Merge branch 'master' into type_function_solver_dependency_fix2

.github/workflows/benchmark.yml

@@ -63,10 +63,10 @@ jobs:
           }
           valgrind --tool=callgrind ./luau-analyze --mode=nonstrict bench/other/LuauPolyfillMap.lua 2>&1 | filter map-nonstrict | tee -a analyze-output.txt
           valgrind --tool=callgrind ./luau-analyze --mode=strict bench/other/LuauPolyfillMap.lua 2>&1 | filter map-strict | tee -a analyze-output.txt
-          valgrind --tool=callgrind ./luau-analyze --mode=strict --fflags=DebugLuauDeferredConstraintResolution bench/other/LuauPolyfillMap.lua 2>&1 | filter map-dcr | tee -a analyze-output.txt
+          valgrind --tool=callgrind ./luau-analyze --mode=strict --fflags=LuauSolverV2 bench/other/LuauPolyfillMap.lua 2>&1 | filter map-dcr | tee -a analyze-output.txt
           valgrind --tool=callgrind ./luau-analyze --mode=nonstrict bench/other/regex.lua 2>&1 | filter regex-nonstrict | tee -a analyze-output.txt
           valgrind --tool=callgrind ./luau-analyze --mode=strict bench/other/regex.lua 2>&1 | filter regex-strict | tee -a analyze-output.txt
-          valgrind --tool=callgrind ./luau-analyze --mode=strict --fflags=DebugLuauDeferredConstraintResolution bench/other/regex.lua 2>&1 | filter regex-dcr | tee -a analyze-output.txt
+          valgrind --tool=callgrind ./luau-analyze --mode=strict --fflags=LuauSolverV2 bench/other/regex.lua 2>&1 | filter regex-dcr | tee -a analyze-output.txt
 
       - name: Run benchmark (compile)
         run: |

.github/workflows/build.yml

@@ -46,9 +46,9 @@ jobs:
     - name: make cli
       run: |
          make -j2 config=sanitize werror=1 luau luau-analyze luau-compile # match config with tests to improve build time
-         ./luau tests/conformance/assert.lua
+         ./luau tests/conformance/assert.luau
-         ./luau-analyze tests/conformance/assert.lua
+         ./luau-analyze tests/conformance/assert.luau
-         ./luau-compile tests/conformance/assert.lua
+         ./luau-compile tests/conformance/assert.luau
 
   windows:
     runs-on: windows-latest
@@ -81,12 +81,12 @@ jobs:
       shell: bash # necessary for fail-fast
       run: |
         cmake --build . --target Luau.Repl.CLI Luau.Analyze.CLI Luau.Compile.CLI --config Debug # match config with tests to improve build time
-        Debug/luau tests/conformance/assert.lua
+        Debug/luau tests/conformance/assert.luau
-        Debug/luau-analyze tests/conformance/assert.lua
+        Debug/luau-analyze tests/conformance/assert.luau
-        Debug/luau-compile tests/conformance/assert.lua
+        Debug/luau-compile tests/conformance/assert.luau
 
   coverage:
-    runs-on: ubuntu-20.04 # needed for clang++-10 to avoid gcov compatibility issues
+    runs-on: ubuntu-22.04
     steps:
     - uses: actions/checkout@v2
     - name: install
@@ -94,7 +94,7 @@ jobs:
         sudo apt install llvm
     - name: make coverage
       run: |
-        CXX=clang++-10 make -j2 config=coverage native=1 coverage
+        CXX=clang++ make -j2 config=coverage native=1 coverage
     - name: upload coverage
       uses: codecov/codecov-action@v3
       with:

.github/workflows/new-release.yml

@@ -29,8 +29,8 @@ jobs:
   build:
     needs: ["create-release"]
     strategy:
-      matrix: # using ubuntu-20.04 to build a Linux binary targeting older glibc to improve compatibility
+      matrix: # not using ubuntu-latest to improve compatibility
-        os: [{name: ubuntu, version: ubuntu-20.04}, {name: macos, version: macos-latest}, {name: windows, version: windows-latest}]
+        os: [{name: ubuntu, version: ubuntu-22.04}, {name: macos, version: macos-latest}, {name: windows, version: windows-latest}]
     name: ${{matrix.os.name}}
     runs-on: ${{matrix.os.version}}
     steps:
@@ -38,7 +38,7 @@ jobs:
     - name: configure
       run: cmake . -DCMAKE_BUILD_TYPE=Release
     - name: build
-      run: cmake --build . --target Luau.Repl.CLI Luau.Analyze.CLI Luau.Compile.CLI --config Release -j 2
+      run: cmake --build . --target Luau.Repl.CLI Luau.Analyze.CLI Luau.Compile.CLI Luau.Ast.CLI --config Release -j 2
     - name: pack
       if: matrix.os.name != 'windows'
       run: zip luau-${{matrix.os.name}}.zip luau*

.github/workflows/release.yml

@@ -13,8 +13,8 @@ on:
 jobs:
   build:
     strategy:
-      matrix: # using ubuntu-20.04 to build a Linux binary targeting older glibc to improve compatibility
+      matrix: # not using ubuntu-latest to improve compatibility
-        os: [{name: ubuntu, version: ubuntu-20.04}, {name: macos, version: macos-latest}, {name: windows, version: windows-latest}]
+        os: [{name: ubuntu, version: ubuntu-22.04}, {name: macos, version: macos-latest}, {name: windows, version: windows-latest}]
     name: ${{matrix.os.name}}
     runs-on: ${{matrix.os.version}}
     steps:

.gitignore

@@ -13,6 +13,7 @@
 /luau
 /luau-tests
 /luau-analyze
+/luau-bytecode
 /luau-compile
 __pycache__
 .cache

Analysis/include/Luau/Autocomplete.h

@@ -1,10 +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/AutocompleteTypes.h"
 #include "Luau/Location.h"
 #include "Luau/Type.h"
 
-#include <unordered_map>
 #include <string>
 #include <memory>
 #include <optional>
@@ -16,89 +16,8 @@ struct Frontend;
 struct SourceModule;
 struct Module;
 struct TypeChecker;
-
+struct FileResolver;
-using ModulePtr = std::shared_ptr<Module>;
-
-enum class AutocompleteContext
-{
-    Unknown,
-    Expression,
-    Statement,
-    Property,
-    Type,
-    Keyword,
-    String,
-};
-
-enum class AutocompleteEntryKind
-{
-    Property,
-    Binding,
-    Keyword,
-    String,
-    Type,
-    Module,
-    GeneratedFunction,
-};
-
-enum class ParenthesesRecommendation
-{
-    None,
-    CursorAfter,
-    CursorInside,
-};
-
-enum class TypeCorrectKind
-{
-    None,
-    Correct,
-    CorrectFunctionResult,
-};
-
-struct AutocompleteEntry
-{
-    AutocompleteEntryKind kind = AutocompleteEntryKind::Property;
-    // Nullopt if kind is Keyword
-    std::optional<TypeId> type = std::nullopt;
-    bool deprecated = false;
-    // Only meaningful if kind is Property.
-    bool wrongIndexType = false;
-    // Set if this suggestion matches the type expected in the context
-    TypeCorrectKind typeCorrect = TypeCorrectKind::None;
-
-    std::optional<const ClassType*> containingClass = std::nullopt;
-    std::optional<const Property*> prop = std::nullopt;
-    std::optional<std::string> documentationSymbol = std::nullopt;
-    Tags tags;
-    ParenthesesRecommendation parens = ParenthesesRecommendation::None;
-    std::optional<std::string> insertText;
-
-    // Only meaningful if kind is Property.
-    bool indexedWithSelf = false;
-};
-
-using AutocompleteEntryMap = std::unordered_map<std::string, AutocompleteEntry>;
-struct AutocompleteResult
-{
-    AutocompleteEntryMap entryMap;
-    std::vector<AstNode*> ancestry;
-    AutocompleteContext context = AutocompleteContext::Unknown;
-
-    AutocompleteResult() = default;
-    AutocompleteResult(AutocompleteEntryMap entryMap, std::vector<AstNode*> ancestry, AutocompleteContext context)
-        : entryMap(std::move(entryMap))
-        , ancestry(std::move(ancestry))
-        , context(context)
-    {
-    }
-};
-
-using ModuleName = std::string;
-using StringCompletionCallback =
-    std::function<std::optional<AutocompleteEntryMap>(std::string tag, std::optional<const ClassType*> ctx, std::optional<std::string> contents)>;
 
 AutocompleteResult autocomplete(Frontend& frontend, const ModuleName& moduleName, Position position, StringCompletionCallback callback);
 
-constexpr char kGeneratedAnonymousFunctionEntryName[] = "function (anonymous autofilled)";
-
 } // namespace Luau

Analysis/include/Luau/AutocompleteTypes.h

@@ -0,0 +1,92 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Ast.h"
+#include "Luau/Type.h"
+
+#include <unordered_map>
+
+namespace Luau
+{
+
+enum class AutocompleteContext
+{
+    Unknown,
+    Expression,
+    Statement,
+    Property,
+    Type,
+    Keyword,
+    String,
+};
+
+enum class AutocompleteEntryKind
+{
+    Property,
+    Binding,
+    Keyword,
+    String,
+    Type,
+    Module,
+    GeneratedFunction,
+    RequirePath,
+};
+
+enum class ParenthesesRecommendation
+{
+    None,
+    CursorAfter,
+    CursorInside,
+};
+
+enum class TypeCorrectKind
+{
+    None,
+    Correct,
+    CorrectFunctionResult,
+};
+
+struct AutocompleteEntry
+{
+    AutocompleteEntryKind kind = AutocompleteEntryKind::Property;
+    // Nullopt if kind is Keyword
+    std::optional<TypeId> type = std::nullopt;
+    bool deprecated = false;
+    // Only meaningful if kind is Property.
+    bool wrongIndexType = false;
+    // Set if this suggestion matches the type expected in the context
+    TypeCorrectKind typeCorrect = TypeCorrectKind::None;
+
+    std::optional<const ClassType*> containingClass = std::nullopt;
+    std::optional<const Property*> prop = std::nullopt;
+    std::optional<std::string> documentationSymbol = std::nullopt;
+    Tags tags;
+    ParenthesesRecommendation parens = ParenthesesRecommendation::None;
+    std::optional<std::string> insertText;
+
+    // Only meaningful if kind is Property.
+    bool indexedWithSelf = false;
+};
+
+using AutocompleteEntryMap = std::unordered_map<std::string, AutocompleteEntry>;
+struct AutocompleteResult
+{
+    AutocompleteEntryMap entryMap;
+    std::vector<AstNode*> ancestry;
+    AutocompleteContext context = AutocompleteContext::Unknown;
+
+    AutocompleteResult() = default;
+    AutocompleteResult(AutocompleteEntryMap entryMap, std::vector<AstNode*> ancestry, AutocompleteContext context)
+        : entryMap(std::move(entryMap))
+        , ancestry(std::move(ancestry))
+        , context(context)
+    {
+    }
+};
+
+using StringCompletionCallback =
+    std::function<std::optional<AutocompleteEntryMap>(std::string tag, std::optional<const ClassType*> ctx, std::optional<std::string> contents)>;
+
+constexpr char kGeneratedAnonymousFunctionEntryName[] = "function (anonymous autofilled)";
+
+} // namespace Luau

Analysis/include/Luau/BuiltinDefinitions.h

@@ -9,6 +9,8 @@
 namespace Luau
 {
 
+static constexpr char kRequireTagName[] = "require";
+
 struct Frontend;
 struct GlobalTypes;
 struct TypeChecker;
@@ -63,10 +65,7 @@ TypeId makeFunction( // Polymorphic
     bool checked = false
 );
 
-void attachMagicFunction(TypeId ty, MagicFunction fn);
+void attachMagicFunction(TypeId ty, std::shared_ptr<MagicFunction> fn);
-void attachDcrMagicFunction(TypeId ty, DcrMagicFunction fn);
-void attachDcrMagicRefinement(TypeId ty, DcrMagicRefinement fn);
-void attachDcrMagicFunctionTypeCheck(TypeId ty, DcrMagicFunctionTypeCheck fn);
 Property makeProperty(TypeId ty, std::optional<std::string> documentationSymbol = std::nullopt);
 void assignPropDocumentationSymbols(TableType::Props& props, const std::string& baseName);
 
@@ -80,4 +79,16 @@ std::optional<Binding> tryGetGlobalBinding(GlobalTypes& globals, const std::stri
 Binding* tryGetGlobalBindingRef(GlobalTypes& globals, const std::string& name);
 TypeId getGlobalBinding(GlobalTypes& globals, const std::string& name);
 
+
+/** A number of built-in functions are magical enough that we need to match on them specifically by
+ * name when they are called. These are listed here to be used whenever necessary, instead of duplicating this logic repeatedly.
+ */
+
+bool matchSetMetatable(const AstExprCall& call);
+bool matchTableFreeze(const AstExprCall& call);
+bool matchAssert(const AstExprCall& call);
+
+// Returns `true` if the function should introduce typestate for its first argument.
+bool shouldTypestateForFirstArgument(const AstExprCall& call);
+
 } // namespace Luau

Analysis/include/Luau/Clone.h

@@ -4,6 +4,7 @@
 #include <Luau/NotNull.h>
 #include "Luau/TypeArena.h"
 #include "Luau/Type.h"
+#include "Luau/Scope.h"
 
 #include <unordered_map>
 
@@ -22,8 +23,21 @@ struct CloneState
     SeenTypePacks seenTypePacks;
 };
 
+/** `shallowClone` will make a copy of only the _top level_ constructor of the type,
+ * while `clone` will make a deep copy of the entire type and its every component.
+ *
+ * Be mindful about which behavior you actually _want_.
+ *
+ * Persistent types are not cloned as an optimization.
+ * If a type is cloned in order to mutate it, 'ignorePersistent' has to be set
+ */
+
+TypePackId shallowClone(TypePackId tp, TypeArena& dest, CloneState& cloneState, bool ignorePersistent = false);
+TypeId shallowClone(TypeId typeId, TypeArena& dest, CloneState& cloneState, bool ignorePersistent = false);
+
 TypePackId clone(TypePackId tp, TypeArena& dest, CloneState& cloneState);
 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);
 
 } // namespace Luau

Analysis/include/Luau/Constraint.h

@@ -109,6 +109,21 @@ struct FunctionCheckConstraint
     NotNull<DenseHashMap<const AstExpr*, TypeId>> astExpectedTypes;
 };
 
+// table_check expectedType exprType
+//
+// If `expectedType` is a table type and `exprType` is _also_ a table type,
+// propogate the member types of `expectedType` into the types of `exprType`.
+// This is used to implement bidirectional inference on table assignment.
+// Also see: FunctionCheckConstraint.
+struct TableCheckConstraint
+{
+    TypeId expectedType;
+    TypeId exprType;
+    AstExprTable* table = nullptr;
+    NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes;
+    NotNull<DenseHashMap<const AstExpr*, TypeId>> astExpectedTypes;
+};
+
 // prim FreeType ExpectedType PrimitiveType
 //
 // FreeType is bounded below by the singleton type and above by PrimitiveType
@@ -273,7 +288,8 @@ using ConstraintV = Variant<
     UnpackConstraint,
     ReduceConstraint,
     ReducePackConstraint,
-    EqualityConstraint>;
+    EqualityConstraint,
+    TableCheckConstraint>;
 
 struct Constraint
 {

Analysis/include/Luau/ConstraintGenerator.h

@@ -5,6 +5,7 @@
 #include "Luau/Constraint.h"
 #include "Luau/ControlFlow.h"
 #include "Luau/DataFlowGraph.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/InsertionOrderedMap.h"
 #include "Luau/Module.h"
 #include "Luau/ModuleResolver.h"
@@ -15,7 +16,6 @@
 #include "Luau/TypeFwd.h"
 #include "Luau/TypeUtils.h"
 #include "Luau/Variant.h"
-#include "Luau/Normalize.h"
 
 #include <memory>
 #include <vector>
@@ -28,6 +28,7 @@ struct Scope;
 using ScopePtr = std::shared_ptr<Scope>;
 
 struct DcrLogger;
+struct TypeFunctionRuntime;
 
 struct Inference
 {
@@ -95,6 +96,9 @@ struct ConstraintGenerator
     // will enqueue them during solving.
     std::vector<ConstraintPtr> unqueuedConstraints;
 
+    // Map a function's signature scope back to its signature type.
+    DenseHashMap<Scope*, TypeId> scopeToFunction{nullptr};
+
     // The private scope of type aliases for which the type parameters belong to.
     DenseHashMap<const AstStatTypeAlias*, ScopePtr> astTypeAliasDefiningScopes{nullptr};
 
@@ -108,6 +112,11 @@ struct ConstraintGenerator
 
     // Needed to be able to enable error-suppression preservation for immediate refinements.
     NotNull<Normalizer> normalizer;
+
+    NotNull<Simplifier> simplifier;
+
+    // Needed to register all available type functions for execution at later stages.
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     // Needed to resolve modules to make 'require' import types properly.
     NotNull<ModuleResolver> moduleResolver;
     // Occasionally constraint generation needs to produce an ICE.
@@ -125,6 +134,8 @@ struct ConstraintGenerator
     ConstraintGenerator(
         ModulePtr module,
         NotNull<Normalizer> normalizer,
+        NotNull<Simplifier> simplifier,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<ModuleResolver> moduleResolver,
         NotNull<BuiltinTypes> builtinTypes,
         NotNull<InternalErrorReporter> ice,
@@ -142,6 +153,8 @@ struct ConstraintGenerator
      */
     void visitModuleRoot(AstStatBlock* block);
 
+    void visitFragmentRoot(const ScopePtr& resumeScope, AstStatBlock* block);
+
 private:
     std::vector<std::vector<TypeId>> interiorTypes;
 
@@ -223,7 +236,10 @@ private:
     );
     void applyRefinements(const ScopePtr& scope, Location location, RefinementId refinement);
 
+    LUAU_NOINLINE void checkAliases(const ScopePtr& scope, AstStatBlock* block);
+
     ControlFlow visitBlockWithoutChildScope(const ScopePtr& scope, AstStatBlock* block);
+    ControlFlow visitBlockWithoutChildScope_DEPRECATED(const ScopePtr& scope, AstStatBlock* block);
 
     ControlFlow visit(const ScopePtr& scope, AstStat* stat);
     ControlFlow visit(const ScopePtr& scope, AstStatBlock* block);
@@ -282,11 +298,25 @@ private:
     Inference check(const ScopePtr& scope, AstExprFunction* func, std::optional<TypeId> expectedType, bool generalize);
     Inference check(const ScopePtr& scope, AstExprUnary* unary);
     Inference check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
+    Inference checkAstExprBinary(
+        const ScopePtr& scope,
+        const Location& location,
+        AstExprBinary::Op op,
+        AstExpr* left,
+        AstExpr* right,
+        std::optional<TypeId> expectedType
+    );
     Inference check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType);
     Inference check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert);
     Inference check(const ScopePtr& scope, AstExprInterpString* interpString);
     Inference check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
-    std::tuple<TypeId, TypeId, RefinementId> checkBinary(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
+    std::tuple<TypeId, TypeId, RefinementId> checkBinary(
+        const ScopePtr& scope,
+        AstExprBinary::Op op,
+        AstExpr* left,
+        AstExpr* right,
+        std::optional<TypeId> expectedType
+    );
 
     void visitLValue(const ScopePtr& scope, AstExpr* expr, TypeId rhsType);
     void visitLValue(const ScopePtr& scope, AstExprLocal* local, TypeId rhsType);
@@ -321,6 +351,11 @@ private:
      */
     void checkFunctionBody(const ScopePtr& scope, AstExprFunction* fn);
 
+    // Specializations of 'resolveType' below
+    TypeId resolveReferenceType(const ScopePtr& scope, AstType* ty, AstTypeReference* ref, bool inTypeArguments, bool replaceErrorWithFresh);
+    TypeId resolveTableType(const ScopePtr& scope, AstType* ty, AstTypeTable* tab, bool inTypeArguments, bool replaceErrorWithFresh);
+    TypeId resolveFunctionType(const ScopePtr& scope, AstType* ty, AstTypeFunction* fn, bool inTypeArguments, bool replaceErrorWithFresh);
+
     /**
      * Resolves a type from its AST annotation.
      * @param scope the scope that the type annotation appears within.
@@ -360,7 +395,7 @@ private:
      **/
     std::vector<std::pair<Name, GenericTypeDefinition>> createGenerics(
         const ScopePtr& scope,
-        AstArray<AstGenericType> generics,
+        AstArray<AstGenericType*> generics,
         bool useCache = false,
         bool addTypes = true
     );
@@ -377,7 +412,7 @@ private:
      **/
     std::vector<std::pair<Name, GenericTypePackDefinition>> createGenericPacks(
         const ScopePtr& scope,
-        AstArray<AstGenericTypePack> packs,
+        AstArray<AstGenericTypePack*> packs,
         bool useCache = false,
         bool addTypes = true
     );
@@ -391,6 +426,7 @@ private:
     TypeId makeUnion(const ScopePtr& scope, Location location, TypeId lhs, TypeId rhs);
     // make an intersect type function of these two types
     TypeId makeIntersect(const ScopePtr& scope, Location location, TypeId lhs, TypeId rhs);
+    void prepopulateGlobalScopeForFragmentTypecheck(const ScopePtr& globalScope, const ScopePtr& resumeScope, AstStatBlock* program);
 
     /** Scan the program for global definitions.
      *
@@ -421,6 +457,8 @@ private:
         const ScopePtr& scope,
         Location location
     );
+
+    TypeId simplifyUnion(const ScopePtr& scope, Location location, TypeId left, TypeId right);
 };
 
 /** Borrow a vector of pointers from a vector of owning pointers to constraints.

Analysis/include/Luau/ConstraintSolver.h

@@ -3,7 +3,9 @@
 #pragma once
 
 #include "Luau/Constraint.h"
+#include "Luau/DataFlowGraph.h"
 #include "Luau/DenseHash.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/Error.h"
 #include "Luau/Location.h"
 #include "Luau/Module.h"
@@ -12,6 +14,7 @@
 #include "Luau/ToString.h"
 #include "Luau/Type.h"
 #include "Luau/TypeCheckLimits.h"
+#include "Luau/TypeFunction.h"
 #include "Luau/TypeFwd.h"
 #include "Luau/Variant.h"
 
@@ -56,17 +59,42 @@ struct HashInstantiationSignature
     size_t operator()(const InstantiationSignature& signature) const;
 };
 
+
+struct TablePropLookupResult
+{
+    // What types are we blocked on for determining this type?
+    std::vector<TypeId> blockedTypes;
+    // The type of the property (if we were able to determine it).
+    std::optional<TypeId> propType;
+    // Whether or not this is _definitely_ derived as the result of an indexer.
+    // We use this to determine whether or not code like:
+    //
+    //   t.lol = nil;
+    //
+    // ... is legal. If `t: { [string]: ~nil }` then this is legal as
+    // there's no guarantee on whether "lol" specifically exists.
+    // However, if `t: { lol: ~nil }`, then we cannot allow assignment as
+    // that would remove "lol" from the table entirely.
+    bool isIndex = false;
+};
+
 struct ConstraintSolver
 {
     NotNull<TypeArena> arena;
     NotNull<BuiltinTypes> builtinTypes;
     InternalErrorReporter iceReporter;
     NotNull<Normalizer> normalizer;
+    NotNull<Simplifier> simplifier;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     // The entire set of constraints that the solver is trying to resolve.
     std::vector<NotNull<Constraint>> constraints;
+    NotNull<DenseHashMap<Scope*, TypeId>> scopeToFunction;
     NotNull<Scope> rootScope;
     ModuleName currentModuleName;
 
+    // The dataflow graph of the program, used in constraint generation and for magic functions.
+    NotNull<const DataFlowGraph> dfg;
+
     // Constraints that the solver has generated, rather than sourcing from the
     // scope tree.
     std::vector<std::unique_ptr<Constraint>> solverConstraints;
@@ -91,6 +119,9 @@ struct ConstraintSolver
     // A mapping from free types to the number of unresolved constraints that mention them.
     DenseHashMap<TypeId, size_t> unresolvedConstraints{{}};
 
+    std::unordered_map<NotNull<const Constraint>, DenseHashSet<TypeId>> maybeMutatedFreeTypes;
+    std::unordered_map<TypeId, DenseHashSet<const Constraint*>> mutatedFreeTypeToConstraint;
+
     // Irreducible/uninhabited type functions or type pack functions.
     DenseHashSet<const void*> uninhabitedTypeFunctions{{}};
 
@@ -114,12 +145,16 @@ struct ConstraintSolver
 
     explicit ConstraintSolver(
         NotNull<Normalizer> normalizer,
+        NotNull<Simplifier> simplifier,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<Scope> rootScope,
         std::vector<NotNull<Constraint>> constraints,
+        NotNull<DenseHashMap<Scope*, TypeId>> scopeToFunction,
         ModuleName moduleName,
         NotNull<ModuleResolver> moduleResolver,
         std::vector<RequireCycle> requireCycles,
         DcrLogger* logger,
+        NotNull<const DataFlowGraph> dfg,
         TypeCheckLimits limits
     );
 
@@ -139,9 +174,11 @@ struct ConstraintSolver
      **/
     void finalizeTypeFunctions();
 
-    bool isDone();
+    bool isDone() const;
 
 private:
+    void generalizeOneType(TypeId ty);
+
     /**
      * Bind a type variable to another type.
      *
@@ -167,13 +204,14 @@ public:
      */
     bool tryDispatch(NotNull<const Constraint> c, bool force);
 
-    bool tryDispatch(const SubtypeConstraint& c, NotNull<const Constraint> constraint, bool force);
+    bool tryDispatch(const SubtypeConstraint& c, NotNull<const Constraint> constraint);
-    bool tryDispatch(const PackSubtypeConstraint& c, NotNull<const Constraint> constraint, bool force);
+    bool tryDispatch(const PackSubtypeConstraint& c, NotNull<const Constraint> constraint);
-    bool tryDispatch(const GeneralizationConstraint& c, NotNull<const Constraint> constraint, bool force);
+    bool tryDispatch(const GeneralizationConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const IterableConstraint& c, NotNull<const Constraint> constraint, bool force);
     bool tryDispatch(const NameConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const TypeAliasExpansionConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const FunctionCallConstraint& c, NotNull<const Constraint> constraint);
+    bool tryDispatch(const TableCheckConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const FunctionCheckConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const PrimitiveTypeConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const HasPropConstraint& c, NotNull<const Constraint> constraint);
@@ -194,16 +232,16 @@ public:
     bool tryDispatch(const UnpackConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const ReduceConstraint& c, NotNull<const Constraint> constraint, bool force);
     bool tryDispatch(const ReducePackConstraint& c, NotNull<const Constraint> constraint, bool force);
-    bool tryDispatch(const EqualityConstraint& c, NotNull<const Constraint> constraint, bool force);
+    bool tryDispatch(const EqualityConstraint& c, NotNull<const Constraint> constraint);
 
     // for a, ... in some_table do
     // also handles __iter metamethod
     bool tryDispatchIterableTable(TypeId iteratorTy, const IterableConstraint& c, NotNull<const Constraint> constraint, bool force);
 
     // for a, ... in next_function, t, ... do
-    bool tryDispatchIterableFunction(TypeId nextTy, TypeId tableTy, const IterableConstraint& c, NotNull<const Constraint> constraint, bool force);
+    bool tryDispatchIterableFunction(TypeId nextTy, TypeId tableTy, const IterableConstraint& c, NotNull<const Constraint> constraint);
 
-    std::pair<std::vector<TypeId>, std::optional<TypeId>> lookupTableProp(
+    TablePropLookupResult lookupTableProp(
         NotNull<const Constraint> constraint,
         TypeId subjectType,
         const std::string& propName,
@@ -211,7 +249,8 @@ public:
         bool inConditional = false,
         bool suppressSimplification = false
     );
-    std::pair<std::vector<TypeId>, std::optional<TypeId>> lookupTableProp(
+
+    TablePropLookupResult lookupTableProp(
         NotNull<const Constraint> constraint,
         TypeId subjectType,
         const std::string& propName,
@@ -270,10 +309,10 @@ public:
     // FIXME: This use of a boolean for the return result is an appalling
     // interface.
     bool blockOnPendingTypes(TypeId target, NotNull<const Constraint> constraint);
-    bool blockOnPendingTypes(TypePackId target, NotNull<const Constraint> constraint);
+    bool blockOnPendingTypes(TypePackId targetPack, NotNull<const Constraint> constraint);
 
     void unblock(NotNull<const Constraint> progressed);
-    void unblock(TypeId progressed, Location location);
+    void unblock(TypeId ty, Location location);
     void unblock(TypePackId progressed, Location location);
     void unblock(const std::vector<TypeId>& types, Location location);
     void unblock(const std::vector<TypePackId>& packs, Location location);
@@ -281,18 +320,18 @@ public:
     /**
      * @returns true if the TypeId is in a blocked state.
      */
-    bool isBlocked(TypeId ty);
+    bool isBlocked(TypeId ty) const;
 
     /**
      * @returns true if the TypePackId is in a blocked state.
      */
-    bool isBlocked(TypePackId tp);
+    bool isBlocked(TypePackId tp) const;
 
     /**
      * Returns whether the constraint is blocked on anything.
      * @param constraint the constraint to check.
      */
-    bool isBlocked(NotNull<const Constraint> constraint);
+    bool isBlocked(NotNull<const Constraint> constraint) const;
 
     /** Pushes a new solver constraint to the solver.
      * @param cv the body of the constraint.
@@ -308,7 +347,7 @@ public:
      * @param location the location where the require is taking place; used for
      * error locations.
      **/
-    TypeId resolveModule(const ModuleInfo& module, const Location& location);
+    TypeId resolveModule(const ModuleInfo& info, const Location& location);
 
     void reportError(TypeErrorData&& data, const Location& location);
     void reportError(TypeError e);
@@ -379,15 +418,21 @@ public:
      **/
     void reproduceConstraints(NotNull<Scope> scope, const Location& location, const Substitution& subst);
 
+    TypeId simplifyIntersection(NotNull<Scope> scope, Location location, TypeId left, TypeId right);
+    TypeId simplifyIntersection(NotNull<Scope> scope, Location location, std::set<TypeId> parts);
+    TypeId simplifyUnion(NotNull<Scope> scope, Location location, TypeId left, TypeId right);
+
     TypeId errorRecoveryType() const;
     TypePackId errorRecoveryTypePack() const;
 
     TypePackId anyifyModuleReturnTypePackGenerics(TypePackId tp);
 
-    void throwTimeLimitError();
+    void throwTimeLimitError() const;
-    void throwUserCancelError();
+    void throwUserCancelError() const;
 
     ToStringOptions opts;
+
+    void fillInDiscriminantTypes(NotNull<const Constraint> constraint, const std::vector<std::optional<TypeId>>& discriminantTypes);
 };
 
 void dump(NotNull<Scope> rootScope, struct ToStringOptions& opts);

Analysis/include/Luau/DataFlowGraph.h

@@ -6,6 +6,7 @@
 #include "Luau/ControlFlow.h"
 #include "Luau/DenseHash.h"
 #include "Luau/Def.h"
+#include "Luau/NotNull.h"
 #include "Luau/Symbol.h"
 #include "Luau/TypedAllocator.h"
 
@@ -35,6 +36,8 @@ struct DataFlowGraph
     DataFlowGraph& operator=(DataFlowGraph&&) = default;
 
     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;
 
@@ -46,13 +49,13 @@ struct DataFlowGraph
     const RefinementKey* getRefinementKey(const AstExpr* expr) const;
 
 private:
-    DataFlowGraph() = default;
+    DataFlowGraph(NotNull<DefArena> defArena, NotNull<RefinementKeyArena> keyArena);
 
     DataFlowGraph(const DataFlowGraph&) = delete;
     DataFlowGraph& operator=(const DataFlowGraph&) = delete;
 
-    DefArena defArena;
+    NotNull<DefArena> defArena;
-    RefinementKeyArena keyArena;
+    NotNull<RefinementKeyArena> keyArena;
 
     DenseHashMap<const AstExpr*, const Def*> astDefs{nullptr};
 
@@ -68,7 +71,6 @@ private:
     DenseHashMap<const AstExpr*, const Def*> compoundAssignDefs{nullptr};
 
     DenseHashMap<const AstExpr*, const RefinementKey*> astRefinementKeys{nullptr};
-
     friend struct DataFlowGraphBuilder;
 };
 
@@ -105,25 +107,37 @@ struct DataFlowResult
     const RefinementKey* parent = nullptr;
 };
 
+using ScopeStack = std::vector<DfgScope*>;
+
 struct DataFlowGraphBuilder
 {
-    static DataFlowGraph build(AstStatBlock* root, NotNull<struct InternalErrorReporter> handle);
+    static DataFlowGraph build(
+        AstStatBlock* block,
+        NotNull<DefArena> defArena,
+        NotNull<RefinementKeyArena> keyArena,
+        NotNull<struct InternalErrorReporter> handle
+    );
 
 private:
-    DataFlowGraphBuilder() = default;
+    DataFlowGraphBuilder(NotNull<DefArena> defArena, NotNull<RefinementKeyArena> keyArena);
 
     DataFlowGraphBuilder(const DataFlowGraphBuilder&) = delete;
     DataFlowGraphBuilder& operator=(const DataFlowGraphBuilder&) = delete;
 
     DataFlowGraph graph;
-    NotNull<DefArena> defArena{&graph.defArena};
+    NotNull<DefArena> defArena;
-    NotNull<RefinementKeyArena> keyArena{&graph.keyArena};
+    NotNull<RefinementKeyArena> keyArena;
 
     struct InternalErrorReporter* handle = nullptr;
-    DfgScope* moduleScope = nullptr;
 
+    /// The arena owning all of the scope allocations for the dataflow graph being built.
     std::vector<std::unique_ptr<DfgScope>> scopes;
 
+    /// A stack of scopes used by the visitor to see where we are.
+    ScopeStack scopeStack;
+
+    DfgScope* currentScope();
+
     struct FunctionCapture
     {
         std::vector<DefId> captureDefs;
@@ -134,81 +148,81 @@ private:
     DenseHashMap<Symbol, FunctionCapture> captures{Symbol{}};
     void resolveCaptures();
 
-    DfgScope* childScope(DfgScope* scope, DfgScope::ScopeType scopeType = DfgScope::Linear);
+    DfgScope* makeChildScope(DfgScope::ScopeType scopeType = DfgScope::Linear);
 
     void join(DfgScope* p, DfgScope* a, DfgScope* b);
     void joinBindings(DfgScope* p, const DfgScope& a, const DfgScope& b);
     void joinProps(DfgScope* p, const DfgScope& a, const DfgScope& b);
 
-    DefId lookup(DfgScope* scope, Symbol symbol);
+    DefId lookup(Symbol symbol);
-    DefId lookup(DfgScope* scope, DefId def, const std::string& key);
+    DefId lookup(DefId def, const std::string& key);
 
-    ControlFlow visit(DfgScope* scope, AstStatBlock* b);
+    ControlFlow visit(AstStatBlock* b);
-    ControlFlow visitBlockWithoutChildScope(DfgScope* scope, AstStatBlock* b);
+    ControlFlow visitBlockWithoutChildScope(AstStatBlock* b);
 
-    ControlFlow visit(DfgScope* scope, AstStat* s);
+    ControlFlow visit(AstStat* s);
-    ControlFlow visit(DfgScope* scope, AstStatIf* i);
+    ControlFlow visit(AstStatIf* i);
-    ControlFlow visit(DfgScope* scope, AstStatWhile* w);
+    ControlFlow visit(AstStatWhile* w);
-    ControlFlow visit(DfgScope* scope, AstStatRepeat* r);
+    ControlFlow visit(AstStatRepeat* r);
-    ControlFlow visit(DfgScope* scope, AstStatBreak* b);
+    ControlFlow visit(AstStatBreak* b);
-    ControlFlow visit(DfgScope* scope, AstStatContinue* c);
+    ControlFlow visit(AstStatContinue* c);
-    ControlFlow visit(DfgScope* scope, AstStatReturn* r);
+    ControlFlow visit(AstStatReturn* r);
-    ControlFlow visit(DfgScope* scope, AstStatExpr* e);
+    ControlFlow visit(AstStatExpr* e);
-    ControlFlow visit(DfgScope* scope, AstStatLocal* l);
+    ControlFlow visit(AstStatLocal* l);
-    ControlFlow visit(DfgScope* scope, AstStatFor* f);
+    ControlFlow visit(AstStatFor* f);
-    ControlFlow visit(DfgScope* scope, AstStatForIn* f);
+    ControlFlow visit(AstStatForIn* f);
-    ControlFlow visit(DfgScope* scope, AstStatAssign* a);
+    ControlFlow visit(AstStatAssign* a);
-    ControlFlow visit(DfgScope* scope, AstStatCompoundAssign* c);
+    ControlFlow visit(AstStatCompoundAssign* c);
-    ControlFlow visit(DfgScope* scope, AstStatFunction* f);
+    ControlFlow visit(AstStatFunction* f);
-    ControlFlow visit(DfgScope* scope, AstStatLocalFunction* l);
+    ControlFlow visit(AstStatLocalFunction* l);
-    ControlFlow visit(DfgScope* scope, AstStatTypeAlias* t);
+    ControlFlow visit(AstStatTypeAlias* t);
-    ControlFlow visit(DfgScope* scope, AstStatTypeFunction* f);
+    ControlFlow visit(AstStatTypeFunction* f);
-    ControlFlow visit(DfgScope* scope, AstStatDeclareGlobal* d);
+    ControlFlow visit(AstStatDeclareGlobal* d);
-    ControlFlow visit(DfgScope* scope, AstStatDeclareFunction* d);
+    ControlFlow visit(AstStatDeclareFunction* d);
-    ControlFlow visit(DfgScope* scope, AstStatDeclareClass* d);
+    ControlFlow visit(AstStatDeclareClass* d);
-    ControlFlow visit(DfgScope* scope, AstStatError* error);
+    ControlFlow visit(AstStatError* error);
 
-    DataFlowResult visitExpr(DfgScope* scope, AstExpr* e);
+    DataFlowResult visitExpr(AstExpr* e);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprGroup* group);
+    DataFlowResult visitExpr(AstExprGroup* group);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprLocal* l);
+    DataFlowResult visitExpr(AstExprLocal* l);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprGlobal* g);
+    DataFlowResult visitExpr(AstExprGlobal* g);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprCall* c);
+    DataFlowResult visitExpr(AstExprCall* c);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprIndexName* i);
+    DataFlowResult visitExpr(AstExprIndexName* i);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprIndexExpr* i);
+    DataFlowResult visitExpr(AstExprIndexExpr* i);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprFunction* f);
+    DataFlowResult visitExpr(AstExprFunction* f);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprTable* t);
+    DataFlowResult visitExpr(AstExprTable* t);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprUnary* u);
+    DataFlowResult visitExpr(AstExprUnary* u);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprBinary* b);
+    DataFlowResult visitExpr(AstExprBinary* b);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprTypeAssertion* t);
+    DataFlowResult visitExpr(AstExprTypeAssertion* t);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprIfElse* i);
+    DataFlowResult visitExpr(AstExprIfElse* i);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprInterpString* i);
+    DataFlowResult visitExpr(AstExprInterpString* i);
-    DataFlowResult visitExpr(DfgScope* scope, AstExprError* error);
+    DataFlowResult visitExpr(AstExprError* error);
 
-    void visitLValue(DfgScope* scope, AstExpr* e, DefId incomingDef);
+    void visitLValue(AstExpr* e, DefId incomingDef);
-    DefId visitLValue(DfgScope* scope, AstExprLocal* l, DefId incomingDef);
+    DefId visitLValue(AstExprLocal* l, DefId incomingDef);
-    DefId visitLValue(DfgScope* scope, AstExprGlobal* g, DefId incomingDef);
+    DefId visitLValue(AstExprGlobal* g, DefId incomingDef);
-    DefId visitLValue(DfgScope* scope, AstExprIndexName* i, DefId incomingDef);
+    DefId visitLValue(AstExprIndexName* i, DefId incomingDef);
-    DefId visitLValue(DfgScope* scope, AstExprIndexExpr* i, DefId incomingDef);
+    DefId visitLValue(AstExprIndexExpr* i, DefId incomingDef);
-    DefId visitLValue(DfgScope* scope, AstExprError* e, DefId incomingDef);
+    DefId visitLValue(AstExprError* e, DefId incomingDef);
 
-    void visitType(DfgScope* scope, AstType* t);
+    void visitType(AstType* t);
-    void visitType(DfgScope* scope, AstTypeReference* r);
+    void visitType(AstTypeReference* r);
-    void visitType(DfgScope* scope, AstTypeTable* t);
+    void visitType(AstTypeTable* t);
-    void visitType(DfgScope* scope, AstTypeFunction* f);
+    void visitType(AstTypeFunction* f);
-    void visitType(DfgScope* scope, AstTypeTypeof* t);
+    void visitType(AstTypeTypeof* t);
-    void visitType(DfgScope* scope, AstTypeUnion* u);
+    void visitType(AstTypeUnion* u);
-    void visitType(DfgScope* scope, AstTypeIntersection* i);
+    void visitType(AstTypeIntersection* i);
-    void visitType(DfgScope* scope, AstTypeError* error);
+    void visitType(AstTypeError* error);
 
-    void visitTypePack(DfgScope* scope, AstTypePack* p);
+    void visitTypePack(AstTypePack* p);
-    void visitTypePack(DfgScope* scope, AstTypePackExplicit* e);
+    void visitTypePack(AstTypePackExplicit* e);
-    void visitTypePack(DfgScope* scope, AstTypePackVariadic* v);
+    void visitTypePack(AstTypePackVariadic* v);
-    void visitTypePack(DfgScope* scope, AstTypePackGeneric* g);
+    void visitTypePack(AstTypePackGeneric* g);
 
-    void visitTypeList(DfgScope* scope, AstTypeList l);
+    void visitTypeList(AstTypeList l);
 
-    void visitGenerics(DfgScope* scope, AstArray<AstGenericType> g);
+    void visitGenerics(AstArray<AstGenericType*> g);
-    void visitGenericPacks(DfgScope* scope, AstArray<AstGenericTypePack> g);
+    void visitGenericPacks(AstArray<AstGenericTypePack*> g);
 };
 
 } // namespace Luau

Analysis/include/Luau/EqSatSimplification.h

@@ -0,0 +1,50 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#pragma once
+
+#include "Luau/TypeFwd.h"
+#include "Luau/NotNull.h"
+#include "Luau/DenseHash.h"
+
+#include <memory>
+#include <optional>
+#include <vector>
+
+namespace Luau
+{
+struct TypeArena;
+}
+
+// The EqSat stuff is pretty template heavy, so we go to some lengths to prevent
+// the complexity from leaking outside its implementation sources.
+namespace Luau::EqSatSimplification
+{
+
+struct Simplifier;
+
+using SimplifierPtr = std::unique_ptr<Simplifier, void (*)(Simplifier*)>;
+
+SimplifierPtr newSimplifier(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes);
+
+} // namespace Luau::EqSatSimplification
+
+namespace Luau
+{
+
+struct EqSatSimplificationResult
+{
+    TypeId result;
+
+    // New type function applications that were created by the reduction phase.
+    // We return these so that the ConstraintSolver can know to try to reduce
+    // them.
+    std::vector<TypeId> newTypeFunctions;
+};
+
+using EqSatSimplification::newSimplifier;    // NOLINT: clang-tidy thinks these are unused.  It is incorrect.
+using Luau::EqSatSimplification::Simplifier; // NOLINT
+using Luau::EqSatSimplification::SimplifierPtr;
+
+std::optional<EqSatSimplificationResult> eqSatSimplify(NotNull<Simplifier> simplifier, TypeId ty);
+
+} // namespace Luau

