Disable LuauNonReentrantGeneralization for some tests (#1775)

For now, this flag causes a stack overflow for some tests on
Windows: we end up minting a massive recursive intersection during
generalization. Let's flip it off until a fix arrives.

Analysis/include/Luau/AnyTypeSummary.h

@@ -1,148 +0,0 @@
-// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-#pragma once
-
-#include "Luau/AstQuery.h"
-#include "Luau/Config.h"
-#include "Luau/ModuleResolver.h"
-#include "Luau/Scope.h"
-#include "Luau/Variant.h"
-#include "Luau/Normalize.h"
-#include "Luau/TypePack.h"
-#include "Luau/TypeArena.h"
-
-#include <mutex>
-#include <string>
-#include <vector>
-#include <optional>
-
-namespace Luau
-{
-
-class AstStat;
-class ParseError;
-struct TypeError;
-struct LintWarning;
-struct GlobalTypes;
-struct ModuleResolver;
-struct ParseResult;
-struct DcrLogger;
-
-struct TelemetryTypePair
-{
-    std::string annotatedType;
-    std::string inferredType;
-};
-
-struct AnyTypeSummary
-{
-    TypeArena arena;
-
-    AstStatBlock* rootSrc = nullptr;
-    DenseHashSet<TypeId> seenTypeFamilyInstances{nullptr};
-
-    int recursionCount = 0;
-
-    std::string root;
-    int strictCount = 0;
-
-    DenseHashMap<const void*, bool> seen{nullptr};
-
-    AnyTypeSummary();
-
-    void traverse(const Module* module, AstStat* src, NotNull<BuiltinTypes> builtinTypes);
-
-    std::pair<bool, TypeId> checkForAnyCast(const Scope* scope, AstExprTypeAssertion* expr);
-
-    bool containsAny(TypePackId typ);
-    bool containsAny(TypeId typ);
-
-    bool isAnyCast(const Scope* scope, AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    bool isAnyCall(const Scope* scope, AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-
-    bool hasVariadicAnys(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    bool hasArgAnys(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    bool hasAnyReturns(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-
-    TypeId checkForFamilyInhabitance(const TypeId instance, Location location);
-    TypeId lookupType(const AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    TypePackId reconstructTypePack(const AstArray<AstExpr*> exprs, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-
-    DenseHashSet<TypeId> seenTypeFunctionInstances{nullptr};
-    TypeId lookupAnnotation(AstType* annotation, const Module* module, NotNull<BuiltinTypes> builtintypes);
-    std::optional<TypePackId> lookupPackAnnotation(AstTypePack* annotation, const Module* module);
-    TypeId checkForTypeFunctionInhabitance(const TypeId instance, const Location location);
-
-    enum Pattern : uint64_t
-    {
-        Casts,
-        FuncArg,
-        FuncRet,
-        FuncApp,
-        VarAnnot,
-        VarAny,
-        TableProp,
-        Alias,
-        Assign,
-        TypePk
-    };
-
-    struct TypeInfo
-    {
-        Pattern code;
-        std::string node;
-        TelemetryTypePair type;
-
-        explicit TypeInfo(Pattern code, std::string node, TelemetryTypePair type);
-    };
-
-    struct FindReturnAncestry final : public AstVisitor
-    {
-        AstNode* currNode{nullptr};
-        AstNode* stat{nullptr};
-        Position rootEnd;
-        bool found = false;
-
-        explicit FindReturnAncestry(AstNode* stat, Position rootEnd);
-
-        bool visit(AstType* node) override;
-        bool visit(AstNode* node) override;
-        bool visit(AstStatFunction* node) override;
-        bool visit(AstStatLocalFunction* node) override;
-    };
-
-    std::vector<TypeInfo> typeInfo;
-
-    /**
-     * Fabricates a scope that is a child of another scope.
-     * @param node the lexical node that the scope belongs to.
-     * @param parent the parent scope of the new scope. Must not be null.
-     */
-    const Scope* childScope(const AstNode* node, const Scope* parent);
-
-    std::optional<AstExpr*> matchRequire(const AstExprCall& call);
-    AstNode* getNode(AstStatBlock* root, AstNode* node);
-    const Scope* findInnerMostScope(const Location location, const Module* module);
-    const AstNode* findAstAncestryAtLocation(const AstStatBlock* root, AstNode* node);
-
-    void visit(const Scope* scope, AstStat* stat, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatBlock* block, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatIf* ifStatement, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatWhile* while_, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatRepeat* repeat, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatReturn* ret, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatLocal* local, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatFor* for_, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatForIn* forIn, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatAssign* assign, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatCompoundAssign* assign, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatFunction* function, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatLocalFunction* function, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatTypeAlias* alias, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatDeclareGlobal* declareGlobal, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatDeclareClass* declareClass, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatDeclareFunction* declareFunction, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-    void visit(const Scope* scope, AstStatError* error, const Module* module, NotNull<BuiltinTypes> builtinTypes);
-};
-
-} // namespace Luau

Analysis/include/Luau/BuiltinDefinitions.h

@@ -70,6 +70,7 @@ Property makeProperty(TypeId ty, std::optional<std::string> documentationSymbol
 void assignPropDocumentationSymbols(TableType::Props& props, const std::string& baseName);
 
 std::string getBuiltinDefinitionSource();
+std::string getTypeFunctionDefinitionSource();
 
 void addGlobalBinding(GlobalTypes& globals, const std::string& name, TypeId ty, const std::string& packageName);
 void addGlobalBinding(GlobalTypes& globals, const std::string& name, Binding binding);

Analysis/include/Luau/Clone.h

@@ -40,4 +40,9 @@ TypeId clone(TypeId tp, TypeArena& dest, CloneState& cloneState);
 TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState);
 Binding clone(const Binding& binding, TypeArena& dest, CloneState& cloneState);
 
+TypePackId cloneIncremental(TypePackId tp, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes);
+TypeId cloneIncremental(TypeId typeId, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes);
+TypeFun cloneIncremental(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes);
+Binding cloneIncremental(const Binding& binding, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes);
+
 } // namespace Luau

Analysis/include/Luau/Constraint.h

@@ -50,6 +50,7 @@ struct GeneralizationConstraint
     TypeId sourceType;
 
     std::vector<TypeId> interiorTypes;
+    bool hasDeprecatedAttribute = false;
 };
 
 // variables ~ iterate iterator

Analysis/include/Luau/ConstraintGenerator.h

@@ -11,15 +11,14 @@
 #include "Luau/ModuleResolver.h"
 #include "Luau/Normalize.h"
 #include "Luau/NotNull.h"
+#include "Luau/Polarity.h"
 #include "Luau/Refinement.h"
 #include "Luau/Symbol.h"
 #include "Luau/TypeFwd.h"
 #include "Luau/TypeUtils.h"
-#include "Luau/Variant.h"
 
 #include <memory>
 #include <vector>
-#include <unordered_map>
 
 namespace Luau
 {
@@ -117,18 +116,23 @@ struct ConstraintGenerator
 
     // Needed to register all available type functions for execution at later stages.
     NotNull<TypeFunctionRuntime> typeFunctionRuntime;
+    DenseHashMap<const AstStatTypeFunction*, ScopePtr> astTypeFunctionEnvironmentScopes{nullptr};
+
     // Needed to resolve modules to make 'require' import types properly.
     NotNull<ModuleResolver> moduleResolver;
     // Occasionally constraint generation needs to produce an ICE.
     const NotNull<InternalErrorReporter> ice;
 
     ScopePtr globalScope;
+    ScopePtr typeFunctionScope;
 
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope;
     std::vector<RequireCycle> requireCycles;
 
     DenseHashMap<TypeId, TypeIds> localTypes{nullptr};
 
+    DenseHashMap<AstExpr*, Inference> inferredExprCache{nullptr};
+
     DcrLogger* logger;
 
     ConstraintGenerator(
@@ -140,6 +144,7 @@ struct ConstraintGenerator
         NotNull<BuiltinTypes> builtinTypes,
         NotNull<InternalErrorReporter> ice,
         const ScopePtr& globalScope,
+        const ScopePtr& typeFunctionScope,
         std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
         DcrLogger* logger,
         NotNull<DataFlowGraph> dfg,
@@ -156,19 +161,26 @@ struct ConstraintGenerator
     void visitFragmentRoot(const ScopePtr& resumeScope, AstStatBlock* block);
 
 private:
-    std::vector<std::vector<TypeId>> interiorTypes;
+    struct InteriorFreeTypes
+    {
+        std::vector<TypeId> types;
+        std::vector<TypePackId> typePacks;
+    };
+
+    std::vector<std::vector<TypeId>> DEPRECATED_interiorTypes;
+    std::vector<InteriorFreeTypes> interiorFreeTypes;
 
     /**
      * Fabricates a new free type belonging to a given scope.
      * @param scope the scope the free type belongs to.
      */
-    TypeId freshType(const ScopePtr& scope);
+    TypeId freshType(const ScopePtr& scope, Polarity polarity = Polarity::Unknown);
 
     /**
      * Fabricates a new free type pack belonging to a given scope.
      * @param scope the scope the free type pack belongs to.
      */
-    TypePackId freshTypePack(const ScopePtr& scope);
+    TypePackId freshTypePack(const ScopePtr& scope, Polarity polarity = Polarity::Unknown);
 
     /**
      * Allocate a new TypePack with the given head and tail.
@@ -289,7 +301,7 @@ private:
     );
 
     Inference check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType, bool forceSingleton);
-    Inference check(const ScopePtr& scope, AstExprConstantBool* bool_, std::optional<TypeId> expectedType, bool forceSingleton);
+    Inference check(const ScopePtr& scope, AstExprConstantBool* boolExpr, std::optional<TypeId> expectedType, bool forceSingleton);
     Inference check(const ScopePtr& scope, AstExprLocal* local);
     Inference check(const ScopePtr& scope, AstExprGlobal* global);
     Inference checkIndexName(const ScopePtr& scope, const RefinementKey* key, AstExpr* indexee, const std::string& index, Location indexLocation);
@@ -365,6 +377,11 @@ private:
      **/
     TypeId resolveType(const ScopePtr& scope, AstType* ty, bool inTypeArguments, bool replaceErrorWithFresh = false);
 
+    // resolveType() is recursive, but we only want to invoke
+    // inferGenericPolarities() once at the very end.  We thus isolate the
+    // recursive part of the algorithm to this internal helper.
+    TypeId resolveType_(const ScopePtr& scope, AstType* ty, bool inTypeArguments, bool replaceErrorWithFresh = false);
+
     /**
      * Resolves a type pack from its AST annotation.
      * @param scope the scope that the type annotation appears within.
@@ -374,6 +391,9 @@ private:
      **/
     TypePackId resolveTypePack(const ScopePtr& scope, AstTypePack* tp, bool inTypeArguments, bool replaceErrorWithFresh = false);
 
+    // Inner hepler for resolveTypePack
+    TypePackId resolveTypePack_(const ScopePtr& scope, AstTypePack* tp, bool inTypeArguments, bool replaceErrorWithFresh = false);
+
     /**
      * Resolves a type pack from its AST annotation.
      * @param scope the scope that the type annotation appears within.
@@ -412,7 +432,7 @@ private:
      **/
     std::vector<std::pair<Name, GenericTypePackDefinition>> createGenericPacks(
         const ScopePtr& scope,
-        AstArray<AstGenericTypePack*> packs,
+        AstArray<AstGenericTypePack*> generics,
         bool useCache = false,
         bool addTypes = true
     );

Analysis/include/Luau/ConstraintSolver.h

@@ -365,7 +365,7 @@ public:
      * @returns a non-free type that generalizes the argument, or `std::nullopt` if one
      * does not exist
      */
-    std::optional<TypeId> generalizeFreeType(NotNull<Scope> scope, TypeId type, bool avoidSealingTables = false);
+    std::optional<TypeId> generalizeFreeType(NotNull<Scope> scope, TypeId type);
 
     /**
      * Checks the existing set of constraints to see if there exist any that contain

Analysis/include/Luau/DataFlowGraph.h

@@ -38,8 +38,6 @@ struct DataFlowGraph
     DefId getDef(const AstExpr* expr) const;
     // Look up the definition optionally, knowing it may not be present.
     std::optional<DefId> getDefOptional(const AstExpr* expr) const;
-    // Look up for the rvalue def for a compound assignment.
-    std::optional<DefId> getRValueDefForCompoundAssign(const AstExpr* expr) const;
 
     DefId getDef(const AstLocal* local) const;
 
@@ -66,10 +64,6 @@ private:
     // All keys in this maps are really only statements that ambiently declares a symbol.
     DenseHashMap<const AstStat*, const Def*> declaredDefs{nullptr};
 
-    // Compound assignments are in a weird situation where the local being assigned to is also being used at its
-    // previous type implicitly in an rvalue position. This map provides the previous binding.
-    DenseHashMap<const AstExpr*, const Def*> compoundAssignDefs{nullptr};
-
     DenseHashMap<const AstExpr*, const RefinementKey*> astRefinementKeys{nullptr};
     friend struct DataFlowGraphBuilder;
 };
@@ -135,8 +129,8 @@ private:
 
     /// A stack of scopes used by the visitor to see where we are.
     ScopeStack scopeStack;
-
+    NotNull<DfgScope> currentScope();
-    DfgScope* currentScope();
+    DfgScope* currentScope_DEPRECATED();
 
     struct FunctionCapture
     {
@@ -154,8 +148,8 @@ private:
     void joinBindings(DfgScope* p, const DfgScope& a, const DfgScope& b);
     void joinProps(DfgScope* p, const DfgScope& a, const DfgScope& b);
 
-    DefId lookup(Symbol symbol);
+    DefId lookup(Symbol symbol, Location location);
-    DefId lookup(DefId def, const std::string& key);
+    DefId lookup(DefId def, const std::string& key, Location location);
 
     ControlFlow visit(AstStatBlock* b);
     ControlFlow visitBlockWithoutChildScope(AstStatBlock* b);

Analysis/include/Luau/Def.h

@@ -4,7 +4,8 @@
 #include "Luau/NotNull.h"
 #include "Luau/TypedAllocator.h"
 #include "Luau/Variant.h"
-
+#include "Luau/Location.h"
+#include "Luau/Symbol.h"
 #include <string>
 #include <optional>
 
@@ -13,6 +14,7 @@ namespace Luau
 
 struct Def;
 using DefId = NotNull<const Def>;
+struct AstLocal;
 
 /**
  * A cell is a "single-object" value.
@@ -64,6 +66,8 @@ struct Def
     using V = Variant<struct Cell, struct Phi>;
 
     V v;
+    Symbol name;
+    Location location;
 };
 
 template<typename T>
@@ -79,7 +83,7 @@ struct DefArena
 {
     TypedAllocator<Def> allocator;
 
-    DefId freshCell(bool subscripted = false);
+    DefId freshCell(Symbol sym, Location location, bool subscripted = false);
     DefId phi(DefId a, DefId b);
     DefId phi(const std::vector<DefId>& defs);
 };

Analysis/include/Luau/FileResolver.h

@@ -1,8 +1,9 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
-#include <string>
+#include <memory>
 #include <optional>
+#include <string>
 #include <vector>
 
 namespace Luau
@@ -32,15 +33,71 @@ struct ModuleInfo
     bool optional = false;
 };
 
+struct RequireAlias
+{
+    std::string alias; // Unprefixed alias name (no leading `@`).
+    std::vector<std::string> tags = {};
+};
+
+struct RequireNode
+{
+    virtual ~RequireNode() {}
+
+    // Get the path component representing this node.
+    virtual std::string getPathComponent() const = 0;
+
+    // Get the displayed user-facing label for this node, defaults to getPathComponent()
+    virtual std::string getLabel() const
+    {
+        return getPathComponent();
+    }
+
+    // Get tags to attach to this node's RequireSuggestion (defaults to none).
+    virtual std::vector<std::string> getTags() const
+    {
+        return {};
+    }
+
+    // TODO: resolvePathToNode() can ultimately be replaced with a call into
+    // require-by-string's path resolution algorithm. This will first require
+    // generalizing that algorithm to work with a virtual file system.
+    virtual std::unique_ptr<RequireNode> resolvePathToNode(const std::string& path) const = 0;
+
+    // Get children of this node, if any (if this node represents a directory).
+    virtual std::vector<std::unique_ptr<RequireNode>> getChildren() const = 0;
+
+    // A list of the aliases available to this node.
+    virtual std::vector<RequireAlias> getAvailableAliases() const = 0;
+};
+
 struct RequireSuggestion
 {
     std::string label;
     std::string fullPath;
+    std::vector<std::string> tags;
 };
 using RequireSuggestions = std::vector<RequireSuggestion>;
 
+struct RequireSuggester
+{
+    virtual ~RequireSuggester() {}
+    std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const;
+
+protected:
+    virtual std::unique_ptr<RequireNode> getNode(const ModuleName& name) const = 0;
+
+private:
+    std::optional<RequireSuggestions> getRequireSuggestionsImpl(const ModuleName& requirer, const std::optional<std::string>& path) const;
+};
+
 struct FileResolver
 {
+    FileResolver() = default;
+    FileResolver(std::shared_ptr<RequireSuggester> requireSuggester)
+        : requireSuggester(std::move(requireSuggester))
+    {
+    }
+
     virtual ~FileResolver() {}
 
     virtual std::optional<SourceCode> readSource(const ModuleName& name) = 0;
@@ -60,10 +117,10 @@ struct FileResolver
         return std::nullopt;
     }
 
-    virtual std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const
+    // Make non-virtual when removing FFlagLuauImproveRequireByStringAutocomplete.
-    {
+    virtual std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const;
-        return std::nullopt;
+
-    }
+    std::shared_ptr<RequireSuggester> requireSuggester;
 };
 
 struct NullFileResolver : FileResolver

Analysis/include/Luau/FragmentAutocomplete.h

@@ -15,6 +15,28 @@ namespace Luau
 {
 struct FrontendOptions;
 
+enum class FragmentAutocompleteWaypoint
+{
+    ParseFragmentEnd,
+    CloneModuleStart,
+    CloneModuleEnd,
+    DfgBuildEnd,
+    CloneAndSquashScopeStart,
+    CloneAndSquashScopeEnd,
+    ConstraintSolverStart,
+    ConstraintSolverEnd,
+    TypecheckFragmentEnd,
+    AutocompleteEnd,
+    COUNT,
+};
+
+class IFragmentAutocompleteReporter
+{
+public:
+    virtual void reportWaypoint(FragmentAutocompleteWaypoint) = 0;
+    virtual void reportFragmentString(std::string_view) = 0;
+};
+
 enum class FragmentTypeCheckStatus
 {
     SkipAutocomplete,
@@ -27,6 +49,8 @@ struct FragmentAutocompleteAncestryResult
     std::vector<AstLocal*> localStack;
     std::vector<AstNode*> ancestry;
     AstStat* nearestStatement = nullptr;
+    AstStatBlock* parentBlock = nullptr;
+    Location fragmentSelectionRegion;
 };
 
 struct FragmentParseResult
@@ -37,6 +61,7 @@ struct FragmentParseResult
     AstStat* nearestStatement = nullptr;
     std::vector<Comment> commentLocations;
     std::unique_ptr<Allocator> alloc = std::make_unique<Allocator>();
+    Position scopePos{0, 0};
 };
 
 struct FragmentTypeCheckResult
@@ -50,14 +75,34 @@ struct FragmentAutocompleteResult
 {
     ModulePtr incrementalModule;
     Scope* freshScope;
-    TypeArena arenaForAutocomplete;
+    TypeArena arenaForAutocomplete_DEPRECATED;
     AutocompleteResult acResults;
 };
 
-FragmentAutocompleteAncestryResult findAncestryForFragmentParse(AstStatBlock* root, const Position& cursorPos);
+struct FragmentRegion
+{
+    Location fragmentLocation;
+    AstStat* nearestStatement = nullptr; // used for tests
+    AstStatBlock* parentBlock = nullptr; // used for scope detection
+};
+
+std::optional<Position> blockDiffStart(AstStatBlock* blockOld, AstStatBlock* blockNew, AstStat* nearestStatementNewAst);
+FragmentRegion getFragmentRegion(AstStatBlock* root, const Position& cursorPosition);
+FragmentAutocompleteAncestryResult findAncestryForFragmentParse(AstStatBlock* stale, const Position& cursorPos, AstStatBlock* lastGoodParse);
+FragmentAutocompleteAncestryResult findAncestryForFragmentParse_DEPRECATED(AstStatBlock* root, const Position& cursorPos);
+
+std::optional<FragmentParseResult> parseFragment_DEPRECATED(
+    AstStatBlock* root,
+    AstNameTable* names,
+    std::string_view src,
+    const Position& cursorPos,
+    std::optional<Position> fragmentEndPosition
+);
 
 std::optional<FragmentParseResult> parseFragment(
-    const SourceModule& srcModule,
+    AstStatBlock* stale,
+    AstStatBlock* mostRecentParse,
+    AstNameTable* names,
     std::string_view src,
     const Position& cursorPos,
     std::optional<Position> fragmentEndPosition
@@ -69,7 +114,9 @@ std::pair<FragmentTypeCheckStatus, FragmentTypeCheckResult> typecheckFragment(
     const Position& cursorPos,
     std::optional<FrontendOptions> opts,
     std::string_view src,
-    std::optional<Position> fragmentEndPosition
+    std::optional<Position> fragmentEndPosition,
+    AstStatBlock* recentParse = nullptr,
+    IFragmentAutocompleteReporter* reporter = nullptr
 );
 
 FragmentAutocompleteResult fragmentAutocomplete(
@@ -79,7 +126,9 @@ FragmentAutocompleteResult fragmentAutocomplete(
     Position cursorPosition,
     std::optional<FrontendOptions> opts,
     StringCompletionCallback callback,
-    std::optional<Position> fragmentEndPosition = std::nullopt
+    std::optional<Position> fragmentEndPosition = std::nullopt,
+    AstStatBlock* recentParse = nullptr,
+    IFragmentAutocompleteReporter* reporter = nullptr
 );
 
 enum class FragmentAutocompleteStatus
@@ -98,9 +147,10 @@ struct FragmentAutocompleteStatusResult
 struct FragmentContext
 {
     std::string_view newSrc;
-    const ParseResult& newAstRoot;
+    const ParseResult& freshParse;
     std::optional<FrontendOptions> opts;
     std::optional<Position> DEPRECATED_fragmentEndPosition;
+    IFragmentAutocompleteReporter* reporter = nullptr;
 };
 
 /**

Analysis/include/Luau/Frontend.h

@@ -10,7 +10,6 @@
 #include "Luau/Set.h"
 #include "Luau/TypeCheckLimits.h"
 #include "Luau/Variant.h"
-#include "Luau/AnyTypeSummary.h"
 
 #include <mutex>
 #include <string>
@@ -32,8 +31,8 @@ struct ModuleResolver;
 struct ParseResult;
 struct HotComment;
 struct BuildQueueItem;
+struct BuildQueueWorkState;
 struct FrontendCancellationToken;
-struct AnyTypeSummary;
 
 struct LoadDefinitionFileResult
 {
@@ -251,6 +250,9 @@ private:
     void checkBuildQueueItem(BuildQueueItem& item);
     void checkBuildQueueItems(std::vector<BuildQueueItem>& items);
     void recordItemResult(const BuildQueueItem& item);
+    void performQueueItemTask(std::shared_ptr<BuildQueueWorkState> state, size_t itemPos);
+    void sendQueueItemTask(std::shared_ptr<BuildQueueWorkState> state, size_t itemPos);
+    void sendQueueCycleItemTask(std::shared_ptr<BuildQueueWorkState> state);
 
     static LintResult classifyLints(const std::vector<LintWarning>& warnings, const Config& config);
 
@@ -296,6 +298,7 @@ ModulePtr check(
     NotNull<ModuleResolver> moduleResolver,
     NotNull<FileResolver> fileResolver,
     const ScopePtr& globalScope,
+    const ScopePtr& typeFunctionScope,
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
     FrontendOptions options,
     TypeCheckLimits limits
@@ -310,6 +313,7 @@ ModulePtr check(
     NotNull<ModuleResolver> moduleResolver,
     NotNull<FileResolver> fileResolver,
     const ScopePtr& globalScope,
+    const ScopePtr& typeFunctionScope,
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
     FrontendOptions options,
     TypeCheckLimits limits,

Analysis/include/Luau/Generalization.h

@@ -8,12 +8,39 @@
 namespace Luau
 {
 
+template<typename TID>
+struct GeneralizationParams
+{
+    bool foundOutsideFunctions = false;
+    size_t useCount = 0;
+    Polarity polarity = Polarity::None;
+};
+
+// Replace a single free type by its bounds according to the polarity provided.
+std::optional<TypeId> generalizeType(
+    NotNull<TypeArena> arena,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Scope> scope,
+    TypeId freeTy,
+    const GeneralizationParams<TypeId>& params
+);
+
+// Generalize one type pack
+std::optional<TypePackId> generalizeTypePack(
+    NotNull<TypeArena> arena,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Scope> scope,
+    TypePackId tp,
+    const GeneralizationParams<TypePackId>& params
+);
+
+void sealTable(NotNull<Scope> scope, TypeId ty);
+
 std::optional<TypeId> generalize(
     NotNull<TypeArena> arena,
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<Scope> scope,
-    NotNull<DenseHashSet<TypeId>> bakedTypes,
+    NotNull<DenseHashSet<TypeId>> cachedTypes,
-    TypeId ty,
+    TypeId ty
-    /* avoid sealing tables*/ bool avoidSealingTables = false
 );
 }

Analysis/include/Luau/GlobalTypes.h

@@ -19,7 +19,9 @@ struct GlobalTypes
 
     TypeArena globalTypes;
     SourceModule globalNames; // names for symbols entered into globalScope
+
     ScopePtr globalScope;     // shared by all modules
+    ScopePtr globalTypeFunctionScope; // shared by all modules
 };
 
 } // namespace Luau

Analysis/include/Luau/InferPolarity.h

@@ -0,0 +1,16 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/NotNull.h"
+#include "Luau/TypeFwd.h"
+
+namespace Luau
+{
+
+struct Scope;
+struct TypeArena;
+
+void inferGenericPolarities(NotNull<TypeArena> arena, NotNull<Scope> scope, TypeId ty);
+void inferGenericPolarities(NotNull<TypeArena> arena, NotNull<Scope> scope, TypePackId tp);
+
+} // namespace Luau

Analysis/include/Luau/InsertionOrderedMap.h

@@ -67,6 +67,19 @@ public:
             return &pairs.at(it->second).second;
     }
 
+    V& operator[](const K& k)
+    {
+        auto it = indices.find(k);
+        if (it == indices.end())
+        {
+            pairs.push_back(std::make_pair(k, V()));
+            indices[k] = pairs.size() - 1;
+            return pairs.back().second;
+        }
+        else
+            return pairs.at(it->second).second;
+    }
+
     const_iterator begin() const
     {
         return pairs.begin();

Analysis/include/Luau/Module.h

@@ -8,7 +8,6 @@
 #include "Luau/ParseResult.h"
 #include "Luau/Scope.h"
 #include "Luau/TypeArena.h"
-#include "Luau/AnyTypeSummary.h"
 #include "Luau/DataFlowGraph.h"
 
 #include <memory>
@@ -16,19 +15,16 @@
 #include <unordered_map>
 #include <optional>
 
-LUAU_FASTFLAG(LuauIncrementalAutocompleteCommentDetection)
-
 namespace Luau
 {
 
-using LogLuauProc = void (*)(std::string_view);
+using LogLuauProc = void (*)(std::string_view, std::string_view);
 extern LogLuauProc logLuau;
 
 void setLogLuau(LogLuauProc ll);
 void resetLogLuauProc();
 
 struct Module;
-struct AnyTypeSummary;
 
 using ScopePtr = std::shared_ptr<struct Scope>;
 using ModulePtr = std::shared_ptr<Module>;
@@ -86,13 +82,10 @@ struct Module
     TypeArena interfaceTypes;
     TypeArena internalTypes;
 
-    // Summary of Ast Nodes that either contain
-    // user annotated anys or typechecker inferred anys
-    AnyTypeSummary ats{};
-
     // Scopes and AST types refer to parse data, so we need to keep that alive
     std::shared_ptr<Allocator> allocator;
     std::shared_ptr<AstNameTable> names;
+    AstStatBlock* root = nullptr;
 
     std::vector<std::pair<Location, ScopePtr>> scopes; // never empty
 

Analysis/include/Luau/NonStrictTypeChecker.h

@@ -1,9 +1,10 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/DataFlowGraph.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/Module.h"
 #include "Luau/NotNull.h"
-#include "Luau/DataFlowGraph.h"
 
 namespace Luau
 {

Analysis/include/Luau/Polarity.h

@@ -0,0 +1,68 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include <cstdint>
+
+namespace Luau
+{
+
+enum struct Polarity : uint8_t
+{
+    None = 0b000,
+    Positive = 0b001,
+    Negative = 0b010,
+    Mixed = 0b011,
+    Unknown = 0b100,
+};
+
+inline Polarity operator|(Polarity lhs, Polarity rhs)
+{
+    return Polarity(uint8_t(lhs) | uint8_t(rhs));
+}
+
+inline Polarity& operator|=(Polarity& lhs, Polarity rhs)
+{
+    lhs = lhs | rhs;
+    return lhs;
+}
+
+inline Polarity operator&(Polarity lhs, Polarity rhs)
+{
+    return Polarity(uint8_t(lhs) & uint8_t(rhs));
+}
+
+inline Polarity& operator&=(Polarity& lhs, Polarity rhs)
+{
+    lhs = lhs & rhs;
+    return lhs;
+}
+
+inline bool isPositive(Polarity p)
+{
+    return bool(p & Polarity::Positive);
+}
+
+inline bool isNegative(Polarity p)
+{
+    return bool(p & Polarity::Negative);
+}
+
+inline bool isKnown(Polarity p)
+{
+    return p != Polarity::Unknown;
+}
+
+inline Polarity invert(Polarity p)
+{
+    switch (p)
+    {
+    case Polarity::Positive:
+        return Polarity::Negative;
+    case Polarity::Negative:
+        return Polarity::Positive;
+    default:
+        return p;
+    }
+}
+
+} // namespace Luau

Analysis/include/Luau/Quantify.h

@@ -31,13 +31,4 @@ struct OrderedMap
     }
 };
 
-struct QuantifierResult
-{
-    TypeId result;
-    OrderedMap<TypeId, TypeId> insertedGenerics;
-    OrderedMap<TypePackId, TypePackId> insertedGenericPacks;
-};
-
-std::optional<QuantifierResult> quantify(TypeArena* arena, TypeId ty, Scope* scope);
-
 } // namespace Luau

Analysis/include/Luau/Refinement.h

@@ -53,6 +53,7 @@ struct Proposition
 {
     const RefinementKey* key;
     TypeId discriminantTy;
+    bool implicitFromCall;
 };
 
 template<typename T>
@@ -69,6 +70,7 @@ struct RefinementArena
     RefinementId disjunction(RefinementId lhs, RefinementId rhs);
     RefinementId equivalence(RefinementId lhs, RefinementId rhs);
     RefinementId proposition(const RefinementKey* key, TypeId discriminantTy);
+    RefinementId implicitProposition(const RefinementKey* key, TypeId discriminantTy);
 
 private:
     TypedAllocator<Refinement> allocator;

Analysis/include/Luau/Scope.h

@@ -35,12 +35,12 @@ struct Scope
     explicit Scope(TypePackId returnType);                    // root scope
     explicit Scope(const ScopePtr& parent, int subLevel = 0); // child scope.  Parent must not be nullptr.
 
-    const ScopePtr parent; // null for the root
+    ScopePtr parent; // null for the root
 
     // All the children of this scope.
     std::vector<NotNull<Scope>> children;
     std::unordered_map<Symbol, Binding> bindings;
-    TypePackId returnType;
+    TypePackId returnType = nullptr;
     std::optional<TypePackId> varargPack;
 
     TypeLevel level;
@@ -59,6 +59,8 @@ struct Scope
 
     std::optional<TypeId> lookup(Symbol sym) const;
     std::optional<TypeId> lookupUnrefinedType(DefId def) const;
+
+    std::optional<TypeId> lookupRValueRefinementType(DefId def) const;
     std::optional<TypeId> lookup(DefId def) const;
     std::optional<std::pair<TypeId, Scope*>> lookupEx(DefId def);
     std::optional<std::pair<Binding*, Scope*>> lookupEx(Symbol sym);
@@ -71,6 +73,7 @@ struct Scope
 
     // WARNING: This function linearly scans for a string key of equal value!  It is thus O(n**2)
     std::optional<Binding> linearSearchForBinding(const std::string& name, bool traverseScopeChain = true) const;
+    std::optional<std::pair<Symbol, Binding>> linearSearchForBindingPair(const std::string& name, bool traverseScopeChain) const;
 
     RefinementMap refinements;
 
@@ -97,6 +100,7 @@ struct Scope
     std::unordered_map<Name, TypePackId> typeAliasTypePackParameters;
 
     std::optional<std::vector<TypeId>> interiorFreeTypes;
+    std::optional<std::vector<TypePackId>> interiorFreeTypePacks;
 };
 
 // Returns true iff the left scope encloses the right scope.  A Scope* equal to

Analysis/include/Luau/TableLiteralInference.h

@@ -14,6 +14,7 @@ namespace Luau
 struct TypeArena;
 struct BuiltinTypes;
 struct Unifier2;
+struct Subtyping;
 class AstExpr;
 
 TypeId matchLiteralType(
@@ -22,6 +23,7 @@ TypeId matchLiteralType(
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<TypeArena> arena,
     NotNull<Unifier2> unifier,
+    NotNull<Subtyping> subtyping,
     TypeId expectedType,
     TypeId exprType,
     const AstExpr* expr,

Analysis/include/Luau/TxnLog.h

@@ -192,16 +192,6 @@ struct TxnLog
     // The pointer returned lives until `commit` or `clear` is called.
     PendingTypePack* changeLevel(TypePackId tp, TypeLevel newLevel);
 
-    // Queues the replacement of a type's scope with the provided scope.
-    //
-    // The pointer returned lives until `commit` or `clear` is called.
-    PendingType* changeScope(TypeId ty, NotNull<Scope> scope);
-
-    // Queues the replacement of a type pack's scope with the provided scope.
-    //
-    // The pointer returned lives until `commit` or `clear` is called.
-    PendingTypePack* changeScope(TypePackId tp, NotNull<Scope> scope);
-
     // Queues a replacement of a table type with another table type with a new
     // indexer.
     //

Analysis/include/Luau/Type.h

@@ -5,10 +5,11 @@
 
 #include "Luau/Ast.h"
 #include "Luau/Common.h"
-#include "Luau/Refinement.h"
 #include "Luau/DenseHash.h"
 #include "Luau/NotNull.h"
+#include "Luau/Polarity.h"
 #include "Luau/Predicate.h"
+#include "Luau/Refinement.h"
 #include "Luau/Unifiable.h"
 #include "Luau/Variant.h"
 #include "Luau/VecDeque.h"
@@ -19,7 +20,6 @@
 #include <optional>
 #include <set>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 LUAU_FASTINT(LuauTableTypeMaximumStringifierLength)
@@ -72,7 +72,7 @@ struct FreeType
     // New constructors
     explicit FreeType(TypeLevel level, TypeId lowerBound, TypeId upperBound);
     // This one got promoted to explicit
-    explicit FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound);
+    explicit FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound, Polarity polarity = Polarity::Unknown);
     explicit FreeType(Scope* scope, TypeLevel level, TypeId lowerBound, TypeId upperBound);
     // Old constructors
     explicit FreeType(TypeLevel level);
@@ -91,6 +91,8 @@ struct FreeType
     // Only used under local type inference
     TypeId lowerBound = nullptr;
     TypeId upperBound = nullptr;
+
+    Polarity polarity = Polarity::Unknown;
 };
 
 struct GenericType
@@ -99,8 +101,8 @@ struct GenericType
     GenericType();
 
     explicit GenericType(TypeLevel level);
-    explicit GenericType(const Name& name);
+    explicit GenericType(const Name& name, Polarity polarity = Polarity::Unknown);
-    explicit GenericType(Scope* scope);
+    explicit GenericType(Scope* scope, Polarity polarity = Polarity::Unknown);
 
     GenericType(TypeLevel level, const Name& name);
     GenericType(Scope* scope, const Name& name);
@@ -110,6 +112,8 @@ struct GenericType
     Scope* scope = nullptr;
     Name name;
     bool explicitName = false;
+
+    Polarity polarity = Polarity::Unknown;
 };
 
 // When an equality constraint is found, it is then "bound" to that type,
@@ -348,10 +352,8 @@ struct FunctionType
     );
 
     // Local monomorphic function
-    FunctionType(TypeLevel level, TypePackId argTypes, TypePackId retTypes, std::optional<FunctionDefinition> defn = {}, bool hasSelf = false);
     FunctionType(
         TypeLevel level,
-        Scope* scope,
         TypePackId argTypes,
         TypePackId retTypes,
         std::optional<FunctionDefinition> defn = {},
@@ -368,16 +370,6 @@ struct FunctionType
         std::optional<FunctionDefinition> defn = {},
         bool hasSelf = false
     );
-    FunctionType(
-        TypeLevel level,
-        Scope* scope,
-        std::vector<TypeId> generics,
-        std::vector<TypePackId> genericPacks,
-        TypePackId argTypes,
-        TypePackId retTypes,
-        std::optional<FunctionDefinition> defn = {},
-        bool hasSelf = false
-    );
 
     std::optional<FunctionDefinition> definition;
     /// These should all be generic
@@ -386,7 +378,6 @@ struct FunctionType
     std::vector<std::optional<FunctionArgument>> argNames;
     Tags tags;
     TypeLevel level;
-    Scope* scope = nullptr;
     TypePackId argTypes;
     TypePackId retTypes;
     std::shared_ptr<MagicFunction> magic = nullptr;
@@ -396,6 +387,7 @@ struct FunctionType
     // this flag is used as an optimization to exit early from procedures that manipulate free or generic types.
     bool hasNoFreeOrGenericTypes = false;
     bool isCheckedFunction = false;
+    bool isDeprecatedFunction = false;
 };
 
 enum class TableState
@@ -472,7 +464,9 @@ struct Property
     TypeId type() const;
     void setType(TypeId ty);
 
-    // Sets the write type of this property to the read type.
+    // If this property has a present `writeTy`, set it equal to the `readTy`.
+    // This is to ensure that if we normalize a property that has divergent
+    // read and write types, we make them converge (for now).
     void makeShared();
 
     bool isShared() const;
@@ -517,9 +511,6 @@ struct TableType
     std::optional<TypeId> boundTo;
     Tags tags;
 
-    // Methods of this table that have an untyped self will use the same shared self type.
-    std::optional<TypeId> selfTy;
-
     // We track the number of as-yet-unadded properties to unsealed tables.
     // Some constraints will use this information to decide whether or not they
     // are able to dispatch.
@@ -622,7 +613,6 @@ struct UserDefinedFunctionData
     AstStatTypeFunction* definition = nullptr;
 
     DenseHashMap<Name, std::pair<AstStatTypeFunction*, size_t>> environment{""};
-    DenseHashMap<Name, AstStatTypeFunction*> environment_DEPRECATED{""};
 };
 
 /**
@@ -882,6 +872,9 @@ struct TypeFun
      */
     TypeId type;
 
+    // The location of where this TypeFun was defined, if available
+    std::optional<Location> definitionLocation;
+
     TypeFun() = default;
 
     explicit TypeFun(TypeId ty)
@@ -889,16 +882,23 @@ struct TypeFun
     {
     }
 
-    TypeFun(std::vector<GenericTypeDefinition> typeParams, TypeId type)
+    TypeFun(std::vector<GenericTypeDefinition> typeParams, TypeId type, std::optional<Location> definitionLocation = std::nullopt)
         : typeParams(std::move(typeParams))
         , type(type)
+        , definitionLocation(definitionLocation)
     {
     }
 
-    TypeFun(std::vector<GenericTypeDefinition> typeParams, std::vector<GenericTypePackDefinition> typePackParams, TypeId type)
+    TypeFun(
+        std::vector<GenericTypeDefinition> typeParams,
+        std::vector<GenericTypePackDefinition> typePackParams,
+        TypeId type,
+        std::optional<Location> definitionLocation = std::nullopt
+    )
         : typeParams(std::move(typeParams))
         , typePackParams(std::move(typePackParams))
         , type(type)
+        , definitionLocation(definitionLocation)
     {
     }
 
@@ -1202,7 +1202,7 @@ private:
     }
 };
 
-TypeId freshType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, Scope* scope);
+TypeId freshType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, Scope* scope, Polarity polarity = Polarity::Unknown);
 
 using TypeIdPredicate = std::function<std::optional<TypeId>(TypeId)>;
 std::vector<TypeId> filterMap(TypeId type, TypeIdPredicate predicate);

Analysis/include/Luau/TypeArena.h

@@ -1,6 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/Polarity.h"
 #include "Luau/TypedAllocator.h"
 #include "Luau/Type.h"
 #include "Luau/TypePack.h"
@@ -40,7 +41,7 @@ struct TypeArena
     TypeId freshType_DEPRECATED(Scope* scope);
     TypeId freshType_DEPRECATED(Scope* scope, TypeLevel level);
 
-    TypePackId freshTypePack(Scope* scope);
+    TypePackId freshTypePack(Scope* scope, Polarity polarity = Polarity::Unknown);
 
     TypePackId addTypePack(std::initializer_list<TypeId> types);
     TypePackId addTypePack(std::vector<TypeId> types, std::optional<TypePackId> tail = {});

Analysis/include/Luau/TypeChecker2.h

@@ -13,6 +13,8 @@
 #include "Luau/TypeOrPack.h"
 #include "Luau/TypeUtils.h"
 
+LUAU_FASTFLAG(LuauImproveTypePathsInErrors)
+
 namespace Luau
 {
 
@@ -38,18 +40,29 @@ struct Reasonings
 
     std::string toString()
     {
+        if (FFlag::LuauImproveTypePathsInErrors && reasons.empty())
+            return "";
+
         // DenseHashSet ordering is entirely undefined, so we want to
         // sort the reasons here to achieve a stable error
         // stringification.
         std::sort(reasons.begin(), reasons.end());
-        std::string allReasons;
+        std::string allReasons = FFlag::LuauImproveTypePathsInErrors ? "\nthis is because " : "";
         bool first = true;
         for (const std::string& reason : reasons)
         {
-            if (first)
+            if (FFlag::LuauImproveTypePathsInErrors)
-                first = false;
+            {
+                if (reasons.size() > 1)
+                    allReasons += "\n\t * ";
+            }
             else
-                allReasons += "\n\t";
+            {
+                if (first)
+                    first = false;
+                else
+                    allReasons += "\n\t";
+            }
 
             allReasons += reason;
         }

Analysis/include/Luau/TypeFunction.h

@@ -48,6 +48,9 @@ struct TypeFunctionRuntime
     // Evaluation of type functions should only be performed in the absence of parse errors in the source module
     bool allowEvaluation = true;
 
+    // Root scope in which the type function operates in, set up by ConstraintGenerator
+    ScopePtr rootScope;
+
     // Output created by 'print' function
     std::vector<std::string> messages;
 
@@ -174,6 +177,7 @@ struct FunctionGraphReductionResult
     DenseHashSet<TypePackId> blockedPacks{nullptr};
     DenseHashSet<TypeId> reducedTypes{nullptr};
     DenseHashSet<TypePackId> reducedPacks{nullptr};
+    DenseHashSet<TypeId> irreducibleTypes{nullptr};
 };
 
 /**
@@ -244,6 +248,8 @@ struct BuiltinTypeFunctions
     TypeFunction setmetatableFunc;
     TypeFunction getmetatableFunc;
 
+    TypeFunction weakoptionalFunc;
+
     void addToScope(NotNull<TypeArena> arena, NotNull<Scope> scope) const;
 };
 

Analysis/include/Luau/TypeFunctionRuntime.h

@@ -223,8 +223,6 @@ struct TypeFunctionClassType
     std::optional<TypeFunctionTypeId> writeParent;
 
     TypeId classTy;
-
-    std::string name_DEPRECATED;
 };
 
 struct TypeFunctionGenericType

Analysis/include/Luau/TypeFunctionRuntimeBuilder.h

@@ -28,14 +28,8 @@ struct TypeFunctionRuntimeBuilderState
 {
     NotNull<TypeFunctionContext> ctx;
 
-    // Mapping of class name to ClassType
-    // Invariant: users can not create a new class types -> any class types that get deserialized must have been an argument to the type function
-    // Using this invariant, whenever a ClassType is serialized, we can put it into this map
-    // whenever a ClassType is deserialized, we can use this map to return the corresponding value
-    DenseHashMap<std::string, TypeId> classesSerialized_DEPRECATED{{}};
-
     // List of errors that occur during serialization/deserialization
-    // At every iteration of serialization/deserialzation, if this list.size() != 0, we halt the process
+    // At every iteration of serialization/deserialization, if this list.size() != 0, we halt the process
     std::vector<std::string> errors{};
 
     TypeFunctionRuntimeBuilderState(NotNull<TypeFunctionContext> ctx)

Analysis/include/Luau/TypePack.h

@@ -1,11 +1,12 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/Common.h"
+#include "Luau/NotNull.h"
+#include "Luau/Polarity.h"
+#include "Luau/TypeFwd.h"
 #include "Luau/Unifiable.h"
 #include "Luau/Variant.h"
-#include "Luau/TypeFwd.h"
-#include "Luau/NotNull.h"
-#include "Luau/Common.h"
 
 #include <optional>
 #include <set>
@@ -26,12 +27,14 @@ struct TypeFunctionInstanceTypePack;
 struct FreeTypePack
 {
     explicit FreeTypePack(TypeLevel level);
-    explicit FreeTypePack(Scope* scope);
+    explicit FreeTypePack(Scope* scope, Polarity polarity = Polarity::Unknown);
     FreeTypePack(Scope* scope, TypeLevel level);
 
     int index;
     TypeLevel level;
     Scope* scope = nullptr;
+
+    Polarity polarity = Polarity::Unknown;
 };
 
 struct GenericTypePack
@@ -40,7 +43,7 @@ struct GenericTypePack
     GenericTypePack();
     explicit GenericTypePack(TypeLevel level);
     explicit GenericTypePack(const Name& name);
-    explicit GenericTypePack(Scope* scope);
+    explicit GenericTypePack(Scope* scope, Polarity polarity = Polarity::Unknown);
     GenericTypePack(TypeLevel level, const Name& name);
     GenericTypePack(Scope* scope, const Name& name);
 
@@ -49,6 +52,8 @@ struct GenericTypePack
     Scope* scope = nullptr;
     Name name;
     bool explicitName = false;
+
+    Polarity polarity = Polarity::Unknown;
 };
 
 using BoundTypePack = Unifiable::Bound<TypePackId>;
@@ -100,9 +105,9 @@ struct TypeFunctionInstanceTypePack
 
 struct TypePackVar
 {
-    explicit TypePackVar(const TypePackVariant& ty);
+    explicit TypePackVar(const TypePackVariant& tp);
-    explicit TypePackVar(TypePackVariant&& ty);
+    explicit TypePackVar(TypePackVariant&& tp);
-    TypePackVar(TypePackVariant&& ty, bool persistent);
+    TypePackVar(TypePackVariant&& tp, bool persistent);
 
     bool operator==(const TypePackVar& rhs) const;
 
@@ -169,6 +174,7 @@ struct TypePackIterator
 
 private:
     TypePackId currentTypePack = nullptr;
+    TypePackId tailCycleCheck = nullptr;
     const TypePack* tp = nullptr;
     size_t currentIndex = 0;
 

Analysis/include/Luau/TypePath.h

@@ -42,9 +42,19 @@ struct Property
 /// element.
 struct Index
 {
+    enum class Variant
+    {
+        Pack,
+        Union,
+        Intersection
+    };
+
     /// The 0-based index to use for the lookup.
     size_t index;
 
+    /// The sort of thing we're indexing from, this is used in stringifying the type path for errors.
+    Variant variant;
+
     bool operator==(const Index& other) const;
 };
 
@@ -205,6 +215,9 @@ using Path = TypePath::Path;
 /// terribly clear to end users of the Luau type system.
 std::string toString(const TypePath::Path& path, bool prefixDot = false);
 
+/// Converts a Path to a human readable string for error reporting.
+std::string toStringHuman(const TypePath::Path& path);
+
 std::optional<TypeOrPack> traverse(TypeId root, const Path& path, NotNull<BuiltinTypes> builtinTypes);
 std::optional<TypeOrPack> traverse(TypePackId root, const Path& path, NotNull<BuiltinTypes> builtinTypes);
 

Analysis/include/Luau/TypeUtils.h

@@ -289,4 +289,6 @@ std::vector<TypeId> findBlockedArgTypesIn(AstExprCall* expr, NotNull<DenseHashMa
  */
 void trackInteriorFreeType(Scope* scope, TypeId ty);
 
+void trackInteriorFreeTypePack(Scope* scope, TypePackId tp);
+
 } // namespace Luau

Analysis/include/Luau/Unifier2.h

@@ -44,6 +44,12 @@ struct Unifier2
     // Mapping from generic type packs to `TypePack`s of free types to be used in instantiation.
     DenseHashMap<TypePackId, TypePackId> genericPackSubstitutions{nullptr};
 
+    // Unification sometimes results in the creation of new free types.
+    // We collect them here so that other systems can perform necessary
+    // bookkeeping.
+    std::vector<TypeId> newFreshTypes;
+    std::vector<TypePackId> newFreshTypePacks;
+
     int recursionCount = 0;
     int recursionLimit = 0;
 
@@ -87,6 +93,9 @@ struct Unifier2
     bool unify(const AnyType* subAny, const TableType* superTable);
     bool unify(const TableType* subTable, const AnyType* superAny);
 
+    bool unify(const MetatableType* subMetatable, const AnyType*);
+    bool unify(const AnyType*, const MetatableType* superMetatable);
+
     // TODO think about this one carefully.  We don't do unions or intersections of type packs
     bool unify(TypePackId subTp, TypePackId superTp);
 
@@ -110,6 +119,9 @@ private:
     // Returns true if needle occurs within haystack already.  ie if we bound
     // needle to haystack, would a cyclic TypePack result?
     OccursCheckResult occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, TypePackId haystack);
+
+    TypeId freshType(NotNull<Scope> scope, Polarity polarity);
+    TypePackId freshTypePack(NotNull<Scope> scope, Polarity polarity);
 };
 
