Sync to upstream/release/588 (#992)

Type checker/autocomplete:
* `Luau::autocomplete` no longer performs typechecking internally, make
sure to run `Frontend::check` before performing autocomplete requests
* Autocomplete string suggestions without "" are now only suggested
inside the ""
* Autocomplete suggestions now include `function (anonymous autofilled)`
key with a full suggestion for the function expression (with arguments
included) stored in `AutocompleteEntry::insertText`
* `AutocompleteEntry::indexedWithSelf` is provided for function call
suggestions made with `:`
* Cyclic modules now see each other type exports as `any` to prevent
memory use-after-free (similar to module return type)

Runtime:
* Updated inline/loop unroll cost model to better handle assignments
(Fixes https://github.com/Roblox/luau/issues/978)
* `math.noise` speed was improved by ~30%
* `table.concat` speed was improved by ~5-7%
* `tonumber` and `tostring` now have fastcall paths that execute ~1.5x
and ~2.5x faster respectively (fixes #777)
* Fixed crash in `luaL_typename` when index refers to a non-existing
value
* Fixed potential out of memory scenario when using `string.sub` or
`string.char` in a loop
* Fixed behavior of some fastcall builtins when called without arguments
under -O2 to match original functions
* Support for native code execution in VM is now enabled by default
(note: native code still has to be generated explicitly)
* `Codegen::compile` now accepts `CodeGen_OnlyNativeModules` flag. When
set, only modules that have a `--!native` hot-comment at the top will be
compiled to native code

In our new typechecker:
* Generic type packs are no longer considered to be variadic during
unification
* Timeout and cancellation now works in new solver
* Fixed false positive errors around 'table' and 'function' type
refinements
* Table literals now use covariant unification rules. This is sound
since literal has no type specified and has no aliases
* Fixed issues with blocked types escaping the constraint solver
* Fixed more places where error messages that should've been suppressed
were still reported
* Fixed errors when iterating over a top table type

In our native code generation (jit):
* 'DebugLuauAbortingChecks' flag is now supported on A64
* LOP_NEWCLOSURE has been translated to IR

Analysis/include/Luau/Autocomplete.h

@@ -38,6 +38,7 @@ enum class AutocompleteEntryKind
     String,
     Type,
     Module,
+    GeneratedFunction,
 };
 
 enum class ParenthesesRecommendation
@@ -70,6 +71,10 @@ struct AutocompleteEntry
     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>;
@@ -94,4 +99,6 @@ using StringCompletionCallback =
 
 AutocompleteResult autocomplete(Frontend& frontend, const ModuleName& moduleName, Position position, StringCompletionCallback callback);
 
+constexpr char kGeneratedAnonymousFunctionEntryName[] = "function (anonymous autofilled)";
+
 } // namespace Luau

Analysis/include/Luau/Config.h

@@ -19,7 +19,7 @@ struct Config
 {
     Config();
 
-    Mode mode;
+    Mode mode = Mode::Nonstrict;
 
     ParseOptions parseOptions;
 

Analysis/include/Luau/ConstraintGraphBuilder.h

@@ -94,12 +94,13 @@ struct ConstraintGraphBuilder
     ScopePtr globalScope;
 
     std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope;
+    std::vector<RequireCycle> requireCycles;
 
     DcrLogger* logger;
 
     ConstraintGraphBuilder(ModulePtr module, TypeArena* arena, NotNull<ModuleResolver> moduleResolver, NotNull<BuiltinTypes> builtinTypes,
         NotNull<InternalErrorReporter> ice, const ScopePtr& globalScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope,
-        DcrLogger* logger, NotNull<DataFlowGraph> dfg);
+        DcrLogger* logger, NotNull<DataFlowGraph> dfg, std::vector<RequireCycle> requireCycles);
 
     /**
      * Fabricates a new free type belonging to a given scope.

Analysis/include/Luau/ConstraintSolver.h

@@ -8,6 +8,7 @@
 #include "Luau/Normalize.h"
 #include "Luau/ToString.h"
 #include "Luau/Type.h"
+#include "Luau/TypeCheckLimits.h"
 #include "Luau/Variant.h"
 
 #include <vector>
@@ -81,9 +82,11 @@ struct ConstraintSolver
     std::vector<RequireCycle> requireCycles;
 
     DcrLogger* logger;
+    TypeCheckLimits limits;
 
     explicit ConstraintSolver(NotNull<Normalizer> normalizer, NotNull<Scope> rootScope, std::vector<NotNull<Constraint>> constraints,
-        ModuleName moduleName, NotNull<ModuleResolver> moduleResolver, std::vector<RequireCycle> requireCycles, DcrLogger* logger);
+        ModuleName moduleName, NotNull<ModuleResolver> moduleResolver, std::vector<RequireCycle> requireCycles, DcrLogger* logger,
+        TypeCheckLimits limits);
 
     // Randomize the order in which to dispatch constraints
     void randomize(unsigned seed);
@@ -280,6 +283,9 @@ private:
 
     TypePackId anyifyModuleReturnTypePackGenerics(TypePackId tp);
 
+    void throwTimeLimitError();
+    void throwUserCancelError();
+
     ToStringOptions opts;
 };
 

Analysis/include/Luau/Differ.h

@@ -1,9 +1,11 @@
 // 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/Type.h"
 #include <optional>
 #include <string>
+#include <unordered_map>
 
 namespace Luau
 {
@@ -17,6 +19,7 @@ struct DiffPathNode
         FunctionReturn,
         Union,
         Intersection,
+        Negation,
     };
     Kind kind;
     // non-null when TableProperty
@@ -54,11 +57,15 @@ struct DiffPathNodeLeaf
     std::optional<Name> tableProperty;
     std::optional<int> minLength;
     bool isVariadic;
-    DiffPathNodeLeaf(std::optional<TypeId> ty, std::optional<Name> tableProperty, std::optional<int> minLength, bool isVariadic)
+    // TODO: Rename to anonymousIndex, for both union and Intersection
+    std::optional<size_t> unionIndex;
+    DiffPathNodeLeaf(
+        std::optional<TypeId> ty, std::optional<Name> tableProperty, std::optional<int> minLength, bool isVariadic, std::optional<size_t> unionIndex)
         : ty(ty)
         , tableProperty(tableProperty)
         , minLength(minLength)
         , isVariadic(isVariadic)
+        , unionIndex(unionIndex)
     {
     }
 
@@ -66,6 +73,8 @@ struct DiffPathNodeLeaf
 
     static DiffPathNodeLeaf detailsTableProperty(TypeId ty, Name tableProperty);
 
+    static DiffPathNodeLeaf detailsUnionIndex(TypeId ty, size_t index);
+
     static DiffPathNodeLeaf detailsLength(int minLength, bool isVariadic);
 
     static DiffPathNodeLeaf nullopts();
@@ -82,11 +91,12 @@ struct DiffError
     enum Kind
     {
         Normal,
-        MissingProperty,
+        MissingTableProperty,
+        MissingUnionMember,
+        MissingIntersectionMember,
+        IncompatibleGeneric,
         LengthMismatchInFnArgs,
         LengthMismatchInFnRets,
-        LengthMismatchInUnion,
-        LengthMismatchInIntersection,
     };
     Kind kind;
 
@@ -141,6 +151,8 @@ struct DifferEnvironment
 {
     TypeId rootLeft;
     TypeId rootRight;
+
+    DenseHashMap<TypeId, TypeId> genericMatchedPairs;
 };
 DifferResult diff(TypeId ty1, TypeId ty2);
 

Analysis/include/Luau/Frontend.h

@@ -6,6 +6,7 @@
 #include "Luau/ModuleResolver.h"
 #include "Luau/RequireTracer.h"
 #include "Luau/Scope.h"
+#include "Luau/TypeCheckLimits.h"
 #include "Luau/TypeInfer.h"
 #include "Luau/Variant.h"
 
@@ -189,14 +190,6 @@ struct Frontend
     std::optional<CheckResult> getCheckResult(const ModuleName& name, bool accumulateNested, bool forAutocomplete = false);
 
 private:
-    struct TypeCheckLimits
-    {
-        std::optional<double> finishTime;
-        std::optional<int> instantiationChildLimit;
-        std::optional<int> unifierIterationLimit;
-        std::shared_ptr<FrontendCancellationToken> cancellationToken;
-    };
-
     ModulePtr check(const SourceModule& sourceModule, Mode mode, std::vector<RequireCycle> requireCycles, std::optional<ScopePtr> environmentScope,
         bool forAutocomplete, bool recordJsonLog, TypeCheckLimits typeCheckLimits);
 