Analysis/include/Luau/EqSatSimplificationImpl.h

@@ -0,0 +1,376 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#pragma once
+
+#include "Luau/EGraph.h"
+#include "Luau/Id.h"
+#include "Luau/Language.h"
+#include "Luau/Lexer.h" // For Allocator
+#include "Luau/NotNull.h"
+#include "Luau/TypeArena.h"
+#include "Luau/TypeFwd.h"
+
+namespace Luau
+{
+struct TypeFunction;
+}
+
+namespace Luau::EqSatSimplification
+{
+
+using StringId = uint32_t;
+using Id = Luau::EqSat::Id;
+
+LUAU_EQSAT_UNIT(TNil);
+LUAU_EQSAT_UNIT(TBoolean);
+LUAU_EQSAT_UNIT(TNumber);
+LUAU_EQSAT_UNIT(TString);
+LUAU_EQSAT_UNIT(TThread);
+LUAU_EQSAT_UNIT(TTopFunction);
+LUAU_EQSAT_UNIT(TTopTable);
+LUAU_EQSAT_UNIT(TTopClass);
+LUAU_EQSAT_UNIT(TBuffer);
+
+// Used for any type that eqsat can't do anything interesting with.
+LUAU_EQSAT_ATOM(TOpaque, TypeId);
+
+LUAU_EQSAT_ATOM(SBoolean, bool);
+LUAU_EQSAT_ATOM(SString, StringId);
+
+LUAU_EQSAT_ATOM(TFunction, TypeId);
+
+LUAU_EQSAT_ATOM(TImportedTable, TypeId);
+
+LUAU_EQSAT_ATOM(TClass, TypeId);
+
+LUAU_EQSAT_UNIT(TAny);
+LUAU_EQSAT_UNIT(TError);
+LUAU_EQSAT_UNIT(TUnknown);
+LUAU_EQSAT_UNIT(TNever);
+
+LUAU_EQSAT_NODE_SET(Union);
+LUAU_EQSAT_NODE_SET(Intersection);
+
+LUAU_EQSAT_NODE_ARRAY(Negation, 1);
+
+LUAU_EQSAT_NODE_ATOM_WITH_VECTOR(TTypeFun, std::shared_ptr<const TypeFunctionInstanceType>);
+
+LUAU_EQSAT_UNIT(TNoRefine);
+LUAU_EQSAT_UNIT(Invalid);
+
+// enodes are immutable, but types are cyclic.  We need a way to tie the knot.
+// We handle this by generating TBound nodes at points where we encounter cycles.
+// Each TBound has an ordinal that we later map onto the type.
+// We use a substitution rule to replace all TBound nodes with their referrent.
+LUAU_EQSAT_ATOM(TBound, size_t);
+
+// Tables are sufficiently unlike other enodes that the Language.h macros won't cut it.
+struct TTable
+{
+    explicit TTable(Id basis);
+    TTable(Id basis, std::vector<StringId> propNames_, std::vector<Id> propTypes_);
+
+    // All TTables extend some other table.  This may be TTopTable.
+    //
+    // It will frequently be a TImportedTable, in which case we can reuse things
+    // like source location and documentation info.
+    Id getBasis() const;
+    EqSat::Slice<const Id> propTypes() const;
+    // TODO: Also support read-only table props
+    // TODO: Indexer type, index result type.
+
+    std::vector<StringId> propNames;
+
+    // The enode interface
+    EqSat::Slice<Id> mutableOperands();
+    EqSat::Slice<const Id> operands() const;
+    bool operator==(const TTable& rhs) const;
+    bool operator!=(const TTable& rhs) const
+    {
+        return !(*this == rhs);
+    }
+
+    struct Hash
+    {
+        size_t operator()(const TTable& value) const;
+    };
+
+private:
+    // The first element of this vector is the basis.  Subsequent elements are
+    // property types. As we add other things like read-only properties and
+    // indexers, the structure of this array is likely to change.
+    //
+    // We encode our data in this way so that the operands() method can properly
+    // return a Slice<Id>.
+    std::vector<Id> storage;
+};
+
+template<typename L>
+using Node = EqSat::Node<L>;
+
+using EType = EqSat::Language<
+    TNil,
+    TBoolean,
+    TNumber,
+    TString,
+    TThread,
+    TTopFunction,
+    TTopTable,
+    TTopClass,
+    TBuffer,
+
+    TOpaque,
+
+    SBoolean,
+    SString,
+
+    TFunction,
+    TTable,
+    TImportedTable,
+    TClass,
+
+    TAny,
+    TError,
+    TUnknown,
+    TNever,
+
+    Union,
+    Intersection,
+
+    Negation,
+
+    TTypeFun,
+
+    Invalid,
+    TNoRefine,
+    TBound>;
+
+
+struct StringCache
+{
+    Allocator allocator;
+    DenseHashMap<std::string_view, StringId> strings{{}};
+    std::vector<std::string_view> views;
+
+    StringId add(std::string_view s);
+    std::string_view asStringView(StringId id) const;
+    std::string asString(StringId id) const;
+};
+
+using EGraph = Luau::EqSat::EGraph<EType, struct Simplify>;
+
+struct Simplify
+{
+    using Data = bool;
+
+    template<typename T>
+    Data make(const EGraph&, const T&) const;
+
+    void join(Data& left, const Data& right) const;
+};
+
+struct Subst
+{
+    Id eclass;
+    Id newClass;
+
+    // The node into eclass which is boring, if any
+    std::optional<size_t> boringIndex;
+
+    std::string desc;
+
+    Subst(Id eclass, Id newClass, std::string desc = "");
+};
+
+struct Simplifier
+{
+    NotNull<TypeArena> arena;
+    NotNull<BuiltinTypes> builtinTypes;
+    EGraph egraph;
+    StringCache stringCache;
+
+    // enodes are immutable but types can be cyclic, so we need some way to
+    // encode the cycle. This map is used to connect TBound nodes to the right
+    // eclass.
+    //
+    // The cyclicIntersection rewrite rule uses this to sense when a cycle can
+    // be deleted from an intersection or union.
+    std::unordered_map<size_t, Id> mappingIdToClass;
+
+    std::vector<Subst> substs;
+
+    using RewriteRuleFn = void (Simplifier::*)(Id id);
+
+    Simplifier(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes);
+
+    // Utilities
+    const EqSat::EClass<EType, Simplify::Data>& get(Id id) const;
+    Id find(Id id) const;
+    Id add(EType enode);
+
+    template<typename Tag>
+    const Tag* isTag(Id id) const;
+
+    template<typename Tag>
+    const Tag* isTag(const EType& enode) const;
+
+    void subst(Id from, Id to);
+    void subst(Id from, Id to, const std::string& ruleName);
+    void subst(Id from, Id to, const std::string& ruleName, const std::unordered_map<Id, size_t>& forceNodes);
+    void subst(Id from, size_t boringIndex, Id to, const std::string& ruleName, const std::unordered_map<Id, size_t>& forceNodes);
+
+    void unionClasses(std::vector<Id>& hereParts, Id there);
+
+    // Rewrite rules
+    void simplifyUnion(Id id);
+    void uninhabitedIntersection(Id id);
+    void intersectWithNegatedClass(Id id);
+    void intersectWithNegatedAtom(Id id);
+    void intersectWithNoRefine(Id id);
+    void cyclicIntersectionOfUnion(Id id);
+    void cyclicUnionOfIntersection(Id id);
+    void expandNegation(Id id);
+    void intersectionOfUnion(Id id);
+    void intersectTableProperty(Id id);
+    void uninhabitedTable(Id id);
+    void unneededTableModification(Id id);
+    void builtinTypeFunctions(Id id);
+    void iffyTypeFunctions(Id id);
+    void strictMetamethods(Id id);
+};
+
+template<typename Tag>
+struct QueryIterator
+{
+    QueryIterator();
+    QueryIterator(EGraph* egraph, Id eclass);
+
+    bool operator==(const QueryIterator& other) const;
+    bool operator!=(const QueryIterator& other) const;
+
+    std::pair<const Tag*, size_t> operator*() const;
+
+    QueryIterator& operator++();
+    QueryIterator& operator++(int);
+
+private:
+    EGraph* egraph = nullptr;
+    Id eclass;
+    size_t index = 0;
+};
+
+template<typename Tag>
+struct Query
+{
+    EGraph* egraph;
+    Id eclass;
+
+    Query(EGraph* egraph, Id eclass)
+        : egraph(egraph)
+        , eclass(eclass)
+    {
+    }
+
+    QueryIterator<Tag> begin()
+    {
+        return QueryIterator<Tag>{egraph, eclass};
+    }
+
+    QueryIterator<Tag> end()
+    {
+        return QueryIterator<Tag>{};
+    }
+};
+
+template<typename Tag>
+QueryIterator<Tag>::QueryIterator()
+    : egraph(nullptr)
+    , eclass(Id{0})
+    , index(0)
+{
+}
+
+template<typename Tag>
+QueryIterator<Tag>::QueryIterator(EGraph* egraph_, Id eclass)
+    : egraph(egraph_)
+    , eclass(eclass)
+    , index(0)
+{
+    const auto& ecl = (*egraph)[eclass];
+
+    static constexpr const int idx = EType::VariantTy::getTypeId<Tag>();
+
+    for (const auto& enode : ecl.nodes)
+    {
+        if (enode.node.index() < idx)
+            ++index;
+        else
+            break;
+    }
+
+    if (index >= ecl.nodes.size() || ecl.nodes[index].node.index() != idx)
+    {
+        egraph = nullptr;
+        index = 0;
+    }
+}
+
+template<typename Tag>
+bool QueryIterator<Tag>::operator==(const QueryIterator<Tag>& rhs) const
+{
+    if (egraph == nullptr && rhs.egraph == nullptr)
+        return true;
+
+    return egraph == rhs.egraph && eclass == rhs.eclass && index == rhs.index;
+}
+
+template<typename Tag>
+bool QueryIterator<Tag>::operator!=(const QueryIterator<Tag>& rhs) const
+{
+    return !(*this == rhs);
+}
+
+template<typename Tag>
+std::pair<const Tag*, size_t> QueryIterator<Tag>::operator*() const
+{
+    LUAU_ASSERT(egraph != nullptr);
+
+    EGraph::EClassT& ecl = (*egraph)[eclass];
+
+    LUAU_ASSERT(index < ecl.nodes.size());
+    auto& enode = ecl.nodes[index].node;
+    Tag* result = enode.template get<Tag>();
+    LUAU_ASSERT(result);
+    return {result, index};
+}
+
+// pre-increment
+template<typename Tag>
+QueryIterator<Tag>& QueryIterator<Tag>::operator++()
+{
+    const auto& ecl = (*egraph)[eclass];
+
+    do
+    {
+        ++index;
+        if (index >= ecl.nodes.size() || ecl.nodes[index].node.index() != EType::VariantTy::getTypeId<Tag>())
+        {
+            egraph = nullptr;
+            index = 0;
+            break;
+        }
+    } while (ecl.nodes[index].boring);
+
+    return *this;
+}
+
+// post-increment
+template<typename Tag>
+QueryIterator<Tag>& QueryIterator<Tag>::operator++(int)
+{
+    QueryIterator<Tag> res = *this;
+    ++res;
+    return res;
+}
+
+} // namespace Luau::EqSatSimplification

Analysis/include/Luau/Error.h

@@ -448,6 +448,13 @@ struct UnexpectedTypePackInSubtyping
     bool operator==(const UnexpectedTypePackInSubtyping& rhs) const;
 };
 
+struct UserDefinedTypeFunctionError
+{
+    std::string message;
+
+    bool operator==(const UserDefinedTypeFunctionError& rhs) const;
+};
+
 using TypeErrorData = Variant<
     TypeMismatch,
     UnknownSymbol,
@@ -496,7 +503,8 @@ using TypeErrorData = Variant<
     CheckedFunctionIncorrectArgs,
     UnexpectedTypeInSubtyping,
     UnexpectedTypePackInSubtyping,
-    ExplicitFunctionAnnotationRecommended>;
+    ExplicitFunctionAnnotationRecommended,
+    UserDefinedTypeFunctionError>;
 
 struct TypeErrorSummary
 {

Analysis/include/Luau/FileResolver.h

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <optional>
+#include <vector>
 
 namespace Luau
 {
@@ -31,6 +32,13 @@ struct ModuleInfo
     bool optional = false;
 };
 
+struct RequireSuggestion
+{
+    std::string label;
+    std::string fullPath;
+};
+using RequireSuggestions = std::vector<RequireSuggestion>;
+
 struct FileResolver
 {
     virtual ~FileResolver() {}
@@ -51,6 +59,11 @@ struct FileResolver
     {
         return std::nullopt;
     }
+
+    virtual std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const
+    {
+        return std::nullopt;
+    }
 };
 
 struct NullFileResolver : FileResolver

Analysis/include/Luau/FragmentAutocomplete.h

@@ -0,0 +1,146 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Ast.h"
+#include "Luau/Parser.h"
+#include "Luau/AutocompleteTypes.h"
+#include "Luau/DenseHash.h"
+#include "Luau/Module.h"
+#include "Luau/Frontend.h"
+
+#include <memory>
+#include <vector>
+
+namespace Luau
+{
+struct FrontendOptions;
+
+enum class FragmentTypeCheckStatus
+{
+    SkipAutocomplete,
+    Success,
+};
+
+struct FragmentAutocompleteAncestryResult
+{
+    DenseHashMap<AstName, AstLocal*> localMap{AstName()};
+    std::vector<AstLocal*> localStack;
+    std::vector<AstNode*> ancestry;
+    AstStat* nearestStatement = nullptr;
+};
+
+struct FragmentParseResult
+{
+    std::string fragmentToParse;
+    AstStatBlock* root = nullptr;
+    std::vector<AstNode*> ancestry;
+    AstStat* nearestStatement = nullptr;
+    std::vector<Comment> commentLocations;
+    std::unique_ptr<Allocator> alloc = std::make_unique<Allocator>();
+};
+
+struct FragmentTypeCheckResult
+{
+    ModulePtr incrementalModule = nullptr;
+    ScopePtr freshScope;
+    std::vector<AstNode*> ancestry;
+};
+
+struct FragmentAutocompleteResult
+{
+    ModulePtr incrementalModule;
+    Scope* freshScope;
+    TypeArena arenaForAutocomplete;
+    AutocompleteResult acResults;
+};
+
+FragmentAutocompleteAncestryResult findAncestryForFragmentParse(AstStatBlock* root, const Position& cursorPos);
+
+std::optional<FragmentParseResult> parseFragment(
+    const SourceModule& srcModule,
+    std::string_view src,
+    const Position& cursorPos,
+    std::optional<Position> fragmentEndPosition
+);
+
+std::pair<FragmentTypeCheckStatus, FragmentTypeCheckResult> typecheckFragment(
+    Frontend& frontend,
+    const ModuleName& moduleName,
+    const Position& cursorPos,
+    std::optional<FrontendOptions> opts,
+    std::string_view src,
+    std::optional<Position> fragmentEndPosition
+);
+
+FragmentAutocompleteResult fragmentAutocomplete(
+    Frontend& frontend,
+    std::string_view src,
+    const ModuleName& moduleName,
+    Position cursorPosition,
+    std::optional<FrontendOptions> opts,
+    StringCompletionCallback callback,
+    std::optional<Position> fragmentEndPosition = std::nullopt
+);
+
+enum class FragmentAutocompleteStatus
+{
+    Success,
+    FragmentTypeCheckFail,
+    InternalIce
+};
+
+struct FragmentAutocompleteStatusResult
+{
+    FragmentAutocompleteStatus status;
+    std::optional<FragmentAutocompleteResult> result;
+};
+
+struct FragmentContext
+{
+    std::string_view newSrc;
+    const ParseResult& newAstRoot;
+    std::optional<FrontendOptions> opts;
+    std::optional<Position> DEPRECATED_fragmentEndPosition;
+};
+
+/**
+ * @brief Attempts to compute autocomplete suggestions from the fragment context.
+ *
+ * This function computes autocomplete suggestions using outdated frontend typechecking data
+ * by patching the fragment context of the new script source content.
+ *
+ * @param frontend The Luau Frontend data structure, which may contain outdated typechecking data.
+ *
+ * @param moduleName The name of the target module, specifying which script the caller wants to request autocomplete for.
+ *
+ * @param cursorPosition The position in the script where the caller wants to trigger autocomplete.
+ *
+ * @param context The fragment context that this API will use to patch the outdated typechecking data.
+ *
+ * @param stringCompletionCB A callback function that provides autocomplete suggestions for string contexts.
+ *
+ * @return
+ * The status indicating whether `fragmentAutocomplete` ran successfully or failed, along with the reason for failure.
+ * Also includes autocomplete suggestions if the status is successful.
+ *
+ * @usage
+ * FragmentAutocompleteStatusResult acStatusResult;
+ * if (shouldFragmentAC)
+ *     acStatusResult = Luau::tryFragmentAutocomplete(...);
+ *
+ * if (acStatusResult.status != Successful)
+ * {
+ *     frontend.check(moduleName, options);
+ *     acStatusResult.acResult = Luau::autocomplete(...);
+ * }
+ * return convertResultWithContext(acStatusResult.acResult);
+ */
+FragmentAutocompleteStatusResult tryFragmentAutocomplete(
+    Frontend& frontend,
+    const ModuleName& moduleName,
+    Position cursorPosition,
+    FragmentContext context,
+    StringCompletionCallback stringCompletionCB
+);
+
+} // namespace Luau

Analysis/include/Luau/Frontend.h

@@ -7,6 +7,7 @@
 #include "Luau/ModuleResolver.h"
 #include "Luau/RequireTracer.h"
 #include "Luau/Scope.h"
+#include "Luau/Set.h"
 #include "Luau/TypeCheckLimits.h"
 #include "Luau/Variant.h"
 #include "Luau/AnyTypeSummary.h"
@@ -44,21 +45,6 @@ struct LoadDefinitionFileResult
 
 std::optional<Mode> parseMode(const std::vector<HotComment>& hotcomments);
 
-std::vector<std::string_view> parsePathExpr(const AstExpr& pathExpr);
-
-// Exported only for convenient testing.
-std::optional<ModuleName> pathExprToModuleName(const ModuleName& currentModuleName, const std::vector<std::string_view>& expr);
-
-/** Try to convert an AST fragment into a ModuleName.
- * Returns std::nullopt if the expression cannot be resolved.  This will most likely happen in cases where
- * the import path involves some dynamic computation that we cannot see into at typechecking time.
- *
- * Unintuitively, weirdly-formulated modules (like game.Parent.Parent.Parent.Foo) will successfully produce a ModuleName
- * as long as it falls within the permitted syntax.  This is ok because we will fail to find the module and produce an
- * error when we try during typechecking.
- */
-std::optional<ModuleName> pathExprToModuleName(const ModuleName& currentModuleName, const AstExpr& expr);
-
 struct SourceNode
 {
     bool hasDirtySourceModule() const
@@ -71,13 +57,32 @@ struct SourceNode
         return forAutocomplete ? dirtyModuleForAutocomplete : dirtyModule;
     }
 
+    bool hasInvalidModuleDependency(bool forAutocomplete) const
+    {
+        return forAutocomplete ? invalidModuleDependencyForAutocomplete : invalidModuleDependency;
+    }
+
+    void setInvalidModuleDependency(bool value, bool forAutocomplete)
+    {
+        if (forAutocomplete)
+            invalidModuleDependencyForAutocomplete = value;
+        else
+            invalidModuleDependency = value;
+    }
+
     ModuleName name;
     std::string humanReadableName;
     DenseHashSet<ModuleName> requireSet{{}};
     std::vector<std::pair<ModuleName, Location>> requireLocations;
+    Set<ModuleName> dependents{{}};
+
     bool dirtySourceModule = true;
     bool dirtyModule = true;
     bool dirtyModuleForAutocomplete = true;
+
+    bool invalidModuleDependency = true;
+    bool invalidModuleDependencyForAutocomplete = true;
+
     double autocompleteLimitsMult = 1.0;
 };
 
@@ -132,7 +137,7 @@ struct FrontendModuleResolver : ModuleResolver
     std::optional<ModuleInfo> resolveModuleInfo(const ModuleName& currentModuleName, const AstExpr& pathExpr) override;
     std::string getHumanReadableModuleName(const ModuleName& moduleName) const override;
 
-    void setModule(const ModuleName& moduleName, ModulePtr module);
+    bool setModule(const ModuleName& moduleName, ModulePtr module);
     void clearModules();
 
 private:
@@ -166,9 +171,13 @@ struct Frontend
     // Parse and typecheck module graph
     CheckResult check(const ModuleName& name, std::optional<FrontendOptions> optionOverride = {}); // new shininess
 
+    bool allModuleDependenciesValid(const ModuleName& name, bool forAutocomplete = false) const;
+
     bool isDirty(const ModuleName& name, bool forAutocomplete = false) const;
     void markDirty(const ModuleName& name, std::vector<ModuleName>* markedDirty = nullptr);
 
+    void traverseDependents(const ModuleName& name, std::function<bool(SourceNode&)> processSubtree);
+
     /** Borrow a pointer into the SourceModule cache.
      *
      * Returns nullptr if we don't have it.  This could mean that the script
@@ -209,6 +218,7 @@ struct Frontend
     );
 
     std::optional<CheckResult> getCheckResult(const ModuleName& name, bool accumulateNested, bool forAutocomplete = false);
+    std::vector<ModuleName> getRequiredScripts(const ModuleName& name);
 
 private:
     ModulePtr check(

Analysis/include/Luau/Instantiation.h

@@ -60,7 +60,7 @@ struct ReplaceGenerics : Substitution
 };
 
 // A substitution which replaces generic functions by monomorphic functions
-struct Instantiation : Substitution
+struct Instantiation final : Substitution
 {
     Instantiation(const TxnLog* log, TypeArena* arena, NotNull<BuiltinTypes> builtinTypes, TypeLevel level, Scope* scope)
         : Substitution(log, arena)

Analysis/include/Luau/Instantiation2.h

@@ -53,7 +53,7 @@ struct Replacer : Substitution
 };
 
 // A substitution which replaces generic functions by monomorphic functions
-struct Instantiation2 : Substitution
+struct Instantiation2 final : Substitution
 {
     // Mapping from generic types to free types to be used in instantiation.
     DenseHashMap<TypeId, TypeId> genericSubstitutions{nullptr};

Analysis/include/Luau/Module.h

@@ -9,15 +9,24 @@
 #include "Luau/Scope.h"
 #include "Luau/TypeArena.h"
 #include "Luau/AnyTypeSummary.h"
+#include "Luau/DataFlowGraph.h"
 
 #include <memory>
 #include <vector>
 #include <unordered_map>
 #include <optional>
 
+LUAU_FASTFLAG(LuauIncrementalAutocompleteCommentDetection)
+
 namespace Luau
 {
 
+using LogLuauProc = void (*)(std::string_view);
+extern LogLuauProc logLuau;
+
+void setLogLuau(LogLuauProc ll);
+void resetLogLuauProc();
+
 struct Module;
 struct AnyTypeSummary;
 
@@ -54,6 +63,7 @@ struct SourceModule
     }
 };
 
+bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos);
 bool isWithinComment(const SourceModule& sourceModule, Position pos);
 bool isWithinComment(const ParseResult& result, Position pos);
 
@@ -67,6 +77,9 @@ struct Module
 {
     ~Module();
 
+    // TODO: Clip this when we clip FFlagLuauSolverV2
+    bool checkedInNewSolver = false;
+
     ModuleName name;
     std::string humanReadableName;
 
@@ -132,6 +145,11 @@ struct Module
     TypePackId returnType = nullptr;
     std::unordered_map<Name, TypeFun> exportedTypeBindings;
 
+    // Arenas related to the DFG must persist after the DFG no longer exists, as
+    // Module objects maintain raw pointers to objects in these arenas.
+    DefArena defArena;
+    RefinementKeyArena keyArena;
+
     bool hasModuleScope() const;
     ScopePtr getModuleScope() const;
 

Analysis/include/Luau/ModuleResolver.h

@@ -20,8 +20,6 @@ struct ModuleResolver
     virtual ~ModuleResolver() {}
 
     /** Compute a ModuleName from an AST fragment.  This AST fragment is generally the argument to the require() function.
-     *
-     * You probably want to implement this with some variation of pathExprToModuleName.
      *
      * @returns The ModuleInfo if the expression is a syntactically legal path.
      * @returns std::nullopt if we are unable to determine whether or not the expression is a valid path.  Type inference will

Analysis/include/Luau/NonStrictTypeChecker.h

@@ -9,11 +9,14 @@ namespace Luau
 {
 
 struct BuiltinTypes;
+struct TypeFunctionRuntime;
 struct UnifierSharedState;
 struct TypeCheckLimits;
 
 void checkNonStrict(
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<InternalErrorReporter> ice,
     NotNull<UnifierSharedState> unifierState,
     NotNull<const DataFlowGraph> dfg,

Analysis/include/Luau/Normalize.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/EqSatSimplification.h"
 #include "Luau/NotNull.h"
 #include "Luau/Set.h"
 #include "Luau/TypeFwd.h"
@@ -21,10 +22,22 @@ struct Scope;
 
 using ModulePtr = std::shared_ptr<Module>;
 
-bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice);
+bool isSubtype(
-bool isSubtype(TypePackId subTy, TypePackId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice);
+    TypeId subTy,
-bool isConsistentSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice);
+    TypeId superTy,
-bool isConsistentSubtype(TypePackId subTy, TypePackId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice);
+    NotNull<Scope> scope,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    InternalErrorReporter& ice
+);
+bool isSubtype(
+    TypePackId subPack,
+    TypePackId superPack,
+    NotNull<Scope> scope,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    InternalErrorReporter& ice
+);
 
 class TypeIds
 {
@@ -336,6 +349,7 @@ struct NormalizedType
 };
 
 
+using SeenTablePropPairs = Set<std::pair<TypeId, TypeId>, TypeIdPairHash>;
 
 class Normalizer
 {
@@ -390,7 +404,13 @@ public:
     void unionTablesWithTable(TypeIds& heres, TypeId there);
     void unionTables(TypeIds& heres, const TypeIds& theres);
     NormalizationResult unionNormals(NormalizedType& here, const NormalizedType& there, int ignoreSmallerTyvars = -1);
-    NormalizationResult unionNormalWithTy(NormalizedType& here, TypeId there, Set<TypeId>& seenSetTypes, int ignoreSmallerTyvars = -1);
+    NormalizationResult unionNormalWithTy(
+        NormalizedType& here,
+        TypeId there,
+        SeenTablePropPairs& seenTablePropPairs,
+        Set<TypeId>& seenSetTypes,
+        int ignoreSmallerTyvars = -1
+    );
 
     // ------- Negations
     std::optional<NormalizedType> negateNormal(const NormalizedType& here);
@@ -407,16 +427,26 @@ public:
     void intersectClassesWithClass(NormalizedClassType& heres, TypeId there);
     void intersectStrings(NormalizedStringType& here, const NormalizedStringType& there);
     std::optional<TypePackId> intersectionOfTypePacks(TypePackId here, TypePackId there);
-    std::optional<TypeId> intersectionOfTables(TypeId here, TypeId there, Set<TypeId>& seenSet);
+    std::optional<TypeId> intersectionOfTables(TypeId here, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSet);
-    void intersectTablesWithTable(TypeIds& heres, TypeId there, Set<TypeId>& seenSetTypes);
+    void intersectTablesWithTable(TypeIds& heres, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSetTypes);
     void intersectTables(TypeIds& heres, const TypeIds& theres);
     std::optional<TypeId> intersectionOfFunctions(TypeId here, TypeId there);
     void intersectFunctionsWithFunction(NormalizedFunctionType& heress, TypeId there);
     void intersectFunctions(NormalizedFunctionType& heress, const NormalizedFunctionType& theress);
-    NormalizationResult intersectTyvarsWithTy(NormalizedTyvars& here, TypeId there, Set<TypeId>& seenSetTypes);
+    NormalizationResult intersectTyvarsWithTy(
+        NormalizedTyvars& here,
+        TypeId there,
+        SeenTablePropPairs& seenTablePropPairs,
+        Set<TypeId>& seenSetTypes
+    );
     NormalizationResult intersectNormals(NormalizedType& here, const NormalizedType& there, int ignoreSmallerTyvars = -1);
-    NormalizationResult intersectNormalWithTy(NormalizedType& here, TypeId there, Set<TypeId>& seenSetTypes);
+    NormalizationResult intersectNormalWithTy(NormalizedType& here, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSetTypes);
-    NormalizationResult normalizeIntersections(const std::vector<TypeId>& intersections, NormalizedType& outType, Set<TypeId>& seenSet);
+    NormalizationResult normalizeIntersections(
+        const std::vector<TypeId>& intersections,
+        NormalizedType& outType,
+        SeenTablePropPairs& seenTablePropPairs,
+        Set<TypeId>& seenSet
+    );
 
     // Check for inhabitance
     NormalizationResult isInhabited(TypeId ty);
@@ -426,7 +456,7 @@ public:
 
     // Check for intersections being inhabited
     NormalizationResult isIntersectionInhabited(TypeId left, TypeId right);
-    NormalizationResult isIntersectionInhabited(TypeId left, TypeId right, Set<TypeId>& seenSet);
+    NormalizationResult isIntersectionInhabited(TypeId left, TypeId right, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSet);
 
     // -------- Convert back from a normalized type to a type
     TypeId typeFromNormal(const NormalizedType& norm);

Analysis/include/Luau/OverloadResolution.h

@@ -2,12 +2,13 @@
 #pragma once
 
 #include "Luau/Ast.h"
-#include "Luau/InsertionOrderedMap.h"
+#include "Luau/EqSatSimplification.h"
-#include "Luau/NotNull.h"
-#include "Luau/TypeFwd.h"
-#include "Luau/Location.h"
 #include "Luau/Error.h"
+#include "Luau/InsertionOrderedMap.h"
+#include "Luau/Location.h"
+#include "Luau/NotNull.h"
 #include "Luau/Subtyping.h"
+#include "Luau/TypeFwd.h"
 
 namespace Luau
 {
@@ -34,7 +35,9 @@ struct OverloadResolver
     OverloadResolver(
         NotNull<BuiltinTypes> builtinTypes,
         NotNull<TypeArena> arena,
+        NotNull<Simplifier> simplifier,
         NotNull<Normalizer> normalizer,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<Scope> scope,
         NotNull<InternalErrorReporter> reporter,
         NotNull<TypeCheckLimits> limits,
@@ -43,7 +46,9 @@ struct OverloadResolver
 
     NotNull<BuiltinTypes> builtinTypes;
     NotNull<TypeArena> arena;
+    NotNull<Simplifier> simplifier;
     NotNull<Normalizer> normalizer;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     NotNull<Scope> scope;
     NotNull<InternalErrorReporter> ice;
     NotNull<TypeCheckLimits> limits;
@@ -108,7 +113,9 @@ struct SolveResult
 SolveResult solveFunctionCall(
     NotNull<TypeArena> arena,
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
     NotNull<Normalizer> normalizer,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<InternalErrorReporter> iceReporter,
     NotNull<TypeCheckLimits> limits,
     NotNull<Scope> scope,

Analysis/include/Luau/RequireTracer.h

@@ -11,14 +11,12 @@
 namespace Luau
 {
 
-class AstStat;
+class AstNode;
-class AstExpr;
 class AstStatBlock;
-struct AstLocal;
 
 struct RequireTraceResult
 {
-    DenseHashMap<const AstExpr*, ModuleInfo> exprs{nullptr};
+    DenseHashMap<const AstNode*, ModuleInfo> exprs{nullptr};
 
     std::vector<std::pair<ModuleName, Location>> requireList;
 };

Analysis/include/Luau/Scope.h

@@ -85,12 +85,18 @@ struct Scope
     void inheritAssignments(const ScopePtr& childScope);
     void inheritRefinements(const ScopePtr& childScope);
 
+    // Track globals that should emit warnings during type checking.
+    DenseHashSet<std::string> globalsToWarn{""};
+    bool shouldWarnGlobal(std::string name) const;
+
     // For mutually recursive type aliases, it's important that
     // they use the same types for the same names.
     // For instance, in `type Tree<T> { data: T, children: Forest<T> } type Forest<T> = {Tree<T>}`
     // we need that the generic type `T` in both cases is the same, so we use a cache.
     std::unordered_map<Name, TypeId> typeAliasTypeParameters;
     std::unordered_map<Name, TypePackId> typeAliasTypePackParameters;
+
+    std::optional<std::vector<TypeId>> interiorFreeTypes;
 };
 
 // Returns true iff the left scope encloses the right scope.  A Scope* equal to

Analysis/include/Luau/Simplify.h

@@ -19,10 +19,10 @@ struct SimplifyResult
     DenseHashSet<TypeId> blockedTypes;
 };
 
-SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId ty, TypeId discriminant);
+SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId left, TypeId right);
 SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, std::set<TypeId> parts);
 
-SimplifyResult simplifyUnion(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId ty, TypeId discriminant);
+SimplifyResult simplifyUnion(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId left, TypeId right);
 
 enum class Relation
 {

Analysis/include/Luau/Subtyping.h

@@ -1,13 +1,14 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/DenseHash.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/Set.h"
+#include "Luau/TypeCheckLimits.h"
+#include "Luau/TypeFunction.h"
 #include "Luau/TypeFwd.h"
 #include "Luau/TypePairHash.h"
 #include "Luau/TypePath.h"
-#include "Luau/TypeFunction.h"
-#include "Luau/TypeCheckLimits.h"
-#include "Luau/DenseHash.h"
 
 #include <vector>
 #include <optional>
@@ -96,6 +97,22 @@ struct SubtypingEnvironment
         DenseHashSet<TypeId> upperBound{nullptr};
     };
 
+    /* For nested subtyping relationship tests of mapped generic bounds, we keep the outer environment immutable */
+    SubtypingEnvironment* parent = nullptr;
+
+    /// Applies `mappedGenerics` to the given type.
+    /// This is used specifically to substitute for generics in type function instances.
+    std::optional<TypeId> applyMappedGenerics(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId ty);
+
+    const TypeId* tryFindSubstitution(TypeId ty) const;
+    const SubtypingResult* tryFindSubtypingResult(std::pair<TypeId, TypeId> subAndSuper) const;
+
+    bool containsMappedType(TypeId ty) const;
+    bool containsMappedPack(TypePackId tp) const;
+
+    GenericBounds& getMappedTypeBounds(TypeId ty);
+    TypePackId* getMappedPackBounds(TypePackId tp);
+
     /*
      * When we encounter a generic over the course of a subtyping test, we need
      * to tentatively map that generic onto a type on the other side.
@@ -112,17 +129,15 @@ struct SubtypingEnvironment
     DenseHashMap<TypeId, TypeId> substitutions{nullptr};
 
     DenseHashMap<std::pair<TypeId, TypeId>, SubtypingResult, TypePairHash> ephemeralCache{{}};
-
-    /// Applies `mappedGenerics` to the given type.
-    /// This is used specifically to substitute for generics in type function instances.
-    std::optional<TypeId> applyMappedGenerics(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId ty);
 };
 
 struct Subtyping
 {
     NotNull<BuiltinTypes> builtinTypes;
     NotNull<TypeArena> arena;
+    NotNull<Simplifier> simplifier;
     NotNull<Normalizer> normalizer;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     NotNull<InternalErrorReporter> iceReporter;
 
     TypeCheckLimits limits;
@@ -142,7 +157,9 @@ struct Subtyping
     Subtyping(
         NotNull<BuiltinTypes> builtinTypes,
         NotNull<TypeArena> typeArena,
+        NotNull<Simplifier> simplifier,
         NotNull<Normalizer> normalizer,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<InternalErrorReporter> iceReporter
     );
 

Analysis/include/Luau/TableLiteralInference.h

@@ -6,6 +6,8 @@
 #include "Luau/NotNull.h"
 #include "Luau/TypeFwd.h"
 
+#include <vector>
+
 namespace Luau
 {
 

Analysis/include/Luau/ToString.h

@@ -44,6 +44,7 @@ struct ToStringOptions
     bool hideTableKind = false;                   // If true, all tables will be surrounded with plain '{}'
     bool hideNamedFunctionTypeParameters = false; // If true, type parameters of functions will be hidden at top-level.
     bool hideFunctionSelfArgument = false;        // If true, `self: X` will be omitted from the function signature if the function has self
+    bool useQuestionMarks = true;                 // If true, use a postfix ? for options, else write them out as unions that include nil.
     size_t maxTableLength = size_t(FInt::LuauTableTypeMaximumStringifierLength); // Only applied to TableTypes
     size_t maxTypeLength = size_t(FInt::LuauTypeMaximumStringifierLength);
     size_t compositeTypesSingleLineLimit = 5; // The number of type elements permitted on a single line when printing type unions/intersections

Analysis/include/Luau/TxnLog.h

@@ -65,11 +65,10 @@ T* getMutable(PendingTypePack* pending)
 // Log of what TypeIds we are rebinding, to be committed later.
 struct TxnLog
 {
-    explicit TxnLog(bool useScopes = false)
+    explicit TxnLog()
         : typeVarChanges(nullptr)
         , typePackChanges(nullptr)
         , ownedSeen()
-        , useScopes(useScopes)
         , sharedSeen(&ownedSeen)
     {
     }

Analysis/include/Luau/Type.h

@@ -31,6 +31,7 @@ namespace Luau
 struct TypeArena;
 struct Scope;
 using ScopePtr = std::shared_ptr<Scope>;
+struct Module;
 
 struct TypeFunction;
 struct Constraint;
@@ -68,12 +69,16 @@ using Name = std::string;
 // A free type is one whose exact shape has yet to be fully determined.
 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, TypeLevel level, TypeId lowerBound, TypeId upperBound);
+    // Old constructors
     explicit FreeType(TypeLevel level);
     explicit FreeType(Scope* scope);
     FreeType(Scope* scope, TypeLevel level);
 
-    FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound);
-
     int index;
     TypeLevel level;
     Scope* scope = nullptr;
@@ -130,14 +135,14 @@ struct BlockedType
     BlockedType();
     int index;
 
-    Constraint* getOwner() const;
+    const Constraint* getOwner() const;
-    void setOwner(Constraint* newOwner);
+    void setOwner(const Constraint* newOwner);
-    void replaceOwner(Constraint* newOwner);
+    void replaceOwner(const Constraint* newOwner);
 
 private:
     // The constraint that is intended to unblock this type. Other constraints
     // should block on this constraint if present.
-    Constraint* owner = nullptr;
+    const Constraint* owner = nullptr;
 };
 
 struct PrimitiveType
@@ -278,9 +283,6 @@ struct WithPredicate
     }
 };
 
-using MagicFunction = std::function<std::optional<
-    WithPredicate<TypePackId>>(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>)>;
-
 struct MagicFunctionCallContext
 {
     NotNull<struct ConstraintSolver> solver;
@@ -290,7 +292,6 @@ struct MagicFunctionCallContext
     TypePackId result;
 };
 
-using DcrMagicFunction = std::function<bool(MagicFunctionCallContext)>;
 struct MagicRefinementContext
 {
     NotNull<Scope> scope;
@@ -307,8 +308,30 @@ struct MagicFunctionTypeCheckContext
     NotNull<Scope> checkScope;
 };
 
-using DcrMagicRefinement = void (*)(const MagicRefinementContext&);
+struct MagicFunction
-using DcrMagicFunctionTypeCheck = std::function<void(const MagicFunctionTypeCheckContext&)>;
+{
+    virtual std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) = 0;
+
+    // Callback to allow custom typechecking of builtin function calls whose argument types
+    // will only be resolved after constraint solving. For example, the arguments to string.format
+    // have types that can only be decided after parsing the format string and unifying
+    // with the passed in values, but the correctness of the call can only be decided after
+    // all the types have been finalized.
+    virtual bool infer(const MagicFunctionCallContext&) = 0;
+    virtual void refine(const MagicRefinementContext&) {}
+
+    // If a magic function needs to do its own special typechecking, do it here.
+    // Returns true if magic typechecking was performed.  Return false if the
+    // default typechecking logic should run.
+    virtual bool typeCheck(const MagicFunctionTypeCheckContext&)
+    {
+        return false;
+    }
+
+    virtual ~MagicFunction() {}
+};
+
 struct FunctionType
 {
     // Global monomorphic function
@@ -366,16 +389,7 @@ struct FunctionType
     Scope* scope = nullptr;
     TypePackId argTypes;
     TypePackId retTypes;
-    MagicFunction magicFunction = nullptr;
+    std::shared_ptr<MagicFunction> magic = nullptr;
-    DcrMagicFunction dcrMagicFunction = nullptr;
-    DcrMagicRefinement dcrMagicRefinement = nullptr;
-
-    // Callback to allow custom typechecking of builtin function calls whose argument types
-    // will only be resolved after constraint solving. For example, the arguments to string.format
-    // have types that can only be decided after parsing the format string and unifying
-    // with the passed in values, but the correctness of the call can only be decided after
-    // all the types have been finalized.
-    DcrMagicFunctionTypeCheck dcrMagicTypeCheck = nullptr;
 
     bool hasSelf;
     // `hasNoFreeOrGenericTypes` should be true if and only if the type does not have any free or generic types present inside it.
@@ -598,6 +612,19 @@ struct ClassType
     }
 };
 
+// Data required to initialize a user-defined function and its environment
+struct UserDefinedFunctionData
+{
+    // Store a weak module reference to ensure the lifetime requirements are preserved
+    std::weak_ptr<Module> owner;
+
+    // References to AST elements are owned by the Module allocator which also stores this type
+    AstStatTypeFunction* definition = nullptr;
+
+    DenseHashMap<Name, std::pair<AstStatTypeFunction*, size_t>> environment{""};
+    DenseHashMap<Name, AstStatTypeFunction*> environment_DEPRECATED{""};
+};
+
 /**
  * An instance of a type function that has not yet been reduced to a more concrete
  * type. The constraint solver receives a constraint to reduce each
@@ -613,20 +640,20 @@ struct TypeFunctionInstanceType
     std::vector<TypePackId> packArguments;
 
     std::optional<AstName> userFuncName; // Name of the user-defined type function; only available for UDTFs
-    std::optional<AstExprFunction*> userFuncBody; // Body of the user-defined type function; only available for UDTFs
+    UserDefinedFunctionData userFuncData;
 
     TypeFunctionInstanceType(
         NotNull<const TypeFunction> function,
         std::vector<TypeId> typeArguments,
         std::vector<TypePackId> packArguments,
-        std::optional<AstName> userFuncName = std::nullopt,
+        std::optional<AstName> userFuncName,
-        std::optional<AstExprFunction*> userFuncBody = std::nullopt
+        UserDefinedFunctionData userFuncData
     )
         : function(function)
         , typeArguments(typeArguments)
         , packArguments(packArguments)
         , userFuncName(userFuncName)
-        , userFuncBody(userFuncBody)
+        , userFuncData(userFuncData)
     {
     }
 
@@ -643,6 +670,13 @@ struct TypeFunctionInstanceType
         , packArguments(packArguments)
     {
     }
+
+    TypeFunctionInstanceType(NotNull<const TypeFunction> function, std::vector<TypeId> typeArguments, std::vector<TypePackId> packArguments)
+        : function{function}
+        , typeArguments(typeArguments)
+        , packArguments(packArguments)
+    {
+    }
 };
 
 /** Represents a pending type alias instantiation.
@@ -670,6 +704,11 @@ struct AnyType
 {
 };
 
+// A special, trivial type for the refinement system that is always eliminated from intersections.
+struct NoRefineType
+{
+};
+
 // `T | U`
 struct UnionType
 {
@@ -737,7 +776,7 @@ struct NegationType
     TypeId ty;
 };
 
-using ErrorType = Unifiable::Error;
+using ErrorType = Unifiable::Error<TypeId>;
 
 using TypeVariant = Unifiable::Variant<
     TypeId,
@@ -758,6 +797,7 @@ using TypeVariant = Unifiable::Variant<
     UnknownType,
     NeverType,
     NegationType,
+    NoRefineType,
     TypeFunctionInstanceType>;
 
 struct Type final
@@ -803,6 +843,13 @@ struct Type final
     Type& operator=(const TypeVariant& rhs);
     Type& operator=(TypeVariant&& rhs);
 
+    Type(Type&&) = default;
+    Type& operator=(Type&&) = default;
+
+    Type clone() const;
+
+private:
+    Type(const Type&) = default;
     Type& operator=(const Type& rhs);
 };
 
@@ -952,6 +999,7 @@ public:
     const TypeId unknownType;
     const TypeId neverType;
     const TypeId errorType;
+    const TypeId noRefineType;
     const TypeId falsyType;
     const TypeId truthyType;
 
@@ -1159,6 +1207,10 @@ TypeId freshType(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, S
 using TypeIdPredicate = std::function<std::optional<TypeId>(TypeId)>;
 std::vector<TypeId> filterMap(TypeId type, TypeIdPredicate predicate);
 
+// A tag to mark a type which doesn't derive directly from the root type as overriding the return of `typeof`.
+// Any classes which derive from this type will have typeof return this type.
+static constexpr char kTypeofRootTag[] = "typeofRoot";
+
 void attachTag(TypeId ty, const std::string& tagName);
 void attachTag(Property& prop, const std::string& tagName);
 

Analysis/include/Luau/TypeArena.h

@@ -32,9 +32,13 @@ struct TypeArena
 
     TypeId addTV(Type&& tv);
 
-    TypeId freshType(TypeLevel level);
+    TypeId freshType(NotNull<BuiltinTypes> builtins, TypeLevel level);
-    TypeId freshType(Scope* scope);
+    TypeId freshType(NotNull<BuiltinTypes> builtins, Scope* scope);
-    TypeId freshType(Scope* scope, TypeLevel level);
+    TypeId freshType(NotNull<BuiltinTypes> builtins, Scope* scope, TypeLevel level);
+
+    TypeId freshType_DEPRECATED(TypeLevel level);
+    TypeId freshType_DEPRECATED(Scope* scope);
+    TypeId freshType_DEPRECATED(Scope* scope, TypeLevel level);
 
     TypePackId freshTypePack(Scope* scope);
 

Analysis/include/Luau/TypeChecker2.h

@@ -2,15 +2,16 @@
 
 #pragma once
 
-#include "Luau/Error.h"
-#include "Luau/NotNull.h"
 #include "Luau/Common.h"
-#include "Luau/TypeUtils.h"
+#include "Luau/EqSatSimplification.h"
+#include "Luau/Error.h"
+#include "Luau/Normalize.h"
+#include "Luau/NotNull.h"
+#include "Luau/Subtyping.h"
 #include "Luau/Type.h"
 #include "Luau/TypeFwd.h"
 #include "Luau/TypeOrPack.h"
-#include "Luau/Normalize.h"
+#include "Luau/TypeUtils.h"
-#include "Luau/Subtyping.h"
 
 namespace Luau
 {
@@ -60,7 +61,9 @@ struct Reasonings
 
 void check(
     NotNull<BuiltinTypes> builtinTypes,
-    NotNull<UnifierSharedState> sharedState,
+    NotNull<Simplifier> simplifier,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
+    NotNull<UnifierSharedState> unifierState,
     NotNull<TypeCheckLimits> limits,
     DcrLogger* logger,
     const SourceModule& sourceModule,
@@ -70,6 +73,8 @@ void check(
 struct TypeChecker2
 {
     NotNull<BuiltinTypes> builtinTypes;
+    NotNull<Simplifier> simplifier;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     DcrLogger* logger;
     const NotNull<TypeCheckLimits> limits;
     const NotNull<InternalErrorReporter> ice;
@@ -88,6 +93,8 @@ struct TypeChecker2
 
     TypeChecker2(
         NotNull<BuiltinTypes> builtinTypes,
+        NotNull<Simplifier> simplifier,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<UnifierSharedState> unifierState,
         NotNull<TypeCheckLimits> limits,
         DcrLogger* logger,
@@ -109,14 +116,14 @@ private:
     std::optional<StackPusher> pushStack(AstNode* node);
     void checkForInternalTypeFunction(TypeId ty, Location location);
     TypeId checkForTypeFunctionInhabitance(TypeId instance, Location location);
-    TypePackId lookupPack(AstExpr* expr);
+    TypePackId lookupPack(AstExpr* expr) const;
     TypeId lookupType(AstExpr* expr);
     TypeId lookupAnnotation(AstType* annotation);
-    std::optional<TypePackId> lookupPackAnnotation(AstTypePack* annotation);
+    std::optional<TypePackId> lookupPackAnnotation(AstTypePack* annotation) const;
-    TypeId lookupExpectedType(AstExpr* expr);
+    TypeId lookupExpectedType(AstExpr* expr) const;
-    TypePackId lookupExpectedPack(AstExpr* expr, TypeArena& arena);
+    TypePackId lookupExpectedPack(AstExpr* expr, TypeArena& arena) const;
     TypePackId reconstructPack(AstArray<AstExpr*> exprs, TypeArena& arena);
-    Scope* findInnermostScope(Location location);
+    Scope* findInnermostScope(Location location) const;
     void visit(AstStat* stat);
     void visit(AstStatIf* ifStatement);
     void visit(AstStatWhile* whileStatement);
@@ -153,7 +160,7 @@ private:
     void visit(AstExprVarargs* expr);
     void visitCall(AstExprCall* call);
     void visit(AstExprCall* call);
-    std::optional<TypeId> tryStripUnionFromNil(TypeId ty);
+    std::optional<TypeId> tryStripUnionFromNil(TypeId ty) const;
     TypeId stripFromNilAndReport(TypeId ty, const Location& location);
     void visitExprName(AstExpr* expr, Location location, const std::string& propName, ValueContext context, TypeId astIndexExprTy);
     void visit(AstExprIndexName* indexName, ValueContext context);
@@ -168,7 +175,7 @@ private:
     void visit(AstExprInterpString* interpString);
     void visit(AstExprError* expr);
     TypeId flattenPack(TypePackId pack);
-    void visitGenerics(AstArray<AstGenericType> generics, AstArray<AstGenericTypePack> genericPacks);
+    void visitGenerics(AstArray<AstGenericType*> generics, AstArray<AstGenericTypePack*> genericPacks);
     void visit(AstType* ty);
     void visit(AstTypeReference* ty);
     void visit(AstTypeTable* table);
@@ -210,6 +217,9 @@ private:
         std::vector<TypeError>& errors
     );
 
+    // Avoid duplicate warnings being emitted for the same global variable.
+    DenseHashSet<std::string> warnedGlobals{""};
+
     void diagnoseMissingTableKey(UnknownProperty* utk, TypeErrorData& data) const;
     bool isErrorSuppressing(Location loc, TypeId ty);
     bool isErrorSuppressing(Location loc1, TypeId ty1, Location loc2, TypeId ty2);