 } // namespace Luau

Analysis/src/AnyTypeSummary.cpp

@@ -1,902 +0,0 @@
-// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-#include "Luau/AnyTypeSummary.h"
-
-#include "Luau/BuiltinDefinitions.h"
-#include "Luau/Clone.h"
-#include "Luau/Common.h"
-#include "Luau/Config.h"
-#include "Luau/ConstraintGenerator.h"
-#include "Luau/ConstraintSolver.h"
-#include "Luau/DataFlowGraph.h"
-#include "Luau/DcrLogger.h"
-#include "Luau/Module.h"
-#include "Luau/Parser.h"
-#include "Luau/Scope.h"
-#include "Luau/StringUtils.h"
-#include "Luau/TimeTrace.h"
-#include "Luau/ToString.h"
-#include "Luau/Transpiler.h"
-#include "Luau/TypeArena.h"
-#include "Luau/TypeChecker2.h"
-#include "Luau/NonStrictTypeChecker.h"
-#include "Luau/TypeInfer.h"
-#include "Luau/Variant.h"
-#include "Luau/VisitType.h"
-#include "Luau/TypePack.h"
-#include "Luau/TypeOrPack.h"
-
-#include <algorithm>
-#include <memory>
-#include <chrono>
-#include <condition_variable>
-#include <exception>
-#include <mutex>
-#include <stdexcept>
-#include <string>
-#include <iostream>
-
-
-#include <stdio.h>
-
-LUAU_FASTFLAGVARIABLE(StudioReportLuauAny2);
-LUAU_FASTINTVARIABLE(LuauAnySummaryRecursionLimit, 300);
-
-LUAU_FASTFLAG(DebugLuauMagicTypes);
-
-namespace Luau
-{
-
-void AnyTypeSummary::traverse(const Module* module, AstStat* src, NotNull<BuiltinTypes> builtinTypes)
-{
-    visit(findInnerMostScope(src->location, module), src, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStat* stat, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    RecursionLimiter limiter{&recursionCount, FInt::LuauAnySummaryRecursionLimit};
-
-    if (auto s = stat->as<AstStatBlock>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto i = stat->as<AstStatIf>())
-        return visit(scope, i, module, builtinTypes);
-    else if (auto s = stat->as<AstStatWhile>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatRepeat>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto r = stat->as<AstStatReturn>())
-        return visit(scope, r, module, builtinTypes);
-    else if (auto e = stat->as<AstStatExpr>())
-        return visit(scope, e, module, builtinTypes);
-    else if (auto s = stat->as<AstStatLocal>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatFor>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatForIn>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto a = stat->as<AstStatAssign>())
-        return visit(scope, a, module, builtinTypes);
-    else if (auto a = stat->as<AstStatCompoundAssign>())
-        return visit(scope, a, module, builtinTypes);
-    else if (auto f = stat->as<AstStatFunction>())
-        return visit(scope, f, module, builtinTypes);
-    else if (auto f = stat->as<AstStatLocalFunction>())
-        return visit(scope, f, module, builtinTypes);
-    else if (auto a = stat->as<AstStatTypeAlias>())
-        return visit(scope, a, module, builtinTypes);
-    else if (auto s = stat->as<AstStatDeclareGlobal>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatDeclareFunction>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatDeclareClass>())
-        return visit(scope, s, module, builtinTypes);
-    else if (auto s = stat->as<AstStatError>())
-        return visit(scope, s, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatBlock* block, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    RecursionCounter counter{&recursionCount};
-
-    if (recursionCount >= FInt::LuauAnySummaryRecursionLimit)
-        return; // don't report
-
-    for (AstStat* stat : block->body)
-        visit(scope, stat, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatIf* ifStatement, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (ifStatement->thenbody)
-    {
-        const Scope* thenScope = findInnerMostScope(ifStatement->thenbody->location, module);
-        visit(thenScope, ifStatement->thenbody, module, builtinTypes);
-    }
-
-    if (ifStatement->elsebody)
-    {
-        const Scope* elseScope = findInnerMostScope(ifStatement->elsebody->location, module);
-        visit(elseScope, ifStatement->elsebody, module, builtinTypes);
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatWhile* while_, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const Scope* whileScope = findInnerMostScope(while_->location, module);
-    visit(whileScope, while_->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatRepeat* repeat, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const Scope* repeatScope = findInnerMostScope(repeat->location, module);
-    visit(repeatScope, repeat->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatReturn* ret, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const Scope* retScope = findInnerMostScope(ret->location, module);
-
-    auto ctxNode = getNode(rootSrc, ret);
-    bool seenTP = false;
-
-    for (auto val : ret->list)
-    {
-        if (isAnyCall(retScope, val, module, builtinTypes))
-        {
-            TelemetryTypePair types;
-            types.inferredType = toString(lookupType(val, module, builtinTypes));
-            TypeInfo ti{Pattern::FuncApp, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-
-        if (isAnyCast(retScope, val, module, builtinTypes))
-        {
-            if (auto cast = val->as<AstExprTypeAssertion>())
-            {
-                TelemetryTypePair types;
-
-                types.annotatedType = toString(lookupAnnotation(cast->annotation, module, builtinTypes));
-                types.inferredType = toString(lookupType(cast->expr, module, builtinTypes));
-
-                TypeInfo ti{Pattern::Casts, toString(ctxNode), types};
-                typeInfo.push_back(ti);
-            }
-        }
-
-        if (ret->list.size > 1 && !seenTP)
-        {
-            if (containsAny(retScope->returnType))
-            {
-                seenTP = true;
-
-                TelemetryTypePair types;
-
-                types.inferredType = toString(retScope->returnType);
-
-                TypeInfo ti{Pattern::TypePk, toString(ctxNode), types};
-                typeInfo.push_back(ti);
-            }
-        }
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatLocal* local, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    auto ctxNode = getNode(rootSrc, local);
-
-    TypePackId values = reconstructTypePack(local->values, module, builtinTypes);
-    auto [head, tail] = flatten(values);
-
-    size_t posn = 0;
-    for (AstLocal* loc : local->vars)
-    {
-        if (local->vars.data[0] == loc && posn < local->values.size)
-        {
-            if (loc->annotation)
-            {
-                auto annot = lookupAnnotation(loc->annotation, module, builtinTypes);
-                if (containsAny(annot))
-                {
-                    TelemetryTypePair types;
-
-                    types.annotatedType = toString(annot);
-                    types.inferredType = toString(lookupType(local->values.data[posn], module, builtinTypes));
-
-                    TypeInfo ti{Pattern::VarAnnot, toString(ctxNode), types};
-                    typeInfo.push_back(ti);
-                }
-            }
-
-            const AstExprTypeAssertion* maybeRequire = local->values.data[posn]->as<AstExprTypeAssertion>();
-            if (!maybeRequire)
-                continue;
-
-            if (std::min(local->values.size - 1, posn) < head.size())
-            {
-                if (isAnyCast(scope, local->values.data[posn], module, builtinTypes))
-                {
-                    TelemetryTypePair types;
-
-                    types.inferredType = toString(head[std::min(local->values.size - 1, posn)]);
-
-                    TypeInfo ti{Pattern::Casts, toString(ctxNode), types};
-                    typeInfo.push_back(ti);
-                }
-            }
-        }
-        else
-        {
-
-            if (std::min(local->values.size - 1, posn) < head.size())
-            {
-                if (loc->annotation)
-                {
-                    auto annot = lookupAnnotation(loc->annotation, module, builtinTypes);
-                    if (containsAny(annot))
-                    {
-                        TelemetryTypePair types;
-
-                        types.annotatedType = toString(annot);
-                        types.inferredType = toString(head[std::min(local->values.size - 1, posn)]);
-
-                        TypeInfo ti{Pattern::VarAnnot, toString(ctxNode), types};
-                        typeInfo.push_back(ti);
-                    }
-                }
-            }
-            else
-            {
-                if (tail)
-                {
-                    if (containsAny(*tail))
-                    {
-                        TelemetryTypePair types;
-
-                        types.inferredType = toString(*tail);
-
-                        TypeInfo ti{Pattern::VarAny, toString(ctxNode), types};
-                        typeInfo.push_back(ti);
-                    }
-                }
-            }
-        }
-
-        ++posn;
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatFor* for_, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const Scope* forScope = findInnerMostScope(for_->location, module);
-    visit(forScope, for_->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatForIn* forIn, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const Scope* loopScope = findInnerMostScope(forIn->location, module);
-    visit(loopScope, forIn->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatAssign* assign, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    auto ctxNode = getNode(rootSrc, assign);
-
-    TypePackId values = reconstructTypePack(assign->values, module, builtinTypes);
-    auto [head, tail] = flatten(values);
-
-    size_t posn = 0;
-    for (AstExpr* var : assign->vars)
-    {
-        TypeId tp = lookupType(var, module, builtinTypes);
-        if (containsAny(tp))
-        {
-            TelemetryTypePair types;
-
-            types.annotatedType = toString(tp);
-
-            auto loc = std::min(assign->vars.size - 1, posn);
-            if (head.size() >= assign->vars.size && posn < head.size())
-            {
-                types.inferredType = toString(head[posn]);
-            }
-            else if (loc < head.size())
-                types.inferredType = toString(head[loc]);
-            else
-                types.inferredType = toString(builtinTypes->nilType);
-
-            TypeInfo ti{Pattern::Assign, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-        ++posn;
-    }
-
-    for (AstExpr* val : assign->values)
-    {
-        if (isAnyCall(scope, val, module, builtinTypes))
-        {
-            TelemetryTypePair types;
-
-            types.inferredType = toString(lookupType(val, module, builtinTypes));
-
-            TypeInfo ti{Pattern::FuncApp, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-
-        if (isAnyCast(scope, val, module, builtinTypes))
-        {
-            if (auto cast = val->as<AstExprTypeAssertion>())
-            {
-                TelemetryTypePair types;
-
-                types.annotatedType = toString(lookupAnnotation(cast->annotation, module, builtinTypes));
-                types.inferredType = toString(lookupType(val, module, builtinTypes));
-
-                TypeInfo ti{Pattern::Casts, toString(ctxNode), types};
-                typeInfo.push_back(ti);
-            }
-        }
-    }
-
-    if (tail)
-    {
-        if (containsAny(*tail))
-        {
-            TelemetryTypePair types;
-
-            types.inferredType = toString(*tail);
-
-            TypeInfo ti{Pattern::Assign, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatCompoundAssign* assign, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    auto ctxNode = getNode(rootSrc, assign);
-
-    TelemetryTypePair types;
-
-    types.inferredType = toString(lookupType(assign->value, module, builtinTypes));
-    types.annotatedType = toString(lookupType(assign->var, module, builtinTypes));
-
-    if (module->astTypes.contains(assign->var))
-    {
-        if (containsAny(*module->astTypes.find(assign->var)))
-        {
-            TypeInfo ti{Pattern::Assign, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-    }
-    else if (module->astTypePacks.contains(assign->var))
-    {
-        if (containsAny(*module->astTypePacks.find(assign->var)))
-        {
-            TypeInfo ti{Pattern::Assign, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-    }
-
-    if (isAnyCall(scope, assign->value, module, builtinTypes))
-    {
-        TypeInfo ti{Pattern::FuncApp, toString(ctxNode), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (isAnyCast(scope, assign->value, module, builtinTypes))
-    {
-        if (auto cast = assign->value->as<AstExprTypeAssertion>())
-        {
-            types.annotatedType = toString(lookupAnnotation(cast->annotation, module, builtinTypes));
-            types.inferredType = toString(lookupType(cast->expr, module, builtinTypes));
-
-            TypeInfo ti{Pattern::Casts, toString(ctxNode), types};
-            typeInfo.push_back(ti);
-        }
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatFunction* function, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    TelemetryTypePair types;
-    types.inferredType = toString(lookupType(function->func, module, builtinTypes));
-
-    if (hasVariadicAnys(scope, function->func, module, builtinTypes))
-    {
-        TypeInfo ti{Pattern::VarAny, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (hasArgAnys(scope, function->func, module, builtinTypes))
-    {
-        TypeInfo ti{Pattern::FuncArg, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (hasAnyReturns(scope, function->func, module, builtinTypes))
-    {
-        TypeInfo ti{Pattern::FuncRet, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (function->func->body->body.size > 0)
-        visit(scope, function->func->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatLocalFunction* function, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    TelemetryTypePair types;
-
-    if (hasVariadicAnys(scope, function->func, module, builtinTypes))
-    {
-        types.inferredType = toString(lookupType(function->func, module, builtinTypes));
-        TypeInfo ti{Pattern::VarAny, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (hasArgAnys(scope, function->func, module, builtinTypes))
-    {
-        types.inferredType = toString(lookupType(function->func, module, builtinTypes));
-        TypeInfo ti{Pattern::FuncArg, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (hasAnyReturns(scope, function->func, module, builtinTypes))
-    {
-        types.inferredType = toString(lookupType(function->func, module, builtinTypes));
-        TypeInfo ti{Pattern::FuncRet, toString(function), types};
-        typeInfo.push_back(ti);
-    }
-
-    if (function->func->body->body.size > 0)
-        visit(scope, function->func->body, module, builtinTypes);
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatTypeAlias* alias, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    auto ctxNode = getNode(rootSrc, alias);
-
-    auto annot = lookupAnnotation(alias->type, module, builtinTypes);
-    if (containsAny(annot))
-    {
-        // no expr => no inference for aliases
-        TelemetryTypePair types;
-
-        types.annotatedType = toString(annot);
-        TypeInfo ti{Pattern::Alias, toString(ctxNode), types};
-        typeInfo.push_back(ti);
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    auto ctxNode = getNode(rootSrc, expr);
-
-    if (isAnyCall(scope, expr->expr, module, builtinTypes))
-    {
-        TelemetryTypePair types;
-        types.inferredType = toString(lookupType(expr->expr, module, builtinTypes));
-
-        TypeInfo ti{Pattern::FuncApp, toString(ctxNode), types};
-        typeInfo.push_back(ti);
-    }
-}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatDeclareGlobal* declareGlobal, const Module* module, NotNull<BuiltinTypes> builtinTypes) {}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatDeclareClass* declareClass, const Module* module, NotNull<BuiltinTypes> builtinTypes) {}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatDeclareFunction* declareFunction, const Module* module, NotNull<BuiltinTypes> builtinTypes) {}
-
-void AnyTypeSummary::visit(const Scope* scope, AstStatError* error, const Module* module, NotNull<BuiltinTypes> builtinTypes) {}
-
-TypeId AnyTypeSummary::checkForFamilyInhabitance(const TypeId instance, const Location location)
-{
-    if (seenTypeFamilyInstances.find(instance))
-        return instance;
-
-    seenTypeFamilyInstances.insert(instance);
-    return instance;
-}
-
-TypeId AnyTypeSummary::lookupType(const AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    const TypeId* ty = module->astTypes.find(expr);
-    if (ty)
-        return checkForFamilyInhabitance(follow(*ty), expr->location);
-
-    const TypePackId* tp = module->astTypePacks.find(expr);
-    if (tp)
-    {
-        if (auto fst = first(*tp, /*ignoreHiddenVariadics*/ false))
-            return checkForFamilyInhabitance(*fst, expr->location);
-        else if (finite(*tp) && size(*tp) == 0)
-            return checkForFamilyInhabitance(builtinTypes->nilType, expr->location);
-    }
-
-    return builtinTypes->errorRecoveryType();
-}
-
-TypePackId AnyTypeSummary::reconstructTypePack(AstArray<AstExpr*> exprs, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (exprs.size == 0)
-        return arena.addTypePack(TypePack{{}, std::nullopt});
-
-    std::vector<TypeId> head;
-
-    for (size_t i = 0; i < exprs.size - 1; ++i)
-    {
-        head.push_back(lookupType(exprs.data[i], module, builtinTypes));
-    }
-
-    const TypePackId* tail = module->astTypePacks.find(exprs.data[exprs.size - 1]);
-    if (tail)
-        return arena.addTypePack(TypePack{std::move(head), follow(*tail)});
-    else
-        return arena.addTypePack(TypePack{std::move(head), builtinTypes->errorRecoveryTypePack()});
-}
-
-bool AnyTypeSummary::isAnyCall(const Scope* scope, AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (auto call = expr->as<AstExprCall>())
-    {
-        TypePackId args = reconstructTypePack(call->args, module, builtinTypes);
-        if (containsAny(args))
-            return true;
-
-        TypeId func = lookupType(call->func, module, builtinTypes);
-        if (containsAny(func))
-            return true;
-    }
-    return false;
-}
-
-bool AnyTypeSummary::hasVariadicAnys(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (expr->vararg && expr->varargAnnotation)
-    {
-        auto annot = lookupPackAnnotation(expr->varargAnnotation, module);
-        if (annot && containsAny(*annot))
-        {
-            return true;
-        }
-    }
-    return false;
-}
-
-bool AnyTypeSummary::hasArgAnys(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (expr->args.size > 0)
-    {
-        for (const AstLocal* arg : expr->args)
-        {
-            if (arg->annotation)
-            {
-                auto annot = lookupAnnotation(arg->annotation, module, builtinTypes);
-                if (containsAny(annot))
-                {
-                    return true;
-                }
-            }
-        }
-    }
-    return false;
-}
-
-bool AnyTypeSummary::hasAnyReturns(const Scope* scope, AstExprFunction* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (!expr->returnAnnotation)
-    {
-        return false;
-    }
-
-    for (AstType* ret : expr->returnAnnotation->types)
-    {
-        if (containsAny(lookupAnnotation(ret, module, builtinTypes)))
-        {
-            return true;
-        }
-    }
-
-    if (expr->returnAnnotation->tailType)
-    {
-        auto annot = lookupPackAnnotation(expr->returnAnnotation->tailType, module);
-        if (annot && containsAny(*annot))
-        {
-            return true;
-        }
-    }
-
-    return false;
-}
-
-bool AnyTypeSummary::isAnyCast(const Scope* scope, AstExpr* expr, const Module* module, NotNull<BuiltinTypes> builtinTypes)
-{
-    if (auto cast = expr->as<AstExprTypeAssertion>())
-    {
-        auto annot = lookupAnnotation(cast->annotation, module, builtinTypes);
-        if (containsAny(annot))
-        {
-            return true;
-        }
-    }
-    return false;
-}
-
-TypeId AnyTypeSummary::lookupAnnotation(AstType* annotation, const Module* module, NotNull<BuiltinTypes> builtintypes)
-{
-    if (FFlag::DebugLuauMagicTypes)
-    {
-        if (auto ref = annotation->as<AstTypeReference>(); ref && ref->parameters.size > 0)
-        {
-            if (auto ann = ref->parameters.data[0].type)
-            {
-                TypeId argTy = lookupAnnotation(ref->parameters.data[0].type, module, builtintypes);
-                return follow(argTy);
-            }
-        }
-    }
-
-    const TypeId* ty = module->astResolvedTypes.find(annotation);
-    if (ty)
-        return checkForTypeFunctionInhabitance(follow(*ty), annotation->location);
-    else
-        return checkForTypeFunctionInhabitance(builtintypes->errorRecoveryType(), annotation->location);
-}
-
-TypeId AnyTypeSummary::checkForTypeFunctionInhabitance(const TypeId instance, const Location location)
-{
-    if (seenTypeFunctionInstances.find(instance))
-        return instance;
-    seenTypeFunctionInstances.insert(instance);
-
-    return instance;
-}
-
-std::optional<TypePackId> AnyTypeSummary::lookupPackAnnotation(AstTypePack* annotation, const Module* module)
-{
-    const TypePackId* tp = module->astResolvedTypePacks.find(annotation);
-    if (tp != nullptr)
-        return {follow(*tp)};
-    return {};
-}
-
-bool AnyTypeSummary::containsAny(TypeId typ)
-{
-    typ = follow(typ);
-
-    if (auto t = seen.find(typ); t && !*t)
-    {
-        return false;
-    }
-
-    seen[typ] = false;
-
-    RecursionCounter counter{&recursionCount};
-    if (recursionCount >= FInt::LuauAnySummaryRecursionLimit)
-    {
-        return false;
-    }
-
-    bool found = false;
-
-    if (auto ty = get<AnyType>(typ))
-    {
-        found = true;
-    }
-    else if (auto ty = get<UnknownType>(typ))
-    {
-        found = true;
-    }
-    else if (auto ty = get<TableType>(typ))
-    {
-        for (auto& [_name, prop] : ty->props)
-        {
-            if (FFlag::LuauSolverV2)
-            {
-                if (auto newT = follow(prop.readTy))
-                {
-                    if (containsAny(*newT))
-                        found = true;
-                }
-                else if (auto newT = follow(prop.writeTy))
-                {
-                    if (containsAny(*newT))
-                        found = true;
-                }
-            }
-            else
-            {
-                if (containsAny(prop.type()))
-                    found = true;
-            }
-        }
-    }
-    else if (auto ty = get<IntersectionType>(typ))
-    {
-        for (auto part : ty->parts)
-        {
-            if (containsAny(part))
-            {
-                found = true;
-            }
-        }
-    }
-    else if (auto ty = get<UnionType>(typ))
-    {
-        for (auto option : ty->options)
-        {
-            if (containsAny(option))
-            {
-                found = true;
-            }
-        }
-    }
-    else if (auto ty = get<FunctionType>(typ))
-    {
-        if (containsAny(ty->argTypes))
-            found = true;
-        else if (containsAny(ty->retTypes))
-            found = true;
-    }
-
-    seen[typ] = found;
-
-    return found;
-}
-
-bool AnyTypeSummary::containsAny(TypePackId typ)
-{
-    typ = follow(typ);
-
-    if (auto t = seen.find(typ); t && !*t)
-    {
-        return false;
-    }
-
-    seen[typ] = false;
-
-    auto [head, tail] = flatten(typ);
-    bool found = false;
-
-    for (auto tp : head)
-    {
-        if (containsAny(tp))
-            found = true;
-    }
-
-    if (tail)
-    {
-        if (auto vtp = get<VariadicTypePack>(tail))
-        {
-            if (auto ty = get<AnyType>(follow(vtp->ty)))
-            {
-                found = true;
-            }
-        }
-        else if (auto tftp = get<TypeFunctionInstanceTypePack>(tail))
-        {
-
-            for (TypePackId tp : tftp->packArguments)
-            {
-                if (containsAny(tp))
-                {
-                    found = true;
-                }
-            }
-
-            for (TypeId t : tftp->typeArguments)
-            {
-                if (containsAny(t))
-                {
-                    found = true;
-                }
-            }
-        }
-    }
-
-    seen[typ] = found;
-
-    return found;
-}
-
-const Scope* AnyTypeSummary::findInnerMostScope(const Location location, const Module* module)
-{
-    const Scope* bestScope = module->getModuleScope().get();
-
-    bool didNarrow = false;
-    do
-    {
-        didNarrow = false;
-        for (auto scope : bestScope->children)
-        {
-            if (scope->location.encloses(location))
-            {
-                bestScope = scope.get();
-                didNarrow = true;
-                break;
-            }
-        }
-    } while (didNarrow && bestScope->children.size() > 0);
-
-    return bestScope;
-}
-
-std::optional<AstExpr*> AnyTypeSummary::matchRequire(const AstExprCall& call)
-{
-    const char* require = "require";
-
-    if (call.args.size != 1)
-        return std::nullopt;
-
-    const AstExprGlobal* funcAsGlobal = call.func->as<AstExprGlobal>();
-    if (!funcAsGlobal || funcAsGlobal->name != require)
-        return std::nullopt;
-
-    if (call.args.size != 1)
-        return std::nullopt;
-
-    return call.args.data[0];
-}
-
-AstNode* AnyTypeSummary::getNode(AstStatBlock* root, AstNode* node)
-{
-    FindReturnAncestry finder(node, root->location.end);
-    root->visit(&finder);
-
-    if (!finder.currNode)
-        finder.currNode = node;
-
-    LUAU_ASSERT(finder.found && finder.currNode);
-    return finder.currNode;
-}
-
-bool AnyTypeSummary::FindReturnAncestry::visit(AstStatLocalFunction* node)
-{
-    currNode = node;
-    return !found;
-}
-
-bool AnyTypeSummary::FindReturnAncestry::visit(AstStatFunction* node)
-{
-    currNode = node;
-    return !found;
-}
-
-bool AnyTypeSummary::FindReturnAncestry::visit(AstType* node)
-{
-    return !found;
-}
-
-bool AnyTypeSummary::FindReturnAncestry::visit(AstNode* node)
-{
-    if (node == stat)
-    {
-        found = true;
-    }
-
-    if (node->location.end == rootEnd && stat->location.end >= rootEnd)
-    {
-        currNode = node;
-        found = true;
-    }
-
-    return !found;
-}
-
-
-AnyTypeSummary::TypeInfo::TypeInfo(Pattern code, std::string node, TelemetryTypePair type)
-    : code(code)
-    , node(node)
-    , type(type)
-{
-}
-
-AnyTypeSummary::FindReturnAncestry::FindReturnAncestry(AstNode* stat, Position rootEnd)
-    : stat(stat)
-    , rootEnd(rootEnd)
-{
-}
-
-AnyTypeSummary::AnyTypeSummary() {}
-
-} // namespace Luau

Analysis/src/AstJsonEncoder.cpp

@@ -1065,6 +1065,11 @@ struct AstJsonEncoder : public AstVisitor
         );
     }
 
+    void write(class AstTypeOptional* node)
+    {
+        writeNode(node, "AstTypeOptional", [&]() {});
+    }
+
     void write(class AstTypeUnion* node)
     {
         writeNode(
@@ -1146,6 +1151,8 @@ struct AstJsonEncoder : public AstVisitor
             return writeString("checked");
         case AstAttr::Type::Native:
             return writeString("native");
+        case AstAttr::Type::Deprecated:
+            return writeString("deprecated");
         }
     }
 

Analysis/src/AstQuery.cpp

@@ -13,8 +13,6 @@
 
 LUAU_FASTFLAG(LuauSolverV2)
 
-LUAU_FASTFLAG(LuauExtendStatEndPosWithSemicolon)
-
 namespace Luau
 {
 
@@ -43,24 +41,13 @@ struct AutocompleteNodeFinder : public AstVisitor
 
     bool visit(AstStat* stat) override
     {
-        if (FFlag::LuauExtendStatEndPosWithSemicolon)
+        // Consider 'local myLocal = 4;|' and 'local myLocal = 4', where '|' is the cursor position. In both cases, the cursor position is equal
+        // to `AstStatLocal.location.end`. However, in the first case (semicolon), we are starting a new statement, whilst in the second case
+        // (no semicolon) we are still part of the AstStatLocal, hence the different comparison check.
+        if (stat->location.begin < pos && (stat->hasSemicolon ? pos < stat->location.end : pos <= stat->location.end))
         {
-            // Consider 'local myLocal = 4;|' and 'local myLocal = 4', where '|' is the cursor position. In both cases, the cursor position is equal
+            ancestry.push_back(stat);
-            // to `AstStatLocal.location.end`. However, in the first case (semicolon), we are starting a new statement, whilst in the second case
+            return true;
-            // (no semicolon) we are still part of the AstStatLocal, hence the different comparison check.
-            if (stat->location.begin < pos && (stat->hasSemicolon ? pos < stat->location.end : pos <= stat->location.end))
-            {
-                ancestry.push_back(stat);
-                return true;
-            }
-        }
-        else
-        {
-            if (stat->location.begin < pos && pos <= stat->location.end)
-            {
-                ancestry.push_back(stat);
-                return true;
-            }
         }
 
         return false;

Analysis/src/AutocompleteCore.cpp

@@ -23,10 +23,14 @@
 LUAU_FASTFLAG(LuauSolverV2)
 LUAU_FASTINT(LuauTypeInferIterationLimit)
 LUAU_FASTINT(LuauTypeInferRecursionLimit)
+LUAU_FASTFLAGVARIABLE(DebugLuauMagicVariableNames)
+
+LUAU_FASTFLAG(LuauExposeRequireByStringAutocomplete)
 
 LUAU_FASTFLAGVARIABLE(LuauAutocompleteRefactorsForIncrementalAutocomplete)
 
 LUAU_FASTFLAGVARIABLE(LuauAutocompleteUsesModuleForTypeCompatibility)
+LUAU_FASTFLAGVARIABLE(LuauAutocompleteUnionCopyPreviousSeen)
 
 static const std::unordered_set<std::string> kStatementStartingKeywords =
     {"while", "if", "local", "repeat", "function", "do", "for", "return", "break", "continue", "type", "export"};
@@ -481,6 +485,21 @@ static void autocompleteProps(
             AutocompleteEntryMap inner;
             std::unordered_set<TypeId> innerSeen;
 
+            // If we don't do this, and we have the misfortune of receiving a
+            // recursive union like:
+            //
+            //  t1 where t1 = t1 | Class
+            //
+            // Then we are on a one way journey to a stack overflow.
+            if (FFlag::LuauAutocompleteUnionCopyPreviousSeen)
+            {
+                for (auto ty : seen)
+                {
+                    if (is<UnionType, IntersectionType>(ty))
+                        innerSeen.insert(ty);
+                }
+            }
+
             if (isNil(*iter))
             {
                 ++iter;
@@ -1343,6 +1362,15 @@ static AutocompleteContext autocompleteExpression(
 
     AstNode* node = ancestry.rbegin()[0];
 
+    if (FFlag::DebugLuauMagicVariableNames)
+    {
+        InternalErrorReporter ice;
+        if (auto local = node->as<AstExprLocal>(); local && local->local->name == "_luau_autocomplete_ice")
+            ice.ice("_luau_autocomplete_ice encountered", local->location);
+        if (auto global = node->as<AstExprGlobal>(); global && global->name == "_luau_autocomplete_ice")
+            ice.ice("_luau_autocomplete_ice encountered", global->location);
+    }
+
     if (node->is<AstExprIndexName>())
     {
         if (auto it = module.astTypes.find(node->asExpr()))
@@ -1509,10 +1537,14 @@ static std::optional<AutocompleteEntryMap> convertRequireSuggestionsToAutocomple
         return std::nullopt;
 
     AutocompleteEntryMap result;
-    for (const RequireSuggestion& suggestion : *suggestions)
+    for (RequireSuggestion& suggestion : *suggestions)
     {
         AutocompleteEntry entry = {AutocompleteEntryKind::RequirePath};
         entry.insertText = std::move(suggestion.fullPath);
+        if (FFlag::LuauExposeRequireByStringAutocomplete)
+        {
+            entry.tags = std::move(suggestion.tags);
+        }
         result[std::move(suggestion.label)] = std::move(entry);
     }
     return result;

Analysis/src/BuiltinDefinitions.cpp

@@ -3,22 +3,23 @@
 
 #include "Luau/Ast.h"
 #include "Luau/Clone.h"
+#include "Luau/Common.h"
+#include "Luau/ConstraintGenerator.h"
+#include "Luau/ConstraintSolver.h"
 #include "Luau/DenseHash.h"
 #include "Luau/Error.h"
 #include "Luau/Frontend.h"
-#include "Luau/Symbol.h"
+#include "Luau/InferPolarity.h"
-#include "Luau/Common.h"
-#include "Luau/ToString.h"
-#include "Luau/ConstraintSolver.h"
-#include "Luau/ConstraintGenerator.h"
 #include "Luau/NotNull.h"
-#include "Luau/TypeInfer.h"
+#include "Luau/Subtyping.h"
+#include "Luau/Symbol.h"
+#include "Luau/ToString.h"
+#include "Luau/Type.h"
 #include "Luau/TypeChecker2.h"
 #include "Luau/TypeFunction.h"
+#include "Luau/TypeInfer.h"
 #include "Luau/TypePack.h"
-#include "Luau/Type.h"
 #include "Luau/TypeUtils.h"
-#include "Luau/Subtyping.h"
 
 #include <algorithm>
 
@@ -29,11 +30,12 @@
  */
 
 LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAGVARIABLE(LuauStringFormatErrorSuppression)
+LUAU_FASTFLAG(LuauNonReentrantGeneralization)
 LUAU_FASTFLAGVARIABLE(LuauTableCloneClonesType3)
 LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope)
-LUAU_FASTFLAGVARIABLE(LuauFreezeIgnorePersistent)
 LUAU_FASTFLAGVARIABLE(LuauFollowTableFreeze)
+LUAU_FASTFLAGVARIABLE(LuauUserTypeFunTypecheck)
+LUAU_FASTFLAGVARIABLE(LuauMagicFreezeCheckBlocked)
 
 namespace Luau
 {
@@ -247,6 +249,7 @@ void addGlobalBinding(GlobalTypes& globals, const ScopePtr& scope, const std::st
 
 void addGlobalBinding(GlobalTypes& globals, const ScopePtr& scope, const std::string& name, Binding binding)
 {
+    inferGenericPolarities(NotNull{&globals.globalTypes}, NotNull{scope.get()}, binding.typeId);
     scope->bindings[globals.globalNames.names->getOrAdd(name.c_str())] = binding;
 }
 
@@ -288,6 +291,22 @@ void assignPropDocumentationSymbols(TableType::Props& props, const std::string&
     }
 }
 
+static void finalizeGlobalBindings(ScopePtr scope)
+{
+    LUAU_ASSERT(FFlag::LuauUserTypeFunTypecheck);
+
+    for (const auto& pair : scope->bindings)
+    {
+        persist(pair.second.typeId);
+
+        if (TableType* ttv = getMutable<TableType>(pair.second.typeId))
+        {
+            if (!ttv->name)
+                ttv->name = "typeof(" + toString(pair.first) + ")";
+        }
+    }
+}
+
 void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeCheckForAutocomplete)
 {
     LUAU_ASSERT(!globals.globalTypes.types.isFrozen());
@@ -295,6 +314,9 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
 
     TypeArena& arena = globals.globalTypes;
     NotNull<BuiltinTypes> builtinTypes = globals.builtinTypes;
+    Scope* globalScope = nullptr; // NotNull<Scope> when removing FFlag::LuauNonReentrantGeneralization
+    if (FFlag::LuauNonReentrantGeneralization)
+        globalScope = globals.globalScope.get();
 
     if (FFlag::LuauSolverV2)
         builtinTypeFunctions().addToScope(NotNull{&arena}, NotNull{globals.globalScope.get()});
@@ -304,8 +326,8 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
     );
     LUAU_ASSERT(loadResult.success);
 
-    TypeId genericK = arena.addType(GenericType{"K"});
+    TypeId genericK = arena.addType(GenericType{globalScope, "K"});
-    TypeId genericV = arena.addType(GenericType{"V"});
+    TypeId genericV = arena.addType(GenericType{globalScope, "V"});
     TypeId mapOfKtoV = arena.addType(TableType{{}, TableIndexer(genericK, genericV), globals.globalScope->level, TableState::Generic});
 
     std::optional<TypeId> stringMetatableTy = getMetatable(builtinTypes->stringType, builtinTypes);
@@ -353,7 +375,7 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
     // pairs<K, V>(t: Table<K, V>) -> ((Table<K, V>, K?) -> (K, V), Table<K, V>, nil)
     addGlobalBinding(globals, "pairs", arena.addType(FunctionType{{genericK, genericV}, {}, pairsArgsTypePack, pairsReturnTypePack}), "@luau");
 
-    TypeId genericMT = arena.addType(GenericType{"MT"});
+    TypeId genericMT = arena.addType(GenericType{globalScope, "MT"});
 
     TableType tab{TableState::Generic, globals.globalScope->level};
     TypeId tabTy = arena.addType(tab);
@@ -365,7 +387,7 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
 
     if (FFlag::LuauSolverV2)
     {
-        TypeId genericT = arena.addType(GenericType{"T"});
+        TypeId genericT = arena.addType(GenericType{globalScope, "T"});
         TypeId tMetaMT = arena.addType(MetatableType{genericT, genericMT});
 
         // clang-format off
@@ -399,14 +421,21 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
         // clang-format on
     }
 
-    for (const auto& pair : globals.globalScope->bindings)
+    if (FFlag::LuauUserTypeFunTypecheck)
     {
-        persist(pair.second.typeId);
+        finalizeGlobalBindings(globals.globalScope);
-
+    }
-        if (TableType* ttv = getMutable<TableType>(pair.second.typeId))
+    else
+    {
+        for (const auto& pair : globals.globalScope->bindings)
         {
-            if (!ttv->name)
+            persist(pair.second.typeId);
-                ttv->name = "typeof(" + toString(pair.first) + ")";
+
+            if (TableType* ttv = getMutable<TableType>(pair.second.typeId))
+            {
+                if (!ttv->name)
+                    ttv->name = "typeof(" + toString(pair.first) + ")";
+            }
         }
     }
 
@@ -415,7 +444,7 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
     if (FFlag::LuauSolverV2)
     {
         // declare function assert<T>(value: T, errorMessage: string?): intersect<T, ~(false?)>
-        TypeId genericT = arena.addType(GenericType{"T"});
+        TypeId genericT = arena.addType(GenericType{globalScope, "T"});
         TypeId refinedTy = arena.addType(TypeFunctionInstanceType{
             NotNull{&builtinTypeFunctions().intersectFunc}, {genericT, arena.addType(NegationType{builtinTypes->falsyType})}, {}
         });
@@ -438,12 +467,16 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
             // the top table type.  We do the best we can by modelling these
             // functions using unconstrained generics.  It's not quite right,
             // but it'll be ok for now.
-            TypeId genericTy = arena.addType(GenericType{"T"});
+            TypeId genericTy = arena.addType(GenericType{globalScope, "T"});
             TypePackId thePack = arena.addTypePack({genericTy});
             TypeId idTyWithMagic = arena.addType(FunctionType{{genericTy}, {}, thePack, thePack});
             ttv->props["freeze"] = makeProperty(idTyWithMagic, "@luau/global/table.freeze");
+            if (globalScope)
+                inferGenericPolarities(NotNull{&globals.globalTypes}, NotNull{globalScope}, idTyWithMagic);
 
             TypeId idTy = arena.addType(FunctionType{{genericTy}, {}, thePack, thePack});
+            if (globalScope)
+                inferGenericPolarities(NotNull{&globals.globalTypes}, NotNull{globalScope}, idTy);
             ttv->props["clone"] = makeProperty(idTy, "@luau/global/table.clone");
         }
         else
@@ -467,6 +500,59 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
     TypeId requireTy = getGlobalBinding(globals, "require");
     attachTag(requireTy, kRequireTagName);
     attachMagicFunction(requireTy, std::make_shared<MagicRequire>());
+
+    if (FFlag::LuauUserTypeFunTypecheck)
+    {
+        // Global scope cannot be the parent of the type checking environment because it can be changed by the embedder
+        globals.globalTypeFunctionScope->exportedTypeBindings = globals.globalScope->exportedTypeBindings;
+        globals.globalTypeFunctionScope->builtinTypeNames = globals.globalScope->builtinTypeNames;
+
+        // Type function runtime also removes a few standard libraries and globals, so we will take only the ones that are defined
+        static const char* typeFunctionRuntimeBindings[] = {
+            // Libraries
+            "math",
+            "table",
+            "string",
+            "bit32",
+            "utf8",
+            "buffer",
+
+            // Globals
+            "assert",
+            "error",
+            "print",
+            "next",
+            "ipairs",
+            "pairs",
+            "select",
+            "unpack",
+            "getmetatable",
+            "setmetatable",
+            "rawget",
+            "rawset",
+            "rawlen",
+            "rawequal",
+            "tonumber",
+            "tostring",
+            "type",
+            "typeof",
+        };
+
+        for (auto& name : typeFunctionRuntimeBindings)
+        {
+            AstName astName = globals.globalNames.names->get(name);
+            LUAU_ASSERT(astName.value);
+
+            globals.globalTypeFunctionScope->bindings[astName] = globals.globalScope->bindings[astName];
+        }
+
+        LoadDefinitionFileResult typeFunctionLoadResult = frontend.loadDefinitionFile(
+            globals, globals.globalTypeFunctionScope, getTypeFunctionDefinitionSource(), "@luau", /* captureComments */ false, false
+        );
+        LUAU_ASSERT(typeFunctionLoadResult.success);
+
+        finalizeGlobalBindings(globals.globalTypeFunctionScope);
+    }
 }
 
 static std::vector<TypeId> parseFormatString(NotNull<BuiltinTypes> builtinTypes, const char* data, size_t size)
@@ -636,25 +722,17 @@ bool MagicFormat::typeCheck(const MagicFunctionTypeCheckContext& context)
 
         if (!result.isSubtype)
         {
-            if (FFlag::LuauStringFormatErrorSuppression)
+            switch (shouldSuppressErrors(NotNull{&context.typechecker->normalizer}, actualTy))
-            {
-                switch (shouldSuppressErrors(NotNull{&context.typechecker->normalizer}, actualTy))
-                {
-                case ErrorSuppression::Suppress:
-                    break;
-                case ErrorSuppression::NormalizationFailed:
-                    break;
-                case ErrorSuppression::DoNotSuppress:
-                    Reasonings reasonings = context.typechecker->explainReasonings(actualTy, expectedTy, location, result);
-
-                    if (!reasonings.suppressed)
-                        context.typechecker->reportError(TypeMismatch{expectedTy, actualTy, reasonings.toString()}, location);
-                }
-            }
-            else
             {
+            case ErrorSuppression::Suppress:
+                break;
+            case ErrorSuppression::NormalizationFailed:
+                break;
+            case ErrorSuppression::DoNotSuppress:
                 Reasonings reasonings = context.typechecker->explainReasonings(actualTy, expectedTy, location, result);
-                context.typechecker->reportError(TypeMismatch{expectedTy, actualTy, reasonings.toString()}, location);
+
+                if (!reasonings.suppressed)
+                    context.typechecker->reportError(TypeMismatch{expectedTy, actualTy, reasonings.toString()}, location);
             }
         }
     }
@@ -1444,7 +1522,7 @@ bool MagicClone::infer(const MagicFunctionCallContext& context)
         return false;
 
     CloneState cloneState{context.solver->builtinTypes};
-    TypeId resultType = shallowClone(inputType, *arena, cloneState, /* ignorePersistent */ FFlag::LuauFreezeIgnorePersistent);
+    TypeId resultType = shallowClone(inputType, *arena, cloneState, /* ignorePersistent */ true);
 
     if (auto tableType = getMutable<TableType>(resultType))
     {
@@ -1481,7 +1559,7 @@ static std::optional<TypeId> freezeTable(TypeId inputType, const MagicFunctionCa
     {
         // Clone the input type, this will become our final result type after we mutate it.
         CloneState cloneState{context.solver->builtinTypes};
-        TypeId resultType = shallowClone(inputType, *arena, cloneState, /* ignorePersistent */ FFlag::LuauFreezeIgnorePersistent);
+        TypeId resultType = shallowClone(inputType, *arena, cloneState, /* ignorePersistent */ true);
         auto tableTy = getMutable<TableType>(resultType);
         // `clone` should not break this.
         LUAU_ASSERT(tableTy);
@@ -1531,6 +1609,17 @@ bool MagicFreeze::infer(const MagicFunctionCallContext& context)
     std::optional<DefId> resultDef = dfg->getDefOptional(targetExpr);
     std::optional<TypeId> resultTy = resultDef ? scope->lookup(*resultDef) : std::nullopt;
 
+    if (FFlag::LuauMagicFreezeCheckBlocked)
+    {
+        if (resultTy && !get<BlockedType>(resultTy))
+        {
+            // If there's an existing result type but it's _not_ blocked, then
+            // we aren't type stating this builtin and should fall back to 
+            // regular inference.
+            return false;
+        }
+    }
+
     std::optional<TypeId> frozenType = freezeTable(inputType, context);
 
     if (!frozenType)

Analysis/src/Clone.cpp

@@ -1,17 +1,20 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Clone.h"
 
+#include "Luau/Common.h"
 #include "Luau/NotNull.h"
 #include "Luau/Type.h"
 #include "Luau/TypePack.h"
 #include "Luau/Unifiable.h"
+#include "Luau/VisitType.h"
 
 LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAG(LuauFreezeIgnorePersistent)
 
 // For each `Luau::clone` call, we will clone only up to N amount of types _and_ packs, as controlled by this limit.
 LUAU_FASTINTVARIABLE(LuauTypeCloneIterationLimit, 100'000)
-
+LUAU_FASTFLAGVARIABLE(LuauClonedTableAndFunctionTypesMustHaveScopes)
+LUAU_FASTFLAGVARIABLE(LuauDoNotClonePersistentBindings)
+LUAU_FASTFLAG(LuauIncrementalAutocompleteDemandBasedCloning)
 namespace Luau
 {
 
@@ -28,6 +31,8 @@ const T* get(const Kind& kind)
 
 class TypeCloner
 {
+
+protected:
     NotNull<TypeArena> arena;
     NotNull<BuiltinTypes> builtinTypes;
 
@@ -62,6 +67,8 @@ public:
     {
     }
 
+    virtual ~TypeCloner() = default;
+
     TypeId clone(TypeId ty)
     {
         shallowClone(ty);
@@ -120,12 +127,13 @@ private:
         }
     }
 
+protected:
     std::optional<TypeId> find(TypeId ty) const
     {
         ty = follow(ty, FollowOption::DisableLazyTypeThunks);
         if (auto it = types->find(ty); it != types->end())
             return it->second;
-        else if (ty->persistent && (!FFlag::LuauFreezeIgnorePersistent || ty != forceTy))
+        else if (ty->persistent && ty != forceTy)
             return ty;
         return std::nullopt;
     }
@@ -135,7 +143,7 @@ private:
         tp = follow(tp);
         if (auto it = packs->find(tp); it != packs->end())
             return it->second;
-        else if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || tp != forceTp))
+        else if (tp->persistent && tp != forceTp)
             return tp;
         return std::nullopt;
     }
@@ -154,14 +162,14 @@ private:
     }
 
 public:
-    TypeId shallowClone(TypeId ty)
+    virtual TypeId shallowClone(TypeId ty)
     {
         // We want to [`Luau::follow`] but without forcing the expansion of [`LazyType`]s.
         ty = follow(ty, FollowOption::DisableLazyTypeThunks);
 
         if (auto clone = find(ty))
             return *clone;
-        else if (ty->persistent && (!FFlag::LuauFreezeIgnorePersistent || ty != forceTy))
+        else if (ty->persistent && ty != forceTy)
             return ty;
 
         TypeId target = arena->addType(ty->ty);
@@ -171,8 +179,6 @@ public:
             generic->scope = nullptr;
         else if (auto free = getMutable<FreeType>(target))
             free->scope = nullptr;
-        else if (auto fn = getMutable<FunctionType>(target))
-            fn->scope = nullptr;
         else if (auto table = getMutable<TableType>(target))
             table->scope = nullptr;
 
@@ -181,13 +187,13 @@ public:
         return target;
     }
 
-    TypePackId shallowClone(TypePackId tp)
+    virtual TypePackId shallowClone(TypePackId tp)
     {
         tp = follow(tp);
 
         if (auto clone = find(tp))
             return *clone;
-        else if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || tp != forceTp))
+        else if (tp->persistent && tp != forceTp)
             return tp;
 
         TypePackId target = arena->addTypePack(tp->ty);
@@ -389,7 +395,7 @@ private:
             ty = shallowClone(ty);
     }
 
-    void cloneChildren(LazyType* t)
+    virtual void cloneChildren(LazyType* t)
     {
         if (auto unwrapped = t->unwrapped.load())
             t->unwrapped.store(shallowClone(unwrapped));
@@ -469,11 +475,94 @@ private:
     }
 };
 
+class FragmentAutocompleteTypeCloner final : public TypeCloner
+{
+    Scope* replacementForNullScope = nullptr;
+
+public:
+    FragmentAutocompleteTypeCloner(
+        NotNull<TypeArena> arena,
+        NotNull<BuiltinTypes> builtinTypes,
+        NotNull<SeenTypes> types,
+        NotNull<SeenTypePacks> packs,
+        TypeId forceTy,
+        TypePackId forceTp,
+        Scope* replacementForNullScope
+    )
+        : TypeCloner(arena, builtinTypes, types, packs, forceTy, forceTp)
+        , replacementForNullScope(replacementForNullScope)
+    {
+        LUAU_ASSERT(replacementForNullScope);
+    }
+
+    TypeId shallowClone(TypeId ty) override
+    {
+        // We want to [`Luau::follow`] but without forcing the expansion of [`LazyType`]s.
+        ty = follow(ty, FollowOption::DisableLazyTypeThunks);
+
+        if (auto clone = find(ty))
+            return *clone;
+        else if (ty->persistent && ty != forceTy)
+            return ty;
+
+        TypeId target = arena->addType(ty->ty);
+        asMutable(target)->documentationSymbol = ty->documentationSymbol;
+
+        if (auto generic = getMutable<GenericType>(target))
+            generic->scope = nullptr;
+        else if (auto free = getMutable<FreeType>(target))
+        {
+            free->scope = replacementForNullScope;
+        }
+        else if (auto tt = getMutable<TableType>(target))
+        {
+            if (FFlag::LuauClonedTableAndFunctionTypesMustHaveScopes)
+                tt->scope = replacementForNullScope;
+        }
+
+        (*types)[ty] = target;
+        queue.emplace_back(target);
+        return target;
+    }
+
+    TypePackId shallowClone(TypePackId tp) override
+    {
+        tp = follow(tp);
+
+        if (auto clone = find(tp))
+            return *clone;
+        else if (tp->persistent && tp != forceTp)
+            return tp;
+
+        TypePackId target = arena->addTypePack(tp->ty);
+
+        if (auto generic = getMutable<GenericTypePack>(target))
+            generic->scope = nullptr;
+        else if (auto free = getMutable<FreeTypePack>(target))
+            free->scope = replacementForNullScope;
+
+        (*packs)[tp] = target;
+        queue.emplace_back(target);
+        return target;
+    }
+
+    void cloneChildren(LazyType* t) override
+    {
+        // Do not clone lazy types
+        if (!FFlag::LuauIncrementalAutocompleteDemandBasedCloning)
+        {
+            if (auto unwrapped = t->unwrapped.load())
+                t->unwrapped.store(shallowClone(unwrapped));
+        }
+    }
+};
+
+
 } // namespace
 
 TypePackId shallowClone(TypePackId tp, TypeArena& dest, CloneState& cloneState, bool ignorePersistent)
 {
-    if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || !ignorePersistent))
+    if (tp->persistent && !ignorePersistent)
         return tp;
 
     TypeCloner cloner{
@@ -482,7 +571,7 @@ TypePackId shallowClone(TypePackId tp, TypeArena& dest, CloneState& cloneState,
         NotNull{&cloneState.seenTypes},
         NotNull{&cloneState.seenTypePacks},
         nullptr,
-        FFlag::LuauFreezeIgnorePersistent && ignorePersistent ? tp : nullptr
+        ignorePersistent ? tp : nullptr
     };
 
     return cloner.shallowClone(tp);
@@ -490,7 +579,7 @@ TypePackId shallowClone(TypePackId tp, TypeArena& dest, CloneState& cloneState,
 
 TypeId shallowClone(TypeId typeId, TypeArena& dest, CloneState& cloneState, bool ignorePersistent)
 {
-    if (typeId->persistent && (!FFlag::LuauFreezeIgnorePersistent || !ignorePersistent))
+    if (typeId->persistent && !ignorePersistent)
         return typeId;
 
     TypeCloner cloner{
@@ -498,7 +587,7 @@ TypeId shallowClone(TypeId typeId, TypeArena& dest, CloneState& cloneState, bool
         cloneState.builtinTypes,
         NotNull{&cloneState.seenTypes},
         NotNull{&cloneState.seenTypePacks},
-        FFlag::LuauFreezeIgnorePersistent && ignorePersistent ? typeId : nullptr,
+        ignorePersistent ? typeId : nullptr,
         nullptr
     };
 
@@ -564,4 +653,96 @@ Binding clone(const Binding& binding, TypeArena& dest, CloneState& cloneState)
     return b;
 }
 
+TypePackId cloneIncremental(TypePackId tp, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes)
+{
+    if (tp->persistent)
+        return tp;
+
+    FragmentAutocompleteTypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        nullptr,
+        nullptr,
+        freshScopeForFreeTypes
+    };
+    return cloner.clone(tp);
+}
+
+TypeId cloneIncremental(TypeId typeId, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes)
+{
+    if (typeId->persistent)
+        return typeId;
+
+    FragmentAutocompleteTypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        nullptr,
+        nullptr,
+        freshScopeForFreeTypes
+    };
+    return cloner.clone(typeId);
+}
+
+TypeFun cloneIncremental(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes)
+{
+    FragmentAutocompleteTypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        nullptr,
+        nullptr,
+        freshScopeForFreeTypes
+    };
+
+    TypeFun copy = typeFun;
+
+    for (auto& param : copy.typeParams)
+    {
+        param.ty = cloner.clone(param.ty);
+
+        if (param.defaultValue)
+            param.defaultValue = cloner.clone(*param.defaultValue);
+    }
+
+    for (auto& param : copy.typePackParams)
+    {
+        param.tp = cloner.clone(param.tp);
+
+        if (param.defaultValue)
+            param.defaultValue = cloner.clone(*param.defaultValue);
+    }
+
+    copy.type = cloner.clone(copy.type);
+
+    return copy;
+}
+
+Binding cloneIncremental(const Binding& binding, TypeArena& dest, CloneState& cloneState, Scope* freshScopeForFreeTypes)
+{
+    FragmentAutocompleteTypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        nullptr,
+        nullptr,
+        freshScopeForFreeTypes
+    };
+
+    Binding b;
+    b.deprecated = binding.deprecated;
+    b.deprecatedSuggestion = binding.deprecatedSuggestion;
+    b.documentationSymbol = binding.documentationSymbol;
+    b.location = binding.location;
+    b.typeId = FFlag::LuauDoNotClonePersistentBindings && binding.typeId->persistent ? binding.typeId : cloner.clone(binding.typeId);
+
+    return b;
+}
+
+
 } // namespace Luau