@@ -248,11 +241,12 @@ public:
 
 ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle>& requireCycles, NotNull<BuiltinTypes> builtinTypes,
     NotNull<InternalErrorReporter> iceHandler, NotNull<ModuleResolver> moduleResolver, NotNull<FileResolver> fileResolver,
-    const ScopePtr& globalScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options);
+    const ScopePtr& globalScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options,
+    TypeCheckLimits limits);
 
 ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle>& requireCycles, NotNull<BuiltinTypes> builtinTypes,
     NotNull<InternalErrorReporter> iceHandler, NotNull<ModuleResolver> moduleResolver, NotNull<FileResolver> fileResolver,
     const ScopePtr& globalScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options,
-    bool recordJsonLog);
+    TypeCheckLimits limits, bool recordJsonLog);
 
 } // namespace Luau

Analysis/include/Luau/Normalize.h

@@ -277,6 +277,9 @@ struct NormalizedType
     /// Returns true if this type should result in error suppressing behavior.
     bool shouldSuppressErrors() const;
 
+    /// Returns true if this type contains the primitve top table type, `table`.
+    bool hasTopTable() const;
+
     // Helpers that improve readability of the above (they just say if the component is present)
     bool hasTops() const;
     bool hasBooleans() const;

Analysis/include/Luau/Symbol.h

@@ -6,8 +6,6 @@
 
 #include <string>
 
-LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
-
 namespace Luau
 {
 
@@ -42,17 +40,7 @@ struct Symbol
         return local != nullptr || global.value != nullptr;
     }
 
-    bool operator==(const Symbol& rhs) const
-    {
-        if (local)
-            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::DebugLuauDeferredConstraintResolution)
-            return !rhs.local && !rhs.global.value; // Reflexivity: we already know `this` Symbol is empty, so check that rhs is.
-        else
-            return false;
-    }
+    bool operator==(const Symbol& rhs) const;
 
     bool operator!=(const Symbol& rhs) const
     {

Analysis/include/Luau/TypeArena.h

@@ -9,12 +9,16 @@
 
 namespace Luau
 {
+struct Module;
 
 struct TypeArena
 {
     TypedAllocator<Type> types;
     TypedAllocator<TypePackVar> typePacks;
 
+    // Owning module, if any
+    Module* owningModule = nullptr;
+
     void clear();
 
     template<typename T>

Analysis/include/Luau/TypeCheckLimits.h

@@ -0,0 +1,41 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Cancellation.h"
+#include "Luau/Error.h"
+
+#include <memory>
+#include <optional>
+#include <string>
+
+namespace Luau
+{
+
+class TimeLimitError : public InternalCompilerError
+{
+public:
+    explicit TimeLimitError(const std::string& moduleName)
+        : InternalCompilerError("Typeinfer failed to complete in allotted time", moduleName)
+    {
+    }
+};
+
+class UserCancelError : public InternalCompilerError
+{
+public:
+    explicit UserCancelError(const std::string& moduleName)
+        : InternalCompilerError("Analysis has been cancelled by user", moduleName)
+    {
+    }
+};
+
+struct TypeCheckLimits
+{
+    std::optional<double> finishTime;
+    std::optional<int> instantiationChildLimit;
+    std::optional<int> unifierIterationLimit;
+
+    std::shared_ptr<FrontendCancellationToken> cancellationToken;
+};
+
+} // namespace Luau

Analysis/include/Luau/TypeInfer.h

@@ -10,6 +10,7 @@
 #include "Luau/Symbol.h"
 #include "Luau/TxnLog.h"
 #include "Luau/Type.h"
+#include "Luau/TypeCheckLimits.h"
 #include "Luau/TypePack.h"
 #include "Luau/TypeUtils.h"
 #include "Luau/Unifier.h"
@@ -56,24 +57,6 @@ struct HashBoolNamePair
     size_t operator()(const std::pair<bool, Name>& pair) const;
 };
 
-class TimeLimitError : public InternalCompilerError
-{
-public:
-    explicit TimeLimitError(const std::string& moduleName)
-        : InternalCompilerError("Typeinfer failed to complete in allotted time", moduleName)
-    {
-    }
-};
-
-class UserCancelError : public InternalCompilerError
-{
-public:
-    explicit UserCancelError(const std::string& moduleName)
-        : InternalCompilerError("Analysis has been cancelled by user", moduleName)
-    {
-    }
-};
-
 struct GlobalTypes
 {
     GlobalTypes(NotNull<BuiltinTypes> builtinTypes);

Analysis/include/Luau/TypeUtils.h

@@ -14,6 +14,7 @@ namespace Luau
 
 struct TxnLog;
 struct TypeArena;
+class Normalizer;
 
 enum class ValueContext
 {
@@ -55,6 +56,51 @@ std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types);
  */
 TypeId stripNil(NotNull<BuiltinTypes> builtinTypes, TypeArena& arena, TypeId ty);
 
+enum class ErrorSuppression
+{
+    Suppress,
+    DoNotSuppress,
+    NormalizationFailed
+};
+
+/**
+ * Normalizes the given type using the normalizer to determine if the type
+ * should suppress any errors that would be reported involving it.
+ * @param normalizer the normalizer to use
+ * @param ty the type to check for error suppression
+ * @returns an enum indicating whether or not to suppress the error or to signal a normalization failure
+ */
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypeId ty);
+
+/**
+ * Flattens and normalizes the given typepack using the normalizer to determine if the type
+ * should suppress any errors that would be reported involving it.
+ * @param normalizer the normalizer to use
+ * @param tp the typepack to check for error suppression
+ * @returns an enum indicating whether or not to suppress the error or to signal a normalization failure
+ */
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypePackId tp);
+
+/**
+ * Normalizes the two given type using the normalizer to determine if either type
+ * should suppress any errors that would be reported involving it.
+ * @param normalizer the normalizer to use
+ * @param ty1 the first type to check for error suppression
+ * @param ty2 the second type to check for error suppression
+ * @returns an enum indicating whether or not to suppress the error or to signal a normalization failure
+ */
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypeId ty1, TypeId ty2);
+
+/**
+ * Flattens and normalizes the two given typepacks using the normalizer to determine if either type
+ * should suppress any errors that would be reported involving it.
+ * @param normalizer the normalizer to use
+ * @param tp1 the first typepack to check for error suppression
+ * @param tp2 the second typepack to check for error suppression
+ * @returns an enum indicating whether or not to suppress the error or to signal a normalization failure
+ */
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypePackId tp1, TypePackId tp2);
+
 template<typename T, typename Ty>
 const T* get(std::optional<Ty> ty)
 {

Analysis/include/Luau/Unifier.h

@@ -43,6 +43,21 @@ struct Widen : Substitution
     TypePackId operator()(TypePackId ty);
 };
 
+/**
+ * Normally, when we unify table properties, we must do so invariantly, but we
+ * can introduce a special exception: If the table property in the subtype
+ * position arises from a literal expression, it is safe to instead perform a
+ * covariant check.
+ *
+ * This is very useful for typechecking cases where table literals (and trees of
+ * table literals) are passed directly to functions.
+ *
+ * In this case, we know that the property has no other name referring to it and
+ * so it is perfectly safe for the function to mutate the table any way it
+ * wishes.
+ */
+using LiteralProperties = DenseHashSet<Name>;
+
 // TODO: Use this more widely.
 struct UnifierOptions
 {
@@ -80,7 +95,7 @@ struct Unifier
 
     // Configure the Unifier to test for scope subsumption via embedded Scope
     // pointers rather than TypeLevels.
-    void enableScopeTests();
+    void enableNewSolver();
 
     // Test whether the two type vars unify.  Never commits the result.
     ErrorVec canUnify(TypeId subTy, TypeId superTy);
@@ -90,10 +105,10 @@ struct Unifier
      * Populate the vector errors with any type errors that may arise.
      * Populate the transaction log with the set of TypeIds that need to be reset to undo the unification attempt.
      */
-    void tryUnify(TypeId subTy, TypeId superTy, bool isFunctionCall = false, bool isIntersection = false);
+    void tryUnify(TypeId subTy, TypeId superTy, bool isFunctionCall = false, bool isIntersection = false, const LiteralProperties* aliasableMap = nullptr);
 
 private:
-    void tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall = false, bool isIntersection = false);
+    void tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall = false, bool isIntersection = false, const LiteralProperties* aliasableMap = nullptr);
     void tryUnifyUnionWithType(TypeId subTy, const UnionType* uv, TypeId superTy);
 