Analysis/include/Luau/TypeFunction.h

@@ -1,29 +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 "Luau/ConstraintSolver.h"
+#include "Luau/Constraint.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/Error.h"
 #include "Luau/NotNull.h"
 #include "Luau/TypeCheckLimits.h"
+#include "Luau/TypeFunctionRuntime.h"
 #include "Luau/TypeFwd.h"
 
 #include <functional>
 #include <string>
 #include <optional>
 
+struct lua_State;
+
 namespace Luau
 {
 
 struct TypeArena;
 struct TxnLog;
+struct ConstraintSolver;
 class Normalizer;
 
+using StateRef = std::unique_ptr<lua_State, void (*)(lua_State*)>;
+
+struct TypeFunctionRuntime
+{
+    TypeFunctionRuntime(NotNull<InternalErrorReporter> ice, NotNull<TypeCheckLimits> limits);
+    ~TypeFunctionRuntime();
+
+    // Return value is an error message if registration failed
+    std::optional<std::string> registerFunction(AstStatTypeFunction* function);
+
+    // For user-defined type functions, we store all generated types and packs for the duration of the typecheck
+    TypedAllocator<TypeFunctionType> typeArena;
+    TypedAllocator<TypeFunctionTypePackVar> typePackArena;
+
+    NotNull<InternalErrorReporter> ice;
+    NotNull<TypeCheckLimits> limits;
+
+    StateRef state;
+
+    // Set of functions which have their environment table initialized
+    DenseHashSet<AstStatTypeFunction*> initialized{nullptr};
+
+    // Evaluation of type functions should only be performed in the absence of parse errors in the source module
+    bool allowEvaluation = true;
+
+    // Output created by 'print' function
+    std::vector<std::string> messages;
+
+private:
+    void prepareState();
+};
+
 struct TypeFunctionContext
 {
     NotNull<TypeArena> arena;
     NotNull<BuiltinTypes> builtins;
     NotNull<Scope> scope;
+    NotNull<Simplifier> simplifier;
     NotNull<Normalizer> normalizer;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     NotNull<InternalErrorReporter> ice;
     NotNull<TypeCheckLimits> limits;
 
@@ -33,32 +72,25 @@ struct TypeFunctionContext
     const Constraint* constraint;
 
     std::optional<AstName> userFuncName; // Name of the user-defined type function; only available for UDTFs
-    std::optional<AstExprFunction*> userFuncBody; // Body of the user-defined type function; only available for UDTFs
 
-    TypeFunctionContext(NotNull<ConstraintSolver> cs, NotNull<Scope> scope, NotNull<const Constraint> constraint)
+    TypeFunctionContext(NotNull<ConstraintSolver> cs, NotNull<Scope> scope, NotNull<const Constraint> constraint);
-        : arena(cs->arena)
-        , builtins(cs->builtinTypes)
-        , scope(scope)
-        , normalizer(cs->normalizer)
-        , ice(NotNull{&cs->iceReporter})
-        , limits(NotNull{&cs->limits})
-        , solver(cs.get())
-        , constraint(constraint.get())
-    {
-    }
 
     TypeFunctionContext(
         NotNull<TypeArena> arena,
         NotNull<BuiltinTypes> builtins,
         NotNull<Scope> scope,
+        NotNull<Simplifier> simplifier,
         NotNull<Normalizer> normalizer,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         NotNull<InternalErrorReporter> ice,
         NotNull<TypeCheckLimits> limits
     )
         : arena(arena)
         , builtins(builtins)
         , scope(scope)
+        , simplifier(simplifier)
         , normalizer(normalizer)
+        , typeFunctionRuntime(typeFunctionRuntime)
         , ice(ice)
         , limits(limits)
         , solver(nullptr)
@@ -66,7 +98,17 @@ struct TypeFunctionContext
     {
     }
 
-    NotNull<Constraint> pushConstraint(ConstraintV&& c);
+    NotNull<Constraint> pushConstraint(ConstraintV&& c) const;
+};
+
+enum class Reduction
+{
+    // The type function is either known to be reducible or the determination is blocked.
+    MaybeOk,
+    // The type function is known to be irreducible, but maybe not be erroneous, e.g. when it's over generics or free types.
+    Irreducible,
+    // The type function is known to be irreducible, and is definitely erroneous.
+    Erroneous,
 };
 
 /// Represents a reduction result, which may have successfully reduced the type,
@@ -75,19 +117,25 @@ struct TypeFunctionContext
 template<typename Ty>
 struct TypeFunctionReductionResult
 {
+
     /// The result of the reduction, if any. If this is nullopt, the type function
     /// could not be reduced.
     std::optional<Ty> result;
-    /// Whether the result is uninhabited: whether we know, unambiguously and
+    /// Indicates the status of this reduction: is `Reduction::Irreducible` if
-    /// permanently, whether this type function reduction results in an
+    /// the this result indicates the type function is irreducible, and
-    /// uninhabitable type. This will trigger an error to be reported.
+    /// `Reduction::Erroneous` if this result indicates the type function is
-    bool uninhabited;
+    /// erroneous. `Reduction::MaybeOk` otherwise.
+    Reduction reductionStatus;
     /// Any types that need to be progressed or mutated before the reduction may
     /// proceed.
     std::vector<TypeId> blockedTypes;
     /// Any type packs that need to be progressed or mutated before the
     /// reduction may proceed.
     std::vector<TypePackId> blockedPacks;
+    /// A runtime error message from user-defined type functions
+    std::optional<std::string> error;
+    /// Messages printed out from user-defined type functions
+    std::vector<std::string> messages;
 };
 
 template<typename T>
@@ -121,6 +169,7 @@ struct TypePackFunction
 struct FunctionGraphReductionResult
 {
     ErrorVec errors;
+    ErrorVec messages;
     DenseHashSet<TypeId> blockedTypes{nullptr};
     DenseHashSet<TypePackId> blockedPacks{nullptr};
     DenseHashSet<TypeId> reducedTypes{nullptr};
@@ -192,6 +241,9 @@ struct BuiltinTypeFunctions
     TypeFunction indexFunc;
     TypeFunction rawgetFunc;
 
+    TypeFunction setmetatableFunc;
+    TypeFunction getmetatableFunc;
+
     void addToScope(NotNull<TypeArena> arena, NotNull<Scope> scope) const;
 };
 

Analysis/include/Luau/TypeFunctionRuntime.h

@@ -0,0 +1,298 @@
+// 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/Variant.h"
+#include "Luau/TypeFwd.h"
+
+#include <optional>
+#include <string>
+#include <map>
+#include <vector>
+
+using lua_State = struct lua_State;
+
+namespace Luau
+{
+
+void* typeFunctionAlloc(void* ud, void* ptr, size_t osize, size_t nsize);
+
+// Replica of types from Type.h
+struct TypeFunctionType;
+using TypeFunctionTypeId = const TypeFunctionType*;
+
+struct TypeFunctionTypePackVar;
+using TypeFunctionTypePackId = const TypeFunctionTypePackVar*;
+
+struct TypeFunctionPrimitiveType
+{
+    enum Type
+    {
+        NilType,
+        Boolean,
+        Number,
+        String,
+        Thread,
+        Buffer,
+    };
+
+    Type type;
+
+    TypeFunctionPrimitiveType(Type type)
+        : type(type)
+    {
+    }
+};
+
+struct TypeFunctionBooleanSingleton
+{
+    bool value = false;
+};
+
+struct TypeFunctionStringSingleton
+{
+    std::string value;
+};
+
+using TypeFunctionSingletonVariant = Variant<TypeFunctionBooleanSingleton, TypeFunctionStringSingleton>;
+
+struct TypeFunctionSingletonType
+{
+    TypeFunctionSingletonVariant variant;
+
+    explicit TypeFunctionSingletonType(TypeFunctionSingletonVariant variant)
+        : variant(std::move(variant))
+    {
+    }
+};
+
+template<typename T>
+const T* get(const TypeFunctionSingletonType* tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? get_if<T>(&tv->variant) : nullptr;
+}
+
+template<typename T>
+T* getMutable(const TypeFunctionSingletonType* tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? get_if<T>(&const_cast<TypeFunctionSingletonType*>(tv)->variant) : nullptr;
+}
+
+struct TypeFunctionUnionType
+{
+    std::vector<TypeFunctionTypeId> components;
+};
+
+struct TypeFunctionIntersectionType
+{
+    std::vector<TypeFunctionTypeId> components;
+};
+
+struct TypeFunctionAnyType
+{
+};
+
+struct TypeFunctionUnknownType
+{
+};
+
+struct TypeFunctionNeverType
+{
+};
+
+struct TypeFunctionNegationType
+{
+    TypeFunctionTypeId type;
+};
+
+struct TypeFunctionTypePack
+{
+    std::vector<TypeFunctionTypeId> head;
+    std::optional<TypeFunctionTypePackId> tail;
+};
+
+struct TypeFunctionVariadicTypePack
+{
+    TypeFunctionTypeId type;
+};
+
+struct TypeFunctionGenericTypePack
+{
+    bool isNamed = false;
+
+    std::string name;
+};
+
+using TypeFunctionTypePackVariant = Variant<TypeFunctionTypePack, TypeFunctionVariadicTypePack, TypeFunctionGenericTypePack>;
+
+struct TypeFunctionTypePackVar
+{
+    TypeFunctionTypePackVariant type;
+
+    TypeFunctionTypePackVar(TypeFunctionTypePackVariant type)
+        : type(std::move(type))
+    {
+    }
+
+    bool operator==(const TypeFunctionTypePackVar& rhs) const;
+};
+
+struct TypeFunctionFunctionType
+{
+    std::vector<TypeFunctionTypeId> generics;
+    std::vector<TypeFunctionTypePackId> genericPacks;
+
+    TypeFunctionTypePackId argTypes;
+    TypeFunctionTypePackId retTypes;
+};
+
+template<typename T>
+const T* get(TypeFunctionTypePackId tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? get_if<T>(&tv->type) : nullptr;
+}
+
+template<typename T>
+T* getMutable(TypeFunctionTypePackId tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? get_if<T>(&const_cast<TypeFunctionTypePackVar*>(tv)->type) : nullptr;
+}
+
+struct TypeFunctionTableIndexer
+{
+    TypeFunctionTableIndexer(TypeFunctionTypeId keyType, TypeFunctionTypeId valueType)
+        : keyType(keyType)
+        , valueType(valueType)
+    {
+    }
+
+    TypeFunctionTypeId keyType;
+    TypeFunctionTypeId valueType;
+};
+
+struct TypeFunctionProperty
+{
+    static TypeFunctionProperty readonly(TypeFunctionTypeId ty);
+    static TypeFunctionProperty writeonly(TypeFunctionTypeId ty);
+    static TypeFunctionProperty rw(TypeFunctionTypeId ty);                             // Shared read-write type.
+    static TypeFunctionProperty rw(TypeFunctionTypeId read, TypeFunctionTypeId write); // Separate read-write type.
+
+    bool isReadOnly() const;
+    bool isWriteOnly() const;
+
+    std::optional<TypeFunctionTypeId> readTy;
+    std::optional<TypeFunctionTypeId> writeTy;
+};
+
+struct TypeFunctionTableType
+{
+    using Name = std::string;
+    using Props = std::map<Name, TypeFunctionProperty>;
+
+    Props props;
+
+    std::optional<TypeFunctionTableIndexer> indexer;
+
+    // Should always be a TypeFunctionTableType
+    std::optional<TypeFunctionTypeId> metatable;
+};
+
+struct TypeFunctionClassType
+{
+    using Name = std::string;
+    using Props = std::map<Name, TypeFunctionProperty>;
+
+    Props props;
+
+    std::optional<TypeFunctionTableIndexer> indexer;
+
+    std::optional<TypeFunctionTypeId> metatable; // metaclass?
+
+    // this was mistaken, and we should actually be keeping separate read/write types here.
+    std::optional<TypeFunctionTypeId> parent_DEPRECATED;
+
+    std::optional<TypeFunctionTypeId> readParent;
+    std::optional<TypeFunctionTypeId> writeParent;
+
+    TypeId classTy;
+
+    std::string name_DEPRECATED;
+};
+
+struct TypeFunctionGenericType
+{
+    bool isNamed = false;
+    bool isPack = false;
+
+    std::string name;
+};
+
+using TypeFunctionTypeVariant = Luau::Variant<
+    TypeFunctionPrimitiveType,
+    TypeFunctionAnyType,
+    TypeFunctionUnknownType,
+    TypeFunctionNeverType,
+    TypeFunctionSingletonType,
+    TypeFunctionUnionType,
+    TypeFunctionIntersectionType,
+    TypeFunctionNegationType,
+    TypeFunctionFunctionType,
+    TypeFunctionTableType,
+    TypeFunctionClassType,
+    TypeFunctionGenericType>;
+
+struct TypeFunctionType
+{
+    TypeFunctionTypeVariant type;
+
+    TypeFunctionType(TypeFunctionTypeVariant type)
+        : type(std::move(type))
+    {
+    }
+
+    bool operator==(const TypeFunctionType& rhs) const;
+};
+
+template<typename T>
+const T* get(TypeFunctionTypeId tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? Luau::get_if<T>(&tv->type) : nullptr;
+}
+
+template<typename T>
+T* getMutable(TypeFunctionTypeId tv)
+{
+    LUAU_ASSERT(tv);
+
+    return tv ? Luau::get_if<T>(&const_cast<TypeFunctionType*>(tv)->type) : nullptr;
+}
+
+std::optional<std::string> checkResultForError(lua_State* L, const char* typeFunctionName, int luaResult);
+
+TypeFunctionType* allocateTypeFunctionType(lua_State* L, TypeFunctionTypeVariant type);
+TypeFunctionTypePackVar* allocateTypeFunctionTypePack(lua_State* L, TypeFunctionTypePackVariant type);
+
+void allocTypeUserData(lua_State* L, TypeFunctionTypeVariant type);
+
+bool isTypeUserData(lua_State* L, int idx);
+TypeFunctionTypeId getTypeUserData(lua_State* L, int idx);
+std::optional<TypeFunctionTypeId> optionalTypeUserData(lua_State* L, int idx);
+
+void registerTypesLibrary(lua_State* L);
+void registerTypeUserData(lua_State* L);
+
+void setTypeFunctionEnvironment(lua_State* L);
+
+void resetTypeFunctionState(lua_State* L);
+
+} // namespace Luau

Analysis/include/Luau/TypeFunctionRuntimeBuilder.h

@@ -0,0 +1,50 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Type.h"
+#include "Luau/TypeFunction.h"
+#include "Luau/TypeFunctionRuntime.h"
+
+namespace Luau
+{
+
+using Kind = Variant<TypeId, TypePackId>;
+
+template<typename T>
+const T* get(const Kind& kind)
+{
+    return get_if<T>(&kind);
+}
+
+using TypeFunctionKind = Variant<TypeFunctionTypeId, TypeFunctionTypePackId>;
+
+template<typename T>
+const T* get(const TypeFunctionKind& tfkind)
+{
+    return get_if<T>(&tfkind);
+}
+
+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
+    std::vector<std::string> errors{};
+
+    TypeFunctionRuntimeBuilderState(NotNull<TypeFunctionContext> ctx)
+        : ctx(ctx)
+    {
+    }
+};
+
+TypeFunctionTypeId serialize(TypeId ty, TypeFunctionRuntimeBuilderState* state);
+TypeId deserialize(TypeFunctionTypeId ty, TypeFunctionRuntimeBuilderState* state);
+
+} // namespace Luau

Analysis/include/Luau/TypeInfer.h

@@ -399,8 +399,8 @@ private:
         const ScopePtr& scope,
         std::optional<TypeLevel> levelOpt,
         const AstNode& node,
-        const AstArray<AstGenericType>& genericNames,
+        const AstArray<AstGenericType*>& genericNames,
-        const AstArray<AstGenericTypePack>& genericPackNames,
+        const AstArray<AstGenericTypePack*>& genericPackNames,
         bool useCache = false
     );
 

Analysis/include/Luau/TypePack.h

@@ -52,7 +52,7 @@ struct GenericTypePack
 };
 
 using BoundTypePack = Unifiable::Bound<TypePackId>;
-using ErrorTypePack = Unifiable::Error;
+using ErrorTypePack = Unifiable::Error<TypePackId>;
 
 using TypePackVariant =
     Unifiable::Variant<TypePackId, FreeTypePack, GenericTypePack, TypePack, VariadicTypePack, BlockedTypePack, TypeFunctionInstanceTypePack>;

Analysis/include/Luau/TypePath.h

@@ -51,6 +51,8 @@ struct Index
 /// Represents fields of a type or pack that contain a type.
 enum class TypeField
 {
+    /// The table of a metatable type.
+    Table,
     /// The metatable of a type. This could be a metatable type, a primitive
     /// type, a class type, or perhaps even a string singleton type.
     Metatable,

Analysis/include/Luau/TypeUtils.h

@@ -40,7 +40,7 @@ struct InConditionalContext
     TypeContext* typeContext;
     TypeContext oldValue;
 
-    InConditionalContext(TypeContext* c)
+    explicit InConditionalContext(TypeContext* c)
         : typeContext(c)
         , oldValue(*c)
     {
@@ -248,4 +248,45 @@ std::optional<Ty> follow(std::optional<Ty> ty)
         return std::nullopt;
 }
 
+/**
+ * Returns whether or not expr is a literal expression, for example:
+ * - Scalar literals (numbers, booleans, strings, nil)
+ * - Table literals
+ * - Lambdas (a "function literal")
+ */
+bool isLiteral(const AstExpr* expr);
+
+/**
+ * Given a table literal and a mapping from expression to type, determine
+ * whether any literal expression in this table depends on any blocked types.
+ * This is used as a precondition for bidirectional inference: be warned that
+ * the behavior of this algorithm is tightly coupled to that of bidirectional
+ * inference.
+ * @param expr Expression to search
+ * @param astTypes Mapping from AST node to TypeID
+ * @returns A vector of blocked types
+ */
+std::vector<TypeId> findBlockedTypesIn(AstExprTable* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes);
+
+/**
+ * Given a function call and a mapping from expression to type, determine
+ * whether the type of any argument in said call in depends on a blocked types.
+ * This is used as a precondition for bidirectional inference: be warned that
+ * the behavior of this algorithm is tightly coupled to that of bidirectional
+ * inference.
+ * @param expr Expression to search
+ * @param astTypes Mapping from AST node to TypeID
+ * @returns A vector of blocked types
+ */
+std::vector<TypeId> findBlockedArgTypesIn(AstExprCall* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes);
+
+/**
+ * Given a scope and a free type, find the closest parent that has a present
+ * `interiorFreeTypes` and append the given type to said list. This list will
+ * be generalized when the requiste `GeneralizationConstraint` is resolved.
+ * @param scope Initial scope this free type was attached to
+ * @param ty Free type to track.
+ */
+void trackInteriorFreeType(Scope* scope, TypeId ty);
+
 } // namespace Luau

Analysis/include/Luau/Unifiable.h

@@ -3,6 +3,7 @@
 
 #include "Luau/Variant.h"
 
+#include <optional>
 #include <string>
 
 namespace Luau
@@ -94,19 +95,29 @@ struct Bound
     Id boundTo;
 };
 
+template<typename Id>
 struct Error
 {
     // This constructor has to be public, since it's used in Type and TypePack,
     // but shouldn't be called directly. Please use errorRecoveryType() instead.
-    Error();
+    explicit Error();
+
+    explicit Error(Id synthetic)
+        : synthetic{synthetic}
+    {
+    }
 
     int index;
 
+    // This is used to create an error that can be rendered out using this field
+    // as appropriate metadata for communicating it to the user.
+    std::optional<Id> synthetic;
+
 private:
     static int nextIndex;
 };
 
 template<typename Id, typename... Value>
-using Variant = Luau::Variant<Bound<Id>, Error, Value...>;
+using Variant = Luau::Variant<Bound<Id>, Error<Id>, Value...>;
 
 } // namespace Luau::Unifiable

Analysis/include/Luau/Unifier.h

@@ -93,10 +93,6 @@ struct Unifier
 
     Unifier(NotNull<Normalizer> normalizer, NotNull<Scope> scope, const Location& location, Variance variance, TxnLog* parentLog = nullptr);
 
-    // Configure the Unifier to test for scope subsumption via embedded Scope
-    // pointers rather than TypeLevels.
-    void enableNewSolver();
-
     // Test whether the two type vars unify.  Never commits the result.
     ErrorVec canUnify(TypeId subTy, TypeId superTy);
     ErrorVec canUnify(TypePackId subTy, TypePackId superTy, bool isFunctionCall = false);
@@ -169,7 +165,6 @@ private:
 
     std::optional<TypeId> findTablePropertyRespectingMeta(TypeId lhsType, Name name);
 
-    TxnLog combineLogsIntoIntersection(std::vector<TxnLog> logs);
     TxnLog combineLogsIntoUnion(std::vector<TxnLog> logs);
 
 public:
@@ -179,7 +174,7 @@ public:
     bool occursCheck(TypePackId needle, TypePackId haystack, bool reversed);
     bool occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, TypePackId haystack);
 
-    Unifier makeChildUnifier();
+    std::unique_ptr<Unifier> makeChildUnifier();
 
     void reportError(TypeError err);
     LUAU_NOINLINE void reportError(Location location, TypeErrorData data);
@@ -195,11 +190,6 @@ private:
 
     // Available after regular type pack unification errors
     std::optional<int> firstPackErrorPos;
-
-    // If true, we do a bunch of small things differently to work better with
-    // the new type inference engine. Most notably, we use the Scope hierarchy
-    // directly rather than using TypeLevels.
-    bool useNewSolver = false;
 };
 
 void promoteTypeLevels(TxnLog& log, const TypeArena* arena, TypeLevel minLevel, Scope* outerScope, bool useScope, TypePackId tp);

Analysis/include/Luau/UnifierSharedState.h

@@ -49,6 +49,26 @@ struct UnifierSharedState
     DenseHashSet<TypePackId> tempSeenTp{nullptr};
 
     UnifierCounters counters;
+
+    bool reentrantTypeReduction = false;
+};
+
+struct TypeReductionRentrancyGuard final
+{
+    explicit TypeReductionRentrancyGuard(NotNull<UnifierSharedState> sharedState)
+        : sharedState{sharedState}
+    {
+        sharedState->reentrantTypeReduction = true;
+    }
+    ~TypeReductionRentrancyGuard()
+    {
+        sharedState->reentrantTypeReduction = false;
+    }
+    TypeReductionRentrancyGuard(const TypeReductionRentrancyGuard&) = delete;
+    TypeReductionRentrancyGuard(TypeReductionRentrancyGuard&&) = delete;
+
+private:
+    NotNull<UnifierSharedState> sharedState;
 };
 
 } // namespace Luau

Analysis/include/Luau/VisitType.h

@@ -10,7 +10,6 @@
 #include "Type.h"
 
 LUAU_FASTINT(LuauVisitRecursionLimit)
-LUAU_FASTFLAG(LuauBoundLazyTypes2)
 LUAU_FASTFLAG(LuauSolverV2)
 
 namespace Luau
@@ -86,6 +85,8 @@ struct GenericTypeVisitor
     {
     }
 
+    virtual ~GenericTypeVisitor() {}
+
     virtual void cycle(TypeId) {}
     virtual void cycle(TypePackId) {}
 
@@ -133,6 +134,10 @@ struct GenericTypeVisitor
     {
         return visit(ty);
     }
+    virtual bool visit(TypeId ty, const NoRefineType& nrt)
+    {
+        return visit(ty);
+    }
     virtual bool visit(TypeId ty, const UnknownType& utv)
     {
         return visit(ty);
@@ -186,7 +191,7 @@ struct GenericTypeVisitor
     {
         return visit(tp);
     }
-    virtual bool visit(TypePackId tp, const Unifiable::Error& etp)
+    virtual bool visit(TypePackId tp, const ErrorTypePack& etp)
     {
         return visit(tp);
     }
@@ -345,6 +350,8 @@ struct GenericTypeVisitor
         }
         else if (auto atv = get<AnyType>(ty))
             visit(ty, *atv);
+        else if (auto nrt = get<NoRefineType>(ty))
+            visit(ty, *nrt);
         else if (auto utv = get<UnionType>(ty))
         {
             if (visit(ty, *utv))
@@ -455,7 +462,7 @@ struct GenericTypeVisitor
         else if (auto gtv = get<GenericTypePack>(tp))
             visit(tp, *gtv);
 
-        else if (auto etv = get<Unifiable::Error>(tp))
+        else if (auto etv = get<ErrorTypePack>(tp))
             visit(tp, *etv);
 
         else if (auto pack = get<TypePack>(tp))

Analysis/src/AnyTypeSummary.cpp

@@ -38,7 +38,7 @@
 
 #include <stdio.h>
 
-LUAU_FASTFLAGVARIABLE(StudioReportLuauAny2, false);
+LUAU_FASTFLAGVARIABLE(StudioReportLuauAny2);
 LUAU_FASTINTVARIABLE(LuauAnySummaryRecursionLimit, 300);
 
 LUAU_FASTFLAG(DebugLuauMagicTypes);
@@ -177,7 +177,6 @@ void AnyTypeSummary::visit(const Scope* scope, AstStatReturn* ret, const Module*
             }
         }
     }
-
 }
 
 void AnyTypeSummary::visit(const Scope* scope, AstStatLocal* local, const Module* module, NotNull<BuiltinTypes> builtinTypes)

Analysis/src/AstJsonEncoder.cpp

@@ -425,6 +425,7 @@ struct AstJsonEncoder : public AstVisitor
             "AstExprFunction",
             [&]()
             {
+                PROP(attributes);
                 PROP(generics);
                 PROP(genericPacks);
                 if (node->self)
@@ -881,7 +882,7 @@ struct AstJsonEncoder : public AstVisitor
                 PROP(name);
                 PROP(generics);
                 PROP(genericPacks);
-                PROP(type);
+                write("value", node->type);
                 PROP(exported);
             }
         );
@@ -894,7 +895,7 @@ struct AstJsonEncoder : public AstVisitor
             "AstStatDeclareFunction",
             [&]()
             {
-                // TODO: attributes
+                PROP(attributes);
                 PROP(name);
                 PROP(nameLocation);
                 PROP(params);
@@ -1042,6 +1043,7 @@ struct AstJsonEncoder : public AstVisitor
             "AstTypeFunction",
             [&]()
             {
+                PROP(attributes);
                 PROP(generics);
                 PROP(genericPacks);
                 PROP(argTypes);
@@ -1136,6 +1138,42 @@ struct AstJsonEncoder : public AstVisitor
         );
     }
 
+    void write(AstAttr::Type type)
+    {
+        switch (type)
+        {
+        case AstAttr::Type::Checked:
+            return writeString("checked");
+        case AstAttr::Type::Native:
+            return writeString("native");
+        }
+    }
+
+    void write(class AstAttr* node)
+    {
+        writeNode(
+            node,
+            "AstAttr",
+            [&]()
+            {
+                write("name", node->type);
+            }
+        );
+    }
+
+    bool visit(class AstTypeGroup* node) override
+    {
+        writeNode(
+            node,
+            "AstTypeGroup",
+            [&]()
+            {
+                write("inner", node->type);
+            }
+        );
+        return false;
+    }
+
     bool visit(class AstTypeSingletonBool* node) override
     {
         writeNode(

Analysis/src/AstQuery.cpp

@@ -13,6 +13,8 @@
 
 LUAU_FASTFLAG(LuauSolverV2)
 
+LUAU_FASTFLAG(LuauExtendStatEndPosWithSemicolon)
+
 namespace Luau
 {
 
@@ -40,12 +42,27 @@ 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))
+            {
+                ancestry.push_back(stat);
+                return true;
+            }
+        }
+        else
         {
             if (stat->location.begin < pos && pos <= stat->location.end)
             {
                 ancestry.push_back(stat);
                 return true;
             }
+        }
+
         return false;
     }
 
@@ -509,6 +526,37 @@ static std::optional<DocumentationSymbol> checkOverloadedDocumentationSymbol(
     return documentationSymbol;
 }
 
+static std::optional<DocumentationSymbol> getMetatableDocumentation(
+    const Module& module,
+    AstExpr* parentExpr,
+    const TableType* mtable,
+    const AstName& index
+)
+{
+    auto indexIt = mtable->props.find("__index");
+    if (indexIt == mtable->props.end())
+        return std::nullopt;
+
+    TypeId followed = follow(indexIt->second.type());
+    const TableType* ttv = get<TableType>(followed);
+    if (!ttv)
+        return std::nullopt;
+
+    auto propIt = ttv->props.find(index.value);
+    if (propIt == ttv->props.end())
+        return std::nullopt;
+
+    if (FFlag::LuauSolverV2)
+    {
+        if (auto ty = propIt->second.readTy)
+            return checkOverloadedDocumentationSymbol(module, *ty, parentExpr, propIt->second.documentationSymbol);
+    }
+    else
+        return checkOverloadedDocumentationSymbol(module, propIt->second.type(), parentExpr, propIt->second.documentationSymbol);
+
+    return std::nullopt;
+}
+
 std::optional<DocumentationSymbol> getDocumentationSymbolAtPosition(const SourceModule& source, const Module& module, Position position)
 {
     std::vector<AstNode*> ancestry = findAstAncestryOfPosition(source, position);
@@ -540,6 +588,8 @@ std::optional<DocumentationSymbol> getDocumentationSymbolAtPosition(const Source
                     }
                 }
                 else if (const ClassType* ctv = get<ClassType>(parentTy))
+                {
+                    while (ctv)
                     {
                         if (auto propIt = ctv->props.find(indexName->index.value); propIt != ctv->props.end())
                         {
@@ -549,7 +599,19 @@ std::optional<DocumentationSymbol> getDocumentationSymbolAtPosition(const Source
                                     return checkOverloadedDocumentationSymbol(module, *ty, parentExpr, propIt->second.documentationSymbol);
                             }
                             else
-                            return checkOverloadedDocumentationSymbol(module, propIt->second.type(), parentExpr, propIt->second.documentationSymbol);
+                                return checkOverloadedDocumentationSymbol(
+                                    module, propIt->second.type(), parentExpr, propIt->second.documentationSymbol
+                                );
+                        }
+                        ctv = ctv->parent ? Luau::get<Luau::ClassType>(*ctv->parent) : nullptr;
+                    }
+                }
+                else if (const PrimitiveType* ptv = get<PrimitiveType>(parentTy); ptv && ptv->metatable)
+                {
+                    if (auto mtable = get<TableType>(*ptv->metatable))
+                    {
+                        if (std::optional<std::string> docSymbol = getMetatableDocumentation(module, parentExpr, mtable, indexName->index))
+                            return docSymbol;
                     }
                 }
             }

Analysis/src/AutocompleteCore.h

@@ -0,0 +1,27 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/AutocompleteTypes.h"
+
+namespace Luau
+{
+struct Module;
+struct FileResolver;
+
+using ModulePtr = std::shared_ptr<Module>;
+using ModuleName = std::string;
+
+
+AutocompleteResult autocomplete_(
+    const ModulePtr& module,
+    NotNull<BuiltinTypes> builtinTypes,
+    TypeArena* typeArena,
+    std::vector<AstNode*>& ancestry,
+    Scope* globalScope,
+    const ScopePtr& scopeAtPosition,
+    Position position,
+    FileResolver* fileResolver,
+    StringCompletionCallback callback
+);
+
+} // namespace Luau

Analysis/src/BuiltinDefinitions.cpp

@@ -2,6 +2,9 @@
 #include "Luau/BuiltinDefinitions.h"
 
 #include "Luau/Ast.h"
+#include "Luau/Clone.h"
+#include "Luau/DenseHash.h"
+#include "Luau/Error.h"
 #include "Luau/Frontend.h"
 #include "Luau/Symbol.h"
 #include "Luau/Common.h"
@@ -25,47 +28,93 @@
  * about a function that takes any number of values, but where each value must have some specific type.
  */
 
-LUAU_FASTFLAG(LuauSolverV2);
+LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAGVARIABLE(LuauDCRMagicFunctionTypeChecker, false);
+LUAU_FASTFLAGVARIABLE(LuauStringFormatErrorSuppression)
+LUAU_FASTFLAGVARIABLE(LuauTableCloneClonesType3)
+LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope)
+LUAU_FASTFLAGVARIABLE(LuauFreezeIgnorePersistent)
+LUAU_FASTFLAGVARIABLE(LuauFollowTableFreeze)
 
 namespace Luau
 {
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionSelect(
+struct MagicSelect final : MagicFunction
-    TypeChecker& typechecker,
+{
-    const ScopePtr& scope,
+    std::optional<WithPredicate<TypePackId>>
-    const AstExprCall& expr,
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
-    WithPredicate<TypePackId> withPredicate
+    bool infer(const MagicFunctionCallContext& ctx) override;
-);
+};
-static std::optional<WithPredicate<TypePackId>> magicFunctionSetMetaTable(
-    TypeChecker& typechecker,
-    const ScopePtr& scope,
-    const AstExprCall& expr,
-    WithPredicate<TypePackId> withPredicate
-);
-static std::optional<WithPredicate<TypePackId>> magicFunctionAssert(
-    TypeChecker& typechecker,
-    const ScopePtr& scope,
-    const AstExprCall& expr,
-    WithPredicate<TypePackId> withPredicate
-);
-static std::optional<WithPredicate<TypePackId>> magicFunctionPack(
-    TypeChecker& typechecker,
-    const ScopePtr& scope,
-    const AstExprCall& expr,
-    WithPredicate<TypePackId> withPredicate
-);
-static std::optional<WithPredicate<TypePackId>> magicFunctionRequire(
-    TypeChecker& typechecker,
-    const ScopePtr& scope,
-    const AstExprCall& expr,
-    WithPredicate<TypePackId> withPredicate
-);
 
+struct MagicSetMetatable final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
 
-static bool dcrMagicFunctionSelect(MagicFunctionCallContext context);
+struct MagicAssert final : MagicFunction
-static bool dcrMagicFunctionRequire(MagicFunctionCallContext context);
+{
-static bool dcrMagicFunctionPack(MagicFunctionCallContext context);
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicPack final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicRequire final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicClone final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicFreeze final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicFormat final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+    bool typeCheck(const MagicFunctionTypeCheckContext& ctx) override;
+};
+
+struct MagicMatch final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicGmatch final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
+
+struct MagicFind final : MagicFunction
+{
+    std::optional<WithPredicate<TypePackId>>
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>) override;
+    bool infer(const MagicFunctionCallContext& ctx) override;
+};
 
 TypeId makeUnion(TypeArena& arena, std::vector<TypeId>&& types)
 {
@@ -160,34 +209,10 @@ TypeId makeFunction(
     return arena.addType(std::move(ftv));
 }
 
-void attachMagicFunction(TypeId ty, MagicFunction fn)
+void attachMagicFunction(TypeId ty, std::shared_ptr<MagicFunction> magic)
 {
     if (auto ftv = getMutable<FunctionType>(ty))
-        ftv->magicFunction = fn;
+        ftv->magic = std::move(magic);
-    else
-        LUAU_ASSERT(!"Got a non functional type");
-}
-
-void attachDcrMagicFunction(TypeId ty, DcrMagicFunction fn)
-{
-    if (auto ftv = getMutable<FunctionType>(ty))
-        ftv->dcrMagicFunction = fn;
-    else
-        LUAU_ASSERT(!"Got a non functional type");
-}
-
-void attachDcrMagicRefinement(TypeId ty, DcrMagicRefinement fn)
-{
-    if (auto ftv = getMutable<FunctionType>(ty))
-        ftv->dcrMagicRefinement = fn;
-    else
-        LUAU_ASSERT(!"Got a non functional type");
-}
-
-void attachDcrMagicFunctionTypeCheck(TypeId ty, DcrMagicFunctionTypeCheck fn)
-{
-    if (auto ftv = getMutable<FunctionType>(ty))
-        ftv->dcrMagicTypeCheck = fn;
     else
         LUAU_ASSERT(!"Got a non functional type");
 }
@@ -293,6 +318,28 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
 
     addGlobalBinding(globals, "string", it->second.type(), "@luau");
 
+    // Setup 'vector' metatable
+    if (auto it = globals.globalScope->exportedTypeBindings.find("vector"); it != globals.globalScope->exportedTypeBindings.end())
+    {
+        TypeId vectorTy = it->second.type;
+        ClassType* vectorCls = getMutable<ClassType>(vectorTy);
+
+        vectorCls->metatable = arena.addType(TableType{{}, std::nullopt, TypeLevel{}, TableState::Sealed});
+        TableType* metatableTy = Luau::getMutable<TableType>(vectorCls->metatable);
+
+        metatableTy->props["__add"] = {makeFunction(arena, vectorTy, {vectorTy}, {vectorTy})};
+        metatableTy->props["__sub"] = {makeFunction(arena, vectorTy, {vectorTy}, {vectorTy})};
+        metatableTy->props["__unm"] = {makeFunction(arena, vectorTy, {}, {vectorTy})};
+
+        std::initializer_list<TypeId> mulOverloads{
+            makeFunction(arena, vectorTy, {vectorTy}, {vectorTy}),
+            makeFunction(arena, vectorTy, {builtinTypes->numberType}, {vectorTy}),
+        };
+        metatableTy->props["__mul"] = {makeIntersection(arena, mulOverloads)};
+        metatableTy->props["__div"] = {makeIntersection(arena, mulOverloads)};
+        metatableTy->props["__idiv"] = {makeIntersection(arena, mulOverloads)};
+    }
+
     // next<K, V>(t: Table<K, V>, i: K?) -> (K?, V)
     TypePackId nextArgsTypePack = arena.addTypePack(TypePack{{mapOfKtoV, makeOption(builtinTypes, arena, genericK)}});
     TypePackId nextRetsTypePack = arena.addTypePack(TypePack{{makeOption(builtinTypes, arena, genericK), genericV}});
@@ -363,7 +410,7 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
         }
     }
 
-    attachMagicFunction(getGlobalBinding(globals, "assert"), magicFunctionAssert);
+    attachMagicFunction(getGlobalBinding(globals, "assert"), std::make_shared<MagicAssert>());
 
     if (FFlag::LuauSolverV2)
     {
@@ -379,9 +426,8 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
         addGlobalBinding(globals, "assert", assertTy, "@luau");
     }
 
-    attachMagicFunction(getGlobalBinding(globals, "setmetatable"), magicFunctionSetMetaTable);
+    attachMagicFunction(getGlobalBinding(globals, "setmetatable"), std::make_shared<MagicSetMetatable>());
-    attachMagicFunction(getGlobalBinding(globals, "select"), magicFunctionSelect);
+    attachMagicFunction(getGlobalBinding(globals, "select"), std::make_shared<MagicSelect>());
-    attachDcrMagicFunction(getGlobalBinding(globals, "select"), dcrMagicFunctionSelect);
 
     if (TableType* ttv = getMutable<TableType>(getGlobalBinding(globals, "table")))
     {
@@ -394,8 +440,10 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
             // but it'll be ok for now.
             TypeId genericTy = arena.addType(GenericType{"T"});
             TypePackId thePack = arena.addTypePack({genericTy});
+            TypeId idTyWithMagic = arena.addType(FunctionType{{genericTy}, {}, thePack, thePack});
+            ttv->props["freeze"] = makeProperty(idTyWithMagic, "@luau/global/table.freeze");
+
             TypeId idTy = arena.addType(FunctionType{{genericTy}, {}, thePack, thePack});
-            ttv->props["freeze"] = makeProperty(idTy, "@luau/global/table.freeze");
             ttv->props["clone"] = makeProperty(idTy, "@luau/global/table.clone");
         }
         else
@@ -410,12 +458,15 @@ void registerBuiltinGlobals(Frontend& frontend, GlobalTypes& globals, bool typeC
         ttv->props["foreach"].deprecated = true;
         ttv->props["foreachi"].deprecated = true;
 
-        attachMagicFunction(ttv->props["pack"].type(), magicFunctionPack);
+        attachMagicFunction(ttv->props["pack"].type(), std::make_shared<MagicPack>());
-        attachDcrMagicFunction(ttv->props["pack"].type(), dcrMagicFunctionPack);
+        if (FFlag::LuauTableCloneClonesType3)
+            attachMagicFunction(ttv->props["clone"].type(), std::make_shared<MagicClone>());
+        attachMagicFunction(ttv->props["freeze"].type(), std::make_shared<MagicFreeze>());
     }
 
-    attachMagicFunction(getGlobalBinding(globals, "require"), magicFunctionRequire);
+    TypeId requireTy = getGlobalBinding(globals, "require");
-    attachDcrMagicFunction(getGlobalBinding(globals, "require"), dcrMagicFunctionRequire);
+    attachTag(requireTy, kRequireTagName);
+    attachMagicFunction(requireTy, std::make_shared<MagicRequire>());
 }
 
 static std::vector<TypeId> parseFormatString(NotNull<BuiltinTypes> builtinTypes, const char* data, size_t size)
@@ -454,7 +505,7 @@ static std::vector<TypeId> parseFormatString(NotNull<BuiltinTypes> builtinTypes,
     return result;
 }
 
-std::optional<WithPredicate<TypePackId>> magicFunctionFormat(
+std::optional<WithPredicate<TypePackId>> MagicFormat::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -504,7 +555,7 @@ std::optional<WithPredicate<TypePackId>> magicFunctionFormat(
     return WithPredicate<TypePackId>{arena.addTypePack({typechecker.stringType})};
 }
 
-static bool dcrMagicFunctionFormat(MagicFunctionCallContext context)
+bool MagicFormat::infer(const MagicFunctionCallContext& context)
 {
     TypeArena* arena = context.solver->arena;
 
@@ -548,7 +599,7 @@ static bool dcrMagicFunctionFormat(MagicFunctionCallContext context)
     return true;
 }
 
-static void dcrMagicFunctionTypeCheckFormat(MagicFunctionTypeCheckContext context)
+bool MagicFormat::typeCheck(const MagicFunctionTypeCheckContext& context)
 {
     AstExprConstantString* fmt = nullptr;
     if (auto index = context.callSite->func->as<AstExprIndexName>(); index && context.callSite->self)
@@ -563,7 +614,10 @@ static void dcrMagicFunctionTypeCheckFormat(MagicFunctionTypeCheckContext contex
         fmt = context.callSite->args.data[0]->as<AstExprConstantString>();
 
     if (!fmt)
-        return;
+    {
+        context.typechecker->reportError(CountMismatch{1, std::nullopt, 0, CountMismatch::Arg, true, "string.format"}, context.callSite->location);
+        return true;
+    }
 
     std::vector<TypeId> expected = parseFormatString(context.builtinTypes, fmt->value.data, fmt->value.size);
     const auto& [params, tail] = flatten(context.arguments);
@@ -579,7 +633,25 @@ static void dcrMagicFunctionTypeCheckFormat(MagicFunctionTypeCheckContext contex
         Location location = context.callSite->args.data[i + (calledWithSelf ? 0 : paramOffset)]->location;
         // use subtyping instead here
         SubtypingResult result = context.typechecker->subtyping->isSubtype(actualTy, expectedTy, context.checkScope);
+
         if (!result.isSubtype)
+        {
+            if (FFlag::LuauStringFormatErrorSuppression)
+            {
+                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
             {
                 Reasonings reasonings = context.typechecker->explainReasonings(actualTy, expectedTy, location, result);
                 context.typechecker->reportError(TypeMismatch{expectedTy, actualTy, reasonings.toString()}, location);
@@ -587,6 +659,9 @@ static void dcrMagicFunctionTypeCheckFormat(MagicFunctionTypeCheckContext contex
         }
     }
 
+    return true;
+}
+
 static std::vector<TypeId> parsePatternString(NotNull<BuiltinTypes> builtinTypes, const char* data, size_t size)
 {
     std::vector<TypeId> result;
@@ -647,7 +722,7 @@ static std::vector<TypeId> parsePatternString(NotNull<BuiltinTypes> builtinTypes
     return result;
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionGmatch(
+std::optional<WithPredicate<TypePackId>> MagicGmatch::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -683,7 +758,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionGmatch(
     return WithPredicate<TypePackId>{arena.addTypePack({iteratorType})};
 }
 
-static bool dcrMagicFunctionGmatch(MagicFunctionCallContext context)
+bool MagicGmatch::infer(const MagicFunctionCallContext& context)
 {
     const auto& [params, tail] = flatten(context.arguments);
 
@@ -716,7 +791,7 @@ static bool dcrMagicFunctionGmatch(MagicFunctionCallContext context)
     return true;
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionMatch(
+std::optional<WithPredicate<TypePackId>> MagicMatch::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -756,7 +831,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionMatch(
     return WithPredicate<TypePackId>{returnList};
 }
 
-static bool dcrMagicFunctionMatch(MagicFunctionCallContext context)
+bool MagicMatch::infer(const MagicFunctionCallContext& context)
 {
     const auto& [params, tail] = flatten(context.arguments);
 
@@ -792,7 +867,7 @@ static bool dcrMagicFunctionMatch(MagicFunctionCallContext context)
     return true;
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionFind(
+std::optional<WithPredicate<TypePackId>> MagicFind::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -850,7 +925,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionFind(
     return WithPredicate<TypePackId>{returnList};
 }
 
-static bool dcrMagicFunctionFind(MagicFunctionCallContext context)
+bool MagicFind::infer(const MagicFunctionCallContext& context)
 {
     const auto& [params, tail] = flatten(context.arguments);
 
@@ -927,12 +1002,9 @@ TypeId makeStringMetatable(NotNull<BuiltinTypes> builtinTypes)
 
 
     FunctionType formatFTV{arena->addTypePack(TypePack{{stringType}, variadicTailPack}), oneStringPack};
-    formatFTV.magicFunction = &magicFunctionFormat;
     formatFTV.isCheckedFunction = true;
     const TypeId formatFn = arena->addType(formatFTV);
-    attachDcrMagicFunction(formatFn, dcrMagicFunctionFormat);
+    attachMagicFunction(formatFn, std::make_shared<MagicFormat>());
-    if (FFlag::LuauDCRMagicFunctionTypeChecker)
-        attachDcrMagicFunctionTypeCheck(formatFn, dcrMagicFunctionTypeCheckFormat);
 
 
     const TypeId stringToStringType = makeFunction(*arena, std::nullopt, {}, {}, {stringType}, {}, {stringType}, /* checked */ true);
@@ -946,16 +1018,14 @@ TypeId makeStringMetatable(NotNull<BuiltinTypes> builtinTypes)
         makeFunction(*arena, stringType, {}, {}, {stringType, replArgType, optionalNumber}, {}, {stringType, numberType}, /* checked */ false);
     const TypeId gmatchFunc =
         makeFunction(*arena, stringType, {}, {}, {stringType}, {}, {arena->addType(FunctionType{emptyPack, stringVariadicList})}, /* checked */ true);
-    attachMagicFunction(gmatchFunc, magicFunctionGmatch);
+    attachMagicFunction(gmatchFunc, std::make_shared<MagicGmatch>());
-    attachDcrMagicFunction(gmatchFunc, dcrMagicFunctionGmatch);
 