Analysis/src/ConstraintSolver.cpp

@@ -35,8 +35,14 @@ LUAU_FASTINTVARIABLE(LuauSolverRecursionLimit, 500)
 LUAU_FASTFLAGVARIABLE(DebugLuauEqSatSimplification)
 LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope)
 LUAU_FASTFLAGVARIABLE(LuauTrackInteriorFreeTablesOnScope)
-LUAU_FASTFLAGVARIABLE(LuauPrecalculateMutatedFreeTypes2)
+LUAU_FASTFLAGVARIABLE(LuauHasPropProperBlock)
 LUAU_FASTFLAGVARIABLE(DebugLuauGreedyGeneralization)
+LUAU_FASTFLAG(LuauSearchForRefineableType)
+LUAU_FASTFLAG(LuauDeprecatedAttribute)
+LUAU_FASTFLAG(LuauNonReentrantGeneralization)
+LUAU_FASTFLAG(LuauBidirectionalInferenceCollectIndexerTypes)
+LUAU_FASTFLAG(LuauNewTypeFunReductionChecks2)
+LUAU_FASTFLAGVARIABLE(LuauTrackInferredFunctionTypeFromCall)
 
 namespace Luau
 {
@@ -356,32 +362,19 @@ ConstraintSolver::ConstraintSolver(
     {
         unsolvedConstraints.emplace_back(c);
 
-        if (FFlag::LuauPrecalculateMutatedFreeTypes2)
+        auto maybeMutatedTypesPerConstraint = c->getMaybeMutatedFreeTypes();
+        for (auto ty : maybeMutatedTypesPerConstraint)
         {
-            auto maybeMutatedTypesPerConstraint = c->getMaybeMutatedFreeTypes();
+            auto [refCount, _] = unresolvedConstraints.try_insert(ty, 0);
-            for (auto ty : maybeMutatedTypesPerConstraint)
+            refCount += 1;
-            {
-                auto [refCount, _] = unresolvedConstraints.try_insert(ty, 0);
-                refCount += 1;
 
-                if (FFlag::DebugLuauGreedyGeneralization)
+            if (FFlag::DebugLuauGreedyGeneralization)
-                {
-                    auto [it, fresh] = mutatedFreeTypeToConstraint.try_emplace(ty, DenseHashSet<const Constraint*>{nullptr});
-                    it->second.insert(c.get());
-                }
-            }
-            maybeMutatedFreeTypes.emplace(c, maybeMutatedTypesPerConstraint);
-        }
-        else
-        {
-            // initialize the reference counts for the free types in this constraint.
-            for (auto ty : c->getMaybeMutatedFreeTypes())
             {
-                // increment the reference count for `ty`
+                auto [it, fresh] = mutatedFreeTypeToConstraint.try_emplace(ty, DenseHashSet<const Constraint*>{nullptr});
-                auto [refCount, _] = unresolvedConstraints.try_insert(ty, 0);
+                it->second.insert(c.get());
-                refCount += 1;
             }
         }
+        maybeMutatedFreeTypes.emplace(c, maybeMutatedTypesPerConstraint);
 
 
         for (NotNull<const Constraint> dep : c->dependencies)
@@ -472,48 +465,24 @@ void ConstraintSolver::run()
                 unblock(c);
                 unsolvedConstraints.erase(unsolvedConstraints.begin() + ptrdiff_t(i));
 
-                if (FFlag::LuauPrecalculateMutatedFreeTypes2)
+                const auto maybeMutated = maybeMutatedFreeTypes.find(c);
+                if (maybeMutated != maybeMutatedFreeTypes.end())
                 {
-                    const auto maybeMutated = maybeMutatedFreeTypes.find(c);
+                    DenseHashSet<TypeId> seen{nullptr};
-                    if (maybeMutated != maybeMutatedFreeTypes.end())
+                    for (auto ty : maybeMutated->second)
                     {
-                        DenseHashSet<TypeId> seen{nullptr};
+                        // There is a high chance that this type has been rebound
-                        for (auto ty : maybeMutated->second)
+                        // across blocked types, rebound free types, pending
+                        // expansion types, etc, so we need to follow it.
+                        ty = follow(ty);
+
+                        if (FFlag::DebugLuauGreedyGeneralization)
                         {
-                            // There is a high chance that this type has been rebound
+                            if (seen.contains(ty))
-                            // across blocked types, rebound free types, pending
+                                continue;
-                            // expansion types, etc, so we need to follow it.
+                            seen.insert(ty);
-                            ty = follow(ty);
-
-                            if (FFlag::DebugLuauGreedyGeneralization)
-                            {
-                                if (seen.contains(ty))
-                                    continue;
-                                seen.insert(ty);
-                            }
-
-                            size_t& refCount = unresolvedConstraints[ty];
-                            if (refCount > 0)
-                                refCount -= 1;
-
-                            // We have two constraints that are designed to wait for the
-                            // refCount on a free type to be equal to 1: the
-                            // PrimitiveTypeConstraint and ReduceConstraint. We
-                            // therefore wake any constraint waiting for a free type's
-                            // refcount to be 1 or 0.
-                            if (refCount <= 1)
-                                unblock(ty, Location{});
-
-                            if (FFlag::DebugLuauGreedyGeneralization && refCount == 0)
-                                generalizeOneType(ty);
                         }
-                    }
+
-                }
-                else
-                {
-                    // decrement the referenced free types for this constraint if we dispatched successfully!
-                    for (auto ty : c->getMaybeMutatedFreeTypes())
-                    {
                         size_t& refCount = unresolvedConstraints[ty];
                         if (refCount > 0)
                             refCount -= 1;
@@ -525,6 +494,9 @@ void ConstraintSolver::run()
                         // refcount to be 1 or 0.
                         if (refCount <= 1)
                             unblock(ty, Location{});
+
+                        if (FFlag::DebugLuauGreedyGeneralization && refCount == 0)
+                            generalizeOneType(ty);
                     }
                 }
 
@@ -624,32 +596,30 @@ bool ConstraintSolver::isDone() const
 
 struct TypeSearcher : TypeVisitor
 {
-    enum struct Polarity: uint8_t
-    {
-        None = 0b00,
-        Positive = 0b01,
-        Negative = 0b10,
-        Mixed = 0b11,
-    };
-
     TypeId needle;
     Polarity current = Polarity::Positive;
 
+    size_t count = 0;
     Polarity result = Polarity::None;
 
     explicit TypeSearcher(TypeId needle)
         : TypeSearcher(needle, Polarity::Positive)
-    {}
+    {
+    }
 
     explicit TypeSearcher(TypeId needle, Polarity initialPolarity)
         : needle(needle)
         , current(initialPolarity)
-    {}
+    {
+    }
 
     bool visit(TypeId ty) override
     {
         if (ty == needle)
-            result = Polarity(int(result) | int(current));
+        {
+            ++count;
+            result = Polarity(size_t(result) | size_t(current));
+        }
 
         return true;
     }
@@ -658,14 +628,14 @@ struct TypeSearcher : TypeVisitor
     {
         switch (current)
         {
-            case Polarity::Positive:
+        case Polarity::Positive:
-                current = Polarity::Negative;
+            current = Polarity::Negative;
-                break;
+            break;
-            case Polarity::Negative:
+        case Polarity::Negative:
-                current = Polarity::Positive;
+            current = Polarity::Positive;
-                break;
+            break;
-            default:
+        default:
-                break;
+            break;
         }
     }
 
@@ -743,23 +713,23 @@ void ConstraintSolver::generalizeOneType(TypeId ty)
 
         switch (ts.result)
         {
-            case TypeSearcher::Polarity::None:
+        case Polarity::None:
+            asMutable(ty)->reassign(Type{BoundType{upperBound}});
+            break;
+
+        case Polarity::Negative:
+        case Polarity::Mixed:
+            if (get<UnknownType>(upperBound) && ts.count > 1)
+            {
+                asMutable(ty)->reassign(Type{GenericType{tyScope}});
+                function->generics.emplace_back(ty);
+            }
+            else
                 asMutable(ty)->reassign(Type{BoundType{upperBound}});
-                break;
+            break;
 
-            case TypeSearcher::Polarity::Negative:
+        case Polarity::Positive:
-            case TypeSearcher::Polarity::Mixed:
+            if (get<UnknownType>(lowerBound) && ts.count > 1)
-                if (get<UnknownType>(upperBound))
-                {
-                    asMutable(ty)->reassign(Type{GenericType{tyScope}});
-                    function->generics.emplace_back(ty);
-                }
-                else
-                    asMutable(ty)->reassign(Type{BoundType{upperBound}});
-                break;
-
-            case TypeSearcher::Polarity::Positive:
-            if (get<UnknownType>(lowerBound))
             {
                 asMutable(ty)->reassign(Type{GenericType{tyScope}});
                 function->generics.emplace_back(ty);
@@ -767,6 +737,8 @@ void ConstraintSolver::generalizeOneType(TypeId ty)
             else
                 asMutable(ty)->reassign(Type{BoundType{lowerBound}});
             break;
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
     }
 }
@@ -778,7 +750,16 @@ void ConstraintSolver::bind(NotNull<const Constraint> constraint, TypeId ty, Typ
 
     boundTo = follow(boundTo);
     if (get<BlockedType>(ty) && ty == boundTo)
-        return emplace<FreeType>(constraint, ty, constraint->scope, builtinTypes->neverType, builtinTypes->unknownType);
+    {
+        emplace<FreeType>(
+            constraint, ty, constraint->scope, builtinTypes->neverType, builtinTypes->unknownType, Polarity::Mixed
+        ); // FIXME?  Is this the right polarity?
+
+        if (FFlag::LuauNonReentrantGeneralization)
+            trackInteriorFreeType(constraint->scope, ty);
+
+        return;
+    }
 
     shiftReferences(ty, boundTo);
     emplaceType<BoundType>(asMutable(ty), boundTo);
@@ -903,26 +884,25 @@ bool ConstraintSolver::tryDispatch(const GeneralizationConstraint& c, NotNull<co
     else if (get<PendingExpansionType>(generalizedType))
         return block(generalizedType, constraint);
 
-    std::optional<QuantifierResult> generalized;
-
     std::optional<TypeId> generalizedTy = generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, c.sourceType);
-    if (generalizedTy)
+    if (!generalizedTy)
-        generalized = QuantifierResult{*generalizedTy}; // FIXME insertedGenerics and insertedGenericPacks
-    else
         reportError(CodeTooComplex{}, constraint->location);
 
-    if (generalized)
+    if (generalizedTy)
     {
         if (get<BlockedType>(generalizedType))
-            bind(constraint, generalizedType, generalized->result);
+            bind(constraint, generalizedType, *generalizedTy);
         else
-            unify(constraint, generalizedType, generalized->result);
+            unify(constraint, generalizedType, *generalizedTy);
 
-        for (auto [free, gen] : generalized->insertedGenerics.pairings)
+        if (FFlag::LuauDeprecatedAttribute)
-            unify(constraint, free, gen);
+        {
-
+            if (FunctionType* fty = getMutable<FunctionType>(follow(generalizedType)))
-        for (auto [free, gen] : generalized->insertedGenericPacks.pairings)
+            {
-            unify(constraint, free, gen);
+                if (c.hasDeprecatedAttribute)
+                    fty->isDeprecatedFunction = true;
+            }
+        }
     }
     else
     {
@@ -935,13 +915,53 @@ bool ConstraintSolver::tryDispatch(const GeneralizationConstraint& c, NotNull<co
         // We check if this member is initialized and then access it, but
         // clang-tidy doesn't understand this is safe.
         if (constraint->scope->interiorFreeTypes)
+        {
             for (TypeId ty : *constraint->scope->interiorFreeTypes) // NOLINT(bugprone-unchecked-optional-access)
-                generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty, /* avoidSealingTables */ false);
+            {
+                if (FFlag::LuauNonReentrantGeneralization)
+                {
+                    ty = follow(ty);
+                    if (auto freeTy = get<FreeType>(ty))
+                    {
+                        GeneralizationParams<TypeId> params;
+                        params.foundOutsideFunctions = true;
+                        params.useCount = 1;
+                        params.polarity = freeTy->polarity;
+
+                        generalizeType(arena, builtinTypes, constraint->scope, ty, params);
+                    }
+                    else if (get<TableType>(ty))
+                        sealTable(constraint->scope, ty);
+                }
+                else
+                    generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty);
+            }
+        }
+
+        if (FFlag::LuauNonReentrantGeneralization)
+        {
+            if (constraint->scope->interiorFreeTypePacks)
+            {
+                for (TypePackId tp : *constraint->scope->interiorFreeTypePacks) // NOLINT(bugprone-unchecked-optional-access)
+                {
+                    tp = follow(tp);
+                    if (auto freeTp = get<FreeTypePack>(tp))
+                    {
+                        GeneralizationParams<TypePackId> params;
+                        params.foundOutsideFunctions = true;
+                        params.useCount = 1;
+                        params.polarity = freeTp->polarity;
+                        LUAU_ASSERT(isKnown(params.polarity));
+                        generalizeTypePack(arena, builtinTypes, constraint->scope, tp, params);
+                    }
+                }
+            }
+        }
     }
     else
     {
         for (TypeId ty : c.interiorTypes)
-            generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty, /* avoidSealingTables */ false);
+            generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty);
     }
 
 
@@ -1017,8 +1037,8 @@ bool ConstraintSolver::tryDispatch(const IterableConstraint& c, NotNull<const Co
     TypeId nextTy = follow(iterator.head[0]);
     if (get<FreeType>(nextTy))
     {
-        TypeId keyTy = freshType(arena, builtinTypes, constraint->scope);
+        TypeId keyTy = freshType(arena, builtinTypes, constraint->scope, Polarity::Mixed);
-        TypeId valueTy = freshType(arena, builtinTypes, constraint->scope);
+        TypeId valueTy = freshType(arena, builtinTypes, constraint->scope, Polarity::Mixed);
         if (FFlag::LuauTrackInteriorFreeTypesOnScope)
         {
             trackInteriorFreeType(constraint->scope, keyTy);
@@ -1352,15 +1372,29 @@ void ConstraintSolver::fillInDiscriminantTypes(NotNull<const Constraint> constra
         if (!ty)
             continue;
 
-        // If the discriminant type has been transmuted, we need to unblock them.
+        if (FFlag::LuauSearchForRefineableType)
-        if (!isBlocked(*ty))
         {
-            unblock(*ty, constraint->location);
+            if (isBlocked(*ty))
-            continue;
+                // We bind any unused discriminants to the `*no-refine*` type indicating that it can be safely ignored.
-        }
+                emplaceType<BoundType>(asMutable(follow(*ty)), builtinTypes->noRefineType);
 
-        // We bind any unused discriminants to the `*no-refine*` type indicating that it can be safely ignored.
+            // We also need to unconditionally unblock these types, otherwise
-        emplaceType<BoundType>(asMutable(follow(*ty)), builtinTypes->noRefineType);
+            // you end up with funky looking "Blocked on *no-refine*."
+            unblock(*ty, constraint->location);
+        }
+        else
+        {
+
+            // If the discriminant type has been transmuted, we need to unblock them.
+            if (!isBlocked(*ty))
+            {
+                unblock(*ty, constraint->location);
+                continue;
+            }
+
+            // We bind any unused discriminants to the `*no-refine*` type indicating that it can be safely ignored.
+            emplaceType<BoundType>(asMutable(follow(*ty)), builtinTypes->noRefineType);
+        }
     }
 }
 
@@ -1370,9 +1404,17 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
     TypePackId argsPack = follow(c.argsPack);
     TypePackId result = follow(c.result);
 
-    if (isBlocked(fn) || hasUnresolvedConstraints(fn))
+    if (FFlag::DebugLuauGreedyGeneralization)
     {
-        return block(c.fn, constraint);
+        if (isBlocked(fn))
+            return block(c.fn, constraint);
+    }
+    else
+    {
+        if (isBlocked(fn) || hasUnresolvedConstraints(fn))
+        {
+            return block(c.fn, constraint);
+        }
     }
 
     if (get<AnyType>(fn))
@@ -1455,7 +1497,8 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
 
         argsPack = arena->addTypePack(TypePack{std::move(argsHead), argsTail});
         fn = follow(*callMm);
-        emplace<FreeTypePack>(constraint, c.result, constraint->scope);
+        emplace<FreeTypePack>(constraint, c.result, constraint->scope, Polarity::Positive);
+        trackInteriorFreeTypePack(constraint->scope, c.result);
     }
     else
     {
@@ -1472,7 +1515,10 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
         }
 
         if (!usedMagic)
-            emplace<FreeTypePack>(constraint, c.result, constraint->scope);
+        {
+            emplace<FreeTypePack>(constraint, c.result, constraint->scope, Polarity::Positive);
+            trackInteriorFreeTypePack(constraint->scope, c.result);
+        }
     }
 
     fillInDiscriminantTypes(constraint, c.discriminantTypes);
@@ -1493,11 +1539,19 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
     if (status == OverloadResolver::Analysis::Ok)
         overloadToUse = overload;
 
-    TypeId inferredTy = arena->addType(FunctionType{TypeLevel{}, constraint->scope.get(), argsPack, c.result});
+    TypeId inferredTy = arena->addType(FunctionType{TypeLevel{}, argsPack, c.result});
     Unifier2 u2{NotNull{arena}, builtinTypes, constraint->scope, NotNull{&iceReporter}};
 
     const bool occursCheckPassed = u2.unify(overloadToUse, inferredTy);
 
+    if (FFlag::LuauNonReentrantGeneralization)
+    {
+        for (TypeId freeTy : u2.newFreshTypes)
+            trackInteriorFreeType(constraint->scope, freeTy);
+        for (TypePackId freeTp : u2.newFreshTypePacks)
+            trackInteriorFreeTypePack(constraint->scope, freeTp);
+    }
+
     if (!u2.genericSubstitutions.empty() || !u2.genericPackSubstitutions.empty())
     {
         std::optional<TypePackId> subst = instantiate2(arena, std::move(u2.genericSubstitutions), std::move(u2.genericPackSubstitutions), result);
@@ -1528,6 +1582,11 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
     queuer.traverse(overloadToUse);
     queuer.traverse(inferredTy);
 
+    // This can potentially contain free types if the return type of
+    // `inferredTy` is never unified elsewhere.
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope && FFlag::LuauTrackInferredFunctionTypeFromCall)
+        trackInteriorFreeType(constraint->scope, inferredTy);
+
     unblock(c.result, constraint->location);
 
     return true;
@@ -1541,6 +1600,43 @@ static AstExpr* unwrapGroup(AstExpr* expr)
     return expr;
 }
 
+struct ContainsGenerics : public TypeOnceVisitor
+{
+    DenseHashSet<const void*> generics{nullptr};
+
+    bool found = false;
+
+    bool visit(TypeId ty) override
+    {
+        return !found;
+    }
+
+    bool visit(TypeId ty, const GenericType&) override
+    {
+        found |= generics.contains(ty);
+        return true;
+    }
+
+    bool visit(TypeId ty, const TypeFunctionInstanceType&) override
+    {
+        return !found;
+    }
+
+    bool visit(TypePackId tp, const GenericTypePack&) override
+    {
+        found |= generics.contains(tp);
+        return !found;
+    }
+
+    bool hasGeneric(TypeId ty)
+    {
+        traverse(ty);
+        auto ret = found;
+        found = false;
+        return ret;
+    }
+};
+
 bool ConstraintSolver::tryDispatch(const FunctionCheckConstraint& c, NotNull<const Constraint> constraint)
 {
     TypeId fn = follow(c.fn);
@@ -1583,36 +1679,49 @@ bool ConstraintSolver::tryDispatch(const FunctionCheckConstraint& c, NotNull<con
     DenseHashMap<TypeId, TypeId> replacements{nullptr};
     DenseHashMap<TypePackId, TypePackId> replacementPacks{nullptr};
 
+    ContainsGenerics containsGenerics;
+
     for (auto generic : ftv->generics)
+    {
         replacements[generic] = builtinTypes->unknownType;
+        if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
+            containsGenerics.generics.insert(generic);
+    }
 
     for (auto genericPack : ftv->genericPacks)
+    {
         replacementPacks[genericPack] = builtinTypes->unknownTypePack;
+        if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
+            containsGenerics.generics.insert(genericPack);
+    }
 
     // If the type of the function has generics, we don't actually want to push any of the generics themselves
     // into the argument types as expected types because this creates an unnecessary loop. Instead, we want to
     // replace these types with `unknown` (and `...unknown`) to keep any structure but not create the cycle.
-    if (!replacements.empty() || !replacementPacks.empty())
+    if (!FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
     {
-        Replacer replacer{arena, std::move(replacements), std::move(replacementPacks)};
+        if (!replacements.empty() || !replacementPacks.empty())
-
-        std::optional<TypeId> res = replacer.substitute(fn);
-        if (res)
         {
-            if (*res != fn)
+            Replacer replacer{arena, std::move(replacements), std::move(replacementPacks)};
+
+            std::optional<TypeId> res = replacer.substitute(fn);
+            if (res)
             {
-                FunctionType* ftvMut = getMutable<FunctionType>(*res);
+                if (*res != fn)
-                LUAU_ASSERT(ftvMut);
+                {
-                ftvMut->generics.clear();
+                    FunctionType* ftvMut = getMutable<FunctionType>(*res);
-                ftvMut->genericPacks.clear();
+                    LUAU_ASSERT(ftvMut);
+                    ftvMut->generics.clear();
+                    ftvMut->genericPacks.clear();
+                }
+
+                fn = *res;
+                ftv = get<FunctionType>(*res);
+                LUAU_ASSERT(ftv);
+
+                // we've potentially copied type functions here, so we need to reproduce their reduce constraint.
+                reproduceConstraints(constraint->scope, constraint->location, replacer);
             }
-
-            fn = *res;
-            ftv = get<FunctionType>(*res);
-            LUAU_ASSERT(ftv);
-
-            // we've potentially copied type functions here, so we need to reproduce their reduce constraint.
-            reproduceConstraints(constraint->scope, constraint->location, replacer);
         }
     }
 
@@ -1631,6 +1740,10 @@ bool ConstraintSolver::tryDispatch(const FunctionCheckConstraint& c, NotNull<con
 
         (*c.astExpectedTypes)[expr] = expectedArgTy;
 
+        // Generic types are skipped over entirely, for now.
+        if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes && containsGenerics.hasGeneric(expectedArgTy))
+            continue;
+
         const FunctionType* expectedLambdaTy = get<FunctionType>(expectedArgTy);
         const FunctionType* lambdaTy = get<FunctionType>(actualArgTy);
         const AstExprFunction* lambdaExpr = expr->as<AstExprFunction>();
@@ -1658,8 +1771,11 @@ bool ConstraintSolver::tryDispatch(const FunctionCheckConstraint& c, NotNull<con
         else if (expr->is<AstExprTable>())
         {
             Unifier2 u2{arena, builtinTypes, constraint->scope, NotNull{&iceReporter}};
+            Subtyping sp{builtinTypes, arena, simplifier, normalizer, typeFunctionRuntime, NotNull{&iceReporter}};
             std::vector<TypeId> toBlock;
-            (void)matchLiteralType(c.astTypes, c.astExpectedTypes, builtinTypes, arena, NotNull{&u2}, expectedArgTy, actualArgTy, expr, toBlock);
+            (void)matchLiteralType(
+                c.astTypes, c.astExpectedTypes, builtinTypes, arena, NotNull{&u2}, NotNull{&sp}, expectedArgTy, actualArgTy, expr, toBlock
+            );
             LUAU_ASSERT(toBlock.empty());
         }
     }
@@ -1683,8 +1799,9 @@ bool ConstraintSolver::tryDispatch(const TableCheckConstraint& c, NotNull<const
         return false;
 
     Unifier2 u2{arena, builtinTypes, constraint->scope, NotNull{&iceReporter}};
+    Subtyping sp{builtinTypes, arena, simplifier, normalizer, typeFunctionRuntime, NotNull{&iceReporter}};
     std::vector<TypeId> toBlock;
-    (void)matchLiteralType(c.astTypes, c.astExpectedTypes, builtinTypes, arena, NotNull{&u2}, c.expectedType, c.exprType, c.table, toBlock);
+    (void)matchLiteralType(c.astTypes, c.astExpectedTypes, builtinTypes, arena, NotNull{&u2}, NotNull{&sp}, c.expectedType, c.exprType, c.table, toBlock);
     LUAU_ASSERT(toBlock.empty());
     return true;
 }
@@ -1731,8 +1848,16 @@ bool ConstraintSolver::tryDispatch(const HasPropConstraint& c, NotNull<const Con
     LUAU_ASSERT(get<BlockedType>(resultType));
     LUAU_ASSERT(canMutate(resultType, constraint));
 
-    if (isBlocked(subjectType) || get<PendingExpansionType>(subjectType) || get<TypeFunctionInstanceType>(subjectType))
+    if (FFlag::LuauHasPropProperBlock)
-        return block(subjectType, constraint);
+    {
+        if (isBlocked(subjectType))
+            return block(subjectType, constraint);
+    }
+    else
+    {
+        if (isBlocked(subjectType) || get<PendingExpansionType>(subjectType) || get<TypeFunctionInstanceType>(subjectType))
+            return block(subjectType, constraint);
+    }
 
     if (const TableType* subjectTable = getTableType(subjectType))
     {
@@ -1794,7 +1919,7 @@ bool ConstraintSolver::tryDispatchHasIndexer(
         else if (auto mt = get<MetatableType>(follow(ft->upperBound)))
             return tryDispatchHasIndexer(recursionDepth, constraint, mt->table, indexType, resultType, seen);
 
-        FreeType freeResult{ft->scope, builtinTypes->neverType, builtinTypes->unknownType};
+        FreeType freeResult{ft->scope, builtinTypes->neverType, builtinTypes->unknownType, Polarity::Mixed};
         emplace<FreeType>(constraint, resultType, freeResult);
 
         TypeId upperBound =
@@ -1817,8 +1942,10 @@ bool ConstraintSolver::tryDispatchHasIndexer(
         {
             // FIXME this is greedy.
 
-            FreeType freeResult{tt->scope, builtinTypes->neverType, builtinTypes->unknownType};
+            FreeType freeResult{tt->scope, builtinTypes->neverType, builtinTypes->unknownType, Polarity::Mixed};
             emplace<FreeType>(constraint, resultType, freeResult);
+            if (FFlag::LuauNonReentrantGeneralization)
+                trackInteriorFreeType(constraint->scope, resultType);
 
             tt->indexer = TableIndexer{indexType, resultType};
             return true;
@@ -2040,11 +2167,7 @@ bool ConstraintSolver::tryDispatch(const AssignPropConstraint& c, NotNull<const
     if (maybeTy)
     {
         TypeId propTy = *maybeTy;
-        bind(
+        bind(constraint, c.propType, isIndex ? arena->addType(UnionType{{propTy, builtinTypes->nilType}}) : propTy);
-            constraint,
-            c.propType,
-            isIndex ? arena->addType(UnionType{{propTy, builtinTypes->nilType}}) : propTy
-        );
         unify(constraint, rhsType, propTy);
         return true;
     }
@@ -2138,11 +2261,7 @@ bool ConstraintSolver::tryDispatch(const AssignIndexConstraint& c, NotNull<const
         {
             unify(constraint, indexType, lhsTable->indexer->indexType);
             unify(constraint, rhsType, lhsTable->indexer->indexResultType);
-            bind(
+            bind(constraint, c.propType, arena->addType(UnionType{{lhsTable->indexer->indexResultType, builtinTypes->nilType}}));
-                constraint,
-                c.propType,
-                arena->addType(UnionType{{lhsTable->indexer->indexResultType, builtinTypes->nilType}})
-            );
             return true;
         }
 
@@ -2191,11 +2310,7 @@ bool ConstraintSolver::tryDispatch(const AssignIndexConstraint& c, NotNull<const
             {
                 unify(constraint, indexType, lhsClass->indexer->indexType);
                 unify(constraint, rhsType, lhsClass->indexer->indexResultType);
-                bind(
+                bind(constraint, c.propType, arena->addType(UnionType{{lhsClass->indexer->indexResultType, builtinTypes->nilType}}));
-                    constraint,
-                    c.propType,
-                    arena->addType(UnionType{{lhsClass->indexer->indexResultType, builtinTypes->nilType}})
-                );
                 return true;
             }
 
@@ -2289,7 +2404,7 @@ bool ConstraintSolver::tryDispatch(const UnpackConstraint& c, NotNull<const Cons
                 // is only blocked on itself. This doesn't actually
                 // constitute any meaningful constraint, so we replace it
                 // with a free type.
-                TypeId f = freshType(arena, builtinTypes, constraint->scope);
+                TypeId f = freshType(arena, builtinTypes, constraint->scope, Polarity::Positive); // FIXME?  Is this the right polarity?
                 if (FFlag::LuauTrackInteriorFreeTypesOnScope)
                     trackInteriorFreeType(constraint->scope, f);
                 shiftReferences(resultTy, f);
@@ -2338,11 +2453,18 @@ bool ConstraintSolver::tryDispatch(const ReduceConstraint& c, NotNull<const Cons
     for (TypePackId r : result.reducedPacks)
         unblock(r, constraint->location);
 
+    if (FFlag::LuauNewTypeFunReductionChecks2)
+    {
+        for (TypeId ity : result.irreducibleTypes)
+            uninhabitedTypeFunctions.insert(ity);
+    }
+
     bool reductionFinished = result.blockedTypes.empty() && result.blockedPacks.empty();
 
     ty = follow(ty);
+
     // If we couldn't reduce this type function, stick it in the set!
-    if (get<TypeFunctionInstanceType>(ty))
+    if (get<TypeFunctionInstanceType>(ty) && (!FFlag::LuauNewTypeFunReductionChecks2 || !result.irreducibleTypes.find(ty)))
         typeFunctionsToFinalize[ty] = constraint;
 
     if (force || reductionFinished)
@@ -2425,8 +2547,8 @@ bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const Iterabl
 
     if (get<FreeType>(iteratorTy))
     {
-        TypeId keyTy = freshType(arena, builtinTypes, constraint->scope);
+        TypeId keyTy = freshType(arena, builtinTypes, constraint->scope, Polarity::Mixed);
-        TypeId valueTy = freshType(arena, builtinTypes, constraint->scope);
+        TypeId valueTy = freshType(arena, builtinTypes, constraint->scope, Polarity::Mixed);
         if (FFlag::LuauTrackInteriorFreeTypesOnScope)
         {
             trackInteriorFreeType(constraint->scope, keyTy);
@@ -2687,7 +2809,7 @@ TablePropLookupResult ConstraintSolver::lookupTableProp(
 
         if (ttv->state == TableState::Free)
         {
-            TypeId result = freshType(arena, builtinTypes, ttv->scope);
+            TypeId result = freshType(arena, builtinTypes, ttv->scope, Polarity::Mixed);
             if (FFlag::LuauTrackInteriorFreeTypesOnScope)
                 trackInteriorFreeType(ttv->scope, result);
             switch (context)
@@ -2801,7 +2923,7 @@ TablePropLookupResult ConstraintSolver::lookupTableProp(
 
         TableType* tt = getMutable<TableType>(newUpperBound);
         LUAU_ASSERT(tt);
-        TypeId propType = freshType(arena, builtinTypes, scope);
+        TypeId propType = freshType(arena, builtinTypes, scope, Polarity::Mixed);
 
         if (FFlag::LuauTrackInteriorFreeTypesOnScope)
             trackInteriorFreeType(scope, propType);
@@ -3262,7 +3384,7 @@ void ConstraintSolver::shiftReferences(TypeId source, TypeId target)
     }
 }
 
-std::optional<TypeId> ConstraintSolver::generalizeFreeType(NotNull<Scope> scope, TypeId type, bool avoidSealingTables)
+std::optional<TypeId> ConstraintSolver::generalizeFreeType(NotNull<Scope> scope, TypeId type)
 {
     TypeId t = follow(type);
     if (get<FreeType>(t))
@@ -3277,7 +3399,7 @@ std::optional<TypeId> ConstraintSolver::generalizeFreeType(NotNull<Scope> scope,
         // that until all constraint generation is complete.
     }
 
-    return generalize(NotNull{arena}, builtinTypes, scope, generalizedTypes, type, avoidSealingTables);
+    return generalize(NotNull{arena}, builtinTypes, scope, generalizedTypes, type);
 }
 
 bool ConstraintSolver::hasUnresolvedConstraints(TypeId ty)

Analysis/src/DataFlowGraph.cpp

@@ -13,32 +13,22 @@
 
 LUAU_FASTFLAG(DebugLuauFreezeArena)
 LUAU_FASTFLAG(LuauSolverV2)
-
+LUAU_FASTFLAGVARIABLE(LuauPreprocessTypestatedArgument)
+LUAU_FASTFLAGVARIABLE(LuauDfgScopeStackTrueReset)
+LUAU_FASTFLAGVARIABLE(LuauDfgScopeStackNotNull)
 namespace Luau
 {
 
 bool doesCallError(const AstExprCall* call); // TypeInfer.cpp
 
-struct ReferencedDefFinder : public AstVisitor
-{
-    bool visit(AstExprLocal* local) override
-    {
-        referencedLocalDefs.push_back(local->local);
-        return true;
-    }
-    // ast defs is just a mapping from expr -> def in general
-    // will get built up by the dfg builder
-
-    // localDefs, we need to copy over
-    std::vector<AstLocal*> referencedLocalDefs;
-};
-
 struct PushScope
 {
     ScopeStack& stack;
+    size_t previousSize;
 
     PushScope(ScopeStack& stack, DfgScope* scope)
         : stack(stack)
+        , previousSize(stack.size())
     {
         // `scope` should never be `nullptr` here.
         LUAU_ASSERT(scope);
@@ -47,7 +37,18 @@ struct PushScope
 
     ~PushScope()
     {
-        stack.pop_back();
+        if (FFlag::LuauDfgScopeStackTrueReset)
+        {
+            // If somehow this stack has _shrunk_ to be smaller than we expect,
+            // something very strange has happened.
+            LUAU_ASSERT(stack.size() > previousSize);
+            while (stack.size() > previousSize)
+                stack.pop_back();
+        }
+        else
+        {
+            stack.pop_back();
+        }
     }
 };
 
@@ -82,12 +83,6 @@ std::optional<DefId> DataFlowGraph::getDefOptional(const AstExpr* expr) const
     return NotNull{*def};
 }
 
-std::optional<DefId> DataFlowGraph::getRValueDefForCompoundAssign(const AstExpr* expr) const
-{
-    auto def = compoundAssignDefs.find(expr);
-    return def ? std::optional<DefId>(*def) : std::nullopt;
-}
-
 DefId DataFlowGraph::getDef(const AstLocal* local) const
 {
     auto def = localDefs.find(local);
@@ -201,7 +196,15 @@ DataFlowGraph DataFlowGraphBuilder::build(
 
     DataFlowGraphBuilder builder(defArena, keyArena);
     builder.handle = handle;
-    DfgScope* moduleScope = builder.makeChildScope();
+
+    DfgScope* moduleScope;
+    // We're not explicitly calling makeChildScope here because that function relies on currentScope
+    // which guarantees that the scope being returned is NotNull
+    // This means that while the scope stack is empty, we'll have to manually initialize the global scope
+    if (FFlag::LuauDfgScopeStackNotNull)
+        moduleScope = builder.scopes.emplace_back(new DfgScope{nullptr, DfgScope::ScopeType::Linear}).get();
+    else
+        moduleScope = builder.makeChildScope();
     PushScope ps{builder.scopeStack, moduleScope};
     builder.visitBlockWithoutChildScope(block);
     builder.resolveCaptures();
@@ -233,7 +236,13 @@ void DataFlowGraphBuilder::resolveCaptures()
     }
 }
 
-DfgScope* DataFlowGraphBuilder::currentScope()
+NotNull<DfgScope> DataFlowGraphBuilder::currentScope()
+{
+    LUAU_ASSERT(!scopeStack.empty());
+    return NotNull{scopeStack.back()};
+}
+
+DfgScope* DataFlowGraphBuilder::currentScope_DEPRECATED()
 {
     if (scopeStack.empty())
         return nullptr; // nullptr is the root DFG scope.
@@ -242,7 +251,10 @@ DfgScope* DataFlowGraphBuilder::currentScope()
 
 DfgScope* DataFlowGraphBuilder::makeChildScope(DfgScope::ScopeType scopeType)
 {
-    return scopes.emplace_back(new DfgScope{currentScope(), scopeType}).get();
+    if (FFlag::LuauDfgScopeStackNotNull)
+        return scopes.emplace_back(new DfgScope{currentScope(), scopeType}).get();
+    else
+        return scopes.emplace_back(new DfgScope{currentScope_DEPRECATED(), scopeType}).get();
 }
 
 void DataFlowGraphBuilder::join(DfgScope* p, DfgScope* a, DfgScope* b)
@@ -317,9 +329,9 @@ void DataFlowGraphBuilder::joinProps(DfgScope* result, const DfgScope& a, const
     }
 }
 
-DefId DataFlowGraphBuilder::lookup(Symbol symbol)
+DefId DataFlowGraphBuilder::lookup(Symbol symbol, Location location)
 {
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
 
     // true if any of the considered scopes are a loop.
     bool outsideLoopScope = false;
@@ -344,15 +356,15 @@ DefId DataFlowGraphBuilder::lookup(Symbol symbol)
         }
     }
 
-    DefId result = defArena->freshCell();
+    DefId result = defArena->freshCell(symbol, location);
     scope->bindings[symbol] = result;
     captures[symbol].allVersions.push_back(result);
     return result;
 }
 
-DefId DataFlowGraphBuilder::lookup(DefId def, const std::string& key)
+DefId DataFlowGraphBuilder::lookup(DefId def, const std::string& key, Location location)
 {
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
     for (DfgScope* current = scope; current; current = current->parent)
     {
         if (auto props = current->props.find(def))
@@ -362,7 +374,7 @@ DefId DataFlowGraphBuilder::lookup(DefId def, const std::string& key)
         }
         else if (auto phi = get<Phi>(def); phi && phi->operands.empty()) // Unresolved phi nodes
         {
-            DefId result = defArena->freshCell();
+            DefId result = defArena->freshCell(def->name, location);
             scope->props[def][key] = result;
             return result;
         }
@@ -372,7 +384,7 @@ DefId DataFlowGraphBuilder::lookup(DefId def, const std::string& key)
     {
         std::vector<DefId> defs;
         for (DefId operand : phi->operands)
-            defs.push_back(lookup(operand, key));
+            defs.push_back(lookup(operand, key, location));
 
         DefId result = defArena->phi(defs);
         scope->props[def][key] = result;
@@ -380,7 +392,7 @@ DefId DataFlowGraphBuilder::lookup(DefId def, const std::string& key)
     }
     else if (get<Cell>(def))
     {
-        DefId result = defArena->freshCell();
+        DefId result = defArena->freshCell(def->name, location);
         scope->props[def][key] = result;
         return result;
     }
@@ -398,7 +410,10 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatBlock* b)
         cf = visitBlockWithoutChildScope(b);
     }
 
-    currentScope()->inherit(child);
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->inherit(child);
+    else
+        currentScope_DEPRECATED()->inherit(child);
     return cf;
 }
 
@@ -483,7 +498,7 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatIf* i)
         elsecf = visit(i->elsebody);
     }
 
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
     if (thencf != ControlFlow::None && elsecf == ControlFlow::None)
         join(scope, scope, elseScope);
     else if (thencf == ControlFlow::None && elsecf != ControlFlow::None)
@@ -510,7 +525,10 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatWhile* w)
         visit(w->body);
     }
 
-    currentScope()->inherit(whileScope);
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->inherit(whileScope);
+    else
+        currentScope_DEPRECATED()->inherit(whileScope);
 
     return ControlFlow::None;
 }
@@ -526,7 +544,10 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatRepeat* r)
         visitExpr(r->condition);
     }
 
-    currentScope()->inherit(repeatScope);
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->inherit(repeatScope);
+    else
+        currentScope_DEPRECATED()->inherit(repeatScope);
 
     return ControlFlow::None;
 }
@@ -575,7 +596,7 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatLocal* l)
         // We need to create a new def to intentionally avoid alias tracking, but we'd like to
         // make sure that the non-aliased defs are also marked as a subscript for refinements.
         bool subscripted = i < defs.size() && containsSubscriptedDefinition(defs[i]);
-        DefId def = defArena->freshCell(subscripted);
+        DefId def = defArena->freshCell(local, local->location, subscripted);
         if (i < l->values.size)
         {
             AstExpr* e = l->values.data[i];
@@ -585,7 +606,10 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatLocal* l)
             }
         }
         graph.localDefs[local] = def;
-        currentScope()->bindings[local] = def;
+        if (FFlag::LuauDfgScopeStackNotNull)
+            currentScope()->bindings[local] = def;
+        else
+            currentScope_DEPRECATED()->bindings[local] = def;
         captures[local].allVersions.push_back(def);
     }
 
@@ -607,16 +631,22 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatFor* f)
         if (f->var->annotation)
             visitType(f->var->annotation);
 
-        DefId def = defArena->freshCell();
+        DefId def = defArena->freshCell(f->var, f->var->location);
         graph.localDefs[f->var] = def;
-        currentScope()->bindings[f->var] = def;
+        if (FFlag::LuauDfgScopeStackNotNull)
+            currentScope()->bindings[f->var] = def;
+        else
+            currentScope_DEPRECATED()->bindings[f->var] = def;
         captures[f->var].allVersions.push_back(def);
 
         // TODO(controlflow): entry point has a back edge from exit point
         visit(f->body);
     }
 
-    currentScope()->inherit(forScope);
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->inherit(forScope);
+    else
+        currentScope_DEPRECATED()->inherit(forScope);
 
     return ControlFlow::None;
 }
@@ -633,9 +663,12 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatForIn* f)
             if (local->annotation)
                 visitType(local->annotation);
 
-            DefId def = defArena->freshCell();
+            DefId def = defArena->freshCell(local, local->location);
             graph.localDefs[local] = def;
-            currentScope()->bindings[local] = def;
+            if (FFlag::LuauDfgScopeStackNotNull)
+                currentScope()->bindings[local] = def;
+            else
+                currentScope_DEPRECATED()->bindings[local] = def;
             captures[local].allVersions.push_back(def);
         }
 
@@ -646,8 +679,10 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatForIn* f)
 
         visit(f->body);
     }
-
+    if (FFlag::LuauDfgScopeStackNotNull)
-    currentScope()->inherit(forScope);
+        currentScope()->inherit(forScope);
+    else
+        currentScope_DEPRECATED()->inherit(forScope);
 
     return ControlFlow::None;
 }
@@ -662,7 +697,7 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatAssign* a)
     for (size_t i = 0; i < a->vars.size; ++i)
     {
         AstExpr* v = a->vars.data[i];
-        visitLValue(v, i < defs.size() ? defs[i] : defArena->freshCell());
+        visitLValue(v, i < defs.size() ? defs[i] : defArena->freshCell(Symbol{}, v->location));
     }
 
     return ControlFlow::None;
@@ -688,7 +723,7 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatFunction* f)
     //
     // which is evidence that references to variables must be a phi node of all possible definitions,
     // but for bug compatibility, we'll assume the same thing here.
-    visitLValue(f->name, defArena->freshCell());
+    visitLValue(f->name, defArena->freshCell(Symbol{}, f->name->location));
     visitExpr(f->func);
 
     if (auto local = f->name->as<AstExprLocal>())
@@ -708,9 +743,12 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatFunction* f)
 
 ControlFlow DataFlowGraphBuilder::visit(AstStatLocalFunction* l)
 {
-    DefId def = defArena->freshCell();
+    DefId def = defArena->freshCell(l->name, l->location);
     graph.localDefs[l->name] = def;
-    currentScope()->bindings[l->name] = def;
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->bindings[l->name] = def;
+    else
+        currentScope_DEPRECATED()->bindings[l->name] = def;
     captures[l->name].allVersions.push_back(def);
     visitExpr(l->func);
 
@@ -741,9 +779,12 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatTypeFunction* f)
 
 ControlFlow DataFlowGraphBuilder::visit(AstStatDeclareGlobal* d)
 {
-    DefId def = defArena->freshCell();
+    DefId def = defArena->freshCell(d->name, d->nameLocation);
     graph.declaredDefs[d] = def;
-    currentScope()->bindings[d->name] = def;
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->bindings[d->name] = def;
+    else
+        currentScope_DEPRECATED()->bindings[d->name] = def;
     captures[d->name].allVersions.push_back(def);
 
     visitType(d->type);
@@ -753,9 +794,12 @@ ControlFlow DataFlowGraphBuilder::visit(AstStatDeclareGlobal* d)
 
 ControlFlow DataFlowGraphBuilder::visit(AstStatDeclareFunction* d)
 {
-    DefId def = defArena->freshCell();
+    DefId def = defArena->freshCell(d->name, d->nameLocation);
     graph.declaredDefs[d] = def;
-    currentScope()->bindings[d->name] = def;
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->bindings[d->name] = def;
+    else
+        currentScope_DEPRECATED()->bindings[d->name] = def;
     captures[d->name].allVersions.push_back(def);
 
     DfgScope* unreachable = makeChildScope();
@@ -810,19 +854,19 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExpr* e)
         if (auto g = e->as<AstExprGroup>())
             return visitExpr(g);
         else if (auto c = e->as<AstExprConstantNil>())
-            return {defArena->freshCell(), nullptr}; // ok
+            return {defArena->freshCell(Symbol{}, c->location), nullptr}; // ok
         else if (auto c = e->as<AstExprConstantBool>())
-            return {defArena->freshCell(), nullptr}; // ok
+            return {defArena->freshCell(Symbol{}, c->location), nullptr}; // ok
         else if (auto c = e->as<AstExprConstantNumber>())
-            return {defArena->freshCell(), nullptr}; // ok
+            return {defArena->freshCell(Symbol{}, c->location), nullptr}; // ok
         else if (auto c = e->as<AstExprConstantString>())
-            return {defArena->freshCell(), nullptr}; // ok
+            return {defArena->freshCell(Symbol{}, c->location), nullptr}; // ok
         else if (auto l = e->as<AstExprLocal>())
             return visitExpr(l);
         else if (auto g = e->as<AstExprGlobal>())
             return visitExpr(g);
         else if (auto v = e->as<AstExprVarargs>())
-            return {defArena->freshCell(), nullptr}; // ok
+            return {defArena->freshCell(Symbol{}, v->location), nullptr}; // ok
         else if (auto c = e->as<AstExprCall>())
             return visitExpr(c);
         else if (auto i = e->as<AstExprIndexName>())
@@ -863,14 +907,14 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprGroup* group)
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprLocal* l)
 {
-    DefId def = lookup(l->local);
+    DefId def = lookup(l->local, l->local->location);
     const RefinementKey* key = keyArena->leaf(def);
     return {def, key};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprGlobal* g)
 {
-    DefId def = lookup(g->name);
+    DefId def = lookup(g->name, g->location);
     return {def, keyArena->leaf(def)};
 }
 
@@ -878,6 +922,12 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprCall* c)
 {
     visitExpr(c->func);
 
+    if (FFlag::LuauPreprocessTypestatedArgument)
+    {
+        for (AstExpr* arg : c->args)
+            visitExpr(arg);
+    }
+
     if (shouldTypestateForFirstArgument(*c) && c->args.size > 1 && isLValue(*c->args.begin()))
     {
         AstExpr* firstArg = *c->args.begin();
@@ -908,11 +958,23 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprCall* c)
         visitLValue(firstArg, def);
     }
 
-    for (AstExpr* arg : c->args)
+    if (!FFlag::LuauPreprocessTypestatedArgument)
-        visitExpr(arg);
+    {
+        for (AstExpr* arg : c->args)
+            visitExpr(arg);
+    }
 
-    // calls should be treated as subscripted.
+    // We treat function calls as "subscripted" as they could potentially
-    return {defArena->freshCell(/* subscripted */ true), nullptr};
+    // return a subscripted value, consider:
+    //
+    //  local function foo(tbl: {[string]: woof)
+    //      return tbl["foobarbaz"]
+    //  end
+    //
+    //  local v = foo({})
+    //
+    // We want to consider `v` to be subscripted here.
+    return {defArena->freshCell(Symbol{}, c->location, /*subscripted=*/true)};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprIndexName* i)
@@ -920,7 +982,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprIndexName* i)
     auto [parentDef, parentKey] = visitExpr(i->expr);
     std::string index = i->index.value;
 
-    DefId def = lookup(parentDef, index);
+    DefId def = lookup(parentDef, index, i->location);
     return {def, keyArena->node(parentKey, def, index)};
 }
 
@@ -933,11 +995,11 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprIndexExpr* i)
     {
         std::string index{string->value.data, string->value.size};
 
-        DefId def = lookup(parentDef, index);
+        DefId def = lookup(parentDef, index, i->location);
         return {def, keyArena->node(parentKey, def, index)};
     }
 
-    return {defArena->freshCell(/* subscripted= */ true), nullptr};
+    return {defArena->freshCell(Symbol{}, i->location, /* subscripted= */ true), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprFunction* f)
@@ -950,7 +1012,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprFunction* f)
         // There's no syntax for `self` to have an annotation if using `function t:m()`
         LUAU_ASSERT(!self->annotation);
 
-        DefId def = defArena->freshCell();
+        DefId def = defArena->freshCell(f->debugname, f->location);
         graph.localDefs[self] = def;
         signatureScope->bindings[self] = def;
         captures[self].allVersions.push_back(def);
@@ -961,7 +1023,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprFunction* f)
         if (param->annotation)
             visitType(param->annotation);
 
-        DefId def = defArena->freshCell();
+        DefId def = defArena->freshCell(param, param->location);
         graph.localDefs[param] = def;
         signatureScope->bindings[param] = def;
         captures[param].allVersions.push_back(def);
@@ -983,13 +1045,16 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprFunction* f)
     // g() --> 5
     visit(f->body);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(f->debugname, f->location), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprTable* t)
 {
-    DefId tableCell = defArena->freshCell();
+    DefId tableCell = defArena->freshCell(Symbol{}, t->location);
-    currentScope()->props[tableCell] = {};
+    if (FFlag::LuauDfgScopeStackNotNull)
+        currentScope()->props[tableCell] = {};
+    else
+        currentScope_DEPRECATED()->props[tableCell] = {};
     for (AstExprTable::Item item : t->items)
     {
         DataFlowResult result = visitExpr(item.value);
@@ -997,7 +1062,12 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprTable* t)
         {
             visitExpr(item.key);
             if (auto string = item.key->as<AstExprConstantString>())
-                currentScope()->props[tableCell][string->value.data] = result.def;
+            {
+                if (FFlag::LuauDfgScopeStackNotNull)
+                    currentScope()->props[tableCell][string->value.data] = result.def;
+                else
+                    currentScope_DEPRECATED()->props[tableCell][string->value.data] = result.def;
+            }
         }
     }
 
@@ -1008,7 +1078,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprUnary* u)
 {
     visitExpr(u->expr);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(Symbol{}, u->location), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprBinary* b)
@@ -1016,7 +1086,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprBinary* b)
     visitExpr(b->left);
     visitExpr(b->right);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(Symbol{}, b->location), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprTypeAssertion* t)
@@ -1033,7 +1103,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprIfElse* i)
     visitExpr(i->trueExpr);
     visitExpr(i->falseExpr);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(Symbol{}, i->location), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprInterpString* i)
@@ -1041,7 +1111,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprInterpString* i)
     for (AstExpr* e : i->expressions)
         visitExpr(e);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(Symbol{}, i->location), nullptr};
 }
 
 DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprError* error)
@@ -1052,7 +1122,7 @@ DataFlowResult DataFlowGraphBuilder::visitExpr(AstExprError* error)
     for (AstExpr* e : error->expressions)
         visitExpr(e);
 
-    return {defArena->freshCell(), nullptr};
+    return {defArena->freshCell(Symbol{}, error->location), nullptr};
 }
 
 void DataFlowGraphBuilder::visitLValue(AstExpr* e, DefId incomingDef)
@@ -1078,12 +1148,12 @@ void DataFlowGraphBuilder::visitLValue(AstExpr* e, DefId incomingDef)
 
 DefId DataFlowGraphBuilder::visitLValue(AstExprLocal* l, DefId incomingDef)
 {
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
 