     // Traverse the two types provided and block on any BlockedTypes we find.
@@ -108,7 +123,7 @@ private:
     void tryUnifyPrimitives(TypeId subTy, TypeId superTy);
     void tryUnifySingletons(TypeId subTy, TypeId superTy);
     void tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCall = false);
-    void tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection = false);
+    void tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection = false, const LiteralProperties* aliasableMap = nullptr);
     void tryUnifyScalarShape(TypeId subTy, TypeId superTy, bool reversed);
     void tryUnifyWithMetatable(TypeId subTy, TypeId superTy, bool reversed);
     void tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed);
@@ -163,8 +178,10 @@ private:
     // Available after regular type pack unification errors
     std::optional<int> firstPackErrorPos;
 
-    // If true, we use the scope hierarchy rather than TypeLevels
-    bool useScopes = false;
+    // 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/src/Autocomplete.cpp

@@ -13,6 +13,10 @@
 #include <utility>
 
 LUAU_FASTFLAG(DebugLuauReadWriteProperties)
+LUAU_FASTFLAGVARIABLE(LuauDisableCompletionOutsideQuotes, false)
+LUAU_FASTFLAGVARIABLE(LuauAnonymousAutofilled, false);
+LUAU_FASTFLAGVARIABLE(LuauAutocompleteLastTypecheck, false)
+LUAU_FASTFLAGVARIABLE(LuauAutocompleteHideSelfArg, false)
 
 static const std::unordered_set<std::string> kStatementStartingKeywords = {
     "while", "if", "local", "repeat", "function", "do", "for", "return", "break", "continue", "type", "export"};
@@ -280,18 +284,38 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, NotNul
                 ParenthesesRecommendation parens =
                     indexType == PropIndexType::Key ? ParenthesesRecommendation::None : getParenRecommendation(type, nodes, typeCorrect);
 
-                result[name] = AutocompleteEntry{
-                    AutocompleteEntryKind::Property,
-                    type,
-                    prop.deprecated,
-                    isWrongIndexer(type),
-                    typeCorrect,
-                    containingClass,
-                    &prop,
-                    prop.documentationSymbol,
-                    {},
-                    parens,
-                };
+                if (FFlag::LuauAutocompleteHideSelfArg)
+                {
+                    result[name] = AutocompleteEntry{
+                        AutocompleteEntryKind::Property,
+                        type,
+                        prop.deprecated,
+                        isWrongIndexer(type),
+                        typeCorrect,
+                        containingClass,
+                        &prop,
+                        prop.documentationSymbol,
+                        {},
+                        parens,
+                        {},
+                        indexType == PropIndexType::Colon
+                    };
+                }
+                else
+                {
+                    result[name] = AutocompleteEntry{
+                        AutocompleteEntryKind::Property,
+                        type,
+                        prop.deprecated,
+                        isWrongIndexer(type),
+                        typeCorrect,
+                        containingClass,
+                        &prop,
+                        prop.documentationSymbol,
+                        {},
+                        parens
+                    };
+                }
             }
         }
     };
@@ -591,14 +615,14 @@ std::optional<TypeId> getLocalTypeInScopeAt(const Module& module, Position posit
     return {};
 }
 
-static std::optional<Name> tryGetTypeNameInScope(ScopePtr scope, TypeId ty)
+template <typename T>
+static std::optional<std::string> tryToStringDetailed(const ScopePtr& scope, T ty, bool functionTypeArguments)
 {
-    if (!canSuggestInferredType(scope, ty))
-        return std::nullopt;
-
+    LUAU_ASSERT(FFlag::LuauAnonymousAutofilled);
     ToStringOptions opts;
     opts.useLineBreaks = false;
     opts.hideTableKind = true;
+    opts.functionTypeArguments = functionTypeArguments;
     opts.scope = scope;
     ToStringResult name = toStringDetailed(ty, opts);
 
@@ -608,6 +632,30 @@ static std::optional<Name> tryGetTypeNameInScope(ScopePtr scope, TypeId ty)
     return name.name;
 }
 
+static std::optional<Name> tryGetTypeNameInScope(ScopePtr scope, TypeId ty, bool functionTypeArguments = false)
+{
+    if (!canSuggestInferredType(scope, ty))
+        return std::nullopt;
+
+    if (FFlag::LuauAnonymousAutofilled)
+    {
+        return tryToStringDetailed(scope, ty, functionTypeArguments);
+    }
+    else
+    {
+        ToStringOptions opts;
+        opts.useLineBreaks = false;
+        opts.hideTableKind = true;
+        opts.scope = scope;
+        ToStringResult name = toStringDetailed(ty, opts);
+
+        if (name.error || name.invalid || name.cycle || name.truncated)
+            return std::nullopt;
+
+        return name.name;
+    }
+}
+
 static bool tryAddTypeCorrectSuggestion(AutocompleteEntryMap& result, ScopePtr scope, AstType* topType, TypeId inferredType, Position position)
 {
     std::optional<TypeId> ty;
@@ -1297,6 +1345,14 @@ static std::optional<AutocompleteEntryMap> autocompleteStringParams(const Source
         return std::nullopt;
     }
 
+    if (FFlag::LuauDisableCompletionOutsideQuotes && !nodes.back()->is<AstExprError>())
+    {
+        if (nodes.back()->location.end == position || nodes.back()->location.begin == position)
+        {
+            return std::nullopt;
+        }
+    }
+
     AstExprCall* candidate = nodes.at(nodes.size() - 2)->as<AstExprCall>();
     if (!candidate)
     {
@@ -1361,6 +1417,140 @@ static AutocompleteResult autocompleteWhileLoopKeywords(std::vector<AstNode*> an
     return {std::move(ret), std::move(ancestry), AutocompleteContext::Keyword};
 }
 