     FunctionType matchFuncTy{
         arena->addTypePack({stringType, stringType, optionalNumber}), arena->addTypePack(TypePackVar{VariadicTypePack{stringType}})
     };
     matchFuncTy.isCheckedFunction = true;
     const TypeId matchFunc = arena->addType(matchFuncTy);
-    attachMagicFunction(matchFunc, magicFunctionMatch);
+    attachMagicFunction(matchFunc, std::make_shared<MagicMatch>());
-    attachDcrMagicFunction(matchFunc, dcrMagicFunctionMatch);
 
     FunctionType findFuncTy{
         arena->addTypePack({stringType, stringType, optionalNumber, optionalBoolean}),
@@ -963,8 +1033,7 @@ TypeId makeStringMetatable(NotNull<BuiltinTypes> builtinTypes)
     };
     findFuncTy.isCheckedFunction = true;
     const TypeId findFunc = arena->addType(findFuncTy);
-    attachMagicFunction(findFunc, magicFunctionFind);
+    attachMagicFunction(findFunc, std::make_shared<MagicFind>());
-    attachDcrMagicFunction(findFunc, dcrMagicFunctionFind);
 
     // string.byte : string -> number? -> number? -> ...number
     FunctionType stringDotByte{arena->addTypePack({stringType, optionalNumber, optionalNumber}), numberVariadicList};
@@ -1025,7 +1094,7 @@ TypeId makeStringMetatable(NotNull<BuiltinTypes> builtinTypes)
     return arena->addType(TableType{{{{"__index", {tableType}}}}, std::nullopt, TypeLevel{}, TableState::Sealed});
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionSelect(
+std::optional<WithPredicate<TypePackId>> MagicSelect::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -1070,7 +1139,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionSelect(
     return std::nullopt;
 }
 
-static bool dcrMagicFunctionSelect(MagicFunctionCallContext context)
+bool MagicSelect::infer(const MagicFunctionCallContext& context)
 {
     if (context.callSite->args.size <= 0)
     {
@@ -1115,7 +1184,7 @@ static bool dcrMagicFunctionSelect(MagicFunctionCallContext context)
     return false;
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionSetMetaTable(
+std::optional<WithPredicate<TypePackId>> MagicSetMetatable::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -1197,7 +1266,12 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionSetMetaTable(
     return WithPredicate<TypePackId>{arena.addTypePack({target})};
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionAssert(
+bool MagicSetMetatable::infer(const MagicFunctionCallContext&)
+{
+    return false;
+}
+
+std::optional<WithPredicate<TypePackId>> MagicAssert::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -1231,7 +1305,12 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionAssert(
     return WithPredicate<TypePackId>{arena.addTypePack(TypePack{std::move(head), tail})};
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionPack(
+bool MagicAssert::infer(const MagicFunctionCallContext&)
+{
+    return false;
+}
+
+std::optional<WithPredicate<TypePackId>> MagicPack::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -1274,7 +1353,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionPack(
     return WithPredicate<TypePackId>{arena.addTypePack({packedTable})};
 }
 
-static bool dcrMagicFunctionPack(MagicFunctionCallContext context)
+bool MagicPack::infer(const MagicFunctionCallContext& context)
 {
 
     TypeArena* arena = context.solver->arena;
@@ -1314,6 +1393,162 @@ static bool dcrMagicFunctionPack(MagicFunctionCallContext context)
     return true;
 }
 
+std::optional<WithPredicate<TypePackId>> MagicClone::handleOldSolver(
+    TypeChecker& typechecker,
+    const ScopePtr& scope,
+    const AstExprCall& expr,
+    WithPredicate<TypePackId> withPredicate
+)
+{
+    LUAU_ASSERT(FFlag::LuauTableCloneClonesType3);
+
+    auto [paramPack, _predicates] = withPredicate;
+
+    TypeArena& arena = typechecker.currentModule->internalTypes;
+
+    const auto& [paramTypes, paramTail] = flatten(paramPack);
+    if (paramTypes.empty() || expr.args.size == 0)
+    {
+        typechecker.reportError(expr.argLocation, CountMismatch{1, std::nullopt, 0});
+        return std::nullopt;
+    }
+
+    TypeId inputType = follow(paramTypes[0]);
+
+    if (!get<TableType>(inputType))
+        return std::nullopt;
+
+    CloneState cloneState{typechecker.builtinTypes};
+    TypeId resultType = shallowClone(inputType, arena, cloneState);
+
+    TypePackId clonedTypePack = arena.addTypePack({resultType});
+    return WithPredicate<TypePackId>{clonedTypePack};
+}
+
+bool MagicClone::infer(const MagicFunctionCallContext& context)
+{
+    LUAU_ASSERT(FFlag::LuauTableCloneClonesType3);
+
+    TypeArena* arena = context.solver->arena;
+
+    const auto& [paramTypes, paramTail] = flatten(context.arguments);
+    if (paramTypes.empty() || context.callSite->args.size == 0)
+    {
+        context.solver->reportError(CountMismatch{1, std::nullopt, 0}, context.callSite->argLocation);
+        return false;
+    }
+
+    TypeId inputType = follow(paramTypes[0]);
+
+    if (!get<TableType>(inputType))
+        return false;
+
+    CloneState cloneState{context.solver->builtinTypes};
+    TypeId resultType = shallowClone(inputType, *arena, cloneState, /* ignorePersistent */ FFlag::LuauFreezeIgnorePersistent);
+
+    if (auto tableType = getMutable<TableType>(resultType))
+    {
+        tableType->scope = context.constraint->scope.get();
+    }
+
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+        trackInteriorFreeType(context.constraint->scope.get(), resultType);
+
+    TypePackId clonedTypePack = arena->addTypePack({resultType});
+    asMutable(context.result)->ty.emplace<BoundTypePack>(clonedTypePack);
+
+    return true;
+}
+
+static std::optional<TypeId> freezeTable(TypeId inputType, const MagicFunctionCallContext& context)
+{
+    TypeArena* arena = context.solver->arena;
+    if (FFlag::LuauFollowTableFreeze)
+        inputType = follow(inputType);
+    if (auto mt = get<MetatableType>(inputType))
+    {
+        std::optional<TypeId> frozenTable = freezeTable(mt->table, context);
+
+        if (!frozenTable)
+            return std::nullopt;
+
+        TypeId resultType = arena->addType(MetatableType{*frozenTable, mt->metatable, mt->syntheticName});
+
+        return resultType;
+    }
+
+    if (get<TableType>(inputType))
+    {
+        // 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);
+        auto tableTy = getMutable<TableType>(resultType);
+        // `clone` should not break this.
+        LUAU_ASSERT(tableTy);
+        tableTy->state = TableState::Sealed;
+
+        // We'll mutate the table to make every property type read-only.
+        for (auto iter = tableTy->props.begin(); iter != tableTy->props.end();)
+        {
+            if (iter->second.isWriteOnly())
+                iter = tableTy->props.erase(iter);
+            else
+            {
+                iter->second.writeTy = std::nullopt;
+                iter++;
+            }
+        }
+
+        return resultType;
+    }
+
+    context.solver->reportError(TypeMismatch{context.solver->builtinTypes->tableType, inputType}, context.callSite->argLocation);
+    return std::nullopt;
+}
+
+std::optional<WithPredicate<TypePackId>> MagicFreeze::
+    handleOldSolver(struct TypeChecker&, const std::shared_ptr<struct Scope>&, const class AstExprCall&, WithPredicate<TypePackId>)
+{
+    return std::nullopt;
+}
+
+bool MagicFreeze::infer(const MagicFunctionCallContext& context)
+{
+    TypeArena* arena = context.solver->arena;
+    const DataFlowGraph* dfg = context.solver->dfg.get();
+    Scope* scope = context.constraint->scope.get();
+
+    const auto& [paramTypes, paramTail] = extendTypePack(*arena, context.solver->builtinTypes, context.arguments, 1);
+    if (paramTypes.empty() || context.callSite->args.size == 0)
+    {
+        context.solver->reportError(CountMismatch{1, std::nullopt, 0}, context.callSite->argLocation);
+        return false;
+    }
+
+    TypeId inputType = follow(paramTypes[0]);
+
+    AstExpr* targetExpr = context.callSite->args.data[0];
+    std::optional<DefId> resultDef = dfg->getDefOptional(targetExpr);
+    std::optional<TypeId> resultTy = resultDef ? scope->lookup(*resultDef) : std::nullopt;
+
+    std::optional<TypeId> frozenType = freezeTable(inputType, context);
+
+    if (!frozenType)
+    {
+        if (resultTy)
+            asMutable(*resultTy)->ty.emplace<BoundType>(context.solver->builtinTypes->errorType);
+        asMutable(context.result)->ty.emplace<BoundTypePack>(context.solver->builtinTypes->errorTypePack);
+
+        return true;
+    }
+
+    if (resultTy)
+        asMutable(*resultTy)->ty.emplace<BoundType>(*frozenType);
+    asMutable(context.result)->ty.emplace<BoundTypePack>(arena->addTypePack({*frozenType}));
+
+    return true;
+}
+
 static bool checkRequirePath(TypeChecker& typechecker, AstExpr* expr)
 {
     // require(foo.parent.bar) will technically work, but it depends on legacy goop that
@@ -1336,7 +1571,7 @@ static bool checkRequirePath(TypeChecker& typechecker, AstExpr* expr)
     return good;
 }
 
-static std::optional<WithPredicate<TypePackId>> magicFunctionRequire(
+std::optional<WithPredicate<TypePackId>> MagicRequire::handleOldSolver(
     TypeChecker& typechecker,
     const ScopePtr& scope,
     const AstExprCall& expr,
@@ -1382,7 +1617,7 @@ static bool checkRequirePathDcr(NotNull<ConstraintSolver> solver, AstExpr* expr)
     return good;
 }
 
-static bool dcrMagicFunctionRequire(MagicFunctionCallContext context)
+bool MagicRequire::infer(const MagicFunctionCallContext& context)
 {
     if (context.callSite->args.size != 1)
     {
@@ -1405,4 +1640,52 @@ static bool dcrMagicFunctionRequire(MagicFunctionCallContext context)
     return false;
 }
 
+bool matchSetMetatable(const AstExprCall& call)
+{
+    const char* smt = "setmetatable";
+
+    if (call.args.size != 2)
+        return false;
+
+    const AstExprGlobal* funcAsGlobal = call.func->as<AstExprGlobal>();
+    if (!funcAsGlobal || funcAsGlobal->name != smt)
+        return false;
+
+    return true;
+}
+
+bool matchTableFreeze(const AstExprCall& call)
+{
+    if (call.args.size < 1)
+        return false;
+
+    const AstExprIndexName* index = call.func->as<AstExprIndexName>();
+    if (!index || index->index != "freeze")
+        return false;
+
+    const AstExprGlobal* global = index->expr->as<AstExprGlobal>();
+    if (!global || global->name != "table")
+        return false;
+
+    return true;
+}
+
+bool matchAssert(const AstExprCall& call)
+{
+    if (call.args.size < 1)
+        return false;
+
+    const AstExprGlobal* funcAsGlobal = call.func->as<AstExprGlobal>();
+    if (!funcAsGlobal || funcAsGlobal->name != "assert")
+        return false;
+
+    return true;
+}
+
+bool shouldTypestateForFirstArgument(const AstExprCall& call)
+{
+    // TODO: magic function for setmetatable and assert and then add them
+    return matchTableFreeze(call);
+}
+
 } // namespace Luau

Analysis/src/Clone.cpp

@@ -7,6 +7,7 @@
 #include "Luau/Unifiable.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)
@@ -38,14 +39,26 @@ class TypeCloner
     NotNull<SeenTypes> types;
     NotNull<SeenTypePacks> packs;
 
+    TypeId forceTy = nullptr;
+    TypePackId forceTp = nullptr;
+
     int steps = 0;
 
 public:
-    TypeCloner(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, NotNull<SeenTypes> types, NotNull<SeenTypePacks> packs)
+    TypeCloner(
+        NotNull<TypeArena> arena,
+        NotNull<BuiltinTypes> builtinTypes,
+        NotNull<SeenTypes> types,
+        NotNull<SeenTypePacks> packs,
+        TypeId forceTy,
+        TypePackId forceTp
+    )
         : arena(arena)
         , builtinTypes(builtinTypes)
         , types(types)
         , packs(packs)
+        , forceTy(forceTy)
+        , forceTp(forceTp)
     {
     }
 
@@ -112,7 +125,7 @@ private:
         ty = follow(ty, FollowOption::DisableLazyTypeThunks);
         if (auto it = types->find(ty); it != types->end())
             return it->second;
-        else if (ty->persistent)
+        else if (ty->persistent && (!FFlag::LuauFreezeIgnorePersistent || ty != forceTy))
             return ty;
         return std::nullopt;
     }
@@ -122,7 +135,7 @@ private:
         tp = follow(tp);
         if (auto it = packs->find(tp); it != packs->end())
             return it->second;
-        else if (tp->persistent)
+        else if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || tp != forceTp))
             return tp;
         return std::nullopt;
     }
@@ -140,7 +153,7 @@ private:
         }
     }
 
-private:
+public:
     TypeId shallowClone(TypeId ty)
     {
         // We want to [`Luau::follow`] but without forcing the expansion of [`LazyType`]s.
@@ -148,7 +161,7 @@ private:
 
         if (auto clone = find(ty))
             return *clone;
-        else if (ty->persistent)
+        else if (ty->persistent && (!FFlag::LuauFreezeIgnorePersistent || ty != forceTy))
             return ty;
 
         TypeId target = arena->addType(ty->ty);
@@ -174,7 +187,7 @@ private:
 
         if (auto clone = find(tp))
             return *clone;
-        else if (tp->persistent)
+        else if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || tp != forceTp))
             return tp;
 
         TypePackId target = arena->addTypePack(tp->ty);
@@ -189,6 +202,7 @@ private:
         return target;
     }
 
+private:
     Property shallowClone(const Property& p)
     {
         if (FFlag::LuauSolverV2)
@@ -256,8 +270,7 @@ private:
             LUAU_ASSERT(!"Item holds neither TypeId nor TypePackId when enqueuing its children?");
     }
 
-    // ErrorType and ErrorTypePack is an alias to this type.
+    void cloneChildren(ErrorType* t)
-    void cloneChildren(Unifiable::Error* t)
     {
         // noop.
     }
@@ -359,6 +372,11 @@ private:
         // noop.
     }
 
+    void cloneChildren(NoRefineType* t)
+    {
+        // noop.
+    }
+
     void cloneChildren(UnionType* t)
     {
         for (TypeId& ty : t->options)
@@ -422,6 +440,11 @@ private:
         t->boundTo = shallowClone(t->boundTo);
     }
 
+    void cloneChildren(ErrorTypePack* t)
+    {
+        // noop.
+    }
+
     void cloneChildren(VariadicTypePack* t)
     {
         t->ty = shallowClone(t->ty);
@@ -448,12 +471,46 @@ private:
 
 } // namespace
 
+TypePackId shallowClone(TypePackId tp, TypeArena& dest, CloneState& cloneState, bool ignorePersistent)
+{
+    if (tp->persistent && (!FFlag::LuauFreezeIgnorePersistent || !ignorePersistent))
+        return tp;
+
+    TypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        nullptr,
+        FFlag::LuauFreezeIgnorePersistent && ignorePersistent ? tp : nullptr
+    };
+
+    return cloner.shallowClone(tp);
+}
+
+TypeId shallowClone(TypeId typeId, TypeArena& dest, CloneState& cloneState, bool ignorePersistent)
+{
+    if (typeId->persistent && (!FFlag::LuauFreezeIgnorePersistent || !ignorePersistent))
+        return typeId;
+
+    TypeCloner cloner{
+        NotNull{&dest},
+        cloneState.builtinTypes,
+        NotNull{&cloneState.seenTypes},
+        NotNull{&cloneState.seenTypePacks},
+        FFlag::LuauFreezeIgnorePersistent && ignorePersistent ? typeId : nullptr,
+        nullptr
+    };
+
+    return cloner.shallowClone(typeId);
+}
+
 TypePackId clone(TypePackId tp, TypeArena& dest, CloneState& cloneState)
 {
     if (tp->persistent)
         return tp;
 
-    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}, nullptr, nullptr};
     return cloner.clone(tp);
 }
 
@@ -462,13 +519,13 @@ TypeId clone(TypeId typeId, TypeArena& dest, CloneState& cloneState)
     if (typeId->persistent)
         return typeId;
 
-    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}, nullptr, nullptr};
     return cloner.clone(typeId);
 }
 
 TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState)
 {
-    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}, nullptr, nullptr};
 
     TypeFun copy = typeFun;
 
@@ -493,4 +550,18 @@ TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState)
     return copy;
 }
 
+Binding clone(const Binding& binding, TypeArena& dest, CloneState& cloneState)
+{
+    TypeCloner cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}, nullptr, nullptr};
+
+    Binding b;
+    b.deprecated = binding.deprecated;
+    b.deprecatedSuggestion = binding.deprecatedSuggestion;
+    b.documentationSymbol = binding.documentationSymbol;
+    b.location = binding.location;
+    b.typeId = cloner.clone(binding.typeId);
+
+    return b;
+}
+
 } // namespace Luau

Analysis/src/Constraint.cpp

@@ -3,6 +3,8 @@
 #include "Luau/Constraint.h"
 #include "Luau/VisitType.h"
 
+LUAU_FASTFLAG(DebugLuauGreedyGeneralization)
+
 namespace Luau
 {
 
@@ -46,6 +48,20 @@ struct ReferenceCountInitializer : TypeOnceVisitor
         // ClassTypes never contain free types.
         return false;
     }
+
+    bool visit(TypeId, const TypeFunctionInstanceType&) override
+    {
+        // We do not consider reference counted types that are inside a type
+        // function to be part of the reachable reference counted types.
+        // Otherwise, code can be constructed in just the right way such
+        // that two type functions both claim to mutate a free type, which
+        // prevents either type function from trying to generalize it, so
+        // we potentially get stuck.
+        //
+        // The default behavior here is `true` for "visit the child types"
+        // of this type, hence:
+        return false;
+    }
 };
 
 bool isReferenceCountedType(const TypeId typ)
@@ -97,6 +113,11 @@ DenseHashSet<TypeId> Constraint::getMaybeMutatedFreeTypes() const
     {
         rci.traverse(fchc->argsPack);
     }
+    else if (auto fcc = get<FunctionCallConstraint>(*this); fcc && FFlag::DebugLuauGreedyGeneralization)
+    {
+        rci.traverse(fcc->fn);
+        rci.traverse(fcc->argsPack);
+    }
     else if (auto ptc = get<PrimitiveTypeConstraint>(*this))
     {
         rci.traverse(ptc->freeType);
@@ -104,7 +125,8 @@ DenseHashSet<TypeId> Constraint::getMaybeMutatedFreeTypes() const
     else if (auto hpc = get<HasPropConstraint>(*this))
     {
         rci.traverse(hpc->resultType);
-        // `HasPropConstraints` should not mutate `subjectType`.
+        if (FFlag::DebugLuauGreedyGeneralization)
+            rci.traverse(hpc->subjectType);
     }
     else if (auto hic = get<HasIndexerConstraint>(*this))
     {
@@ -132,6 +154,10 @@ DenseHashSet<TypeId> Constraint::getMaybeMutatedFreeTypes() const
     {
         rci.traverse(rpc->tp);
     }
+    else if (auto tcc = get<TableCheckConstraint>(*this))
+    {
+        rci.traverse(tcc->exprType);
+    }
 
     return types;
 }

Analysis/src/Differ.cpp

@@ -718,7 +718,7 @@ static DifferResult diffUsingEnv(DifferEnvironment& env, TypeId left, TypeId rig
         env.popVisiting();
         return diffRes;
     }
-    if (auto le = get<Luau::Unifiable::Error>(left))
+    if (auto le = get<ErrorType>(left))
     {
         // TODO: return debug-friendly result state
         env.popVisiting();

Analysis/src/EmbeddedBuiltinDefinitions.cpp

@@ -1,102 +1,12 @@
 // 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
 {
 
-static const std::string kBuiltinDefinitionLuaSrcChecked = R"BUILTIN_SRC(
+static const std::string kBuiltinDefinitionBaseSrc = R"BUILTIN_SRC(
-
-declare bit32: {
-    band: @checked (...number) -> number,
-    bor: @checked (...number) -> number,
-    bxor: @checked (...number) -> number,
-    btest: @checked (number, ...number) -> boolean,
-    rrotate: @checked (x: number, disp: number) -> number,
-    lrotate: @checked (x: number, disp: number) -> number,
-    lshift: @checked (x: number, disp: number) -> number,
-    arshift: @checked (x: number, disp: number) -> number,
-    rshift: @checked (x: number, disp: number) -> number,
-    bnot: @checked (x: number) -> number,
-    extract: @checked (n: number, field: number, width: number?) -> number,
-    replace: @checked (n: number, v: number, field: number, width: number?) -> number,
-    countlz: @checked (n: number) -> number,
-    countrz: @checked (n: number) -> number,
-    byteswap: @checked (n: number) -> number,
-}
-
-declare math: {
-    frexp: @checked (n: number) -> (number, number),
-    ldexp: @checked (s: number, e: number) -> number,
-    fmod: @checked (x: number, y: number) -> number,
-    modf: @checked (n: number) -> (number, number),
-    pow: @checked (x: number, y: number) -> number,
-    exp: @checked (n: number) -> number,
-
-    ceil: @checked (n: number) -> number,
-    floor: @checked (n: number) -> number,
-    abs: @checked (n: number) -> number,
-    sqrt: @checked (n: number) -> number,
-
-    log: @checked (n: number, base: number?) -> number,
-    log10: @checked (n: number) -> number,
-
-    rad: @checked (n: number) -> number,
-    deg: @checked (n: number) -> number,
-
-    sin: @checked (n: number) -> number,
-    cos: @checked (n: number) -> number,
-    tan: @checked (n: number) -> number,
-    sinh: @checked (n: number) -> number,
-    cosh: @checked (n: number) -> number,
-    tanh: @checked (n: number) -> number,
-    atan: @checked (n: number) -> number,
-    acos: @checked (n: number) -> number,
-    asin: @checked (n: number) -> number,
-    atan2: @checked (y: number, x: number) -> number,
-
-    min: @checked (number, ...number) -> number,
-    max: @checked (number, ...number) -> number,
-
-    pi: number,
-    huge: number,
-
-    randomseed: @checked (seed: number) -> (),
-    random: @checked (number?, number?) -> number,
-
-    sign: @checked (n: number) -> number,
-    clamp: @checked (n: number, min: number, max: number) -> number,
-    noise: @checked (x: number, y: number?, z: number?) -> number,
-    round: @checked (n: number) -> number,
-}
-
-type DateTypeArg = {
-    year: number,
-    month: number,
-    day: number,
-    hour: number?,
-    min: number?,
-    sec: number?,
-    isdst: boolean?,
-}
-
-type DateTypeResult = {
-    year: number,
-    month: number,
-    wday: number,
-    yday: number,
-    day: number,
-    hour: number,
-    min: number,
-    sec: number,
-    isdst: boolean,
-}
-
-declare os: {
-    time: (time: DateTypeArg?) -> number,
-    date: ((formatString: "*t" | "!*t", time: number?) -> DateTypeResult) & ((formatString: string?, time: number?) -> string),
-    difftime: (t2: DateTypeResult | number, t1: DateTypeResult | number) -> number,
-    clock: () -> number,
-}
 
 @checked declare function require(target: any): any
 
@@ -144,6 +54,119 @@ declare function loadstring<A...>(src: string, chunkname: string?): (((A...) ->
 
 @checked declare function newproxy(mt: boolean?): any
 
+-- Cannot use `typeof` here because it will produce a polytype when we expect a monotype.
+declare function unpack<V>(tab: {V}, i: number?, j: number?): ...V
+
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionBit32Src = R"BUILTIN_SRC(
+
+declare bit32: {
+    band: @checked (...number) -> number,
+    bor: @checked (...number) -> number,
+    bxor: @checked (...number) -> number,
+    btest: @checked (number, ...number) -> boolean,
+    rrotate: @checked (x: number, disp: number) -> number,
+    lrotate: @checked (x: number, disp: number) -> number,
+    lshift: @checked (x: number, disp: number) -> number,
+    arshift: @checked (x: number, disp: number) -> number,
+    rshift: @checked (x: number, disp: number) -> number,
+    bnot: @checked (x: number) -> number,
+    extract: @checked (n: number, field: number, width: number?) -> number,
+    replace: @checked (n: number, v: number, field: number, width: number?) -> number,
+    countlz: @checked (n: number) -> number,
+    countrz: @checked (n: number) -> number,
+    byteswap: @checked (n: number) -> number,
+}
+
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionMathSrc = R"BUILTIN_SRC(
+
+declare math: {
+    frexp: @checked (n: number) -> (number, number),
+    ldexp: @checked (s: number, e: number) -> number,
+    fmod: @checked (x: number, y: number) -> number,
+    modf: @checked (n: number) -> (number, number),
+    pow: @checked (x: number, y: number) -> number,
+    exp: @checked (n: number) -> number,
+
+    ceil: @checked (n: number) -> number,
+    floor: @checked (n: number) -> number,
+    abs: @checked (n: number) -> number,
+    sqrt: @checked (n: number) -> number,
+
+    log: @checked (n: number, base: number?) -> number,
+    log10: @checked (n: number) -> number,
+
+    rad: @checked (n: number) -> number,
+    deg: @checked (n: number) -> number,
+
+    sin: @checked (n: number) -> number,
+    cos: @checked (n: number) -> number,
+    tan: @checked (n: number) -> number,
+    sinh: @checked (n: number) -> number,
+    cosh: @checked (n: number) -> number,
+    tanh: @checked (n: number) -> number,
+    atan: @checked (n: number) -> number,
+    acos: @checked (n: number) -> number,
+    asin: @checked (n: number) -> number,
+    atan2: @checked (y: number, x: number) -> number,
+
+    min: @checked (number, ...number) -> number,
+    max: @checked (number, ...number) -> number,
+
+    pi: number,
+    huge: number,
+
+    randomseed: @checked (seed: number) -> (),
+    random: @checked (number?, number?) -> number,
+
+    sign: @checked (n: number) -> number,
+    clamp: @checked (n: number, min: number, max: number) -> number,
+    noise: @checked (x: number, y: number?, z: number?) -> number,
+    round: @checked (n: number) -> number,
+    map: @checked (x: number, inmin: number, inmax: number, outmin: number, outmax: number) -> number,
+    lerp: @checked (a: number, b: number, t: number) -> number,
+}
+
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionOsSrc = R"BUILTIN_SRC(
+
+type DateTypeArg = {
+    year: number,
+    month: number,
+    day: number,
+    hour: number?,
+    min: number?,
+    sec: number?,
+    isdst: boolean?,
+}
+
+type DateTypeResult = {
+    year: number,
+    month: number,
+    wday: number,
+    yday: number,
+    day: number,
+    hour: number,
+    min: number,
+    sec: number,
+    isdst: boolean,
+}
+
+declare os: {
+    time: (time: DateTypeArg?) -> number,
+    date: ((formatString: "*t" | "!*t", time: number?) -> DateTypeResult) & ((formatString: string?, time: number?) -> string),
+    difftime: (t2: DateTypeResult | number, t1: DateTypeResult | number) -> number,
+    clock: () -> number,
+}
+
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionCoroutineSrc = R"BUILTIN_SRC(
+
 declare coroutine: {
     create: <A..., R...>(f: (A...) -> R...) -> thread,
     resume: <A..., R...>(co: thread, A...) -> (boolean, R...),
@@ -155,6 +178,10 @@ declare coroutine: {
     close: @checked (co: thread) -> (boolean, any)
 }
 
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionTableSrc = R"BUILTIN_SRC(
+
 declare table: {
     concat: <V>(t: {V}, sep: string?, i: number?, j: number?) -> string,
     insert: (<V>(t: {V}, value: V) -> ()) & (<V>(t: {V}, pos: number, value: V) -> ()),
@@ -177,11 +204,28 @@ declare table: {
     isfrozen: <K, V>(t: {[K]: V}) -> boolean,
 }
 
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionDebugSrc = R"BUILTIN_SRC(
+
+declare debug: {
+    info: ((thread: thread, level: number, options: string) -> ...any) & ((level: number, options: string) -> ...any) & (<A..., R1...>(func: (A...) -> R1..., options: string) -> ...any),
+    traceback: ((message: string?, level: number?) -> string) & ((thread: thread, message: string?, level: number?) -> string),
+}
+
+)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: {
     char: @checked (...number) -> string,
     charpattern: string,
@@ -191,10 +235,9 @@ declare utf8: {
     offset: @checked (s: string, n: number?, i: number?) -> number,
 }
 
--- Cannot use `typeof` here because it will produce a polytype when we expect a monotype.
+)BUILTIN_SRC";
-declare function unpack<V>(tab: {V}, i: number?, j: number?): ...V
-
 
+static const std::string kBuiltinDefinitionBufferSrc = R"BUILTIN_SRC(
 --- Buffer API
 declare buffer: {
     create: @checked (size: number) -> buffer,
@@ -221,13 +264,56 @@ declare buffer: {
     writef64: @checked (b: buffer, offset: number, value: number) -> (),
     readstring: @checked (b: buffer, offset: number, count: number) -> string,
     writestring: @checked (b: buffer, offset: number, value: string, count: number?) -> (),
+    readbits: @checked (b: buffer, bitOffset: number, bitCount: number) -> number,
+    writebits: @checked (b: buffer, bitOffset: number, bitCount: number, value: number) -> (),
+}
+
+)BUILTIN_SRC";
+
+static const std::string kBuiltinDefinitionVectorSrc = R"BUILTIN_SRC(
+
+-- While vector would have been better represented as a built-in primitive type, type solver class handling covers most of the properties
+declare class vector
+    x: number
+    y: number
+    z: number
+end
+
+declare vector: {
+    create: @checked (x: number, y: number, z: number?) -> vector,
+    magnitude: @checked (vec: vector) -> number,
+    normalize: @checked (vec: vector) -> vector,
+    cross: @checked (vec1: vector, vec2: vector) -> vector,
+    dot: @checked (vec1: vector, vec2: vector) -> number,
+    angle: @checked (vec1: vector, vec2: vector, axis: vector?) -> number,
+    floor: @checked (vec: vector) -> vector,
+    ceil: @checked (vec: vector) -> vector,
+    abs: @checked (vec: vector) -> vector,
+    sign: @checked (vec: vector) -> vector,
+    clamp: @checked (vec: vector, min: vector, max: vector) -> vector,
+    max: @checked (vector, ...vector) -> vector,
+    min: @checked (vector, ...vector) -> vector,
+
+    zero: vector,
+    one: vector,
 }
 
 )BUILTIN_SRC";
 
 std::string getBuiltinDefinitionSource()
 {
-    std::string result = kBuiltinDefinitionLuaSrcChecked;
+    std::string result = kBuiltinDefinitionBaseSrc;
+
+    result += kBuiltinDefinitionBit32Src;
+    result += kBuiltinDefinitionMathSrc;
+    result += kBuiltinDefinitionOsSrc;
+    result += kBuiltinDefinitionCoroutineSrc;
+    result += kBuiltinDefinitionTableSrc;
+    result += FFlag::LuauDebugInfoDefn ? kBuiltinDefinitionDebugSrc : kBuiltinDefinitionDebugSrc_DEPRECATED;
+    result += kBuiltinDefinitionUtf8Src;
+    result += kBuiltinDefinitionBufferSrc;
+    result += kBuiltinDefinitionVectorSrc;
+
     return result;
 }
 

Analysis/src/Error.cpp

@@ -18,8 +18,6 @@
 
 LUAU_FASTINTVARIABLE(LuauIndentTypeMismatchMaxTypeLength, 10)
 
-LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauImproveNonFunctionCallError, false)
-
 static std::string wrongNumberOfArgsString(
     size_t expectedCount,
     std::optional<size_t> maximumCount,
@@ -407,8 +405,6 @@ struct ErrorConverter
     }
 
     std::string operator()(const Luau::CannotCallNonFunction& e) const
-    {
-        if (DFFlag::LuauImproveNonFunctionCallError)
     {
         if (auto unionTy = get<UnionType>(follow(e.ty)))
         {
@@ -435,9 +431,6 @@ struct ErrorConverter
 
         return "Cannot call a value of type " + toString(e.ty);
     }
-
-        return "Cannot call non-function " + toString(e.ty);
-    }
     std::string operator()(const Luau::ExtraInformation& e) const
     {
         return e.message;
@@ -793,6 +786,11 @@ struct ErrorConverter
         return "Encountered an unexpected type pack in subtyping: " + toString(e.tp);
     }
 
+    std::string operator()(const UserDefinedTypeFunctionError& e) const
+    {
+        return e.message;
+    }
+
     std::string operator()(const CannotAssignToNever& e) const
     {
         std::string result = "Cannot assign a value of type " + toString(e.rhsType) + " to a field of type never";
@@ -1175,6 +1173,11 @@ bool UnexpectedTypePackInSubtyping::operator==(const UnexpectedTypePackInSubtypi
     return tp == rhs.tp;
 }
 
+bool UserDefinedTypeFunctionError::operator==(const UserDefinedTypeFunctionError& rhs) const
+{
+    return message == rhs.message;
+}
+
 bool CannotAssignToNever::operator==(const CannotAssignToNever& rhs) const
 {
     if (cause.size() != rhs.cause.size())
@@ -1384,6 +1387,9 @@ void copyError(T& e, TypeArena& destArena, CloneState& cloneState)
         e.ty = clone(e.ty);
     else if constexpr (std::is_same_v<T, UnexpectedTypePackInSubtyping>)
         e.tp = clone(e.tp);
+    else if constexpr (std::is_same_v<T, UserDefinedTypeFunctionError>)
+    {
+    }
     else if constexpr (std::is_same_v<T, CannotAssignToNever>)
     {
         e.rhsType = clone(e.rhsType);