     // In order to avoid alias tracking, we need to clip the reference to the parent def.
     if (scope->canUpdateDefinition(l->local))
     {
-        DefId updated = defArena->freshCell(containsSubscriptedDefinition(incomingDef));
+        DefId updated = defArena->freshCell(l->local, l->location, containsSubscriptedDefinition(incomingDef));
         scope->bindings[l->local] = updated;
         captures[l->local].allVersions.push_back(updated);
         return updated;
@@ -1094,12 +1164,12 @@ DefId DataFlowGraphBuilder::visitLValue(AstExprLocal* l, DefId incomingDef)
 
 DefId DataFlowGraphBuilder::visitLValue(AstExprGlobal* g, DefId incomingDef)
 {
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
 
     // In order to avoid alias tracking, we need to clip the reference to the parent def.
     if (scope->canUpdateDefinition(g->name))
     {
-        DefId updated = defArena->freshCell(containsSubscriptedDefinition(incomingDef));
+        DefId updated = defArena->freshCell(g->name, g->location, containsSubscriptedDefinition(incomingDef));
         scope->bindings[g->name] = updated;
         captures[g->name].allVersions.push_back(updated);
         return updated;
@@ -1112,10 +1182,10 @@ DefId DataFlowGraphBuilder::visitLValue(AstExprIndexName* i, DefId incomingDef)
 {
     DefId parentDef = visitExpr(i->expr).def;
 
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
     if (scope->canUpdateDefinition(parentDef, i->index.value))
     {
-        DefId updated = defArena->freshCell(containsSubscriptedDefinition(incomingDef));
+        DefId updated = defArena->freshCell(i->index, i->location, containsSubscriptedDefinition(incomingDef));
         scope->props[parentDef][i->index.value] = updated;
         return updated;
     }
@@ -1128,12 +1198,12 @@ DefId DataFlowGraphBuilder::visitLValue(AstExprIndexExpr* i, DefId incomingDef)
     DefId parentDef = visitExpr(i->expr).def;
     visitExpr(i->index);
 
-    DfgScope* scope = currentScope();
+    DfgScope* scope = FFlag::LuauDfgScopeStackNotNull ? currentScope() : currentScope_DEPRECATED();
     if (auto string = i->index->as<AstExprConstantString>())
     {
         if (scope->canUpdateDefinition(parentDef, string->value.data))
         {
-            DefId updated = defArena->freshCell(containsSubscriptedDefinition(incomingDef));
+            DefId updated = defArena->freshCell(Symbol{}, i->location, containsSubscriptedDefinition(incomingDef));
             scope->props[parentDef][string->value.data] = updated;
             return updated;
         }
@@ -1141,7 +1211,7 @@ DefId DataFlowGraphBuilder::visitLValue(AstExprIndexExpr* i, DefId incomingDef)
             return visitExpr(static_cast<AstExpr*>(i)).def;
     }
     else
-        return defArena->freshCell(/*subscripted=*/true);
+        return defArena->freshCell(Symbol{}, i->location, /*subscripted=*/true);
 }
 
 DefId DataFlowGraphBuilder::visitLValue(AstExprError* error, DefId incomingDef)
@@ -1159,6 +1229,8 @@ void DataFlowGraphBuilder::visitType(AstType* t)
         return visitType(f);
     else if (auto tyof = t->as<AstTypeTypeof>())
         return visitType(tyof);
+    else if (auto o = t->as<AstTypeOptional>())
+        return;
     else if (auto u = t->as<AstTypeUnion>())
         return visitType(u);
     else if (auto i = t->as<AstTypeIntersection>())

Analysis/src/Def.cpp

@@ -36,9 +36,9 @@ void collectOperands(DefId def, std::vector<DefId>* operands)
     }
 }
 
-DefId DefArena::freshCell(bool subscripted)
+DefId DefArena::freshCell(Symbol sym, Location location, bool subscripted)
 {
-    return NotNull{allocator.allocate(Def{Cell{subscripted}})};
+    return NotNull{allocator.allocate(Def{Cell{subscripted}, sym, location})};
 }
 
 DefId DefArena::phi(DefId a, DefId b)

Analysis/src/EmbeddedBuiltinDefinitions.cpp

@@ -1,8 +1,6 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/BuiltinDefinitions.h"
 
-LUAU_FASTFLAGVARIABLE(LuauDebugInfoDefn)
-
 namespace Luau
 {
 
@@ -215,15 +213,6 @@ declare debug: {
 
 )BUILTIN_SRC";
 
-static const std::string kBuiltinDefinitionDebugSrc_DEPRECATED = R"BUILTIN_SRC(
-
-declare debug: {
-    info: (<R...>(thread: thread, level: number, options: string) -> R...) & (<R...>(level: number, options: string) -> R...) & (<A..., R1..., R2...>(func: (A...) -> R1..., options: string) -> R2...),
-    traceback: ((message: string?, level: number?) -> string) & ((thread: thread, message: string?, level: number?) -> string),
-}
-
-)BUILTIN_SRC";
-
 static const std::string kBuiltinDefinitionUtf8Src = R"BUILTIN_SRC(
 
 declare utf8: {
@@ -309,7 +298,7 @@ std::string getBuiltinDefinitionSource()
     result += kBuiltinDefinitionOsSrc;
     result += kBuiltinDefinitionCoroutineSrc;
     result += kBuiltinDefinitionTableSrc;
-    result += FFlag::LuauDebugInfoDefn ? kBuiltinDefinitionDebugSrc : kBuiltinDefinitionDebugSrc_DEPRECATED;
+    result += kBuiltinDefinitionDebugSrc;
     result += kBuiltinDefinitionUtf8Src;
     result += kBuiltinDefinitionBufferSrc;
     result += kBuiltinDefinitionVectorSrc;
@@ -317,4 +306,83 @@ std::string getBuiltinDefinitionSource()
     return result;
 }
 
+// TODO: split into separate tagged unions when the new solver can appropriately handle that.
+static const std::string kBuiltinDefinitionTypesSrc = R"BUILTIN_SRC(
+
+export type type = {
+    tag: "nil" | "unknown" | "never" | "any" | "boolean" | "number" | "string" | "buffer" | "thread" |
+         "singleton" | "negation" | "union" | "intesection" | "table" | "function" | "class" | "generic",
+
+    is: (self: type, arg: string) -> boolean,
+
+    -- for singleton type
+    value: (self: type) -> (string | boolean | nil),
+
+    -- for negation type
+    inner: (self: type) -> type,
+
+    -- for union and intersection types
+    components: (self: type) -> {type},
+
+    -- for table type
+    setproperty: (self: type, key: type, value: type?) -> (),
+    setreadproperty: (self: type, key: type, value: type?) -> (),
+    setwriteproperty: (self: type, key: type, value: type?) -> (),
+    readproperty: (self: type, key: type) -> type?,
+    writeproperty: (self: type, key: type) -> type?,
+    properties: (self: type) -> { [type]: { read: type?, write: type? } },
+    setindexer: (self: type, index: type, result: type) -> (),
+    setreadindexer: (self: type, index: type, result: type) -> (),
+    setwriteindexer: (self: type, index: type, result: type) -> (),
+    indexer: (self: type) -> { index: type, readresult: type, writeresult: type }?,
+    readindexer: (self: type) -> { index: type, result: type }?,
+    writeindexer: (self: type) -> { index: type, result: type }?,
+    setmetatable: (self: type, arg: type) -> (),
+    metatable: (self: type) -> type?,
+
+    -- for function type
+    setparameters: (self: type, head: {type}?, tail: type?) -> (),
+    parameters: (self: type) -> { head: {type}?, tail: type? },
+    setreturns: (self: type, head: {type}?, tail: type? ) -> (),
+    returns: (self: type) -> { head: {type}?, tail: type? },
+    setgenerics: (self: type, {type}?) -> (),
+    generics: (self: type) -> {type},
+
+    -- for class type
+    -- 'properties', 'metatable', 'indexer', 'readindexer' and 'writeindexer' are shared with table type
+    readparent: (self: type) -> type?,
+    writeparent: (self: type) -> type?,
+
+    -- for generic type
+    name: (self: type) -> string?,
+    ispack: (self: type) -> boolean,
+}
+
+declare types: {
+    unknown: type,
+    never: type,
+    any: type,
+    boolean: type,
+    number: type,
+    string: type,
+    thread: type,
+    buffer: type,
+
+    singleton: @checked (arg: string | boolean | nil) -> type,
+    generic: @checked (name: string, ispack: boolean?) -> type,
+    negationof: @checked (arg: type) -> type,
+    unionof: @checked (...type) -> type,
+    intersectionof: @checked (...type) -> type,
+    newtable: @checked (props: {[type]: type} | {[type]: { read: type, write: type } } | nil, indexer: { index: type, readresult: type, writeresult: type }?, metatable: type?) -> type,
+    newfunction: @checked (parameters: { head: {type}?, tail: type? }?, returns: { head: {type}?, tail: type? }?, generics: {type}?) -> type,
+    copy: @checked (arg: type) -> type,
+}
+
+)BUILTIN_SRC";
+
+std::string getTypeFunctionDefinitionSource()
+{
+    return kBuiltinDefinitionTypesSrc;
+}
+
 } // namespace Luau

Analysis/src/Error.cpp

@@ -8,6 +8,7 @@
 #include "Luau/StringUtils.h"
 #include "Luau/ToString.h"
 #include "Luau/Type.h"
+#include "Luau/TypeChecker2.h"
 #include "Luau/TypeFunction.h"
 
 #include <optional>
@@ -17,6 +18,7 @@
 #include <unordered_set>
 
 LUAU_FASTINTVARIABLE(LuauIndentTypeMismatchMaxTypeLength, 10)
+LUAU_FASTFLAG(LuauNonStrictFuncDefErrorFix)
 
 static std::string wrongNumberOfArgsString(
     size_t expectedCount,
@@ -116,7 +118,10 @@ struct ErrorConverter
             size_t luauIndentTypeMismatchMaxTypeLength = size_t(FInt::LuauIndentTypeMismatchMaxTypeLength);
             if (givenType.length() <= luauIndentTypeMismatchMaxTypeLength || wantedType.length() <= luauIndentTypeMismatchMaxTypeLength)
                 return "Type " + given + " could not be converted into " + wanted;
-            return "Type\n    " + given + "\ncould not be converted into\n    " + wanted;
+            if (FFlag::LuauImproveTypePathsInErrors)
+                return "Type\n\t" + given + "\ncould not be converted into\n\t" + wanted;
+            else
+                return "Type\n    " + given + "\ncould not be converted into\n    " + wanted;
         };
 
         if (givenTypeName == wantedTypeName)
@@ -601,7 +606,7 @@ struct ErrorConverter
         auto tfit = get<TypeFunctionInstanceType>(e.ty);
         LUAU_ASSERT(tfit); // Luau analysis has actually done something wrong if this type is not a type function.
         if (!tfit)
-            return "Unexpected type " + Luau::toString(e.ty) + " flagged as an uninhabited type function.";
+            return "Internal error: Unexpected type " + Luau::toString(e.ty) + " flagged as an uninhabited type function.";
 
         // unary operators
         if (auto unaryString = kUnaryOps.find(tfit->function->name); unaryString != kUnaryOps.end())
@@ -751,8 +756,15 @@ struct ErrorConverter
 
     std::string operator()(const NonStrictFunctionDefinitionError& e) const
     {
-        return "Argument " + e.argument + " with type '" + toString(e.argumentType) + "' in function '" + e.functionName +
+        if (FFlag::LuauNonStrictFuncDefErrorFix && e.functionName.empty())
-               "' is used in a way that will run time error";
+        {
+            return "Argument " + e.argument + " with type '" + toString(e.argumentType) + "' is used in a way that will run time error";
+        }
+        else
+        {
+            return "Argument " + e.argument + " with type '" + toString(e.argumentType) + "' in function '" + e.functionName +
+                   "' is used in a way that will run time error";
+        }
     }
 
     std::string operator()(const PropertyAccessViolation& e) const

Analysis/src/FileResolver.cpp

@@ -0,0 +1,172 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/FileResolver.h"
+
+#include "Luau/Common.h"
+#include "Luau/StringUtils.h"
+
+#include <algorithm>
+#include <memory>
+#include <optional>
+#include <string_view>
+#include <utility>
+
+LUAU_FASTFLAGVARIABLE(LuauExposeRequireByStringAutocomplete)
+LUAU_FASTFLAGVARIABLE(LuauEscapeCharactersInRequireSuggestions)
+LUAU_FASTFLAGVARIABLE(LuauHideImpossibleRequireSuggestions)
+
+namespace Luau
+{
+
+static std::optional<RequireSuggestions> processRequireSuggestions(std::optional<RequireSuggestions> suggestions)
+{
+    if (!suggestions)
+        return suggestions;
+
+    if (FFlag::LuauEscapeCharactersInRequireSuggestions)
+    {
+        for (RequireSuggestion& suggestion : *suggestions)
+        {
+            suggestion.fullPath = escape(suggestion.fullPath);
+        }
+    }
+
+    return suggestions;
+}
+
+static RequireSuggestions makeSuggestionsFromAliases(std::vector<RequireAlias> aliases)
+{
+    RequireSuggestions result;
+    for (RequireAlias& alias : aliases)
+    {
+        RequireSuggestion suggestion;
+        suggestion.label = "@" + std::move(alias.alias);
+        suggestion.fullPath = suggestion.label;
+        suggestion.tags = std::move(alias.tags);
+        result.push_back(std::move(suggestion));
+    }
+    return result;
+}
+
+static RequireSuggestions makeSuggestionsForFirstComponent(std::unique_ptr<RequireNode> node)
+{
+    RequireSuggestions result = makeSuggestionsFromAliases(node->getAvailableAliases());
+    result.push_back(RequireSuggestion{"./", "./", {}});
+    result.push_back(RequireSuggestion{"../", "../", {}});
+    return result;
+}
+
+static RequireSuggestions makeSuggestionsFromNode(std::unique_ptr<RequireNode> node, const std::string_view path, bool isPartialPath)
+{
+    LUAU_ASSERT(!path.empty());
+
+    RequireSuggestions result;
+
+    const size_t lastSlashInPath = path.find_last_of('/');
+
+    if (lastSlashInPath != std::string_view::npos)
+    {
+        // Add a suggestion for the parent directory
+        RequireSuggestion parentSuggestion;
+        parentSuggestion.label = "..";
+
+        // TODO: after exposing require-by-string's path normalization API, this
+        // if-else can be replaced. Instead, we can simply normalize the result
+        // of inserting ".." at the end of the current path.
+        if (lastSlashInPath >= 2 && path.substr(lastSlashInPath - 2, 3) == "../")
+        {
+            parentSuggestion.fullPath = path.substr(0, lastSlashInPath + 1);
+            parentSuggestion.fullPath += "..";
+        }
+        else
+        {
+            parentSuggestion.fullPath = path.substr(0, lastSlashInPath);
+        }
+
+        result.push_back(std::move(parentSuggestion));
+    }
+
+    std::string fullPathPrefix;
+    if (isPartialPath)
+    {
+        // ./path/to/chi -> ./path/to/
+        fullPathPrefix += path.substr(0, lastSlashInPath + 1);
+    }
+    else
+    {
+        if (path.back() == '/')
+        {
+            // ./path/to/ -> ./path/to/
+            fullPathPrefix += path;
+        }
+        else
+        {
+            // ./path/to -> ./path/to/
+            fullPathPrefix += path;
+            fullPathPrefix += "/";
+        }
+    }
+
+    for (const std::unique_ptr<RequireNode>& child : node->getChildren())
+    {
+        if (!child)
+            continue;
+
+        std::string pathComponent = child->getPathComponent();
+        if (FFlag::LuauHideImpossibleRequireSuggestions)
+        {
+            // If path component contains a slash, it cannot be required by string.
+            // There's no point suggesting it.
+            if (pathComponent.find('/') != std::string::npos)
+                continue;
+        }
+
+        RequireSuggestion suggestion;
+        suggestion.label = isPartialPath || path.back() == '/' ? child->getLabel() : "/" + child->getLabel();
+        suggestion.fullPath = fullPathPrefix + std::move(pathComponent);
+        suggestion.tags = child->getTags();
+        result.push_back(std::move(suggestion));
+    }
+
+    return result;
+}
+
+std::optional<RequireSuggestions> RequireSuggester::getRequireSuggestionsImpl(const ModuleName& requirer, const std::optional<std::string>& path)
+    const
+{
+    if (!path)
+        return std::nullopt;
+
+    std::unique_ptr<RequireNode> requirerNode = getNode(requirer);
+    if (!requirerNode)
+        return std::nullopt;
+
+    const size_t slashPos = path->find_last_of('/');
+
+    if (slashPos == std::string::npos)
+        return makeSuggestionsForFirstComponent(std::move(requirerNode));
+
+    // If path already points at a Node, return the Node's children as paths.
+    if (std::unique_ptr<RequireNode> node = requirerNode->resolvePathToNode(*path))
+        return makeSuggestionsFromNode(std::move(node), *path, /* isPartialPath = */ false);
+
+    // Otherwise, recover a partial path and use this to generate suggestions.
+    if (std::unique_ptr<RequireNode> partialNode = requirerNode->resolvePathToNode(path->substr(0, slashPos)))
+        return makeSuggestionsFromNode(std::move(partialNode), *path, /* isPartialPath = */ true);
+
+    return std::nullopt;
+}
+
+std::optional<RequireSuggestions> RequireSuggester::getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& path) const
+{
+    return processRequireSuggestions(getRequireSuggestionsImpl(requirer, path));
+}
+
+std::optional<RequireSuggestions> FileResolver::getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& path) const
+{
+    if (!FFlag::LuauExposeRequireByStringAutocomplete)
+        return std::nullopt;
+
+    return requireSuggester ? requireSuggester->getRequireSuggestions(requirer, path) : std::nullopt;
+}
+
+} // namespace Luau

Analysis/src/Frontend.cpp

@@ -1,7 +1,6 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Frontend.h"
 
-#include "Luau/AnyTypeSummary.h"
 #include "Luau/BuiltinDefinitions.h"
 #include "Luau/Clone.h"
 #include "Luau/Common.h"
@@ -40,19 +39,15 @@ LUAU_FASTINT(LuauTarjanChildLimit)
 LUAU_FASTFLAG(LuauInferInNoCheckMode)
 LUAU_FASTFLAGVARIABLE(LuauKnowsTheDataModel3)
 LUAU_FASTFLAG(LuauSolverV2)
+LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauRethrowKnownExceptions, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJson)
 LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJsonFile)
 LUAU_FASTFLAGVARIABLE(DebugLuauForbidInternalTypes)
 LUAU_FASTFLAGVARIABLE(DebugLuauForceStrictMode)
 LUAU_FASTFLAGVARIABLE(DebugLuauForceNonStrictMode)
-LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauRunCustomModuleChecks, false)
-
-LUAU_FASTFLAGVARIABLE(LuauBetterReverseDependencyTracking)
-
-LUAU_FASTFLAG(StudioReportLuauAny2)
-LUAU_FASTFLAGVARIABLE(LuauStoreSolverTypeOnModule)
 
 LUAU_FASTFLAGVARIABLE(LuauSelectivelyRetainDFGArena)
+LUAU_FASTFLAG(LuauTypeFunResultInAutocomplete)
 
 namespace Luau
 {
@@ -82,6 +77,20 @@ struct BuildQueueItem
     Frontend::Stats stats;
 };
 
+struct BuildQueueWorkState
+{
+    std::function<void(std::function<void()> task)> executeTask;
+
+    std::vector<BuildQueueItem> buildQueueItems;
+
+    std::mutex mtx;
+    std::condition_variable cv;
+    std::vector<size_t> readyQueueItems;
+
+    size_t processing = 0;
+    size_t remaining = 0;
+};
+
 std::optional<Mode> parseMode(const std::vector<HotComment>& hotcomments)
 {
     for (const HotComment& hc : hotcomments)
@@ -446,20 +455,6 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
 
         if (item.name == name)
             checkResult.lintResult = item.module->lintResult;
-
-        if (FFlag::StudioReportLuauAny2 && item.options.retainFullTypeGraphs)
-        {
-            if (item.module)
-            {
-                const SourceModule& sourceModule = *item.sourceModule;
-                if (sourceModule.mode == Luau::Mode::Strict)
-                {
-                    item.module->ats.root = toString(sourceModule.root);
-                }
-                item.module->ats.rootSrc = sourceModule.root;
-                item.module->ats.traverse(item.module.get(), sourceModule.root, NotNull{&builtinTypes_});
-            }
-        }
     }
 
     return checkResult;
@@ -490,7 +485,8 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
     std::swap(currModuleQueue, moduleQueue);
 
     DenseHashSet<Luau::ModuleName> seen{{}};
-    std::vector<BuildQueueItem> buildQueueItems;
+
+    std::shared_ptr<BuildQueueWorkState> state = std::make_shared<BuildQueueWorkState>();
 
     for (const ModuleName& name : currModuleQueue)
     {
@@ -514,18 +510,18 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
             }
         );
 
-        addBuildQueueItems(buildQueueItems, queue, cycleDetected, seen, frontendOptions);
+        addBuildQueueItems(state->buildQueueItems, queue, cycleDetected, seen, frontendOptions);
     }
 
-    if (buildQueueItems.empty())
+    if (state->buildQueueItems.empty())
         return {};
 
     // We need a mapping from modules to build queue slots
     std::unordered_map<ModuleName, size_t> moduleNameToQueue;
 
-    for (size_t i = 0; i < buildQueueItems.size(); i++)
+    for (size_t i = 0; i < state->buildQueueItems.size(); i++)
     {
-        BuildQueueItem& item = buildQueueItems[i];
+        BuildQueueItem& item = state->buildQueueItems[i];
         moduleNameToQueue[item.name] = i;
     }
 
@@ -538,67 +534,13 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
         };
     }
 
-    std::mutex mtx;
+    state->executeTask = executeTask;
-    std::condition_variable cv;
+    state->remaining = state->buildQueueItems.size();
-    std::vector<size_t> readyQueueItems;
 
-    size_t processing = 0;
+    // Record dependencies between modules
-    size_t remaining = buildQueueItems.size();
+    for (size_t i = 0; i < state->buildQueueItems.size(); i++)
-
-    auto itemTask = [&](size_t i)
     {
-        BuildQueueItem& item = buildQueueItems[i];
+        BuildQueueItem& item = state->buildQueueItems[i];
-
-        try
-        {
-            checkBuildQueueItem(item);
-        }
-        catch (...)
-        {
-            item.exception = std::current_exception();
-        }
-
-        {
-            std::unique_lock guard(mtx);
-            readyQueueItems.push_back(i);
-        }
-
-        cv.notify_one();
-    };
-
-    auto sendItemTask = [&](size_t i)
-    {
-        BuildQueueItem& item = buildQueueItems[i];
-
-        item.processing = true;
-        processing++;
-
-        executeTask(
-            [&itemTask, i]()
-            {
-                itemTask(i);
-            }
-        );
-    };
-
-    auto sendCycleItemTask = [&]
-    {
-        for (size_t i = 0; i < buildQueueItems.size(); i++)
-        {
-            BuildQueueItem& item = buildQueueItems[i];
-
-            if (!item.processing)
-            {
-                sendItemTask(i);
-                break;
-            }
-        }
-    };
-
-    // In a first pass, check modules that have no dependencies and record info of those modules that wait
-    for (size_t i = 0; i < buildQueueItems.size(); i++)
-    {
-        BuildQueueItem& item = buildQueueItems[i];
 
         for (const ModuleName& dep : item.sourceNode->requireSet)
         {
@@ -608,41 +550,45 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
                 {
                     item.dirtyDependencies++;
 
-                    buildQueueItems[moduleNameToQueue[dep]].reverseDeps.push_back(i);
+                    state->buildQueueItems[moduleNameToQueue[dep]].reverseDeps.push_back(i);
                 }
             }
         }
-
-        if (item.dirtyDependencies == 0)
-            sendItemTask(i);
     }
 
-    // Not a single item was found, a cycle in the graph was hit
+    // In the first pass, check all modules with no pending dependencies
-    if (processing == 0)
+    for (size_t i = 0; i < state->buildQueueItems.size(); i++)
-        sendCycleItemTask();
+    {
+        if (state->buildQueueItems[i].dirtyDependencies == 0)
+            sendQueueItemTask(state, i);
+    }
+
+    // If not a single item was found, a cycle in the graph was hit
+    if (state->processing == 0)
+        sendQueueCycleItemTask(state);
 
     std::vector<size_t> nextItems;
     std::optional<size_t> itemWithException;
     bool cancelled = false;
 
-    while (remaining != 0)
+    while (state->remaining != 0)
     {
         {
-            std::unique_lock guard(mtx);
+            std::unique_lock guard(state->mtx);
 
             // If nothing is ready yet, wait
-            cv.wait(
+            state->cv.wait(
                 guard,
-                [&readyQueueItems]
+                [state]
                 {
-                    return !readyQueueItems.empty();
+                    return !state->readyQueueItems.empty();
                 }
             );
 
             // Handle checked items
-            for (size_t i : readyQueueItems)
+            for (size_t i : state->readyQueueItems)
             {
-                const BuildQueueItem& item = buildQueueItems[i];
+                const BuildQueueItem& item = state->buildQueueItems[i];
 
                 // If exception was thrown, stop adding new items and wait for processing items to complete
                 if (item.exception)
@@ -659,7 +605,7 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
                 // Notify items that were waiting for this dependency
                 for (size_t reverseDep : item.reverseDeps)
                 {
-                    BuildQueueItem& reverseDepItem = buildQueueItems[reverseDep];
+                    BuildQueueItem& reverseDepItem = state->buildQueueItems[reverseDep];
 
                     LUAU_ASSERT(reverseDepItem.dirtyDependencies != 0);
                     reverseDepItem.dirtyDependencies--;
@@ -670,26 +616,26 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
                 }
             }
 
-            LUAU_ASSERT(processing >= readyQueueItems.size());
+            LUAU_ASSERT(state->processing >= state->readyQueueItems.size());
-            processing -= readyQueueItems.size();
+            state->processing -= state->readyQueueItems.size();
 
-            LUAU_ASSERT(remaining >= readyQueueItems.size());
+            LUAU_ASSERT(state->remaining >= state->readyQueueItems.size());
-            remaining -= readyQueueItems.size();
+            state->remaining -= state->readyQueueItems.size();
-            readyQueueItems.clear();
+            state->readyQueueItems.clear();
         }
 
         if (progress)
         {
-            if (!progress(buildQueueItems.size() - remaining, buildQueueItems.size()))
+            if (!progress(state->buildQueueItems.size() - state->remaining, state->buildQueueItems.size()))
                 cancelled = true;
         }
 
         // Items cannot be submitted while holding the lock
         for (size_t i : nextItems)
-            sendItemTask(i);
+            sendQueueItemTask(state, i);
         nextItems.clear();
 
-        if (processing == 0)
+        if (state->processing == 0)
         {
             // Typechecking might have been cancelled by user, don't return partial results
             if (cancelled)
@@ -697,19 +643,19 @@ std::vector<ModuleName> Frontend::checkQueuedModules(
 
             // We might have stopped because of a pending exception
             if (itemWithException)
-                recordItemResult(buildQueueItems[*itemWithException]);
+                recordItemResult(state->buildQueueItems[*itemWithException]);
         }
 
         // If we aren't done, but don't have anything processing, we hit a cycle
-        if (remaining != 0 && processing == 0)
+        if (state->remaining != 0 && state->processing == 0)
-            sendCycleItemTask();
+            sendQueueCycleItemTask(state);
     }
 
     std::vector<ModuleName> checkedModules;
-    checkedModules.reserve(buildQueueItems.size());
+    checkedModules.reserve(state->buildQueueItems.size());
 
-    for (size_t i = 0; i < buildQueueItems.size(); i++)
+    for (size_t i = 0; i < state->buildQueueItems.size(); i++)
-        checkedModules.push_back(std::move(buildQueueItems[i].name));
+        checkedModules.push_back(std::move(state->buildQueueItems[i].name));
 
     return checkedModules;
 }
@@ -822,14 +768,11 @@ bool Frontend::parseGraph(
 
             buildQueue.push_back(top->name);
 
-            if (FFlag::LuauBetterReverseDependencyTracking)
+            // at this point we know all valid dependencies are processed into SourceNodes
+            for (const ModuleName& dep : top->requireSet)
             {
-                // at this point we know all valid dependencies are processed into SourceNodes
+                if (auto it = sourceNodes.find(dep); it != sourceNodes.end())
-                for (const ModuleName& dep : top->requireSet)
+                    it->second->dependents.insert(top->name);
-                {
-                    if (auto it = sourceNodes.find(dep); it != sourceNodes.end())
-                        it->second->dependents.insert(top->name);
-                }
             }
         }
         else
@@ -1008,7 +951,7 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
         item.stats.timeCheck += duration;
         item.stats.filesStrict += 1;
 
-        if (DFFlag::LuauRunCustomModuleChecks && item.options.customModuleCheck)
+        if (item.options.customModuleCheck)
             item.options.customModuleCheck(sourceModule, *moduleForAutocomplete);
 
         item.module = moduleForAutocomplete;
@@ -1028,7 +971,7 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
     item.stats.filesStrict += mode == Mode::Strict;
     item.stats.filesNonstrict += mode == Mode::Nonstrict;
 
-    if (DFFlag::LuauRunCustomModuleChecks && item.options.customModuleCheck)
+    if (item.options.customModuleCheck)
         item.options.customModuleCheck(sourceModule, *module);
 
     if (FFlag::LuauSolverV2 && mode == Mode::NoCheck)
@@ -1118,51 +1061,35 @@ void Frontend::recordItemResult(const BuildQueueItem& item)
     if (item.exception)
         std::rethrow_exception(item.exception);
 
-    if (FFlag::LuauBetterReverseDependencyTracking)
+    bool replacedModule = false;
+    if (item.options.forAutocomplete)
     {
-        bool replacedModule = false;
+        replacedModule = moduleResolverForAutocomplete.setModule(item.name, item.module);
-        if (item.options.forAutocomplete)
+        item.sourceNode->dirtyModuleForAutocomplete = false;
-        {
-            replacedModule = moduleResolverForAutocomplete.setModule(item.name, item.module);
-            item.sourceNode->dirtyModuleForAutocomplete = false;
-        }
-        else
-        {
-            replacedModule = moduleResolver.setModule(item.name, item.module);
-            item.sourceNode->dirtyModule = false;
-        }
-
-        if (replacedModule)
-        {
-            LUAU_TIMETRACE_SCOPE("Frontend::invalidateDependentModules", "Frontend");
-            LUAU_TIMETRACE_ARGUMENT("name", item.name.c_str());
-            traverseDependents(
-                item.name,
-                [forAutocomplete = item.options.forAutocomplete](SourceNode& sourceNode)
-                {
-                    bool traverseSubtree = !sourceNode.hasInvalidModuleDependency(forAutocomplete);
-                    sourceNode.setInvalidModuleDependency(true, forAutocomplete);
-                    return traverseSubtree;
-                }
-            );
-        }
-
-        item.sourceNode->setInvalidModuleDependency(false, item.options.forAutocomplete);
     }
     else
     {
-        if (item.options.forAutocomplete)
+        replacedModule = moduleResolver.setModule(item.name, item.module);
-        {
+        item.sourceNode->dirtyModule = false;
-            moduleResolverForAutocomplete.setModule(item.name, item.module);
-            item.sourceNode->dirtyModuleForAutocomplete = false;
-        }
-        else
-        {
-            moduleResolver.setModule(item.name, item.module);
-            item.sourceNode->dirtyModule = false;
-        }
     }
 
+    if (replacedModule)
+    {
+        LUAU_TIMETRACE_SCOPE("Frontend::invalidateDependentModules", "Frontend");
+        LUAU_TIMETRACE_ARGUMENT("name", item.name.c_str());
+        traverseDependents(
+            item.name,
+            [forAutocomplete = item.options.forAutocomplete](SourceNode& sourceNode)
+            {
+                bool traverseSubtree = !sourceNode.hasInvalidModuleDependency(forAutocomplete);
+                sourceNode.setInvalidModuleDependency(true, forAutocomplete);
+                return traverseSubtree;
+            }
+        );
+    }
+
+    item.sourceNode->setInvalidModuleDependency(false, item.options.forAutocomplete);
+
     stats.timeCheck += item.stats.timeCheck;
     stats.timeLint += item.stats.timeLint;
 
@@ -1170,6 +1097,72 @@ void Frontend::recordItemResult(const BuildQueueItem& item)
     stats.filesNonstrict += item.stats.filesNonstrict;
 }
 
+void Frontend::performQueueItemTask(std::shared_ptr<BuildQueueWorkState> state, size_t itemPos)
+{
+    BuildQueueItem& item = state->buildQueueItems[itemPos];
+
+    if (DFFlag::LuauRethrowKnownExceptions)
+    {
+        try
+        {
+            checkBuildQueueItem(item);
+        }
+        catch (const Luau::InternalCompilerError&)
+        {
+            item.exception = std::current_exception();
+        }
+    }
+    else
+    {
+        try
+        {
+            checkBuildQueueItem(item);
+        }
+        catch (...)
+        {
+            item.exception = std::current_exception();
+        }
+    }
+
+    {
+        std::unique_lock guard(state->mtx);
+        state->readyQueueItems.push_back(itemPos);
+    }
+
+    state->cv.notify_one();
+}
+
+void Frontend::sendQueueItemTask(std::shared_ptr<BuildQueueWorkState> state, size_t itemPos)
+{
+    BuildQueueItem& item = state->buildQueueItems[itemPos];
+
+    LUAU_ASSERT(!item.processing);
+    item.processing = true;
+
+    state->processing++;
+
+    state->executeTask(
+        [this, state, itemPos]()
+        {
+            performQueueItemTask(state, itemPos);
+        }
+    );
+}
+
+void Frontend::sendQueueCycleItemTask(std::shared_ptr<BuildQueueWorkState> state)
+{
+    for (size_t i = 0; i < state->buildQueueItems.size(); i++)
+    {
+        BuildQueueItem& item = state->buildQueueItems[i];
+
+        if (!item.processing)
+        {
+            sendQueueItemTask(state, i);
+            break;
+        }
+    }
+}
+
 ScopePtr Frontend::getModuleEnvironment(const SourceModule& module, const Config& config, bool forAutocomplete) const
 {
     ScopePtr result;
@@ -1199,7 +1192,6 @@ ScopePtr Frontend::getModuleEnvironment(const SourceModule& module, const Config
 
 bool Frontend::allModuleDependenciesValid(const ModuleName& name, bool forAutocomplete) const
 {
-    LUAU_ASSERT(FFlag::LuauBetterReverseDependencyTracking);
     auto it = sourceNodes.find(name);
     return it != sourceNodes.end() && !it->second->hasInvalidModuleDependency(forAutocomplete);
 }
@@ -1221,72 +1213,27 @@ void Frontend::markDirty(const ModuleName& name, std::vector<ModuleName>* marked
     LUAU_TIMETRACE_SCOPE("Frontend::markDirty", "Frontend");
     LUAU_TIMETRACE_ARGUMENT("name", name.c_str());
 
-    if (FFlag::LuauBetterReverseDependencyTracking)
+    traverseDependents(
-    {
+        name,
-        traverseDependents(
+        [markedDirty](SourceNode& sourceNode)
-            name,
-            [markedDirty](SourceNode& sourceNode)
-            {
-                if (markedDirty)
-                    markedDirty->push_back(sourceNode.name);
-
-                if (sourceNode.dirtySourceModule && sourceNode.dirtyModule && sourceNode.dirtyModuleForAutocomplete)
-                    return false;
-
-                sourceNode.dirtySourceModule = true;
-                sourceNode.dirtyModule = true;
-                sourceNode.dirtyModuleForAutocomplete = true;
-
-                return true;
-            }
-        );
-    }
-    else
-    {
-        if (sourceNodes.count(name) == 0)
-            return;
-
-        std::unordered_map<ModuleName, std::vector<ModuleName>> reverseDeps;
-        for (const auto& module : sourceNodes)
         {
-            for (const auto& dep : module.second->requireSet)
-                reverseDeps[dep].push_back(module.first);
-        }
-
-        std::vector<ModuleName> queue{name};
-
-        while (!queue.empty())
-        {
-            ModuleName next = std::move(queue.back());
-            queue.pop_back();
-
-            LUAU_ASSERT(sourceNodes.count(next) > 0);
-            SourceNode& sourceNode = *sourceNodes[next];
-
             if (markedDirty)
-                markedDirty->push_back(next);
+                markedDirty->push_back(sourceNode.name);
 
             if (sourceNode.dirtySourceModule && sourceNode.dirtyModule && sourceNode.dirtyModuleForAutocomplete)
-                continue;
+                return false;
 
             sourceNode.dirtySourceModule = true;
             sourceNode.dirtyModule = true;
             sourceNode.dirtyModuleForAutocomplete = true;
 
-            if (0 == reverseDeps.count(next))
+            return true;
-                continue;
-
-            sourceModules.erase(next);
-
-            const std::vector<ModuleName>& dependents = reverseDeps[next];
-            queue.insert(queue.end(), dependents.begin(), dependents.end());
         }
-    }
+    );
 }
 
 void Frontend::traverseDependents(const ModuleName& name, std::function<bool(SourceNode&)> processSubtree)
 {
-    LUAU_ASSERT(FFlag::LuauBetterReverseDependencyTracking);
     LUAU_TIMETRACE_SCOPE("Frontend::traverseDependents", "Frontend");
 
     if (sourceNodes.count(name) == 0)
@@ -1333,6 +1280,7 @@ ModulePtr check(
     NotNull<ModuleResolver> moduleResolver,
     NotNull<FileResolver> fileResolver,
     const ScopePtr& parentScope,
+    const ScopePtr& typeFunctionScope,
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
     FrontendOptions options,
     TypeCheckLimits limits,
@@ -1349,6 +1297,7 @@ ModulePtr check(
         moduleResolver,
         fileResolver,
         parentScope,
+        typeFunctionScope,
         std::move(prepareModuleScope),
         options,
         limits,
@@ -1410,6 +1359,7 @@ ModulePtr check(
     NotNull<ModuleResolver> moduleResolver,
     NotNull<FileResolver> fileResolver,
     const ScopePtr& parentScope,
+    const ScopePtr& typeFunctionScope,
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
     FrontendOptions options,
     TypeCheckLimits limits,
@@ -1422,8 +1372,7 @@ ModulePtr check(
     LUAU_TIMETRACE_ARGUMENT("name", sourceModule.humanReadableName.c_str());
 
     ModulePtr result = std::make_shared<Module>();
-    if (FFlag::LuauStoreSolverTypeOnModule)
+    result->checkedInNewSolver = true;
-        result->checkedInNewSolver = true;
     result->name = sourceModule.name;
     result->humanReadableName = sourceModule.humanReadableName;
     result->mode = mode;
@@ -1431,6 +1380,7 @@ ModulePtr check(
     result->interfaceTypes.owningModule = result.get();
     result->allocator = sourceModule.allocator;
     result->names = sourceModule.names;
+    result->root = sourceModule.root;
 
     iceHandler->moduleName = sourceModule.name;
 
@@ -1455,7 +1405,7 @@ ModulePtr check(
     SimplifierPtr simplifier = newSimplifier(NotNull{&result->internalTypes}, builtinTypes);
     TypeFunctionRuntime typeFunctionRuntime{iceHandler, NotNull{&limits}};
 
-    typeFunctionRuntime.allowEvaluation = sourceModule.parseErrors.empty();
+    typeFunctionRuntime.allowEvaluation = FFlag::LuauTypeFunResultInAutocomplete || sourceModule.parseErrors.empty();
 
     ConstraintGenerator cg{
         result,
@@ -1466,6 +1416,7 @@ ModulePtr check(
         builtinTypes,
         iceHandler,
         parentScope,
+        typeFunctionScope,
         std::move(prepareModuleScope),
         logger.get(),
         NotNull{&dfg},
@@ -1648,6 +1599,7 @@ ModulePtr Frontend::check(
                 NotNull{forAutocomplete ? &moduleResolverForAutocomplete : &moduleResolver},
                 NotNull{fileResolver},
                 environmentScope ? *environmentScope : globals.globalScope,
+                globals.globalTypeFunctionScope,
                 prepareModuleScopeWrap,
                 options,
                 typeCheckLimits,
@@ -1746,14 +1698,11 @@ std::pair<SourceNode*, SourceModule*> Frontend::getSourceNode(const ModuleName&
     sourceNode->name = sourceModule->name;
     sourceNode->humanReadableName = sourceModule->humanReadableName;
 
-    if (FFlag::LuauBetterReverseDependencyTracking)
+    // clear all prior dependents. we will re-add them after parsing the rest of the graph
+    for (const auto& [moduleName, _] : sourceNode->requireLocations)
     {
-        // clear all prior dependents. we will re-add them after parsing the rest of the graph
+        if (auto depIt = sourceNodes.find(moduleName); depIt != sourceNodes.end())
-        for (const auto& [moduleName, _] : sourceNode->requireLocations)
+            depIt->second->dependents.erase(sourceNode->name);
-        {
-            if (auto depIt = sourceNodes.find(moduleName); depIt != sourceNodes.end())
-                depIt->second->dependents.erase(sourceNode->name);
-        }
     }
 
     sourceNode->requireSet.clear();
@@ -1881,17 +1830,9 @@ bool FrontendModuleResolver::setModule(const ModuleName& moduleName, ModulePtr m
 {
     std::scoped_lock lock(moduleMutex);
 
-    if (FFlag::LuauBetterReverseDependencyTracking)
+    bool replaced = modules.count(moduleName) > 0;
-    {
+    modules[moduleName] = std::move(module);
-        bool replaced = modules.count(moduleName) > 0;
+    return replaced;
-        modules[moduleName] = std::move(module);
-        return replaced;
-    }
-    else
-    {
-        modules[moduleName] = std::move(module);
-        return false;
-    }
 }
 
 void FrontendModuleResolver::clearModules()

Analysis/src/Generalization.cpp

@@ -4,19 +4,84 @@
 
 #include "Luau/Common.h"
 #include "Luau/DenseHash.h"
+#include "Luau/InsertionOrderedMap.h"
+#include "Luau/Polarity.h"
 #include "Luau/Scope.h"
-#include "Luau/Type.h"
 #include "Luau/ToString.h"
+#include "Luau/Type.h"
 #include "Luau/TypeArena.h"
 #include "Luau/TypePack.h"
 #include "Luau/VisitType.h"
 
 LUAU_FASTFLAG(LuauAutocompleteRefactorsForIncrementalAutocomplete)
-LUAU_FASTFLAGVARIABLE(LuauGeneralizationRemoveRecursiveUpperBound2)
+
+LUAU_FASTFLAGVARIABLE(LuauNonReentrantGeneralization)
 
 namespace Luau
 {
 
+namespace
+{
+
+template<typename T>
+struct OrderedSet
+{
+    using iterator = typename std::vector<T>::iterator;
+    using const_iterator = typename std::vector<T>::const_iterator;
+
+    bool empty() const
+    {
+        return elements.empty();
+    }
+
+    size_t size() const
+    {
+        return elements.size();
+    }
+
+    void insert(T t)
+    {
+        if (!elementSet.contains(t))
+        {
+            elementSet.insert(t);
+            elements.push_back(t);
+        }
+    }
+
+    iterator begin()
+    {
+        return elements.begin();
+    }
+
+    const_iterator begin() const
+    {
+        return elements.begin();
+    }
+
+    iterator end()
+    {
+        return elements.end();
+    }
+
+    const_iterator end() const
+    {
+        return elements.end();
+    }
+
+    /// Move the underlying vector out of the OrderedSet.
+    std::vector<T> takeVector()
+    {
+        elementSet.clear();
+        return std::move(elements);
+    }
+
+private:
+    std::vector<T> elements;
+    DenseHashSet<T> elementSet{nullptr};
+};
+
+} // namespace
+
 struct MutatingGeneralizer : TypeOnceVisitor
 {
     NotNull<TypeArena> arena;
@@ -30,7 +95,6 @@ struct MutatingGeneralizer : TypeOnceVisitor
     std::vector<TypePackId> genericPacks;
 
     bool isWithinFunction = false;
-    bool avoidSealingTables = false;
 
     MutatingGeneralizer(
         NotNull<TypeArena> arena,
@@ -38,8 +102,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
         NotNull<Scope> scope,
         NotNull<DenseHashSet<TypeId>> cachedTypes,
         DenseHashMap<const void*, size_t> positiveTypes,
-        DenseHashMap<const void*, size_t> negativeTypes,
+        DenseHashMap<const void*, size_t> negativeTypes
-        bool avoidSealingTables
     )
         : TypeOnceVisitor(/* skipBoundTypes */ true)
         , arena(arena)
@@ -48,7 +111,6 @@ struct MutatingGeneralizer : TypeOnceVisitor
         , cachedTypes(cachedTypes)
         , positiveTypes(std::move(positiveTypes))
         , negativeTypes(std::move(negativeTypes))
-        , avoidSealingTables(avoidSealingTables)
     {
     }
 
@@ -99,7 +161,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
                 LUAU_ASSERT(onlyType != haystack);
                 emplaceType<BoundType>(asMutable(haystack), onlyType);
             }
-            else if (FFlag::LuauGeneralizationRemoveRecursiveUpperBound2 && ut->options.empty())
+            else if (ut->options.empty())
             {
                 emplaceType<BoundType>(asMutable(haystack), builtinTypes->neverType);
             }
@@ -146,7 +208,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
                 LUAU_ASSERT(onlyType != needle);
                 emplaceType<BoundType>(asMutable(needle), onlyType);
             }
-            else if (FFlag::LuauGeneralizationRemoveRecursiveUpperBound2 && it->parts.empty())
+            else if (it->parts.empty())
             {
                 emplaceType<BoundType>(asMutable(needle), builtinTypes->unknownType);
             }
@@ -274,6 +336,15 @@ struct MutatingGeneralizer : TypeOnceVisitor
             return 0;
     }
 
+    template<typename TID>
+    static size_t getCount(const DenseHashMap<TID, size_t>& map, TID ty)
+    {
+        if (const size_t* count = map.find(ty))
+            return *count;
+        else
+            return 0;
+    }
+
     bool visit(TypeId ty, const TableType&) override
     {
         if (cachedTypes->contains(ty))
@@ -292,8 +363,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
         TableType* tt = getMutable<TableType>(ty);
         LUAU_ASSERT(tt);
 
-        if (!avoidSealingTables)
+        tt->state = TableState::Sealed;
-            tt->state = TableState::Sealed;
 
         return true;
     }
@@ -332,38 +402,22 @@ struct FreeTypeSearcher : TypeVisitor
     {
     }
 
-    enum Polarity
+    bool isWithinFunction = false;
-    {
+    Polarity polarity = Polarity::Positive;
-        Positive,
-        Negative,
-        Both,
-    };
-
-    Polarity polarity = Positive;
 
     void flip()
     {
-        switch (polarity)
+        polarity = invert(polarity);
-        {
-        case Positive:
-            polarity = Negative;
-            break;
-        case Negative:
-            polarity = Positive;
-            break;
-        case Both:
-            break;
-        }
     }
 
     DenseHashSet<const void*> seenPositive{nullptr};
     DenseHashSet<const void*> seenNegative{nullptr};
 
-    bool seenWithPolarity(const void* ty)
+    bool seenWithCurrentPolarity(const void* ty)
     {
         switch (polarity)
         {
-        case Positive:
+        case Polarity::Positive:
         {
             if (seenPositive.contains(ty))
                 return true;
@@ -371,7 +425,7 @@ struct FreeTypeSearcher : TypeVisitor
             seenPositive.insert(ty);
             return false;
         }
-        case Negative:
+        case Polarity::Negative:
         {
             if (seenNegative.contains(ty))
                 return true;
@@ -379,7 +433,7 @@ struct FreeTypeSearcher : TypeVisitor
             seenNegative.insert(ty);
             return false;
         }
-        case Both:
+        case Polarity::Mixed:
         {
             if (seenPositive.contains(ty) && seenNegative.contains(ty))
                 return true;
@@ -388,20 +442,24 @@ struct FreeTypeSearcher : TypeVisitor
             seenNegative.insert(ty);
             return false;
         }
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
 
         return false;
     }
 
-    // The keys in these maps are either TypeIds or TypePackIds. It's safe to
-    // mix them because we only use these pointers as unique keys.  We never
-    // indirect them.
     DenseHashMap<const void*, size_t> negativeTypes{0};
     DenseHashMap<const void*, size_t> positiveTypes{0};
 
+    InsertionOrderedMap<TypeId, GeneralizationParams<TypeId>> types;
+    InsertionOrderedMap<TypePackId, GeneralizationParams<TypePackId>> typePacks;
+
+    OrderedSet<TypeId> unsealedTables;
+
     bool visit(TypeId ty) override
     {
-        if (cachedTypes->contains(ty) || seenWithPolarity(ty))
+        if (cachedTypes->contains(ty) || seenWithCurrentPolarity(ty))
             return false;
 
         LUAU_ASSERT(ty);
@@ -410,24 +468,45 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const FreeType& ft) override
     {
-        if (cachedTypes->contains(ty) || seenWithPolarity(ty))
+        if (FFlag::LuauNonReentrantGeneralization)
-            return false;
-
-        if (!subsumes(scope, ft.scope))
-            return true;
-
-        switch (polarity)
         {
-        case Positive:
+            if (!subsumes(scope, ft.scope))
-            positiveTypes[ty]++;
+                return true;
-            break;
+
-        case Negative:
+            GeneralizationParams<TypeId>& params = types[ty];
-            negativeTypes[ty]++;
+            ++params.useCount;
-            break;
+
-        case Both:
+            if (cachedTypes->contains(ty) || seenWithCurrentPolarity(ty))
-            positiveTypes[ty]++;
+                return false;
-            negativeTypes[ty]++;
+
-            break;
+            if (!isWithinFunction)
+                params.foundOutsideFunctions = true;
+
+            params.polarity |= polarity;
+        }
+        else
+        {
+            if (cachedTypes->contains(ty) || seenWithCurrentPolarity(ty))
+                return false;
+
+            if (!subsumes(scope, ft.scope))
+                return true;
+
+            switch (polarity)
+            {
+            case Polarity::Positive:
+                positiveTypes[ty]++;
+                break;
+            case Polarity::Negative:
+                negativeTypes[ty]++;
+                break;
+            case Polarity::Mixed:
+                positiveTypes[ty]++;
+                negativeTypes[ty]++;
+                break;
+            default:
+                LUAU_ASSERT(!"Unreachable");
+            }
         }
 
         return true;
@@ -435,23 +514,30 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const TableType& tt) override
     {
-        if (cachedTypes->contains(ty) || seenWithPolarity(ty))
+        if (cachedTypes->contains(ty) || seenWithCurrentPolarity(ty))
             return false;
 
         if ((tt.state == TableState::Free || tt.state == TableState::Unsealed) && subsumes(scope, tt.scope))
         {
-            switch (polarity)
+            if (FFlag::LuauNonReentrantGeneralization)
+                unsealedTables.insert(ty);
+            else
             {
-            case Positive:
+                switch (polarity)
-                positiveTypes[ty]++;
+                {
-                break;
+                case Polarity::Positive:
-            case Negative:
+                    positiveTypes[ty]++;
-                negativeTypes[ty]++;
+                    break;
-                break;
+                case Polarity::Negative:
-            case Both:
+                    negativeTypes[ty]++;
-                positiveTypes[ty]++;
+                    break;
-                negativeTypes[ty]++;
+                case Polarity::Mixed:
-                break;
+                    positiveTypes[ty]++;
+                    negativeTypes[ty]++;
+                    break;
+                default:
+                    LUAU_ASSERT(!"Unreachable");
+                }
             }
         }
 
@@ -464,7 +550,7 @@ struct FreeTypeSearcher : TypeVisitor
                 LUAU_ASSERT(prop.isShared() || FFlag::LuauAutocompleteRefactorsForIncrementalAutocomplete);
 