+static std::string makeAnonymous(const ScopePtr& scope, const FunctionType& funcTy)
+{
+    LUAU_ASSERT(FFlag::LuauAnonymousAutofilled);
+    std::string result = "function(";
+
+    auto [args, tail] = Luau::flatten(funcTy.argTypes);
+
+    bool first = true;
+    // Skip the implicit 'self' argument if call is indexed with ':'
+    for (size_t argIdx = 0; argIdx < args.size(); ++argIdx)
+    {
+        if (!first)
+            result += ", ";
+        else
+            first = false;
+
+        std::string name;
+        if (argIdx < funcTy.argNames.size() && funcTy.argNames[argIdx])
+            name = funcTy.argNames[argIdx]->name;
+        else
+            name = "a" + std::to_string(argIdx);
+
+        if (std::optional<Name> type = tryGetTypeNameInScope(scope, args[argIdx], true))
+            result += name + ": " + *type; 
+        else
+            result += name;
+    }
+
+    if (tail && (Luau::isVariadic(*tail) || Luau::get<Luau::FreeTypePack>(Luau::follow(*tail))))
+    {
+        if (!first)
+            result += ", ";
+
+        std::optional<std::string> varArgType;
+        if (const VariadicTypePack* pack = get<VariadicTypePack>(follow(*tail)))
+        {
+            if (std::optional<std::string> res = tryToStringDetailed(scope, pack->ty, true))
+                varArgType = std::move(res);
+        }
+        
+        if (varArgType)
+            result += "...: " + *varArgType;
+        else
+            result += "...";
+    }
+
+    result += ")";
+
+    auto [rets, retTail] = Luau::flatten(funcTy.retTypes);
+    if (const size_t totalRetSize = rets.size() + (retTail ? 1 : 0); totalRetSize > 0)
+    {
+        if (std::optional<std::string> returnTypes = tryToStringDetailed(scope, funcTy.retTypes, true))
+        {
+            result += ": ";
+            bool wrap = totalRetSize != 1;
+            if (wrap)
+                result += "(";
+            result += *returnTypes;
+            if (wrap)
+                result += ")";
+        }
+    }
+    result += "  end";
+    return result;
+}
+
+static std::optional<AutocompleteEntry> makeAnonymousAutofilled(const ModulePtr& module, Position position, const AstNode* node, const std::vector<AstNode*>& ancestry)
+{
+    LUAU_ASSERT(FFlag::LuauAnonymousAutofilled);
+    const AstExprCall* call = node->as<AstExprCall>();
+    if (!call && ancestry.size() > 1)
+        call = ancestry[ancestry.size() - 2]->as<AstExprCall>();
+
+    if (!call)
+        return std::nullopt;
+
+    if (!call->location.containsClosed(position) || call->func->location.containsClosed(position))
+        return std::nullopt;
+
+    TypeId* typeIter = module->astTypes.find(call->func);
+    if (!typeIter)
+        return std::nullopt;
+
+    const FunctionType* outerFunction = get<FunctionType>(follow(*typeIter));
+    if (!outerFunction)
+        return std::nullopt;
+
+    size_t argument = 0;
+    for (size_t i = 0; i < call->args.size; ++i)
+    {
+        if (call->args.data[i]->location.containsClosed(position))
+        {
+            argument = i;
+            break;
+        }
+    }
+
+    if (call->self)
+        argument++;
+
+    std::optional<TypeId> argType;
+    auto [args, tail] = flatten(outerFunction->argTypes);
+    if (argument < args.size())
+        argType = args[argument];
+    
+    if (!argType)
+        return std::nullopt;
+    
+    TypeId followed = follow(*argType);
+    const FunctionType* type = get<FunctionType>(followed);
+    if (!type)
+    {
+        if (const UnionType* unionType = get<UnionType>(followed))
+        {
+            if (std::optional<const FunctionType*> nonnullFunction = returnFirstNonnullOptionOfType<FunctionType>(unionType))
+                type = *nonnullFunction;
+        }
+    }
+
+    if (!type)
+        return std::nullopt;
+
+    const ScopePtr scope = findScopeAtPosition(*module, position);
+    if (!scope)
+        return std::nullopt;
+
+    AutocompleteEntry entry;
+    entry.kind = AutocompleteEntryKind::GeneratedFunction;
+    entry.typeCorrect = TypeCorrectKind::Correct;
+    entry.type = argType;
+    entry.insertText = makeAnonymous(scope, *type);
+    return std::make_optional(std::move(entry));
+}
+
 static AutocompleteResult autocomplete(const SourceModule& sourceModule, const ModulePtr& module, NotNull<BuiltinTypes> builtinTypes,
     TypeArena* typeArena, Scope* globalScope, Position position, StringCompletionCallback callback)
 {
@@ -1612,7 +1802,19 @@ static AutocompleteResult autocomplete(const SourceModule& sourceModule, const M
         return {};
 
     if (node->asExpr())
-        return autocompleteExpression(sourceModule, *module, builtinTypes, typeArena, ancestry, position);
+    {
+        if (FFlag::LuauAnonymousAutofilled)
+        {
+            AutocompleteResult ret = autocompleteExpression(sourceModule, *module, builtinTypes, typeArena, ancestry, position);
+            if (std::optional<AutocompleteEntry> generated = makeAnonymousAutofilled(module, position, node, ancestry))
+                ret.entryMap[kGeneratedAnonymousFunctionEntryName] = std::move(*generated);
+            return ret;
+        }
+        else
+        {
+            return autocompleteExpression(sourceModule, *module, builtinTypes, typeArena, ancestry, position);
+        }
+    }
     else if (node->asStat())
         return {autocompleteStatement(sourceModule, *module, ancestry, position), ancestry, AutocompleteContext::Statement};
 
@@ -1621,11 +1823,14 @@ static AutocompleteResult autocomplete(const SourceModule& sourceModule, const M
 
 AutocompleteResult autocomplete(Frontend& frontend, const ModuleName& moduleName, Position position, StringCompletionCallback callback)
 {
-    // FIXME: We can improve performance here by parsing without checking.
-    // The old type graph is probably fine. (famous last words!)
-    FrontendOptions opts;
-    opts.forAutocomplete = true;
-    frontend.check(moduleName, opts);
+    if (!FFlag::LuauAutocompleteLastTypecheck)
+    {
+        // FIXME: We can improve performance here by parsing without checking.
+        // The old type graph is probably fine. (famous last words!)
+        FrontendOptions opts;
+        opts.forAutocomplete = true;
+        frontend.check(moduleName, opts);
+    }
 
     const SourceModule* sourceModule = frontend.getSourceModule(moduleName);
     if (!sourceModule)

Analysis/src/Config.cpp

@@ -4,15 +4,12 @@
 #include "Luau/Lexer.h"
 #include "Luau/StringUtils.h"
 
-LUAU_FASTFLAGVARIABLE(LuauEnableNonstrictByDefaultForLuauConfig, false)
-
 namespace Luau
 {
 
 using Error = std::optional<std::string>;
 
 Config::Config()
-    : mode(FFlag::LuauEnableNonstrictByDefaultForLuauConfig ? Mode::Nonstrict : Mode::NoCheck)
 {
     enabledLint.setDefaults();
 }

Analysis/src/ConstraintGraphBuilder.cpp

@@ -139,7 +139,8 @@ void forEachConstraint(const Checkpoint& start, const Checkpoint& end, const Con
 
 ConstraintGraphBuilder::ConstraintGraphBuilder(ModulePtr module, TypeArena* arena, NotNull<ModuleResolver> moduleResolver,
     NotNull<BuiltinTypes> builtinTypes, NotNull<InternalErrorReporter> ice, const ScopePtr& globalScope,
-    std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, DcrLogger* logger, NotNull<DataFlowGraph> dfg)
+    std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, DcrLogger* logger, NotNull<DataFlowGraph> dfg,
+    std::vector<RequireCycle> requireCycles)
     : module(module)
     , builtinTypes(builtinTypes)
     , arena(arena)
@@ -149,6 +150,7 @@ ConstraintGraphBuilder::ConstraintGraphBuilder(ModulePtr module, TypeArena* aren
     , ice(ice)
     , globalScope(globalScope)
     , prepareModuleScope(std::move(prepareModuleScope))
+    , requireCycles(std::move(requireCycles))
     , logger(logger)
 {
     LUAU_ASSERT(module);
@@ -703,6 +705,16 @@ ControlFlow ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* l
                     {
                         scope->importedTypeBindings[name] = module->exportedTypeBindings;
                         scope->importedModules[name] = moduleInfo->name;
+
+                        // Imported types of requires that transitively refer to current module have to be replaced with 'any'
+                        for (const auto& [location, path] : requireCycles)
+                        {
+                            if (!path.empty() && path.front() == moduleInfo->name)
+                            {
+                                for (auto& [name, tf] : scope->importedTypeBindings[name])
+                                    tf = TypeFun{{}, {}, builtinTypes->anyType};
+                            }
+                        }
                     }
                 }
             }
@@ -1913,6 +1925,9 @@ std::tuple<TypeId, TypeId, RefinementId> ConstraintGraphBuilder::checkBinary(
         NullableBreadcrumbId bc = dfg->getBreadcrumb(typeguard->target);
         if (!bc)
             return {leftType, rightType, nullptr};
+        auto augmentForErrorSupression = [&](TypeId ty) -> TypeId {
+            return arena->addType(UnionType{{ty, builtinTypes->errorType}});
+        };
 
         TypeId discriminantTy = builtinTypes->neverType;
         if (typeguard->type == "nil")
@@ -1926,9 +1941,9 @@ std::tuple<TypeId, TypeId, RefinementId> ConstraintGraphBuilder::checkBinary(
         else if (typeguard->type == "thread")
             discriminantTy = builtinTypes->threadType;
         else if (typeguard->type == "table")
-            discriminantTy = builtinTypes->tableType;
+            discriminantTy = augmentForErrorSupression(builtinTypes->tableType);
         else if (typeguard->type == "function")
-            discriminantTy = builtinTypes->functionType;
+            discriminantTy = augmentForErrorSupression(builtinTypes->functionType);
         else if (typeguard->type == "userdata")
         {
             // For now, we don't really care about being accurate with userdata if the typeguard was using typeof.