Analysis/src/FragmentAutocomplete.cpp

@@ -0,0 +1,708 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/FragmentAutocomplete.h"
+
+#include "Luau/Ast.h"
+#include "Luau/AstQuery.h"
+#include "Luau/Autocomplete.h"
+#include "Luau/Common.h"
+#include "Luau/EqSatSimplification.h"
+#include "Luau/ModuleResolver.h"
+#include "Luau/Parser.h"
+#include "Luau/ParseOptions.h"
+#include "Luau/Module.h"
+#include "Luau/TimeTrace.h"
+#include "Luau/UnifierSharedState.h"
+#include "Luau/TypeFunction.h"
+#include "Luau/DataFlowGraph.h"
+#include "Luau/ConstraintGenerator.h"
+#include "Luau/ConstraintSolver.h"
+#include "Luau/Frontend.h"
+#include "Luau/Parser.h"
+#include "Luau/ParseOptions.h"
+#include "Luau/Module.h"
+#include "Luau/Clone.h"
+#include "AutocompleteCore.h"
+
+LUAU_FASTINT(LuauTypeInferRecursionLimit);
+LUAU_FASTINT(LuauTypeInferIterationLimit);
+LUAU_FASTINT(LuauTarjanChildLimit)
+LUAU_FASTFLAG(LuauAutocompleteRefactorsForIncrementalAutocomplete)
+
+LUAU_FASTFLAGVARIABLE(LuauIncrementalAutocompleteBugfixes)
+LUAU_FASTFLAGVARIABLE(LuauMixedModeDefFinderTraversesTypeOf)
+LUAU_FASTFLAG(LuauBetterReverseDependencyTracking)
+LUAU_FASTFLAGVARIABLE(LuauCloneIncrementalModule)
+LUAU_FASTFLAGVARIABLE(LogFragmentsFromAutocomplete)
+namespace
+{
+template<typename T>
+void copyModuleVec(std::vector<T>& result, const std::vector<T>& input)
+{
+    result.insert(result.end(), input.begin(), input.end());
+}
+
+template<typename K, typename V>
+void copyModuleMap(Luau::DenseHashMap<K, V>& result, const Luau::DenseHashMap<K, V>& input)
+{
+    for (auto [k, v] : input)
+        result[k] = v;
+}
+
+} // namespace
+
+namespace Luau
+{
+
+template<typename K, typename V>
+void cloneModuleMap(TypeArena& destArena, CloneState& cloneState, const Luau::DenseHashMap<K, V>& source, Luau::DenseHashMap<K, V>& dest)
+{
+    for (auto [k, v] : source)
+    {
+        dest[k] = Luau::clone(v, destArena, cloneState);
+    }
+}
+
+struct MixedModeIncrementalTCDefFinder : public AstVisitor
+{
+    bool visit(AstExprLocal* local) override
+    {
+        referencedLocalDefs.emplace_back(local->local, local);
+        return true;
+    }
+
+    bool visit(AstTypeTypeof* node) override
+    {
+        // We need to traverse typeof expressions because they may refer to locals that we need
+        // to populate the local environment for fragment typechecking. For example, `typeof(m)`
+        // requires that we find the local/global `m` and place it in the environment.
+        // The default behaviour here is to return false, and have individual visitors override
+        // the specific behaviour they need.
+        return FFlag::LuauMixedModeDefFinderTraversesTypeOf;
+    }
+
+    // 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<std::pair<AstLocal*, AstExpr*>> referencedLocalDefs;
+};
+
+void cloneAndSquashScopes(
+    CloneState& cloneState,
+    const Scope* staleScope,
+    const ModulePtr& staleModule,
+    NotNull<TypeArena> destArena,
+    NotNull<DataFlowGraph> dfg,
+    AstStatBlock* program,
+    Scope* destScope
+)
+{
+    LUAU_TIMETRACE_SCOPE("Luau::cloneAndSquashScopes", "FragmentAutocomplete");
+    std::vector<const Scope*> scopes;
+    for (const Scope* current = staleScope; current; current = current->parent.get())
+    {
+        scopes.emplace_back(current);
+    }
+
+    // in reverse order (we need to clone the parents and override defs as we go down the list)
+    for (auto it = scopes.rbegin(); it != scopes.rend(); ++it)
+    {
+        const Scope* curr = *it;
+        // Clone the lvalue types
+        for (const auto& [def, ty] : curr->lvalueTypes)
+            destScope->lvalueTypes[def] = Luau::clone(ty, *destArena, cloneState);
+        // Clone the rvalueRefinements
+        for (const auto& [def, ty] : curr->rvalueRefinements)
+            destScope->rvalueRefinements[def] = Luau::clone(ty, *destArena, cloneState);
+        for (const auto& [n, m] : curr->importedTypeBindings)
+        {
+            std::unordered_map<Name, TypeFun> importedBindingTypes;
+            for (const auto& [v, tf] : m)
+                importedBindingTypes[v] = Luau::clone(tf, *destArena, cloneState);
+            destScope->importedTypeBindings[n] = m;
+        }
+
+        // Finally, clone up the bindings
+        for (const auto& [s, b] : curr->bindings)
+        {
+            destScope->bindings[s] = Luau::clone(b, *destArena, cloneState);
+        }
+    }
+
+    // The above code associates defs with TypeId's in the scope
+    // so that lookup to locals will succeed.
+    MixedModeIncrementalTCDefFinder finder;
+    program->visit(&finder);
+    std::vector<std::pair<AstLocal*, AstExpr*>> locals = std::move(finder.referencedLocalDefs);
+    for (auto [loc, expr] : locals)
+    {
+        if (std::optional<Binding> binding = staleScope->linearSearchForBinding(loc->name.value, true))
+        {
+            destScope->lvalueTypes[dfg->getDef(expr)] = Luau::clone(binding->typeId, *destArena, cloneState);
+        }
+    }
+    return;
+}
+
+static FrontendModuleResolver& getModuleResolver(Frontend& frontend, std::optional<FrontendOptions> options)
+{
+    if (FFlag::LuauSolverV2 || !options)
+        return frontend.moduleResolver;
+
+    return options->forAutocomplete ? frontend.moduleResolverForAutocomplete : frontend.moduleResolver;
+}
+
+FragmentAutocompleteAncestryResult findAncestryForFragmentParse(AstStatBlock* root, const Position& cursorPos)
+{
+    std::vector<AstNode*> ancestry = findAncestryAtPositionForAutocomplete(root, cursorPos);
+    // Should always contain the root AstStat
+    LUAU_ASSERT(ancestry.size() >= 1);
+    DenseHashMap<AstName, AstLocal*> localMap{AstName()};
+    std::vector<AstLocal*> localStack;
+    AstStat* nearestStatement = nullptr;
+    for (AstNode* node : ancestry)
+    {
+        if (auto block = node->as<AstStatBlock>())
+        {
+            for (auto stat : block->body)
+            {
+                if (stat->location.begin <= cursorPos)
+                    nearestStatement = stat;
+                if (stat->location.begin < cursorPos && stat->location.begin.line < cursorPos.line)
+                {
+                    // This statement precedes the current one
+                    if (auto loc = stat->as<AstStatLocal>())
+                    {
+                        for (auto v : loc->vars)
+                        {
+                            localStack.push_back(v);
+                            localMap[v->name] = v;
+                        }
+                    }
+                    else if (auto locFun = stat->as<AstStatLocalFunction>())
+                    {
+                        localStack.push_back(locFun->name);
+                        localMap[locFun->name->name] = locFun->name;
+                        if (locFun->location.contains(cursorPos))
+                        {
+                            for (AstLocal* loc : locFun->func->args)
+                            {
+                                localStack.push_back(loc);
+                                localMap[loc->name] = loc;
+                            }
+                        }
+                    }
+                    else if (auto globFun = stat->as<AstStatFunction>())
+                    {
+                        if (globFun->location.contains(cursorPos))
+                        {
+                            for (AstLocal* loc : globFun->func->args)
+                            {
+                                localStack.push_back(loc);
+                                localMap[loc->name] = loc;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    if (!nearestStatement)
+        nearestStatement = ancestry[0]->asStat();
+    LUAU_ASSERT(nearestStatement);
+    return {std::move(localMap), std::move(localStack), std::move(ancestry), std::move(nearestStatement)};
+}
+
+/**
+ * Get document offsets is a function that takes a source text document as well as a start position and end position(line, column) in that
+ * document and attempts to get the concrete text between those points. It returns a pair of:
+ * - start offset that represents an index in the source `char*` corresponding to startPos
+ * - length, that represents how many more bytes to read to get to endPos.
+ * Example - your document is "foo bar baz" and getDocumentOffsets is passed (0, 4), (0, 8). This function returns the pair {3, 5}
+ * which corresponds to the string " bar "
+ */
+std::pair<size_t, size_t> getDocumentOffsets(const std::string_view& src, const Position& startPos, const Position& endPos)
+{
+    size_t lineCount = 0;
+    size_t colCount = 0;
+
+    size_t docOffset = 0;
+    size_t startOffset = 0;
+    size_t endOffset = 0;
+    bool foundStart = false;
+    bool foundEnd = false;
+
+    for (char c : src)
+    {
+        if (foundStart && foundEnd)
+            break;
+
+        if (startPos.line == lineCount && startPos.column == colCount)
+        {
+            foundStart = true;
+            startOffset = docOffset;
+        }
+
+        if (endPos.line == lineCount && endPos.column == colCount)
+        {
+            endOffset = docOffset;
+            while (endOffset < src.size() && src[endOffset] != '\n')
+                endOffset++;
+            foundEnd = true;
+        }
+
+        // We put a cursor position that extends beyond the extents of the current line
+        if (foundStart && !foundEnd && (lineCount > endPos.line))
+        {
+            foundEnd = true;
+            endOffset = docOffset - 1;
+        }
+
+        if (c == '\n')
+        {
+            lineCount++;
+            colCount = 0;
+        }
+        else
+        {
+            colCount++;
+        }
+        docOffset++;
+    }
+
+    if (foundStart && !foundEnd)
+        endOffset = src.length();
+
+    size_t min = std::min(startOffset, endOffset);
+    size_t len = std::max(startOffset, endOffset) - min;
+    return {min, len};
+}
+
+ScopePtr findClosestScope(const ModulePtr& module, const AstStat* nearestStatement)
+{
+    LUAU_ASSERT(module->hasModuleScope());
+
+    ScopePtr closest = module->getModuleScope();
+
+    // find the scope the nearest statement belonged to.
+    for (auto [loc, sc] : module->scopes)
+    {
+        if (loc.encloses(nearestStatement->location) && closest->location.begin <= loc.begin)
+            closest = sc;
+    }
+
+    return closest;
+}
+
+std::optional<FragmentParseResult> parseFragment(
+    const SourceModule& srcModule,
+    std::string_view src,
+    const Position& cursorPos,
+    std::optional<Position> fragmentEndPosition
+)
+{
+    FragmentAutocompleteAncestryResult result = findAncestryForFragmentParse(srcModule.root, cursorPos);
+    AstStat* nearestStatement = result.nearestStatement;
+
+    const Location& rootSpan = srcModule.root->location;
+    // Did we append vs did we insert inline
+    bool appended = cursorPos >= rootSpan.end;
+    // statement spans multiple lines
+    bool multiline = nearestStatement->location.begin.line != nearestStatement->location.end.line;
+
+    const Position endPos = fragmentEndPosition.value_or(cursorPos);
+
+    // We start by re-parsing everything (we'll refine this as we go)
+    Position startPos = srcModule.root->location.begin;
+
+    // If we added to the end of the sourceModule, use the end of the nearest location
+    if (appended && multiline)
+        startPos = nearestStatement->location.end;
+    // Statement spans one line && cursorPos is either on the same line or after
+    else if (!multiline && cursorPos.line >= nearestStatement->location.end.line)
+        startPos = nearestStatement->location.begin;
+    else if (multiline && nearestStatement->location.end.line < cursorPos.line)
+        startPos = nearestStatement->location.end;
+    else
+        startPos = nearestStatement->location.begin;
+
+    auto [offsetStart, parseLength] = getDocumentOffsets(src, startPos, endPos);
+    const char* srcStart = src.data() + offsetStart;
+    std::string_view dbg = src.substr(offsetStart, parseLength);
+    const std::shared_ptr<AstNameTable>& nameTbl = srcModule.names;
+    FragmentParseResult fragmentResult;
+    fragmentResult.fragmentToParse = std::string(dbg.data(), parseLength);
+    // For the duration of the incremental parse, we want to allow the name table to re-use duplicate names
+    if (FFlag::LogFragmentsFromAutocomplete)
+        logLuau(dbg);
+
+    ParseOptions opts;
+    opts.allowDeclarationSyntax = false;
+    opts.captureComments = true;
+    opts.parseFragment = FragmentParseResumeSettings{std::move(result.localMap), std::move(result.localStack), startPos};
+    ParseResult p = Luau::Parser::parse(srcStart, parseLength, *nameTbl, *fragmentResult.alloc.get(), opts);
+    // This means we threw a ParseError and we should decline to offer autocomplete here.
+    if (p.root == nullptr)
+        return std::nullopt;
+
+    std::vector<AstNode*> fabricatedAncestry = std::move(result.ancestry);
+
+    // Get the ancestry for the fragment at the offset cursor position.
+    // Consumers have the option to request with fragment end position, so we cannot just use the end position of our parse result as the
+    // cursor position. Instead, use the cursor position calculated as an offset from our start position.
+    std::vector<AstNode*> fragmentAncestry = findAncestryAtPositionForAutocomplete(p.root, cursorPos);
+    fabricatedAncestry.insert(fabricatedAncestry.end(), fragmentAncestry.begin(), fragmentAncestry.end());
+    if (nearestStatement == nullptr)
+        nearestStatement = p.root;
+    fragmentResult.root = std::move(p.root);
+    fragmentResult.ancestry = std::move(fabricatedAncestry);
+    fragmentResult.nearestStatement = nearestStatement;
+    fragmentResult.commentLocations = std::move(p.commentLocations);
+    return fragmentResult;
+}
+
+ModulePtr cloneModule(CloneState& cloneState, const ModulePtr& source, std::unique_ptr<Allocator> alloc)
+{
+    LUAU_TIMETRACE_SCOPE("Luau::cloneModule", "FragmentAutocomplete");
+    freeze(source->internalTypes);
+    freeze(source->interfaceTypes);
+    ModulePtr incremental = std::make_shared<Module>();
+    incremental->name = source->name;
+    incremental->humanReadableName = source->humanReadableName;
+    incremental->allocator = std::move(alloc);
+    //  Clone types
+    cloneModuleMap(incremental->internalTypes, cloneState, source->astTypes, incremental->astTypes);
+    cloneModuleMap(incremental->internalTypes, cloneState, source->astTypePacks, incremental->astTypePacks);
+    cloneModuleMap(incremental->internalTypes, cloneState, source->astExpectedTypes, incremental->astExpectedTypes);
+
+    cloneModuleMap(incremental->internalTypes, cloneState, source->astOverloadResolvedTypes, incremental->astOverloadResolvedTypes);
+
+    cloneModuleMap(incremental->internalTypes, cloneState, source->astForInNextTypes, incremental->astForInNextTypes);
+
+    copyModuleMap(incremental->astScopes, source->astScopes);
+
+    return incremental;
+}
+
+ModulePtr copyModule(const ModulePtr& result, std::unique_ptr<Allocator> alloc)
+{
+    ModulePtr incrementalModule = std::make_shared<Module>();
+    incrementalModule->name = result->name;
+    incrementalModule->humanReadableName = "Incremental$" + result->humanReadableName;
+    incrementalModule->internalTypes.owningModule = incrementalModule.get();
+    incrementalModule->interfaceTypes.owningModule = incrementalModule.get();
+    incrementalModule->allocator = std::move(alloc);
+    // Don't need to keep this alive (it's already on the source module)
+    copyModuleVec(incrementalModule->scopes, result->scopes);
+    copyModuleMap(incrementalModule->astTypes, result->astTypes);
+    copyModuleMap(incrementalModule->astTypePacks, result->astTypePacks);
+    copyModuleMap(incrementalModule->astExpectedTypes, result->astExpectedTypes);
+    // Don't need to clone astOriginalCallTypes
+    copyModuleMap(incrementalModule->astOverloadResolvedTypes, result->astOverloadResolvedTypes);
+    // Don't need to clone astForInNextTypes
+    copyModuleMap(incrementalModule->astForInNextTypes, result->astForInNextTypes);
+    // Don't need to clone astResolvedTypes
+    // Don't need to clone astResolvedTypePacks
+    // Don't need to clone upperBoundContributors
+    copyModuleMap(incrementalModule->astScopes, result->astScopes);
+    // Don't need to clone declared Globals;
+    return incrementalModule;
+}
+
+void mixedModeCompatibility(
+    const ScopePtr& bottomScopeStale,
+    const ScopePtr& myFakeScope,
+    const ModulePtr& stale,
+    NotNull<DataFlowGraph> dfg,
+    AstStatBlock* program
+)
+{
+    // This code does the following
+    // traverse program
+    // look for ast refs for locals
+    // ask for the corresponding defId from dfg
+    // given that defId, and that expression, in the incremental module, map lvalue types from defID to
+
+    MixedModeIncrementalTCDefFinder finder;
+    program->visit(&finder);
+    std::vector<std::pair<AstLocal*, AstExpr*>> locals = std::move(finder.referencedLocalDefs);
+    for (auto [loc, expr] : locals)
+    {
+        if (std::optional<Binding> binding = bottomScopeStale->linearSearchForBinding(loc->name.value, true))
+        {
+            myFakeScope->lvalueTypes[dfg->getDef(expr)] = binding->typeId;
+        }
+    }
+}
+
+FragmentTypeCheckResult typecheckFragment_(
+    Frontend& frontend,
+    AstStatBlock* root,
+    const ModulePtr& stale,
+    const ScopePtr& closestScope,
+    const Position& cursorPos,
+    std::unique_ptr<Allocator> astAllocator,
+    const FrontendOptions& opts
+)
+{
+    LUAU_TIMETRACE_SCOPE("Luau::typecheckFragment_", "FragmentAutocomplete");
+
+    freeze(stale->internalTypes);
+    freeze(stale->interfaceTypes);
+    CloneState cloneState{frontend.builtinTypes};
+    ModulePtr incrementalModule =
+        FFlag::LuauCloneIncrementalModule ? cloneModule(cloneState, stale, std::move(astAllocator)) : copyModule(stale, std::move(astAllocator));
+    incrementalModule->checkedInNewSolver = true;
+    unfreeze(incrementalModule->internalTypes);
+    unfreeze(incrementalModule->interfaceTypes);
+
+    /// Setup typecheck limits
+    TypeCheckLimits limits;
+    if (opts.moduleTimeLimitSec)
+        limits.finishTime = TimeTrace::getClock() + *opts.moduleTimeLimitSec;
+    else
+        limits.finishTime = std::nullopt;
+    limits.cancellationToken = opts.cancellationToken;
+
+    /// Icehandler
+    NotNull<InternalErrorReporter> iceHandler{&frontend.iceHandler};
+    /// Make the shared state for the unifier (recursion + iteration limits)
+    UnifierSharedState unifierState{iceHandler};
+    unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
+    unifierState.counters.iterationLimit = limits.unifierIterationLimit.value_or(FInt::LuauTypeInferIterationLimit);
+
+    /// Initialize the normalizer
+    Normalizer normalizer{&incrementalModule->internalTypes, frontend.builtinTypes, NotNull{&unifierState}};
+
+    /// User defined type functions runtime
+    TypeFunctionRuntime typeFunctionRuntime(iceHandler, NotNull{&limits});
+
+    /// Create a DataFlowGraph just for the surrounding context
+    DataFlowGraph dfg = DataFlowGraphBuilder::build(root, NotNull{&incrementalModule->defArena}, NotNull{&incrementalModule->keyArena}, iceHandler);
+
+    SimplifierPtr simplifier = newSimplifier(NotNull{&incrementalModule->internalTypes}, frontend.builtinTypes);
+
+    FrontendModuleResolver& resolver = getModuleResolver(frontend, opts);
+
+    /// Contraint Generator
+    ConstraintGenerator cg{
+        incrementalModule,
+        NotNull{&normalizer},
+        NotNull{simplifier.get()},
+        NotNull{&typeFunctionRuntime},
+        NotNull{&resolver},
+        frontend.builtinTypes,
+        iceHandler,
+        stale->getModuleScope(),
+        nullptr,
+        nullptr,
+        NotNull{&dfg},
+        {}
+    };
+    std::shared_ptr<Scope> freshChildOfNearestScope = nullptr;
+    if (FFlag::LuauCloneIncrementalModule)
+    {
+        freshChildOfNearestScope = std::make_shared<Scope>(closestScope);
+        incrementalModule->scopes.emplace_back(root->location, freshChildOfNearestScope);
+        cg.rootScope = freshChildOfNearestScope.get();
+
+        cloneAndSquashScopes(
+            cloneState, closestScope.get(), stale, NotNull{&incrementalModule->internalTypes}, NotNull{&dfg}, root, freshChildOfNearestScope.get()
+        );
+        cg.visitFragmentRoot(freshChildOfNearestScope, root);
+    }
+    else
+    {
+        // Any additions to the scope must occur in a fresh scope
+        cg.rootScope = stale->getModuleScope().get();
+        freshChildOfNearestScope = std::make_shared<Scope>(closestScope);
+        incrementalModule->scopes.emplace_back(root->location, freshChildOfNearestScope);
+        mixedModeCompatibility(closestScope, freshChildOfNearestScope, stale, NotNull{&dfg}, root);
+        // closest Scope -> children = { ...., freshChildOfNearestScope}
+        // We need to trim nearestChild from the scope hierarcy
+        closestScope->children.emplace_back(freshChildOfNearestScope.get());
+        cg.visitFragmentRoot(freshChildOfNearestScope, root);
+        // Trim nearestChild from the closestScope
+        Scope* back = closestScope->children.back().get();
+        LUAU_ASSERT(back == freshChildOfNearestScope.get());
+        closestScope->children.pop_back();
+    }
+
+    /// Initialize the constraint solver and run it
+    ConstraintSolver cs{
+        NotNull{&normalizer},
+        NotNull{simplifier.get()},
+        NotNull{&typeFunctionRuntime},
+        NotNull(cg.rootScope),
+        borrowConstraints(cg.constraints),
+        NotNull{&cg.scopeToFunction},
+        incrementalModule->name,
+        NotNull{&resolver},
+        {},
+        nullptr,
+        NotNull{&dfg},
+        limits
+    };
+
+    try
+    {
+        cs.run();
+    }
+    catch (const TimeLimitError&)
+    {
+        stale->timeout = true;
+    }
+    catch (const UserCancelError&)
+    {
+        stale->cancelled = true;
+    }
+
+    // In frontend we would forbid internal types
+    // because this is just for autocomplete, we don't actually care
+    // We also don't even need to typecheck - just synthesize types as best as we can
+
+    freeze(incrementalModule->internalTypes);
+    freeze(incrementalModule->interfaceTypes);
+    return {std::move(incrementalModule), std::move(freshChildOfNearestScope)};
+}
+
+
+std::pair<FragmentTypeCheckStatus, FragmentTypeCheckResult> typecheckFragment(
+    Frontend& frontend,
+    const ModuleName& moduleName,
+    const Position& cursorPos,
+    std::optional<FrontendOptions> opts,
+    std::string_view src,
+    std::optional<Position> fragmentEndPosition
+)
+{
+    LUAU_TIMETRACE_SCOPE("Luau::typecheckFragment", "FragmentAutocomplete");
+    LUAU_TIMETRACE_ARGUMENT("name", moduleName.c_str());
+
+    if (FFlag::LuauBetterReverseDependencyTracking)
+    {
+        if (!frontend.allModuleDependenciesValid(moduleName, opts && opts->forAutocomplete))
+            return {FragmentTypeCheckStatus::SkipAutocomplete, {}};
+    }
+
+    const SourceModule* sourceModule = frontend.getSourceModule(moduleName);
+    if (!sourceModule)
+    {
+        LUAU_ASSERT(!"Expected Source Module for fragment typecheck");
+        return {};
+    }
+
+    FrontendModuleResolver& resolver = getModuleResolver(frontend, opts);
+    ModulePtr module = resolver.getModule(moduleName);
+    if (!module)
+    {
+        LUAU_ASSERT(!"Expected Module for fragment typecheck");
+        return {};
+    }
+
+    if (FFlag::LuauIncrementalAutocompleteBugfixes)
+    {
+        if (sourceModule->allocator.get() != module->allocator.get())
+        {
+            return {FragmentTypeCheckStatus::SkipAutocomplete, {}};
+        }
+    }
+
+    auto tryParse = parseFragment(*sourceModule, src, cursorPos, fragmentEndPosition);
+
+    if (!tryParse)
+        return {FragmentTypeCheckStatus::SkipAutocomplete, {}};
+
+    FragmentParseResult& parseResult = *tryParse;
+
+    if (isWithinComment(parseResult.commentLocations, fragmentEndPosition.value_or(cursorPos)))
+        return {FragmentTypeCheckStatus::SkipAutocomplete, {}};
+
+    FrontendOptions frontendOptions = opts.value_or(frontend.options);
+    const ScopePtr& closestScope = findClosestScope(module, parseResult.nearestStatement);
+    FragmentTypeCheckResult result =
+        typecheckFragment_(frontend, parseResult.root, module, closestScope, cursorPos, std::move(parseResult.alloc), frontendOptions);
+    result.ancestry = std::move(parseResult.ancestry);
+    return {FragmentTypeCheckStatus::Success, result};
+}
+
+FragmentAutocompleteStatusResult tryFragmentAutocomplete(
+    Frontend& frontend,
+    const ModuleName& moduleName,
+    Position cursorPosition,
+    FragmentContext context,
+    StringCompletionCallback stringCompletionCB
+)
+{
+    // TODO: we should calculate fragmentEnd position here, by using context.newAstRoot and cursorPosition
+    try
+    {
+        Luau::FragmentAutocompleteResult fragmentAutocomplete = Luau::fragmentAutocomplete(
+            frontend,
+            context.newSrc,
+            moduleName,
+            cursorPosition,
+            context.opts,
+            std::move(stringCompletionCB),
+            context.DEPRECATED_fragmentEndPosition
+        );
+        return {FragmentAutocompleteStatus::Success, std::move(fragmentAutocomplete)};
+    }
+    catch (const Luau::InternalCompilerError& e)
+    {
+        if (FFlag::LogFragmentsFromAutocomplete)
+            logLuau(e.what());
+        return {FragmentAutocompleteStatus::InternalIce, std::nullopt};
+    }
+}
+
+FragmentAutocompleteResult fragmentAutocomplete(
+    Frontend& frontend,
+    std::string_view src,
+    const ModuleName& moduleName,
+    Position cursorPosition,
+    std::optional<FrontendOptions> opts,
+    StringCompletionCallback callback,
+    std::optional<Position> fragmentEndPosition
+)
+{
+    LUAU_ASSERT(FFlag::LuauAutocompleteRefactorsForIncrementalAutocomplete);
+    LUAU_TIMETRACE_SCOPE("Luau::fragmentAutocomplete", "FragmentAutocomplete");
+    LUAU_TIMETRACE_ARGUMENT("name", moduleName.c_str());
+
+    const SourceModule* sourceModule = frontend.getSourceModule(moduleName);
+    if (!sourceModule)
+    {
+        LUAU_ASSERT(!"Expected Source Module for fragment typecheck");
+        return {};
+    }
+
+    // If the cursor is within a comment in the stale source module we should avoid providing a recommendation
+    if (isWithinComment(*sourceModule, fragmentEndPosition.value_or(cursorPosition)))
+        return {};
+
+    auto [tcStatus, tcResult] = typecheckFragment(frontend, moduleName, cursorPosition, opts, src, fragmentEndPosition);
+    if (tcStatus == FragmentTypeCheckStatus::SkipAutocomplete)
+        return {};
+
+    auto globalScope = (opts && opts->forAutocomplete) ? frontend.globalsForAutocomplete.globalScope.get() : frontend.globals.globalScope.get();
+    if (FFlag::LogFragmentsFromAutocomplete)
+        logLuau(src);
+    TypeArena arenaForFragmentAutocomplete;
+    auto result = Luau::autocomplete_(
+        tcResult.incrementalModule,
+        frontend.builtinTypes,
+        &arenaForFragmentAutocomplete,
+        tcResult.ancestry,
+        globalScope,
+        tcResult.freshScope,
+        cursorPosition,
+        frontend.fileResolver,
+        callback
+    );
+
+    return {std::move(tcResult.incrementalModule), tcResult.freshScope.get(), std::move(arenaForFragmentAutocomplete), std::move(result)};
+}
+
+} // namespace Luau

Analysis/src/Frontend.cpp

@@ -10,8 +10,10 @@
 #include "Luau/ConstraintSolver.h"
 #include "Luau/DataFlowGraph.h"
 #include "Luau/DcrLogger.h"
+#include "Luau/EqSatSimplification.h"
 #include "Luau/FileResolver.h"
 #include "Luau/NonStrictTypeChecker.h"
+#include "Luau/NotNull.h"
 #include "Luau/Parser.h"
 #include "Luau/Scope.h"
 #include "Luau/StringUtils.h"
@@ -36,18 +38,21 @@ LUAU_FASTINT(LuauTypeInferIterationLimit)
 LUAU_FASTINT(LuauTypeInferRecursionLimit)
 LUAU_FASTINT(LuauTarjanChildLimit)
 LUAU_FASTFLAG(LuauInferInNoCheckMode)
-LUAU_FASTFLAGVARIABLE(LuauKnowsTheDataModel3, false)
+LUAU_FASTFLAGVARIABLE(LuauKnowsTheDataModel3)
-LUAU_FASTFLAGVARIABLE(LuauStoreCommentsForDefinitionFiles, false)
 LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJson, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJson)
-LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJsonFile, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJsonFile)
-LUAU_FASTFLAGVARIABLE(DebugLuauForbidInternalTypes, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauForbidInternalTypes)
-LUAU_FASTFLAGVARIABLE(DebugLuauForceStrictMode, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauForceStrictMode)
-LUAU_FASTFLAGVARIABLE(DebugLuauForceNonStrictMode, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauForceNonStrictMode)
-LUAU_FASTFLAGVARIABLE(LuauSourceModuleUpdatedWithSelectedMode, false)
 LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauRunCustomModuleChecks, false)
 
+LUAU_FASTFLAGVARIABLE(LuauBetterReverseDependencyTracking)
+
 LUAU_FASTFLAG(StudioReportLuauAny2)
+LUAU_FASTFLAGVARIABLE(LuauStoreSolverTypeOnModule)
+
+LUAU_FASTFLAGVARIABLE(LuauSelectivelyRetainDFGArena)
 
 namespace Luau
 {
@@ -134,7 +139,7 @@ static ParseResult parseSourceForModule(std::string_view source, Luau::SourceMod
     sourceModule.root = parseResult.root;
     sourceModule.mode = Mode::Definition;
 
-    if (FFlag::LuauStoreCommentsForDefinitionFiles && options.captureComments)
+    if (options.captureComments)
     {
         sourceModule.hotcomments = parseResult.hotcomments;
         sourceModule.commentLocations = parseResult.commentLocations;
@@ -205,72 +210,6 @@ LoadDefinitionFileResult Frontend::loadDefinitionFile(
     return LoadDefinitionFileResult{true, parseResult, sourceModule, checkedModule};
 }
 
-std::vector<std::string_view> parsePathExpr(const AstExpr& pathExpr)
-{
-    const AstExprIndexName* indexName = pathExpr.as<AstExprIndexName>();
-    if (!indexName)
-        return {};
-
-    std::vector<std::string_view> segments{indexName->index.value};
-
-    while (true)
-    {
-        if (AstExprIndexName* in = indexName->expr->as<AstExprIndexName>())
-        {
-            segments.push_back(in->index.value);
-            indexName = in;
-            continue;
-        }
-        else if (AstExprGlobal* indexNameAsGlobal = indexName->expr->as<AstExprGlobal>())
-        {
-            segments.push_back(indexNameAsGlobal->name.value);
-            break;
-        }
-        else if (AstExprLocal* indexNameAsLocal = indexName->expr->as<AstExprLocal>())
-        {
-            segments.push_back(indexNameAsLocal->local->name.value);
-            break;
-        }
-        else
-            return {};
-    }
-
-    std::reverse(segments.begin(), segments.end());
-    return segments;
-}
-
-std::optional<std::string> pathExprToModuleName(const ModuleName& currentModuleName, const std::vector<std::string_view>& segments)
-{
-    if (segments.empty())
-        return std::nullopt;
-
-    std::vector<std::string_view> result;
-
-    auto it = segments.begin();
-
-    if (*it == "script" && !currentModuleName.empty())
-    {
-        result = split(currentModuleName, '/');
-        ++it;
-    }
-
-    for (; it != segments.end(); ++it)
-    {
-        if (result.size() > 1 && *it == "Parent")
-            result.pop_back();
-        else
-            result.push_back(*it);
-    }
-
-    return join(result, "/");
-}
-
-std::optional<std::string> pathExprToModuleName(const ModuleName& currentModuleName, const AstExpr& pathExpr)
-{
-    std::vector<std::string_view> segments = parsePathExpr(pathExpr);
-    return pathExprToModuleName(currentModuleName, segments);
-}
-
 namespace
 {
 
@@ -351,8 +290,7 @@ static void filterLintOptions(LintOptions& lintOptions, const std::vector<HotCom
 std::vector<RequireCycle> getRequireCycles(
     const FileResolver* resolver,
     const std::unordered_map<ModuleName, std::shared_ptr<SourceNode>>& sourceNodes,
-    const SourceNode* start,
+    const SourceNode* start
-    bool stopAtFirst = false
 )
 {
     std::vector<RequireCycle> result;
@@ -422,9 +360,6 @@ std::vector<RequireCycle> getRequireCycles(
         {
             result.push_back({depLocation, std::move(cycle)});
 
-            if (stopAtFirst)
-                return result;
-
             // note: if we didn't find a cycle, all nodes that we've seen don't depend [transitively] on start
             // so it's safe to *only* clear seen vector when we find a cycle
             // if we don't do it, we will not have correct reporting for some cycles
@@ -812,6 +747,32 @@ std::optional<CheckResult> Frontend::getCheckResult(const ModuleName& name, bool
     return checkResult;
 }
 
+std::vector<ModuleName> Frontend::getRequiredScripts(const ModuleName& name)
+{
+    RequireTraceResult require = requireTrace[name];
+    if (isDirty(name))
+    {
+        std::optional<SourceCode> source = fileResolver->readSource(name);
+        if (!source)
+        {
+            return {};
+        }
+        const Config& config = configResolver->getConfig(name);
+        ParseOptions opts = config.parseOptions;
+        opts.captureComments = true;
+        SourceModule result = parse(name, source->source, opts);
+        result.type = source->type;
+        require = traceRequires(fileResolver, result.root, name);
+    }
+    std::vector<std::string> requiredModuleNames;
+    requiredModuleNames.reserve(require.requireList.size());
+    for (const auto& [moduleName, _] : require.requireList)
+    {
+        requiredModuleNames.push_back(moduleName);
+    }
+    return requiredModuleNames;
+}
+
 bool Frontend::parseGraph(
     std::vector<ModuleName>& buildQueue,
     const ModuleName& root,
@@ -860,6 +821,16 @@ bool Frontend::parseGraph(
             topseen = Permanent;
 
             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)
+                {
+                    if (auto it = sourceNodes.find(dep); it != sourceNodes.end())
+                        it->second->dependents.insert(top->name);
+                }
+            }
         }
         else
         {
@@ -948,14 +919,11 @@ void Frontend::addBuildQueueItems(
         data.environmentScope = getModuleEnvironment(*sourceModule, data.config, frontendOptions.forAutocomplete);
         data.recordJsonLog = FFlag::DebugLuauLogSolverToJson;
 
-        Mode mode = sourceModule->mode.value_or(data.config.mode);
-
-        // in NoCheck mode we only need to compute the value of .cyclic for typeck
         // in the future we could replace toposort with an algorithm that can flag cyclic nodes by itself
         // however, for now getRequireCycles isn't expensive in practice on the cases we care about, and long term
         // all correct programs must be acyclic so this code triggers rarely
         if (cycleDetected)
-            data.requireCycles = getRequireCycles(fileResolver, sourceNodes, sourceNode.get(), mode == Mode::NoCheck);
+            data.requireCycles = getRequireCycles(fileResolver, sourceNodes, sourceNode.get());
 
         data.options = frontendOptions;
 
@@ -987,7 +955,6 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
     else
         mode = sourceModule.mode.value_or(config.mode);
 
-    if (FFlag::LuauSourceModuleUpdatedWithSelectedMode)
     item.sourceModule->mode = {mode};
     ScopePtr environmentScope = item.environmentScope;
     double timestamp = getTimestamp();
@@ -1093,6 +1060,11 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
         freeze(module->interfaceTypes);
 
         module->internalTypes.clear();
+        if (FFlag::LuauSelectivelyRetainDFGArena)
+        {
+            module->defArena.allocator.clear();
+            module->keyArena.allocator.clear();
+        }
 
         module->astTypes.clear();
         module->astTypePacks.clear();
@@ -1146,6 +1118,39 @@ void Frontend::recordItemResult(const BuildQueueItem& item)
     if (item.exception)
         std::rethrow_exception(item.exception);
 
+    if (FFlag::LuauBetterReverseDependencyTracking)
+    {
+        bool replacedModule = false;
+        if (item.options.forAutocomplete)
+        {
+            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)
         {
             moduleResolverForAutocomplete.setModule(item.name, item.module);
@@ -1156,6 +1161,7 @@ void Frontend::recordItemResult(const BuildQueueItem& item)
             moduleResolver.setModule(item.name, item.module);
             item.sourceNode->dirtyModule = false;
         }
+    }
 
     stats.timeCheck += item.stats.timeCheck;
     stats.timeLint += item.stats.timeLint;
@@ -1191,6 +1197,13 @@ ScopePtr Frontend::getModuleEnvironment(const SourceModule& module, const Config
     return result;
 }
 
+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);
+}
+
 bool Frontend::isDirty(const ModuleName& name, bool forAutocomplete) const
 {
     auto it = sourceNodes.find(name);
@@ -1204,6 +1217,31 @@ bool Frontend::isDirty(const ModuleName& name, bool forAutocomplete) const
  * It would be nice for this function to be O(1)
  */
 void Frontend::markDirty(const ModuleName& name, std::vector<ModuleName>* markedDirty)
+{
+    LUAU_TIMETRACE_SCOPE("Frontend::markDirty", "Frontend");
+    LUAU_TIMETRACE_ARGUMENT("name", name.c_str());
+
+    if (FFlag::LuauBetterReverseDependencyTracking)
+    {
+        traverseDependents(
+            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;
@@ -1244,6 +1282,33 @@ void Frontend::markDirty(const ModuleName& name, std::vector<ModuleName>* marked
             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)
+        return;
+
+    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 (!processSubtree(sourceNode))
+            continue;
+
+        const Set<ModuleName>& dependents = sourceNode.dependents;
+        queue.insert(queue.end(), dependents.begin(), dependents.end());
+    }
+}
 
 SourceModule* Frontend::getSourceModule(const ModuleName& moduleName)
 {
@@ -1357,11 +1422,15 @@ ModulePtr check(
     LUAU_TIMETRACE_ARGUMENT("name", sourceModule.humanReadableName.c_str());
 
     ModulePtr result = std::make_shared<Module>();
+    if (FFlag::LuauStoreSolverTypeOnModule)
+        result->checkedInNewSolver = true;
     result->name = sourceModule.name;
     result->humanReadableName = sourceModule.humanReadableName;
     result->mode = mode;
     result->internalTypes.owningModule = result.get();
     result->interfaceTypes.owningModule = result.get();
+    result->allocator = sourceModule.allocator;
+    result->names = sourceModule.names;
 
     iceHandler->moduleName = sourceModule.name;
 
@@ -1376,17 +1445,23 @@ ModulePtr check(
         }
     }
 
-    DataFlowGraph dfg = DataFlowGraphBuilder::build(sourceModule.root, iceHandler);
+    DataFlowGraph dfg = DataFlowGraphBuilder::build(sourceModule.root, NotNull{&result->defArena}, NotNull{&result->keyArena}, iceHandler);
 
     UnifierSharedState unifierState{iceHandler};
     unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
     unifierState.counters.iterationLimit = limits.unifierIterationLimit.value_or(FInt::LuauTypeInferIterationLimit);
 
     Normalizer normalizer{&result->internalTypes, builtinTypes, NotNull{&unifierState}};
+    SimplifierPtr simplifier = newSimplifier(NotNull{&result->internalTypes}, builtinTypes);
+    TypeFunctionRuntime typeFunctionRuntime{iceHandler, NotNull{&limits}};
+
+    typeFunctionRuntime.allowEvaluation = sourceModule.parseErrors.empty();
 
     ConstraintGenerator cg{
         result,
         NotNull{&normalizer},
+        NotNull{simplifier.get()},
+        NotNull{&typeFunctionRuntime},
         moduleResolver,
         builtinTypes,
         iceHandler,
@@ -1402,12 +1477,16 @@ ModulePtr check(
 
     ConstraintSolver cs{
         NotNull{&normalizer},
+        NotNull{simplifier.get()},
+        NotNull{&typeFunctionRuntime},
         NotNull(cg.rootScope),
         borrowConstraints(cg.constraints),
+        NotNull{&cg.scopeToFunction},
         result->name,
         moduleResolver,
         requireCycles,
         logger.get(),
+        NotNull{&dfg},
         limits
     };
 
@@ -1461,12 +1540,31 @@ ModulePtr check(
         switch (mode)
         {
         case Mode::Nonstrict:
-            Luau::checkNonStrict(builtinTypes, iceHandler, NotNull{&unifierState}, NotNull{&dfg}, NotNull{&limits}, sourceModule, result.get());
+            Luau::checkNonStrict(
+                builtinTypes,
+                NotNull{simplifier.get()},
+                NotNull{&typeFunctionRuntime},
+                iceHandler,
+                NotNull{&unifierState},
+                NotNull{&dfg},
+                NotNull{&limits},
+                sourceModule,
+                result.get()
+            );
             break;
         case Mode::Definition:
             // fallthrough intentional
         case Mode::Strict:
-            Luau::check(builtinTypes, NotNull{&unifierState}, NotNull{&limits}, logger.get(), sourceModule, result.get());
+            Luau::check(
+                builtinTypes,
+                NotNull{simplifier.get()},
+                NotNull{&typeFunctionRuntime},
+                NotNull{&unifierState},
+                NotNull{&limits},
+                logger.get(),
+                sourceModule,
+                result.get()
+            );
             break;
         case Mode::NoCheck:
             break;
@@ -1647,6 +1745,17 @@ 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)
+        {
+            if (auto depIt = sourceNodes.find(moduleName); depIt != sourceNodes.end())
+                depIt->second->dependents.erase(sourceNode->name);
+        }
+    }
+
     sourceNode->requireSet.clear();
     sourceNode->requireLocations.clear();
     sourceNode->dirtySourceModule = false;
@@ -1768,11 +1877,21 @@ std::string FrontendModuleResolver::getHumanReadableModuleName(const ModuleName&
     return frontend->fileResolver->getHumanReadableModuleName(moduleName);
 }
 
-void FrontendModuleResolver::setModule(const ModuleName& moduleName, ModulePtr module)
+bool FrontendModuleResolver::setModule(const ModuleName& moduleName, ModulePtr module)
 {
     std::scoped_lock lock(moduleMutex);
 
+    if (FFlag::LuauBetterReverseDependencyTracking)
+    {
+        bool replaced = modules.count(moduleName) > 0;
         modules[moduleName] = std::move(module);
+        return replaced;
+    }
+    else
+    {
+        modules[moduleName] = std::move(module);
+        return false;
+    }
 }
 
 void FrontendModuleResolver::clearModules()

Analysis/src/Generalization.cpp

@@ -2,6 +2,8 @@
 
 #include "Luau/Generalization.h"
 
+#include "Luau/Common.h"
+#include "Luau/DenseHash.h"
 #include "Luau/Scope.h"
 #include "Luau/Type.h"
 #include "Luau/ToString.h"
@@ -9,11 +11,15 @@
 #include "Luau/TypePack.h"
 #include "Luau/VisitType.h"
 
+LUAU_FASTFLAG(LuauAutocompleteRefactorsForIncrementalAutocomplete)
+LUAU_FASTFLAGVARIABLE(LuauGeneralizationRemoveRecursiveUpperBound2)
+
 namespace Luau
 {
 
 struct MutatingGeneralizer : TypeOnceVisitor
 {
+    NotNull<TypeArena> arena;
     NotNull<BuiltinTypes> builtinTypes;
 
     NotNull<Scope> scope;
@@ -27,6 +33,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
     bool avoidSealingTables = false;
 
     MutatingGeneralizer(
+        NotNull<TypeArena> arena,
         NotNull<BuiltinTypes> builtinTypes,
         NotNull<Scope> scope,
         NotNull<DenseHashSet<TypeId>> cachedTypes,
@@ -35,6 +42,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
         bool avoidSealingTables
     )
         : TypeOnceVisitor(/* skipBoundTypes */ true)
+        , arena(arena)
         , builtinTypes(builtinTypes)
         , scope(scope)
         , cachedTypes(cachedTypes)
@@ -44,7 +52,7 @@ struct MutatingGeneralizer : TypeOnceVisitor
     {
     }
 
-    static void replace(DenseHashSet<TypeId>& seen, TypeId haystack, TypeId needle, TypeId replacement)
+    void replace(DenseHashSet<TypeId>& seen, TypeId haystack, TypeId needle, TypeId replacement)
     {
         haystack = follow(haystack);
 
@@ -91,6 +99,10 @@ struct MutatingGeneralizer : TypeOnceVisitor
                 LUAU_ASSERT(onlyType != haystack);
                 emplaceType<BoundType>(asMutable(haystack), onlyType);
             }
+            else if (FFlag::LuauGeneralizationRemoveRecursiveUpperBound2 && ut->options.empty())
+            {
+                emplaceType<BoundType>(asMutable(haystack), builtinTypes->neverType);
+            }
 
             return;
         }
@@ -134,6 +146,10 @@ struct MutatingGeneralizer : TypeOnceVisitor
                 LUAU_ASSERT(onlyType != needle);
                 emplaceType<BoundType>(asMutable(needle), onlyType);
             } 
+            else if (FFlag::LuauGeneralizationRemoveRecursiveUpperBound2 && it->parts.empty())
+            {
+                emplaceType<BoundType>(asMutable(needle), builtinTypes->unknownType);
+            }
 
             return;
         }
@@ -445,7 +461,7 @@ struct FreeTypeSearcher : TypeVisitor
                 traverse(*prop.readTy);
             else
             {
-                LUAU_ASSERT(prop.isShared());
+                LUAU_ASSERT(prop.isShared() || FFlag::LuauAutocompleteRefactorsForIncrementalAutocomplete);
 
                 Polarity p = polarity;
                 polarity = Both;
@@ -526,7 +542,7 @@ struct TypeCacher : TypeOnceVisitor
     DenseHashSet<TypePackId> uncacheablePacks{nullptr};
 
     explicit TypeCacher(NotNull<DenseHashSet<TypeId>> cachedTypes)
-        : TypeOnceVisitor(/* skipBoundTypes */ true)
+        : TypeOnceVisitor(/* skipBoundTypes */ false)
         , cachedTypes(cachedTypes)
     {
     }
@@ -563,9 +579,19 @@ struct TypeCacher : TypeOnceVisitor
 
     bool visit(TypeId ty) override
     {
-        if (isUncacheable(ty) || isCached(ty))
+        // NOTE: `TypeCacher` should explicitly visit _all_ types and type packs,
+        // otherwise it's prone to marking types that cannot be cached as
+        // cacheable.
+        LUAU_ASSERT(false);
+        LUAU_UNREACHABLE();
+    }
+
+    bool visit(TypeId ty, const BoundType& btv) override
+    {
+        traverse(btv.boundTo);
+        if (isUncacheable(btv.boundTo))
+            markUncacheable(ty);
         return false;
-        return true;
     }
 
     bool visit(TypeId ty, const FreeType& ft) override
@@ -590,6 +616,12 @@ struct TypeCacher : TypeOnceVisitor
         return false;
     }
 
+    bool visit(TypeId ty, const ErrorType&) override
+    {
+        cache(ty);
+        return false;
+    }
+
     bool visit(TypeId ty, const PrimitiveType&) override
     {
         cache(ty);
@@ -727,6 +759,17 @@ struct TypeCacher : TypeOnceVisitor
         return false;
     }
 
+    bool visit(TypeId ty, const MetatableType& mtv) override
+    {
+        traverse(mtv.table);
+        traverse(mtv.metatable);
+        if (isUncacheable(mtv.table) || isUncacheable(mtv.metatable))
+            markUncacheable(ty);
+        else
+            cache(ty);
+        return false;
+    }
+
     bool visit(TypeId ty, const ClassType&) override
     {
         cache(ty);
@@ -739,6 +782,12 @@ struct TypeCacher : TypeOnceVisitor
         return false;
     }
 
+    bool visit(TypeId ty, const NoRefineType&) override
+    {
+        cache(ty);
+        return false;
+    }
+
     bool visit(TypeId ty, const UnionType& ut) override
     {
         if (isUncacheable(ty) || isCached(ty))
@@ -841,12 +890,31 @@ struct TypeCacher : TypeOnceVisitor
         return false;
     }
 
+    bool visit(TypePackId tp) override
+    {
+        // NOTE: `TypeCacher` should explicitly visit _all_ types and type packs,
+        // otherwise it's prone to marking types that cannot be cached as
+        // cacheable, which will segfault down the line.
+        LUAU_ASSERT(false);
+        LUAU_UNREACHABLE();
+    }
+
     bool visit(TypePackId tp, const FreeTypePack&) override
     {
         markUncacheable(tp);
         return false;
     }
 
+    bool visit(TypePackId tp, const GenericTypePack& gtp) override
+    {
+        return true;
+    }
+
+    bool visit(TypePackId tp, const ErrorTypePack& etp) override
+    {
+        return true;
+    }
+
     bool visit(TypePackId tp, const VariadicTypePack& vtp) override
     {
         if (isUncacheable(tp))
@@ -871,6 +939,32 @@ struct TypeCacher : TypeOnceVisitor
         markUncacheable(tp);
         return false;
     }
+
+    bool visit(TypePackId tp, const BoundTypePack& btp) override
+    {
+        traverse(btp.boundTo);
+        if (isUncacheable(btp.boundTo))
+            markUncacheable(tp);
+        return false;
+    }
+
+    bool visit(TypePackId tp, const TypePack& typ) override
+    {
+        bool uncacheable = false;
+        for (TypeId ty : typ.head)
+        {
+            traverse(ty);
+            uncacheable |= isUncacheable(ty);
+        }
+        if (typ.tail)
+        {
+            traverse(*typ.tail);
+            uncacheable |= isUncacheable(*typ.tail);
+        }
+        if (uncacheable)
+            markUncacheable(tp);
+        return false;
+    }
 };
 
 std::optional<TypeId> generalize(
@@ -890,7 +984,7 @@ std::optional<TypeId> generalize(
     FreeTypeSearcher fts{scope, cachedTypes};
     fts.traverse(ty);
 
-    MutatingGeneralizer gen{builtinTypes, scope, cachedTypes, std::move(fts.positiveTypes), std::move(fts.negativeTypes), avoidSealingTables};
+    MutatingGeneralizer gen{arena, builtinTypes, scope, cachedTypes, std::move(fts.positiveTypes), std::move(fts.negativeTypes), avoidSealingTables};
 
     gen.traverse(ty);
 

Analysis/src/Instantiation.cpp

@@ -11,6 +11,7 @@
 #include <algorithm>
 
 LUAU_FASTFLAG(LuauSolverV2)
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
 
 namespace Luau
 {
@@ -61,9 +62,7 @@ TypeId Instantiation::clean(TypeId ty)
     LUAU_ASSERT(ftv);
 
     FunctionType clone = FunctionType{level, scope, ftv->argTypes, ftv->retTypes, ftv->definition, ftv->hasSelf};
-    clone.magicFunction = ftv->magicFunction;
+    clone.magic = ftv->magic;
-    clone.dcrMagicFunction = ftv->dcrMagicFunction;
-    clone.dcrMagicRefinement = ftv->dcrMagicRefinement;
     clone.tags = ftv->tags;
     clone.argNames = ftv->argNames;
     TypeId result = addType(std::move(clone));
@@ -165,7 +164,7 @@ TypeId ReplaceGenerics::clean(TypeId ty)
     }
     else
     {
-        return addType(FreeType{scope, level});
+        return FFlag::LuauFreeTypesMustHaveBounds ? arena->freshType(builtinTypes, scope, level) : addType(FreeType{scope, level});
     }
 }
 

Analysis/src/IostreamHelpers.cpp

@@ -227,6 +227,8 @@ static void errorToString(std::ostream& stream, const T& err)
         stream << "UnexpectedTypeInSubtyping {  ty = '" + toString(err.ty) + "' }";
     else if constexpr (std::is_same_v<T, UnexpectedTypePackInSubtyping>)
         stream << "UnexpectedTypePackInSubtyping {  tp = '" + toString(err.tp) + "' }";
+    else if constexpr (std::is_same_v<T, UserDefinedTypeFunctionError>)
+        stream << "UserDefinedTypeFunctionError { " << err.message << " }";
     else if constexpr (std::is_same_v<T, CannotAssignToNever>)
     {
         stream << "CannotAssignToNever { rvalueType = '" << toString(err.rhsType) << "', reason = '" << err.reason << "', cause = { ";

Analysis/src/Linter.cpp

@@ -17,8 +17,7 @@ LUAU_FASTINTVARIABLE(LuauSuggestionDistance, 4)
 LUAU_FASTFLAG(LuauSolverV2)
 
 LUAU_FASTFLAG(LuauAttribute)
-LUAU_FASTFLAG(LuauNativeAttribute)
+LUAU_FASTFLAGVARIABLE(LintRedundantNativeAttribute)
-LUAU_FASTFLAGVARIABLE(LintRedundantNativeAttribute, false)
 
 namespace Luau
 {
@@ -3239,7 +3238,6 @@ static void lintComments(LintContext& context, const std::vector<HotComment>& ho
 
 static bool hasNativeCommentDirective(const std::vector<HotComment>& hotcomments)
 {
-    LUAU_ASSERT(FFlag::LuauNativeAttribute);
     LUAU_ASSERT(FFlag::LintRedundantNativeAttribute);
 
     for (const HotComment& hc : hotcomments)
@@ -3265,7 +3263,6 @@ struct LintRedundantNativeAttribute : AstVisitor
 public:
     LUAU_NOINLINE static void process(LintContext& context)
     {
-        LUAU_ASSERT(FFlag::LuauNativeAttribute);
         LUAU_ASSERT(FFlag::LintRedundantNativeAttribute);
 
         LintRedundantNativeAttribute pass;
@@ -3389,7 +3386,7 @@ std::vector<LintWarning> lint(
     if (context.warningEnabled(LintWarning::Code_ComparisonPrecedence))
         LintComparisonPrecedence::process(context);
 
-    if (FFlag::LuauNativeAttribute && FFlag::LintRedundantNativeAttribute && context.warningEnabled(LintWarning::Code_RedundantNativeAttribute))
+    if (FFlag::LintRedundantNativeAttribute && context.warningEnabled(LintWarning::Code_RedundantNativeAttribute))
     {
         if (hasNativeCommentDirective(hotcomments))
             LintRedundantNativeAttribute::process(context);

Analysis/src/Module.cpp

@@ -15,11 +15,32 @@
 #include <algorithm>
 
 LUAU_FASTFLAG(LuauSolverV2);
+LUAU_FASTFLAGVARIABLE(LuauIncrementalAutocompleteCommentDetection)
 
 namespace Luau
 {
 
-static bool contains(Position pos, Comment comment)
+static void defaultLogLuau(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.
+}
+
+Luau::LogLuauProc logLuau = &defaultLogLuau;
+
+void setLogLuau(LogLuauProc ll)
+{
+    logLuau = ll;
+}
+
+void resetLogLuauProc()
+{
+    logLuau = &defaultLogLuau;
+}
+
+
+
+static bool contains_DEPRECATED(Position pos, Comment comment)
 {
     if (comment.location.contains(pos))
         return true;
@@ -32,7 +53,22 @@ static bool contains(Position pos, Comment comment)
         return false;
 }
 
-static bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos)
+static bool contains(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;
+    // comments actually span the whole line - in incremental mode, we could pass a cursor outside of the current parsed comment range span, but it
+    // would still be 'within' the comment So, the cursor must be on the same line and the comment itself must come strictly after the `begin`
+    else if (comment.type == Lexeme::Comment && comment.location.end.line == pos.line && comment.location.begin <= pos)
+        return true;
+    else
+        return false;
+}
+
+bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos)
 {
     auto iter = std::lower_bound(
         commentLocations.begin(),
@@ -40,6 +76,11 @@ static bool isWithinComment(const std::vector<Comment>& commentLocations, Positi
         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;
+            }
             return a.location.end < b.location.end;
         }
     );
@@ -47,7 +88,7 @@ static bool isWithinComment(const std::vector<Comment>& commentLocations, Positi
     if (iter == commentLocations.end())
         return false;
 
-    if (contains(pos, *iter))
+    if (FFlag::LuauIncrementalAutocompleteCommentDetection ? contains(pos, *iter) : contains_DEPRECATED(pos, *iter))
         return true;
 
     // Due to the nature of std::lower_bound, it is possible that iter points at a comment that ends
@@ -131,19 +172,61 @@ struct ClonePublicInterface : Substitution
             }
 
             ftv->level = TypeLevel{0, 0};
+            if (FFlag::LuauSolverV2)
+                ftv->scope = nullptr;
         }
         else if (TableType* ttv = getMutable<TableType>(result))
         {
             ttv->level = TypeLevel{0, 0};
+            if (FFlag::LuauSolverV2)
+                ttv->scope = nullptr;
+        }
+
+        if (FFlag::LuauSolverV2)
+        {
+            if (auto freety = getMutable<FreeType>(result))
+            {
+                module->errors.emplace_back(
+                    freety->scope->location,
+                    module->name,
+                    InternalError{"Free type is escaping its module; please report this bug at "
+                                  "https://github.com/luau-lang/luau/issues"}
+                );
+                result = builtinTypes->errorRecoveryType();
+            }
+            else if (auto genericty = getMutable<GenericType>(result))
+            {
+                genericty->scope = nullptr;
+            }
         }
 
         return result;
     }
 
     TypePackId clean(TypePackId tp) override
+    {
+        if (FFlag::LuauSolverV2)
+        {
+            auto clonedTp = clone(tp);
+            if (auto ftp = getMutable<FreeTypePack>(clonedTp))
+            {
+                module->errors.emplace_back(
+                    ftp->scope->location,
+                    module->name,
+                    InternalError{"Free type pack is escaping its module; please report this bug at "
+                                  "https://github.com/luau-lang/luau/issues"}
+                );
+                clonedTp = builtinTypes->errorRecoveryTypePack();
+            }
+            else if (auto gtp = getMutable<GenericTypePack>(clonedTp))
+                gtp->scope = nullptr;
+            return clonedTp;
+        }
+        else
         {
             return clone(tp);
         }
+    }
 
     TypeId cloneType(TypeId ty)
     {

Analysis/src/NonStrictTypeChecker.cpp

@@ -14,11 +14,15 @@
 #include "Luau/TypeFunction.h"
 #include "Luau/Def.h"
 #include "Luau/ToString.h"
-#include "Luau/TypeFwd.h"
+#include "Luau/TypeUtils.h"
 
 #include <iostream>
 #include <iterator>
 
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+LUAU_FASTFLAGVARIABLE(LuauNonStrictVisitorImprovements)
+LUAU_FASTFLAGVARIABLE(LuauNewNonStrictWarnOnUnknownGlobals)
+
 namespace Luau
 {
 