                 Polarity p = polarity;
-                polarity = Both;
+                polarity = Polarity::Mixed;
                 traverse(prop.type());
                 polarity = p;
             }
@@ -472,8 +558,27 @@ struct FreeTypeSearcher : TypeVisitor
 
         if (tt.indexer)
         {
-            traverse(tt.indexer->indexType);
+            if (FFlag::LuauNonReentrantGeneralization)
-            traverse(tt.indexer->indexResultType);
+            {
+                // {[K]: V} is equivalent to three functions: get, set, and iterate
+                //
+                // (K) -> V
+                // (K, V) -> ()
+                // () -> {K}
+                //
+                // K and V therefore both have mixed polarity.
+
+                const Polarity p = polarity;
+                polarity = Polarity::Mixed;
+                traverse(tt.indexer->indexType);
+                traverse(tt.indexer->indexResultType);
+                polarity = p;
+            }
+            else
+            {
+                traverse(tt.indexer->indexType);
+                traverse(tt.indexer->indexResultType);
+            }
         }
 
         return false;
@@ -481,15 +586,20 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const FunctionType& ft) override
     {
-        if (cachedTypes->contains(ty) || seenWithPolarity(ty))
+        if (cachedTypes->contains(ty) || seenWithCurrentPolarity(ty))
             return false;
 
+        const bool oldValue = isWithinFunction;
+        isWithinFunction = true;
+
         flip();
         traverse(ft.argTypes);
         flip();
 
         traverse(ft.retTypes);
 
+        isWithinFunction = oldValue;
+
         return false;
     }
 
@@ -500,24 +610,39 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypePackId tp, const FreeTypePack& ftp) override
     {
-        if (seenWithPolarity(tp))
+        if (seenWithCurrentPolarity(tp))
             return false;
 
         if (!subsumes(scope, ftp.scope))
             return true;
 
-        switch (polarity)
+        if (FFlag::LuauNonReentrantGeneralization)
         {
-        case Positive:
+            GeneralizationParams<TypePackId>& params = typePacks[tp];
-            positiveTypes[tp]++;
+            ++params.useCount;
-            break;
+
-        case Negative:
+            if (!isWithinFunction)
-            negativeTypes[tp]++;
+                params.foundOutsideFunctions = true;
-            break;
+
-        case Both:
+            params.polarity |= polarity;
-            positiveTypes[tp]++;
+        }
-            negativeTypes[tp]++;
+        else
-            break;
+        {
+            switch (polarity)
+            {
+            case Polarity::Positive:
+                positiveTypes[tp]++;
+                break;
+            case Polarity::Negative:
+                negativeTypes[tp]++;
+                break;
+            case Polarity::Mixed:
+                positiveTypes[tp]++;
+                negativeTypes[tp]++;
+                break;
+            default:
+                LUAU_ASSERT(!"Unreachable");
+            }
         }
 
         return true;
@@ -547,7 +672,7 @@ struct TypeCacher : TypeOnceVisitor
     {
     }
 
-    void cache(TypeId ty)
+    void cache(TypeId ty) const
     {
         cachedTypes->insert(ty);
     }
@@ -967,13 +1092,227 @@ struct TypeCacher : TypeOnceVisitor
     }
 };
 
+/**
+ * Remove occurrences of `needle` within `haystack`.  This is used to cull cyclic bounds from free types.
+ *
+ * @param haystack Either the upper or lower bound of a free type.
+ * @param needle The type to be removed.
+ */
+[[nodiscard]]
+static TypeId removeType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, DenseHashSet<TypeId>& seen, TypeId haystack, TypeId needle)
+{
+    haystack = follow(haystack);
+
+    if (seen.find(haystack))
+        return haystack;
+    seen.insert(haystack);
+
+    if (const UnionType* ut = get<UnionType>(haystack))
+    {
+        OrderedSet<TypeId> newOptions;
+
+        for (TypeId option : ut)
+        {
+            if (option == needle)
+                continue;
+
+            if (get<NeverType>(option))
+                continue;
+
+            LUAU_ASSERT(!get<UnionType>(option));
+
+            if (get<IntersectionType>(option))
+                newOptions.insert(removeType(arena, builtinTypes, seen, option, needle));
+            else
+                newOptions.insert(option);
+        }
+
+        if (newOptions.empty())
+            return builtinTypes->neverType;
+        else if (newOptions.size() == 1)
+        {
+            TypeId onlyType = *newOptions.begin();
+            LUAU_ASSERT(onlyType != haystack);
+            return onlyType;
+        }
+        else
+            return arena->addType(UnionType{newOptions.takeVector()});
+    }
+
+    if (const IntersectionType* it = get<IntersectionType>(haystack))
+    {
+        OrderedSet<TypeId> newParts;
+
+        for (TypeId part : it)
+        {
+            part = follow(part);
+
+            if (part == needle)
+                continue;
+
+            if (get<UnknownType>(part))
+                continue;
+
+            LUAU_ASSERT(!get<IntersectionType>(follow(part)));
+
+            if (get<UnionType>(part))
+                newParts.insert(removeType(arena, builtinTypes, seen, part, needle));
+            else
+                newParts.insert(part);
+        }
+
+        if (newParts.empty())
+            return builtinTypes->unknownType;
+        else if (newParts.size() == 1)
+        {
+            TypeId onlyType = *newParts.begin();
+            LUAU_ASSERT(onlyType != needle);
+            return onlyType;
+        }
+        else
+            return arena->addType(IntersectionType{newParts.takeVector()});
+    }
+
+    return haystack;
+}
+
+std::optional<TypeId> generalizeType(
+    NotNull<TypeArena> arena,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Scope> scope,
+    TypeId freeTy,
+    const GeneralizationParams<TypeId>& params
+)
+{
+    freeTy = follow(freeTy);
+
+    FreeType* ft = getMutable<FreeType>(freeTy);
+    LUAU_ASSERT(ft);
+
+    LUAU_ASSERT(isPositive(params.polarity) || isNegative(params.polarity));
+
+    const bool hasLowerBound = !get<NeverType>(follow(ft->lowerBound));
+    const bool hasUpperBound = !get<UnknownType>(follow(ft->upperBound));
+
+    const bool isWithinFunction = !params.foundOutsideFunctions;
+
+    if (!hasLowerBound && !hasUpperBound)
+    {
+        if ((params.polarity != Polarity::Mixed && params.useCount == 1) || !isWithinFunction)
+            emplaceType<BoundType>(asMutable(freeTy), builtinTypes->unknownType);
+        else
+        {
+            emplaceType<GenericType>(asMutable(freeTy), scope, params.polarity);
+            return freeTy;
+        }
+    }
+    // It is possible that this free type has other free types in its upper
+    // or lower bounds.  If this is the case, we must replace those
+    // references with never (for the lower bound) or unknown (for the upper
+    // bound).
+    //
+    // If we do not do this, we get tautological bounds like a <: a <: unknown.
+    else if (isPositive(params.polarity) && !hasUpperBound)
+    {
+        TypeId lb = follow(ft->lowerBound);
+        if (FreeType* lowerFree = getMutable<FreeType>(lb); lowerFree && lowerFree->upperBound == freeTy)
+            lowerFree->upperBound = builtinTypes->unknownType;
+        else
+        {
+            DenseHashSet<TypeId> replaceSeen{nullptr};
+            lb = removeType(arena, builtinTypes, replaceSeen, lb, freeTy);
+            ft->lowerBound = lb;
+        }
+
+        if (follow(lb) != freeTy)
+            emplaceType<BoundType>(asMutable(freeTy), lb);
+        else if (!isWithinFunction || params.useCount == 1)
+            emplaceType<BoundType>(asMutable(freeTy), builtinTypes->unknownType);
+        else
+        {
+            // if the lower bound is the type in question (eg 'a <: 'a), we don't actually have a lower bound.
+            emplaceType<GenericType>(asMutable(freeTy), scope, params.polarity);
+            return freeTy;
+        }
+    }
+    else
+    {
+        TypeId ub = follow(ft->upperBound);
+        if (FreeType* upperFree = getMutable<FreeType>(ub); upperFree && upperFree->lowerBound == freeTy)
+            upperFree->lowerBound = builtinTypes->neverType;
+        else
+        {
+            // If the free type appears within its own upper bound, cull that cycle.
+            DenseHashSet<TypeId> replaceSeen{nullptr};
+            ub = removeType(arena, builtinTypes, replaceSeen, ub, freeTy);
+            ft->upperBound = ub;
+        }
+
+        if (follow(ub) != freeTy)
+            emplaceType<BoundType>(asMutable(freeTy), ub);
+        else if (!isWithinFunction || params.useCount == 1)
+            emplaceType<BoundType>(asMutable(freeTy), builtinTypes->unknownType);
+        else
+        {
+            // if the upper bound is the type in question, we don't actually have an upper bound.
+            emplaceType<GenericType>(asMutable(freeTy), scope, params.polarity);
+            return freeTy;
+        }
+    }
+
+    return std::nullopt;
+}
+
+std::optional<TypePackId> generalizeTypePack(
+    NotNull<TypeArena> arena,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Scope> scope,
+    TypePackId tp,
+    const GeneralizationParams<TypePackId>& params
+)
+{
+    tp = follow(tp);
+
+    if (tp->owningArena != arena)
+        return std::nullopt;
+
+    const FreeTypePack* ftp = get<FreeTypePack>(tp);
+    if (!ftp)
+        return std::nullopt;
+
+    if (!subsumes(scope, ftp->scope))
+        return std::nullopt;
+
+    if (1 == params.useCount)
+        emplaceTypePack<BoundTypePack>(asMutable(tp), builtinTypes->unknownTypePack);
+    else
+    {
+        emplaceTypePack<GenericTypePack>(asMutable(tp), scope, params.polarity);
+        return tp;
+    }
+
+    return std::nullopt;
+}
+
+void sealTable(NotNull<Scope> scope, TypeId ty)
+{
+    TableType* tableTy = getMutable<TableType>(follow(ty));
+    if (!tableTy)
+        return;
+
+    if (!subsumes(scope, tableTy->scope))
+        return;
+
+    if (tableTy->state == TableState::Unsealed || tableTy->state == TableState::Free)
+        tableTy->state = TableState::Sealed;
+}
+
 std::optional<TypeId> generalize(
     NotNull<TypeArena> arena,
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<Scope> scope,
     NotNull<DenseHashSet<TypeId>> cachedTypes,
-    TypeId ty,
+    TypeId ty
-    bool avoidSealingTables
 )
 {
     ty = follow(ty);
@@ -984,35 +1323,74 @@ std::optional<TypeId> generalize(
     FreeTypeSearcher fts{scope, cachedTypes};
     fts.traverse(ty);
 
-    MutatingGeneralizer gen{arena, builtinTypes, scope, cachedTypes, std::move(fts.positiveTypes), std::move(fts.negativeTypes), avoidSealingTables};
+    if (FFlag::LuauNonReentrantGeneralization)
-
-    gen.traverse(ty);
-
-    /* MutatingGeneralizer mutates types in place, so it is possible that ty has
-     * been transmuted to a BoundType. We must follow it again and verify that
-     * we are allowed to mutate it before we attach generics to it.
-     */
-    ty = follow(ty);
-
-    if (ty->owningArena != arena || ty->persistent)
-        return ty;
-
-    TypeCacher cacher{cachedTypes};
-    cacher.traverse(ty);
-
-    FunctionType* ftv = getMutable<FunctionType>(ty);
-    if (ftv)
     {
-        // If we're generalizing a function type, add any of the newly inferred
+        FunctionType* functionTy = getMutable<FunctionType>(ty);
-        // generics to the list of existing generic types.
+        auto pushGeneric = [&](TypeId t)
-        for (const auto g : std::move(gen.generics))
         {
-            ftv->generics.push_back(g);
+            if (functionTy)
+                functionTy->generics.push_back(t);
+        };
+
+        auto pushGenericPack = [&](TypePackId tp)
+        {
+            if (functionTy)
+                functionTy->genericPacks.push_back(tp);
+        };
+
+        for (const auto& [freeTy, params] : fts.types)
+        {
+            if (std::optional<TypeId> genericTy = generalizeType(arena, builtinTypes, scope, freeTy, params))
+                pushGeneric(*genericTy);
         }
-        // Ditto for generic packs.
+
-        for (const auto gp : std::move(gen.genericPacks))
+        for (TypeId unsealedTableTy : fts.unsealedTables)
+            sealTable(scope, unsealedTableTy);
+
+        for (const auto& [freePackId, params] : fts.typePacks)
         {
-            ftv->genericPacks.push_back(gp);
+            TypePackId freePack = follow(freePackId);
+            std::optional<TypePackId> generalizedTp = generalizeTypePack(arena, builtinTypes, scope, freePack, params);
+
+            if (generalizedTp)
+                pushGenericPack(freePack);
+        }
+
+        TypeCacher cacher{cachedTypes};
+        cacher.traverse(ty);
+    }
+    else
+    {
+        MutatingGeneralizer gen{arena, builtinTypes, scope, cachedTypes, std::move(fts.positiveTypes), std::move(fts.negativeTypes)};
+
+        gen.traverse(ty);
+
+        /* MutatingGeneralizer mutates types in place, so it is possible that ty has
+         * been transmuted to a BoundType. We must follow it again and verify that
+         * we are allowed to mutate it before we attach generics to it.
+         */
+        ty = follow(ty);
+
+        if (ty->owningArena != arena || ty->persistent)
+            return ty;
+
+        TypeCacher cacher{cachedTypes};
+        cacher.traverse(ty);
+
+        FunctionType* ftv = getMutable<FunctionType>(ty);
+        if (ftv)
+        {
+            // If we're generalizing a function type, add any of the newly inferred
+            // generics to the list of existing generic types.
+            for (const auto g : std::move(gen.generics))
+            {
+                ftv->generics.push_back(g);
+            }
+            // Ditto for generic packs.
+            for (const auto gp : std::move(gen.genericPacks))
+            {
+                ftv->genericPacks.push_back(gp);
+            }
         }
     }
 

Analysis/src/GlobalTypes.cpp

@@ -9,6 +9,7 @@ GlobalTypes::GlobalTypes(NotNull<BuiltinTypes> builtinTypes)
     : builtinTypes(builtinTypes)
 {
     globalScope = std::make_shared<Scope>(globalTypes.addTypePack(TypePackVar{FreeTypePack{TypeLevel{}}}));
+    globalTypeFunctionScope = std::make_shared<Scope>(globalTypes.addTypePack(TypePackVar{FreeTypePack{TypeLevel{}}}));
 
     globalScope->addBuiltinTypeBinding("any", TypeFun{{}, builtinTypes->anyType});
     globalScope->addBuiltinTypeBinding("nil", TypeFun{{}, builtinTypes->nilType});

Analysis/src/InferPolarity.cpp

@@ -0,0 +1,169 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/DenseHash.h"
+#include "Luau/Polarity.h"
+#include "Luau/Scope.h"
+#include "Luau/VisitType.h"
+
+LUAU_FASTFLAG(LuauNonReentrantGeneralization)
+
+namespace Luau
+{
+
+struct InferPolarity : TypeVisitor
+{
+    NotNull<TypeArena> arena;
+    NotNull<Scope> scope;
+
+    DenseHashMap<TypeId, Polarity> types{nullptr};
+    DenseHashMap<TypePackId, Polarity> packs{nullptr};
+
+    Polarity polarity = Polarity::Positive;
+
+    explicit InferPolarity(NotNull<TypeArena> arena, NotNull<Scope> scope)
+        : arena(arena)
+        , scope(scope)
+    {
+    }
+
+    void flip()
+    {
+        polarity = invert(polarity);
+    }
+
+    bool visit(TypeId ty, const GenericType& gt) override
+    {
+        if (ty->owningArena != arena)
+            return false;
+
+        if (subsumes(scope, gt.scope))
+            types[ty] |= polarity;
+
+        return false;
+    }
+
+    bool visit(TypeId ty, const TableType& tt) override
+    {
+        if (ty->owningArena != arena)
+            return false;
+
+        const Polarity p = polarity;
+        for (const auto& [name, prop] : tt.props)
+        {
+            if (prop.isShared())
+            {
+                polarity = Polarity::Mixed;
+                traverse(prop.type());
+            }
+            else if (prop.isReadOnly())
+            {
+                polarity = p;
+                traverse(*prop.readTy);
+            }
+            else if (prop.isWriteOnly())
+            {
+                polarity = invert(p);
+                traverse(*prop.writeTy);
+            }
+            else
+                LUAU_ASSERT(!"Unreachable");
+        }
+
+        if (tt.indexer)
+        {
+            polarity = Polarity::Mixed;
+            traverse(tt.indexer->indexType);
+            traverse(tt.indexer->indexResultType);
+        }
+
+        polarity = p;
+
+        return false;
+    }
+
+    bool visit(TypeId ty, const FunctionType& ft) override
+    {
+        if (ty->owningArena != arena)
+            return false;
+
+        const Polarity p = polarity;
+
+        polarity = Polarity::Positive;
+
+        // If these types actually occur within the function signature, their
+        // polarity will be overwritten. If not, we infer that they are phantom
+        // types.
+        for (TypeId generic : ft.generics)
+        {
+            const auto gen = get<GenericType>(generic);
+            LUAU_ASSERT(gen);
+            if (subsumes(scope, gen->scope))
+                types[generic] = Polarity::None;
+        }
+        for (TypePackId genericPack : ft.genericPacks)
+        {
+            const auto gen = get<GenericTypePack>(genericPack);
+            LUAU_ASSERT(gen);
+            if (subsumes(scope, gen->scope))
+                packs[genericPack] = Polarity::None;
+        }
+
+        flip();
+        traverse(ft.argTypes);
+        flip();
+        traverse(ft.retTypes);
+
+        polarity = p;
+
+        return false;
+    }
+
+    bool visit(TypeId, const ClassType&) override
+    {
+        return false;
+    }
+
+    bool visit(TypePackId tp, const GenericTypePack& gtp) override
+    {
+        packs[tp] |= polarity;
+        return false;
+    }
+};
+
+template<typename TID>
+static void inferGenericPolarities_(NotNull<TypeArena> arena, NotNull<Scope> scope, TID ty)
+{
+    if (!FFlag::LuauNonReentrantGeneralization)
+        return;
+
+    InferPolarity infer{arena, scope};
+    infer.traverse(ty);
+
+    for (const auto& [ty, polarity] : infer.types)
+    {
+        auto gt = getMutable<GenericType>(ty);
+        LUAU_ASSERT(gt);
+        gt->polarity = polarity;
+    }
+
+    for (const auto& [tp, polarity] : infer.packs)
+    {
+        if (tp->owningArena != arena)
+            continue;
+        auto gp = getMutable<GenericTypePack>(tp);
+        LUAU_ASSERT(gp);
+        gp->polarity = polarity;
+    }
+}
+
+void inferGenericPolarities(NotNull<TypeArena> arena, NotNull<Scope> scope, TypeId ty)
+{
+    inferGenericPolarities_(arena, scope, ty);
+}
+
+void inferGenericPolarities(NotNull<TypeArena> arena, NotNull<Scope> scope, TypePackId tp)
+{
+    inferGenericPolarities_(arena, scope, tp);
+}
+
+} // namespace Luau

Analysis/src/Instantiation.cpp

@@ -61,7 +61,7 @@ TypeId Instantiation::clean(TypeId ty)
     const FunctionType* ftv = log->getMutable<FunctionType>(ty);
     LUAU_ASSERT(ftv);
 
-    FunctionType clone = FunctionType{level, scope, ftv->argTypes, ftv->retTypes, ftv->definition, ftv->hasSelf};
+    FunctionType clone = FunctionType{level, ftv->argTypes, ftv->retTypes, ftv->definition, ftv->hasSelf};
     clone.magic = ftv->magic;
     clone.tags = ftv->tags;
     clone.argNames = ftv->argNames;

Analysis/src/Linter.cpp

@@ -19,6 +19,8 @@ LUAU_FASTFLAG(LuauSolverV2)
 LUAU_FASTFLAG(LuauAttribute)
 LUAU_FASTFLAGVARIABLE(LintRedundantNativeAttribute)
 
+LUAU_FASTFLAG(LuauDeprecatedAttribute)
+
 namespace Luau
 {
 
@@ -2280,6 +2282,57 @@ private:
     {
     }
 
+    bool visit(AstExprLocal* node) override
+    {
+        if (FFlag::LuauDeprecatedAttribute)
+        {
+
+            const FunctionType* fty = getFunctionType(node);
+            bool shouldReport = fty && fty->isDeprecatedFunction && !inScope(fty);
+
+            if (shouldReport)
+                report(node->location, node->local->name.value);
+        }
+
+        return true;
+    }
+
+    bool visit(AstExprGlobal* node) override
+    {
+        if (FFlag::LuauDeprecatedAttribute)
+        {
+            const FunctionType* fty = getFunctionType(node);
+            bool shouldReport = fty && fty->isDeprecatedFunction && !inScope(fty);
+
+            if (shouldReport)
+                report(node->location, node->name.value);
+        }
+
+        return true;
+    }
+
+    bool visit(AstStatLocalFunction* node) override
+    {
+        if (FFlag::LuauDeprecatedAttribute)
+        {
+            check(node->func);
+            return false;
+        }
+        else
+            return true;
+    }
+
+    bool visit(AstStatFunction* node) override
+    {
+        if (FFlag::LuauDeprecatedAttribute)
+        {
+            check(node->func);
+            return false;
+        }
+        else
+            return true;
+    }
+
     bool visit(AstExprIndexName* node) override
     {
         if (std::optional<TypeId> ty = context->getType(node->expr))
@@ -2325,18 +2378,59 @@ private:
 
             if (prop && prop->deprecated)
                 report(node->location, *prop, cty->name.c_str(), node->index.value);
+            else if (FFlag::LuauDeprecatedAttribute && prop)
+            {
+                if (std::optional<TypeId> ty = prop->readTy)
+                {
+                    const FunctionType* fty = get<FunctionType>(follow(ty));
+                    bool shouldReport = fty && fty->isDeprecatedFunction && !inScope(fty);
+
+                    if (shouldReport)
+                    {
+                        const char* className = nullptr;
+                        if (AstExprGlobal* global = node->expr->as<AstExprGlobal>())
+                            className = global->name.value;
+
+                        const char* functionName = node->index.value;
+
+                        report(node->location, className, functionName);
+                    }
+                }
+            }
         }
         else if (const TableType* tty = get<TableType>(ty))
         {
             auto prop = tty->props.find(node->index.value);
 
-            if (prop != tty->props.end() && prop->second.deprecated)
+            if (prop != tty->props.end())
             {
-                // strip synthetic typeof() for builtin tables
+                if (prop->second.deprecated)
-                if (tty->name && tty->name->compare(0, 7, "typeof(") == 0 && tty->name->back() == ')')
+                {
-                    report(node->location, prop->second, tty->name->substr(7, tty->name->length() - 8).c_str(), node->index.value);
+                    // strip synthetic typeof() for builtin tables
-                else
+                    if (tty->name && tty->name->compare(0, 7, "typeof(") == 0 && tty->name->back() == ')')
-                    report(node->location, prop->second, tty->name ? tty->name->c_str() : nullptr, node->index.value);
+                        report(node->location, prop->second, tty->name->substr(7, tty->name->length() - 8).c_str(), node->index.value);
+                    else
+                        report(node->location, prop->second, tty->name ? tty->name->c_str() : nullptr, node->index.value);
+                }
+                else if (FFlag::LuauDeprecatedAttribute)
+                {
+                    if (std::optional<TypeId> ty = prop->second.readTy)
+                    {
+                        const FunctionType* fty = get<FunctionType>(follow(ty));
+                        bool shouldReport = fty && fty->isDeprecatedFunction && !inScope(fty);
+
+                        if (shouldReport)
+                        {
+                            const char* className = nullptr;
+                            if (AstExprGlobal* global = node->expr->as<AstExprGlobal>())
+                                className = global->name.value;
+
+                            const char* functionName = node->index.value;
+
+                            report(node->location, className, functionName);
+                        }
+                    }
+                }
             }
         }
     }
@@ -2355,6 +2449,26 @@ private:
         }
     }
 
+    void check(AstExprFunction* func)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+        LUAU_ASSERT(func);
+
+        const FunctionType* fty = getFunctionType(func);
+        bool isDeprecated = fty && fty->isDeprecatedFunction;
+
+        // If a function is deprecated, we don't want to flag its recursive uses.
+        // So we push it on a stack while its body is being analyzed.
+        // When a deprecated function is used, we check the stack to ensure that we are not inside that function.
+        if (isDeprecated)
+            pushScope(fty);
+
+        func->visit(this);
+
+        if (isDeprecated)
+            popScope(fty);
+    }
+
     void report(const Location& location, const Property& prop, const char* container, const char* field)
     {
         std::string suggestion = prop.deprecatedSuggestion.empty() ? "" : format(", use '%s' instead", prop.deprecatedSuggestion.c_str());
@@ -2364,6 +2478,63 @@ private:
         else
             emitWarning(*context, LintWarning::Code_DeprecatedApi, location, "Member '%s' is deprecated%s", field, suggestion.c_str());
     }
+
+    void report(const Location& location, const char* tableName, const char* functionName)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+        if (tableName)
+            emitWarning(*context, LintWarning::Code_DeprecatedApi, location, "Member '%s.%s' is deprecated", tableName, functionName);
+        else
+            emitWarning(*context, LintWarning::Code_DeprecatedApi, location, "Member '%s' is deprecated", functionName);
+    }
+
+    void report(const Location& location, const char* functionName)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+        emitWarning(*context, LintWarning::Code_DeprecatedApi, location, "Function '%s' is deprecated", functionName);
+    }
+
+    std::vector<const FunctionType*> functionTypeScopeStack;
+
+    void pushScope(const FunctionType* fty)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+        LUAU_ASSERT(fty);
+
+        functionTypeScopeStack.push_back(fty);
+    }
+
+    void popScope(const FunctionType* fty)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+        LUAU_ASSERT(fty);
+
+        LUAU_ASSERT(fty == functionTypeScopeStack.back());
+        functionTypeScopeStack.pop_back();
+    }
+
+    bool inScope(const FunctionType* fty) const
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+        LUAU_ASSERT(fty);
+
+        return std::find(functionTypeScopeStack.begin(), functionTypeScopeStack.end(), fty) != functionTypeScopeStack.end();
+    }
+
+    const FunctionType* getFunctionType(AstExpr* node)
+    {
+        LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+        std::optional<TypeId> ty = context->getType(node);
+        if (!ty)
+            return nullptr;
+
+        const FunctionType* fty = get<FunctionType>(follow(ty));
+
+        return fty;
+    }
 };
 
 class LintTableOperations : AstVisitor

Analysis/src/Module.cpp

@@ -15,12 +15,12 @@
 #include <algorithm>
 
 LUAU_FASTFLAG(LuauSolverV2);
-LUAU_FASTFLAGVARIABLE(LuauIncrementalAutocompleteCommentDetection)
+LUAU_FASTFLAG(LuauRetainDefinitionAliasLocations)
 
 namespace Luau
 {
 
-static void defaultLogLuau(std::string_view input)
+static void defaultLogLuau(std::string_view context, std::string_view input)
 {
     // The default is to do nothing because we don't want to mess with
     // the xml parsing done by the dcr script.
@@ -38,21 +38,6 @@ void resetLogLuauProc()
     logLuau = &defaultLogLuau;
 }
 
-
-
-static bool contains_DEPRECATED(Position pos, Comment comment)
-{
-    if (comment.location.contains(pos))
-        return true;
-    else if (comment.type == Lexeme::BrokenComment && comment.location.begin <= pos) // Broken comments are broken specifically because they don't
-                                                                                     // have an end
-        return true;
-    else if (comment.type == Lexeme::Comment && comment.location.end == pos)
-        return true;
-    else
-        return false;
-}
-
 static bool contains(Position pos, Comment comment)
 {
     if (comment.location.contains(pos))
@@ -76,11 +61,8 @@ bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos)
         Comment{Lexeme::Comment, Location{pos, pos}},
         [](const Comment& a, const Comment& b)
         {
-            if (FFlag::LuauIncrementalAutocompleteCommentDetection)
+            if (a.type == Lexeme::Comment)
-            {
+                return a.location.end.line < b.location.end.line;
-                if (a.type == Lexeme::Comment)
-                    return a.location.end.line < b.location.end.line;
-            }
             return a.location.end < b.location.end;
         }
     );
@@ -88,7 +70,7 @@ bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos)
     if (iter == commentLocations.end())
         return false;
 
-    if (FFlag::LuauIncrementalAutocompleteCommentDetection ? contains(pos, *iter) : contains_DEPRECATED(pos, *iter))
+    if (contains(pos, *iter))
         return true;
 
     // Due to the nature of std::lower_bound, it is possible that iter points at a comment that ends
@@ -172,8 +154,6 @@ struct ClonePublicInterface : Substitution
             }
 
             ftv->level = TypeLevel{0, 0};
-            if (FFlag::LuauSolverV2)
-                ftv->scope = nullptr;
         }
         else if (TableType* ttv = getMutable<TableType>(result))
         {
@@ -285,7 +265,10 @@ struct ClonePublicInterface : Substitution
 
         TypeId type = cloneType(tf.type);
 
-        return TypeFun{typeParams, typePackParams, type};
+        if (FFlag::LuauRetainDefinitionAliasLocations)
+            return TypeFun{typeParams, typePackParams, type, tf.definitionLocation};
+        else
+            return TypeFun{typeParams, typePackParams, type};
     }
 };
 

Analysis/src/NonStrictTypeChecker.cpp

@@ -2,6 +2,7 @@
 #include "Luau/NonStrictTypeChecker.h"
 
 #include "Luau/Ast.h"
+#include "Luau/AstQuery.h"
 #include "Luau/Common.h"
 #include "Luau/Simplify.h"
 #include "Luau/Type.h"
@@ -22,6 +23,7 @@
 LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
 LUAU_FASTFLAGVARIABLE(LuauNonStrictVisitorImprovements)
 LUAU_FASTFLAGVARIABLE(LuauNewNonStrictWarnOnUnknownGlobals)
+LUAU_FASTFLAGVARIABLE(LuauNonStrictFuncDefErrorFix)
 
 namespace Luau
 {
@@ -763,7 +765,17 @@ struct NonStrictTypeChecker
         for (AstLocal* local : exprFn->args)
         {
             if (std::optional<TypeId> ty = willRunTimeErrorFunctionDefinition(local, remainder))
-                reportError(NonStrictFunctionDefinitionError{exprFn->debugname.value, local->name.value, *ty}, local->location);
+            {
+                if (FFlag::LuauNonStrictFuncDefErrorFix)
+                {
+                    const char* debugname = exprFn->debugname.value;
+                    reportError(NonStrictFunctionDefinitionError{debugname ? debugname : "", local->name.value, *ty}, local->location);
+                }
+                else
+                {
+                    reportError(NonStrictFunctionDefinitionError{exprFn->debugname.value, local->name.value, *ty}, local->location);
+                }
+            }
             remainder.remove(dfg->getDef(local));
         }
         return remainder;

Analysis/src/Normalize.cpp

@@ -17,11 +17,16 @@
 
 LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant)
 
+LUAU_FASTFLAGVARIABLE(LuauNormalizeNegatedErrorToAnError)
+LUAU_FASTFLAGVARIABLE(LuauNormalizeIntersectErrorToAnError)
 LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000)
 LUAU_FASTINTVARIABLE(LuauNormalizeIntersectionLimit, 200)
+LUAU_FASTINTVARIABLE(LuauNormalizeUnionLimit, 100)
 LUAU_FASTFLAG(LuauSolverV2)
 LUAU_FASTFLAGVARIABLE(LuauFixInfiniteRecursionInNormalization)
-LUAU_FASTFLAGVARIABLE(LuauFixNormalizedIntersectionOfNegatedClass)
+LUAU_FASTFLAGVARIABLE(LuauNormalizedBufferIsNotUnknown)
+LUAU_FASTFLAGVARIABLE(LuauNormalizeLimitFunctionSet)
+LUAU_FASTFLAGVARIABLE(LuauNormalizationCatchMetatableCycles)
 
 namespace Luau
 {
@@ -303,7 +308,9 @@ bool NormalizedType::isUnknown() const
 
     // Otherwise, we can still be unknown!
     bool hasAllPrimitives = isPrim(booleans, PrimitiveType::Boolean) && isPrim(nils, PrimitiveType::NilType) && isNumber(numbers) &&
-                            strings.isString() && isPrim(threads, PrimitiveType::Thread) && isThread(threads);
+                            strings.isString() &&
+                            (FFlag::LuauNormalizedBufferIsNotUnknown ? isThread(threads) && isBuffer(buffers)
+                                                                     : isPrim(threads, PrimitiveType::Thread) && isThread(threads));
 
     // Check is class
     bool isTopClass = false;
@@ -578,7 +585,7 @@ NormalizationResult Normalizer::isIntersectionInhabited(TypeId left, TypeId righ
 {
     left = follow(left);
     right = follow(right);
-    // We're asking if intersection is inahbited between left and right but we've already seen them ....
+    // We're asking if intersection is inhabited between left and right but we've already seen them ....
 
     if (cacheInhabitance)
     {
@@ -1684,6 +1691,13 @@ NormalizationResult Normalizer::unionNormals(NormalizedType& here, const Normali
             return res;
     }
 
+    if (FFlag::LuauNormalizeLimitFunctionSet)
+    {
+        // Limit based on worst-case expansion of the function unions
+        if (here.functions.parts.size() * there.functions.parts.size() >= size_t(FInt::LuauNormalizeUnionLimit))
+            return NormalizationResult::HitLimits;
+    }
+
     here.booleans = unionOfBools(here.booleans, there.booleans);
     unionClasses(here.classes, there.classes);
 
@@ -1695,6 +1709,7 @@ NormalizationResult Normalizer::unionNormals(NormalizedType& here, const Normali
     here.buffers = (get<NeverType>(there.buffers) ? here.buffers : there.buffers);
     unionFunctions(here.functions, there.functions);
     unionTables(here.tables, there.tables);
+
     return NormalizationResult::True;
 }
 
@@ -1734,7 +1749,7 @@ NormalizationResult Normalizer::intersectNormalWithNegationTy(TypeId toNegate, N
     return NormalizationResult::True;
 }
 
-// See above for an explaination of `ignoreSmallerTyvars`.
+// See above for an explanation of `ignoreSmallerTyvars`.
 NormalizationResult Normalizer::unionNormalWithTy(
     NormalizedType& here,
     TypeId there,
@@ -2288,7 +2303,7 @@ void Normalizer::intersectClassesWithClass(NormalizedClassType& heres, TypeId th
 
             for (auto nIt = negations.begin(); nIt != negations.end();)
             {
-                if (FFlag::LuauFixNormalizedIntersectionOfNegatedClass && isSubclass(there, *nIt))
+                if (isSubclass(there, *nIt))
                 {
                     // Hitting this block means that the incoming class is a
                     // subclass of this type, _and_ one of its negations is a
@@ -3049,7 +3064,7 @@ NormalizationResult Normalizer::intersectTyvarsWithTy(
     return NormalizationResult::True;
 }
 
-// See above for an explaination of `ignoreSmallerTyvars`.
+// See above for an explanation of `ignoreSmallerTyvars`.
 NormalizationResult Normalizer::intersectNormals(NormalizedType& here, const NormalizedType& there, int ignoreSmallerTyvars)
 {
     RecursionCounter _rc(&sharedState->counters.recursionCount);
@@ -3067,11 +3082,17 @@ NormalizationResult Normalizer::intersectNormals(NormalizedType& here, const Nor
         return unionNormals(here, there, ignoreSmallerTyvars);
     }
 
-    // Limit based on worst-case expansion of the table intersection
+    // Limit based on worst-case expansion of the table/function intersections
     // This restriction can be relaxed when table intersection simplification is improved
     if (here.tables.size() * there.tables.size() >= size_t(FInt::LuauNormalizeIntersectionLimit))
         return NormalizationResult::HitLimits;
 
+    if (FFlag::LuauNormalizeLimitFunctionSet)
+    {
+        if (here.functions.parts.size() * there.functions.parts.size() >= size_t(FInt::LuauNormalizeIntersectionLimit))
+            return NormalizationResult::HitLimits;
+    }
+
     here.booleans = intersectionOfBools(here.booleans, there.booleans);
 
     intersectClasses(here.classes, there.classes);
@@ -3207,7 +3228,7 @@ NormalizationResult Normalizer::intersectNormalWithTy(
     {
         TypeId errors = here.errors;
         clearNormal(here);
-        here.errors = errors;
+        here.errors = FFlag::LuauNormalizeIntersectErrorToAnError && get<ErrorType>(errors) ? errors : there;
     }
     else if (const PrimitiveType* ptv = get<PrimitiveType>(there))
     {
@@ -3304,8 +3325,18 @@ NormalizationResult Normalizer::intersectNormalWithTy(
             clearNormal(here);
             return NormalizationResult::True;
         }
+        else if (FFlag::LuauNormalizeNegatedErrorToAnError && get<ErrorType>(t))
+        {
+            // ~error is still an error, so intersecting with the negation is the same as intersecting with a type
+            TypeId errors = here.errors;
+            clearNormal(here);
+            here.errors = FFlag::LuauNormalizeIntersectErrorToAnError && get<ErrorType>(errors) ? errors : t;
+        }
         else if (auto nt = get<NegationType>(t))
+        {
+            here.tyvars = std::move(tyvars);
             return intersectNormalWithTy(here, nt->ty, seenTablePropPairs, seenSetTypes);
+        }
         else
         {
             // TODO negated unions, intersections, table, and function.
@@ -3333,7 +3364,7 @@ NormalizationResult Normalizer::intersectNormalWithTy(
     return NormalizationResult::True;
 }
 
-void makeTableShared(TypeId ty)
+void makeTableShared_DEPRECATED(TypeId ty)
 {
     ty = follow(ty);
     if (auto tableTy = getMutable<TableType>(ty))
@@ -3343,11 +3374,35 @@ void makeTableShared(TypeId ty)
     }
     else if (auto metatableTy = get<MetatableType>(ty))
     {
-        makeTableShared(metatableTy->metatable);
+        makeTableShared_DEPRECATED(metatableTy->metatable);
-        makeTableShared(metatableTy->table);
+        makeTableShared_DEPRECATED(metatableTy->table);
     }
 }
 
+void makeTableShared(TypeId ty, DenseHashSet<TypeId>& seen)
+{
+    ty = follow(ty);
+    if (seen.contains(ty))
+        return;
+    seen.insert(ty);
+    if (auto tableTy = getMutable<TableType>(ty))
+    {
+        for (auto& [_, prop] : tableTy->props)
+            prop.makeShared();
+    }
+    else if (auto metatableTy = get<MetatableType>(ty))
+    {
+        makeTableShared(metatableTy->metatable, seen);
+        makeTableShared(metatableTy->table, seen);
+    }
+}
+
+void makeTableShared(TypeId ty)
+{
+    DenseHashSet<TypeId> seen{nullptr};
+    makeTableShared(ty, seen);
+}
+
 // -------- Convert back from a normalized type to a type
 TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
 {
@@ -3447,7 +3502,10 @@ TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
         result.reserve(result.size() + norm.tables.size());
         for (auto table : norm.tables)
         {
-            makeTableShared(table);
+            if (FFlag::LuauNormalizationCatchMetatableCycles)
+                makeTableShared(table);
+            else
+                makeTableShared_DEPRECATED(table);
             result.push_back(table);
         }
     }

Analysis/src/OverloadResolution.cpp

@@ -454,7 +454,7 @@ SolveResult solveFunctionCall(
 
     TypePackId resultPack = arena->freshTypePack(scope);
 
-    TypeId inferredTy = arena->addType(FunctionType{TypeLevel{}, scope.get(), argsPack, resultPack});
+    TypeId inferredTy = arena->addType(FunctionType{TypeLevel{}, argsPack, resultPack});
     Unifier2 u2{NotNull{arena}, builtinTypes, scope, iceReporter};
 
     const bool occursCheckPassed = u2.unify(*overloadToUse, inferredTy);

Analysis/src/Quantify.cpp

@@ -107,134 +107,4 @@ void quantify(TypeId ty, TypeLevel level)
     ftv->genericPacks.insert(ftv->genericPacks.end(), q.genericPacks.begin(), q.genericPacks.end());
 }
 
-struct PureQuantifier : Substitution
-{
-    Scope* scope;
-    OrderedMap<TypeId, TypeId> insertedGenerics;
-    OrderedMap<TypePackId, TypePackId> insertedGenericPacks;
-    bool seenMutableType = false;
-    bool seenGenericType = false;
-
-    PureQuantifier(TypeArena* arena, Scope* scope)
-        : Substitution(TxnLog::empty(), arena)
-        , scope(scope)
-    {
-    }
-
-    bool isDirty(TypeId ty) override
-    {
-        LUAU_ASSERT(ty == follow(ty));
-
-        if (auto ftv = get<FreeType>(ty))
-        {
-            bool result = subsumes(scope, ftv->scope);
-            seenMutableType |= result;
-            return result;
-        }
-        else if (auto ttv = get<TableType>(ty))
-        {
-            if (ttv->state == TableState::Free)
-                seenMutableType = true;
-            else if (ttv->state == TableState::Generic)
-                seenGenericType = true;
-
-            return (ttv->state == TableState::Unsealed || ttv->state == TableState::Free) && subsumes(scope, ttv->scope);
-        }
-
-        return false;
-    }
-
-    bool isDirty(TypePackId tp) override
-    {
-        if (auto ftp = get<FreeTypePack>(tp))
-        {
-            return subsumes(scope, ftp->scope);
-        }
-
-        return false;
-    }
-
-    TypeId clean(TypeId ty) override
-    {
-        if (auto ftv = get<FreeType>(ty))
-        {
-            TypeId result = arena->addType(GenericType{scope});
-            insertedGenerics.push(ty, result);
-            return result;
-        }
-        else if (auto ttv = get<TableType>(ty))
-        {
-            TypeId result = arena->addType(TableType{});
-            TableType* resultTable = getMutable<TableType>(result);
-            LUAU_ASSERT(resultTable);
-
-            *resultTable = *ttv;
-            resultTable->level = TypeLevel{};
-            resultTable->scope = scope;
-
-            if (ttv->state == TableState::Free)
-            {
-                resultTable->state = TableState::Generic;
-                insertedGenerics.push(ty, result);
-            }
-            else if (ttv->state == TableState::Unsealed)
-                resultTable->state = TableState::Sealed;
-
-            return result;
-        }
-
-        return ty;
-    }
-
-    TypePackId clean(TypePackId tp) override
-    {
-        if (auto ftp = get<FreeTypePack>(tp))
-        {
-            TypePackId result = arena->addTypePack(TypePackVar{GenericTypePack{scope}});
-            insertedGenericPacks.push(tp, result);
-            return result;
-        }
-
-        return tp;
-    }
-
-    bool ignoreChildren(TypeId ty) override
-    {
-        if (get<ClassType>(ty))
-            return true;
-
-        return ty->persistent;
-    }
-    bool ignoreChildren(TypePackId ty) override
-    {
-        return ty->persistent;
-    }
-};
-
-std::optional<QuantifierResult> quantify(TypeArena* arena, TypeId ty, Scope* scope)
-{
-    PureQuantifier quantifier{arena, scope};
-    std::optional<TypeId> result = quantifier.substitute(ty);
-    if (!result)
-        return std::nullopt;
-
-    FunctionType* ftv = getMutable<FunctionType>(*result);
-    LUAU_ASSERT(ftv);
-    ftv->scope = scope;
-
-    for (auto k : quantifier.insertedGenerics.keys)
-    {
-        TypeId g = quantifier.insertedGenerics.pairings[k];
-        if (get<GenericType>(g))
-            ftv->generics.push_back(g);
-    }
-
-    for (auto k : quantifier.insertedGenericPacks.keys)
-        ftv->genericPacks.push_back(quantifier.insertedGenericPacks.pairings[k]);
-
-    ftv->hasNoFreeOrGenericTypes = ftv->generics.empty() && ftv->genericPacks.empty() && !quantifier.seenGenericType && !quantifier.seenMutableType;
-
-    return std::optional<QuantifierResult>({*result, std::move(quantifier.insertedGenerics), std::move(quantifier.insertedGenericPacks)});
-}
-
 } // namespace Luau

Analysis/src/Refinement.cpp

@@ -54,7 +54,15 @@ RefinementId RefinementArena::proposition(const RefinementKey* key, TypeId discr
     if (!key)
         return nullptr;
 
-    return NotNull{allocator.allocate(Proposition{key, discriminantTy})};
+    return NotNull{allocator.allocate(Proposition{key, discriminantTy, false})};
+}
+
+RefinementId RefinementArena::implicitProposition(const RefinementKey* key, TypeId discriminantTy)
+{
+    if (!key)
+        return nullptr;
+
+    return NotNull{allocator.allocate(Proposition{key, discriminantTy, true})};
 }
 
 } // namespace Luau

Analysis/src/RequireTracer.cpp

@@ -4,8 +4,6 @@
 #include "Luau/Ast.h"
 #include "Luau/Module.h"
 
-LUAU_FASTFLAGVARIABLE(LuauExtendedSimpleRequire)
-
 namespace Luau
 {
 
@@ -106,96 +104,50 @@ struct RequireTracer : AstVisitor
     {
         ModuleInfo moduleContext{currentModuleName};
 
-        if (FFlag::LuauExtendedSimpleRequire)
+        // seed worklist with require arguments
+        work.reserve(requireCalls.size());
+
+        for (AstExprCall* require : requireCalls)
+            work.push_back(require->args.data[0]);
+
+        // push all dependent expressions to the work stack; note that the vector is modified during traversal
+        for (size_t i = 0; i < work.size(); ++i)
         {
-            // seed worklist with require arguments
+            if (AstNode* dep = getDependent(work[i]))
-            work.reserve(requireCalls.size());
+                work.push_back(dep);
-
-            for (AstExprCall* require : requireCalls)
-                work.push_back(require->args.data[0]);
-
-            // push all dependent expressions to the work stack; note that the vector is modified during traversal
-            for (size_t i = 0; i < work.size(); ++i)
-            {
-                if (AstNode* dep = getDependent(work[i]))
-                    work.push_back(dep);
-            }
-
-            // resolve all expressions to a module info
-            for (size_t i = work.size(); i > 0; --i)
-            {
-                AstNode* expr = work[i - 1];
-
-                // when multiple expressions depend on the same one we push it to work queue multiple times
-                if (result.exprs.contains(expr))
-                    continue;
-
-                std::optional<ModuleInfo> info;
-
-                if (AstNode* dep = getDependent(expr))
-                {
-                    const ModuleInfo* context = result.exprs.find(dep);
-
-                    if (context && expr->is<AstExprLocal>())
-                        info = *context; // locals just inherit their dependent context, no resolution required
-                    else if (context && (expr->is<AstExprGroup>() || expr->is<AstTypeGroup>()))
-                        info = *context; // simple group nodes propagate their value
-                    else if (context && (expr->is<AstTypeTypeof>() || expr->is<AstExprTypeAssertion>()))
-                        info = *context; // typeof type annotations will resolve to the typeof content
-                    else if (AstExpr* asExpr = expr->asExpr())
-                        info = fileResolver->resolveModule(context, asExpr);
-                }
-                else if (AstExpr* asExpr = expr->asExpr())
-                {
-                    info = fileResolver->resolveModule(&moduleContext, asExpr);
-                }
-
-                if (info)
-                    result.exprs[expr] = std::move(*info);
-            }
         }
-        else
+
+        // resolve all expressions to a module info
+        for (size_t i = work.size(); i > 0; --i)
         {
-            // seed worklist with require arguments
+            AstNode* expr = work[i - 1];
-            work_DEPRECATED.reserve(requireCalls.size());
 
-            for (AstExprCall* require : requireCalls)
+            // when multiple expressions depend on the same one we push it to work queue multiple times
-                work_DEPRECATED.push_back(require->args.data[0]);
+            if (result.exprs.contains(expr))
+                continue;
 
-            // push all dependent expressions to the work stack; note that the vector is modified during traversal
+            std::optional<ModuleInfo> info;
-            for (size_t i = 0; i < work_DEPRECATED.size(); ++i)
-                if (AstExpr* dep = getDependent_DEPRECATED(work_DEPRECATED[i]))
-                    work_DEPRECATED.push_back(dep);
 
-            // resolve all expressions to a module info
+            if (AstNode* dep = getDependent(expr))
-            for (size_t i = work_DEPRECATED.size(); i > 0; --i)
             {
-                AstExpr* expr = work_DEPRECATED[i - 1];
+                const ModuleInfo* context = result.exprs.find(dep);
 
-                // when multiple expressions depend on the same one we push it to work queue multiple times
+                if (context && expr->is<AstExprLocal>())
-                if (result.exprs.contains(expr))
+                    info = *context; // locals just inherit their dependent context, no resolution required
-                    continue;
+                else if (context && (expr->is<AstExprGroup>() || expr->is<AstTypeGroup>()))
-
+                    info = *context; // simple group nodes propagate their value
-                std::optional<ModuleInfo> info;
+                else if (context && (expr->is<AstTypeTypeof>() || expr->is<AstExprTypeAssertion>()))
-
+                    info = *context; // typeof type annotations will resolve to the typeof content
-                if (AstExpr* dep = getDependent_DEPRECATED(expr))
+                else if (AstExpr* asExpr = expr->asExpr())
-                {
+                    info = fileResolver->resolveModule(context, asExpr);
-                    const ModuleInfo* context = result.exprs.find(dep);
-
-                    // locals just inherit their dependent context, no resolution required
-                    if (expr->is<AstExprLocal>())
-                        info = context ? std::optional<ModuleInfo>(*context) : std::nullopt;
-                    else
-                        info = fileResolver->resolveModule(context, expr);
-                }
-                else
-                {
-                    info = fileResolver->resolveModule(&moduleContext, expr);
-                }
-
-                if (info)
-                    result.exprs[expr] = std::move(*info);
             }
+            else if (AstExpr* asExpr = expr->asExpr())
+            {
+                info = fileResolver->resolveModule(&moduleContext, asExpr);
+            }
+
+            if (info)
+                result.exprs[expr] = std::move(*info);
         }
 
         // resolve all requires according to their argument
@@ -224,7 +176,6 @@ struct RequireTracer : AstVisitor
     ModuleName currentModuleName;
 
     DenseHashMap<AstLocal*, AstExpr*> locals;
-    std::vector<AstExpr*> work_DEPRECATED;
     std::vector<AstNode*> work;
     std::vector<AstExprCall*> requireCalls;
 };

Analysis/src/Scope.cpp

@@ -84,6 +84,17 @@ std::optional<TypeId> Scope::lookupUnrefinedType(DefId def) const
     return std::nullopt;
 }
 
+std::optional<TypeId> Scope::lookupRValueRefinementType(DefId def) const
+{
+    for (const Scope* current = this; current; current = current->parent.get())
+    {
+        if (auto ty = current->rvalueRefinements.find(def))
+            return *ty;
+    }
+
+    return std::nullopt;
+}
+
 std::optional<TypeId> Scope::lookup(DefId def) const
 {
     for (const Scope* current = this; current; current = current->parent.get())
@@ -181,6 +192,29 @@ std::optional<Binding> Scope::linearSearchForBinding(const std::string& name, bo
     return std::nullopt;
 }
 
+std::optional<std::pair<Symbol, Binding>> Scope::linearSearchForBindingPair(const std::string& name, bool traverseScopeChain) const
+{
+    const Scope* scope = this;
+
+    while (scope)
+    {
+        for (auto& [n, binding] : scope->bindings)
+        {
+            if (n.local && n.local->name == name.c_str())
+                return {{n, binding}};
+            else if (n.global.value && n.global == name.c_str())
+                return {{n, binding}};
+        }
+
+        scope = scope->parent.get();
+
+        if (!traverseScopeChain)
+            break;
+    }
+
+    return std::nullopt;
+}
+
 // Updates the `this` scope with the assignments from the `childScope` including ones that doesn't exist in `this`.
 void Scope::inheritAssignments(const ScopePtr& childScope)
 {