Analysis/src/ConstraintSolver.cpp

@@ -12,6 +12,7 @@
 #include "Luau/ModuleResolver.h"
 #include "Luau/Quantify.h"
 #include "Luau/Simplify.h"
+#include "Luau/TimeTrace.h"
 #include "Luau/ToString.h"
 #include "Luau/Type.h"
 #include "Luau/TypeFamily.h"
@@ -259,7 +260,7 @@ struct InstantiationQueuer : TypeOnceVisitor
 };
 
 ConstraintSolver::ConstraintSolver(NotNull<Normalizer> normalizer, NotNull<Scope> rootScope, std::vector<NotNull<Constraint>> constraints,
-    ModuleName moduleName, NotNull<ModuleResolver> moduleResolver, std::vector<RequireCycle> requireCycles, DcrLogger* logger)
+    ModuleName moduleName, NotNull<ModuleResolver> moduleResolver, std::vector<RequireCycle> requireCycles, DcrLogger* logger, TypeCheckLimits limits)
     : arena(normalizer->arena)
     , builtinTypes(normalizer->builtinTypes)
     , normalizer(normalizer)
@@ -269,6 +270,7 @@ ConstraintSolver::ConstraintSolver(NotNull<Normalizer> normalizer, NotNull<Scope
     , moduleResolver(moduleResolver)
     , requireCycles(requireCycles)
     , logger(logger)
+    , limits(std::move(limits))
 {
     opts.exhaustive = true;
 
@@ -334,6 +336,11 @@ void ConstraintSolver::run()
                 continue;
             }
 
+            if (limits.finishTime && TimeTrace::getClock() > *limits.finishTime)
+                throwTimeLimitError();
+            if (limits.cancellationToken && limits.cancellationToken->requested())
+                throwUserCancelError();
+
             std::string saveMe = FFlag::DebugLuauLogSolver ? toString(*c, opts) : std::string{};
             StepSnapshot snapshot;
 
@@ -555,6 +562,9 @@ bool ConstraintSolver::tryDispatch(const InstantiationConstraint& c, NotNull<con
 
     Instantiation inst(TxnLog::empty(), arena, TypeLevel{}, constraint->scope);
 
+    if (limits.instantiationChildLimit)
+        inst.childLimit = *limits.instantiationChildLimit;
+
     std::optional<TypeId> instantiated = inst.substitute(c.superType);
 
     LUAU_ASSERT(get<BlockedType>(c.subType));
@@ -586,7 +596,7 @@ bool ConstraintSolver::tryDispatch(const UnaryConstraint& c, NotNull<const Const
     if (isBlocked(operandType))
         return block(operandType, constraint);
 
-    if (get<FreeType>(operandType))
+    if (!force && get<FreeType>(operandType))
         return block(operandType, constraint);
 
     LUAU_ASSERT(get<BlockedType>(c.resultType));
@@ -713,6 +723,10 @@ bool ConstraintSolver::tryDispatch(const BinaryConstraint& c, NotNull<const Cons
         if (mm)
         {
             Instantiation instantiation{TxnLog::empty(), arena, TypeLevel{}, constraint->scope};
+
+            if (limits.instantiationChildLimit)
+                instantiation.childLimit = *limits.instantiationChildLimit;
+
             std::optional<TypeId> instantiatedMm = instantiation.substitute(*mm);
             if (!instantiatedMm)
             {
@@ -1318,6 +1332,9 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
 
     Instantiation inst(TxnLog::empty(), arena, TypeLevel{}, constraint->scope);
 
+    if (limits.instantiationChildLimit)
+        inst.childLimit = *limits.instantiationChildLimit;
+
     std::vector<TypeId> arityMatchingOverloads;
     std::optional<TxnLog> bestOverloadLog;
 
@@ -1334,7 +1351,7 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
         }
 
         Unifier u{normalizer, constraint->scope, Location{}, Covariant};
-        u.enableScopeTests();
+        u.enableNewSolver();
 
         u.tryUnify(*instantiated, inferredTy, /* isFunctionCall */ true);
 
@@ -1384,7 +1401,7 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
     if (!bestOverloadLog)
     {
         Unifier u{normalizer, constraint->scope, Location{}, Covariant};
-        u.enableScopeTests();
+        u.enableNewSolver();
 
         u.tryUnify(inferredTy, builtinTypes->anyType);
         u.tryUnify(fn, builtinTypes->anyType);
@@ -1505,6 +1522,7 @@ static void updateTheTableType(
 
     for (size_t i = 0; i < path.size() - 1; ++i)
     {
+        t = follow(t);
         auto propTy = findTablePropertyRespectingMeta(builtinTypes, dummy, t, path[i], Location{});
         dummy.clear();
 
@@ -1885,19 +1903,20 @@ bool ConstraintSolver::tryDispatch(const RefineConstraint& c, NotNull<const Cons
     if (!force && !blockedTypes.empty())
         return block(blockedTypes, constraint);
 
-    const NormalizedType* normType = normalizer->normalize(c.type);
-
-    if (!normType)
-        reportError(NormalizationTooComplex{}, constraint->location);
-
-    if (normType && normType->shouldSuppressErrors())
+    switch (shouldSuppressErrors(normalizer, c.type))
+    {
+    case ErrorSuppression::Suppress:
     {
         auto resultOrError = simplifyUnion(builtinTypes, arena, result, builtinTypes->errorType).result;
         asMutable(c.resultType)->ty.emplace<BoundType>(resultOrError);
+        break;
     }
-    else
-    {
+    case ErrorSuppression::DoNotSuppress:
         asMutable(c.resultType)->ty.emplace<BoundType>(result);
+        break;
+    case ErrorSuppression::NormalizationFailed:
+        reportError(NormalizationTooComplex{}, constraint->location);
+        break;
     }
 
     unblock(c.resultType, constraint->location);
@@ -1983,6 +2002,15 @@ bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const Iterabl
             unify(*anyified, ty, constraint->scope);
     };
 
+    auto unknownify = [&](auto ty) {
+        Anyification anyify{arena, constraint->scope, builtinTypes, &iceReporter, builtinTypes->unknownType, builtinTypes->anyTypePack};
+        std::optional anyified = anyify.substitute(ty);
+        if (!anyified)
+            reportError(CodeTooComplex{}, constraint->location);
+        else
+            unify(*anyified, ty, constraint->scope);
+    };
+
     auto errorify = [&](auto ty) {
         Anyification anyify{arena, constraint->scope, builtinTypes, &iceReporter, errorRecoveryType(), errorRecoveryTypePack()};
         std::optional errorified = anyify.substitute(ty);
@@ -2051,6 +2079,9 @@ bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const Iterabl
 
         Instantiation instantiation(TxnLog::empty(), arena, TypeLevel{}, constraint->scope);
 
+        if (limits.instantiationChildLimit)
+            instantiation.childLimit = *limits.instantiationChildLimit;
+
         if (std::optional<TypeId> instantiatedIterFn = instantiation.substitute(*iterFn))
         {
             if (auto iterFtv = get<FunctionType>(*instantiatedIterFn))
@@ -2107,6 +2138,8 @@ bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const Iterabl
 
         LUAU_ASSERT(false);
     }
+    else if (auto primitiveTy = get<PrimitiveType>(iteratorTy); primitiveTy && primitiveTy->type == PrimitiveType::Type::Table)
+        unknownify(c.variables);
     else
         errorify(c.variables);
 
@@ -2357,7 +2390,7 @@ template<typename TID>
 bool ConstraintSolver::tryUnify(NotNull<const Constraint> constraint, TID subTy, TID superTy)
 {
     Unifier u{normalizer, constraint->scope, constraint->location, Covariant};
-    u.enableScopeTests();
+    u.enableNewSolver();
 
     u.tryUnify(subTy, superTy);
 
@@ -2606,7 +2639,7 @@ bool ConstraintSolver::isBlocked(NotNull<const Constraint> constraint)
 ErrorVec ConstraintSolver::unify(TypeId subType, TypeId superType, NotNull<Scope> scope)
 {
     Unifier u{normalizer, scope, Location{}, Covariant};
-    u.enableScopeTests();
+    u.enableNewSolver();
 
     u.tryUnify(subType, superType);
 
@@ -2631,7 +2664,7 @@ ErrorVec ConstraintSolver::unify(TypePackId subPack, TypePackId superPack, NotNu
 {
     UnifierSharedState sharedState{&iceReporter};
     Unifier u{normalizer, scope, Location{}, Covariant};
-    u.enableScopeTests();
+    u.enableNewSolver();
 
     u.tryUnify(subPack, superPack);
 