@@ -154,8 +158,9 @@ private:
 
 struct NonStrictTypeChecker
 {
-
     NotNull<BuiltinTypes> builtinTypes;
+    NotNull<Simplifier> simplifier;
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     const NotNull<InternalErrorReporter> ice;
     NotNull<TypeArena> arena;
     Module* module;
@@ -171,6 +176,8 @@ struct NonStrictTypeChecker
     NonStrictTypeChecker(
         NotNull<TypeArena> arena,
         NotNull<BuiltinTypes> builtinTypes,
+        NotNull<Simplifier> simplifier,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
         const NotNull<InternalErrorReporter> ice,
         NotNull<UnifierSharedState> unifierState,
         NotNull<const DataFlowGraph> dfg,
@@ -178,11 +185,13 @@ struct NonStrictTypeChecker
         Module* module
     )
         : builtinTypes(builtinTypes)
+        , simplifier(simplifier)
+        , typeFunctionRuntime(typeFunctionRuntime)
         , ice(ice)
         , arena(arena)
         , module(module)
         , normalizer{arena, builtinTypes, unifierState, /* cache inhabitance */ true}
-        , subtyping{builtinTypes, arena, NotNull(&normalizer), ice}
+        , subtyping{builtinTypes, arena, simplifier, NotNull(&normalizer), typeFunctionRuntime, ice}
         , dfg(dfg)
         , limits(limits)
     {
@@ -204,7 +213,7 @@ struct NonStrictTypeChecker
             return *fst;
         else if (auto ftp = get<FreeTypePack>(pack))
         {
-            TypeId result = arena->addType(FreeType{ftp->scope});
+            TypeId result = FFlag::LuauFreeTypesMustHaveBounds ? arena->freshType(builtinTypes, ftp->scope) : arena->addType(FreeType{ftp->scope});
             TypePackId freeTail = arena->addTypePack(FreeTypePack{ftp->scope});
 
             TypePack* resultPack = emplaceTypePack<TypePack>(asMutable(pack));
@@ -213,7 +222,7 @@ struct NonStrictTypeChecker
 
             return result;
         }
-        else if (get<Unifiable::Error>(pack))
+        else if (get<ErrorTypePack>(pack))
             return builtinTypes->errorRecoveryType();
         else if (finite(pack) && size(pack) == 0)
             return builtinTypes->nilType; // `(f())` where `f()` returns no values is coerced into `nil`
@@ -228,7 +237,12 @@ struct NonStrictTypeChecker
             return instance;
 
         ErrorVec errors =
-            reduceTypeFunctions(instance, location, TypeFunctionContext{arena, builtinTypes, stack.back(), NotNull{&normalizer}, ice, limits}, true)
+            reduceTypeFunctions(
+                instance,
+                location,
+                TypeFunctionContext{arena, builtinTypes, stack.back(), simplifier, NotNull{&normalizer}, typeFunctionRuntime, ice, limits},
+                true
+            )
                 .errors;
 
         if (errors.empty())
@@ -329,8 +343,9 @@ struct NonStrictTypeChecker
 
     NonStrictContext visit(AstStatIf* ifStatement)
     {
-        NonStrictContext condB = visit(ifStatement->condition);
+        NonStrictContext condB = visit(ifStatement->condition, ValueContext::RValue);
         NonStrictContext branchContext;
+
         // If there is no else branch, don't bother generating warnings for the then branch - we can't prove there is an error
         if (ifStatement->elsebody)
         {
@@ -338,16 +353,31 @@ struct NonStrictTypeChecker
             NonStrictContext elseBody = visit(ifStatement->elsebody);
             branchContext = NonStrictContext::conjunction(builtinTypes, arena, thenBody, elseBody);
         }
+
         return NonStrictContext::disjunction(builtinTypes, arena, condB, branchContext);
     }
 
     NonStrictContext visit(AstStatWhile* whileStatement)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            NonStrictContext condition = visit(whileStatement->condition, ValueContext::RValue);
+            NonStrictContext body = visit(whileStatement->body);
+            return NonStrictContext::disjunction(builtinTypes, arena, condition, body);
+        }
+        else
             return {};
     }
 
     NonStrictContext visit(AstStatRepeat* repeatStatement)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            NonStrictContext body = visit(repeatStatement->body);
+            NonStrictContext condition = visit(repeatStatement->condition, ValueContext::RValue);
+            return NonStrictContext::disjunction(builtinTypes, arena, body, condition);
+        }
+        else
             return {};
     }
 
@@ -363,49 +393,94 @@ struct NonStrictTypeChecker
 
     NonStrictContext visit(AstStatReturn* returnStatement)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            // TODO: this is believing existing code, but i'm not sure if this makes sense
+            // for how the contexts are handled
+            for (AstExpr* expr : returnStatement->list)
+                visit(expr, ValueContext::RValue);
+        }
+
         return {};
     }
 
     NonStrictContext visit(AstStatExpr* expr)
     {
-        return visit(expr->expr);
+        return visit(expr->expr, ValueContext::RValue);
     }
 
     NonStrictContext visit(AstStatLocal* local)
     {
         for (AstExpr* rhs : local->values)
-            visit(rhs);
+            visit(rhs, ValueContext::RValue);
         return {};
     }
 
     NonStrictContext visit(AstStatFor* forStatement)
+    {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            // TODO: throwing out context based on same principle as existing code?
+            if (forStatement->from)
+                visit(forStatement->from, ValueContext::RValue);
+            if (forStatement->to)
+                visit(forStatement->to, ValueContext::RValue);
+            if (forStatement->step)
+                visit(forStatement->step, ValueContext::RValue);
+            return visit(forStatement->body);
+        }
+        else
         {
             return {};
         }
+    }
 
     NonStrictContext visit(AstStatForIn* forInStatement)
+    {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (AstExpr* rhs : forInStatement->values)
+                visit(rhs, ValueContext::RValue);
+            return visit(forInStatement->body);
+        }
+        else
         {
             return {};
         }
+    }
 
     NonStrictContext visit(AstStatAssign* assign)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (AstExpr* lhs : assign->vars)
+                visit(lhs, ValueContext::LValue);
+            for (AstExpr* rhs : assign->values)
+                visit(rhs, ValueContext::RValue);
+        }
+
         return {};
     }
 
     NonStrictContext visit(AstStatCompoundAssign* compoundAssign)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            visit(compoundAssign->var, ValueContext::LValue);
+            visit(compoundAssign->value, ValueContext::RValue);
+        }
+
         return {};
     }
 
     NonStrictContext visit(AstStatFunction* statFn)
     {
-        return visit(statFn->func);
+        return visit(statFn->func, ValueContext::RValue);
     }
 
     NonStrictContext visit(AstStatLocalFunction* localFn)
     {
-        return visit(localFn->func);
+        return visit(localFn->func, ValueContext::RValue);
     }
 
     NonStrictContext visit(AstStatTypeAlias* typeAlias)
@@ -415,7 +490,6 @@ struct NonStrictTypeChecker
 
     NonStrictContext visit(AstStatTypeFunction* typeFunc)
     {
-        reportError(GenericError{"This syntax is not supported"}, typeFunc->location);
         return {};
     }
 
@@ -436,14 +510,22 @@ struct NonStrictTypeChecker
 
     NonStrictContext visit(AstStatError* error)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (AstStat* stat : error->statements)
+                visit(stat);
+            for (AstExpr* expr : error->expressions)
+                visit(expr, ValueContext::RValue);
+        }
+
         return {};
     }
 
-    NonStrictContext visit(AstExpr* expr)
+    NonStrictContext visit(AstExpr* expr, ValueContext context)
     {
         auto pusher = pushStack(expr);
         if (auto e = expr->as<AstExprGroup>())
-            return visit(e);
+            return visit(e, context);
         else if (auto e = expr->as<AstExprConstantNil>())
             return visit(e);
         else if (auto e = expr->as<AstExprConstantBool>())
@@ -453,17 +535,17 @@ struct NonStrictTypeChecker
         else if (auto e = expr->as<AstExprConstantString>())
             return visit(e);
         else if (auto e = expr->as<AstExprLocal>())
-            return visit(e);
+            return visit(e, context);
         else if (auto e = expr->as<AstExprGlobal>())
-            return visit(e);
+            return visit(e, context);
         else if (auto e = expr->as<AstExprVarargs>())
             return visit(e);
         else if (auto e = expr->as<AstExprCall>())
             return visit(e);
         else if (auto e = expr->as<AstExprIndexName>())
-            return visit(e);
+            return visit(e, context);
         else if (auto e = expr->as<AstExprIndexExpr>())
-            return visit(e);
+            return visit(e, context);
         else if (auto e = expr->as<AstExprFunction>())
             return visit(e);
         else if (auto e = expr->as<AstExprTable>())
@@ -487,8 +569,11 @@ struct NonStrictTypeChecker
         }
     }
 
-    NonStrictContext visit(AstExprGroup* group)
+    NonStrictContext visit(AstExprGroup* group, ValueContext context)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+            return visit(group->expr, context);
+        else
             return {};
     }
 
@@ -512,22 +597,34 @@ struct NonStrictTypeChecker
         return {};
     }
 
-    NonStrictContext visit(AstExprLocal* local)
+    NonStrictContext visit(AstExprLocal* local, ValueContext context)
     {
         return {};
     }
 
-    NonStrictContext visit(AstExprGlobal* global)
+    NonStrictContext visit(AstExprGlobal* global, ValueContext context)
     {
+        if (FFlag::LuauNewNonStrictWarnOnUnknownGlobals)
+        {
+            // We don't file unknown symbols for LValues.
+            if (context == ValueContext::LValue)
+                return {};
+
+            NotNull<Scope> scope = stack.back();
+            if (!scope->lookup(global->name))
+            {
+                reportError(UnknownSymbol{global->name.value, UnknownSymbol::Binding}, global->location);
+            }
+        }
+
         return {};
     }
 
-    NonStrictContext visit(AstExprVarargs* global)
+    NonStrictContext visit(AstExprVarargs* varargs)
     {
         return {};
     }
 
-
     NonStrictContext visit(AstExprCall* call)
     {
         NonStrictContext fresh{};
@@ -536,9 +633,7 @@ struct NonStrictTypeChecker
             return fresh;
 
         TypeId fnTy = *originalCallTy;
-        if (auto fn = get<FunctionType>(follow(fnTy)))
+        if (auto fn = get<FunctionType>(follow(fnTy)); fn && fn->isCheckedFunction)
-        {
-            if (fn->isCheckedFunction)
         {
             // We know fn is a checked function, which means it looks like:
             // (S1, ... SN) -> T &
@@ -547,21 +642,33 @@ struct NonStrictTypeChecker
             // ...
             // ...
             // (unknown^N-1, ~S_N) -> error
+
+            std::vector<AstExpr*> arguments;
+            arguments.reserve(call->args.size + (call->self ? 1 : 0));
+            if (call->self)
+            {
+                if (auto indexExpr = call->func->as<AstExprIndexName>())
+                    arguments.push_back(indexExpr->expr);
+                else
+                    ice->ice("method call expression has no 'self'");
+            }
+            arguments.insert(arguments.end(), call->args.begin(), call->args.end());
+
             std::vector<TypeId> argTypes;
-                argTypes.reserve(call->args.size);
+            argTypes.reserve(arguments.size());
-                // Pad out the arg types array with the types you would expect to see
+
+            // Move all the types over from the argument typepack for `fn`
             TypePackIterator curr = begin(fn->argTypes);
             TypePackIterator fin = end(fn->argTypes);
-                while (curr != fin)
+            for (; curr != fin; curr++)
-                {
                 argTypes.push_back(*curr);
-                    ++curr;
+
-                }
+            // Pad out the rest with the variadic as needed.
             if (auto argTail = curr.tail())
             {
                 if (const VariadicTypePack* vtp = get<VariadicTypePack>(follow(*argTail)))
                 {
-                        while (argTypes.size() < call->args.size)
+                    while (argTypes.size() < arguments.size())
                     {
                         argTypes.push_back(vtp->ty);
                     }
@@ -569,26 +676,26 @@ struct NonStrictTypeChecker
             }
 
             std::string functionName = getFunctionNameAsString(*call->func).value_or("");
-                if (call->args.size > argTypes.size())
+            if (arguments.size() > argTypes.size())
             {
                 // We are passing more arguments than we expect, so we should error
-                    reportError(CheckedFunctionIncorrectArgs{functionName, argTypes.size(), call->args.size}, call->location);
+                reportError(CheckedFunctionIncorrectArgs{functionName, argTypes.size(), arguments.size()}, call->location);
                 return fresh;
             }
 
-                for (size_t i = 0; i < call->args.size; i++)
+            for (size_t i = 0; i < arguments.size(); i++)
             {
                 // For example, if the arg is "hi"
                 // The actual arg type is string
                 // The expected arg type is number
                 // The type of the argument in the overload is ~number
                 // We will compare arg and ~number
-                    AstExpr* arg = call->args.data[i];
+                AstExpr* arg = arguments[i];
                 TypeId expectedArgType = argTypes[i];
                 std::shared_ptr<const NormalizedType> norm = normalizer.normalize(expectedArgType);
                 DefId def = dfg->getDef(arg);
                 TypeId runTimeErrorTy;
-                    // If we're dealing with any, negating any will cause all subtype tests to fail, since ~any is any
+                // If we're dealing with any, negating any will cause all subtype tests to fail
                 // However, when someone calls this function, they're going to want to be able to pass it anything,
                 // for that reason, we manually inject never into the context so that the runtime test will always pass.
                 if (!norm)
@@ -602,39 +709,49 @@ struct NonStrictTypeChecker
             }
 
             // Populate the context and now iterate through each of the arguments to the call to find out if we satisfy the types
-                for (size_t i = 0; i < call->args.size; i++)
+            for (size_t i = 0; i < arguments.size(); i++)
             {
-                    AstExpr* arg = call->args.data[i];
+                AstExpr* arg = arguments[i];
                 if (auto runTimeFailureType = willRunTimeError(arg, fresh))
                     reportError(CheckedFunctionCallError{argTypes[i], *runTimeFailureType, functionName, i}, arg->location);
             }
 
-                if (call->args.size < argTypes.size())
+            if (arguments.size() < argTypes.size())
             {
                 // We are passing fewer arguments than we expect
                 // so we need to ensure that the rest of the args are optional.
                 bool remainingArgsOptional = true;
-                    for (size_t i = call->args.size; i < argTypes.size(); i++)
+                for (size_t i = arguments.size(); i < argTypes.size(); i++)
                     remainingArgsOptional = remainingArgsOptional && isOptional(argTypes[i]);
+
                 if (!remainingArgsOptional)
                 {
-                        reportError(CheckedFunctionIncorrectArgs{functionName, argTypes.size(), call->args.size}, call->location);
+                    reportError(CheckedFunctionIncorrectArgs{functionName, argTypes.size(), arguments.size()}, call->location);
                     return fresh;
                 }
             }
         }
-        }
 
         return fresh;
     }
 
-    NonStrictContext visit(AstExprIndexName* indexName)
+    NonStrictContext visit(AstExprIndexName* indexName, ValueContext context)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+            return visit(indexName->expr, context);
+        else
             return {};
     }
 
-    NonStrictContext visit(AstExprIndexExpr* indexExpr)
+    NonStrictContext visit(AstExprIndexExpr* indexExpr, ValueContext context)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            NonStrictContext expr = visit(indexExpr->expr, context);
+            NonStrictContext index = visit(indexExpr->index, ValueContext::RValue);
+            return NonStrictContext::disjunction(builtinTypes, arena, expr, index);
+        }
+        else
             return {};
     }
 
@@ -654,39 +771,74 @@ struct NonStrictTypeChecker
 
     NonStrictContext visit(AstExprTable* table)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (auto [_, key, value] : table->items)
+            {
+                if (key)
+                    visit(key, ValueContext::RValue);
+                visit(value, ValueContext::RValue);
+            }
+        }
+
         return {};
     }
 
     NonStrictContext visit(AstExprUnary* unary)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+            return visit(unary->expr, ValueContext::RValue);
+        else
             return {};
     }
 
     NonStrictContext visit(AstExprBinary* binary)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            NonStrictContext lhs = visit(binary->left, ValueContext::RValue);
+            NonStrictContext rhs = visit(binary->right, ValueContext::RValue);
+            return NonStrictContext::disjunction(builtinTypes, arena, lhs, rhs);
+        }
+        else
             return {};
     }
 
     NonStrictContext visit(AstExprTypeAssertion* typeAssertion)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+            return visit(typeAssertion->expr, ValueContext::RValue);
+        else
             return {};
     }
 
     NonStrictContext visit(AstExprIfElse* ifElse)
     {
-        NonStrictContext condB = visit(ifElse->condition);
+        NonStrictContext condB = visit(ifElse->condition, ValueContext::RValue);
-        NonStrictContext thenB = visit(ifElse->trueExpr);
+        NonStrictContext thenB = visit(ifElse->trueExpr, ValueContext::RValue);
-        NonStrictContext elseB = visit(ifElse->falseExpr);
+        NonStrictContext elseB = visit(ifElse->falseExpr, ValueContext::RValue);
         return NonStrictContext::disjunction(builtinTypes, arena, condB, NonStrictContext::conjunction(builtinTypes, arena, thenB, elseB));
     }
 
     NonStrictContext visit(AstExprInterpString* interpString)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (AstExpr* expr : interpString->expressions)
+                visit(expr, ValueContext::RValue);
+        }
+
         return {};
     }
 
     NonStrictContext visit(AstExprError* error)
     {
+        if (FFlag::LuauNonStrictVisitorImprovements)
+        {
+            for (AstExpr* expr : error->expressions)
+                visit(expr, ValueContext::RValue);
+        }
+
         return {};
     }
 
@@ -754,6 +906,8 @@ private:
 
 void checkNonStrict(
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<InternalErrorReporter> ice,
     NotNull<UnifierSharedState> unifierState,
     NotNull<const DataFlowGraph> dfg,
@@ -764,7 +918,9 @@ void checkNonStrict(
 {
     LUAU_TIMETRACE_SCOPE("checkNonStrict", "Typechecking");
 
-    NonStrictTypeChecker typeChecker{NotNull{&module->internalTypes}, builtinTypes, ice, unifierState, dfg, limits, module};
+    NonStrictTypeChecker typeChecker{
+        NotNull{&module->internalTypes}, builtinTypes, simplifier, typeFunctionRuntime, ice, unifierState, dfg, limits, module
+    };
     typeChecker.visit(sourceModule.root);
     unfreeze(module->interfaceTypes);
     copyErrors(module->errors, module->interfaceTypes, builtinTypes);

Analysis/src/Normalize.cpp

@@ -15,36 +15,17 @@
 #include "Luau/TypeFwd.h"
 #include "Luau/Unifier.h"
 
-LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant)
-LUAU_FASTFLAGVARIABLE(LuauNormalizeAwayUninhabitableTables, false)
-LUAU_FASTFLAGVARIABLE(LuauNormalizeNotUnknownIntersection, false);
-LUAU_FASTFLAGVARIABLE(LuauFixReduceStackPressure, false);
-LUAU_FASTFLAGVARIABLE(LuauFixCyclicTablesBlowingStack, false);
 
-// This could theoretically be 2000 on amd64, but x86 requires this.
+LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000)
-LUAU_FASTINTVARIABLE(LuauNormalizeIterationLimit, 1200);
+LUAU_FASTINTVARIABLE(LuauNormalizeIntersectionLimit, 200)
-LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
+LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTFLAG(LuauSolverV2);
+LUAU_FASTFLAGVARIABLE(LuauFixInfiniteRecursionInNormalization)
-
+LUAU_FASTFLAGVARIABLE(LuauFixNormalizedIntersectionOfNegatedClass)
-static bool fixReduceStackPressure()
-{
-    return FFlag::LuauFixReduceStackPressure || FFlag::LuauSolverV2;
-}
-
-static bool fixCyclicTablesBlowingStack()
-{
-    return FFlag::LuauFixCyclicTablesBlowingStack || FFlag::LuauSolverV2;
-}
 
 namespace Luau
 {
 
-// helper to make `FFlag::LuauNormalizeAwayUninhabitableTables` not explicitly required when DCR is enabled.
-static bool normalizeAwayUninhabitableTables()
-{
-    return FFlag::LuauNormalizeAwayUninhabitableTables || FFlag::LuauSolverV2;
-}
-
 static bool shouldEarlyExit(NormalizationResult res)
 {
     // if res is hit limits, return control flow
@@ -589,10 +570,11 @@ NormalizationResult Normalizer::isInhabited(TypeId ty, Set<TypeId>& seen)
 NormalizationResult Normalizer::isIntersectionInhabited(TypeId left, TypeId right)
 {
     Set<TypeId> seen{nullptr};
-    return isIntersectionInhabited(left, right, seen);
+    SeenTablePropPairs seenTablePropPairs{{nullptr, nullptr}};
+    return isIntersectionInhabited(left, right, seenTablePropPairs, seen);
 }
 
-NormalizationResult Normalizer::isIntersectionInhabited(TypeId left, TypeId right, Set<TypeId>& seenSet)
+NormalizationResult Normalizer::isIntersectionInhabited(TypeId left, TypeId right, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSet)
 {
     left = follow(left);
     right = follow(right);
@@ -605,7 +587,7 @@ NormalizationResult Normalizer::isIntersectionInhabited(TypeId left, TypeId righ
     }
 
     NormalizedType norm{builtinTypes};
-    NormalizationResult res = normalizeIntersections({left, right}, norm, seenSet);
+    NormalizationResult res = normalizeIntersections({left, right}, norm, seenTablePropPairs, seenSet);
     if (res != NormalizationResult::True)
     {
         if (cacheInhabitance && res == NormalizationResult::False)
@@ -956,7 +938,8 @@ std::shared_ptr<const NormalizedType> Normalizer::normalize(TypeId ty)
 
     NormalizedType norm{builtinTypes};
     Set<TypeId> seenSetTypes{nullptr};
-    NormalizationResult res = unionNormalWithTy(norm, ty, seenSetTypes);
+    SeenTablePropPairs seenTablePropPairs{{nullptr, nullptr}};
+    NormalizationResult res = unionNormalWithTy(norm, ty, seenTablePropPairs, seenSetTypes);
     if (res != NormalizationResult::True)
         return nullptr;
 
@@ -974,7 +957,12 @@ std::shared_ptr<const NormalizedType> Normalizer::normalize(TypeId ty)
     return shared;
 }
 
-NormalizationResult Normalizer::normalizeIntersections(const std::vector<TypeId>& intersections, NormalizedType& outType, Set<TypeId>& seenSet)
+NormalizationResult Normalizer::normalizeIntersections(
+    const std::vector<TypeId>& intersections,
+    NormalizedType& outType,
+    SeenTablePropPairs& seenTablePropPairs,
+    Set<TypeId>& seenSet
+)
 {
     if (!arena)
         sharedState->iceHandler->ice("Normalizing types outside a module");
@@ -983,7 +971,7 @@ NormalizationResult Normalizer::normalizeIntersections(const std::vector<TypeId>
     // Now we need to intersect the two types
     for (auto ty : intersections)
     {
-        NormalizationResult res = intersectNormalWithTy(norm, ty, seenSet);
+        NormalizationResult res = intersectNormalWithTy(norm, ty, seenTablePropPairs, seenSet);
         if (res != NormalizationResult::True)
             return res;
     }
@@ -1620,7 +1608,7 @@ void Normalizer::unionTablesWithTable(TypeIds& heres, TypeId there)
     // TODO: remove unions of tables where possible
 
     // we can always skip `never`
-    if (normalizeAwayUninhabitableTables() && get<NeverType>(there))
+    if (get<NeverType>(there))
         return;
 
     heres.insert(there);
@@ -1747,7 +1735,13 @@ NormalizationResult Normalizer::intersectNormalWithNegationTy(TypeId toNegate, N
 }
 
 // See above for an explaination of `ignoreSmallerTyvars`.
-NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, Set<TypeId>& seenSetTypes, int ignoreSmallerTyvars)
+NormalizationResult Normalizer::unionNormalWithTy(
+    NormalizedType& here,
+    TypeId there,
+    SeenTablePropPairs& seenTablePropPairs,
+    Set<TypeId>& seenSetTypes,
+    int ignoreSmallerTyvars
+)
 {
     RecursionCounter _rc(&sharedState->counters.recursionCount);
     if (!withinResourceLimits())
@@ -1779,7 +1773,7 @@ NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId t
 
         for (UnionTypeIterator it = begin(utv); it != end(utv); ++it)
         {
-            NormalizationResult res = unionNormalWithTy(here, *it, seenSetTypes);
+            NormalizationResult res = unionNormalWithTy(here, *it, seenTablePropPairs, seenSetTypes);
             if (res != NormalizationResult::True)
             {
                 seenSetTypes.erase(there);
@@ -1800,7 +1794,7 @@ NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId t
         norm.tops = builtinTypes->anyType;
         for (IntersectionTypeIterator it = begin(itv); it != end(itv); ++it)
         {
-            NormalizationResult res = intersectNormalWithTy(norm, *it, seenSetTypes);
+            NormalizationResult res = intersectNormalWithTy(norm, *it, seenTablePropPairs, seenSetTypes);
             if (res != NormalizationResult::True)
             {
                 seenSetTypes.erase(there);
@@ -1814,7 +1808,8 @@ NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId t
     }
     else if (get<UnknownType>(here.tops))
         return NormalizationResult::True;
-    else if (get<GenericType>(there) || get<FreeType>(there) || get<BlockedType>(there) || get<PendingExpansionType>(there) || get<TypeFunctionInstanceType>(there))
+    else if (get<GenericType>(there) || get<FreeType>(there) || get<BlockedType>(there) || get<PendingExpansionType>(there) ||
+             get<TypeFunctionInstanceType>(there))
     {
         if (tyvarIndex(there) <= ignoreSmallerTyvars)
             return NormalizationResult::True;
@@ -1891,7 +1886,7 @@ NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId t
         if (res != NormalizationResult::True)
             return res;
     }
-    else if (get<PendingExpansionType>(there) || get<TypeFunctionInstanceType>(there))
+    else if (get<PendingExpansionType>(there) || get<TypeFunctionInstanceType>(there) || get<NoRefineType>(there))
     {
         // nothing
     }
@@ -1900,7 +1895,7 @@ NormalizationResult Normalizer::unionNormalWithTy(NormalizedType& here, TypeId t
 
     for (auto& [tyvar, intersect] : here.tyvars)
     {
-        NormalizationResult res = unionNormalWithTy(*intersect, there, seenSetTypes, tyvarIndex(tyvar));
+        NormalizationResult res = unionNormalWithTy(*intersect, there, seenTablePropPairs, seenSetTypes, tyvarIndex(tyvar));
         if (res != NormalizationResult::True)
             return res;
     }
@@ -2289,9 +2284,24 @@ void Normalizer::intersectClassesWithClass(NormalizedClassType& heres, TypeId th
         else if (isSubclass(there, hereTy))
         {
             TypeIds negations = std::move(hereNegations);
+            bool emptyIntersectWithNegation = false;
 
             for (auto nIt = negations.begin(); nIt != negations.end();)
             {
+                if (FFlag::LuauFixNormalizedIntersectionOfNegatedClass && isSubclass(there, *nIt))
+                {
+                    // Hitting this block means that the incoming class is a
+                    // subclass of this type, _and_ one of its negations is a
+                    // superclass of this type, e.g.:
+                    //
+                    //  Dog & ~Animal
+                    //
+                    // Clearly this intersects to never, so we mark this class as
+                    // being removed from the normalized class type.
+                    emptyIntersectWithNegation = true;
+                    break;
+                }
+
                 if (!isSubclass(*nIt, there))
                 {
                     nIt = negations.erase(nIt);
@@ -2304,6 +2314,7 @@ void Normalizer::intersectClassesWithClass(NormalizedClassType& heres, TypeId th
 
             it = heres.ordering.erase(it);
             heres.classes.erase(hereTy);
+            if (!emptyIntersectWithNegation)
                 heres.pushPair(there, std::move(negations));
             break;
         }
@@ -2510,7 +2521,7 @@ std::optional<TypePackId> Normalizer::intersectionOfTypePacks(TypePackId here, T
         return arena->addTypePack({});
 }
 
-std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there, Set<TypeId>& seenSet)
+std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSet)
 {
     if (here == there)
         return here;
@@ -2589,50 +2600,61 @@ std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there
                 {
                     if (tprop.readTy.has_value())
                     {
-                        // if the intersection of the read types of a property is uninhabited, the whole table is `never`.
+                        if (FFlag::LuauFixInfiniteRecursionInNormalization)
-                        if (fixReduceStackPressure())
                         {
+                            TypeId ty = simplifyIntersection(builtinTypes, NotNull{arena}, *hprop.readTy, *tprop.readTy).result;
+
+                            // If any property is going to get mapped to `never`, we can just call the entire table `never`.
+                            // Since this check is syntactic, we may sometimes miss simplifying tables with complex uninhabited properties.
+                            // Prior versions of this code attempted to do this semantically using the normalization machinery, but this
+                            // mistakenly causes infinite loops when giving more complex recursive table types. As it stands, this approach
+                            // will continue to scale as simplification is improved, but we may wish to reintroduce the semantic approach
+                            // once we have revisited the usage of seen sets systematically (and possibly with some additional guarding to recognize
+                            // when types are infinitely-recursive with non-pointer identical instances of them, or some guard to prevent that
+                            // construction altogether). See also: `gh1632_no_infinite_recursion_in_normalization`
+                            if (get<NeverType>(ty))
+                                return {builtinTypes->neverType};
+
+                            prop.readTy = ty;
+                            hereSubThere &= (ty == hprop.readTy);
+                            thereSubHere &= (ty == tprop.readTy);
+                        }
+                        else
+                        {
+                            // if the intersection of the read types of a property is uninhabited, the whole table is `never`.
                             // We've seen these table prop elements before and we're about to ask if their intersection
                             // is inhabited
-                            if (fixCyclicTablesBlowingStack())
+
+                            auto pair1 = std::pair{*hprop.readTy, *tprop.readTy};
+                            auto pair2 = std::pair{*tprop.readTy, *hprop.readTy};
+                            if (seenTablePropPairs.contains(pair1) || seenTablePropPairs.contains(pair2))
                             {
-                                if (seenSet.contains(*hprop.readTy) && seenSet.contains(*tprop.readTy))
+                                seenTablePropPairs.erase(pair1);
-                                {
+                                seenTablePropPairs.erase(pair2);
-                                    seenSet.erase(*hprop.readTy);
-                                    seenSet.erase(*tprop.readTy);
                                 return {builtinTypes->neverType};
                             }
                             else
                             {
-                                    seenSet.insert(*hprop.readTy);
+                                seenTablePropPairs.insert(pair1);
-                                    seenSet.insert(*tprop.readTy);
+                                seenTablePropPairs.insert(pair2);
-                                }
                             }
 
-                            NormalizationResult res = isIntersectionInhabited(*hprop.readTy, *tprop.readTy);
+                            // FIXME(ariel): this is being added in a flag removal, so not changing the semantics here, but worth noting that this
+                            // fresh `seenSet` is definitely a bug. we already have `seenSet` from the parameter that _should_ have been used here.
+                            Set<TypeId> seenSet{nullptr};
+                            NormalizationResult res = isIntersectionInhabited(*hprop.readTy, *tprop.readTy, seenTablePropPairs, seenSet);
 
-                            // Cleanup
+                            seenTablePropPairs.erase(pair1);
-                            if (fixCyclicTablesBlowingStack())
+                            seenTablePropPairs.erase(pair2);
-                            {
+                            if (NormalizationResult::True != res)
-                                seenSet.erase(*hprop.readTy);
-                                seenSet.erase(*tprop.readTy);
-                            }
-
-                            if (normalizeAwayUninhabitableTables() && NormalizationResult::True != res)
                                 return {builtinTypes->neverType};
-                        }
-                        else
-                        {
-                            if (normalizeAwayUninhabitableTables() &&
-                                NormalizationResult::False == isIntersectionInhabited(*hprop.readTy, *tprop.readTy))
-                                return {builtinTypes->neverType};
-                        }
 
                             TypeId ty = simplifyIntersection(builtinTypes, NotNull{arena}, *hprop.readTy, *tprop.readTy).result;
                             prop.readTy = ty;
                             hereSubThere &= (ty == hprop.readTy);
                             thereSubHere &= (ty == tprop.readTy);
                         }
+                    }
                     else
                     {
                         prop.readTy = *hprop.readTy;
@@ -2737,7 +2759,7 @@ std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there
     if (tmtable && hmtable)
     {
         // NOTE: this assumes metatables are ivariant
-        if (std::optional<TypeId> mtable = intersectionOfTables(hmtable, tmtable, seenSet))
+        if (std::optional<TypeId> mtable = intersectionOfTables(hmtable, tmtable, seenTablePropPairs, seenSet))
         {
             if (table == htable && *mtable == hmtable)
                 return here;
@@ -2767,12 +2789,12 @@ std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there
         return table;
 }
 
-void Normalizer::intersectTablesWithTable(TypeIds& heres, TypeId there, Set<TypeId>& seenSetTypes)
+void Normalizer::intersectTablesWithTable(TypeIds& heres, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSetTypes)
 {
     TypeIds tmp;
     for (TypeId here : heres)
     {
-        if (std::optional<TypeId> inter = intersectionOfTables(here, there, seenSetTypes))
+        if (std::optional<TypeId> inter = intersectionOfTables(here, there, seenTablePropPairs, seenSetTypes))
             tmp.insert(*inter);
     }
     heres.retain(tmp);
@@ -2787,7 +2809,8 @@ void Normalizer::intersectTables(TypeIds& heres, const TypeIds& theres)
         for (TypeId there : theres)
         {
             Set<TypeId> seenSetTypes{nullptr};
-            if (std::optional<TypeId> inter = intersectionOfTables(here, there, seenSetTypes))
+            SeenTablePropPairs seenTablePropPairs{{nullptr, nullptr}};
+            if (std::optional<TypeId> inter = intersectionOfTables(here, there, seenTablePropPairs, seenSetTypes))
                 tmp.insert(*inter);
         }
     }
@@ -3005,12 +3028,17 @@ void Normalizer::intersectFunctions(NormalizedFunctionType& heres, const Normali
     }
 }
 
-NormalizationResult Normalizer::intersectTyvarsWithTy(NormalizedTyvars& here, TypeId there, Set<TypeId>& seenSetTypes)
+NormalizationResult Normalizer::intersectTyvarsWithTy(
+    NormalizedTyvars& here,
+    TypeId there,
+    SeenTablePropPairs& seenTablePropPairs,
+    Set<TypeId>& seenSetTypes
+)
 {
     for (auto it = here.begin(); it != here.end();)
     {
         NormalizedType& inter = *it->second;
-        NormalizationResult res = intersectNormalWithTy(inter, there, seenSetTypes);
+        NormalizationResult res = intersectNormalWithTy(inter, there, seenTablePropPairs, seenSetTypes);
         if (res != NormalizationResult::True)
             return res;
         if (isShallowInhabited(inter))
@@ -3024,6 +3052,10 @@ NormalizationResult Normalizer::intersectTyvarsWithTy(NormalizedTyvars& here, Ty
 // See above for an explaination of `ignoreSmallerTyvars`.
 NormalizationResult Normalizer::intersectNormals(NormalizedType& here, const NormalizedType& there, int ignoreSmallerTyvars)
 {
+    RecursionCounter _rc(&sharedState->counters.recursionCount);
+    if (!withinResourceLimits())
+        return NormalizationResult::HitLimits;
+
     if (!get<NeverType>(there.tops))
     {
         here.tops = intersectionOfTops(here.tops, there.tops);
@@ -3035,6 +3067,11 @@ NormalizationResult Normalizer::intersectNormals(NormalizedType& here, const Nor
         return unionNormals(here, there, ignoreSmallerTyvars);
     }
 
+    // Limit based on worst-case expansion of the table intersection
+    // 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;
+
     here.booleans = intersectionOfBools(here.booleans, there.booleans);
 
     intersectClasses(here.classes, there.classes);
@@ -3088,7 +3125,12 @@ NormalizationResult Normalizer::intersectNormals(NormalizedType& here, const Nor
     return NormalizationResult::True;
 }
 
-NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, TypeId there, Set<TypeId>& seenSetTypes)
+NormalizationResult Normalizer::intersectNormalWithTy(
+    NormalizedType& here,
+    TypeId there,
+    SeenTablePropPairs& seenTablePropPairs,
+    Set<TypeId>& seenSetTypes
+)
 {
     RecursionCounter _rc(&sharedState->counters.recursionCount);
     if (!withinResourceLimits())
@@ -3104,14 +3146,14 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
     else if (!get<NeverType>(here.tops))
     {
         clearNormal(here);
-        return unionNormalWithTy(here, there, seenSetTypes);
+        return unionNormalWithTy(here, there, seenTablePropPairs, seenSetTypes);
     }
     else if (const UnionType* utv = get<UnionType>(there))
     {
         NormalizedType norm{builtinTypes};
         for (UnionTypeIterator it = begin(utv); it != end(utv); ++it)
         {
-            NormalizationResult res = unionNormalWithTy(norm, *it, seenSetTypes);
+            NormalizationResult res = unionNormalWithTy(norm, *it, seenTablePropPairs, seenSetTypes);
             if (res != NormalizationResult::True)
                 return res;
         }
@@ -3121,13 +3163,14 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
     {
         for (IntersectionTypeIterator it = begin(itv); it != end(itv); ++it)
         {
-            NormalizationResult res = intersectNormalWithTy(here, *it, seenSetTypes);
+            NormalizationResult res = intersectNormalWithTy(here, *it, seenTablePropPairs, seenSetTypes);
             if (res != NormalizationResult::True)
                 return res;
         }
         return NormalizationResult::True;
     }
-    else if (get<GenericType>(there) || get<FreeType>(there) || get<BlockedType>(there) || get<PendingExpansionType>(there) || get<TypeFunctionInstanceType>(there))
+    else if (get<GenericType>(there) || get<FreeType>(there) || get<BlockedType>(there) || get<PendingExpansionType>(there) ||
+             get<TypeFunctionInstanceType>(there))
     {
         NormalizedType thereNorm{builtinTypes};
         NormalizedType topNorm{builtinTypes};
@@ -3150,7 +3193,7 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
     {
         TypeIds tables = std::move(here.tables);
         clearNormal(here);
-        intersectTablesWithTable(tables, there, seenSetTypes);
+        intersectTablesWithTable(tables, there, seenTablePropPairs, seenSetTypes);
         here.tables = std::move(tables);
     }
     else if (get<ClassType>(there))
@@ -3243,13 +3286,18 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
             // assumption that it is the same as any.
             return NormalizationResult::True;
         }
+        else if (get<NoRefineType>(t))
+        {
+            // `*no-refine*` means we will never do anything to affect the intersection.
+            return NormalizationResult::True;
+        }
         else if (get<NeverType>(t))
         {
             // if we're intersecting with `~never`, this is equivalent to intersecting with `unknown`
             // this is a noop since an intersection with `unknown` is trivial.
             return NormalizationResult::True;
         }
-        else if ((FFlag::LuauNormalizeNotUnknownIntersection || FFlag::LuauSolverV2) && get<UnknownType>(t))
+        else if (get<UnknownType>(t))
         {
             // if we're intersecting with `~unknown`, this is equivalent to intersecting with `never`
             // this means we should clear the type entirely.
@@ -3257,7 +3305,7 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
             return NormalizationResult::True;
         }
         else if (auto nt = get<NegationType>(t))
-            return intersectNormalWithTy(here, nt->ty, seenSetTypes);
+            return intersectNormalWithTy(here, nt->ty, seenTablePropPairs, seenSetTypes);
         else
         {
             // TODO negated unions, intersections, table, and function.
@@ -3269,10 +3317,15 @@ NormalizationResult Normalizer::intersectNormalWithTy(NormalizedType& here, Type
     {
         here.classes.resetToNever();
     }
+    else if (get<NoRefineType>(there))
+    {
+        // `*no-refine*` means we will never do anything to affect the intersection.
+        return NormalizationResult::True;
+    }
     else
         LUAU_ASSERT(!"Unreachable");
 
-    NormalizationResult res = intersectTyvarsWithTy(tyvars, there, seenSetTypes);
+    NormalizationResult res = intersectTyvarsWithTy(tyvars, there, seenTablePropPairs, seenSetTypes);
     if (res != NormalizationResult::True)
         return res;
     here.tyvars = std::move(tyvars);
@@ -3420,16 +3473,27 @@ TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
         return arena->addType(UnionType{std::move(result)});
 }
 
-bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice)
+bool isSubtype(
+    TypeId subTy,
+    TypeId superTy,
+    NotNull<Scope> scope,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    InternalErrorReporter& ice
+)
 {
     UnifierSharedState sharedState{&ice};
     TypeArena arena;
     Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
+    TypeCheckLimits limits;
+    TypeFunctionRuntime typeFunctionRuntime{
+        NotNull{&ice}, NotNull{&limits}
+    }; // TODO: maybe subtyping checks should not invoke user-defined type function runtime
 
     // Subtyping under DCR is not implemented using unification!
     if (FFlag::LuauSolverV2)
     {
-        Subtyping subtyping{builtinTypes, NotNull{&arena}, NotNull{&normalizer}, NotNull{&ice}};
+        Subtyping subtyping{builtinTypes, NotNull{&arena}, simplifier, NotNull{&normalizer}, NotNull{&typeFunctionRuntime}, NotNull{&ice}};
 
         return subtyping.isSubtype(subTy, superTy, scope).isSubtype;
     }
@@ -3442,16 +3506,27 @@ bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<Built
     }
 }
 
-bool isSubtype(TypePackId subPack, TypePackId superPack, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice)
+bool isSubtype(
+    TypePackId subPack,
+    TypePackId superPack,
+    NotNull<Scope> scope,
+    NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    InternalErrorReporter& ice
+)
 {
     UnifierSharedState sharedState{&ice};
     TypeArena arena;
     Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
+    TypeCheckLimits limits;
+    TypeFunctionRuntime typeFunctionRuntime{
+        NotNull{&ice}, NotNull{&limits}
+    }; // TODO: maybe subtyping checks should not invoke user-defined type function runtime
 
     // Subtyping under DCR is not implemented using unification!
     if (FFlag::LuauSolverV2)
     {
-        Subtyping subtyping{builtinTypes, NotNull{&arena}, NotNull{&normalizer}, NotNull{&ice}};
+        Subtyping subtyping{builtinTypes, NotNull{&arena}, simplifier, NotNull{&normalizer}, NotNull{&typeFunctionRuntime}, NotNull{&ice}};
 
         return subtyping.isSubtype(subPack, superPack, scope).isSubtype;
     }
@@ -3464,38 +3539,4 @@ bool isSubtype(TypePackId subPack, TypePackId superPack, NotNull<Scope> scope, N
     }
 }
 
-bool isConsistentSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<BuiltinTypes> builtinTypes, InternalErrorReporter& ice)
-{
-    LUAU_ASSERT(!FFlag::LuauSolverV2);
-
-    UnifierSharedState sharedState{&ice};
-    TypeArena arena;
-    Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
-    Unifier u{NotNull{&normalizer}, scope, Location{}, Covariant};
-
-    u.tryUnify(subTy, superTy);
-    const bool ok = u.errors.empty() && u.log.empty();
-    return ok;
-}
-
-bool isConsistentSubtype(
-    TypePackId subPack,
-    TypePackId superPack,
-    NotNull<Scope> scope,
-    NotNull<BuiltinTypes> builtinTypes,
-    InternalErrorReporter& ice
-)
-{
-    LUAU_ASSERT(!FFlag::LuauSolverV2);
-
-    UnifierSharedState sharedState{&ice};
-    TypeArena arena;
-    Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
-    Unifier u{NotNull{&normalizer}, scope, Location{}, Covariant};
-
-    u.tryUnify(subPack, superPack);
-    const bool ok = u.errors.empty() && u.log.empty();
-    return ok;
-}
-
 } // namespace Luau

Analysis/src/OverloadResolution.cpp

@@ -16,7 +16,9 @@ namespace Luau
 OverloadResolver::OverloadResolver(
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<TypeArena> arena,
+    NotNull<Simplifier> simplifier,
     NotNull<Normalizer> normalizer,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<Scope> scope,
     NotNull<InternalErrorReporter> reporter,
     NotNull<TypeCheckLimits> limits,
@@ -24,11 +26,13 @@ OverloadResolver::OverloadResolver(
 )
     : builtinTypes(builtinTypes)
     , arena(arena)
+    , simplifier(simplifier)
     , normalizer(normalizer)
+    , typeFunctionRuntime(typeFunctionRuntime)
     , scope(scope)
     , ice(reporter)
     , limits(limits)
-    , subtyping({builtinTypes, arena, normalizer, ice})
+    , subtyping({builtinTypes, arena, simplifier, normalizer, typeFunctionRuntime, ice})
     , callLoc(callLocation)
 {
 }
@@ -199,8 +203,9 @@ std::pair<OverloadResolver::Analysis, ErrorVec> OverloadResolver::checkOverload_
     const std::vector<AstExpr*>* argExprs
 )
 {
-    FunctionGraphReductionResult result =
+    FunctionGraphReductionResult result = reduceTypeFunctions(
-        reduceTypeFunctions(fnTy, callLoc, TypeFunctionContext{arena, builtinTypes, scope, normalizer, ice, limits}, /*force=*/true);
+        fnTy, callLoc, TypeFunctionContext{arena, builtinTypes, scope, simplifier, normalizer, typeFunctionRuntime, ice, limits}, /*force=*/true
+    );
     if (!result.errors.empty())
         return {OverloadIsNonviable, result.errors};
 
@@ -401,10 +406,12 @@ void OverloadResolver::add(Analysis analysis, TypeId ty, ErrorVec&& errors)
 
 // we wrap calling the overload resolver in a separate function to reduce overall stack pressure in `solveFunctionCall`.
 // this limits the lifetime of `OverloadResolver`, a large type, to only as long as it is actually needed.
-std::optional<TypeId> selectOverload(
+static std::optional<TypeId> selectOverload(
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<TypeArena> arena,
+    NotNull<Simplifier> simplifier,
     NotNull<Normalizer> normalizer,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<Scope> scope,
     NotNull<InternalErrorReporter> iceReporter,
     NotNull<TypeCheckLimits> limits,
@@ -413,8 +420,9 @@ std::optional<TypeId> selectOverload(
     TypePackId argsPack
 )
 {
-    OverloadResolver resolver{builtinTypes, arena, normalizer, scope, iceReporter, limits, location};
+    auto resolver =
-    auto [status, overload] = resolver.selectOverload(fn, argsPack);
+        std::make_unique<OverloadResolver>(builtinTypes, arena, simplifier, normalizer, typeFunctionRuntime, scope, iceReporter, limits, location);
+    auto [status, overload] = resolver->selectOverload(fn, argsPack);
 
     if (status == OverloadResolver::Analysis::Ok)
         return overload;
@@ -428,7 +436,9 @@ std::optional<TypeId> selectOverload(
 SolveResult solveFunctionCall(
     NotNull<TypeArena> arena,
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
     NotNull<Normalizer> normalizer,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<InternalErrorReporter> iceReporter,
     NotNull<TypeCheckLimits> limits,
     NotNull<Scope> scope,
@@ -437,7 +447,8 @@ SolveResult solveFunctionCall(
     TypePackId argsPack
 )
 {
-    std::optional<TypeId> overloadToUse = selectOverload(builtinTypes, arena, normalizer, scope, iceReporter, limits, location, fn, argsPack);
+    std::optional<TypeId> overloadToUse =
+        selectOverload(builtinTypes, arena, simplifier, normalizer, typeFunctionRuntime, scope, iceReporter, limits, location, fn, argsPack);
     if (!overloadToUse)
         return {SolveResult::NoMatchingOverload};
 
@@ -450,9 +461,9 @@ SolveResult solveFunctionCall(
 
     if (!u2.genericSubstitutions.empty() || !u2.genericPackSubstitutions.empty())
     {
-        Instantiation2 instantiation{arena, std::move(u2.genericSubstitutions), std::move(u2.genericPackSubstitutions)};
+        auto instantiation = std::make_unique<Instantiation2>(arena, std::move(u2.genericSubstitutions), std::move(u2.genericPackSubstitutions));
 