Analysis/src/Substitution.cpp

@@ -13,6 +13,7 @@ LUAU_FASTINTVARIABLE(LuauTarjanChildLimit, 10000)
 LUAU_FASTFLAG(LuauSolverV2)
 LUAU_FASTINTVARIABLE(LuauTarjanPreallocationSize, 256)
 LUAU_FASTFLAG(LuauSyntheticErrors)
+LUAU_FASTFLAG(LuauDeprecatedAttribute)
 
 namespace Luau
 {
@@ -95,13 +96,15 @@ static TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool a
             return dest.addType(a);
         else if constexpr (std::is_same_v<T, FunctionType>)
         {
-            FunctionType clone = FunctionType{a.level, a.scope, a.argTypes, a.retTypes, a.definition, a.hasSelf};
+            FunctionType clone = FunctionType{a.level, a.argTypes, a.retTypes, a.definition, a.hasSelf};
             clone.generics = a.generics;
             clone.genericPacks = a.genericPacks;
             clone.magic = a.magic;
             clone.tags = a.tags;
             clone.argNames = a.argNames;
             clone.isCheckedFunction = a.isCheckedFunction;
+            if (FFlag::LuauDeprecatedAttribute)
+                clone.isDeprecatedFunction = a.isDeprecatedFunction;
             return dest.addType(std::move(clone));
         }
         else if constexpr (std::is_same_v<T, TableType>)

Analysis/src/Subtyping.cpp

@@ -22,7 +22,9 @@
 #include <algorithm>
 
 LUAU_FASTFLAGVARIABLE(DebugLuauSubtypingCheckPathValidity)
-LUAU_FASTFLAGVARIABLE(LuauSubtypingFixTailPack)
+LUAU_FASTFLAGVARIABLE(LuauSubtypingStopAtNormFail)
+LUAU_FASTINTVARIABLE(LuauSubtypingReasoningLimit, 100)
+LUAU_FASTFLAGVARIABLE(LuauSubtypingEnableReasoningLimit)
 
 namespace Luau
 {
@@ -100,6 +102,9 @@ static SubtypingReasonings mergeReasonings(const SubtypingReasonings& a, const S
             else
                 result.insert(r);
         }
+
+        if (FFlag::LuauSubtypingEnableReasoningLimit && result.size() >= size_t(FInt::LuauSubtypingReasoningLimit))
+            return result;
     }
 
     for (const SubtypingReasoning& r : b)
@@ -116,6 +121,9 @@ static SubtypingReasonings mergeReasonings(const SubtypingReasonings& a, const S
             else
                 result.insert(r);
         }
+
+        if (FFlag::LuauSubtypingEnableReasoningLimit && result.size() >= size_t(FInt::LuauSubtypingReasoningLimit))
+            return result;
     }
 
     return result;
@@ -416,6 +424,14 @@ SubtypingResult Subtyping::isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope
 
     SubtypingResult result = isCovariantWith(env, subTy, superTy, scope);
 
+    if (FFlag::LuauSubtypingStopAtNormFail && result.normalizationTooComplex)
+    {
+        if (result.isCacheable)
+            resultCache[{subTy, superTy}] = result;
+
+        return result;
+    }
+
     for (const auto& [subTy, bounds] : env.mappedGenerics)
     {
         const auto& lb = bounds.lowerBound;
@@ -593,7 +609,12 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypeId sub
         if (!result.isSubtype && !result.normalizationTooComplex)
         {
             SubtypingResult semantic = isCovariantWith(env, normalizer->normalize(subTy), normalizer->normalize(superTy), scope);
-            if (semantic.isSubtype)
+
+            if (FFlag::LuauSubtypingStopAtNormFail && semantic.normalizationTooComplex)
+            {
+                result = semantic;
+            }
+            else if (semantic.isSubtype)
             {
                 semantic.reasoning.clear();
                 result = semantic;
@@ -608,7 +629,12 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypeId sub
         if (!result.isSubtype && !result.normalizationTooComplex)
         {
             SubtypingResult semantic = isCovariantWith(env, normalizer->normalize(subTy), normalizer->normalize(superTy), scope);
-            if (semantic.isSubtype)
+
+            if (FFlag::LuauSubtypingStopAtNormFail && semantic.normalizationTooComplex)
+            {
+                result = semantic;
+            }
+            else if (semantic.isSubtype)
             {
                 // Clear the semantic reasoning, as any reasonings within
                 // potentially contain invalid paths.
@@ -754,7 +780,8 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
     // Match head types pairwise
 
     for (size_t i = 0; i < headSize; ++i)
-        results.push_back(isCovariantWith(env, subHead[i], superHead[i], scope).withBothComponent(TypePath::Index{i}));
+        results.push_back(isCovariantWith(env, subHead[i], superHead[i], scope).withBothComponent(TypePath::Index{i, TypePath::Index::Variant::Pack})
+        );
 
     // Handle mismatched head sizes
 
@@ -767,7 +794,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
                 for (size_t i = headSize; i < superHead.size(); ++i)
                     results.push_back(isCovariantWith(env, vt->ty, superHead[i], scope)
                                           .withSubPath(TypePath::PathBuilder().tail().variadic().build())
-                                          .withSuperComponent(TypePath::Index{i}));
+                                          .withSuperComponent(TypePath::Index{i, TypePath::Index::Variant::Pack}));
             }
             else if (auto gt = get<GenericTypePack>(*subTail))
             {
@@ -821,7 +848,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
             {
                 for (size_t i = headSize; i < subHead.size(); ++i)
                     results.push_back(isCovariantWith(env, subHead[i], vt->ty, scope)
-                                          .withSubComponent(TypePath::Index{i})
+                                          .withSubComponent(TypePath::Index{i, TypePath::Index::Variant::Pack})
                                           .withSuperPath(TypePath::PathBuilder().tail().variadic().build()));
             }
             else if (auto gt = get<GenericTypePack>(*superTail))
@@ -859,7 +886,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
             else
                 return SubtypingResult{false}
                     .withSuperComponent(TypePath::PackField::Tail)
-                    .withError({scope->location, UnexpectedTypePackInSubtyping{FFlag::LuauSubtypingFixTailPack ? *superTail : *subTail}});
+                    .withError({scope->location, UnexpectedTypePackInSubtyping{*superTail}});
         }
         else
             return {false};
@@ -1082,6 +1109,10 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypeId sub
     for (TypeId ty : superUnion)
     {
         SubtypingResult next = isCovariantWith(env, subTy, ty, scope);
+
+        if (FFlag::LuauSubtypingStopAtNormFail && next.normalizationTooComplex)
+            return SubtypingResult{false, /* normalizationTooComplex */ true};
+
         if (next.isSubtype)
             return SubtypingResult{true};
     }
@@ -1100,7 +1131,13 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const Unio
     std::vector<SubtypingResult> subtypings;
     size_t i = 0;
     for (TypeId ty : subUnion)
-        subtypings.push_back(isCovariantWith(env, ty, superTy, scope).withSubComponent(TypePath::Index{i++}));
+    {
+        subtypings.push_back(isCovariantWith(env, ty, superTy, scope).withSubComponent(TypePath::Index{i++, TypePath::Index::Variant::Union}));
+
+        if (FFlag::LuauSubtypingStopAtNormFail && subtypings.back().normalizationTooComplex)
+            return SubtypingResult{false, /* normalizationTooComplex */ true};
+    }
+
     return SubtypingResult::all(subtypings);
 }
 
@@ -1110,7 +1147,13 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypeId sub
     std::vector<SubtypingResult> subtypings;
     size_t i = 0;
     for (TypeId ty : superIntersection)
-        subtypings.push_back(isCovariantWith(env, subTy, ty, scope).withSuperComponent(TypePath::Index{i++}));
+    {
+        subtypings.push_back(isCovariantWith(env, subTy, ty, scope).withSuperComponent(TypePath::Index{i++, TypePath::Index::Variant::Intersection}));
+
+        if (FFlag::LuauSubtypingStopAtNormFail && subtypings.back().normalizationTooComplex)
+            return SubtypingResult{false, /* normalizationTooComplex */ true};
+    }
+
     return SubtypingResult::all(subtypings);
 }
 
@@ -1120,7 +1163,13 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const Inte
     std::vector<SubtypingResult> subtypings;
     size_t i = 0;
     for (TypeId ty : subIntersection)
-        subtypings.push_back(isCovariantWith(env, ty, superTy, scope).withSubComponent(TypePath::Index{i++}));
+    {
+        subtypings.push_back(isCovariantWith(env, ty, superTy, scope).withSubComponent(TypePath::Index{i++, TypePath::Index::Variant::Intersection}));
+
+        if (FFlag::LuauSubtypingStopAtNormFail && subtypings.back().normalizationTooComplex)
+            return SubtypingResult{false, /* normalizationTooComplex */ true};
+    }
+
     return SubtypingResult::any(subtypings);
 }
 
@@ -1410,7 +1459,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const Meta
         // of the supertype table.
         //
         // There's a flaw here in that if the __index metamethod contributes a new
-        // field that would satisfy the subtyping relationship, we'll erronously say
+        // field that would satisfy the subtyping relationship, we'll erroneously say
         // that the metatable isn't a subtype of the table, even though they have
         // compatible properties/shapes. We'll revisit this later when we have a
         // better understanding of how important this is.
@@ -1760,7 +1809,12 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const Type
     {
         results.emplace_back();
         for (TypeId superTy : superTypes)
+        {
             results.back().orElse(isCovariantWith(env, subTy, superTy, scope));
+
+            if (FFlag::LuauSubtypingStopAtNormFail && results.back().normalizationTooComplex)
+                return SubtypingResult{false, /* normalizationTooComplex */ true};
+        }
     }
 
     return SubtypingResult::all(results);

Analysis/src/Symbol.cpp

@@ -4,7 +4,6 @@
 #include "Luau/Common.h"
 
 LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAGVARIABLE(LuauSymbolEquality)
 
 namespace Luau
 {
@@ -15,10 +14,8 @@ bool Symbol::operator==(const Symbol& rhs) const
         return local == rhs.local;
     else if (global.value)
         return rhs.global.value && global == rhs.global.value; // Subtlety: AstName::operator==(const char*) uses strcmp, not pointer identity.
-    else if (FFlag::LuauSolverV2 || FFlag::LuauSymbolEquality)
-        return !rhs.local && !rhs.global.value; // Reflexivity: we already know `this` Symbol is empty, so check that rhs is.
     else
-        return false;
+        return !rhs.local && !rhs.global.value; // Reflexivity: we already know `this` Symbol is empty, so check that rhs is.
 }
 
 std::string toString(const Symbol& name)

Analysis/src/TableLiteralInference.cpp

@@ -1,16 +1,22 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 
+#include "Luau/TableLiteralInference.h"
+
 #include "Luau/Ast.h"
+#include "Luau/Common.h"
 #include "Luau/Normalize.h"
 #include "Luau/Simplify.h"
+#include "Luau/Subtyping.h"
 #include "Luau/Type.h"
 #include "Luau/ToString.h"
 #include "Luau/TypeArena.h"
 #include "Luau/TypeUtils.h"
 #include "Luau/Unifier2.h"
 
-LUAU_FASTFLAGVARIABLE(LuauDontInPlaceMutateTableType)
+LUAU_FASTFLAGVARIABLE(LuauBidirectionalInferenceUpcast)
-LUAU_FASTFLAGVARIABLE(LuauAllowNonSharedTableTypesInLiteral)
+LUAU_FASTFLAGVARIABLE(LuauBidirectionalInferenceCollectIndexerTypes)
+LUAU_FASTFLAGVARIABLE(LuauBidirectionalFailsafe)
+LUAU_FASTFLAGVARIABLE(LuauBidirectionalInferenceElideAssert)
 
 namespace Luau
 {
@@ -112,6 +118,7 @@ TypeId matchLiteralType(
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<TypeArena> arena,
     NotNull<Unifier2> unifier,
+    NotNull<Subtyping> subtyping,
     TypeId expectedType,
     TypeId exprType,
     const AstExpr* expr,
@@ -132,17 +139,38 @@ TypeId matchLiteralType(
      * things like replace explicit named properties with indexers as required
      * by the expected type.
      */
+
     if (!isLiteral(expr))
-        return exprType;
+    {
+        if (FFlag::LuauBidirectionalInferenceUpcast)
+        {
+            auto result = subtyping->isSubtype(/*subTy=*/exprType, /*superTy=*/expectedType, unifier->scope);
+            return result.isSubtype ? expectedType : exprType;
+        }
+        else
+            return exprType;
+    }
 
     expectedType = follow(expectedType);
     exprType = follow(exprType);
 
-    if (get<AnyType>(expectedType) || get<UnknownType>(expectedType))
+    if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
     {
-        // "Narrowing" to unknown or any is not going to do anything useful.
+        // The intent of `matchLiteralType` is to upcast values when it's safe
-        return exprType;
+        // to do so. it's always safe to upcast to `any` or `unknown`, so we
+        // can unconditionally do so here.
+        if (is<AnyType, UnknownType>(expectedType))
+            return expectedType;
     }
+    else
+    {
+        if (get<AnyType>(expectedType) || get<UnknownType>(expectedType))
+        {
+            // "Narrowing" to unknown or any is not going to do anything useful.
+            return exprType;
+        }
+    }
+
 
     if (expr->is<AstExprConstantString>())
     {
@@ -210,11 +238,27 @@ TypeId matchLiteralType(
         return exprType;
     }
 
-    // TODO: lambdas
+
+    if (FFlag::LuauBidirectionalInferenceUpcast && expr->is<AstExprFunction>())
+    {
+        // TODO: Push argument / return types into the lambda. For now, just do
+        // the non-literal thing: check for a subtype and upcast if valid.
+        auto result = subtyping->isSubtype(/*subTy=*/exprType, /*superTy=*/expectedType, unifier->scope);
+        return result.isSubtype ? expectedType : exprType;
+    }
 
     if (auto exprTable = expr->as<AstExprTable>())
     {
         TableType* const tableTy = getMutable<TableType>(exprType);
+
+        // This can occur if we have an expression like:
+        //
+        //  { x = {}, x = 42 }
+        //
+        // The type of this will be `{ x: number }`
+        if (FFlag::LuauBidirectionalFailsafe && !tableTy)
+            return exprType;
+
         LUAU_ASSERT(tableTy);
 
         const TableType* expectedTableTy = get<TableType>(expectedType);
@@ -229,7 +273,7 @@ TypeId matchLiteralType(
 
                 if (tt)
                 {
-                    TypeId res = matchLiteralType(astTypes, astExpectedTypes, builtinTypes, arena, unifier, *tt, exprType, expr, toBlock);
+                    TypeId res = matchLiteralType(astTypes, astExpectedTypes, builtinTypes, arena, unifier, subtyping, *tt, exprType, expr, toBlock);
 
                     parts.push_back(res);
                     return arena->addType(UnionType{std::move(parts)});
@@ -241,6 +285,9 @@ TypeId matchLiteralType(
 
         DenseHashSet<AstExprConstantString*> keysToDelete{nullptr};
 
+        DenseHashSet<TypeId> indexerKeyTypes{nullptr};
+        DenseHashSet<TypeId> indexerValueTypes{nullptr};
+
         for (const AstExprTable::Item& item : exprTable->items)
         {
             if (isRecord(item))
@@ -248,23 +295,20 @@ TypeId matchLiteralType(
                 const AstArray<char>& s = item.key->as<AstExprConstantString>()->value;
                 std::string keyStr{s.data, s.data + s.size};
                 auto it = tableTy->props.find(keyStr);
+
+                // This can occur, potentially, if we are re-entrant.
+                if (FFlag::LuauBidirectionalFailsafe && it == tableTy->props.end())
+                    continue;
+
                 LUAU_ASSERT(it != tableTy->props.end());
 
                 Property& prop = it->second;
 
-                if (FFlag::LuauAllowNonSharedTableTypesInLiteral)
+                // If we encounter a duplcate property, we may have already
-                {
+                // set it to be read-only. If that's the case, the only thing
-                    // If we encounter a duplcate property, we may have already
+                // that will definitely crash is trying to access a write
-                    // set it to be read-only. If that's the case, the only thing
+                // only property.
-                    // that will definitely crash is trying to access a write
+                LUAU_ASSERT(!prop.isWriteOnly());
-                    // only property.
-                    LUAU_ASSERT(!prop.isWriteOnly());
-                }
-                else
-                {
-                    // Table literals always initially result in shared read-write types
-                    LUAU_ASSERT(prop.isShared());
-                }
                 TypeId propTy = *prop.readTy;
 
                 auto it2 = expectedTableTy->props.find(keyStr);
@@ -285,21 +329,27 @@ TypeId matchLiteralType(
                             builtinTypes,
                             arena,
                             unifier,
+                            subtyping,
                             expectedTableTy->indexer->indexResultType,
                             propTy,
                             item.value,
                             toBlock
                         );
 
-                        if (tableTy->indexer)
+                        if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
-                            unifier->unify(matchedType, tableTy->indexer->indexResultType);
+                        {
+                            indexerKeyTypes.insert(arena->addType(SingletonType{StringSingleton{keyStr}}));
+                            indexerValueTypes.insert(matchedType);
+                        }
                         else
-                            tableTy->indexer = TableIndexer{expectedTableTy->indexer->indexType, matchedType};
+                        {
+                            if (tableTy->indexer)
+                                unifier->unify(matchedType, tableTy->indexer->indexResultType);
+                            else
+                                tableTy->indexer = TableIndexer{expectedTableTy->indexer->indexType, matchedType};
+                        }
 
-                        if (FFlag::LuauDontInPlaceMutateTableType)
+                        keysToDelete.insert(item.key->as<AstExprConstantString>());
-                            keysToDelete.insert(item.key->as<AstExprConstantString>());
-                        else
-                            tableTy->props.erase(keyStr);
                     }
 
                     // If it's just an extra property and the expected type
@@ -322,22 +372,25 @@ TypeId matchLiteralType(
                 // quadratic in a hurry.
                 if (expectedProp.isShared())
                 {
-                    matchedType =
+                    matchedType = matchLiteralType(
-                        matchLiteralType(astTypes, astExpectedTypes, builtinTypes, arena, unifier, *expectedReadTy, propTy, item.value, toBlock);
+                        astTypes, astExpectedTypes, builtinTypes, arena, unifier, subtyping, *expectedReadTy, propTy, item.value, toBlock
+                    );
                     prop.readTy = matchedType;
                     prop.writeTy = matchedType;
                 }
                 else if (expectedReadTy)
                 {
-                    matchedType =
+                    matchedType = matchLiteralType(
-                        matchLiteralType(astTypes, astExpectedTypes, builtinTypes, arena, unifier, *expectedReadTy, propTy, item.value, toBlock);
+                        astTypes, astExpectedTypes, builtinTypes, arena, unifier, subtyping, *expectedReadTy, propTy, item.value, toBlock
+                    );
                     prop.readTy = matchedType;
                     prop.writeTy.reset();
                 }
                 else if (expectedWriteTy)
                 {
-                    matchedType =
+                    matchedType = matchLiteralType(
-                        matchLiteralType(astTypes, astExpectedTypes, builtinTypes, arena, unifier, *expectedWriteTy, propTy, item.value, toBlock);
+                        astTypes, astExpectedTypes, builtinTypes, arena, unifier, subtyping, *expectedWriteTy, propTy, item.value, toBlock
+                    );
                     prop.readTy.reset();
                     prop.writeTy = matchedType;
                 }
@@ -354,10 +407,16 @@ TypeId matchLiteralType(
                 LUAU_ASSERT(matchedType);
 
                 (*astExpectedTypes)[item.value] = matchedType;
+                // NOTE: We do *not* add to the potential indexer types here.
+                // I think this is correct to support something like:
+                //
+                //  { [string]: number, foo: boolean }
+                //
             }
             else if (item.kind == AstExprTable::Item::List)
             {
-                LUAU_ASSERT(tableTy->indexer);
+                if (!FFlag::LuauBidirectionalInferenceCollectIndexerTypes || !FFlag::LuauBidirectionalInferenceElideAssert)
+                    LUAU_ASSERT(tableTy->indexer);
 
                 if (expectedTableTy->indexer)
                 {
@@ -371,15 +430,24 @@ TypeId matchLiteralType(
                         builtinTypes,
                         arena,
                         unifier,
+                        subtyping,
                         expectedTableTy->indexer->indexResultType,
                         *propTy,
                         item.value,
                         toBlock
                     );
 
-                    // if the index result type is the prop type, we can replace it with the matched type here.
+                    if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
-                    if (tableTy->indexer->indexResultType == *propTy)
+                    {
-                        tableTy->indexer->indexResultType = matchedType;
+                        indexerKeyTypes.insert(builtinTypes->numberType);
+                        indexerValueTypes.insert(matchedType);
+                    }
+                    else
+                    {
+                        // if the index result type is the prop type, we can replace it with the matched type here.
+                        if (tableTy->indexer->indexResultType == *propTy)
+                            tableTy->indexer->indexResultType = matchedType;
+                    }
                 }
             }
             else if (item.kind == AstExprTable::Item::General)
@@ -401,19 +469,22 @@ TypeId matchLiteralType(
                 // Populate expected types for non-string keys declared with [] (the code below will handle the case where they are strings)
                 if (!item.key->as<AstExprConstantString>() && expectedTableTy->indexer)
                     (*astExpectedTypes)[item.key] = expectedTableTy->indexer->indexType;
+
+                if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes)
+                {
+                    indexerKeyTypes.insert(tKey);
+                    indexerValueTypes.insert(tProp);
+                }
             }
             else
                 LUAU_ASSERT(!"Unexpected");
         }
 
-        if (FFlag::LuauDontInPlaceMutateTableType)
+        for (const auto& key : keysToDelete)
         {
-            for (const auto& key : keysToDelete)
+            const AstArray<char>& s = key->value;
-            {
+            std::string keyStr{s.data, s.data + s.size};
-                const AstArray<char>& s = key->value;
+            tableTy->props.erase(keyStr);
-                std::string keyStr{s.data, s.data + s.size};
-                tableTy->props.erase(keyStr);
-            }
         }
 
         // Keys that the expectedType says we should have, but that aren't
@@ -465,9 +536,39 @@ TypeId matchLiteralType(
         // have one too.
         // TODO: If the expected table also has an indexer, we might want to
         // push the expected indexer's types into it.
-        if (expectedTableTy->indexer && !tableTy->indexer)
+        if (FFlag::LuauBidirectionalInferenceCollectIndexerTypes && expectedTableTy->indexer)
         {
-            tableTy->indexer = expectedTableTy->indexer;
+            if (indexerValueTypes.size() > 0 && indexerKeyTypes.size() > 0)
+            {
+                TypeId inferredKeyType = builtinTypes->neverType;
+                TypeId inferredValueType = builtinTypes->neverType;
+                for (auto kt : indexerKeyTypes)
+                {
+                    auto simplified = simplifyUnion(builtinTypes, arena, inferredKeyType, kt);
+                    inferredKeyType = simplified.result;
+                }
+                for (auto vt : indexerValueTypes)
+                {
+                    auto simplified = simplifyUnion(builtinTypes, arena, inferredValueType, vt);
+                    inferredValueType = simplified.result;
+                }
+                tableTy->indexer = TableIndexer{inferredKeyType, inferredValueType};
+                auto keyCheck = subtyping->isSubtype(inferredKeyType, expectedTableTy->indexer->indexType, unifier->scope);
+                if (keyCheck.isSubtype)
+                    tableTy->indexer->indexType = expectedTableTy->indexer->indexType;
+                auto valueCheck = subtyping->isSubtype(inferredValueType, expectedTableTy->indexer->indexResultType, unifier->scope);
+                if (valueCheck.isSubtype)
+                    tableTy->indexer->indexResultType = expectedTableTy->indexer->indexResultType;
+            }
+            else
+                LUAU_ASSERT(indexerKeyTypes.empty() && indexerValueTypes.empty());
+        }
+        else
+        {
+            if (expectedTableTy->indexer && !tableTy->indexer)
+            {
+                tableTy->indexer = expectedTableTy->indexer;
+            }
         }
     }
 

Analysis/src/ToString.cpp

@@ -301,6 +301,28 @@ struct StringifierState
         emit(std::to_string(i).c_str());
     }
 
+    void emit(Polarity p)
+    {
+        switch (p)
+        {
+        case Polarity::None:
+            emit("  ");
+            break;
+        case Polarity::Negative:
+            emit(" -");
+            break;
+        case Polarity::Positive:
+            emit("+ ");
+            break;
+        case Polarity::Mixed:
+            emit("+-");
+            break;
+        default:
+            emit("!!");
+            break;
+        }
+    }
+
     void indent()
     {
         indentation += 4;
@@ -482,6 +504,8 @@ struct TypeStringifier
             {
                 state.emit("'");
                 state.emit(state.getName(ty));
+                if (FInt::DebugLuauVerboseTypeNames >= 1)
+                    state.emit(ftv.polarity);
             }
             else
             {
@@ -494,6 +518,9 @@ struct TypeStringifier
                 state.emit("'");
                 state.emit(state.getName(ty));
 
+                if (FInt::DebugLuauVerboseTypeNames >= 1)
+                    state.emit(ftv.polarity);
+
                 if (!get<UnknownType>(upperBound))
                 {
                     state.emit(" <: ");
@@ -509,6 +536,9 @@ struct TypeStringifier
 
         state.emit(state.getName(ty));
 
+        if (FFlag::LuauSolverV2 && FInt::DebugLuauVerboseTypeNames >= 1)
+            state.emit(ftv.polarity);
+
         if (FInt::DebugLuauVerboseTypeNames >= 2)
         {
             state.emit("-");
@@ -538,6 +568,9 @@ struct TypeStringifier
         else
             state.emit(state.getName(ty));
 
+        if (FInt::DebugLuauVerboseTypeNames >= 1)
+            state.emit(gtv.polarity);
+
         if (FInt::DebugLuauVerboseTypeNames >= 2)
         {
             state.emit("-");
@@ -1222,6 +1255,9 @@ struct TypePackStringifier
             state.emit(state.getName(tp));
         }
 
+        if (FInt::DebugLuauVerboseTypeNames >= 1)
+            state.emit(pack.polarity);
+
         if (FInt::DebugLuauVerboseTypeNames >= 2)
         {
             state.emit("-");
@@ -1241,6 +1277,9 @@ struct TypePackStringifier
             state.emit("free-");
         state.emit(state.getName(tp));
 
+        if (FInt::DebugLuauVerboseTypeNames >= 1)
+            state.emit(pack.polarity);
+
         if (FInt::DebugLuauVerboseTypeNames >= 2)
         {
             state.emit("-");

Analysis/src/Transpiler.cpp

@@ -10,10 +10,11 @@
 #include <limits>
 #include <math.h>
 
-LUAU_FASTFLAG(LuauStoreCSTData)
+LUAU_FASTFLAG(LuauStoreCSTData2)
-LUAU_FASTFLAG(LuauExtendStatEndPosWithSemicolon)
+LUAU_FASTFLAG(LuauAstTypeGroup3)
-LUAU_FASTFLAG(LuauAstTypeGroup2)
 LUAU_FASTFLAG(LuauFixDoBlockEndLocation)
+LUAU_FASTFLAG(LuauParseOptionalAsNode2)
+LUAU_FASTFLAG(LuauFixFunctionWithAttributesStartLocation)
 
 namespace
 {
@@ -166,7 +167,7 @@ struct StringWriter : Writer
 
     void symbol(std::string_view s) override
     {
-        if (FFlag::LuauStoreCSTData)
+        if (FFlag::LuauStoreCSTData2)
         {
             write(s);
         }
@@ -256,7 +257,7 @@ public:
             first = !first;
         else
         {
-            if (FFlag::LuauStoreCSTData && commaPosition)
+            if (FFlag::LuauStoreCSTData2 && commaPosition)
             {
                 writer.advance(*commaPosition);
                 commaPosition++;
@@ -271,6 +272,43 @@ private:
     const Position* commaPosition;
 };
 
+class ArgNameInserter
+{
+public:
+    ArgNameInserter(Writer& w, AstArray<std::optional<AstArgumentName>> names, AstArray<std::optional<Position>> colonPositions)
+        : writer(w)
+        , names(names)
+        , colonPositions(colonPositions)
+    {
+    }
+
+    void operator()()
+    {
+        if (idx < names.size)
+        {
+            const auto name = names.data[idx];
+            if (name.has_value())
+            {
+                writer.advance(name->second.begin);
+                writer.identifier(name->first.value);
+                if (idx < colonPositions.size)
+                {
+                    LUAU_ASSERT(colonPositions.data[idx].has_value());
+                    writer.advance(*colonPositions.data[idx]);
+                }
+                writer.symbol(":");
+            }
+        }
+        idx++;
+    }
+
+private:
+    Writer& writer;
+    AstArray<std::optional<AstArgumentName>> names;
+    AstArray<std::optional<Position>> colonPositions;
+    size_t idx = 0;
+};
+
 struct Printer_DEPRECATED
 {
     explicit Printer_DEPRECATED(Writer& writer)
@@ -330,7 +368,7 @@ struct Printer_DEPRECATED
         else if (typeCount == 1)
         {
             bool shouldParenthesize = unconditionallyParenthesize && (list.types.size == 0 || !list.types.data[0]->is<AstTypeGroup>());
-            if (FFlag::LuauAstTypeGroup2 ? shouldParenthesize : unconditionallyParenthesize)
+            if (FFlag::LuauAstTypeGroup3 ? shouldParenthesize : unconditionallyParenthesize)
                 writer.symbol("(");
 
             // Only variadic tail
@@ -343,7 +381,7 @@ struct Printer_DEPRECATED
                 visualizeTypeAnnotation(*list.types.data[0]);
             }
 
-            if (FFlag::LuauAstTypeGroup2 ? shouldParenthesize : unconditionallyParenthesize)
+            if (FFlag::LuauAstTypeGroup3 ? shouldParenthesize : unconditionallyParenthesize)
                 writer.symbol(")");
         }
         else
@@ -1191,9 +1229,18 @@ struct Printer_DEPRECATED
                 AstType* l = a->types.data[0];
                 AstType* r = a->types.data[1];
 
-                auto lta = l->as<AstTypeReference>();
+                if (FFlag::LuauParseOptionalAsNode2)
-                if (lta && lta->name == "nil")
+                {
-                    std::swap(l, r);
+                    auto lta = l->as<AstTypeReference>();
+                    if (lta && lta->name == "nil" && !r->is<AstTypeOptional>())
+                        std::swap(l, r);
+                }
+                else
+                {
+                    auto lta = l->as<AstTypeReference>();
+                    if (lta && lta->name == "nil")
+                        std::swap(l, r);
+                }
 
                 // it's still possible that we had a (T | U) or (T | nil) and not (nil | T)
                 auto rta = r->as<AstTypeReference>();
@@ -1216,6 +1263,15 @@ struct Printer_DEPRECATED
 
             for (size_t i = 0; i < a->types.size; ++i)
             {
+                if (FFlag::LuauParseOptionalAsNode2)
+                {
+                    if (a->types.data[i]->is<AstTypeOptional>())
+                    {
+                        writer.symbol("?");
+                        continue;
+                    }
+                }
+
                 if (i > 0)
                 {
                     writer.maybeSpace(a->types.data[i]->location.begin, 2);
@@ -1312,7 +1368,7 @@ struct Printer
         }
     }
 
-    void visualizeTypePackAnnotation(const AstTypePack& annotation, bool forVarArg)
+    void visualizeTypePackAnnotation(AstTypePack& annotation, bool forVarArg)
     {
         advance(annotation.location.begin);
         if (const AstTypePackVariadic* variadicTp = annotation.as<AstTypePackVariadic>())
@@ -1322,15 +1378,22 @@ struct Printer
 
             visualizeTypeAnnotation(*variadicTp->variadicType);
         }
-        else if (const AstTypePackGeneric* genericTp = annotation.as<AstTypePackGeneric>())
+        else if (AstTypePackGeneric* genericTp = annotation.as<AstTypePackGeneric>())
         {
             writer.symbol(genericTp->genericName.value);
+            if (const auto cstNode = lookupCstNode<CstTypePackGeneric>(genericTp))
+                advance(cstNode->ellipsisPosition);
             writer.symbol("...");
         }
-        else if (const AstTypePackExplicit* explicitTp = annotation.as<AstTypePackExplicit>())
+        else if (AstTypePackExplicit* explicitTp = annotation.as<AstTypePackExplicit>())
         {
             LUAU_ASSERT(!forVarArg);
-            visualizeTypeList(explicitTp->typeList, true);
+            if (const auto cstNode = lookupCstNode<CstTypePackExplicit>(explicitTp))
+                visualizeTypeList(
+                    explicitTp->typeList, true, cstNode->openParenthesesPosition, cstNode->closeParenthesesPosition, cstNode->commaPositions
+                );
+            else
+                visualizeTypeList(explicitTp->typeList, true);
         }
         else
         {
@@ -1338,19 +1401,37 @@ struct Printer
         }
     }
 
-    void visualizeTypeList(const AstTypeList& list, bool unconditionallyParenthesize)
+    void visualizeNamedTypeList(
+        const AstTypeList& list,
+        bool unconditionallyParenthesize,
+        std::optional<Position> openParenthesesPosition,
+        std::optional<Position> closeParenthesesPosition,
+        AstArray<Position> commaPositions,
+        AstArray<std::optional<AstArgumentName>> argNames,
+        AstArray<std::optional<Position>> argNamesColonPositions
+    )
     {
         size_t typeCount = list.types.size + (list.tailType != nullptr ? 1 : 0);
         if (typeCount == 0)
         {
+            if (openParenthesesPosition)
+                advance(*openParenthesesPosition);
             writer.symbol("(");
+            if (closeParenthesesPosition)
+                advance(*closeParenthesesPosition);
             writer.symbol(")");
         }
         else if (typeCount == 1)
         {
             bool shouldParenthesize = unconditionallyParenthesize && (list.types.size == 0 || !list.types.data[0]->is<AstTypeGroup>());
-            if (FFlag::LuauAstTypeGroup2 ? shouldParenthesize : unconditionallyParenthesize)
+            if (FFlag::LuauAstTypeGroup3 ? shouldParenthesize : unconditionallyParenthesize)
+            {
+                if (openParenthesesPosition)
+                    advance(*openParenthesesPosition);
                 writer.symbol("(");
+            }
+
+            ArgNameInserter(writer, argNames, argNamesColonPositions)();
 
             // Only variadic tail
             if (list.types.size == 0)
@@ -1362,34 +1443,51 @@ struct Printer
                 visualizeTypeAnnotation(*list.types.data[0]);
             }
 
-            if (FFlag::LuauAstTypeGroup2 ? shouldParenthesize : unconditionallyParenthesize)
+            if (FFlag::LuauAstTypeGroup3 ? shouldParenthesize : unconditionallyParenthesize)
+            {
+                if (closeParenthesesPosition)
+                    advance(*closeParenthesesPosition);
                 writer.symbol(")");
+            }
         }
         else
         {
+            if (openParenthesesPosition)
+                advance(*openParenthesesPosition);
             writer.symbol("(");
 
-            bool first = true;
+            CommaSeparatorInserter comma(writer, commaPositions.size > 0 ? commaPositions.begin() : nullptr);
+            ArgNameInserter argName(writer, argNames, argNamesColonPositions);
             for (const auto& el : list.types)
             {
-                if (first)
+                comma();
-                    first = false;
+                argName();
-                else
-                    writer.symbol(",");
-
                 visualizeTypeAnnotation(*el);
             }
 
             if (list.tailType)
             {
-                writer.symbol(",");
+                comma();
                 visualizeTypePackAnnotation(*list.tailType, false);
             }
 
+            if (closeParenthesesPosition)
+                advance(*closeParenthesesPosition);
             writer.symbol(")");
         }
     }
 
+    void visualizeTypeList(
+        const AstTypeList& list,
+        bool unconditionallyParenthesize,
+        std::optional<Position> openParenthesesPosition = std::nullopt,
+        std::optional<Position> closeParenthesesPosition = std::nullopt,
+        AstArray<Position> commaPositions = {}
+    )
+    {
+        visualizeNamedTypeList(list, unconditionallyParenthesize, openParenthesesPosition, closeParenthesesPosition, commaPositions, {}, {});
+    }
+
     bool isIntegerish(double d)
     {
         if (d <= std::numeric_limits<int>::max() && d >= std::numeric_limits<int>::min())
@@ -1400,13 +1498,14 @@ struct Printer
 
     void visualize(AstExpr& expr)
     {
-        advance(expr.location.begin);
+        if (!expr.is<AstExprFunction>() || FFlag::LuauFixFunctionWithAttributesStartLocation)
+            advance(expr.location.begin);
 
         if (const auto& a = expr.as<AstExprGroup>())
         {
             writer.symbol("(");
             visualize(*a->expr);
-            advance(Position{a->location.end.line, a->location.end.column - 1});
+            advanceBefore(a->location.end, 1);
             writer.symbol(")");
         }
         else if (expr.is<AstExprConstantNil>())
@@ -1534,6 +1633,17 @@ struct Printer
         }
         else if (const auto& a = expr.as<AstExprFunction>())
         {
+            for (const auto& attribute : a->attributes)
+                visualizeAttribute(*attribute);
+            if (FFlag::LuauFixFunctionWithAttributesStartLocation)
+            {
+                if (const auto cstNode = lookupCstNode<CstExprFunction>(a))
+                    advance(cstNode->functionKeywordPosition);
+            }
+            else
+            {
+                advance(a->location.begin);
+            }
             writer.keyword("function");
             visualizeFunctionBody(*a);
         }
@@ -1775,9 +1885,18 @@ struct Printer
         writer.advance(newPos);
     }
 
+    void advanceBefore(const Position& newPos, unsigned int tokenLength)
+    {
+        if (newPos.column >= tokenLength)
+            advance(Position{newPos.line, newPos.column - tokenLength});
+        else
+            advance(newPos);
+    }
+
     void visualize(AstStat& program)
     {
-        advance(program.location.begin);
+        if ((!program.is<AstStatLocalFunction>() && !program.is<AstStatFunction>()) || FFlag::LuauFixFunctionWithAttributesStartLocation)
+            advance(program.location.begin);
 
         if (const auto& block = program.as<AstStatBlock>())
         {
@@ -1817,8 +1936,8 @@ struct Printer
             visualizeBlock(*a->body);
             if (const auto cstNode = lookupCstNode<CstStatRepeat>(a))
                 writer.advance(cstNode->untilPosition);
-            else if (a->condition->location.begin.column > 5)
+            else
-                writer.advance(Position{a->condition->location.begin.line, a->condition->location.begin.column - 6});
+                advanceBefore(a->condition->location.begin, 6);
             writer.keyword("until");
             visualize(*a->condition);
         }
@@ -2014,13 +2133,36 @@ struct Printer
         }
         else if (const auto& a = program.as<AstStatFunction>())
         {
+            for (const auto& attribute : a->func->attributes)
+                visualizeAttribute(*attribute);
+            if (FFlag::LuauFixFunctionWithAttributesStartLocation)
+            {
+                if (const auto cstNode = lookupCstNode<CstStatFunction>(a))
+                    advance(cstNode->functionKeywordPosition);
+            }
+            else
+            {
+                advance(a->location.begin);
+            }
             writer.keyword("function");
             visualize(*a->name);
             visualizeFunctionBody(*a->func);
         }
         else if (const auto& a = program.as<AstStatLocalFunction>())
         {
+            for (const auto& attribute : a->func->attributes)
+                visualizeAttribute(*attribute);
+
             const auto cstNode = lookupCstNode<CstStatLocalFunction>(a);
+            if (FFlag::LuauFixFunctionWithAttributesStartLocation)
+            {
+                if (cstNode)
+                    advance(cstNode->localKeywordPosition);
+            }
+            else
+            {
+                advance(a->location.begin);
+            }
 
             writer.keyword("local");
 
@@ -2121,7 +2263,20 @@ struct Printer
         {
             if (writeTypes)
             {
-                writer.keyword("type function");
+                const auto cstNode = lookupCstNode<CstStatTypeFunction>(t);
+                if (t->exported)
+                    writer.keyword("export");
+                if (cstNode)
+                    advance(cstNode->typeKeywordPosition);
+                else
+                    writer.space();
+                writer.keyword("type");
+                if (cstNode)
+                    advance(cstNode->functionKeywordPosition);
+                else
+                    writer.space();
+                writer.keyword("function");
+                advance(t->nameLocation.begin);
                 writer.identifier(t->name.value);
                 visualizeFunctionBody(*t->body);
             }
@@ -2151,17 +2306,23 @@ struct Printer
 
         if (program.hasSemicolon)
         {
-            if (FFlag::LuauStoreCSTData)
+            if (FFlag::LuauStoreCSTData2)
-                advance(Position{program.location.end.line, program.location.end.column - 1});
+                advanceBefore(program.location.end, 1);
             writer.symbol(";");
         }
     }
 
     void visualizeFunctionBody(AstExprFunction& func)
     {
+        const auto cstNode = lookupCstNode<CstExprFunction>(&func);
+
+        // TODO(CLI-139347): need to handle return type (incl. parentheses of return type)
+
         if (func.generics.size > 0 || func.genericPacks.size > 0)
         {
-            CommaSeparatorInserter comma(writer);
+            CommaSeparatorInserter comma(writer, cstNode ? cstNode->genericsCommaPositions.begin() : nullptr);
+            if (cstNode)
+                advance(cstNode->openGenericsPosition);
             writer.symbol("<");
             for (const auto& o : func.generics)
             {
@@ -2176,13 +2337,19 @@ struct Printer
 
                 writer.advance(o->location.begin);
                 writer.identifier(o->name.value);
+                if (const auto* genericTypePackCstNode = lookupCstNode<CstGenericTypePack>(o))
+                    advance(genericTypePackCstNode->ellipsisPosition);
                 writer.symbol("...");
             }
+            if (cstNode)
+                advance(cstNode->closeGenericsPosition);
             writer.symbol(">");
         }
 
+        if (func.argLocation)
+            advance(func.argLocation->begin);
         writer.symbol("(");
-        CommaSeparatorInserter comma(writer);
+        CommaSeparatorInserter comma(writer, cstNode ? cstNode->argsCommaPositions.begin() : nullptr);
 
         for (size_t i = 0; i < func.args.size; ++i)
         {
@@ -2212,10 +2379,14 @@ struct Printer
             }
         }
 
+        if (func.argLocation)
+            advanceBefore(func.argLocation->end, 1);
         writer.symbol(")");
 
         if (writeTypes && func.returnAnnotation)
         {
+            if (cstNode)
+                advance(cstNode->returnSpecifierPosition);
             writer.symbol(":");
             writer.space();
 
@@ -2301,6 +2472,23 @@ struct Printer
         }
     }
 
+    void visualizeAttribute(AstAttr& attribute)
+    {
+        advance(attribute.location.begin);
+        switch (attribute.type)
+        {
+        case AstAttr::Checked:
+            writer.keyword("@checked");
+            break;
+        case AstAttr::Native:
+            writer.keyword("@native");
+            break;
+        case AstAttr::Deprecated:
+            writer.keyword("@deprecated");
+            break;
+        }
+    }
+
     void visualizeTypeAnnotation(AstType& typeAnnotation)
     {
         advance(typeAnnotation.location.begin);
@@ -2340,9 +2528,13 @@ struct Printer
         }
         else if (const auto& a = typeAnnotation.as<AstTypeFunction>())
         {
+            const auto cstNode = lookupCstNode<CstTypeFunction>(a);
+
             if (a->generics.size > 0 || a->genericPacks.size > 0)
             {
-                CommaSeparatorInserter comma(writer);
+                CommaSeparatorInserter comma(writer, cstNode ? cstNode->genericsCommaPositions.begin() : nullptr);
+                if (cstNode)
+                    advance(cstNode->openGenericsPosition);
                 writer.symbol("<");
                 for (const auto& o : a->generics)
                 {
@@ -2357,15 +2549,29 @@ struct Printer
 
                     writer.advance(o->location.begin);
                     writer.identifier(o->name.value);
+                    if (const auto* genericTypePackCstNode = lookupCstNode<CstGenericTypePack>(o))
+                        advance(genericTypePackCstNode->ellipsisPosition);
                     writer.symbol("...");
                 }
+                if (cstNode)
+                    advance(cstNode->closeGenericsPosition);
                 writer.symbol(">");
             }
 
             {
-                visualizeTypeList(a->argTypes, true);
+                visualizeNamedTypeList(
+                    a->argTypes,
+                    true,
+                    cstNode ? std::make_optional(cstNode->openArgsPosition) : std::nullopt,
+                    cstNode ? std::make_optional(cstNode->closeArgsPosition) : std::nullopt,
+                    cstNode ? cstNode->argumentsCommaPositions : Luau::AstArray<Position>{},
+                    a->argNames,
+                    cstNode ? cstNode->argumentNameColonPositions : Luau::AstArray<std::optional<Position>>{}
+                );
             }
 
+            if (cstNode)
+                advance(cstNode->returnArrowPosition);
             writer.symbol("->");
             visualizeTypeList(a->returnTypes, true);
         }
@@ -2527,14 +2733,25 @@ struct Printer
         }
         else if (const auto& a = typeAnnotation.as<AstTypeUnion>())
         {
-            if (a->types.size == 2)
+            const auto cstNode = lookupCstNode<CstTypeUnion>(a);
+
+            if (!cstNode && a->types.size == 2)
             {
                 AstType* l = a->types.data[0];
                 AstType* r = a->types.data[1];
 
-                auto lta = l->as<AstTypeReference>();
+                if (FFlag::LuauParseOptionalAsNode2)
-                if (lta && lta->name == "nil")
+                {
-                    std::swap(l, r);
+                    auto lta = l->as<AstTypeReference>();
+                    if (lta && lta->name == "nil" && !r->is<AstTypeOptional>())
+                        std::swap(l, r);
+                }
+                else
+                {
+                    auto lta = l->as<AstTypeReference>();
+                    if (lta && lta->name == "nil")
+                        std::swap(l, r);
+                }
 
                 // it's still possible that we had a (T | U) or (T | nil) and not (nil | T)
                 auto rta = r->as<AstTypeReference>();
@@ -2555,15 +2772,39 @@ struct Printer
                 }
             }
 
+            if (cstNode && cstNode->leadingPosition)
+            {
+                advance(*cstNode->leadingPosition);
+                writer.symbol("|");
+            }
+
+            size_t separatorIndex = 0;
             for (size_t i = 0; i < a->types.size; ++i)
             {
+                if (FFlag::LuauParseOptionalAsNode2)
+                {
+                    if (const auto optional = a->types.data[i]->as<AstTypeOptional>())
+                    {
+                        advance(optional->location.begin);
+                        writer.symbol("?");
+                        continue;
+                    }
+                }
+
                 if (i > 0)
                 {
-                    writer.maybeSpace(a->types.data[i]->location.begin, 2);
+                    if (cstNode && FFlag::LuauParseOptionalAsNode2)
+                    {
+                        // separatorIndex is only valid if `?` is handled as an AstTypeOptional
+                        advance(cstNode->separatorPositions.data[separatorIndex]);
+                        separatorIndex++;
+                    }
+                    else
+                        writer.maybeSpace(a->types.data[i]->location.begin, 2);
                     writer.symbol("|");
                 }
 
-                bool wrap = a->types.data[i]->as<AstTypeIntersection>() || a->types.data[i]->as<AstTypeFunction>();
+                bool wrap = !cstNode && (a->types.data[i]->as<AstTypeIntersection>() || a->types.data[i]->as<AstTypeFunction>());
 
                 if (wrap)
                     writer.symbol("(");
@@ -2576,15 +2817,27 @@ struct Printer
         }
         else if (const auto& a = typeAnnotation.as<AstTypeIntersection>())
         {
+            const auto cstNode = lookupCstNode<CstTypeIntersection>(a);
+
+            // If the sizes are equal, we know there is a leading & token
+            if (cstNode && cstNode->leadingPosition)
+            {
+                advance(*cstNode->leadingPosition);
+                writer.symbol("&");
+            }
+
             for (size_t i = 0; i < a->types.size; ++i)
             {
                 if (i > 0)
                 {
-                    writer.maybeSpace(a->types.data[i]->location.begin, 2);
+                    if (cstNode)
+                        advance(cstNode->separatorPositions.data[i - 1]);
+                    else
+                        writer.maybeSpace(a->types.data[i]->location.begin, 2);
                     writer.symbol("&");
                 }
 
-                bool wrap = a->types.data[i]->as<AstTypeUnion>() || a->types.data[i]->as<AstTypeFunction>();
+                bool wrap = !cstNode && (a->types.data[i]->as<AstTypeUnion>() || a->types.data[i]->as<AstTypeFunction>());
 
                 if (wrap)
                     writer.symbol("(");
@@ -2599,7 +2852,7 @@ struct Printer
         {
             writer.symbol("(");
             visualizeTypeAnnotation(*a->type);
-            advance(Position{a->location.end.line, a->location.end.column - 1});
+            advanceBefore(a->location.end, 1);
             writer.symbol(")");
         }
         else if (const auto& a = typeAnnotation.as<AstTypeSingletonBool>())
@@ -2633,7 +2886,7 @@ std::string toString(AstNode* node)
     StringWriter writer;
     writer.pos = node->location.begin;
 
-    if (FFlag::LuauStoreCSTData)
+    if (FFlag::LuauStoreCSTData2)
     {
         Printer printer(writer, CstNodeMap{nullptr});
         printer.writeTypes = true;
@@ -2669,7 +2922,7 @@ void dump(AstNode* node)
 std::string transpile(AstStatBlock& block, const CstNodeMap& cstNodeMap)
 {
     StringWriter writer;
-    if (FFlag::LuauStoreCSTData)
+    if (FFlag::LuauStoreCSTData2)
     {
         Printer(writer, cstNodeMap).visualizeBlock(block);
     }
@@ -2683,7 +2936,7 @@ std::string transpile(AstStatBlock& block, const CstNodeMap& cstNodeMap)
 std::string transpileWithTypes(AstStatBlock& block, const CstNodeMap& cstNodeMap)
 {
     StringWriter writer;
-    if (FFlag::LuauStoreCSTData)
+    if (FFlag::LuauStoreCSTData2)
     {
         Printer printer(writer, cstNodeMap);
         printer.writeTypes = true;

Analysis/src/TxnLog.cpp

@@ -407,41 +407,6 @@ PendingTypePack* TxnLog::changeLevel(TypePackId tp, TypeLevel newLevel)
     return newTp;
 }
 
-PendingType* TxnLog::changeScope(TypeId ty, NotNull<Scope> newScope)
-{
-    LUAU_ASSERT(get<FreeType>(ty) || get<TableType>(ty) || get<FunctionType>(ty));
-
-    PendingType* newTy = queue(ty);
-    if (FreeType* ftv = Luau::getMutable<FreeType>(newTy))
-    {
-        ftv->scope = newScope;
-    }
-    else if (TableType* ttv = Luau::getMutable<TableType>(newTy))
-    {
-        LUAU_ASSERT(ttv->state == TableState::Free || ttv->state == TableState::Generic);
-        ttv->scope = newScope;
-    }
-    else if (FunctionType* ftv = Luau::getMutable<FunctionType>(newTy))
-    {
-        ftv->scope = newScope;
-    }
-
-    return newTy;
-}
-
-PendingTypePack* TxnLog::changeScope(TypePackId tp, NotNull<Scope> newScope)
-{
-    LUAU_ASSERT(get<FreeTypePack>(tp));
-
-    PendingTypePack* newTp = queue(tp);
-    if (FreeTypePack* ftp = Luau::getMutable<FreeTypePack>(newTp))
-    {
-        ftp->scope = newScope;
-    }
-
-    return newTp;
-}
-
 PendingType* TxnLog::changeIndexer(TypeId ty, std::optional<TableIndexer> indexer)
 {
     LUAU_ASSERT(get<TableType>(ty));

Analysis/src/Type.cpp

@@ -488,11 +488,12 @@ FreeType::FreeType(TypeLevel level, TypeId lowerBound, TypeId upperBound)
 {
 }
 
-FreeType::FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound)
+FreeType::FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound, Polarity polarity)
     : index(Unifiable::freshIndex())
     , scope(scope)
     , lowerBound(lowerBound)
     , upperBound(upperBound)
+    , polarity(polarity)
 {
 }
 
@@ -543,16 +544,18 @@ GenericType::GenericType(TypeLevel level)
 {
 }
 
-GenericType::GenericType(const Name& name)
+GenericType::GenericType(const Name& name, Polarity polarity)
     : index(Unifiable::freshIndex())
     , name(name)
     , explicitName(true)
+    , polarity(polarity)
 {
 }
 