@@ -2728,7 +2761,7 @@ TypeId ConstraintSolver::unionOfTypes(TypeId a, TypeId b, NotNull<Scope> scope,
     if (unifyFreeTypes && (get<FreeType>(a) || get<FreeType>(b)))
     {
         Unifier u{normalizer, scope, Location{}, Covariant};
-        u.enableScopeTests();
+        u.enableNewSolver();
         u.tryUnify(b, a);
 
         if (u.errors.empty())
@@ -2785,4 +2818,14 @@ TypePackId ConstraintSolver::anyifyModuleReturnTypePackGenerics(TypePackId tp)
     return arena->addTypePack(resultTypes, resultTail);
 }
 
+LUAU_NOINLINE void ConstraintSolver::throwTimeLimitError()
+{
+    throw TimeLimitError(currentModuleName);
+}
+
+LUAU_NOINLINE void ConstraintSolver::throwUserCancelError()
+{
+    throw UserCancelError(currentModuleName);
+}
+
 } // namespace Luau

Analysis/src/Differ.cpp

@@ -1,11 +1,15 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Differ.h"
+#include "Luau/Common.h"
 #include "Luau/Error.h"
 #include "Luau/ToString.h"
 #include "Luau/Type.h"
 #include "Luau/TypePack.h"
+#include "Luau/Unifiable.h"
 #include <optional>
 #include <string>
+#include <unordered_set>
+#include <vector>
 
 namespace Luau
 {
@@ -34,6 +38,10 @@ std::string DiffPathNode::toString() const
         // Add 1 because Lua is 1-indexed
         return "Ret[" + std::to_string(*index + 1) + "]";
     }
+    case DiffPathNode::Kind::Negation:
+    {
+        return "Negation";
+    }
     default:
     {
         throw InternalCompilerError{"DiffPathNode::toString is not exhaustive"};
@@ -58,22 +66,27 @@ DiffPathNode DiffPathNode::constructWithKind(Kind kind)
 
 DiffPathNodeLeaf DiffPathNodeLeaf::detailsNormal(TypeId ty)
 {
-    return DiffPathNodeLeaf{ty, std::nullopt, std::nullopt, false};
+    return DiffPathNodeLeaf{ty, std::nullopt, std::nullopt, false, std::nullopt};
 }
 
 DiffPathNodeLeaf DiffPathNodeLeaf::detailsTableProperty(TypeId ty, Name tableProperty)
 {
-    return DiffPathNodeLeaf{ty, tableProperty, std::nullopt, false};
+    return DiffPathNodeLeaf{ty, tableProperty, std::nullopt, false, std::nullopt};
+}
+
+DiffPathNodeLeaf DiffPathNodeLeaf::detailsUnionIndex(TypeId ty, size_t index)
+{
+    return DiffPathNodeLeaf{ty, std::nullopt, std::nullopt, false, index};
 }
 
 DiffPathNodeLeaf DiffPathNodeLeaf::detailsLength(int minLength, bool isVariadic)
 {
-    return DiffPathNodeLeaf{std::nullopt, std::nullopt, minLength, isVariadic};
+    return DiffPathNodeLeaf{std::nullopt, std::nullopt, minLength, isVariadic, std::nullopt};
 }
 
 DiffPathNodeLeaf DiffPathNodeLeaf::nullopts()
 {
-    return DiffPathNodeLeaf{std::nullopt, std::nullopt, std::nullopt, false};
+    return DiffPathNodeLeaf{std::nullopt, std::nullopt, std::nullopt, false, std::nullopt};
 }
 
 std::string DiffPath::toString(bool prependDot) const
@@ -104,7 +117,7 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
         checkNonMissingPropertyLeavesHaveNulloptTableProperty();
         return pathStr + " has type " + Luau::toString(*leaf.ty);
     }
-    case DiffError::Kind::MissingProperty:
+    case DiffError::Kind::MissingTableProperty:
     {
         if (leaf.ty.has_value())
         {
@@ -120,6 +133,38 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
         }
         throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
     }
+    case DiffError::Kind::MissingUnionMember:
+    {
+        // TODO: do normal case
+        if (leaf.ty.has_value())
+        {
+            if (!leaf.unionIndex.has_value())
+                throw InternalCompilerError{"leaf.unionIndex is nullopt"};
+            return pathStr + " is a union containing type " + Luau::toString(*leaf.ty);
+        }
+        else if (otherLeaf.ty.has_value())
+        {
+            return pathStr + " is a union missing type " + Luau::toString(*otherLeaf.ty);
+        }
+        throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
+    }
+    case DiffError::Kind::MissingIntersectionMember:
+    {
+        // TODO: better message for intersections
+        // An intersection of just functions is always an "overloaded function"
+        // An intersection of just tables is always a "joined table"
+        if (leaf.ty.has_value())
+        {
+            if (!leaf.unionIndex.has_value())
+                throw InternalCompilerError{"leaf.unionIndex is nullopt"};
+            return pathStr + " is an intersection containing type " + Luau::toString(*leaf.ty);
+        }
+        else if (otherLeaf.ty.has_value())
+        {
+            return pathStr + " is an intersection missing type " + Luau::toString(*otherLeaf.ty);
+        }
+        throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
+    }
     case DiffError::Kind::LengthMismatchInFnArgs:
     {
         if (!leaf.minLength.has_value())
@@ -163,9 +208,20 @@ std::string getDevFixFriendlyName(TypeId ty)
 
 std::string DiffError::toString() const
 {
-    std::string msg = "DiffError: these two types are not equal because the left type at " + toStringALeaf(leftRootName, left, right) +
-                      ", while the right type at " + toStringALeaf(rightRootName, right, left);
-    return msg;
+    switch (kind)
+    {
+    case DiffError::Kind::IncompatibleGeneric:
+    {
+        std::string diffPathStr{diffPath.toString(true)};
+        return "DiffError: these two types are not equal because the left generic at " + leftRootName + diffPathStr +
+               " cannot be the same type parameter as the right generic at " + rightRootName + diffPathStr;
+    }
+    default:
+    {
+        return "DiffError: these two types are not equal because the left type at " + toStringALeaf(leftRootName, left, right) +
+               ", while the right type at " + toStringALeaf(rightRootName, right, left);
+    }
+    }
 }
 
 void DiffError::checkValidInitialization(const DiffPathNodeLeaf& left, const DiffPathNodeLeaf& right)
@@ -193,6 +249,19 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
 static DifferResult diffPrimitive(DifferEnvironment& env, TypeId left, TypeId right);
 static DifferResult diffSingleton(DifferEnvironment& env, TypeId left, TypeId right);
 static DifferResult diffFunction(DifferEnvironment& env, TypeId left, TypeId right);
+static DifferResult diffGeneric(DifferEnvironment& env, TypeId left, TypeId right);
+static DifferResult diffNegation(DifferEnvironment& env, TypeId left, TypeId right);
+struct FindSeteqCounterexampleResult
+{
+    // nullopt if no counterexample found
+    std::optional<size_t> mismatchIdx;
+    // true if counterexample is in the left, false if cex is in the right
+    bool inLeft;
+};
+static FindSeteqCounterexampleResult findSeteqCounterexample(
+    DifferEnvironment& env, const std::vector<TypeId>& left, const std::vector<TypeId>& right);
+static DifferResult diffUnion(DifferEnvironment& env, TypeId left, TypeId right);
+static DifferResult diffIntersection(DifferEnvironment& env, TypeId left, TypeId right);
 /**
  * The last argument gives context info on which complex type contained the TypePack.
  */
@@ -205,6 +274,8 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
 {
     const TableType* leftTable = get<TableType>(left);
     const TableType* rightTable = get<TableType>(right);
+    LUAU_ASSERT(leftTable);
+    LUAU_ASSERT(rightTable);
 