-        std::optional<TypePackId> subst = instantiation.substitute(resultPack);
+        std::optional<TypePackId> subst = instantiation->substitute(resultPack);
 
         if (!subst)
             return {SolveResult::CodeTooComplex};

Analysis/src/RequireTracer.cpp

@@ -4,6 +4,8 @@
 #include "Luau/Ast.h"
 #include "Luau/Module.h"
 
+LUAU_FASTFLAGVARIABLE(LuauExtendedSimpleRequire)
+
 namespace Luau
 {
 
@@ -65,7 +67,7 @@ struct RequireTracer : AstVisitor
         return true;
     }
 
-    AstExpr* getDependent(AstExpr* node)
+    AstExpr* getDependent_DEPRECATED(AstExpr* node)
     {
         if (AstExprLocal* expr = node->as<AstExprLocal>())
             return locals[expr->local];
@@ -78,11 +80,34 @@ struct RequireTracer : AstVisitor
         else
             return nullptr;
     }
+    AstNode* getDependent(AstNode* node)
+    {
+        if (AstExprLocal* expr = node->as<AstExprLocal>())
+            return locals[expr->local];
+        else if (AstExprIndexName* expr = node->as<AstExprIndexName>())
+            return expr->expr;
+        else if (AstExprIndexExpr* expr = node->as<AstExprIndexExpr>())
+            return expr->expr;
+        else if (AstExprCall* expr = node->as<AstExprCall>(); expr && expr->self)
+            return expr->func->as<AstExprIndexName>()->expr;
+        else if (AstExprGroup* expr = node->as<AstExprGroup>())
+            return expr->expr;
+        else if (AstExprTypeAssertion* expr = node->as<AstExprTypeAssertion>())
+            return expr->annotation;
+        else if (AstTypeGroup* expr = node->as<AstTypeGroup>())
+            return expr->type;
+        else if (AstTypeTypeof* expr = node->as<AstTypeTypeof>())
+            return expr->expr;
+        else
+            return nullptr;
+    }
 
     void process()
     {
         ModuleInfo moduleContext{currentModuleName};
 
+        if (FFlag::LuauExtendedSimpleRequire)
+        {
             // seed worklist with require arguments
             work.reserve(requireCalls.size());
 
@@ -91,13 +116,15 @@ struct RequireTracer : AstVisitor
 
             // 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 (AstExpr* dep = getDependent(work[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)
             {
-            AstExpr* expr = work[i - 1];
+                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))
@@ -105,7 +132,53 @@ struct RequireTracer : AstVisitor
 
                 std::optional<ModuleInfo> info;
 
-            if (AstExpr* dep = getDependent(expr))
+                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
+        {
+            // seed worklist with require arguments
+            work_DEPRECATED.reserve(requireCalls.size());
+
+            for (AstExprCall* require : requireCalls)
+                work_DEPRECATED.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_DEPRECATED.size(); ++i)
+                if (AstExpr* dep = getDependent_DEPRECATED(work_DEPRECATED[i]))
+                    work_DEPRECATED.push_back(dep);
+
+            // resolve all expressions to a module info
+            for (size_t i = work_DEPRECATED.size(); i > 0; --i)
+            {
+                AstExpr* expr = work_DEPRECATED[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 (AstExpr* dep = getDependent_DEPRECATED(expr))
                 {
                     const ModuleInfo* context = result.exprs.find(dep);
 
@@ -123,6 +196,7 @@ struct RequireTracer : AstVisitor
                 if (info)
                     result.exprs[expr] = std::move(*info);
             }
+        }
 
         // resolve all requires according to their argument
         result.requireList.reserve(requireCalls.size());
@@ -150,7 +224,8 @@ struct RequireTracer : AstVisitor
     ModuleName currentModuleName;
 
     DenseHashMap<AstLocal*, AstExpr*> locals;
-    std::vector<AstExpr*> work;
+    std::vector<AstExpr*> work_DEPRECATED;
+    std::vector<AstNode*> work;
     std::vector<AstExprCall*> requireCalls;
 };
 

Analysis/src/Scope.cpp

@@ -211,6 +211,16 @@ void Scope::inheritRefinements(const ScopePtr& childScope)
     }
 }
 
+bool Scope::shouldWarnGlobal(std::string name) const
+{
+    for (const Scope* current = this; current; current = current->parent.get())
+    {
+        if (current->globalsToWarn.contains(name))
+            return true;
+    }
+    return false;
+}
+
 bool subsumesStrict(Scope* left, Scope* right)
 {
     while (right)

Analysis/src/Simplify.cpp

@@ -2,6 +2,7 @@
 
 #include "Luau/Simplify.h"
 
+#include "Luau/Common.h"
 #include "Luau/DenseHash.h"
 #include "Luau/RecursionCounter.h"
 #include "Luau/Set.h"
@@ -14,6 +15,7 @@
 LUAU_FASTINT(LuauTypeReductionRecursionLimit)
 LUAU_FASTFLAG(LuauSolverV2)
 LUAU_DYNAMIC_FASTINTVARIABLE(LuauSimplificationComplexityLimit, 8);
+LUAU_FASTFLAGVARIABLE(LuauFlagBasicIntersectFollows);
 
 namespace Luau
 {
@@ -29,16 +31,16 @@ struct TypeSimplifier
 
     int recursionDepth = 0;
 
-    TypeId mkNegation(TypeId ty);
+    TypeId mkNegation(TypeId ty) const;
 
     TypeId intersectFromParts(std::set<TypeId> parts);
 
-    TypeId intersectUnionWithType(TypeId unionTy, TypeId right);
+    TypeId intersectUnionWithType(TypeId left, TypeId right);
     TypeId intersectUnions(TypeId left, TypeId right);
-    TypeId intersectNegatedUnion(TypeId unionTy, TypeId right);
+    TypeId intersectNegatedUnion(TypeId left, TypeId right);
 
-    TypeId intersectTypeWithNegation(TypeId a, TypeId b);
+    TypeId intersectTypeWithNegation(TypeId left, TypeId right);
-    TypeId intersectNegations(TypeId a, TypeId b);
+    TypeId intersectNegations(TypeId left, TypeId right);
 
     TypeId intersectIntersectionWithType(TypeId left, TypeId right);
 
@@ -46,8 +48,8 @@ struct TypeSimplifier
     // unions, intersections, or negations.
     std::optional<TypeId> basicIntersect(TypeId left, TypeId right);
 
-    TypeId intersect(TypeId ty, TypeId discriminant);
+    TypeId intersect(TypeId left, TypeId right);
-    TypeId union_(TypeId ty, TypeId discriminant);
+    TypeId union_(TypeId left, TypeId right);
 
     TypeId simplify(TypeId ty);
     TypeId simplify(TypeId ty, DenseHashSet<TypeId>& seen);
@@ -571,7 +573,7 @@ Relation relate(TypeId left, TypeId right)
     return relate(left, right, seen);
 }
 
-TypeId TypeSimplifier::mkNegation(TypeId ty)
+TypeId TypeSimplifier::mkNegation(TypeId ty) const
 {
     TypeId result = nullptr;
 
@@ -1064,6 +1066,12 @@ TypeId TypeSimplifier::intersectIntersectionWithType(TypeId left, TypeId right)
 
 std::optional<TypeId> TypeSimplifier::basicIntersect(TypeId left, TypeId right)
 {
+    if (FFlag::LuauFlagBasicIntersectFollows)
+    {
+        left = follow(left);
+        right = follow(right);
+    }
+
     if (get<AnyType>(left) && get<ErrorType>(right))
         return right;
     if (get<AnyType>(right) && get<ErrorType>(left))
@@ -1403,8 +1411,6 @@ TypeId TypeSimplifier::simplify(TypeId ty, DenseHashSet<TypeId>& seen)
 
 SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId left, TypeId right)
 {
-    LUAU_ASSERT(FFlag::LuauSolverV2);
-
     TypeSimplifier s{builtinTypes, arena};
 
     // fprintf(stderr, "Intersect %s and %s ...\n", toString(left).c_str(), toString(right).c_str());
@@ -1418,8 +1424,6 @@ SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<
 
 SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, std::set<TypeId> parts)
 {
-    LUAU_ASSERT(FFlag::LuauSolverV2);
-
     TypeSimplifier s{builtinTypes, arena};
 
     TypeId res = s.intersectFromParts(std::move(parts));
@@ -1429,8 +1433,6 @@ SimplifyResult simplifyIntersection(NotNull<BuiltinTypes> builtinTypes, NotNull<
 
 SimplifyResult simplifyUnion(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId left, TypeId right)
 {
-    LUAU_ASSERT(FFlag::LuauSolverV2);
-
     TypeSimplifier s{builtinTypes, arena};
 
     TypeId res = s.union_(left, right);

Analysis/src/Substitution.cpp

@@ -4,13 +4,15 @@
 #include "Luau/Common.h"
 #include "Luau/Clone.h"
 #include "Luau/TxnLog.h"
+#include "Luau/Type.h"
 
 #include <algorithm>
 #include <stdexcept>
 
 LUAU_FASTINTVARIABLE(LuauTarjanChildLimit, 10000)
-LUAU_FASTFLAG(LuauSolverV2);
+LUAU_FASTFLAG(LuauSolverV2)
-LUAU_FASTINTVARIABLE(LuauTarjanPreallocationSize, 256);
+LUAU_FASTINTVARIABLE(LuauTarjanPreallocationSize, 256)
+LUAU_FASTFLAG(LuauSyntheticErrors)
 
 namespace Luau
 {
@@ -50,11 +52,33 @@ static TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool a
             LUAU_ASSERT(ty->persistent);
             return ty;
         }
-        else if constexpr (std::is_same_v<T, ErrorType>)
+        else if constexpr (std::is_same_v<T, NoRefineType>)
         {
             LUAU_ASSERT(ty->persistent);
             return ty;
         }
+        else if constexpr (std::is_same_v<T, ErrorType>)
+        {
+            if (FFlag::LuauSyntheticErrors)
+            {
+                LUAU_ASSERT(ty->persistent || a.synthetic);
+
+                if (ty->persistent)
+                    return ty;
+
+                // While this code intentionally works (and clones) even if `a.synthetic` is `std::nullopt`,
+                // we still assert above because we consider it a bug to have a non-persistent error type
+                // without any associated metadata. We should always use the persistent version in such cases.
+                ErrorType clone = ErrorType{};
+                clone.synthetic = a.synthetic;
+                return dest.addType(clone);
+            }
+            else
+            {
+                LUAU_ASSERT(ty->persistent);
+                return ty;
+            }
+        }
         else if constexpr (std::is_same_v<T, UnknownType>)
         {
             LUAU_ASSERT(ty->persistent);
@@ -74,9 +98,7 @@ static TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool a
             FunctionType clone = FunctionType{a.level, a.scope, a.argTypes, a.retTypes, a.definition, a.hasSelf};
             clone.generics = a.generics;
             clone.genericPacks = a.genericPacks;
-            clone.magicFunction = a.magicFunction;
+            clone.magic = a.magic;
-            clone.dcrMagicFunction = a.dcrMagicFunction;
-            clone.dcrMagicRefinement = a.dcrMagicRefinement;
             clone.tags = a.tags;
             clone.argNames = a.argNames;
             clone.isCheckedFunction = a.isCheckedFunction;
@@ -127,7 +149,7 @@ static TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool a
             return dest.addType(NegationType{a.ty});
         else if constexpr (std::is_same_v<T, TypeFunctionInstanceType>)
         {
-            TypeFunctionInstanceType clone{a.function, a.typeArguments, a.packArguments, a.userFuncName, a.userFuncBody};
+            TypeFunctionInstanceType clone{a.function, a.typeArguments, a.packArguments, a.userFuncName, a.userFuncData};
             return dest.addType(std::move(clone));
         }
         else

Analysis/src/Subtyping.cpp

@@ -5,6 +5,7 @@
 #include "Luau/Common.h"
 #include "Luau/Error.h"
 #include "Luau/Normalize.h"
+#include "Luau/RecursionCounter.h"
 #include "Luau/Scope.h"
 #include "Luau/StringUtils.h"
 #include "Luau/Substitution.h"
@@ -20,7 +21,8 @@
 
 #include <algorithm>
 
-LUAU_FASTFLAGVARIABLE(DebugLuauSubtypingCheckPathValidity, false);
+LUAU_FASTFLAGVARIABLE(DebugLuauSubtypingCheckPathValidity)
+LUAU_FASTFLAGVARIABLE(LuauSubtypingFixTailPack)
 
 namespace Luau
 {
@@ -258,43 +260,32 @@ SubtypingResult SubtypingResult::any(const std::vector<SubtypingResult>& results
 
 struct ApplyMappedGenerics : Substitution
 {
-    using MappedGenerics = DenseHashMap<TypeId, SubtypingEnvironment::GenericBounds>;
-    using MappedGenericPacks = DenseHashMap<TypePackId, TypePackId>;
-
     NotNull<BuiltinTypes> builtinTypes;
     NotNull<TypeArena> arena;
 
-    MappedGenerics& mappedGenerics;
+    SubtypingEnvironment& env;
-    MappedGenericPacks& mappedGenericPacks;
 
-
+    ApplyMappedGenerics(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, SubtypingEnvironment& env)
-    ApplyMappedGenerics(
-        NotNull<BuiltinTypes> builtinTypes,
-        NotNull<TypeArena> arena,
-        MappedGenerics& mappedGenerics,
-        MappedGenericPacks& mappedGenericPacks
-    )
         : Substitution(TxnLog::empty(), arena)
         , builtinTypes(builtinTypes)
         , arena(arena)
-        , mappedGenerics(mappedGenerics)
+        , env(env)
-        , mappedGenericPacks(mappedGenericPacks)
     {
     }
 
     bool isDirty(TypeId ty) override
     {
-        return mappedGenerics.contains(ty);
+        return env.containsMappedType(ty);
     }
 
     bool isDirty(TypePackId tp) override
     {
-        return mappedGenericPacks.contains(tp);
+        return env.containsMappedPack(tp);
     }
 
     TypeId clean(TypeId ty) override
     {
-        const auto& bounds = mappedGenerics[ty];
+        const auto& bounds = env.getMappedTypeBounds(ty);
 
         if (bounds.upperBound.empty())
             return builtinTypes->unknownType;
@@ -307,7 +298,12 @@ struct ApplyMappedGenerics : Substitution
 
     TypePackId clean(TypePackId tp) override
     {
-        return mappedGenericPacks[tp];
+        if (auto it = env.getMappedPackBounds(tp))
+            return *it;
+
+        // Clean is only called when isDirty found a pack bound
+        LUAU_ASSERT(!"Unreachable");
+        return nullptr;
     }
 
     bool ignoreChildren(TypeId ty) override
@@ -325,19 +321,91 @@ struct ApplyMappedGenerics : Substitution
 
 std::optional<TypeId> SubtypingEnvironment::applyMappedGenerics(NotNull<BuiltinTypes> builtinTypes, NotNull<TypeArena> arena, TypeId ty)
 {
-    ApplyMappedGenerics amg{builtinTypes, arena, mappedGenerics, mappedGenericPacks};
+    ApplyMappedGenerics amg{builtinTypes, arena, *this};
     return amg.substitute(ty);
 }
 
+const TypeId* SubtypingEnvironment::tryFindSubstitution(TypeId ty) const
+{
+    if (auto it = substitutions.find(ty))
+        return it;
+
+    if (parent)
+        return parent->tryFindSubstitution(ty);
+
+    return nullptr;
+}
+
+const SubtypingResult* SubtypingEnvironment::tryFindSubtypingResult(std::pair<TypeId, TypeId> subAndSuper) const
+{
+    if (auto it = ephemeralCache.find(subAndSuper))
+        return it;
+
+    if (parent)
+        return parent->tryFindSubtypingResult(subAndSuper);
+
+    return nullptr;
+}
+
+bool SubtypingEnvironment::containsMappedType(TypeId ty) const
+{
+    if (mappedGenerics.contains(ty))
+        return true;
+
+    if (parent)
+        return parent->containsMappedType(ty);
+
+    return false;
+}
+
+bool SubtypingEnvironment::containsMappedPack(TypePackId tp) const
+{
+    if (mappedGenericPacks.contains(tp))
+        return true;
+
+    if (parent)
+        return parent->containsMappedPack(tp);
+
+    return false;
+}
+
+SubtypingEnvironment::GenericBounds& SubtypingEnvironment::getMappedTypeBounds(TypeId ty)
+{
+    if (auto it = mappedGenerics.find(ty))
+        return *it;
+
+    if (parent)
+        return parent->getMappedTypeBounds(ty);
+
+    LUAU_ASSERT(!"Use containsMappedType before asking for bounds!");
+    return mappedGenerics[ty];
+}
+
+TypePackId* SubtypingEnvironment::getMappedPackBounds(TypePackId tp)
+{
+    if (auto it = mappedGenericPacks.find(tp))
+        return it;
+
+    if (parent)
+        return parent->getMappedPackBounds(tp);
+
+    // This fallback is reachable in valid cases, unlike the final part of getMappedTypeBounds
+    return nullptr;
+}
+
 Subtyping::Subtyping(
     NotNull<BuiltinTypes> builtinTypes,
     NotNull<TypeArena> typeArena,
+    NotNull<Simplifier> simplifier,
     NotNull<Normalizer> normalizer,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<InternalErrorReporter> iceReporter
 )
     : builtinTypes(builtinTypes)
     , arena(typeArena)
+    , simplifier(simplifier)
     , normalizer(normalizer)
+    , typeFunctionRuntime(typeFunctionRuntime)
     , iceReporter(iceReporter)
 {
 }
@@ -379,7 +447,10 @@ SubtypingResult Subtyping::isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope
             result.isSubtype = false;
         }
 
-        SubtypingResult boundsResult = isCovariantWith(env, lowerBound, upperBound, scope);
+
+        SubtypingEnvironment boundsEnv;
+        boundsEnv.parent = &env;
+        SubtypingResult boundsResult = isCovariantWith(boundsEnv, lowerBound, upperBound, scope);
         boundsResult.reasoning.clear();
 
         result.andAlso(boundsResult);
@@ -442,20 +513,30 @@ struct SeenSetPopper
 
 SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypeId subTy, TypeId superTy, NotNull<Scope> scope)
 {
+    UnifierCounters& counters = normalizer->sharedState->counters;
+    RecursionCounter rc(&counters.recursionCount);
+
+    if (counters.recursionLimit > 0 && counters.recursionLimit < counters.recursionCount)
+    {
+        SubtypingResult result;
+        result.normalizationTooComplex = true;
+        return result;
+    }
+
     subTy = follow(subTy);
     superTy = follow(superTy);
 
-    if (TypeId* subIt = env.substitutions.find(subTy); subIt && *subIt)
+    if (const TypeId* subIt = env.tryFindSubstitution(subTy); subIt && *subIt)
         subTy = *subIt;
 
-    if (TypeId* superIt = env.substitutions.find(superTy); superIt && *superIt)
+    if (const TypeId* superIt = env.tryFindSubstitution(superTy); superIt && *superIt)
         superTy = *superIt;
 
-    SubtypingResult* cachedResult = resultCache.find({subTy, superTy});
+    const SubtypingResult* cachedResult = resultCache.find({subTy, superTy});
     if (cachedResult)
         return *cachedResult;
 
-    cachedResult = env.ephemeralCache.find({subTy, superTy});
+    cachedResult = env.tryFindSubtypingResult({subTy, superTy});
     if (cachedResult)
         return *cachedResult;
 
@@ -700,7 +781,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
                     std::vector<TypeId> headSlice(begin(superHead), begin(superHead) + headSize);
                     TypePackId superTailPack = arena->addTypePack(std::move(headSlice), superTail);
 
-                    if (TypePackId* other = env.mappedGenericPacks.find(*subTail))
+                    if (TypePackId* other = env.getMappedPackBounds(*subTail))
                         // TODO: TypePath can't express "slice of a pack + its tail".
                         results.push_back(isCovariantWith(env, *other, superTailPack, scope).withSubComponent(TypePath::PackField::Tail));
                     else
@@ -755,7 +836,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
                     std::vector<TypeId> headSlice(begin(subHead), begin(subHead) + headSize);
                     TypePackId subTailPack = arena->addTypePack(std::move(headSlice), subTail);
 
-                    if (TypePackId* other = env.mappedGenericPacks.find(*superTail))
+                    if (TypePackId* other = env.getMappedPackBounds(*superTail))
                         // TODO: TypePath can't express "slice of a pack + its tail".
                         results.push_back(isContravariantWith(env, subTailPack, *other, scope).withSuperComponent(TypePath::PackField::Tail));
                     else
@@ -778,7 +859,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, TypePackId
             else
                 return SubtypingResult{false}
                     .withSuperComponent(TypePath::PackField::Tail)
-                    .withError({scope->location, UnexpectedTypePackInSubtyping{*subTail}});
+                    .withError({scope->location, UnexpectedTypePackInSubtyping{FFlag::LuauSubtypingFixTailPack ? *superTail : *subTail}});
         }
         else
             return {false};
@@ -1316,6 +1397,7 @@ SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const Tabl
 SubtypingResult Subtyping::isCovariantWith(SubtypingEnvironment& env, const MetatableType* subMt, const MetatableType* superMt, NotNull<Scope> scope)
 {
     return isCovariantWith(env, subMt->table, superMt->table, scope)
+        .withBothComponent(TypePath::TypeField::Table)
         .andAlso(isCovariantWith(env, subMt->metatable, superMt->metatable, scope).withBothComponent(TypePath::TypeField::Metatable));
 }
 
@@ -1389,6 +1471,19 @@ SubtypingResult Subtyping::isCovariantWith(
         result.orElse(
             isContravariantWith(env, subFunction->argTypes, superFunction->argTypes, scope).withBothComponent(TypePath::PackField::Arguments)
         );
+
+        // If subtyping failed in the argument packs, we should check if there's a hidden variadic tail and try ignoring it.
+        // This might cause subtyping correctly because the sub type here may not have a hidden variadic tail or equivalent.
+        if (!result.isSubtype)
+        {
+            auto [arguments, tail] = flatten(superFunction->argTypes);
+
+            if (auto variadic = get<VariadicTypePack>(tail); variadic && variadic->hidden)
+            {
+                result.orElse(isContravariantWith(env, subFunction->argTypes, arena->addTypePack(TypePack{arguments}), scope)
+                                  .withBothComponent(TypePath::PackField::Arguments));
+            }
+        }
     }
 
     result.andAlso(isCovariantWith(env, subFunction->retTypes, superFunction->retTypes, scope).withBothComponent(TypePath::PackField::Returns));
@@ -1688,6 +1783,9 @@ bool Subtyping::bindGeneric(SubtypingEnvironment& env, TypeId subTy, TypeId supe
         if (!get<GenericType>(subTy))
             return false;
 
+        if (!env.mappedGenerics.find(subTy) && env.containsMappedType(subTy))
+            iceReporter->ice("attempting to modify bounds of a potentially visited generic");
+
         env.mappedGenerics[subTy].upperBound.insert(superTy);
     }
     else
@@ -1695,6 +1793,9 @@ bool Subtyping::bindGeneric(SubtypingEnvironment& env, TypeId subTy, TypeId supe
         if (!get<GenericType>(superTy))
             return false;
 
+        if (!env.mappedGenerics.find(superTy) && env.containsMappedType(superTy))
+            iceReporter->ice("attempting to modify bounds of a potentially visited generic");
+
         env.mappedGenerics[superTy].lowerBound.insert(subTy);
     }
 
@@ -1740,7 +1841,7 @@ bool Subtyping::bindGeneric(SubtypingEnvironment& env, TypePackId subTp, TypePac
     if (!get<GenericTypePack>(subTp))
         return false;
 
-    if (TypePackId* m = env.mappedGenericPacks.find(subTp))
+    if (TypePackId* m = env.getMappedPackBounds(subTp))
         return *m == superTp;
 
     env.mappedGenericPacks[subTp] = superTp;
@@ -1761,7 +1862,7 @@ TypeId Subtyping::makeAggregateType(const Container& container, TypeId orElse)
 
 std::pair<TypeId, ErrorVec> Subtyping::handleTypeFunctionReductionResult(const TypeFunctionInstanceType* functionInstance, NotNull<Scope> scope)
 {
-    TypeFunctionContext context{arena, builtinTypes, scope, normalizer, iceReporter, NotNull{&limits}};
+    TypeFunctionContext context{arena, builtinTypes, scope, simplifier, normalizer, typeFunctionRuntime, iceReporter, NotNull{&limits}};
     TypeId function = arena->addType(*functionInstance);
     FunctionGraphReductionResult result = reduceTypeFunctions(function, {}, context, true);
     ErrorVec errors;

Analysis/src/Symbol.cpp

@@ -4,6 +4,7 @@
 #include "Luau/Common.h"
 
 LUAU_FASTFLAG(LuauSolverV2)
+LUAU_FASTFLAGVARIABLE(LuauSymbolEquality)
 
 namespace Luau
 {
@@ -14,7 +15,7 @@ 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)
+    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;

Analysis/src/TableLiteralInference.cpp

@@ -6,19 +6,15 @@
 #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(LuauAllowNonSharedTableTypesInLiteral)
+
 namespace Luau
 {
 
-static bool isLiteral(const AstExpr* expr)
-{
-    return (
-        expr->is<AstExprTable>() || expr->is<AstExprFunction>() || expr->is<AstExprConstantNumber>() || expr->is<AstExprConstantString>() ||
-        expr->is<AstExprConstantBool>() || expr->is<AstExprConstantNil>()
-    );
-}
-
 // A fast approximation of subTy <: superTy
 static bool fastIsSubtype(TypeId subTy, TypeId superTy)
 {
@@ -243,6 +239,8 @@ TypeId matchLiteralType(
             return exprType;
         }
 
+        DenseHashSet<AstExprConstantString*> keysToDelete{nullptr};
+
         for (const AstExprTable::Item& item : exprTable->items)
         {
             if (isRecord(item))
@@ -254,8 +252,19 @@ TypeId matchLiteralType(
 
                 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
+                    // that will definitely crash is trying to access a write
+                    // 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);
@@ -287,6 +296,9 @@ TypeId matchLiteralType(
                         else
                             tableTy->indexer = TableIndexer{expectedTableTy->indexer->indexType, matchedType};
 
+                        if (FFlag::LuauDontInPlaceMutateTableType)
+                            keysToDelete.insert(item.key->as<AstExprConstantString>());
+                        else
                             tableTy->props.erase(keyStr);
                     }
 
@@ -381,15 +393,11 @@ TypeId matchLiteralType(
                 const TypeId* keyTy = astTypes->find(item.key);
                 LUAU_ASSERT(keyTy);
                 TypeId tKey = follow(*keyTy);
-                if (get<BlockedType>(tKey))
+                LUAU_ASSERT(!is<BlockedType>(tKey));
-                    toBlock.push_back(tKey);
-
                 const TypeId* propTy = astTypes->find(item.value);
                 LUAU_ASSERT(propTy);
                 TypeId tProp = follow(*propTy);
-                if (get<BlockedType>(tProp))
+                LUAU_ASSERT(!is<BlockedType>(tProp));
-                    toBlock.push_back(tProp);
-
                 // 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;
@@ -398,6 +406,16 @@ TypeId matchLiteralType(
                 LUAU_ASSERT(!"Unexpected");
         }
 
+        if (FFlag::LuauDontInPlaceMutateTableType)
+        {
+            for (const auto& key : keysToDelete)
+            {
+                const AstArray<char>& s = key->value;
+                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
         // specified by the AST fragment.
         //

Analysis/src/ToDot.cpp

@@ -269,6 +269,12 @@ void StateDot::visitChildren(TypeId ty, int index)
             finishNodeLabel(ty);
             finishNode();
         }
+        else if constexpr (std::is_same_v<T, NoRefineType>)
+        {
+            formatAppend(result, "NoRefineType %d", index);
+            finishNodeLabel(ty);
+            finishNode();
+        }
         else if constexpr (std::is_same_v<T, UnknownType>)
         {
             formatAppend(result, "UnknownType %d", index);
@@ -414,7 +420,7 @@ void StateDot::visitChildren(TypePackId tp, int index)
         finishNodeLabel(tp);
         finishNode();
     }
-    else if (get<Unifiable::Error>(tp))
+    else if (get<ErrorTypePack>(tp))
     {
         formatAppend(result, "ErrorTypePack %d", index);
         finishNodeLabel(tp);

Analysis/src/ToString.cpp

@@ -20,6 +20,7 @@
 #include <string>
 
 LUAU_FASTFLAG(LuauSolverV2)
+LUAU_FASTFLAGVARIABLE(LuauSyntheticErrors)
 
 /*
  * Enables increasing levels of verbosity for Luau type names when stringifying.
@@ -38,7 +39,7 @@ LUAU_FASTFLAG(LuauSolverV2)
  * 3: Suffix free/generic types with their scope pointer, if present.
  */
 LUAU_FASTINTVARIABLE(DebugLuauVerboseTypeNames, 0)
-LUAU_FASTFLAGVARIABLE(DebugLuauToStringNoLexicalSort, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauToStringNoLexicalSort)
 
 namespace Luau
 {
@@ -856,6 +857,11 @@ struct TypeStringifier
         state.emit("any");
     }
 
+    void operator()(TypeId, const NoRefineType&)
+    {
+        state.emit("*no-refine*");
+    }
+
     void operator()(TypeId, const UnionType& uv)
     {
         if (state.hasSeen(&uv))
@@ -865,6 +871,8 @@ struct TypeStringifier
             return;
         }
 
+        LUAU_ASSERT(uv.options.size() > 1);
+
         bool optional = false;
         bool hasNonNilDisjunct = false;
 
@@ -873,7 +881,7 @@ struct TypeStringifier
         {
             el = follow(el);
 
-            if (isNil(el))
+            if (state.opts.useQuestionMarks && isNil(el))
             {
                 optional = true;
                 continue;
@@ -991,6 +999,14 @@ struct TypeStringifier
     void operator()(TypeId, const ErrorType& tv)
     {
         state.result.error = true;
+
+        if (FFlag::LuauSyntheticErrors && tv.synthetic)
+        {
+            state.emit("*error-type<");
+            stringify(*tv.synthetic);
+            state.emit(">*");
+        }
+        else
             state.emit("*error-type*");
     }
 
@@ -1040,6 +1056,7 @@ struct TypeStringifier
             state.emit(tfitv.userFuncName->value);
         else
             state.emit(tfitv.function->name);
+
         state.emit("<");
 
         bool comma = false;
@@ -1165,9 +1182,17 @@ struct TypePackStringifier
         state.unsee(&tp);
     }
 
-    void operator()(TypePackId, const Unifiable::Error& error)
+    void operator()(TypePackId, const ErrorTypePack& error)
     {
         state.result.error = true;
+
+        if (FFlag::LuauSyntheticErrors && error.synthetic)
+        {
+            state.emit("*");
+            stringify(*error.synthetic);
+            state.emit("*");
+        }
+        else
             state.emit("*error-type*");
     }
 
@@ -1840,6 +1865,8 @@ std::string toString(const Constraint& constraint, ToStringOptions& opts)
         }
         else if constexpr (std::is_same_v<T, EqualityConstraint>)
             return "equality: " + tos(c.resultType) + " ~ " + tos(c.assignmentType);
+        else if constexpr (std::is_same_v<T, TableCheckConstraint>)
+            return "table_check " + tos(c.expectedType) + " :> " + tos(c.exprType);
         else
             static_assert(always_false_v<T>, "Non-exhaustive constraint switch");
     };

Analysis/src/TxnLog.cpp

@@ -93,8 +93,8 @@ void TxnLog::concatAsIntersections(TxnLog rhs, NotNull<TypeArena> arena)
 
         if (auto leftRep = typeVarChanges.find(ty); leftRep && !(*leftRep)->dead)
         {
-            TypeId leftTy = arena->addType((*leftRep)->pending);
+            TypeId leftTy = arena->addType((*leftRep)->pending.clone());
-            TypeId rightTy = arena->addType(rightRep->pending);
+            TypeId rightTy = arena->addType(rightRep->pending.clone());
             typeVarChanges[ty]->pending.ty = IntersectionType{{leftTy, rightTy}};
         }
         else
@@ -170,8 +170,8 @@ void TxnLog::concatAsUnion(TxnLog rhs, NotNull<TypeArena> arena)
 
         if (auto leftRep = typeVarChanges.find(ty); leftRep && !(*leftRep)->dead)
         {
-            TypeId leftTy = arena->addType((*leftRep)->pending);
+            TypeId leftTy = arena->addType((*leftRep)->pending.clone());
-            TypeId rightTy = arena->addType(rightRep->pending);
+            TypeId rightTy = arena->addType(rightRep->pending.clone());
 
             if (follow(leftTy) == follow(rightTy))
                 typeVarChanges[ty] = std::move(rightRep);
@@ -217,7 +217,7 @@ TxnLog TxnLog::inverse()
     for (auto& [ty, _rep] : typeVarChanges)
     {
         if (!_rep->dead)
-            inversed.typeVarChanges[ty] = std::make_unique<PendingType>(*ty);
+            inversed.typeVarChanges[ty] = std::make_unique<PendingType>(ty->clone());
     }
 
     for (auto& [tp, _rep] : typePackChanges)
@@ -292,7 +292,7 @@ PendingType* TxnLog::queue(TypeId ty)
     auto& pending = typeVarChanges[ty];
     if (!pending || (*pending).dead)
     {
-        pending = std::make_unique<PendingType>(*ty);
+        pending = std::make_unique<PendingType>(ty->clone());
         pending->pending.owningArena = nullptr;
     }
 

Analysis/src/Type.cpp

@@ -27,6 +27,7 @@ LUAU_FASTINTVARIABLE(LuauTypeMaximumStringifierLength, 500)
 LUAU_FASTINTVARIABLE(LuauTableTypeMaximumStringifierLength, 0)
 LUAU_FASTINT(LuauTypeInferRecursionLimit)
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
+LUAU_FASTFLAGVARIABLE(LuauFreeTypesMustHaveBounds)
 
 namespace Luau
 {
@@ -478,24 +479,12 @@ bool hasLength(TypeId ty, DenseHashSet<TypeId>& seen, int* recursionCount)
     return false;
 }
 
-FreeType::FreeType(TypeLevel level)
+// New constructors
+FreeType::FreeType(TypeLevel level, TypeId lowerBound, TypeId upperBound)
     : index(Unifiable::freshIndex())
     , level(level)
-    , scope(nullptr)
+    , lowerBound(lowerBound)
-{
+    , upperBound(upperBound)
-}
-
-FreeType::FreeType(Scope* scope)
-    : index(Unifiable::freshIndex())
-    , level{}
-    , scope(scope)
-{
-}
-
-FreeType::FreeType(Scope* scope, TypeLevel level)
-    : index(Unifiable::freshIndex())
-    , level(level)
-    , scope(scope)
 {
 }
 
@@ -507,6 +496,40 @@ FreeType::FreeType(Scope* scope, TypeId lowerBound, TypeId upperBound)
 {
 }
 
+FreeType::FreeType(Scope* scope, TypeLevel level, TypeId lowerBound, TypeId upperBound)
+    : index(Unifiable::freshIndex())
+    , level(level)
+    , scope(scope)
+    , lowerBound(lowerBound)
+    , upperBound(upperBound)
+{
+}
+
+// Old constructors
+FreeType::FreeType(TypeLevel level)
+    : index(Unifiable::freshIndex())
+    , level(level)
+    , scope(nullptr)
+{
+    LUAU_ASSERT(!FFlag::LuauFreeTypesMustHaveBounds);
+}
+
+FreeType::FreeType(Scope* scope)
+    : index(Unifiable::freshIndex())
+    , level{}
+    , scope(scope)
+{
+    LUAU_ASSERT(!FFlag::LuauFreeTypesMustHaveBounds);
+}
+
+FreeType::FreeType(Scope* scope, TypeLevel level)
+    : index(Unifiable::freshIndex())
+    , level(level)
+    , scope(scope)
+{
+    LUAU_ASSERT(!FFlag::LuauFreeTypesMustHaveBounds);
+}
+
 GenericType::GenericType()
     : index(Unifiable::freshIndex())
     , name("g" + std::to_string(index))
@@ -554,12 +577,12 @@ BlockedType::BlockedType()
 {
 }
 
-Constraint* BlockedType::getOwner() const
+const Constraint* BlockedType::getOwner() const
 {
     return owner;
 }
 
-void BlockedType::setOwner(Constraint* newOwner)
+void BlockedType::setOwner(const Constraint* newOwner)
 {
     LUAU_ASSERT(owner == nullptr);
 
@@ -569,7 +592,7 @@ void BlockedType::setOwner(Constraint* newOwner)
     owner = newOwner;
 }
 
-void BlockedType::replaceOwner(Constraint* newOwner)
+void BlockedType::replaceOwner(const Constraint* newOwner)
 {
     owner = newOwner;
 }
@@ -999,6 +1022,11 @@ Type& Type::operator=(const Type& rhs)
     return *this;
 }
 
+Type Type::clone() const
+{
+    return *this;
+}
+
 TypeId makeFunction(
     TypeArena& arena,
     std::optional<TypeId> selfType,
@@ -1030,6 +1058,7 @@ BuiltinTypes::BuiltinTypes()
     , unknownType(arena->addType(Type{UnknownType{}, /*persistent*/ true}))
     , neverType(arena->addType(Type{NeverType{}, /*persistent*/ true}))
     , errorType(arena->addType(Type{ErrorType{}, /*persistent*/ true}))
+    , noRefineType(arena->addType(Type{NoRefineType{}, /*persistent*/ true}))
     , falsyType(arena->addType(Type{UnionType{{falseType, nilType}}, /*persistent*/ true}))
     , truthyType(arena->addType(Type{NegationType{falsyType}, /*persistent*/ true}))
     , optionalNumberType(arena->addType(Type{UnionType{{numberType, nilType}}, /*persistent*/ true}))
@@ -1039,7 +1068,7 @@ BuiltinTypes::BuiltinTypes()
     , unknownTypePack(arena->addTypePack(TypePackVar{VariadicTypePack{unknownType}, /*persistent*/ true}))
     , neverTypePack(arena->addTypePack(TypePackVar{VariadicTypePack{neverType}, /*persistent*/ true}))
     , uninhabitableTypePack(arena->addTypePack(TypePackVar{TypePack{{neverType}, neverTypePack}, /*persistent*/ true}))
-    , errorTypePack(arena->addTypePack(TypePackVar{Unifiable::Error{}, /*persistent*/ true}))
+    , errorTypePack(arena->addTypePack(TypePackVar{ErrorTypePack{}, /*persistent*/ true}))
 {
     freeze(*arena);
 }

Analysis/src/TypeArena.cpp

@@ -2,7 +2,8 @@
 
 #include "Luau/TypeArena.h"
 
-LUAU_FASTFLAGVARIABLE(DebugLuauFreezeArena, false);
+LUAU_FASTFLAGVARIABLE(DebugLuauFreezeArena);
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
 
 namespace Luau
 {
@@ -22,7 +23,34 @@ TypeId TypeArena::addTV(Type&& tv)
     return allocated;
 }
 
-TypeId TypeArena::freshType(TypeLevel level)
+TypeId TypeArena::freshType(NotNull<BuiltinTypes> builtins, TypeLevel level)
+{
+    TypeId allocated = types.allocate(FreeType{level, builtins->neverType, builtins->unknownType});
+
+    asMutable(allocated)->owningArena = this;
+
+    return allocated;
+}
+
+TypeId TypeArena::freshType(NotNull<BuiltinTypes> builtins, Scope* scope)
+{
+    TypeId allocated = types.allocate(FreeType{scope, builtins->neverType, builtins->unknownType});
+
+    asMutable(allocated)->owningArena = this;
+
+    return allocated;
+}
+
+TypeId TypeArena::freshType(NotNull<BuiltinTypes> builtins, Scope* scope, TypeLevel level)
+{
+    TypeId allocated = types.allocate(FreeType{scope, level, builtins->neverType, builtins->unknownType});
+
+    asMutable(allocated)->owningArena = this;
+
+    return allocated;
+}
+
+TypeId TypeArena::freshType_DEPRECATED(TypeLevel level)
 {
     TypeId allocated = types.allocate(FreeType{level});
 
@@ -31,7 +59,7 @@ TypeId TypeArena::freshType(TypeLevel level)
     return allocated;
 }
 
-TypeId TypeArena::freshType(Scope* scope)
+TypeId TypeArena::freshType_DEPRECATED(Scope* scope)
 {
     TypeId allocated = types.allocate(FreeType{scope});
 
@@ -40,7 +68,7 @@ TypeId TypeArena::freshType(Scope* scope)
     return allocated;
 }
 
-TypeId TypeArena::freshType(Scope* scope, TypeLevel level)
+TypeId TypeArena::freshType_DEPRECATED(Scope* scope, TypeLevel level)
 {
     TypeId allocated = types.allocate(FreeType{scope, level});
 

Analysis/src/TypeAttach.cpp

@@ -145,6 +145,12 @@ public:
     {
         return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("any"), std::nullopt, Location());
     }
+
+    AstType* operator()(const NoRefineType&)
+    {
+        return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("*no-refine*"), std::nullopt, Location());
+    }
+
     AstType* operator()(const TableType& ttv)
     {
         RecursionCounter counter(&count);
@@ -255,24 +261,24 @@ public:
         if (hasSeen(&ftv))
             return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("<Cycle>"), std::nullopt, Location());
 
-        AstArray<AstGenericType> generics;
+        AstArray<AstGenericType*> generics;
         generics.size = ftv.generics.size();
-        generics.data = static_cast<AstGenericType*>(allocator->allocate(sizeof(AstGenericType) * generics.size));
+        generics.data = static_cast<AstGenericType**>(allocator->allocate(sizeof(AstGenericType) * generics.size));
         size_t numGenerics = 0;
         for (auto it = ftv.generics.begin(); it != ftv.generics.end(); ++it)
         {
             if (auto gtv = get<GenericType>(*it))
-                generics.data[numGenerics++] = {AstName(gtv->name.c_str()), Location(), nullptr};
+                generics.data[numGenerics++] = allocator->alloc<AstGenericType>(Location(), AstName(gtv->name.c_str()), nullptr);
         }
 
-        AstArray<AstGenericTypePack> genericPacks;
+        AstArray<AstGenericTypePack*> genericPacks;
         genericPacks.size = ftv.genericPacks.size();
-        genericPacks.data = static_cast<AstGenericTypePack*>(allocator->allocate(sizeof(AstGenericTypePack) * genericPacks.size));
+        genericPacks.data = static_cast<AstGenericTypePack**>(allocator->allocate(sizeof(AstGenericTypePack) * genericPacks.size));
         size_t numGenericPacks = 0;
         for (auto it = ftv.genericPacks.begin(); it != ftv.genericPacks.end(); ++it)
         {
             if (auto gtv = get<GenericTypePack>(*it))
-                genericPacks.data[numGenericPacks++] = {AstName(gtv->name.c_str()), Location(), nullptr};
+                genericPacks.data[numGenericPacks++] = allocator->alloc<AstGenericTypePack>(Location(), AstName(gtv->name.c_str()), nullptr);
         }
 
         AstArray<AstType*> argTypes;
@@ -323,7 +329,7 @@ public:
             Location(), generics, genericPacks, AstTypeList{argTypes, argTailAnnotation}, argNames, AstTypeList{returnTypes, retTailAnnotation}
         );
     }
-    AstType* operator()(const Unifiable::Error&)
+    AstType* operator()(const ErrorType&)
     {
         return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("Unifiable<Error>"), std::nullopt, Location());
     }
@@ -380,8 +386,12 @@ public:
     }
     AstType* operator()(const NegationType& ntv)
     {
-        // FIXME: do the same thing we do with ErrorType
+        AstArray<AstTypeOrPack> params;
-        throw InternalCompilerError("Cannot convert NegationType into AstNode");
+        params.size = 1;
+        params.data = static_cast<AstTypeOrPack*>(allocator->allocate(sizeof(AstType*)));
+        params.data[0] = AstTypeOrPack{Luau::visit(*this, ntv.ty->ty), nullptr};
+
+        return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("negate"), std::nullopt, Location(), true, params);
     }
     AstType* operator()(const TypeFunctionInstanceType& tfit)
     {
@@ -452,7 +462,7 @@ public:
         return allocator->alloc<AstTypePackGeneric>(Location(), AstName("free"));
     }
 
-    AstTypePack* operator()(const Unifiable::Error&) const
+    AstTypePack* operator()(const ErrorTypePack&) const
     {
         return allocator->alloc<AstTypePackGeneric>(Location(), AstName("Unifiable<Error>"));
     }

Analysis/src/TypeChecker2.cpp

@@ -7,7 +7,6 @@
 #include "Luau/DcrLogger.h"
 #include "Luau/DenseHash.h"
 #include "Luau/Error.h"
-#include "Luau/InsertionOrderedMap.h"
 #include "Luau/Instantiation.h"
 #include "Luau/Metamethods.h"
 #include "Luau/Normalize.h"
@@ -27,11 +26,11 @@
 #include "Luau/VisitType.h"
 
 #include <algorithm>
-#include <iostream>
-#include <ostream>
 
 LUAU_FASTFLAG(DebugLuauMagicTypes)
 
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+
 namespace Luau
 {
 
@@ -173,7 +172,7 @@ struct InternalTypeFunctionFinder : TypeOnceVisitor
     DenseHashSet<TypeId> mentionedFunctions{nullptr};
     DenseHashSet<TypePackId> mentionedFunctionPacks{nullptr};
 
-    InternalTypeFunctionFinder(std::vector<TypeId>& declStack)
+    explicit InternalTypeFunctionFinder(std::vector<TypeId>& declStack)
     {
         TypeFunctionFinder f;
         for (TypeId fn : declStack)
@@ -266,6 +265,8 @@ struct InternalTypeFunctionFinder : TypeOnceVisitor
 
 void check(
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<UnifierSharedState> unifierState,
     NotNull<TypeCheckLimits> limits,
     DcrLogger* logger,
@@ -275,7 +276,7 @@ void check(
 {
     LUAU_TIMETRACE_SCOPE("check", "Typechecking");
 
-    TypeChecker2 typeChecker{builtinTypes, unifierState, limits, logger, &sourceModule, module};
+    TypeChecker2 typeChecker{builtinTypes, simplifier, typeFunctionRuntime, unifierState, limits, logger, &sourceModule, module};
 
     typeChecker.visit(sourceModule.root);
 