-GenericType::GenericType(Scope* scope)
+GenericType::GenericType(Scope* scope, Polarity polarity)
     : index(Unifiable::freshIndex())
     , scope(scope)
+    , polarity(polarity)
 {
 }
 
@@ -630,23 +633,6 @@ FunctionType::FunctionType(TypeLevel level, TypePackId argTypes, TypePackId retT
 {
 }
 
-FunctionType::FunctionType(
-    TypeLevel level,
-    Scope* scope,
-    TypePackId argTypes,
-    TypePackId retTypes,
-    std::optional<FunctionDefinition> defn,
-    bool hasSelf
-)
-    : definition(std::move(defn))
-    , level(level)
-    , scope(scope)
-    , argTypes(argTypes)
-    , retTypes(retTypes)
-    , hasSelf(hasSelf)
-{
-}
-
 FunctionType::FunctionType(
     std::vector<TypeId> generics,
     std::vector<TypePackId> genericPacks,
@@ -683,27 +669,6 @@ FunctionType::FunctionType(
 {
 }
 
-FunctionType::FunctionType(
-    TypeLevel level,
-    Scope* scope,
-    std::vector<TypeId> generics,
-    std::vector<TypePackId> genericPacks,
-    TypePackId argTypes,
-    TypePackId retTypes,
-    std::optional<FunctionDefinition> defn,
-    bool hasSelf
-)
-    : definition(std::move(defn))
-    , generics(generics)
-    , genericPacks(genericPacks)
-    , level(level)
-    , scope(scope)
-    , argTypes(argTypes)
-    , retTypes(retTypes)
-    , hasSelf(hasSelf)
-{
-}
-
 Property::Property() {}
 
 Property::Property(
@@ -1306,9 +1271,9 @@ IntersectionTypeIterator end(const IntersectionType* itv)
     return IntersectionTypeIterator{};
 }
 
-TypeId freshType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, Scope* scope)
+TypeId freshType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, Scope* scope, Polarity polarity)
 {
-    return arena->addType(FreeType{scope, builtinTypes->neverType, builtinTypes->unknownType});
+    return arena->addType(FreeType{scope, builtinTypes->neverType, builtinTypes->unknownType, polarity});
 }
 
 std::vector<TypeId> filterMap(TypeId type, TypeIdPredicate predicate)

Analysis/src/TypeArena.cpp

@@ -77,9 +77,9 @@ TypeId TypeArena::freshType_DEPRECATED(Scope* scope, TypeLevel level)
     return allocated;
 }
 
-TypePackId TypeArena::freshTypePack(Scope* scope)
+TypePackId TypeArena::freshTypePack(Scope* scope, Polarity polarity)
 {
-    TypePackId allocated = typePacks.allocate(FreeTypePack{scope});
+    TypePackId allocated = typePacks.allocate(FreeTypePack{scope, polarity});
 
     asMutable(allocated)->owningArena = this;
 

Analysis/src/TypeAttach.cpp

@@ -13,6 +13,8 @@
 
 #include <string>
 
+LUAU_FASTFLAG(LuauStoreCSTData2)
+
 static char* allocateString(Luau::Allocator& allocator, std::string_view contents)
 {
     char* result = (char*)allocator.allocate(contents.size() + 1);
@@ -305,7 +307,8 @@ public:
             std::optional<AstArgumentName>* arg = &argNames.data[i++];
 
             if (el)
-                new (arg) std::optional<AstArgumentName>(AstArgumentName(AstName(el->name.c_str()), el->location));
+                new (arg)
+                    std::optional<AstArgumentName>(AstArgumentName(AstName(el->name.c_str()), FFlag::LuauStoreCSTData2 ? Location() : el->location));
             else
                 new (arg) std::optional<AstArgumentName>();
         }

Analysis/src/TypeChecker2.cpp

@@ -26,10 +26,14 @@
 #include "Luau/VisitType.h"
 
 #include <algorithm>
+#include <sstream>
 
 LUAU_FASTFLAG(DebugLuauMagicTypes)
 
 LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+LUAU_FASTFLAGVARIABLE(LuauImproveTypePathsInErrors)
+LUAU_FASTFLAG(LuauUserTypeFunTypecheck)
+LUAU_FASTFLAGVARIABLE(LuauTypeCheckerAcceptNumberConcats)
 
 namespace Luau
 {
@@ -1201,7 +1205,8 @@ void TypeChecker2::visit(AstStatTypeAlias* stat)
 
 void TypeChecker2::visit(AstStatTypeFunction* stat)
 {
-    // TODO: add type checking for user-defined type functions
+    if (FFlag::LuauUserTypeFunTypecheck)
+        visit(stat->body);
 }
 
 void TypeChecker2::visit(AstTypeList types)
@@ -2225,10 +2230,21 @@ TypeId TypeChecker2::visit(AstExprBinary* expr, AstNode* overrideKey)
 
         return builtinTypes->numberType;
     case AstExprBinary::Op::Concat:
-        testIsSubtype(leftType, builtinTypes->stringType, expr->left->location);
+    {
-        testIsSubtype(rightType, builtinTypes->stringType, expr->right->location);
+        if (FFlag::LuauTypeCheckerAcceptNumberConcats)
+        {
+            const TypeId numberOrString = module->internalTypes.addType(UnionType{{builtinTypes->numberType, builtinTypes->stringType}});
+            testIsSubtype(leftType, numberOrString, expr->left->location);
+            testIsSubtype(rightType, numberOrString, expr->right->location);
+        }
+        else
+        {
+            testIsSubtype(leftType, builtinTypes->stringType, expr->left->location);
+            testIsSubtype(rightType, builtinTypes->stringType, expr->right->location);
+        }
 
         return builtinTypes->stringType;
+    }
     case AstExprBinary::Op::CompareGe:
     case AstExprBinary::Op::CompareGt:
     case AstExprBinary::Op::CompareLe:
@@ -2701,20 +2717,61 @@ Reasonings TypeChecker2::explainReasonings_(TID subTy, TID superTy, Location loc
         if (!subLeafTy && !superLeafTy && !subLeafTp && !superLeafTp)
             ice->ice("Subtyping test returned a reasoning where one path ends at a type and the other ends at a pack.", location);
 
-        std::string relation = "a subtype of";
+        if (FFlag::LuauImproveTypePathsInErrors)
-        if (reasoning.variance == SubtypingVariance::Invariant)
+        {
-            relation = "exactly";
+            std::string relation = "a subtype of";
-        else if (reasoning.variance == SubtypingVariance::Contravariant)
+            if (reasoning.variance == SubtypingVariance::Invariant)
-            relation = "a supertype of";
+                relation = "exactly";
+            else if (reasoning.variance == SubtypingVariance::Contravariant)
+                relation = "a supertype of";
 
-        std::string reason;
+            std::string subLeafAsString = toString(subLeaf);
-        if (reasoning.subPath == reasoning.superPath)
+            // if the string is empty, it must be an empty type pack
-            reason = "at " + toString(reasoning.subPath) + ", " + toString(subLeaf) + " is not " + relation + " " + toString(superLeaf);
+            if (subLeafAsString.empty())
+                subLeafAsString = "()";
+
+            std::string superLeafAsString = toString(superLeaf);
+            // if the string is empty, it must be an empty type pack
+            if (superLeafAsString.empty())
+                superLeafAsString = "()";
+
+            std::stringstream baseReasonBuilder;
+            baseReasonBuilder << "`" << subLeafAsString << "` is not " << relation << " `" << superLeafAsString << "`";
+            std::string baseReason = baseReasonBuilder.str();
+
+            std::stringstream reason;
+
+            if (reasoning.subPath == reasoning.superPath)
+                reason << toStringHuman(reasoning.subPath) << "`" << subLeafAsString << "` in the former type and `" << superLeafAsString
+                       << "` in the latter type, and " << baseReason;
+            else if (!reasoning.subPath.empty() && !reasoning.superPath.empty())
+                reason << toStringHuman(reasoning.subPath) << "`" << subLeafAsString << "` and " << toStringHuman(reasoning.superPath) << "`"
+                       << superLeafAsString << "`, and " << baseReason;
+            else if (!reasoning.subPath.empty())
+                reason << toStringHuman(reasoning.subPath) << "`" << subLeafAsString << "`, which is not " << relation << " `" << superLeafAsString
+                       << "`";
+            else
+                reason << toStringHuman(reasoning.superPath) << "`" << superLeafAsString << "`, and " << baseReason;
+
+            reasons.push_back(reason.str());
+        }
         else
-            reason = "type " + toString(subTy) + toString(reasoning.subPath, /* prefixDot */ true) + " (" + toString(subLeaf) + ") is not " +
+        {
-                     relation + " " + toString(superTy) + toString(reasoning.superPath, /* prefixDot */ true) + " (" + toString(superLeaf) + ")";
+            std::string relation = "a subtype of";
+            if (reasoning.variance == SubtypingVariance::Invariant)
+                relation = "exactly";
+            else if (reasoning.variance == SubtypingVariance::Contravariant)
+                relation = "a supertype of";
 
-        reasons.push_back(reason);
+            std::string reason;
+            if (reasoning.subPath == reasoning.superPath)
+                reason = "at " + toString(reasoning.subPath) + ", " + toString(subLeaf) + " is not " + relation + " " + toString(superLeaf);
+            else
+                reason = "type " + toString(subTy) + toString(reasoning.subPath, /* prefixDot */ true) + " (" + toString(subLeaf) + ") is not " +
+                         relation + " " + toString(superTy) + toString(reasoning.superPath, /* prefixDot */ true) + " (" + toString(superLeaf) + ")";
+
+            reasons.push_back(reason);
+        }
 
         // if we haven't already proved this isn't suppressing, we have to keep checking.
         if (suppressed)

Analysis/src/TypeFunctionRuntime.cpp

@@ -13,11 +13,7 @@
 #include <set>
 #include <vector>
 
-LUAU_FASTFLAGVARIABLE(LuauTypeFunFixHydratedClasses)
 LUAU_DYNAMIC_FASTINT(LuauTypeFunctionSerdeIterationLimit)
-LUAU_FASTFLAGVARIABLE(LuauTypeFunSingletonEquality)
-LUAU_FASTFLAGVARIABLE(LuauUserTypeFunTypeofReturnsType)
-LUAU_FASTFLAGVARIABLE(LuauTypeFunPrintFix)
 LUAU_FASTFLAGVARIABLE(LuauTypeFunReadWriteParents)
 
 namespace Luau
@@ -1617,11 +1613,8 @@ void registerTypeUserData(lua_State* L)
     // Create and register metatable for type userdata
     luaL_newmetatable(L, "type");
 
-    if (FFlag::LuauUserTypeFunTypeofReturnsType)
+    lua_pushstring(L, "type");
-    {
+    lua_setfield(L, -2, "__type");
-        lua_pushstring(L, "type");
-        lua_setfield(L, -2, "__type");
-    }
 
     // Protect metatable from being changed
     lua_pushstring(L, "The metatable is locked");
@@ -1662,10 +1655,7 @@ static int print(lua_State* L)
         const char* s = luaL_tolstring(L, i, &l); // convert to string using __tostring et al
         if (i > 1)
         {
-            if (FFlag::LuauTypeFunPrintFix)
+            result.append(1, '\t');
-                result.append(1, '\t');
-            else
-                result.append('\t', 1);
         }
         result.append(s, l);
         lua_pop(L, 1);
@@ -1758,14 +1748,14 @@ bool areEqual(SeenSet& seen, const TypeFunctionSingletonType& lhs, const TypeFun
 
     {
         const TypeFunctionBooleanSingleton* lp = get<TypeFunctionBooleanSingleton>(&lhs);
-        const TypeFunctionBooleanSingleton* rp = get<TypeFunctionBooleanSingleton>(FFlag::LuauTypeFunSingletonEquality ? &rhs : &lhs);
+        const TypeFunctionBooleanSingleton* rp = get<TypeFunctionBooleanSingleton>(&rhs);
         if (lp && rp)
             return lp->value == rp->value;
     }
 
     {
         const TypeFunctionStringSingleton* lp = get<TypeFunctionStringSingleton>(&lhs);
-        const TypeFunctionStringSingleton* rp = get<TypeFunctionStringSingleton>(FFlag::LuauTypeFunSingletonEquality ? &rhs : &lhs);
+        const TypeFunctionStringSingleton* rp = get<TypeFunctionStringSingleton>(&rhs);
         if (lp && rp)
             return lp->value == rp->value;
     }
@@ -1918,10 +1908,7 @@ bool areEqual(SeenSet& seen, const TypeFunctionClassType& lhs, const TypeFunctio
     if (seenSetContains(seen, &lhs, &rhs))
         return true;
 
-    if (FFlag::LuauTypeFunFixHydratedClasses)
+    return lhs.classTy == rhs.classTy;
-        return lhs.classTy == rhs.classTy;
-    else
-        return lhs.name_DEPRECATED == rhs.name_DEPRECATED;
 }
 
 bool areEqual(SeenSet& seen, const TypeFunctionType& lhs, const TypeFunctionType& rhs)

Analysis/src/TypeFunctionRuntimeBuilder.cpp

@@ -19,7 +19,6 @@
 // used to control the recursion limit of any operations done by user-defined type functions
 // currently, controls serialization, deserialization, and `type.copy`
 LUAU_DYNAMIC_FASTINTVARIABLE(LuauTypeFunctionSerdeIterationLimit, 100'000);
-LUAU_FASTFLAG(LuauTypeFunFixHydratedClasses)
 LUAU_FASTFLAG(LuauTypeFunReadWriteParents)
 
 namespace Luau
@@ -209,19 +208,11 @@ private:
         }
         else if (auto c = get<ClassType>(ty))
         {
-            if (FFlag::LuauTypeFunFixHydratedClasses)
+            // Since there aren't any new class types being created in type functions, we will deserialize by using a direct reference to the original
-            {
+            // class
-                // Since there aren't any new class types being created in type functions, we will deserialize by using a direct reference to the
+            target = typeFunctionRuntime->typeArena.allocate(
-                // original class
+                TypeFunctionClassType{{}, std::nullopt, std::nullopt, std::nullopt, std::nullopt, std::nullopt, ty}
-                target = typeFunctionRuntime->typeArena.allocate(TypeFunctionClassType{{}, std::nullopt, std::nullopt, std::nullopt, std::nullopt, std::nullopt, ty});
+            );
-            }
-            else
-            {
-                state->classesSerialized_DEPRECATED[c->name] = ty;
-                target = typeFunctionRuntime->typeArena.allocate(
-                    TypeFunctionClassType{{}, std::nullopt, std::nullopt, std::nullopt, std::nullopt, std::nullopt, /* classTy */ nullptr, c->name}
-                );
-            }
         }
         else if (auto g = get<GenericType>(ty))
         {
@@ -713,17 +704,7 @@ private:
         }
         else if (auto c = get<TypeFunctionClassType>(ty))
         {
-            if (FFlag::LuauTypeFunFixHydratedClasses)
+            target = c->classTy;
-            {
-                target = c->classTy;
-            }
-            else
-            {
-                if (auto result = state->classesSerialized_DEPRECATED.find(c->name_DEPRECATED))
-                    target = *result;
-                else
-                    state->ctx->ice->ice("Deserializing user defined type function arguments: mysterious class type is being deserialized");
-            }
         }
         else if (auto g = get<TypeFunctionGenericType>(ty))
         {

Analysis/src/TypeInfer.cpp

@@ -32,9 +32,10 @@ LUAU_FASTINTVARIABLE(LuauVisitRecursionLimit, 500)
 LUAU_FASTFLAG(LuauKnowsTheDataModel3)
 LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification)
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
-LUAU_FASTFLAGVARIABLE(LuauOldSolverCreatesChildScopePointers)
 LUAU_FASTFLAG(LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)
 LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+LUAU_FASTFLAG(LuauRetainDefinitionAliasLocations)
+LUAU_FASTFLAGVARIABLE(LuauStatForInFix)
 
 namespace Luau
 {
@@ -255,6 +256,7 @@ ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mo
     currentModule->type = module.type;
     currentModule->allocator = module.allocator;
     currentModule->names = module.names;
+    currentModule->root = module.root;
 
     iceHandler->moduleName = module.name;
     normalizer.arena = &currentModule->internalTypes;
@@ -1316,8 +1318,24 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatForIn& forin)
             // Extract the remaining return values of the call
             // and check them against the parameter types of the iterator function.
             auto [types, tail] = flatten(callRetPack);
-            std::vector<TypeId> argTypes = std::vector<TypeId>(types.begin() + 1, types.end());
+
-            argPack = addTypePack(TypePackVar{TypePack{std::move(argTypes), tail}});
+            if (FFlag::LuauStatForInFix)
+            {
+                if (!types.empty())
+                {
+                    std::vector<TypeId> argTypes = std::vector<TypeId>(types.begin() + 1, types.end());
+                    argPack = addTypePack(TypePackVar{TypePack{std::move(argTypes), tail}});
+                }
+                else
+                {
+                    argPack = addTypePack(TypePack{});
+                }
+            }
+            else
+            {
+                std::vector<TypeId> argTypes = std::vector<TypeId>(types.begin() + 1, types.end());
+                argPack = addTypePack(TypePackVar{TypePack{std::move(argTypes), tail}});
+            }
         }
         else
         {
@@ -1655,7 +1673,10 @@ void TypeChecker::prototype(const ScopePtr& scope, const AstStatTypeAlias& typea
             FreeType* ftv = getMutable<FreeType>(ty);
             LUAU_ASSERT(ftv);
             ftv->forwardedTypeAlias = true;
-            bindingsMap[name] = {std::move(generics), std::move(genericPacks), ty};
+            if (FFlag::LuauRetainDefinitionAliasLocations)
+                bindingsMap[name] = {std::move(generics), std::move(genericPacks), ty, typealias.location};
+            else
+                bindingsMap[name] = {std::move(generics), std::move(genericPacks), ty};
 
             scope->typeAliasLocations[name] = typealias.location;
             scope->typeAliasNameLocations[name] = typealias.nameLocation;
@@ -1700,7 +1721,10 @@ void TypeChecker::prototype(const ScopePtr& scope, const AstStatDeclareClass& de
     TypeId metaTy = addType(TableType{TableState::Sealed, scope->level});
 
     ctv->metatable = metaTy;
-    scope->exportedTypeBindings[className] = TypeFun{{}, classTy};
+    if (FFlag::LuauRetainDefinitionAliasLocations)
+        scope->exportedTypeBindings[className] = TypeFun{{}, classTy, declaredClass.location};
+    else
+        scope->exportedTypeBindings[className] = TypeFun{{}, classTy};
 }
 
 ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatDeclareClass& declaredClass)
@@ -5212,12 +5236,9 @@ LUAU_NOINLINE void TypeChecker::reportErrorCodeTooComplex(const Location& locati
 ScopePtr TypeChecker::childFunctionScope(const ScopePtr& parent, const Location& location, int subLevel)
 {
     ScopePtr scope = std::make_shared<Scope>(parent, subLevel);
-    if (FFlag::LuauOldSolverCreatesChildScopePointers)
+    scope->location = location;
-    {
+    scope->returnType = parent->returnType;
-        scope->location = location;
+    parent->children.emplace_back(scope.get());
-        scope->returnType = parent->returnType;
-        parent->children.emplace_back(scope.get());
-    }
 
     currentModule->scopes.push_back(std::make_pair(location, scope));
     return scope;
@@ -5229,12 +5250,9 @@ ScopePtr TypeChecker::childScope(const ScopePtr& parent, const Location& locatio
     ScopePtr scope = std::make_shared<Scope>(parent);
     scope->level = parent->level;
     scope->varargPack = parent->varargPack;
-    if (FFlag::LuauOldSolverCreatesChildScopePointers)
+    scope->location = location;
-    {
+    scope->returnType = parent->returnType;
-        scope->location = location;
+    parent->children.emplace_back(scope.get());
-        scope->returnType = parent->returnType;
-        parent->children.emplace_back(scope.get());
-    }
 
     currentModule->scopes.push_back(std::make_pair(location, scope));
     return scope;
@@ -5724,6 +5742,10 @@ TypeId TypeChecker::resolveTypeWorker(const ScopePtr& scope, const AstType& anno
         TypeId ty = checkExpr(scope, *typeOf->expr).type;
         return ty;
     }
+    else if (annotation.is<AstTypeOptional>())
+    {
+        return builtinTypes->nilType;
+    }
     else if (const auto& un = annotation.as<AstTypeUnion>())
     {
         if (FFlag::LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)

Analysis/src/TypePack.cpp

@@ -6,7 +6,7 @@
 
 #include <stdexcept>
 
-LUAU_FASTFLAG(LuauSolverV2);
+LUAU_FASTFLAGVARIABLE(LuauTypePackDetectCycles)
 
 namespace Luau
 {
@@ -18,10 +18,11 @@ FreeTypePack::FreeTypePack(TypeLevel level)
 {
 }
 
-FreeTypePack::FreeTypePack(Scope* scope)
+FreeTypePack::FreeTypePack(Scope* scope, Polarity polarity)
     : index(Unifiable::freshIndex())
     , level{}
     , scope(scope)
+    , polarity(polarity)
 {
 }
 
@@ -52,9 +53,10 @@ GenericTypePack::GenericTypePack(const Name& name)
 {
 }
 
-GenericTypePack::GenericTypePack(Scope* scope)
+GenericTypePack::GenericTypePack(Scope* scope, Polarity polarity)
     : index(Unifiable::freshIndex())
     , scope(scope)
+    , polarity(polarity)
 {
 }
 
@@ -147,6 +149,15 @@ TypePackIterator& TypePackIterator::operator++()
         currentTypePack = tp->tail ? log->follow(*tp->tail) : nullptr;
         tp = currentTypePack ? log->getMutable<TypePack>(currentTypePack) : nullptr;
 
+        if (FFlag::LuauTypePackDetectCycles && tp)
+        {
+            // Step twice on each iteration to detect cycles
+            tailCycleCheck = tp->tail ? log->follow(*tp->tail) : nullptr;
+
+            if (currentTypePack == tailCycleCheck)
+                throw InternalCompilerError("TypePackIterator detected a type pack cycle");
+        }
+
         currentIndex = 0;
     }
 

Analysis/src/TypePath.cpp

@@ -14,7 +14,8 @@
 #include <type_traits>
 
 LUAU_FASTFLAG(LuauSolverV2);
-LUAU_FASTFLAGVARIABLE(LuauDisableNewSolverAssertsInMixedMode);
+LUAU_FASTFLAGVARIABLE(LuauDisableNewSolverAssertsInMixedMode)
+
 // Maximum number of steps to follow when traversing a path. May not always
 // equate to the number of components in a path, depending on the traversal
 // logic.
@@ -638,6 +639,247 @@ std::string toString(const TypePath::Path& path, bool prefixDot)
     return result.str();
 }
 
+std::string toStringHuman(const TypePath::Path& path)
+{
+    LUAU_ASSERT(FFlag::LuauSolverV2);
+
+    enum class State
+    {
+        Initial,
+        Normal,
+        Property,
+        PendingIs,
+        PendingAs,
+        PendingWhich,
+    };
+
+    std::stringstream result;
+    State state = State::Initial;
+    bool last = false;
+
+    auto strComponent = [&](auto&& c)
+    {
+        using T = std::decay_t<decltype(c)>;
+        if constexpr (std::is_same_v<T, TypePath::Property>)
+        {
+            if (state == State::PendingIs)
+                result << ", ";
+
+            switch (state)
+            {
+            case State::Initial:
+            case State::PendingIs:
+                if (c.isRead)
+                    result << "accessing `";
+                else
+                    result << "writing to `";
+                break;
+            case State::Property:
+                // if the previous state was a property, then we're doing a sequence of indexing
+                result << '.';
+                break;
+            default:
+                break;
+            }
+
+            result << c.name;
+
+            state = State::Property;
+        }
+        else if constexpr (std::is_same_v<T, TypePath::Index>)
+        {
+            size_t humanIndex = c.index + 1;
+
+            if (state == State::Initial && !last)
+                result << "in" << ' ';
+            else if (state == State::PendingIs)
+                result << ' ' << "has" << ' ';
+            else if (state == State::Property)
+                result << '`' << ' ' << "has" << ' ';
+
+            result << "the " << humanIndex;
+            switch (humanIndex)
+            {
+            case 1:
+                result << "st";
+                break;
+            case 2:
+                result << "nd";
+                break;
+            case 3:
+                result << "rd";
+                break;
+            default:
+                result << "th";
+            }
+
+            switch (c.variant)
+            {
+            case TypePath::Index::Variant::Pack:
+                result << ' ' << "entry in the type pack";
+                break;
+            case TypePath::Index::Variant::Union:
+                result << ' ' << "component of the union";
+                break;
+            case TypePath::Index::Variant::Intersection:
+                result << ' ' << "component of the intersection";
+                break;
+            }
+
+            if (state == State::PendingWhich)
+                result << ' ' << "which";
+
+            if (state == State::PendingIs || state == State::Property)
+                state = State::PendingAs;
+            else
+                state = State::PendingIs;
+        }
+        else if constexpr (std::is_same_v<T, TypePath::TypeField>)
+        {
+            if (state == State::Initial && !last)
+                result << "in" << ' ';
+            else if (state == State::PendingIs)
+                result << ", ";
+            else if (state == State::Property)
+                result << '`' << ' ' << "has" << ' ';
+
+            switch (c)
+            {
+            case TypePath::TypeField::Table:
+                result << "the table portion";
+                if (state == State::Property)
+                    state = State::PendingAs;
+                else
+                    state = State::PendingIs;
+                break;
+            case TypePath::TypeField::Metatable:
+                result << "the metatable portion";
+                if (state == State::Property)
+                    state = State::PendingAs;
+                else
+                    state = State::PendingIs;
+                break;
+            case TypePath::TypeField::LowerBound:
+                result << "the lower bound of" << ' ';
+                state = State::Normal;
+                break;
+            case TypePath::TypeField::UpperBound:
+                result << "the upper bound of" << ' ';
+                state = State::Normal;
+                break;
+            case TypePath::TypeField::IndexLookup:
+                result << "the index type";
+                if (state == State::Property)
+                    state = State::PendingAs;
+                else
+                    state = State::PendingIs;
+                break;
+            case TypePath::TypeField::IndexResult:
+                result << "the result of indexing";
+                if (state == State::Property)
+                    state = State::PendingAs;
+                else
+                    state = State::PendingIs;
+                break;
+            case TypePath::TypeField::Negated:
+                result << "the negation" << ' ';
+                state = State::Normal;
+                break;
+            case TypePath::TypeField::Variadic:
+                result << "the variadic" << ' ';
+                state = State::Normal;
+                break;
+            }
+        }
+        else if constexpr (std::is_same_v<T, TypePath::PackField>)
+        {
+            if (state == State::PendingIs)
+                result << ", ";
+            else if (state == State::Property)
+                result << "`, ";
+
+            switch (c)
+            {
+            case TypePath::PackField::Arguments:
+                if (state == State::Initial)
+                    result << "it" << ' ';
+                else if (state == State::PendingIs)
+                    result << "the function" << ' ';
+
+                result << "takes";
+                break;
+            case TypePath::PackField::Returns:
+                if (state == State::Initial)
+                    result << "it" << ' ';
+                else if (state == State::PendingIs)
+                    result << "the function" << ' ';
+
+                result << "returns";
+                break;
+            case TypePath::PackField::Tail:
+                if (state == State::Initial)
+                    result << "it has" << ' ';
+                result << "a tail of";
+                break;
+            }
+
+            if (state == State::PendingIs)
+            {
+                result << ' ';
+                state = State::PendingWhich;
+            }
+            else
+            {
+                result << ' ';
+                state = State::Normal;
+            }
+        }
+        else if constexpr (std::is_same_v<T, TypePath::Reduction>)
+        {
+            if (state == State::Initial)
+                result << "it" << ' ';
+            result << "reduces to" << ' ';
+            state = State::Normal;
+        }
+        else
+        {
+            static_assert(always_false_v<T>, "Unhandled Component variant");
+        }
+    };
+
+    size_t count = 0;
+
+    for (const TypePath::Component& component : path.components)
+    {
+        count++;
+        if (count == path.components.size())
+            last = true;
+
+        Luau::visit(strComponent, component);
+    }
+
+    switch (state)
+    {
+    case State::Property:
+        result << "` results in ";
+        break;
+    case State::PendingWhich:
+        // pending `which` becomes `is` if it's at the end
+        result << "is" << ' ';
+        break;
+    case State::PendingIs:
+        result << ' ' << "is" << ' ';
+        break;
+    case State::PendingAs:
+        result << ' ' << "as" << ' ';
+        break;
+    default:
+        break;
+    }
+
+    return result.str();
+}
+
 static bool traverse(TraversalState& state, const Path& path)
 {
     auto step = [&state](auto&& c)

Analysis/src/TypeUtils.cpp

@@ -14,7 +14,9 @@ LUAU_FASTFLAG(LuauSolverV2);
 LUAU_FASTFLAG(LuauAutocompleteRefactorsForIncrementalAutocomplete);
 LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope);
 LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+LUAU_FASTFLAG(LuauNonReentrantGeneralization)
 LUAU_FASTFLAG(LuauDisableNewSolverAssertsInMixedMode)
+
 namespace Luau
 {
 
@@ -304,7 +306,11 @@ TypePack extendTypePack(
             // also have to create a new tail.
 
             TypePack newPack;
-            newPack.tail = arena.freshTypePack(ftp->scope);
+            newPack.tail = arena.freshTypePack(ftp->scope, ftp->polarity);
+
+            if (FFlag::LuauNonReentrantGeneralization)
+                trackInteriorFreeTypePack(ftp->scope, *newPack.tail);
+
             if (FFlag::LuauSolverV2)
                 result.tail = newPack.tail;
             size_t overridesIndex = 0;
@@ -319,7 +325,7 @@ TypePack extendTypePack(
                 {
                     if (FFlag::LuauSolverV2)
                     {
-                        FreeType ft{ftp->scope, builtinTypes->neverType, builtinTypes->unknownType};
+                        FreeType ft{ftp->scope, builtinTypes->neverType, builtinTypes->unknownType, ftp->polarity};
                         t = arena.addType(ft);
                         if (FFlag::LuauTrackInteriorFreeTypesOnScope)
                             trackInteriorFreeType(ftp->scope, t);
@@ -568,4 +574,24 @@ void trackInteriorFreeType(Scope* scope, TypeId ty)
     LUAU_ASSERT(!"No scopes in parent chain had a present `interiorFreeTypes` member.");
 }
 
+void trackInteriorFreeTypePack(Scope* scope, TypePackId tp)
+{
+    LUAU_ASSERT(tp);
+    if (!FFlag::LuauNonReentrantGeneralization)
+        return;
+
+    for (; scope; scope = scope->parent.get())
+    {
+        if (scope->interiorFreeTypePacks)
+        {
+            scope->interiorFreeTypePacks->push_back(tp);
+            return;
+        }
+    }
+    // There should at least be *one* generalization constraint per module
+    // where `interiorFreeTypes` is present, which would be the one made
+    // by ConstraintGenerator::visitModuleRoot.
+    LUAU_ASSERT(!"No scopes in parent chain had a present `interiorFreeTypePacks` member.");
+}
+
 } // namespace Luau

Analysis/src/TypedAllocator.cpp

@@ -24,6 +24,7 @@ const size_t kPageSize = sysconf(_SC_PAGESIZE);
 #endif
 #endif
 
+#include <stdint.h>
 #include <stdlib.h>
 
 LUAU_FASTFLAG(DebugLuauFreezeArena)

Analysis/src/Unifier2.cpp

@@ -18,6 +18,9 @@
 #include <optional>
 
 LUAU_FASTINT(LuauTypeInferRecursionLimit)
+LUAU_FASTFLAGVARIABLE(LuauUnifyMetatableWithAny)
+LUAU_FASTFLAG(LuauExtraFollows)
+LUAU_FASTFLAG(LuauNonReentrantGeneralization)
 
 namespace Luau
 {
@@ -235,6 +238,10 @@ bool Unifier2::unify(TypeId subTy, TypeId superTy)
     auto superMetatable = get<MetatableType>(superTy);
     if (subMetatable && superMetatable)
         return unify(subMetatable, superMetatable);
+    else if (FFlag::LuauUnifyMetatableWithAny && subMetatable && superAny)
+        return unify(subMetatable, superAny);
+    else if (FFlag::LuauUnifyMetatableWithAny && subAny && superMetatable)
+        return unify(subAny, superMetatable);
     else if (subMetatable) // if we only have one metatable, unify with the inner table
         return unify(subMetatable->table, superTy);
     else if (superMetatable) // if we only have one metatable, unify with the inner table
@@ -277,7 +284,7 @@ bool Unifier2::unifyFreeWithType(TypeId subTy, TypeId superTy)
     if (superArgTail)
         return doDefault();
 
-    const IntersectionType* upperBoundIntersection = get<IntersectionType>(subFree->upperBound);
+    const IntersectionType* upperBoundIntersection = get<IntersectionType>(FFlag::LuauExtraFollows ? upperBound : subFree->upperBound);
     if (!upperBoundIntersection)
         return doDefault();
 
@@ -315,10 +322,23 @@ bool Unifier2::unify(TypeId subTy, const FunctionType* superFn)
     if (shouldInstantiate)
     {
         for (auto generic : subFn->generics)
-            genericSubstitutions[generic] = freshType(arena, builtinTypes, scope);
+        {
+            const GenericType* gen = get<GenericType>(generic);
+            LUAU_ASSERT(gen);
+            genericSubstitutions[generic] = freshType(scope, gen->polarity);
+        }
 
         for (auto genericPack : subFn->genericPacks)
-            genericPackSubstitutions[genericPack] = arena->freshTypePack(scope);
+        {
+            if (FFlag::LuauNonReentrantGeneralization)
+            {
+                const GenericTypePack* gen = get<GenericTypePack>(genericPack);
+                LUAU_ASSERT(gen);
+                genericPackSubstitutions[genericPack] = freshTypePack(scope, gen->polarity);
+            }
+            else
+                genericPackSubstitutions[genericPack] = arena->freshTypePack(scope);
+        }
     }
 
     bool argResult = unify(superFn->argTypes, subFn->argTypes);
@@ -427,9 +447,6 @@ bool Unifier2::unify(TableType* subTable, const TableType* superTable)
         superTypePackParamsIter++;
     }
 
-    if (subTable->selfTy && superTable->selfTy)
-        result &= unify(*subTable->selfTy, *superTable->selfTy);
-
     if (subTable->indexer && superTable->indexer)
     {
         result &= unify(subTable->indexer->indexType, superTable->indexer->indexType);
@@ -524,6 +541,16 @@ bool Unifier2::unify(const TableType* subTable, const AnyType* superAny)
     return true;
 }
 
+bool Unifier2::unify(const MetatableType* subMetatable, const AnyType*)
+{
+    return unify(subMetatable->metatable, builtinTypes->anyType) && unify(subMetatable->table, builtinTypes->anyType);
+}
+
+bool Unifier2::unify(const AnyType*, const MetatableType* superMetatable)
+{
+    return unify(builtinTypes->anyType, superMetatable->metatable) && unify(builtinTypes->anyType, superMetatable->table);
+}
+
 // FIXME?  This should probably return an ErrorVec or an optional<TypeError>
 // rather than a boolean to signal an occurs check failure.
 bool Unifier2::unify(TypePackId subTp, TypePackId superTp)
@@ -634,38 +661,33 @@ struct FreeTypeSearcher : TypeVisitor
     {
     }
 
-    enum Polarity
+    Polarity polarity = Polarity::Positive;
-    {
-        Positive,
-        Negative,
-        Both,
-    };
-
-    Polarity polarity = Positive;
 
     void flip()
     {
         switch (polarity)
         {
-        case Positive:
+        case Polarity::Positive:
-            polarity = Negative;
+            polarity = Polarity::Negative;
             break;
-        case Negative:
+        case Polarity::Negative:
-            polarity = Positive;
+            polarity = Polarity::Positive;
             break;
-        case Both:
+        case Polarity::Mixed:
             break;
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
     }
 
     DenseHashSet<const void*> seenPositive{nullptr};
     DenseHashSet<const void*> seenNegative{nullptr};
 
-    bool seenWithPolarity(const void* ty)
+    bool seenWithCurrentPolarity(const void* ty)
     {
         switch (polarity)
         {
-        case Positive:
+        case Polarity::Positive:
         {
             if (seenPositive.contains(ty))
                 return true;
@@ -673,7 +695,7 @@ struct FreeTypeSearcher : TypeVisitor
             seenPositive.insert(ty);
             return false;
         }
-        case Negative:
+        case Polarity::Negative:
         {
             if (seenNegative.contains(ty))
                 return true;
@@ -681,7 +703,7 @@ struct FreeTypeSearcher : TypeVisitor
             seenNegative.insert(ty);
             return false;
         }
-        case Both:
+        case Polarity::Mixed:
         {
             if (seenPositive.contains(ty) && seenNegative.contains(ty))
                 return true;
@@ -690,6 +712,8 @@ struct FreeTypeSearcher : TypeVisitor
             seenNegative.insert(ty);
             return false;
         }
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
 
         return false;
@@ -703,7 +727,7 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty) override
     {
-        if (seenWithPolarity(ty))
+        if (seenWithCurrentPolarity(ty))
             return false;
 
         LUAU_ASSERT(ty);
@@ -712,7 +736,7 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const FreeType& ft) override
     {
-        if (seenWithPolarity(ty))
+        if (seenWithCurrentPolarity(ty))
             return false;
 
         if (!subsumes(scope, ft.scope))
@@ -720,16 +744,18 @@ struct FreeTypeSearcher : TypeVisitor
 
         switch (polarity)
         {
-        case Positive:
+        case Polarity::Positive:
             positiveTypes[ty]++;
             break;
-        case Negative:
+        case Polarity::Negative:
             negativeTypes[ty]++;
             break;
-        case Both:
+        case Polarity::Mixed:
             positiveTypes[ty]++;
             negativeTypes[ty]++;
             break;
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
 
         return true;
@@ -737,23 +763,25 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const TableType& tt) override
     {
-        if (seenWithPolarity(ty))
+        if (seenWithCurrentPolarity(ty))
             return false;
 
         if ((tt.state == TableState::Free || tt.state == TableState::Unsealed) && subsumes(scope, tt.scope))
         {
             switch (polarity)
             {
-            case Positive:
+            case Polarity::Positive:
                 positiveTypes[ty]++;
                 break;
-            case Negative:
+            case Polarity::Negative:
                 negativeTypes[ty]++;
                 break;
-            case Both:
+            case Polarity::Mixed:
                 positiveTypes[ty]++;
                 negativeTypes[ty]++;
                 break;
+            default:
+                LUAU_ASSERT(!"Unreachable");
             }
         }
 
@@ -766,7 +794,7 @@ struct FreeTypeSearcher : TypeVisitor
                 LUAU_ASSERT(prop.isShared());
 
                 Polarity p = polarity;
-                polarity = Both;
+                polarity = Polarity::Mixed;
                 traverse(prop.type());
                 polarity = p;
             }
@@ -783,7 +811,7 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypeId ty, const FunctionType& ft) override
     {
-        if (seenWithPolarity(ty))
+        if (seenWithCurrentPolarity(ty))
             return false;
 
         flip();
@@ -802,7 +830,7 @@ struct FreeTypeSearcher : TypeVisitor
 
     bool visit(TypePackId tp, const FreeTypePack& ftp) override
     {
-        if (seenWithPolarity(tp))
+        if (seenWithCurrentPolarity(tp))
             return false;
 
         if (!subsumes(scope, ftp.scope))
@@ -810,16 +838,18 @@ struct FreeTypeSearcher : TypeVisitor
 
         switch (polarity)
         {
-        case Positive:
+        case Polarity::Positive:
             positiveTypes[tp]++;
             break;
-        case Negative:
+        case Polarity::Negative:
             negativeTypes[tp]++;
             break;
-        case Both:
+        case Polarity::Mixed:
             positiveTypes[tp]++;
             negativeTypes[tp]++;
             break;
+        default:
+            LUAU_ASSERT(!"Unreachable");
         }
 
         return true;
@@ -925,4 +955,23 @@ OccursCheckResult Unifier2::occursCheck(DenseHashSet<TypePackId>& seen, TypePack
     return OccursCheckResult::Pass;
 }
 
+TypeId Unifier2::freshType(NotNull<Scope> scope, Polarity polarity)
+{
+    TypeId result = ::Luau::freshType(arena, builtinTypes, scope.get(), polarity);
+    newFreshTypes.emplace_back(result);
+    return result;
+}
+
+TypePackId Unifier2::freshTypePack(NotNull<Scope> scope, Polarity polarity)
+{
+    TypePackId result = arena->freshTypePack(scope.get());
+
+    auto ftp = getMutable<FreeTypePack>(result);
+    LUAU_ASSERT(ftp);
+    ftp->polarity = polarity;
+
+    newFreshTypePacks.emplace_back(result);
+    return result;
+}
+
 } // namespace Luau

Ast/include/Luau/Ast.h

@@ -194,6 +194,7 @@ public:
     {
         Checked,
         Native,
+        Deprecated,
     };
 
     AstAttr(const Location& location, Type type);
@@ -453,6 +454,7 @@ public:
     void visit(AstVisitor* visitor) override;
 
     bool hasNativeAttribute() const;
+    bool hasAttribute(AstAttr::Type attributeType) const;
 
     AstArray<AstAttr*> attributes;
     AstArray<AstGenericType*> generics;
@@ -890,14 +892,22 @@ class AstStatTypeFunction : public AstStat
 public:
     LUAU_RTTI(AstStatTypeFunction);
 
-    AstStatTypeFunction(const Location& location, const AstName& name, const Location& nameLocation, AstExprFunction* body, bool exported);
+    AstStatTypeFunction(
+        const Location& location,
+        const AstName& name,
+        const Location& nameLocation,
+        AstExprFunction* body,
+        bool exported,
+        bool hasErrors
+    );
 
     void visit(AstVisitor* visitor) override;
 
     AstName name;
     Location nameLocation;
-    AstExprFunction* body;
+    AstExprFunction* body = nullptr;
-    bool exported;
+    bool exported = false;
+    bool hasErrors = false;
 };
 
 class AstStatDeclareGlobal : public AstStat
@@ -950,6 +960,7 @@ public:
     void visit(AstVisitor* visitor) override;
 
     bool isCheckedFunction() const;
+    bool hasAttribute(AstAttr::Type attributeType) const;
 
     AstArray<AstAttr*> attributes;
     AstName name;
@@ -1106,6 +1117,7 @@ public:
     void visit(AstVisitor* visitor) override;
 
     bool isCheckedFunction() const;
+    bool hasAttribute(AstAttr::Type attributeType) const;
 
     AstArray<AstAttr*> attributes;
     AstArray<AstGenericType*> generics;
@@ -1127,6 +1139,16 @@ public:
     AstExpr* expr;
 };
 
+class AstTypeOptional : public AstType
+{
+public:
+    LUAU_RTTI(AstTypeOptional)
+
+    AstTypeOptional(const Location& location);
+
+    void visit(AstVisitor* visitor) override;
+};
+
 class AstTypeUnion : public AstType
 {
 public:
@@ -1449,6 +1471,10 @@ public:
     {
         return visit(static_cast<AstStat*>(node));
     }
+    virtual bool visit(class AstStatTypeFunction* node)
+    {
+        return visit(static_cast<AstStat*>(node));
+    }
     virtual bool visit(class AstStatDeclareFunction* node)
     {
         return visit(static_cast<AstStat*>(node));
@@ -1488,6 +1514,10 @@ public:
     {
         return visit(static_cast<AstType*>(node));
     }
+    virtual bool visit(class AstTypeOptional* node)
+    {
+        return visit(static_cast<AstType*>(node));
+    }
     virtual bool visit(class AstTypeUnion* node)
     {
         return visit(static_cast<AstType*>(node));

Ast/include/Luau/Cst.h

@@ -105,6 +105,21 @@ public:
     Position closeBracketPosition;
 };
 
+class CstExprFunction : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstExprFunction)
+
+    CstExprFunction();
+
+    Position functionKeywordPosition{0, 0};
+    Position openGenericsPosition{0, 0};
+    AstArray<Position> genericsCommaPositions;
+    Position closeGenericsPosition{0, 0};
+    AstArray<Position> argsCommaPositions;
+    Position returnSpecifierPosition{0, 0};
+};
+
 class CstExprTable : public CstNode
 {
 public:
@@ -260,13 +275,24 @@ public:
     Position opPosition;
 };
 
+class CstStatFunction : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstStatFunction)
+
+    explicit CstStatFunction(Position functionKeywordPosition);
+
+    Position functionKeywordPosition;
+};
+
 class CstStatLocalFunction : public CstNode
 {
 public:
     LUAU_CST_RTTI(CstStatLocalFunction)
 
-    explicit CstStatLocalFunction(Position functionKeywordPosition);
+    explicit CstStatLocalFunction(Position localKeywordPosition, Position functionKeywordPosition);
 
+    Position localKeywordPosition;
     Position functionKeywordPosition;
 };
 
@@ -311,6 +337,17 @@ public:
     Position equalsPosition;
 };
 
+class CstStatTypeFunction : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstStatTypeFunction)
+
+    CstStatTypeFunction(Position typeKeywordPosition, Position functionKeywordPosition);
+
+    Position typeKeywordPosition;
+    Position functionKeywordPosition;
+};
+
 class CstTypeReference : public CstNode
 {
 public:
@@ -359,6 +396,32 @@ public:
     bool isArray = false;
 };
 
+class CstTypeFunction : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstTypeFunction)
+
+    CstTypeFunction(
+        Position openGenericsPosition,
+        AstArray<Position> genericsCommaPositions,
+        Position closeGenericsPosition,
+        Position openArgsPosition,
+        AstArray<std::optional<Position>> argumentNameColonPositions,
+        AstArray<Position> argumentsCommaPositions,
+        Position closeArgsPosition,
+        Position returnArrowPosition
+    );
+
+    Position openGenericsPosition;
+    AstArray<Position> genericsCommaPositions;
+    Position closeGenericsPosition;
+    Position openArgsPosition;
+    AstArray<std::optional<Position>> argumentNameColonPositions;
+    AstArray<Position> argumentsCommaPositions;
+    Position closeArgsPosition;
+    Position returnArrowPosition;
+};
+
 class CstTypeTypeof : public CstNode
 {
 public:
@@ -370,6 +433,28 @@ public:
     Position closePosition;
 };
 
+class CstTypeUnion : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstTypeUnion)
+
+    CstTypeUnion(std::optional<Position> leadingPosition, AstArray<Position> separatorPositions);
+
+    std::optional<Position> leadingPosition;
+    AstArray<Position> separatorPositions;
+};
+
+class CstTypeIntersection : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstTypeIntersection)
+
+    explicit CstTypeIntersection(std::optional<Position> leadingPosition, AstArray<Position> separatorPositions);
+
+    std::optional<Position> leadingPosition;
+    AstArray<Position> separatorPositions;
+};
+
 class CstTypeSingletonString : public CstNode
 {
 public:
@@ -382,4 +467,26 @@ public:
     unsigned int blockDepth;
 };
 
+class CstTypePackExplicit : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstTypePackExplicit)
+
+    CstTypePackExplicit(Position openParenthesesPosition, Position closeParenthesesPosition, AstArray<Position> commaPositions);
+
+    Position openParenthesesPosition;
+    Position closeParenthesesPosition;
+    AstArray<Position> commaPositions;
+};
+
+class CstTypePackGeneric : public CstNode
+{
+public:
+    LUAU_CST_RTTI(CstTypePackGeneric)
+
+    explicit CstTypePackGeneric(Position ellipsisPosition);
+
+    Position ellipsisPosition;
+};
+
 } // namespace Luau

Ast/include/Luau/Parser.h

@@ -125,7 +125,7 @@ private:
     AstStat* parseFor();
 
     // funcname ::= Name {`.' Name} [`:' Name]
-    AstExpr* parseFunctionName(Location start_DEPRECATED, bool& hasself, AstName& debugname);
+    AstExpr* parseFunctionName(bool& hasself, AstName& debugname);
 
     // function funcname funcbody
     LUAU_FORCEINLINE AstStat* parseFunctionStat(const AstArray<AstAttr*>& attributes = {nullptr, 0});
@@ -155,9 +155,11 @@ private:
     AstStat* parseTypeAlias(const Location& start, bool exported, Position typeKeywordPosition);
 
     // type function Name ... end
-    AstStat* parseTypeFunction(const Location& start, bool exported);
+    AstStat* parseTypeFunction(const Location& start, bool exported, Position typeKeywordPosition);
+
+    AstDeclaredClassProp parseDeclaredClassMethod(const AstArray<AstAttr*>& attributes);
+    AstDeclaredClassProp parseDeclaredClassMethod_DEPRECATED();
 
-    AstDeclaredClassProp parseDeclaredClassMethod();
 
     // `declare global' Name: Type |
     // `declare function' Name`(' [parlist] `)' [`:` Type]
@@ -192,7 +194,8 @@ private:
     std::tuple<bool, Location, AstTypePack*> parseBindingList(
         TempVector<Binding>& result,
         bool allowDot3 = false,
-        TempVector<Position>* commaPositions = nullptr
+        AstArray<Position>* commaPositions = nullptr,
+        std::optional<Position> initialCommaPosition = std::nullopt
     );
 
     AstType* parseOptionalType();
@@ -209,9 +212,14 @@ private:
     //      |   `(' [TypeList] `)' `->` ReturnType
 
     // Returns the variadic annotation, if it exists.
-    AstTypePack* parseTypeList(TempVector<AstType*>& result, TempVector<std::optional<AstArgumentName>>& resultNames);
+    AstTypePack* parseTypeList(
+        TempVector<AstType*>& result,
+        TempVector<std::optional<AstArgumentName>>& resultNames,
+        TempVector<Position>* commaPositions = nullptr,
+        TempVector<std::optional<Position>>* nameColonPositions = nullptr
+    );
 
-    std::optional<AstTypeList> parseOptionalReturnType();
+    std::optional<AstTypeList> parseOptionalReturnType(Position* returnSpecifierPosition = nullptr);
     std::pair<Location, AstTypeList> parseReturnType();
 
     struct TableIndexerResult
@@ -222,9 +230,9 @@ private:
         Position colonPosition;
     };
 
-    TableIndexerResult parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation);
+    TableIndexerResult parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin);
-    // Remove with FFlagLuauStoreCSTData
+    // Remove with FFlagLuauStoreCSTData2
-    AstTableIndexer* parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation);
+    AstTableIndexer* parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin);
 
     AstTypeOrPack parseFunctionType(bool allowPack, const AstArray<AstAttr*>& attributes);
     AstType* parseFunctionTypeTail(
@@ -305,7 +313,7 @@ private:
     std::pair<AstArray<AstGenericType*>, AstArray<AstGenericTypePack*>> parseGenericTypeList(
         bool withDefaultValues,
         Position* openPosition = nullptr,
-        TempVector<Position>* commaPositions = nullptr,
+        AstArray<Position>* commaPositions = nullptr,
         Position* closePosition = nullptr
     );
 
@@ -491,6 +499,7 @@ private:
     std::vector<AstGenericTypePack*> scratchGenericTypePacks;
     std::vector<std::optional<AstArgumentName>> scratchOptArgName;
     std::vector<Position> scratchPosition;
+    std::vector<std::optional<Position>> scratchOptPosition;
     std::string scratchData;
 
     CstNodeMap cstNodeMap;

Ast/src/Ast.cpp

@@ -3,9 +3,24 @@
 
 #include "Luau/Common.h"
 
+LUAU_FASTFLAG(LuauDeprecatedAttribute);
+
 namespace Luau
 {
 
+static bool hasAttributeInArray(const AstArray<AstAttr*> attributes, AstAttr::Type attributeType)
+{
+    LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+    for (const auto attribute : attributes)
+    {
+        if (attribute->type == attributeType)
+            return true;
+    }
+
+    return false;
+}
+
 static void visitTypeList(AstVisitor* visitor, const AstTypeList& list)
 {
     for (AstType* ty : list.types)
@@ -277,6 +292,13 @@ bool AstExprFunction::hasNativeAttribute() const
     return false;
 }
 