     for (auto const& [field, value] : leftTable->props)
     {
@@ -212,7 +283,7 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
         {
             // left has a field the right doesn't
             return DifferResult{DiffError{
-                DiffError::Kind::MissingProperty,
+                DiffError::Kind::MissingTableProperty,
                 DiffPathNodeLeaf::detailsTableProperty(value.type(), field),
                 DiffPathNodeLeaf::nullopts(),
                 getDevFixFriendlyName(env.rootLeft),
@@ -225,9 +296,9 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
         if (leftTable->props.find(field) == leftTable->props.end())
         {
             // right has a field the left doesn't
-            return DifferResult{
-                DiffError{DiffError::Kind::MissingProperty, DiffPathNodeLeaf::nullopts(), DiffPathNodeLeaf::detailsTableProperty(value.type(), field),
-                    getDevFixFriendlyName(env.rootLeft), getDevFixFriendlyName(env.rootRight)}};
+            return DifferResult{DiffError{DiffError::Kind::MissingTableProperty, DiffPathNodeLeaf::nullopts(),
+                DiffPathNodeLeaf::detailsTableProperty(value.type(), field), getDevFixFriendlyName(env.rootLeft),
+                getDevFixFriendlyName(env.rootRight)}};
         }
     }
     // left and right have the same set of keys
@@ -248,6 +319,8 @@ static DifferResult diffPrimitive(DifferEnvironment& env, TypeId left, TypeId ri
 {
     const PrimitiveType* leftPrimitive = get<PrimitiveType>(left);
     const PrimitiveType* rightPrimitive = get<PrimitiveType>(right);
+    LUAU_ASSERT(leftPrimitive);
+    LUAU_ASSERT(rightPrimitive);
 
     if (leftPrimitive->type != rightPrimitive->type)
     {
@@ -266,6 +339,8 @@ static DifferResult diffSingleton(DifferEnvironment& env, TypeId left, TypeId ri
 {
     const SingletonType* leftSingleton = get<SingletonType>(left);
     const SingletonType* rightSingleton = get<SingletonType>(right);
+    LUAU_ASSERT(leftSingleton);
+    LUAU_ASSERT(rightSingleton);
 
     if (*leftSingleton != *rightSingleton)
     {
@@ -284,6 +359,8 @@ static DifferResult diffFunction(DifferEnvironment& env, TypeId left, TypeId rig
 {
     const FunctionType* leftFunction = get<FunctionType>(left);
     const FunctionType* rightFunction = get<FunctionType>(right);
+    LUAU_ASSERT(leftFunction);
+    LUAU_ASSERT(rightFunction);
 
     DifferResult differResult = diffTpi(env, DiffError::Kind::LengthMismatchInFnArgs, leftFunction->argTypes, rightFunction->argTypes);
     if (differResult.diffError.has_value())
@@ -291,6 +368,157 @@ static DifferResult diffFunction(DifferEnvironment& env, TypeId left, TypeId rig
     return diffTpi(env, DiffError::Kind::LengthMismatchInFnRets, leftFunction->retTypes, rightFunction->retTypes);
 }
 
+static DifferResult diffGeneric(DifferEnvironment& env, TypeId left, TypeId right)
+{
+    LUAU_ASSERT(get<GenericType>(left));
+    LUAU_ASSERT(get<GenericType>(right));
+    // Try to pair up the generics
+    bool isLeftFree = !env.genericMatchedPairs.contains(left);
+    bool isRightFree = !env.genericMatchedPairs.contains(right);
+    if (isLeftFree && isRightFree)
+    {
+        env.genericMatchedPairs[left] = right;
+        env.genericMatchedPairs[right] = left;
+        return DifferResult{};
+    }
+    else if (isLeftFree || isRightFree)
+    {
+        return DifferResult{DiffError{
+            DiffError::Kind::IncompatibleGeneric,
+            DiffPathNodeLeaf::nullopts(),
+            DiffPathNodeLeaf::nullopts(),
+            getDevFixFriendlyName(env.rootLeft),
+            getDevFixFriendlyName(env.rootRight),
+        }};
+    }
+
+    // Both generics are already paired up
+    if (*env.genericMatchedPairs.find(left) == right)
+        return DifferResult{};
+
+    return DifferResult{DiffError{
+        DiffError::Kind::IncompatibleGeneric,
+        DiffPathNodeLeaf::nullopts(),
+        DiffPathNodeLeaf::nullopts(),
+        getDevFixFriendlyName(env.rootLeft),
+        getDevFixFriendlyName(env.rootRight),
+    }};
+}
+
+static DifferResult diffNegation(DifferEnvironment& env, TypeId left, TypeId right)
+{
+    const NegationType* leftNegation = get<NegationType>(left);
+    const NegationType* rightNegation = get<NegationType>(right);
+    LUAU_ASSERT(leftNegation);
+    LUAU_ASSERT(rightNegation);
+
+    DifferResult differResult = diffUsingEnv(env, leftNegation->ty, rightNegation->ty);
+    if (!differResult.diffError.has_value())
+        return DifferResult{};
+
+    differResult.wrapDiffPath(DiffPathNode::constructWithKind(DiffPathNode::Kind::Negation));
+    return differResult;
+}
+
+static FindSeteqCounterexampleResult findSeteqCounterexample(
+    DifferEnvironment& env, const std::vector<TypeId>& left, const std::vector<TypeId>& right)
+{
+    std::unordered_set<size_t> unmatchedRightIdxes;
+    for (size_t i = 0; i < right.size(); i++)
+        unmatchedRightIdxes.insert(i);
+    for (size_t leftIdx = 0; leftIdx < left.size(); leftIdx++)
+    {
+        bool leftIdxIsMatched = false;
+        auto unmatchedRightIdxIt = unmatchedRightIdxes.begin();
+        while (unmatchedRightIdxIt != unmatchedRightIdxes.end())
+        {
+            DifferResult differResult = diffUsingEnv(env, left[leftIdx], right[*unmatchedRightIdxIt]);
+            if (differResult.diffError.has_value())
+            {
+                unmatchedRightIdxIt++;
+                continue;
+            }
+
+            // unmatchedRightIdxIt is matched with current leftIdx
+            leftIdxIsMatched = true;
+            unmatchedRightIdxIt = unmatchedRightIdxes.erase(unmatchedRightIdxIt);
+        }
+        if (!leftIdxIsMatched)
+        {
+            return FindSeteqCounterexampleResult{leftIdx, true};
+        }
+    }
+    if (unmatchedRightIdxes.empty())
+        return FindSeteqCounterexampleResult{std::nullopt, false};
+    return FindSeteqCounterexampleResult{*unmatchedRightIdxes.begin(), false};
+}
+
+static DifferResult diffUnion(DifferEnvironment& env, TypeId left, TypeId right)
+{
+    const UnionType* leftUnion = get<UnionType>(left);
+    const UnionType* rightUnion = get<UnionType>(right);
+    LUAU_ASSERT(leftUnion);
+    LUAU_ASSERT(rightUnion);
+
+    FindSeteqCounterexampleResult findSeteqCexResult = findSeteqCounterexample(env, leftUnion->options, rightUnion->options);
+    if (findSeteqCexResult.mismatchIdx.has_value())
+    {
+        if (findSeteqCexResult.inLeft)
+            return DifferResult{DiffError{
+                DiffError::Kind::MissingUnionMember,
+                DiffPathNodeLeaf::detailsUnionIndex(leftUnion->options[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
+                DiffPathNodeLeaf::nullopts(),
+                getDevFixFriendlyName(env.rootLeft),
+                getDevFixFriendlyName(env.rootRight),
+            }};
+        else
+            return DifferResult{DiffError{
+                DiffError::Kind::MissingUnionMember,
+                DiffPathNodeLeaf::nullopts(),
+                DiffPathNodeLeaf::detailsUnionIndex(rightUnion->options[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
+                getDevFixFriendlyName(env.rootLeft),
+                getDevFixFriendlyName(env.rootRight),
+            }};
+    }
+
+    // TODO: somehow detect mismatch index, likely using heuristics
+
+    return DifferResult{};
+}
+
+static DifferResult diffIntersection(DifferEnvironment& env, TypeId left, TypeId right)
+{
+    const IntersectionType* leftIntersection = get<IntersectionType>(left);
+    const IntersectionType* rightIntersection = get<IntersectionType>(right);
+    LUAU_ASSERT(leftIntersection);
+    LUAU_ASSERT(rightIntersection);
+
+    FindSeteqCounterexampleResult findSeteqCexResult = findSeteqCounterexample(env, leftIntersection->parts, rightIntersection->parts);
+    if (findSeteqCexResult.mismatchIdx.has_value())
+    {
+        if (findSeteqCexResult.inLeft)
+            return DifferResult{DiffError{
+                DiffError::Kind::MissingIntersectionMember,
+                DiffPathNodeLeaf::detailsUnionIndex(leftIntersection->parts[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
+                DiffPathNodeLeaf::nullopts(),
+                getDevFixFriendlyName(env.rootLeft),
+                getDevFixFriendlyName(env.rootRight),
+            }};
+        else
+            return DifferResult{DiffError{
+                DiffError::Kind::MissingIntersectionMember,
+                DiffPathNodeLeaf::nullopts(),
+                DiffPathNodeLeaf::detailsUnionIndex(rightIntersection->parts[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
+                getDevFixFriendlyName(env.rootLeft),
+                getDevFixFriendlyName(env.rootRight),
+            }};
+    }
+
+    // TODO: somehow detect mismatch index, likely using heuristics
+
+    return DifferResult{};
+}
+
 static DifferResult diffUsingEnv(DifferEnvironment& env, TypeId left, TypeId right)
 {
     left = follow(left);
@@ -322,6 +550,10 @@ static DifferResult diffUsingEnv(DifferEnvironment& env, TypeId left, TypeId rig
             // Both left and right must be Any if either is Any for them to be equal!
             return DifferResult{};
         }
+        else if (auto ln = get<NegationType>(left))
+        {
+            return diffNegation(env, left, right);
+        }
 