@@ -292,6 +293,8 @@ void check(
 
 TypeChecker2::TypeChecker2(
     NotNull<BuiltinTypes> builtinTypes,
+    NotNull<Simplifier> simplifier,
+    NotNull<TypeFunctionRuntime> typeFunctionRuntime,
     NotNull<UnifierSharedState> unifierState,
     NotNull<TypeCheckLimits> limits,
     DcrLogger* logger,
@@ -299,13 +302,15 @@ TypeChecker2::TypeChecker2(
     Module* module
 )
     : builtinTypes(builtinTypes)
+    , simplifier(simplifier)
+    , typeFunctionRuntime(typeFunctionRuntime)
     , logger(logger)
     , limits(limits)
     , ice(unifierState->iceHandler)
     , sourceModule(sourceModule)
     , module(module)
     , normalizer{&module->internalTypes, builtinTypes, unifierState, /* cacheInhabitance */ true}
-    , _subtyping{builtinTypes, NotNull{&module->internalTypes}, NotNull{&normalizer}, NotNull{unifierState->iceHandler}}
+    , _subtyping{builtinTypes, NotNull{&module->internalTypes}, simplifier, NotNull{&normalizer}, typeFunctionRuntime, NotNull{unifierState->iceHandler}}
     , subtyping(&_subtyping)
 {
 }
@@ -483,10 +488,13 @@ TypeId TypeChecker2::checkForTypeFunctionInhabitance(TypeId instance, Location l
         return instance;
     seenTypeFunctionInstances.insert(instance);
 
-    ErrorVec errors = reduceTypeFunctions(
+    ErrorVec errors =
+        reduceTypeFunctions(
             instance,
             location,
-                          TypeFunctionContext{NotNull{&module->internalTypes}, builtinTypes, stack.back(), NotNull{&normalizer}, ice, limits},
+            TypeFunctionContext{
+                NotNull{&module->internalTypes}, builtinTypes, stack.back(), simplifier, NotNull{&normalizer}, typeFunctionRuntime, ice, limits
+            },
             true
         )
             .errors;
@@ -495,7 +503,7 @@ TypeId TypeChecker2::checkForTypeFunctionInhabitance(TypeId instance, Location l
     return instance;
 }
 
-TypePackId TypeChecker2::lookupPack(AstExpr* expr)
+TypePackId TypeChecker2::lookupPack(AstExpr* expr) const
 {
     // If a type isn't in the type graph, it probably means that a recursion limit was exceeded.
     // We'll just return anyType in these cases.  Typechecking against any is very fast and this
@@ -545,7 +553,7 @@ TypeId TypeChecker2::lookupAnnotation(AstType* annotation)
     return checkForTypeFunctionInhabitance(follow(*ty), annotation->location);
 }
 
-std::optional<TypePackId> TypeChecker2::lookupPackAnnotation(AstTypePack* annotation)
+std::optional<TypePackId> TypeChecker2::lookupPackAnnotation(AstTypePack* annotation) const
 {
     TypePackId* tp = module->astResolvedTypePacks.find(annotation);
     if (tp != nullptr)
@@ -553,7 +561,7 @@ std::optional<TypePackId> TypeChecker2::lookupPackAnnotation(AstTypePack* annota
     return {};
 }
 
-TypeId TypeChecker2::lookupExpectedType(AstExpr* expr)
+TypeId TypeChecker2::lookupExpectedType(AstExpr* expr) const
 {
     if (TypeId* ty = module->astExpectedTypes.find(expr))
         return follow(*ty);
@@ -561,7 +569,7 @@ TypeId TypeChecker2::lookupExpectedType(AstExpr* expr)
     return builtinTypes->anyType;
 }
 
-TypePackId TypeChecker2::lookupExpectedPack(AstExpr* expr, TypeArena& arena)
+TypePackId TypeChecker2::lookupExpectedPack(AstExpr* expr, TypeArena& arena) const
 {
     if (TypeId* ty = module->astExpectedTypes.find(expr))
         return arena.addTypePack(TypePack{{follow(*ty)}, std::nullopt});
@@ -585,7 +593,7 @@ TypePackId TypeChecker2::reconstructPack(AstArray<AstExpr*> exprs, TypeArena& ar
     return arena.addTypePack(TypePack{head, tail});
 }
 
-Scope* TypeChecker2::findInnermostScope(Location location)
+Scope* TypeChecker2::findInnermostScope(Location location) const
 {
     Scope* bestScope = module->getModuleScope().get();
 
@@ -1008,7 +1016,8 @@ void TypeChecker2::visit(AstStatForIn* forInStatement)
     {
         reportError(OptionalValueAccess{iteratorTy}, forInStatement->values.data[0]->location);
     }
-    else if (std::optional<TypeId> iterMmTy = findMetatableEntry(builtinTypes, module->errors, iteratorTy, "__iter", forInStatement->values.data[0]->location))
+    else if (std::optional<TypeId> iterMmTy =
+                 findMetatableEntry(builtinTypes, module->errors, iteratorTy, "__iter", forInStatement->values.data[0]->location))
     {
         Instantiation instantiation{TxnLog::empty(), &arena, builtinTypes, TypeLevel{}, scope};
 
@@ -1193,8 +1202,6 @@ void TypeChecker2::visit(AstStatTypeAlias* stat)
 void TypeChecker2::visit(AstStatTypeFunction* stat)
 {
     // TODO: add type checking for user-defined type functions
-
-    reportError(TypeError{stat->location, GenericError{"This syntax is not supported"}});
 }
 
 void TypeChecker2::visit(AstTypeList types)
@@ -1345,8 +1352,18 @@ void TypeChecker2::visit(AstExprGlobal* expr)
 {
     NotNull<Scope> scope = stack.back();
     if (!scope->lookup(expr->name))
+    {
         reportError(UnknownSymbol{expr->name.value, UnknownSymbol::Binding}, expr->location);
     }
+    else
+    {
+        if (scope->shouldWarnGlobal(expr->name.value) && !warnedGlobals.contains(expr->name.value))
+        {
+            reportError(UnknownSymbol{expr->name.value, UnknownSymbol::Binding}, expr->location);
+            warnedGlobals.insert(expr->name.value);
+        }
+    }
+}
 
 void TypeChecker2::visit(AstExprVarargs* expr)
 {
@@ -1433,9 +1450,10 @@ void TypeChecker2::visitCall(AstExprCall* call)
     TypePackId argsTp = module->internalTypes.addTypePack(args);
     if (auto ftv = get<FunctionType>(follow(*originalCallTy)))
     {
-        if (ftv->dcrMagicTypeCheck)
+        if (ftv->magic)
         {
-            ftv->dcrMagicTypeCheck(MagicFunctionTypeCheckContext{NotNull{this}, builtinTypes, call, argsTp, scope});
+            bool usedMagic = ftv->magic->typeCheck(MagicFunctionTypeCheckContext{NotNull{this}, builtinTypes, call, argsTp, scope});
+            if (usedMagic)
                 return;
         }
     }
@@ -1444,7 +1462,9 @@ void TypeChecker2::visitCall(AstExprCall* call)
     OverloadResolver resolver{
         builtinTypes,
         NotNull{&module->internalTypes},
+        simplifier,
         NotNull{&normalizer},
+        typeFunctionRuntime,
         NotNull{stack.back()},
         ice,
         limits,
@@ -1540,7 +1560,7 @@ void TypeChecker2::visit(AstExprCall* call)
     visitCall(call);
 }
 
-std::optional<TypeId> TypeChecker2::tryStripUnionFromNil(TypeId ty)
+std::optional<TypeId> TypeChecker2::tryStripUnionFromNil(TypeId ty) const
 {
     if (const UnionType* utv = get<UnionType>(ty))
     {
@@ -1618,8 +1638,7 @@ void TypeChecker2::indexExprMetatableHelper(AstExprIndexExpr* indexExpr, const M
         indexExprMetatableHelper(indexExpr, mtmt, exprType, indexType);
     else
     {
-        LUAU_ASSERT(tt || get<PrimitiveType>(follow(metaTable->table)));
+        // CLI-122161: We're not handling unions correctly (probably).
-
         reportError(CannotExtendTable{exprType, CannotExtendTable::Indexer, "indexer??"}, indexExpr->location);
     }
 }
@@ -1826,11 +1845,10 @@ void TypeChecker2::visit(AstExprFunction* fn)
 
 void TypeChecker2::visit(AstExprTable* expr)
 {
-    // TODO!
     for (const AstExprTable::Item& item : expr->items)
     {
         if (item.key)
-            visit(item.key, ValueContext::LValue);
+            visit(item.key, ValueContext::RValue);
         visit(item.value, ValueContext::RValue);
     }
 }
@@ -2078,7 +2096,10 @@ TypeId TypeChecker2::visit(AstExprBinary* expr, AstNode* overrideKey)
                 }
                 else
                 {
-                    expectedRets = module->internalTypes.addTypePack({module->internalTypes.freshType(scope, TypeLevel{})});
+                    expectedRets = module->internalTypes.addTypePack(
+                        {FFlag::LuauFreeTypesMustHaveBounds ? module->internalTypes.freshType(builtinTypes, scope, TypeLevel{})
+                                                            : module->internalTypes.freshType_DEPRECATED(scope, TypeLevel{})}
+                    );
                 }
 
                 TypeId expectedTy = module->internalTypes.addType(FunctionType(expectedArgs, expectedRets));
@@ -2330,7 +2351,8 @@ TypeId TypeChecker2::flattenPack(TypePackId pack)
         return *fst;
     else if (auto ftp = get<FreeTypePack>(pack))
     {
-        TypeId result = module->internalTypes.addType(FreeType{ftp->scope});
+        TypeId result = FFlag::LuauFreeTypesMustHaveBounds ? module->internalTypes.freshType(builtinTypes, ftp->scope)
+                                                           : module->internalTypes.addType(FreeType{ftp->scope});
         TypePackId freeTail = module->internalTypes.addTypePack(FreeTypePack{ftp->scope});
 
         TypePack* resultPack = emplaceTypePack<TypePack>(asMutable(pack));
@@ -2339,7 +2361,7 @@ TypeId TypeChecker2::flattenPack(TypePackId pack)
 
         return result;
     }
-    else if (get<Unifiable::Error>(pack))
+    else if (get<ErrorTypePack>(pack))
         return builtinTypes->errorRecoveryType();
     else if (finite(pack) && size(pack) == 0)
         return builtinTypes->nilType; // `(f())` where `f()` returns no values is coerced into `nil`
@@ -2347,30 +2369,30 @@ TypeId TypeChecker2::flattenPack(TypePackId pack)
         ice->ice("flattenPack got a weird pack!");
 }
 
-void TypeChecker2::visitGenerics(AstArray<AstGenericType> generics, AstArray<AstGenericTypePack> genericPacks)
+void TypeChecker2::visitGenerics(AstArray<AstGenericType*> generics, AstArray<AstGenericTypePack*> genericPacks)
 {
     DenseHashSet<AstName> seen{AstName{}};
 
-    for (const auto& g : generics)
+    for (const auto* g : generics)
     {
-        if (seen.contains(g.name))
+        if (seen.contains(g->name))
-            reportError(DuplicateGenericParameter{g.name.value}, g.location);
+            reportError(DuplicateGenericParameter{g->name.value}, g->location);
         else
-            seen.insert(g.name);
+            seen.insert(g->name);
 
-        if (g.defaultValue)
+        if (g->defaultValue)
-            visit(g.defaultValue);
+            visit(g->defaultValue);
     }
 
-    for (const auto& g : genericPacks)
+    for (const auto* g : genericPacks)
     {
-        if (seen.contains(g.name))
+        if (seen.contains(g->name))
-            reportError(DuplicateGenericParameter{g.name.value}, g.location);
+            reportError(DuplicateGenericParameter{g->name.value}, g->location);
         else
-            seen.insert(g.name);
+            seen.insert(g->name);
 
-        if (g.defaultValue)
+        if (g->defaultValue)
-            visit(g.defaultValue);
+            visit(g->defaultValue);
     }
 }
 
@@ -2392,6 +2414,8 @@ void TypeChecker2::visit(AstType* ty)
         return visit(t);
     else if (auto t = ty->as<AstTypeIntersection>())
         return visit(t);
+    else if (auto t = ty->as<AstTypeGroup>())
+        return visit(t->type);
 }
 
 void TypeChecker2::visit(AstTypeReference* ty)
@@ -3012,10 +3036,8 @@ PropertyType TypeChecker2::hasIndexTypeFromType(
         if (tt->indexer)
         {
             TypeId indexType = follow(tt->indexer->indexType);
-            if (isPrim(indexType, PrimitiveType::String))
+            TypeId givenType = module->internalTypes.addType(SingletonType{StringSingleton{prop}});
-                return {NormalizationResult::True, {tt->indexer->indexResultType}};
+            if (isSubtype(givenType, indexType, NotNull{module->getModuleScope().get()}, builtinTypes, simplifier, *ice))
-            // If the indexer looks like { [any] : _} - the prop lookup should be allowed!
-            else if (get<AnyType>(indexType) || get<UnknownType>(indexType))
                 return {NormalizationResult::True, {tt->indexer->indexResultType}};
         }
 

Analysis/src/TypeFunctionReductionGuesser.cpp

@@ -3,6 +3,7 @@
 
 #include "Luau/DenseHash.h"
 #include "Luau/Normalize.h"
+#include "Luau/ToString.h"
 #include "Luau/TypeFunction.h"
 #include "Luau/Type.h"
 #include "Luau/TypePack.h"

Analysis/src/TypeInfer.cpp

@@ -23,18 +23,18 @@
 #include <algorithm>
 #include <iterator>
 
-LUAU_FASTFLAGVARIABLE(DebugLuauMagicTypes, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauMagicTypes)
 LUAU_FASTINTVARIABLE(LuauTypeInferRecursionLimit, 165)
 LUAU_FASTINTVARIABLE(LuauTypeInferIterationLimit, 20000)
 LUAU_FASTINTVARIABLE(LuauTypeInferTypePackLoopLimit, 5000)
 LUAU_FASTINTVARIABLE(LuauCheckRecursionLimit, 300)
 LUAU_FASTINTVARIABLE(LuauVisitRecursionLimit, 500)
 LUAU_FASTFLAG(LuauKnowsTheDataModel3)
-LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification, false)
+LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification)
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
-LUAU_FASTFLAGVARIABLE(LuauRemoveBadRelationalOperatorWarning, false)
+LUAU_FASTFLAGVARIABLE(LuauOldSolverCreatesChildScopePointers)
-LUAU_FASTFLAGVARIABLE(LuauOkWithIteratingOverTableProperties, false)
+LUAU_FASTFLAG(LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)
-LUAU_FASTFLAGVARIABLE(LuauAcceptIndexingTableUnionsIntersections, false)
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
 
 namespace Luau
 {
@@ -265,11 +265,7 @@ ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mo
     ScopePtr parentScope = environmentScope.value_or(globalScope);
     ScopePtr moduleScope = std::make_shared<Scope>(parentScope);
 
-    if (module.cyclic)
-        moduleScope->returnType = addTypePack(TypePack{{anyType}, std::nullopt});
-    else
     moduleScope->returnType = freshTypePack(moduleScope);
-
     moduleScope->varargPack = anyTypePack;
 
     currentModule->scopes.push_back(std::make_pair(module.root->location, moduleScope));
@@ -767,8 +763,12 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatRepeat& state
 
 struct Demoter : Substitution
 {
-    Demoter(TypeArena* arena)
+    TypeArena* arena = nullptr;
+    NotNull<BuiltinTypes> builtins;
+    Demoter(TypeArena* arena, NotNull<BuiltinTypes> builtins)
         : Substitution(TxnLog::empty(), arena)
+        , arena(arena)
+        , builtins(builtins)
     {
     }
 
@@ -794,7 +794,8 @@ struct Demoter : Substitution
     {
         auto ftv = get<FreeType>(ty);
         LUAU_ASSERT(ftv);
-        return addType(FreeType{demotedLevel(ftv->level)});
+        return FFlag::LuauFreeTypesMustHaveBounds ? arena->freshType(builtins, demotedLevel(ftv->level))
+                                                  : addType(FreeType{demotedLevel(ftv->level)});
     }
 
     TypePackId clean(TypePackId tp) override
@@ -841,7 +842,7 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatReturn& retur
         }
     }
 
-    Demoter demoter{&currentModule->internalTypes};
+    Demoter demoter{&currentModule->internalTypes, builtinTypes};
     demoter.demote(expectedTypes);
 
     TypePackId retPack = checkExprList(scope, return_.location, return_.list, false, {}, expectedTypes).type;
@@ -958,7 +959,7 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatAssign& assig
         else if (auto tail = valueIter.tail())
         {
             TypePackId tailPack = follow(*tail);
-            if (get<Unifiable::Error>(tailPack))
+            if (get<ErrorTypePack>(tailPack))
                 right = errorRecoveryType(scope);
             else if (auto vtp = get<VariadicTypePack>(tailPack))
                 right = vtp->ty;
@@ -1238,7 +1239,7 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatForIn& forin)
             iterTy = freshType(scope);
             unify(callRetPack, addTypePack({{iterTy}, freshTypePack(scope)}), scope, forin.location);
         }
-        else if (get<Unifiable::Error>(callRetPack) || !first(callRetPack))
+        else if (get<ErrorTypePack>(callRetPack) || !first(callRetPack))
         {
             for (TypeId var : varTypes)
                 unify(errorRecoveryType(scope), var, scope, forin.location);
@@ -1284,20 +1285,11 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatForIn& forin)
             for (size_t i = 2; i < varTypes.size(); ++i)
                 unify(nilType, varTypes[i], scope, forin.location);
         }
-        else if (isNonstrictMode() || FFlag::LuauOkWithIteratingOverTableProperties)
+        else
         {
             for (TypeId var : varTypes)
                 unify(unknownType, var, scope, forin.location);
         }
-        else
-        {
-            TypeId varTy = errorRecoveryType(loopScope);
-
-            for (TypeId var : varTypes)
-                unify(varTy, var, scope, forin.location);
-
-            reportError(firstValue->location, GenericError{"Cannot iterate over a table without indexer"});
-        }
 
         return check(loopScope, *forin.body);
     }
@@ -1975,7 +1967,7 @@ WithPredicate<TypeId> TypeChecker::checkExpr(const ScopePtr& scope, const AstExp
         *asMutable(varargPack) = TypePack{{head}, tail};
         return WithPredicate{head};
     }
-    if (get<ErrorType>(varargPack))
+    if (get<ErrorTypePack>(varargPack))
         return WithPredicate{errorRecoveryType(scope)};
     else if (auto vtp = get<VariadicTypePack>(varargPack))
         return WithPredicate{vtp->ty};
@@ -2005,7 +1997,7 @@ WithPredicate<TypeId> TypeChecker::checkExpr(const ScopePtr& scope, const AstExp
         unify(pack, retPack, scope, expr.location);
         return {head, std::move(result.predicates)};
     }
-    if (get<Unifiable::Error>(retPack))
+    if (get<ErrorTypePack>(retPack))
         return {errorRecoveryType(scope), std::move(result.predicates)};
     else if (auto vtp = get<VariadicTypePack>(retPack))
         return {vtp->ty, std::move(result.predicates)};
@@ -2804,8 +2796,6 @@ TypeId TypeChecker::checkRelationalOperation(
         {
             reportErrors(state.errors);
 
-            if (FFlag::LuauRemoveBadRelationalOperatorWarning)
-            {
             // The original version of this check also produced this error when we had a union type.
             // However, the old solver does not readily have the ability to discern if the union is comparable.
             // This is the case when the lhs is e.g. a union of singletons and the rhs is the combined type.
@@ -2820,19 +2810,6 @@ TypeId TypeChecker::checkRelationalOperation(
                     }
                 );
             }
-            }
-            else
-            {
-                if (!isEquality && state.errors.empty() && (get<UnionType>(leftType) || isBoolean(leftType)))
-                {
-                    reportError(
-                        expr.location,
-                        GenericError{
-                            format("Type '%s' cannot be compared with relational operator %s", toString(leftType).c_str(), toString(expr.op).c_str())
-                        }
-                    );
-                }
-            }
 
             return booleanType;
         }
@@ -2896,7 +2873,7 @@ TypeId TypeChecker::checkRelationalOperation(
             std::optional<TypeId> metamethod = findMetatableEntry(lhsType, metamethodName, expr.location, /* addErrors= */ true);
             if (metamethod)
             {
-                if (const FunctionType* ftv = get<FunctionType>(*metamethod))
+                if (const FunctionType* ftv = get<FunctionType>(follow(*metamethod)))
                 {
                     if (isEquality)
                     {
@@ -3507,7 +3484,6 @@ TypeId TypeChecker::checkLValueBinding(const ScopePtr& scope, const AstExprIndex
         }
     }
 
-    if (FFlag::LuauAcceptIndexingTableUnionsIntersections)
     {
         // We're going to have a whole vector.
         std::vector<TableType*> tableTypes{};
@@ -3658,57 +3634,6 @@ TypeId TypeChecker::checkLValueBinding(const ScopePtr& scope, const AstExprIndex
 
         return addType(IntersectionType{{resultTypes.begin(), resultTypes.end()}});
     }
-    else
-    {
-        TableType* exprTable = getMutableTableType(exprType);
-        if (!exprTable)
-        {
-            reportError(TypeError{expr.expr->location, NotATable{exprType}});
-            return errorRecoveryType(scope);
-        }
-
-        if (value)
-        {
-            const auto& it = exprTable->props.find(value->value.data);
-            if (it != exprTable->props.end())
-            {
-                return it->second.type();
-            }
-            else if ((ctx == ValueContext::LValue && exprTable->state == TableState::Unsealed) || exprTable->state == TableState::Free)
-            {
-                TypeId resultType = freshType(scope);
-                Property& property = exprTable->props[value->value.data];
-                property.setType(resultType);
-                property.location = expr.index->location;
-                return resultType;
-            }
-        }
-
-        if (exprTable->indexer)
-        {
-            const TableIndexer& indexer = *exprTable->indexer;
-            unify(indexType, indexer.indexType, scope, expr.index->location);
-            return indexer.indexResultType;
-        }
-        else if ((ctx == ValueContext::LValue && exprTable->state == TableState::Unsealed) || exprTable->state == TableState::Free)
-        {
-            TypeId indexerType = freshType(exprTable->level);
-            unify(indexType, indexerType, scope, expr.location);
-            TypeId indexResultType = freshType(exprTable->level);
-
-            exprTable->indexer = TableIndexer{anyIfNonstrict(indexerType), anyIfNonstrict(indexResultType)};
-            return indexResultType;
-        }
-        else
-        {
-            /*
-             * If we use [] indexing to fetch a property from a sealed table that
-             * has no indexer, we have no idea if it will work so we just return any
-             * and hope for the best.
-             */
-            return anyType;
-        }
-    }
 }
 
 // Answers the question: "Can I define another function with this name?"
@@ -4163,7 +4088,7 @@ void TypeChecker::checkArgumentList(
             if (argIter.tail())
             {
                 TypePackId tail = *argIter.tail();
-                if (state.log.getMutable<Unifiable::Error>(tail))
+                if (state.log.getMutable<ErrorTypePack>(tail))
                 {
                     // Unify remaining parameters so we don't leave any free-types hanging around.
                     while (paramIter != endIter)
@@ -4248,7 +4173,7 @@ void TypeChecker::checkArgumentList(
             }
             TypePackId tail = state.log.follow(*paramIter.tail());
 
-            if (state.log.getMutable<Unifiable::Error>(tail))
+            if (state.log.getMutable<ErrorTypePack>(tail))
             {
                 // Function is variadic.  Ok.
                 return;
@@ -4384,7 +4309,7 @@ WithPredicate<TypePackId> TypeChecker::checkExprPackHelper(const ScopePtr& scope
         WithPredicate<TypePackId> argListResult = checkExprList(scope, expr.location, expr.args, false, {}, expectedTypes);
         TypePackId argPack = argListResult.type;
 
-        if (get<Unifiable::Error>(argPack))
+        if (get<ErrorTypePack>(argPack))
             return WithPredicate{errorRecoveryTypePack(scope)};
 
         TypePack* args = nullptr;
@@ -4490,7 +4415,7 @@ std::vector<std::optional<TypeId>> TypeChecker::getExpectedTypesForCall(const st
         }
     }
 
-    Demoter demoter{&currentModule->internalTypes};
+    Demoter demoter{&currentModule->internalTypes, builtinTypes};
     demoter.demote(expectedTypes);
 
     return expectedTypes;
@@ -4588,10 +4513,10 @@ std::unique_ptr<WithPredicate<TypePackId>> TypeChecker::checkCallOverload(
 
     // When this function type has magic functions and did return something, we select that overload instead.
     // TODO: pass in a Unifier object to the magic functions? This will allow the magic functions to cooperate with overload resolution.
-    if (ftv->magicFunction)
+    if (ftv->magic)
     {
         // TODO: We're passing in the wrong TypePackId. Should be argPack, but a unit test fails otherwise. CLI-40458
-        if (std::optional<WithPredicate<TypePackId>> ret = ftv->magicFunction(*this, scope, expr, argListResult))
+        if (std::optional<WithPredicate<TypePackId>> ret = ftv->magic->handleOldSolver(*this, scope, expr, argListResult))
             return std::make_unique<WithPredicate<TypePackId>>(std::move(*ret));
     }
 
@@ -4974,7 +4899,7 @@ TypeId TypeChecker::checkRequire(const ScopePtr& scope, const ModuleInfo& module
 
     TypePackId modulePack = module->returnType;
 
-    if (get<Unifiable::Error>(modulePack))
+    if (get<ErrorTypePack>(modulePack))
         return errorRecoveryType(scope);
 
     std::optional<TypeId> moduleType = first(modulePack);
@@ -5063,17 +4988,17 @@ void TypeChecker::unifyWithInstantiationIfNeeded(TypeId subTy, TypeId superTy, c
     {
         // First try unifying with the original uninstantiated type
         // but if that fails, try the instantiated one.
-        Unifier child = state.makeChildUnifier();
+        std::unique_ptr<Unifier> child = state.makeChildUnifier();
-        child.tryUnify(subTy, superTy, /*isFunctionCall*/ false);
+        child->tryUnify(subTy, superTy, /*isFunctionCall*/ false);
-        if (!child.errors.empty())
+        if (!child->errors.empty())
         {
-            TypeId instantiated = instantiate(scope, subTy, state.location, &child.log);
+            TypeId instantiated = instantiate(scope, subTy, state.location, &child->log);
             if (subTy == instantiated)
             {
                 // Instantiating the argument made no difference, so just report any child errors
-                state.log.concat(std::move(child.log));
+                state.log.concat(std::move(child->log));
 
-                state.errors.insert(state.errors.end(), child.errors.begin(), child.errors.end());
+                state.errors.insert(state.errors.end(), child->errors.begin(), child->errors.end());
             }
             else
             {
@@ -5082,7 +5007,7 @@ void TypeChecker::unifyWithInstantiationIfNeeded(TypeId subTy, TypeId superTy, c
         }
         else
         {
-            state.log.concat(std::move(child.log));
+            state.log.concat(std::move(child->log));
         }
     }
 }
@@ -5287,6 +5212,13 @@ 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;
+        parent->children.emplace_back(scope.get());
+    }
+
     currentModule->scopes.push_back(std::make_pair(location, scope));
     return scope;
 }
@@ -5297,6 +5229,12 @@ 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;
+        parent->children.emplace_back(scope.get());
+    }
 
     currentModule->scopes.push_back(std::make_pair(location, scope));
     return scope;
@@ -5342,7 +5280,8 @@ TypeId TypeChecker::freshType(const ScopePtr& scope)
 
 TypeId TypeChecker::freshType(TypeLevel level)
 {
-    return currentModule->internalTypes.addType(Type(FreeType(level)));
+    return FFlag::LuauFreeTypesMustHaveBounds ? currentModule->internalTypes.freshType(builtinTypes, level)
+                                              : currentModule->internalTypes.addType(Type(FreeType(level)));
 }
 
 TypeId TypeChecker::singletonType(bool value)
@@ -5787,6 +5726,12 @@ TypeId TypeChecker::resolveTypeWorker(const ScopePtr& scope, const AstType& anno
     }
     else if (const auto& un = annotation.as<AstTypeUnion>())
     {
+        if (FFlag::LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)
+        {
+            if (un->types.size == 1)
+                return resolveType(scope, *un->types.data[0]);
+        }
+
         std::vector<TypeId> types;
         for (AstType* ann : un->types)
             types.push_back(resolveType(scope, *ann));
@@ -5795,12 +5740,22 @@ TypeId TypeChecker::resolveTypeWorker(const ScopePtr& scope, const AstType& anno
     }
     else if (const auto& un = annotation.as<AstTypeIntersection>())
     {
+        if (FFlag::LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)
+        {
+            if (un->types.size == 1)
+                return resolveType(scope, *un->types.data[0]);
+        }
+
         std::vector<TypeId> types;
         for (AstType* ann : un->types)
             types.push_back(resolveType(scope, *ann));
 
         return addType(IntersectionType{types});
     }
+    else if (const auto& g = annotation.as<AstTypeGroup>())
+    {
+        return resolveType(scope, *g->type);
+    }
     else if (const auto& tsb = annotation.as<AstTypeSingletonBool>())
     {
         return singletonType(tsb->value);
@@ -5958,8 +5913,8 @@ GenericTypeDefinitions TypeChecker::createGenericTypes(
     const ScopePtr& scope,
     std::optional<TypeLevel> levelOpt,
     const AstNode& node,
-    const AstArray<AstGenericType>& genericNames,
+    const AstArray<AstGenericType*>& genericNames,
-    const AstArray<AstGenericTypePack>& genericPackNames,
+    const AstArray<AstGenericTypePack*>& genericPackNames,
     bool useCache
 )
 {
@@ -5969,14 +5924,14 @@ GenericTypeDefinitions TypeChecker::createGenericTypes(
 
     std::vector<GenericTypeDefinition> generics;
 
-    for (const AstGenericType& generic : genericNames)
+    for (const AstGenericType* generic : genericNames)
     {
         std::optional<TypeId> defaultValue;
 
-        if (generic.defaultValue)
+        if (generic->defaultValue)
-            defaultValue = resolveType(scope, *generic.defaultValue);
+            defaultValue = resolveType(scope, *generic->defaultValue);
 
-        Name n = generic.name.value;
+        Name n = generic->name.value;
 
         // These generics are the only thing that will ever be added to scope, so we can be certain that
         // a collision can only occur when two generic types have the same name.
@@ -6005,14 +5960,14 @@ GenericTypeDefinitions TypeChecker::createGenericTypes(
 
     std::vector<GenericTypePackDefinition> genericPacks;
 
-    for (const AstGenericTypePack& genericPack : genericPackNames)
+    for (const AstGenericTypePack* genericPack : genericPackNames)
     {
         std::optional<TypePackId> defaultValue;
 
-        if (genericPack.defaultValue)
+        if (genericPack->defaultValue)
-            defaultValue = resolveTypePack(scope, *genericPack.defaultValue);
+            defaultValue = resolveTypePack(scope, *genericPack->defaultValue);
 
-        Name n = genericPack.name.value;
+        Name n = genericPack->name.value;
 
         // These generics are the only thing that will ever be added to scope, so we can be certain that
         // a collision can only occur when two generic types have the same name.
@@ -6418,7 +6373,7 @@ void TypeChecker::resolve(const TypeGuardPredicate& typeguardP, RefinementMap& r
     }
 
     // We're only interested in the root class of any classes.
-    if (auto ctv = get<ClassType>(type); !ctv || ctv->parent != builtinTypes->classType)
+    if (auto ctv = get<ClassType>(type); !ctv || (ctv->parent != builtinTypes->classType && !hasTag(type, kTypeofRootTag)))
         return addRefinement(refis, typeguardP.lvalue, errorRecoveryType(scope));
 
     // This probably hints at breaking out type filtering functions from the predicate solver so that typeof is not tightly coupled with IsA.

Analysis/src/TypePath.cpp

@@ -14,7 +14,7 @@
 #include <type_traits>
 
 LUAU_FASTFLAG(LuauSolverV2);
-
+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.
@@ -156,6 +156,7 @@ Path PathBuilder::build()
 
 PathBuilder& PathBuilder::readProp(std::string name)
 {
+    if (!FFlag::LuauDisableNewSolverAssertsInMixedMode)
         LUAU_ASSERT(FFlag::LuauSolverV2);
     components.push_back(Property{std::move(name), true});
     return *this;
@@ -163,6 +164,7 @@ PathBuilder& PathBuilder::readProp(std::string name)
 
 PathBuilder& PathBuilder::writeProp(std::string name)
 {
+    if (!FFlag::LuauDisableNewSolverAssertsInMixedMode)
         LUAU_ASSERT(FFlag::LuauSolverV2);
     components.push_back(Property{std::move(name), false});
     return *this;
@@ -415,6 +417,14 @@ struct TraversalState
 
         switch (field)
         {
+        case TypePath::TypeField::Table:
+            if (auto mt = get<MetatableType>(current))
+            {
+                updateCurrent(mt->table);
+                return true;
+            }
+
+            return false;
         case TypePath::TypeField::Metatable:
             if (auto currentType = get<TypeId>(current))
             {
@@ -561,6 +571,9 @@ std::string toString(const TypePath::Path& path, bool prefixDot)
 
             switch (c)
             {
+            case TypePath::TypeField::Table:
+                result << "table";
+                break;
             case TypePath::TypeField::Metatable:
                 result << "metatable";
                 break;

Analysis/src/TypeUtils.cpp

@@ -5,12 +5,16 @@
 #include "Luau/Normalize.h"
 #include "Luau/Scope.h"
 #include "Luau/ToString.h"
+#include "Luau/Type.h"
 #include "Luau/TypeInfer.h"
 
 #include <algorithm>
 
 LUAU_FASTFLAG(LuauSolverV2);
-
+LUAU_FASTFLAG(LuauAutocompleteRefactorsForIncrementalAutocomplete);
+LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope);
+LUAU_FASTFLAG(LuauFreeTypesMustHaveBounds)
+LUAU_FASTFLAG(LuauDisableNewSolverAssertsInMixedMode)
 namespace Luau
 {
 
@@ -317,9 +321,11 @@ TypePack extendTypePack(
                     {
                         FreeType ft{ftp->scope, builtinTypes->neverType, builtinTypes->unknownType};
                         t = arena.addType(ft);
+                        if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+                            trackInteriorFreeType(ftp->scope, t);
                     }
                     else
-                        t = arena.freshType(ftp->scope);
+                        t = FFlag::LuauFreeTypesMustHaveBounds ? arena.freshType(builtinTypes, ftp->scope) : arena.freshType_DEPRECATED(ftp->scope);
                 }
 
                 newPack.head.push_back(t);
@@ -331,7 +337,7 @@ TypePack extendTypePack(
 
             return result;
         }
-        else if (const Unifiable::Error* etp = getMutable<Unifiable::Error>(pack))
+        else if (auto etp = getMutable<ErrorTypePack>(pack))
         {
             while (result.head.size() < length)
                 result.head.push_back(builtinTypes->errorRecoveryType());
@@ -426,7 +432,7 @@ TypeId stripNil(NotNull<BuiltinTypes> builtinTypes, TypeArena& arena, TypeId ty)
 
 ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypeId ty)
 {
-    LUAU_ASSERT(FFlag::LuauSolverV2);
+    LUAU_ASSERT(FFlag::LuauSolverV2 || FFlag::LuauAutocompleteRefactorsForIncrementalAutocomplete);
     std::shared_ptr<const NormalizedType> normType = normalizer->normalize(ty);
 
     if (!normType)
@@ -479,4 +485,87 @@ ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypePackId
     return result;
 }
 
+bool isLiteral(const AstExpr* expr)
+{
+    return (
+        expr->is<AstExprTable>() || expr->is<AstExprFunction>() || expr->is<AstExprConstantNumber>() || expr->is<AstExprConstantString>() ||
+        expr->is<AstExprConstantBool>() || expr->is<AstExprConstantNil>()
+    );
+}
+/**
+ * Visitor which, given an expression and a mapping from expression to TypeId,
+ * determines if there are any literal expressions that contain blocked types.
+ * This is used for bi-directional inference: we want to "apply" a type from
+ * a function argument or a type annotation to a literal.
+ */
+class BlockedTypeInLiteralVisitor : public AstVisitor
+{
+public:
+    explicit BlockedTypeInLiteralVisitor(NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes, NotNull<std::vector<TypeId>> toBlock)
+        : astTypes_{astTypes}
+        , toBlock_{toBlock}
+    {
+    }
+    bool visit(AstNode*) override
+    {
+        return false;
+    }
+
+    bool visit(AstExpr* e) override
+    {
+        auto ty = astTypes_->find(e);
+        if (ty && (get<BlockedType>(follow(*ty)) != nullptr))
+        {
+            toBlock_->push_back(*ty);
+        }
+        return isLiteral(e) || e->is<AstExprGroup>();
+    }
+
+private:
+    NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes_;
+    NotNull<std::vector<TypeId>> toBlock_;
+};
+
+std::vector<TypeId> findBlockedTypesIn(AstExprTable* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes)
+{
+    std::vector<TypeId> toBlock;
+    BlockedTypeInLiteralVisitor v{astTypes, NotNull{&toBlock}};
+    expr->visit(&v);
+    return toBlock;
+}
+
+std::vector<TypeId> findBlockedArgTypesIn(AstExprCall* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes)
+{
+    std::vector<TypeId> toBlock;
+    BlockedTypeInLiteralVisitor v{astTypes, NotNull{&toBlock}};
+    for (auto arg : expr->args)
+    {
+        if (isLiteral(arg) || arg->is<AstExprGroup>())
+        {
+            arg->visit(&v);
+        }
+    }
+    return toBlock;
+}
+
+void trackInteriorFreeType(Scope* scope, TypeId ty)
+{
+    if (FFlag::LuauDisableNewSolverAssertsInMixedMode)
+        LUAU_ASSERT(FFlag::LuauTrackInteriorFreeTypesOnScope);
+    else
+        LUAU_ASSERT(FFlag::LuauSolverV2 && FFlag::LuauTrackInteriorFreeTypesOnScope);
+    for (; scope; scope = scope->parent.get())
+    {
+        if (scope->interiorFreeTypes)
+        {
+            scope->interiorFreeTypes->push_back(ty);
+            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 `interiorFreeTypes` member.");
+}
+
 } // namespace Luau

Analysis/src/Unifiable.cpp

@@ -1,5 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Unifiable.h"
+#include "Luau/TypeFwd.h"
+#include "Luau/TypePack.h"
 
 namespace Luau
 {
@@ -13,12 +15,17 @@ int freshIndex()
     return ++nextIndex;
 }
 
-Error::Error()
+template<typename Id>
+Error<Id>::Error()
     : index(++nextIndex)
 {
 }
 
-int Error::nextIndex = 0;
+template<typename Id>
+int Error<Id>::nextIndex = 0;
+
+template struct Error<TypeId>;
+template struct Error<TypePackId>;
 
 } // namespace Unifiable
 } // namespace Luau

Analysis/src/Unifier2.cpp

@@ -908,7 +908,7 @@ OccursCheckResult Unifier2::occursCheck(DenseHashSet<TypePackId>& seen, TypePack
 
     RecursionLimiter _ra(&recursionCount, recursionLimit);
 
-    while (!getMutable<Unifiable::Error>(haystack))
+    while (!getMutable<ErrorTypePack>(haystack))
     {
         if (needle == haystack)
             return OccursCheckResult::Fail;

Ast/include/Luau/Allocator.h

@@ -0,0 +1,48 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Ast.h"
+#include "Luau/Location.h"
+#include "Luau/DenseHash.h"
+#include "Luau/Common.h"
+
+#include <vector>
+
+namespace Luau
+{
+
+class Allocator
+{
+public:
+    Allocator();
+    Allocator(Allocator&&);
+
+    Allocator& operator=(Allocator&&) = delete;
+
+    ~Allocator();
+
+    void* allocate(size_t size);
+
+    template<typename T, typename... Args>
+    T* alloc(Args&&... args)
+    {
+        static_assert(std::is_trivially_destructible<T>::value, "Objects allocated with this allocator will never have their destructors run!");
+
+        T* t = static_cast<T*>(allocate(sizeof(T)));
+        new (t) T(std::forward<Args>(args)...);
+        return t;
+    }
+
+private:
+    struct Page
+    {
+        Page* next;
+
+        alignas(8) char data[8192];
+    };
+
+    Page* root;
+    size_t offset;
+};
+
+} // namespace Luau

Ast/include/Luau/Ast.h

@@ -120,20 +120,6 @@ struct AstTypeList
 
 using AstArgumentName = std::pair<AstName, Location>; // TODO: remove and replace when we get a common struct for this pair instead of AstName
 
-struct AstGenericType
-{
-    AstName name;
-    Location location;
-    AstType* defaultValue = nullptr;
-};
-
-struct AstGenericTypePack
-{
-    AstName name;
-    Location location;
-    AstTypePack* defaultValue = nullptr;
-};
-
 extern int gAstRttiIndex;
 
 template<typename T>
@@ -253,6 +239,32 @@ public:
     bool hasSemicolon;
 };
 
+class AstGenericType : public AstNode
+{
+public:
+    LUAU_RTTI(AstGenericType)
+
+    explicit AstGenericType(const Location& location, AstName name, AstType* defaultValue = nullptr);
+
+    void visit(AstVisitor* visitor) override;
+
+    AstName name;
+    AstType* defaultValue = nullptr;
+};
+
+class AstGenericTypePack : public AstNode
+{
+public:
+    LUAU_RTTI(AstGenericTypePack)
+
+    explicit AstGenericTypePack(const Location& location, AstName name, AstTypePack* defaultValue = nullptr);
+
+    void visit(AstVisitor* visitor) override;
+
+    AstName name;
+    AstTypePack* defaultValue = nullptr;
+};
+
 class AstExprGroup : public AstExpr
 {
 public:
@@ -316,16 +328,18 @@ public:
 
     enum QuoteStyle
     {
-        Quoted,
+        QuotedSimple,
+        QuotedRaw,
         Unquoted
     };
 
-    AstExprConstantString(const Location& location, const AstArray<char>& value, QuoteStyle quoteStyle = Quoted);
+    AstExprConstantString(const Location& location, const AstArray<char>& value, QuoteStyle quoteStyle);
 
     void visit(AstVisitor* visitor) override;
+    bool isQuoted() const;
 
     AstArray<char> value;
-    QuoteStyle quoteStyle = Quoted;
+    QuoteStyle quoteStyle;
 };
 
 class AstExprLocal : public AstExpr
@@ -422,8 +436,8 @@ public:
     AstExprFunction(
         const Location& location,
         const AstArray<AstAttr*>& attributes,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         AstLocal* self,
         const AstArray<AstLocal*>& args,
         bool vararg,
@@ -441,8 +455,8 @@ public:
     bool hasNativeAttribute() const;
 
     AstArray<AstAttr*> attributes;
-    AstArray<AstGenericType> generics;
+    AstArray<AstGenericType*> generics;
-    AstArray<AstGenericTypePack> genericPacks;
+    AstArray<AstGenericTypePack*> genericPacks;
     AstLocal* self;
     AstArray<AstLocal*> args;
     std::optional<AstTypeList> returnAnnotation;
@@ -855,8 +869,8 @@ public:
         const Location& location,
         const AstName& name,
         const Location& nameLocation,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         AstType* type,
         bool exported
     );
@@ -865,8 +879,8 @@ public:
 
     AstName name;
     Location nameLocation;
-    AstArray<AstGenericType> generics;
+    AstArray<AstGenericType*> generics;
-    AstArray<AstGenericTypePack> genericPacks;
+    AstArray<AstGenericTypePack*> genericPacks;
     AstType* type;
     bool exported;
 };
@@ -876,13 +890,14 @@ class AstStatTypeFunction : public AstStat
 public:
     LUAU_RTTI(AstStatTypeFunction);
 
-    AstStatTypeFunction(const Location& location, const AstName& name, const Location& nameLocation, AstExprFunction* body);
+    AstStatTypeFunction(const Location& location, const AstName& name, const Location& nameLocation, AstExprFunction* body, bool exported);
 
     void visit(AstVisitor* visitor) override;
 
     AstName name;
     Location nameLocation;
     AstExprFunction* body;
+    bool exported;
 };
 
 class AstStatDeclareGlobal : public AstStat
@@ -908,8 +923,8 @@ public:
         const Location& location,
         const AstName& name,
         const Location& nameLocation,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         const AstTypeList& params,
         const AstArray<AstArgumentName>& paramNames,
         bool vararg,
@@ -922,8 +937,8 @@ public:
         const AstArray<AstAttr*>& attributes,
         const AstName& name,
         const Location& nameLocation,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         const AstTypeList& params,
         const AstArray<AstArgumentName>& paramNames,
         bool vararg,
@@ -939,8 +954,8 @@ public:
     AstArray<AstAttr*> attributes;
     AstName name;
     Location nameLocation;
-    AstArray<AstGenericType> generics;
+    AstArray<AstGenericType*> generics;
-    AstArray<AstGenericTypePack> genericPacks;
+    AstArray<AstGenericTypePack*> genericPacks;
     AstTypeList params;
     AstArray<AstArgumentName> paramNames;
     bool vararg = false;
@@ -1071,8 +1086,8 @@ public:
 
     AstTypeFunction(
         const Location& location,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         const AstTypeList& argTypes,
         const AstArray<std::optional<AstArgumentName>>& argNames,
         const AstTypeList& returnTypes
@@ -1081,8 +1096,8 @@ public:
     AstTypeFunction(
         const Location& location,
         const AstArray<AstAttr*>& attributes,
-        const AstArray<AstGenericType>& generics,
+        const AstArray<AstGenericType*>& generics,
-        const AstArray<AstGenericTypePack>& genericPacks,
+        const AstArray<AstGenericTypePack*>& genericPacks,
         const AstTypeList& argTypes,
         const AstArray<std::optional<AstArgumentName>>& argNames,
         const AstTypeList& returnTypes
@@ -1093,8 +1108,8 @@ public:
     bool isCheckedFunction() const;
 
     AstArray<AstAttr*> attributes;
-    AstArray<AstGenericType> generics;
+    AstArray<AstGenericType*> generics;
-    AstArray<AstGenericTypePack> genericPacks;
+    AstArray<AstGenericTypePack*> genericPacks;
     AstTypeList argTypes;
     AstArray<std::optional<AstArgumentName>> argNames;
     AstTypeList returnTypes;
@@ -1201,6 +1216,18 @@ public:
     const AstArray<char> value;
 };
 
+class AstTypeGroup : public AstType
+{
+public:
+    LUAU_RTTI(AstTypeGroup)
+
+    explicit AstTypeGroup(const Location& location, AstType* type);
+
+    void visit(AstVisitor* visitor) override;
+
+    AstType* type;
+};
+
 class AstTypePack : public AstNode
 {
 public:
@@ -1261,6 +1288,16 @@ public:
         return visit(static_cast<AstNode*>(node));
     }
 
+    virtual bool visit(class AstGenericType* node)
+    {
+        return visit(static_cast<AstNode*>(node));
+    }
+
+    virtual bool visit(class AstGenericTypePack* node)
+    {
+        return visit(static_cast<AstNode*>(node));
+    }
+
     virtual bool visit(class AstExpr* node)
     {
         return visit(static_cast<AstNode*>(node));
@@ -1467,6 +1504,10 @@ public:
     {
         return visit(static_cast<AstType*>(node));
     }
+    virtual bool visit(class AstTypeGroup* node)
+    {
+        return visit(static_cast<AstType*>(node));
+    }
     virtual bool visit(class AstTypeError* node)
     {
         return visit(static_cast<AstType*>(node));
@@ -1490,6 +1531,7 @@ public:
     }
 };
 
+bool isLValue(const AstExpr*);
 AstName getIdentifier(AstExpr*);
 Location getLocation(const AstTypeList& typeList);