+bool AstExprFunction::hasAttribute(const AstAttr::Type attributeType) const
+{
+    LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+    return hasAttributeInArray(attributes, attributeType);
+}
+
 AstExprTable::AstExprTable(const Location& location, const AstArray<Item>& items)
     : AstExpr(ClassIndex(), location)
     , items(items)
@@ -791,13 +813,15 @@ AstStatTypeFunction::AstStatTypeFunction(
     const AstName& name,
     const Location& nameLocation,
     AstExprFunction* body,
-    bool exported
+    bool exported,
+    bool hasErrors
 )
     : AstStat(ClassIndex(), location)
     , name(name)
     , nameLocation(nameLocation)
     , body(body)
     , exported(exported)
+    , hasErrors(hasErrors)
 {
 }
 
@@ -894,6 +918,13 @@ bool AstStatDeclareFunction::isCheckedFunction() const
     return false;
 }
 
+bool AstStatDeclareFunction::hasAttribute(AstAttr::Type attributeType) const
+{
+    LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+    return hasAttributeInArray(attributes, attributeType);
+}
+
 AstStatDeclareClass::AstStatDeclareClass(
     const Location& location,
     const AstName& name,
@@ -1057,6 +1088,13 @@ bool AstTypeFunction::isCheckedFunction() const
     return false;
 }
 
+bool AstTypeFunction::hasAttribute(AstAttr::Type attributeType) const
+{
+    LUAU_ASSERT(FFlag::LuauDeprecatedAttribute);
+
+    return hasAttributeInArray(attributes, attributeType);
+}
+
 AstTypeTypeof::AstTypeTypeof(const Location& location, AstExpr* expr)
     : AstType(ClassIndex(), location)
     , expr(expr)
@@ -1069,6 +1107,16 @@ void AstTypeTypeof::visit(AstVisitor* visitor)
         expr->visit(visitor);
 }
 
+AstTypeOptional::AstTypeOptional(const Location& location)
+    : AstType(ClassIndex(), location)
+{
+}
+
+void AstTypeOptional::visit(AstVisitor* visitor)
+{
+    visitor->visit(this);
+}
+
 AstTypeUnion::AstTypeUnion(const Location& location, const AstArray<AstType*>& types)
     : AstType(ClassIndex(), location)
     , types(types)

Ast/src/Cst.cpp

@@ -38,6 +38,11 @@ CstExprIndexExpr::CstExprIndexExpr(Position openBracketPosition, Position closeB
 {
 }
 
+CstExprFunction::CstExprFunction()
+    : CstNode(CstClassIndex())
+{
+}
+
 CstExprTable::CstExprTable(const AstArray<Item>& items)
     : CstNode(CstClassIndex())
     , items(items)
@@ -125,12 +130,19 @@ CstStatCompoundAssign::CstStatCompoundAssign(Position opPosition)
 {
 }
 
-CstStatLocalFunction::CstStatLocalFunction(Position functionKeywordPosition)
+CstStatFunction::CstStatFunction(Position functionKeywordPosition)
     : CstNode(CstClassIndex())
     , functionKeywordPosition(functionKeywordPosition)
 {
 }
 
+CstStatLocalFunction::CstStatLocalFunction(Position localKeywordPosition, Position functionKeywordPosition)
+    : CstNode(CstClassIndex())
+    , localKeywordPosition(localKeywordPosition)
+    , functionKeywordPosition(functionKeywordPosition)
+{
+}
+
 CstGenericType::CstGenericType(std::optional<Position> defaultEqualsPosition)
     : CstNode(CstClassIndex())
     , defaultEqualsPosition(defaultEqualsPosition)
@@ -160,6 +172,13 @@ CstStatTypeAlias::CstStatTypeAlias(
 {
 }
 
+CstStatTypeFunction::CstStatTypeFunction(Position typeKeywordPosition, Position functionKeywordPosition)
+    : CstNode(CstClassIndex())
+    , typeKeywordPosition(typeKeywordPosition)
+    , functionKeywordPosition(functionKeywordPosition)
+{
+}
+
 CstTypeReference::CstTypeReference(
     std::optional<Position> prefixPointPosition,
     Position openParametersPosition,
@@ -181,6 +200,28 @@ CstTypeTable::CstTypeTable(AstArray<Item> items, bool isArray)
 {
 }
 
+CstTypeFunction::CstTypeFunction(
+    Position openGenericsPosition,
+    AstArray<Position> genericsCommaPositions,
+    Position closeGenericsPosition,
+    Position openArgsPosition,
+    AstArray<std::optional<Position>> argumentNameColonPositions,
+    AstArray<Position> argumentsCommaPositions,
+    Position closeArgsPosition,
+    Position returnArrowPosition
+)
+    : CstNode(CstClassIndex())
+    , openGenericsPosition(openGenericsPosition)
+    , genericsCommaPositions(genericsCommaPositions)
+    , closeGenericsPosition(closeGenericsPosition)
+    , openArgsPosition(openArgsPosition)
+    , argumentNameColonPositions(argumentNameColonPositions)
+    , argumentsCommaPositions(argumentsCommaPositions)
+    , closeArgsPosition(closeArgsPosition)
+    , returnArrowPosition(returnArrowPosition)
+{
+}
+
 CstTypeTypeof::CstTypeTypeof(Position openPosition, Position closePosition)
     : CstNode(CstClassIndex())
     , openPosition(openPosition)
@@ -188,6 +229,20 @@ CstTypeTypeof::CstTypeTypeof(Position openPosition, Position closePosition)
 {
 }
 
+CstTypeUnion::CstTypeUnion(std::optional<Position> leadingPosition, AstArray<Position> separatorPositions)
+    : CstNode(CstClassIndex())
+    , leadingPosition(leadingPosition)
+    , separatorPositions(separatorPositions)
+{
+}
+
+CstTypeIntersection::CstTypeIntersection(std::optional<Position> leadingPosition, AstArray<Position> separatorPositions)
+    : CstNode(CstClassIndex())
+    , leadingPosition(leadingPosition)
+    , separatorPositions(separatorPositions)
+{
+}
+
 CstTypeSingletonString::CstTypeSingletonString(AstArray<char> sourceString, CstExprConstantString::QuoteStyle quoteStyle, unsigned int blockDepth)
     : CstNode(CstClassIndex())
     , sourceString(sourceString)
@@ -197,4 +252,18 @@ CstTypeSingletonString::CstTypeSingletonString(AstArray<char> sourceString, CstE
     LUAU_ASSERT(quoteStyle != CstExprConstantString::QuotedInterp);
 }
 
+CstTypePackExplicit::CstTypePackExplicit(Position openParenthesesPosition, Position closeParenthesesPosition, AstArray<Position> commaPositions)
+    : CstNode(CstClassIndex())
+    , openParenthesesPosition(openParenthesesPosition)
+    , closeParenthesesPosition(closeParenthesesPosition)
+    , commaPositions(commaPositions)
+{
+}
+
+CstTypePackGeneric::CstTypePackGeneric(Position ellipsisPosition)
+    : CstNode(CstClassIndex())
+    , ellipsisPosition(ellipsisPosition)
+{
+}
+
 } // namespace Luau

Ast/src/Lexer.cpp

@@ -8,9 +8,6 @@
 
 #include <limits.h>
 
-LUAU_FASTFLAGVARIABLE(LexerResumesFromPosition2)
-LUAU_FASTFLAGVARIABLE(LexerFixInterpStringStart)
-
 namespace Luau
 {
 
@@ -342,12 +339,9 @@ Lexer::Lexer(const char* buffer, size_t bufferSize, AstNameTable& names, Positio
     : buffer(buffer)
     , bufferSize(bufferSize)
     , offset(0)
-    , line(FFlag::LexerResumesFromPosition2 ? startPosition.line : 0)
+    , line(startPosition.line)
-    , lineOffset(FFlag::LexerResumesFromPosition2 ? 0u - startPosition.column : 0)
+    , lineOffset(0u - startPosition.column)
-    , lexeme(
+    , lexeme((Location(Position(startPosition.line, startPosition.column), 0)), Lexeme::Eof)
-          (FFlag::LexerResumesFromPosition2 ? Location(Position(startPosition.line, startPosition.column), 0) : Location(Position(0, 0), 0)),
-          Lexeme::Eof
-      )
     , names(names)
     , skipComments(false)
     , readNames(true)
@@ -793,7 +787,7 @@ Lexeme Lexer::readNext()
             return Lexeme(Location(start, 1), '}');
         }
 
-        return readInterpolatedStringSection(FFlag::LexerFixInterpStringStart ? start : position(), Lexeme::InterpStringMid, Lexeme::InterpStringEnd);
+        return readInterpolatedStringSection(start, Lexeme::InterpStringMid, Lexeme::InterpStringEnd);
     }
 
     case '=':

CLI/include/Luau/AnalyzeRequirer.h

@@ -0,0 +1,35 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/RequireNavigator.h"
+#include "Luau/RequirerUtils.h"
+
+struct FileNavigationContext : Luau::Require::NavigationContext
+{
+    using NavigateResult = Luau::Require::NavigationContext::NavigateResult;
+
+    FileNavigationContext(std::string requirerPath);
+
+    std::string getRequirerIdentifier() const override;
+
+    // Navigation interface
+    NavigateResult reset(const std::string& requirerChunkname) override;
+    NavigateResult jumpToAlias(const std::string& path) override;
+
+    NavigateResult toParent() override;
+    NavigateResult toChild(const std::string& component) override;
+
+    bool isConfigPresent() const override;
+    std::optional<std::string> getConfig() const override;
+
+    // Custom capabilities
+    bool isModulePresent() const;
+    std::optional<std::string> getIdentifier() const;
+
+    std::string path;
+    std::string suffix;
+    std::string requirerPath;
+
+private:
+    NavigateResult storePathResult(PathResult result);
+};

CLI/include/Luau/ReplRequirer.h

@@ -0,0 +1,32 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Require.h"
+
+#include "Luau/Compiler.h"
+
+#include "lua.h"
+
+#include <functional>
+#include <string>
+
+void requireConfigInit(luarequire_Configuration* config);
+
+struct ReplRequirer
+{
+    ReplRequirer(
+        std::function<Luau::CompileOptions()> copts,
+        std::function<bool()> coverageActive,
+        std::function<bool()> codegenEnabled,
+        std::function<void(lua_State*, int)> coverageTrack
+    );
+
+    std::function<Luau::CompileOptions()> copts;
+    std::function<bool()> coverageActive;
+    std::function<bool()> codegenEnabled;
+    std::function<void(lua_State*, int)> coverageTrack;
+
+    std::string absPath;
+    std::string relPath;
+    std::string suffix;
+};

CLI/include/Luau/Require.h

@@ -1,84 +0,0 @@
-// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-#pragma once
-
-#include "Luau/Config.h"
-
-#include <functional>
-#include <string>
-#include <string_view>
-
-class RequireResolver
-{
-public:
-    enum class ModuleStatus
-    {
-        Cached,
-        FileRead,
-        ErrorReported
-    };
-
-    struct ResolvedRequire
-    {
-        ModuleStatus status;
-        std::string identifier;
-        std::string absolutePath;
-        std::string sourceCode;
-    };
-
-    struct RequireContext
-    {
-        virtual ~RequireContext() = default;
-        virtual std::string getPath() = 0;
-        virtual bool isRequireAllowed() = 0;
-        virtual bool isStdin() = 0;
-        virtual std::string createNewIdentifer(const std::string& path) = 0;
-    };
-
-    struct CacheManager
-    {
-        virtual ~CacheManager() = default;
-        virtual bool isCached(const std::string& path)
-        {
-            return false;
-        }
-    };
-
-    struct ErrorHandler
-    {
-        virtual ~ErrorHandler() = default;
-        virtual void reportError(const std::string message) {}
-    };
-
-    RequireResolver(std::string pathToResolve, RequireContext& requireContext, CacheManager& cacheManager, ErrorHandler& errorHandler);
-
-    [[nodiscard]] ResolvedRequire resolveRequire(std::function<void(const ModuleStatus)> completionCallback = nullptr);
-
-private:
-    std::string pathToResolve;
-
-    RequireContext& requireContext;
-    CacheManager& cacheManager;
-    ErrorHandler& errorHandler;
-
-    ResolvedRequire resolvedRequire;
-    bool isRequireResolved = false;
-
-    Luau::Config config;
-    std::string lastSearchedDir;
-    bool isConfigFullyResolved = false;
-
-    [[nodiscard]] bool initialize();
-
-    ModuleStatus findModule();
-    ModuleStatus findModuleImpl();
-
-    [[nodiscard]] bool resolveAndStoreDefaultPaths();
-    std::optional<std::string> getRequiringContextAbsolute();
-    std::string getRequiringContextRelative();
-
-    [[nodiscard]] bool substituteAliasIfPresent(std::string& path);
-    std::optional<std::string> getAlias(std::string alias);
-
-    [[nodiscard]] bool parseNextConfig();
-    [[nodiscard]] bool parseConfigInDirectory(const std::string& directory);
-};

CLI/include/Luau/RequirerUtils.h

@@ -0,0 +1,36 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include <optional>
+#include <string>
+#include <string_view>
+
+struct PathResult
+{
+    enum class Status
+    {
+        SUCCESS,
+        AMBIGUOUS,
+        NOT_FOUND
+    };
+
+    Status status;
+    std::string absPath;
+    std::string relPath;
+    std::string suffix;
+};
+
+PathResult getStdInResult();
+
+PathResult getAbsolutePathResult(const std::string& path);
+
+// If given an absolute path, this will implicitly call getAbsolutePathResult.
+// Aliases prevent us from solely operating on relative paths, so we need to
+// be able to fall back to operating on absolute paths if needed.
+PathResult tryGetRelativePathResult(const std::string& path);
+
+PathResult getParent(const std::string& absPath, const std::string& relPath);
+PathResult getChild(const std::string& absPath, const std::string& relPath, const std::string& name);
+
+bool isFilePresent(const std::string& path, const std::string& suffix);
+std::optional<std::string> getFileContents(const std::string& path, const std::string& suffix);

CLI/src/Analyze.cpp

@@ -7,9 +7,10 @@
 #include "Luau/TypeAttach.h"
 #include "Luau/Transpiler.h"
 
+#include "Luau/AnalyzeRequirer.h"
 #include "Luau/FileUtils.h"
 #include "Luau/Flags.h"
-#include "Luau/Require.h"
+#include "Luau/RequireNavigator.h"
 
 #include <condition_variable>
 #include <functional>
@@ -173,15 +174,18 @@ struct CliFileResolver : Luau::FileResolver
         {
             std::string path{expr->value.data, expr->value.size};
 
-            AnalysisRequireContext requireContext{context->name};
+            FileNavigationContext navigationContext{context->name};
-            AnalysisCacheManager cacheManager;
+            Luau::Require::ErrorHandler nullErrorHandler{};
-            AnalysisErrorHandler errorHandler;
 
-            RequireResolver resolver(path, requireContext, cacheManager, errorHandler);
+            Luau::Require::Navigator navigator(navigationContext, nullErrorHandler);
-            RequireResolver::ResolvedRequire resolvedRequire = resolver.resolveRequire();
+            if (navigator.navigate(path) != Luau::Require::Navigator::Status::Success)
+                return std::nullopt;
 
-            if (resolvedRequire.status == RequireResolver::ModuleStatus::FileRead)
+            if (!navigationContext.isModulePresent())
-                return {{resolvedRequire.identifier}};
+                return std::nullopt;
+
+            if (std::optional<std::string> identifier = navigationContext.getIdentifier())
+                return {{*identifier}};
         }
 
         return std::nullopt;
@@ -193,48 +197,6 @@ struct CliFileResolver : Luau::FileResolver
             return "stdin";
         return name;
     }
-
-private:
-    struct AnalysisRequireContext : RequireResolver::RequireContext
-    {
-        explicit AnalysisRequireContext(std::string path)
-            : path(std::move(path))
-        {
-        }
-
-        std::string getPath() override
-        {
-            return path;
-        }
-
-        bool isRequireAllowed() override
-        {
-            return true;
-        }
-
-        bool isStdin() override
-        {
-            return path == "-";
-        }
-
-        std::string createNewIdentifer(const std::string& path) override
-        {
-            return path;
-        }
-
-    private:
-        std::string path;
-    };
-
-    struct AnalysisCacheManager : public RequireResolver::CacheManager
-    {
-        AnalysisCacheManager() = default;
-    };
-
-    struct AnalysisErrorHandler : RequireResolver::ErrorHandler
-    {
-        AnalysisErrorHandler() = default;
-    };
 };
 
 struct CliConfigResolver : Luau::ConfigResolver

CLI/src/AnalyzeRequirer.cpp

@@ -0,0 +1,99 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/AnalyzeRequirer.h"
+
+#include "Luau/RequireNavigator.h"
+#include "Luau/RequirerUtils.h"
+
+#include <string>
+#include <string_view>
+
+Luau::Require::NavigationContext::NavigateResult FileNavigationContext::storePathResult(PathResult result)
+{
+    if (result.status == PathResult::Status::AMBIGUOUS)
+        return Luau::Require::NavigationContext::NavigateResult::Ambiguous;
+
+    if (result.status == PathResult::Status::NOT_FOUND)
+        return Luau::Require::NavigationContext::NavigateResult::NotFound;
+
+    path = result.absPath;
+    suffix = result.suffix;
+
+    return Luau::Require::NavigationContext::NavigateResult::Success;
+}
+
+FileNavigationContext::FileNavigationContext(std::string requirerPath)
+{
+    std::string_view path = requirerPath;
+    if (path.size() >= 10 && path.substr(path.size() - 10) == "/init.luau")
+    {
+        path.remove_suffix(10);
+    }
+    else if (path.size() >= 9 && path.substr(path.size() - 9) == "/init.lua")
+    {
+        path.remove_suffix(9);
+    }
+    else if (path.size() >= 5 && path.substr(path.size() - 5) == ".luau")
+    {
+        path.remove_suffix(5);
+    }
+    else if (path.size() >= 4 && path.substr(path.size() - 4) == ".lua")
+    {
+        path.remove_suffix(4);
+    }
+
+    this->requirerPath = path;
+}
+
+std::string FileNavigationContext::getRequirerIdentifier() const
+{
+    return requirerPath;
+}
+
+Luau::Require::NavigationContext::NavigateResult FileNavigationContext::reset(const std::string& requirerChunkname)
+{
+    if (requirerChunkname == "-")
+    {
+        return storePathResult(getStdInResult());
+    }
+
+    return storePathResult(tryGetRelativePathResult(requirerChunkname));
+}
+
+Luau::Require::NavigationContext::NavigateResult FileNavigationContext::jumpToAlias(const std::string& path)
+{
+    Luau::Require::NavigationContext::NavigateResult result = storePathResult(getAbsolutePathResult(path));
+    if (result != Luau::Require::NavigationContext::NavigateResult::Success)
+        return result;
+
+    return Luau::Require::NavigationContext::NavigateResult::Success;
+}
+
+Luau::Require::NavigationContext::NavigateResult FileNavigationContext::toParent()
+{
+    return storePathResult(getParent(path, path));
+}
+
+Luau::Require::NavigationContext::NavigateResult FileNavigationContext::toChild(const std::string& component)
+{
+    return storePathResult(getChild(path, path, component));
+}
+
+bool FileNavigationContext::isModulePresent() const
+{
+    return isFilePresent(path, suffix);
+}
+
+std::optional<std::string> FileNavigationContext::getIdentifier() const
+{
+    return path + suffix;
+}
+
+bool FileNavigationContext::isConfigPresent() const
+{
+    return isFilePresent(path, "/.luaurc");
+}
+
+std::optional<std::string> FileNavigationContext::getConfig() const
+{
+    return getFileContents(path, "/.luaurc");
+}

CLI/src/Flags.cpp

@@ -31,7 +31,7 @@ static void setLuauFlags(bool state)
 void setLuauFlagsDefault()
 {
     for (Luau::FValue<bool>* flag = Luau::FValue<bool>::list; flag; flag = flag->next)
-        if (strncmp(flag->name, "Luau", 4) == 0 && !Luau::isFlagExperimental(flag->name))
+        if (strncmp(flag->name, "Luau", 4) == 0 && !Luau::isAnalysisFlagExperimental(flag->name))
             flag->value = true;
 }
 

CLI/src/Repl.cpp

@@ -14,6 +14,7 @@
 #include "Luau/FileUtils.h"
 #include "Luau/Flags.h"
 #include "Luau/Profiler.h"
+#include "Luau/ReplRequirer.h"
 #include "Luau/Require.h"
 
 #include "isocline.h"
@@ -113,172 +114,6 @@ static int lua_loadstring(lua_State* L)
     return 2;          // return nil plus error message
 }
 
-static int finishrequire(lua_State* L)
-{
-    if (lua_isstring(L, -1))
-        lua_error(L);
-
-    return 1;
-}
-
-struct RuntimeRequireContext : public RequireResolver::RequireContext
-{
-    // In the context of the REPL, source is the calling context's chunkname.
-    //
-    // These chunknames have certain prefixes that indicate context. These
-    // are used when displaying debug information (see luaO_chunkid).
-    //
-    // Generally, the '@' prefix is used for filepaths, and the '=' prefix is
-    // used for custom chunknames, such as =stdin.
-    explicit RuntimeRequireContext(std::string source)
-        : source(std::move(source))
-    {
-    }
-
-    std::string getPath() override
-    {
-        return source.substr(1);
-    }
-
-    bool isRequireAllowed() override
-    {
-        return isStdin() || (!source.empty() && source[0] == '@');
-    }
-
-    bool isStdin() override
-    {
-        return source == "=stdin";
-    }
-
-    std::string createNewIdentifer(const std::string& path) override
-    {
-        return "@" + path;
-    }
-
-private:
-    std::string source;
-};
-
-struct RuntimeCacheManager : public RequireResolver::CacheManager
-{
-    explicit RuntimeCacheManager(lua_State* L)
-        : L(L)
-    {
-    }
-
-    bool isCached(const std::string& path) override
-    {
-        luaL_findtable(L, LUA_REGISTRYINDEX, "_MODULES", 1);
-        lua_getfield(L, -1, path.c_str());
-        bool cached = !lua_isnil(L, -1);
-        lua_pop(L, 2);
-
-        if (cached)
-            cacheKey = path;
-
-        return cached;
-    }
-
-    std::string cacheKey;
-
-private:
-    lua_State* L;
-};
-
-struct RuntimeErrorHandler : RequireResolver::ErrorHandler
-{
-    explicit RuntimeErrorHandler(lua_State* L)
-        : L(L)
-    {
-    }
-
-    void reportError(const std::string message) override
-    {
-        luaL_errorL(L, "%s", message.c_str());
-    }
-
-private:
-    lua_State* L;
-};
-
-static int lua_require(lua_State* L)
-{
-    std::string name = luaL_checkstring(L, 1);
-
-    RequireResolver::ResolvedRequire resolvedRequire;
-    {
-        lua_Debug ar;
-        lua_getinfo(L, 1, "s", &ar);
-
-        RuntimeRequireContext requireContext{ar.source};
-        RuntimeCacheManager cacheManager{L};
-        RuntimeErrorHandler errorHandler{L};
-
-        RequireResolver resolver(std::move(name), requireContext, cacheManager, errorHandler);
-
-        resolvedRequire = resolver.resolveRequire(
-            [L, &cacheKey = cacheManager.cacheKey](const RequireResolver::ModuleStatus status)
-            {
-                lua_getfield(L, LUA_REGISTRYINDEX, "_MODULES");
-                if (status == RequireResolver::ModuleStatus::Cached)
-                    lua_getfield(L, -1, cacheKey.c_str());
-            }
-        );
-    }
-
-    if (resolvedRequire.status == RequireResolver::ModuleStatus::Cached)
-        return finishrequire(L);
-
-    // module needs to run in a new thread, isolated from the rest
-    // note: we create ML on main thread so that it doesn't inherit environment of L
-    lua_State* GL = lua_mainthread(L);
-    lua_State* ML = lua_newthread(GL);
-    lua_xmove(GL, L, 1);
-
-    // new thread needs to have the globals sandboxed
-    luaL_sandboxthread(ML);
-
-    // now we can compile & run module on the new thread
-    std::string bytecode = Luau::compile(resolvedRequire.sourceCode, copts());
-    if (luau_load(ML, resolvedRequire.identifier.c_str(), bytecode.data(), bytecode.size(), 0) == 0)
-    {
-        if (codegen)
-        {
-            Luau::CodeGen::CompilationOptions nativeOptions;
-            Luau::CodeGen::compile(ML, -1, nativeOptions);
-        }
-
-        if (coverageActive())
-            coverageTrack(ML, -1);
-
-        int status = lua_resume(ML, L, 0);
-
-        if (status == 0)
-        {
-            if (lua_gettop(ML) == 0)
-                lua_pushstring(ML, "module must return a value");
-            else if (!lua_istable(ML, -1) && !lua_isfunction(ML, -1))
-                lua_pushstring(ML, "module must return a table or function");
-        }
-        else if (status == LUA_YIELD)
-        {
-            lua_pushstring(ML, "module can not yield");
-        }
-        else if (!lua_isstring(ML, -1))
-        {
-            lua_pushstring(ML, "unknown error while running module");
-        }
-    }
-
-    // there's now a return value on top of ML; L stack: _MODULES ML
-    lua_xmove(ML, L, 1);
-    lua_pushvalue(L, -1);
-    lua_setfield(L, -4, resolvedRequire.absolutePath.c_str());
-
-    // L stack: _MODULES ML result
-    return finishrequire(L);
-}
-
 static int lua_collectgarbage(lua_State* L)
 {
     const char* option = luaL_optstring(L, 1, "collect");
@@ -329,6 +164,39 @@ static int lua_callgrind(lua_State* L)
 }
 #endif
 
+static void* createCliRequireContext(lua_State* L)
+{
+    void* ctx = lua_newuserdatadtor(
+        L,
+        sizeof(ReplRequirer),
+        [](void* ptr)
+        {
+            static_cast<ReplRequirer*>(ptr)->~ReplRequirer();
+        }
+    );
+
+    if (!ctx)
+        luaL_error(L, "unable to allocate ReplRequirer");
+
+    ctx = new (ctx) ReplRequirer{
+        copts,
+        coverageActive,
+        []()
+        {
+            return codegen;
+        },
+        coverageTrack,
+    };
+
+    // Store ReplRequirer in the registry to keep it alive for the lifetime of
+    // this lua_State. Memory address is used as a key to avoid collisions.
+    lua_pushlightuserdata(L, ctx);
+    lua_insert(L, -2);
+    lua_settable(L, LUA_REGISTRYINDEX);
+
+    return ctx;
+}
+
 void setupState(lua_State* L)
 {
     if (codegen)
@@ -338,7 +206,6 @@ void setupState(lua_State* L)
 
     static const luaL_Reg funcs[] = {
         {"loadstring", lua_loadstring},
-        {"require", lua_require},
         {"collectgarbage", lua_collectgarbage},
 #ifdef CALLGRIND
         {"callgrind", lua_callgrind},
@@ -350,6 +217,8 @@ void setupState(lua_State* L)
     luaL_register(L, NULL, funcs);
     lua_pop(L, 1);
 
+    luaopen_require(L, requireConfigInit, createCliRequireContext(L));
+
     luaL_sandbox(L);
 }
 
@@ -712,7 +581,14 @@ static bool runFile(const char* name, lua_State* GL, bool repl)
     // new thread needs to have the globals sandboxed
     luaL_sandboxthread(L);
 
-    std::string chunkname = "@" + std::string(name);
+    // ignore file extension when storing module's chunkname
+    std::string chunkname = "@";
+    std::string_view nameView = name;
+    if (size_t dotPos = nameView.find_last_of('.'); dotPos != std::string_view::npos)
+    {
+        nameView.remove_suffix(nameView.size() - dotPos);
+    }
+    chunkname += nameView;
 
     std::string bytecode = Luau::compile(*source, copts());
     int status = 0;

CLI/src/ReplRequirer.cpp

@@ -0,0 +1,221 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/ReplRequirer.h"
+
+#include "Luau/CodeGen.h"
+#include "Luau/CodeGenOptions.h"
+#include "Luau/Require.h"
+
+#include "Luau/RequirerUtils.h"
+#include "lua.h"
+#include "lualib.h"
+
+#include <string>
+#include <string_view>
+#include <utility>
+
+static luarequire_WriteResult write(std::optional<std::string> contents, char* buffer, size_t bufferSize, size_t* sizeOut)
+{
+    if (!contents)
+        return luarequire_WriteResult::WRITE_FAILURE;
+
+    size_t nullTerminatedSize = contents->size() + 1;
+
+    if (bufferSize < nullTerminatedSize)
+    {
+        *sizeOut = nullTerminatedSize;
+        return luarequire_WriteResult::WRITE_BUFFER_TOO_SMALL;
+    }
+
+    *sizeOut = nullTerminatedSize;
+    memcpy(buffer, contents->c_str(), nullTerminatedSize);
+    return luarequire_WriteResult::WRITE_SUCCESS;
+}
+
+static luarequire_NavigateResult storePathResult(ReplRequirer* req, PathResult result)
+{
+    if (result.status == PathResult::Status::AMBIGUOUS)
+        return NAVIGATE_AMBIGUOUS;
+
+    if (result.status == PathResult::Status::NOT_FOUND)
+        return NAVIGATE_NOT_FOUND;
+
+    req->absPath = result.absPath;
+    req->relPath = result.relPath;
+    req->suffix = result.suffix;
+
+    return NAVIGATE_SUCCESS;
+}
+
+static bool is_require_allowed(lua_State* L, void* ctx, const char* requirer_chunkname)
+{
+    std::string_view chunkname = requirer_chunkname;
+    return chunkname == "=stdin" || (!chunkname.empty() && chunkname[0] == '@');
+}
+
+static luarequire_NavigateResult reset(lua_State* L, void* ctx, const char* requirer_chunkname)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+
+    std::string chunkname = requirer_chunkname;
+    if (chunkname == "=stdin")
+    {
+        return storePathResult(req, getStdInResult());
+    }
+    else if (!chunkname.empty() && chunkname[0] == '@')
+    {
+        return storePathResult(req, tryGetRelativePathResult(chunkname.substr(1)));
+    }
+
+    return NAVIGATE_NOT_FOUND;
+}
+
+static luarequire_NavigateResult jump_to_alias(lua_State* L, void* ctx, const char* path)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+
+    luarequire_NavigateResult result = storePathResult(req, getAbsolutePathResult(path));
+    if (result != NAVIGATE_SUCCESS)
+        return result;
+
+    // Jumping to an absolute path breaks the relative-require chain. The best
+    // we can do is to store the absolute path itself.
+    req->relPath = req->absPath;
+    return NAVIGATE_SUCCESS;
+}
+
+static luarequire_NavigateResult to_parent(lua_State* L, void* ctx)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return storePathResult(req, getParent(req->absPath, req->relPath));
+}
+
+static luarequire_NavigateResult to_child(lua_State* L, void* ctx, const char* name)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return storePathResult(req, getChild(req->absPath, req->relPath, name));
+}
+
+static bool is_module_present(lua_State* L, void* ctx)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return isFilePresent(req->absPath, req->suffix);
+}
+
+static luarequire_WriteResult get_contents(lua_State* L, void* ctx, char* buffer, size_t buffer_size, size_t* size_out)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return write(getFileContents(req->absPath, req->suffix), buffer, buffer_size, size_out);
+}
+
+static luarequire_WriteResult get_chunkname(lua_State* L, void* ctx, char* buffer, size_t buffer_size, size_t* size_out)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return write("@" + req->relPath, buffer, buffer_size, size_out);
+}
+
+static luarequire_WriteResult get_cache_key(lua_State* L, void* ctx, char* buffer, size_t buffer_size, size_t* size_out)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return write(req->absPath + req->suffix, buffer, buffer_size, size_out);
+}
+
+static bool is_config_present(lua_State* L, void* ctx)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return isFilePresent(req->absPath, "/.luaurc");
+}
+
+static luarequire_WriteResult get_config(lua_State* L, void* ctx, char* buffer, size_t buffer_size, size_t* size_out)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+    return write(getFileContents(req->absPath, "/.luaurc"), buffer, buffer_size, size_out);
+}
+
+static int load(lua_State* L, void* ctx, const char* chunkname, const char* contents)
+{
+    ReplRequirer* req = static_cast<ReplRequirer*>(ctx);
+
+    // module needs to run in a new thread, isolated from the rest
+    // note: we create ML on main thread so that it doesn't inherit environment of L
+    lua_State* GL = lua_mainthread(L);
+    lua_State* ML = lua_newthread(GL);
+    lua_xmove(GL, L, 1);
+
+    // new thread needs to have the globals sandboxed
+    luaL_sandboxthread(ML);
+
+    // now we can compile & run module on the new thread
+    std::string bytecode = Luau::compile(contents, req->copts());
+    if (luau_load(ML, chunkname, bytecode.data(), bytecode.size(), 0) == 0)
+    {
+        if (req->codegenEnabled())
+        {
+            Luau::CodeGen::CompilationOptions nativeOptions;
+            Luau::CodeGen::compile(ML, -1, nativeOptions);
+        }
+
+        if (req->coverageActive())
+            req->coverageTrack(ML, -1);
+
+        int status = lua_resume(ML, L, 0);
+
+        if (status == 0)
+        {
+            if (lua_gettop(ML) == 0)
+                lua_pushstring(ML, "module must return a value");
+            else if (!lua_istable(ML, -1) && !lua_isfunction(ML, -1))
+                lua_pushstring(ML, "module must return a table or function");
+        }
+        else if (status == LUA_YIELD)
+        {
+            lua_pushstring(ML, "module can not yield");
+        }
+        else if (!lua_isstring(ML, -1))
+        {
+            lua_pushstring(ML, "unknown error while running module");
+        }
+    }
+
+    // add ML result to L stack
+    lua_xmove(ML, L, 1);
+    if (lua_isstring(L, -1))
+        lua_error(L);
+
+    // remove ML thread from L stack
+    lua_remove(L, -2);
+
+    // added one value to L stack: module result
+    return 1;
+}
+
+void requireConfigInit(luarequire_Configuration* config)
+{
+    if (config == nullptr)
+        return;
+
+    config->is_require_allowed = is_require_allowed;
+    config->reset = reset;
+    config->jump_to_alias = jump_to_alias;
+    config->to_parent = to_parent;
+    config->to_child = to_child;
+    config->is_module_present = is_module_present;
+    config->get_contents = get_contents;
+    config->is_config_present = is_config_present;
+    config->get_chunkname = get_chunkname;
+    config->get_cache_key = get_cache_key;
+    config->get_config = get_config;
+    config->load = load;
+}
+
+ReplRequirer::ReplRequirer(
+    std::function<Luau::CompileOptions()> copts,
+    std::function<bool()> coverageActive,
+    std::function<bool()> codegenEnabled,
+    std::function<void(lua_State*, int)> coverageTrack
+)
+    : copts(std::move(copts))
+    , coverageActive(std::move(coverageActive))
+    , codegenEnabled(std::move(codegenEnabled))
+    , coverageTrack(std::move(coverageTrack))
+{
+}

CLI/src/Require.cpp

@@ -1,313 +0,0 @@
-// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-#include "Luau/Require.h"
-
-#include "Luau/FileUtils.h"
-#include "Luau/Common.h"
-#include "Luau/Config.h"
-
-#include <algorithm>
-#include <array>
-#include <utility>
-
-static constexpr char kRequireErrorGeneric[] = "error requiring module";
-
-RequireResolver::RequireResolver(std::string path, RequireContext& requireContext, CacheManager& cacheManager, ErrorHandler& errorHandler)
-    : pathToResolve(std::move(path))
-    , requireContext(requireContext)
-    , cacheManager(cacheManager)
-    , errorHandler(errorHandler)
-{
-}
-
-RequireResolver::ResolvedRequire RequireResolver::resolveRequire(std::function<void(const ModuleStatus)> completionCallback)
-{
-    if (isRequireResolved)
-    {
-        errorHandler.reportError("require statement has already been resolved");
-        return ResolvedRequire{ModuleStatus::ErrorReported};
-    }
-
-    if (!initialize())
-        return ResolvedRequire{ModuleStatus::ErrorReported};
-
-    resolvedRequire.status = findModule();
-
-    if (completionCallback)
-        completionCallback(resolvedRequire.status);
-
-    isRequireResolved = true;
-    return resolvedRequire;
-}
-
-static bool hasValidPrefix(std::string_view path)
-{
-    return path.compare(0, 2, "./") == 0 || path.compare(0, 3, "../") == 0 || path.compare(0, 1, "@") == 0;
-}
-
-static bool isPathAmbiguous(const std::string& path)
-{
-    bool found = false;
-    for (const char* suffix : {".luau", ".lua"})
-    {
-        if (isFile(path + suffix))
-        {
-            if (found)
-                return true;
-            else
-                found = true;
-        }
-    }
-    if (isDirectory(path) && found)
-        return true;
-
-    return false;
-}
-
-bool RequireResolver::initialize()
-{
-    if (!requireContext.isRequireAllowed())
-    {
-        errorHandler.reportError("require is not supported in this context");
-        return false;
-    }
-
-    if (isAbsolutePath(pathToResolve))
-    {
-        errorHandler.reportError("cannot require an absolute path");
-        return false;
-    }
-
-    std::replace(pathToResolve.begin(), pathToResolve.end(), '\\', '/');
-
-    if (!hasValidPrefix(pathToResolve))
-    {
-        errorHandler.reportError("require path must start with a valid prefix: ./, ../, or @");
-        return false;
-    }
-
-    return substituteAliasIfPresent(pathToResolve);
-}
-
-RequireResolver::ModuleStatus RequireResolver::findModule()
-{
-    if (!resolveAndStoreDefaultPaths())
-        return ModuleStatus::ErrorReported;
-
-    if (isPathAmbiguous(resolvedRequire.absolutePath))
-    {
-        errorHandler.reportError("require path could not be resolved to a unique file");
-        return ModuleStatus::ErrorReported;
-    }
-
-    static constexpr std::array<const char*, 4> possibleSuffixes = {".luau", ".lua", "/init.luau", "/init.lua"};
-    size_t unsuffixedAbsolutePathSize = resolvedRequire.absolutePath.size();
-
-    for (const char* possibleSuffix : possibleSuffixes)
-    {
-        resolvedRequire.absolutePath += possibleSuffix;
-
-        if (cacheManager.isCached(resolvedRequire.absolutePath))
-            return ModuleStatus::Cached;
-
-        // Try to read the matching file
-        if (std::optional<std::string> source = readFile(resolvedRequire.absolutePath))
-        {
-            resolvedRequire.identifier = requireContext.createNewIdentifer(resolvedRequire.identifier + possibleSuffix);
-            resolvedRequire.sourceCode = *source;
-            return ModuleStatus::FileRead;
-        }
-
-        resolvedRequire.absolutePath.resize(unsuffixedAbsolutePathSize); // truncate to remove suffix
-    }
-
-    if (hasFileExtension(resolvedRequire.absolutePath, {".luau", ".lua"}) && isFile(resolvedRequire.absolutePath))
-    {
-        errorHandler.reportError("error requiring module: consider removing the file extension");
-        return ModuleStatus::ErrorReported;
-    }
-
-    errorHandler.reportError(kRequireErrorGeneric);
-    return ModuleStatus::ErrorReported;
-}
-
-bool RequireResolver::resolveAndStoreDefaultPaths()
-{
-    if (!isAbsolutePath(pathToResolve))
-    {
-        std::string identifierContext = getRequiringContextRelative();
-        std::optional<std::string> absolutePathContext = getRequiringContextAbsolute();
-
-        if (!absolutePathContext)
-            return false;
-
-        // resolvePath automatically sanitizes/normalizes the paths
-        std::optional<std::string> identifier = resolvePath(pathToResolve, identifierContext);
-        std::optional<std::string> absolutePath = resolvePath(pathToResolve, *absolutePathContext);
-
-        if (!identifier || !absolutePath)
-        {
-            errorHandler.reportError("could not resolve require path");
-            return false;
-        }
-
-        resolvedRequire.identifier = std::move(*identifier);
-        resolvedRequire.absolutePath = std::move(*absolutePath);
-    }
-    else
-    {
-        // Here we must explicitly sanitize, as the path is taken as is
-        std::string sanitizedPath = normalizePath(pathToResolve);
-        resolvedRequire.identifier = sanitizedPath;
-        resolvedRequire.absolutePath = std::move(sanitizedPath);
-    }
-    return true;
-}
-
-std::optional<std::string> RequireResolver::getRequiringContextAbsolute()
-{
-    std::string requiringFile;
-    if (isAbsolutePath(requireContext.getPath()))
-    {
-        // We already have an absolute path for the requiring file
-        requiringFile = requireContext.getPath();
-    }
-    else
-    {
-        // Requiring file's stored path is relative to the CWD, must make absolute
-        std::optional<std::string> cwd = getCurrentWorkingDirectory();
-        if (!cwd)
-        {
-            errorHandler.reportError("could not determine current working directory");
-            return std::nullopt;
-        }
-
-        if (requireContext.isStdin())
-        {
-            // Require statement is being executed from REPL input prompt
-            // The requiring context is the pseudo-file "stdin" in the CWD
-            requiringFile = joinPaths(*cwd, "stdin");
-        }
-        else
-        {
-            // Require statement is being executed in a file, must resolve relative to CWD
-            requiringFile = normalizePath(joinPaths(*cwd, requireContext.getPath()));
-        }
-    }
-    std::replace(requiringFile.begin(), requiringFile.end(), '\\', '/');
-    return requiringFile;
-}
-
-std::string RequireResolver::getRequiringContextRelative()
-{
-    return requireContext.isStdin() ? "./" : requireContext.getPath();
-}
-
-bool RequireResolver::substituteAliasIfPresent(std::string& path)
-{
-    if (path.size() < 1 || path[0] != '@')
-        return true;
-
-    // To ignore the '@' alias prefix when processing the alias
-    const size_t aliasStartPos = 1;
-
-    // If a directory separator was found, the length of the alias is the
-    // distance between the start of the alias and the separator. Otherwise,
-    // the whole string after the alias symbol is the alias.
-    size_t aliasLen = path.find_first_of("\\/");
-    if (aliasLen != std::string::npos)
-        aliasLen -= aliasStartPos;
-
-    const std::string potentialAlias = path.substr(aliasStartPos, aliasLen);
-
-    // Not worth searching when potentialAlias cannot be an alias
-    if (!Luau::isValidAlias(potentialAlias))
-    {
-        errorHandler.reportError("@" + potentialAlias + " is not a valid alias");
-        return false;
-    }
-
-    if (std::optional<std::string> alias = getAlias(potentialAlias))
-    {
-        path = *alias + path.substr(potentialAlias.size() + 1);
-        return true;
-    }
-
-    errorHandler.reportError("@" + potentialAlias + " is not a valid alias");
-    return false;
-}
-
-std::optional<std::string> RequireResolver::getAlias(std::string alias)
-{
-    std::transform(
-        alias.begin(),
-        alias.end(),
-        alias.begin(),
-        [](unsigned char c)
-        {
-            return ('A' <= c && c <= 'Z') ? (c + ('a' - 'A')) : c;
-        }
-    );
-    while (!config.aliases.contains(alias) && !isConfigFullyResolved)
-    {
-        if (!parseNextConfig())
-            return std::nullopt; // error parsing config
-    }
-    if (!config.aliases.contains(alias) && isConfigFullyResolved)
-        return std::nullopt; // could not find alias
-
-    const Luau::Config::AliasInfo& aliasInfo = config.aliases[alias];
-    return resolvePath(aliasInfo.value, aliasInfo.configLocation);
-}
-
-bool RequireResolver::parseNextConfig()
-{
-    if (isConfigFullyResolved)
-        return true; // no config files left to parse
-
-    std::optional<std::string> directory;
-    if (lastSearchedDir.empty())
-    {
-        std::optional<std::string> requiringFile = getRequiringContextAbsolute();
-        if (!requiringFile)
-            return false;
-
-        directory = getParentPath(*requiringFile);
-    }
-    else
-        directory = getParentPath(lastSearchedDir);
-
-    if (directory)
-    {
-        lastSearchedDir = *directory;
-        if (!parseConfigInDirectory(*directory))
-            return false;
-    }
-    else
-        isConfigFullyResolved = true;
-
-    return true;
-}
-
-bool RequireResolver::parseConfigInDirectory(const std::string& directory)
-{
-    std::string configPath = joinPaths(directory, Luau::kConfigName);
-
-    Luau::ConfigOptions::AliasOptions aliasOpts;
-    aliasOpts.configLocation = configPath;
-    aliasOpts.overwriteAliases = false;
-
-    Luau::ConfigOptions opts;
-    opts.aliasOptions = std::move(aliasOpts);
-
-    if (std::optional<std::string> contents = readFile(configPath))
-    {
-        std::optional<std::string> error = Luau::parseConfig(*contents, config, opts);
-        if (error)
-        {
-            errorHandler.reportError("error parsing " + configPath + "(" + *error + ")");
-            return false;
-        }
-    }
-
-    return true;
-}

CLI/src/RequirerUtils.cpp

@@ -0,0 +1,119 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/RequirerUtils.h"
+
+#include "Luau/FileUtils.h"
+
+#include <algorithm>
+#include <string>
+#include <string_view>
+
+static std::pair<PathResult::Status, std::string> getSuffixWithAmbiguityCheck(const std::string& path)
+{
+    bool found = false;
+    std::string suffix;
+
+    for (const char* potentialSuffix : {".luau", ".lua"})
+    {
+        if (isFile(path + potentialSuffix))
+        {
+            if (found)
+                return {PathResult::Status::AMBIGUOUS, ""};
+
+            suffix = potentialSuffix;
+            found = true;
+        }
+    }
+    if (isDirectory(path))
+    {
+        if (found)
+            return {PathResult::Status::AMBIGUOUS, ""};
+
+        for (const char* potentialSuffix : {"/init.luau", "/init.lua"})
+        {
+            if (isFile(path + potentialSuffix))
+            {
+                if (found)
+                    return {PathResult::Status::AMBIGUOUS, ""};
+
+                suffix = potentialSuffix;
+                found = true;
+            }
+        }
+
+        found = true;
+    }
+
+    if (!found)
+        return {PathResult::Status::NOT_FOUND, ""};
+
+    return {PathResult::Status::SUCCESS, suffix};
+}
+
+static PathResult addSuffix(PathResult partialResult)
+{
+    if (partialResult.status != PathResult::Status::SUCCESS)
+        return partialResult;
+
+    auto [status, suffix] = getSuffixWithAmbiguityCheck(partialResult.absPath);
+    if (status != PathResult::Status::SUCCESS)
+        return PathResult{status};
+
+    partialResult.suffix = std::move(suffix);
+    return partialResult;
+}
+
+PathResult getStdInResult()
+{
+    std::optional<std::string> cwd = getCurrentWorkingDirectory();
+    if (!cwd)
+        return PathResult{PathResult::Status::NOT_FOUND};
+
+    std::replace(cwd->begin(), cwd->end(), '\\', '/');
+
+    return PathResult{PathResult::Status::SUCCESS, *cwd + "/stdin", "./stdin", ""};
+}
+
+PathResult getAbsolutePathResult(const std::string& path)
+{
+    return addSuffix(PathResult{PathResult::Status::SUCCESS, path});
+}
+
+PathResult tryGetRelativePathResult(const std::string& path)
+{
+    if (isAbsolutePath(path))
+        return getAbsolutePathResult(path);
+
+    std::optional<std::string> cwd = getCurrentWorkingDirectory();
+    if (!cwd)
+        return PathResult{PathResult::Status::NOT_FOUND};
+
+    std::optional<std::string> resolvedAbsPath = resolvePath(path, *cwd + "/stdin");
+    if (!resolvedAbsPath)
+        return PathResult{PathResult::Status::NOT_FOUND};
+
+    return addSuffix(PathResult{PathResult::Status::SUCCESS, std::move(*resolvedAbsPath), path});
+}
+
+PathResult getParent(const std::string& absPath, const std::string& relPath)
+{
+    std::optional<std::string> parent = getParentPath(absPath);
+    if (!parent)
+        return PathResult{PathResult::Status::NOT_FOUND};
+
+    return addSuffix(PathResult{PathResult::Status::SUCCESS, *parent, normalizePath(relPath + "/..")});
+}
+
+PathResult getChild(const std::string& absPath, const std::string& relPath, const std::string& name)
+{
+    return addSuffix(PathResult{PathResult::Status::SUCCESS, joinPaths(absPath, name), joinPaths(relPath, name)});
+}
+
+bool isFilePresent(const std::string& path, const std::string& suffix)
+{
+    return isFile(path + suffix);
+}
+
+std::optional<std::string> getFileContents(const std::string& path, const std::string& suffix)
+{
+    return readFile(path + suffix);
+}

CMakeLists.txt

@@ -4,7 +4,7 @@ if(EXT_PLATFORM_STRING)
     return()
 endif()
 
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.10)
 
 option(LUAU_BUILD_CLI "Build CLI" ON)
 option(LUAU_BUILD_TESTS "Build tests" ON)
@@ -31,6 +31,8 @@ add_library(Luau.Analysis STATIC)
 add_library(Luau.EqSat STATIC)
 add_library(Luau.CodeGen STATIC)
 add_library(Luau.VM STATIC)
+add_library(Luau.Require STATIC)
+add_library(Luau.RequireNavigator STATIC)
 add_library(isocline STATIC)
 
 if(LUAU_BUILD_CLI)
@@ -101,6 +103,15 @@ target_compile_features(Luau.VM PRIVATE cxx_std_11)
 target_include_directories(Luau.VM PUBLIC VM/include)
 target_link_libraries(Luau.VM PUBLIC Luau.Common)
 
+target_compile_features(Luau.Require PUBLIC cxx_std_17)
+target_include_directories(Luau.Require PUBLIC Require/Runtime/include)
+target_link_libraries(Luau.Require PUBLIC Luau.VM)
+target_link_libraries(Luau.Require PRIVATE Luau.RequireNavigator)
+
+target_compile_features(Luau.RequireNavigator PUBLIC cxx_std_17)
+target_include_directories(Luau.RequireNavigator PUBLIC Require/Navigator/include)
+target_link_libraries(Luau.RequireNavigator PUBLIC Luau.Config)
+
 target_include_directories(isocline PUBLIC extern/isocline/include)
 
 target_include_directories(Luau.VM.Internals INTERFACE VM/src)
@@ -215,12 +226,12 @@ if(LUAU_BUILD_CLI)
 
     target_include_directories(Luau.Repl.CLI PRIVATE extern extern/isocline/include)
 
-    target_link_libraries(Luau.Repl.CLI PRIVATE Luau.Compiler Luau.Config Luau.CodeGen Luau.VM Luau.CLI.lib isocline)
+    target_link_libraries(Luau.Repl.CLI PRIVATE Luau.Compiler Luau.Config Luau.CodeGen Luau.VM Luau.Require Luau.CLI.lib isocline)
 
     target_link_libraries(Luau.Repl.CLI PRIVATE osthreads)
     target_link_libraries(Luau.Analyze.CLI PRIVATE osthreads)
 
-    target_link_libraries(Luau.Analyze.CLI PRIVATE Luau.Analysis Luau.CLI.lib)
+    target_link_libraries(Luau.Analyze.CLI PRIVATE Luau.Analysis Luau.CLI.lib Luau.RequireNavigator)
 
     target_link_libraries(Luau.Ast.CLI PRIVATE Luau.Ast Luau.Analysis Luau.CLI.lib)
 
@@ -252,7 +263,7 @@ if(LUAU_BUILD_TESTS)
 
     target_compile_options(Luau.CLI.Test PRIVATE ${LUAU_OPTIONS})
     target_include_directories(Luau.CLI.Test PRIVATE extern CLI)
-    target_link_libraries(Luau.CLI.Test PRIVATE Luau.Compiler Luau.Config Luau.CodeGen Luau.VM Luau.CLI.lib isocline)
+    target_link_libraries(Luau.CLI.Test PRIVATE Luau.Compiler Luau.Config Luau.CodeGen Luau.VM Luau.Require Luau.CLI.lib isocline)
     target_link_libraries(Luau.CLI.Test PRIVATE osthreads)
 
 endif()