         throw InternalCompilerError{"Unimplemented Simple TypeId variant for diffing"};
     }
@@ -336,6 +568,24 @@ static DifferResult diffUsingEnv(DifferEnvironment& env, TypeId left, TypeId rig
     {
         return diffFunction(env, left, right);
     }
+    if (auto lg = get<GenericType>(left))
+    {
+        return diffGeneric(env, left, right);
+    }
+    if (auto lu = get<UnionType>(left))
+    {
+        return diffUnion(env, left, right);
+    }
+    if (auto li = get<IntersectionType>(left))
+    {
+        return diffIntersection(env, left, right);
+    }
+    if (auto le = get<Luau::Unifiable::Error>(left))
+    {
+        // TODO: return debug-friendly result state
+        return DifferResult{};
+    }
+
     throw InternalCompilerError{"Unimplemented non-simple TypeId variant for diffing"};
 }
 
@@ -444,7 +694,7 @@ static DifferResult diffHandleFlattenedTail(DifferEnvironment& env, DiffError::K
 
 DifferResult diff(TypeId ty1, TypeId ty2)
 {
-    DifferEnvironment differEnv{ty1, ty2};
+    DifferEnvironment differEnv{ty1, ty2, DenseHashMap<TypeId, TypeId>{nullptr}};
     return diffUsingEnv(differEnv, ty1, ty2);
 }
 
@@ -452,7 +702,7 @@ bool isSimple(TypeId ty)
 {
     ty = follow(ty);
     // TODO: think about GenericType, etc.
-    return get<PrimitiveType>(ty) || get<SingletonType>(ty) || get<AnyType>(ty);
+    return get<PrimitiveType>(ty) || get<SingletonType>(ty) || get<AnyType>(ty) || get<NegationType>(ty);
 }
 
 } // namespace Luau

Analysis/src/Frontend.cpp

@@ -1141,22 +1141,26 @@ const SourceModule* Frontend::getSourceModule(const ModuleName& moduleName) cons
 
 ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle>& requireCycles, NotNull<BuiltinTypes> builtinTypes,
     NotNull<InternalErrorReporter> iceHandler, NotNull<ModuleResolver> moduleResolver, NotNull<FileResolver> fileResolver,
-    const ScopePtr& parentScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options)
+    const ScopePtr& parentScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options,
+    TypeCheckLimits limits)
 {
     const bool recordJsonLog = FFlag::DebugLuauLogSolverToJson;
     return check(sourceModule, requireCycles, builtinTypes, iceHandler, moduleResolver, fileResolver, parentScope, std::move(prepareModuleScope),
-        options, recordJsonLog);
+        options, limits, recordJsonLog);
 }
 
 ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle>& requireCycles, NotNull<BuiltinTypes> builtinTypes,
     NotNull<InternalErrorReporter> iceHandler, NotNull<ModuleResolver> moduleResolver, NotNull<FileResolver> fileResolver,
     const ScopePtr& parentScope, std::function<void(const ModuleName&, const ScopePtr&)> prepareModuleScope, FrontendOptions options,
-    bool recordJsonLog)
+    TypeCheckLimits limits, bool recordJsonLog)
 {
     ModulePtr result = std::make_shared<Module>();
     result->name = sourceModule.name;
     result->humanReadableName = sourceModule.humanReadableName;
 
+    result->internalTypes.owningModule = result.get();
+    result->interfaceTypes.owningModule = result.get();
+
     iceHandler->moduleName = sourceModule.name;
 
     std::unique_ptr<DcrLogger> logger;
@@ -1174,32 +1178,34 @@ ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle
 
     UnifierSharedState unifierState{iceHandler};
     unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
-    unifierState.counters.iterationLimit = FInt::LuauTypeInferIterationLimit;
+    unifierState.counters.iterationLimit = limits.unifierIterationLimit.value_or(FInt::LuauTypeInferIterationLimit);
 
     Normalizer normalizer{&result->internalTypes, builtinTypes, NotNull{&unifierState}};
 
-    ConstraintGraphBuilder cgb{
-        result,
-        &result->internalTypes,
-        moduleResolver,
-        builtinTypes,
-        iceHandler,
-        parentScope,
-        std::move(prepareModuleScope),
-        logger.get(),
-        NotNull{&dfg},
-    };
+    ConstraintGraphBuilder cgb{result, &result->internalTypes, moduleResolver, builtinTypes, iceHandler, parentScope, std::move(prepareModuleScope),
+        logger.get(), NotNull{&dfg}, requireCycles};
 
     cgb.visit(sourceModule.root);
     result->errors = std::move(cgb.errors);
 
-    ConstraintSolver cs{
-        NotNull{&normalizer}, NotNull(cgb.rootScope), borrowConstraints(cgb.constraints), result->name, moduleResolver, requireCycles, logger.get()};
+    ConstraintSolver cs{NotNull{&normalizer}, NotNull(cgb.rootScope), borrowConstraints(cgb.constraints), result->humanReadableName, moduleResolver,
+        requireCycles, logger.get(), limits};
 
     if (options.randomizeConstraintResolutionSeed)
         cs.randomize(*options.randomizeConstraintResolutionSeed);
 
-    cs.run();
+    try
+    {
+        cs.run();
+    }
+    catch (const TimeLimitError&)
+    {
+        result->timeout = true;
+    }
+    catch (const UserCancelError&)
+    {
+        result->cancelled = true;
+    }
 
     for (TypeError& e : cs.errors)
         result->errors.emplace_back(std::move(e));
@@ -1209,7 +1215,22 @@ ModulePtr check(const SourceModule& sourceModule, const std::vector<RequireCycle
 
     result->clonePublicInterface(builtinTypes, *iceHandler);
 
-    Luau::check(builtinTypes, NotNull{&unifierState}, logger.get(), sourceModule, result.get());
+    if (result->timeout || result->cancelled)
+    {
+        // If solver was interrupted, skip typechecking and replace all module results with error-supressing types to avoid leaking blocked/pending types
+        ScopePtr moduleScope = result->getModuleScope();
+        moduleScope->returnType = builtinTypes->errorRecoveryTypePack();
+
+        for (auto& [name, ty] : result->declaredGlobals)
+            ty = builtinTypes->errorRecoveryType();
+
+        for (auto& [name, tf] : result->exportedTypeBindings)
+            tf.type = builtinTypes->errorRecoveryType();
+    }
+    else
+    {
+        Luau::check(builtinTypes, NotNull{&unifierState}, logger.get(), sourceModule, result.get());
+    }
 
     // It would be nice if we could freeze the arenas before doing type
     // checking, but we'll have to do some work to get there.
@@ -1248,7 +1269,7 @@ ModulePtr Frontend::check(const SourceModule& sourceModule, Mode mode, std::vect
         {
             return Luau::check(sourceModule, requireCycles, builtinTypes, NotNull{&iceHandler},
                 NotNull{forAutocomplete ? &moduleResolverForAutocomplete : &moduleResolver}, NotNull{fileResolver},
-                environmentScope ? *environmentScope : globals.globalScope, prepareModuleScopeWrap, options, recordJsonLog);
+                environmentScope ? *environmentScope : globals.globalScope, prepareModuleScopeWrap, options, typeCheckLimits, recordJsonLog);
         }
         catch (const InternalCompilerError& err)
         {

Analysis/src/Linter.cpp

@@ -14,6 +14,8 @@
 
 LUAU_FASTINTVARIABLE(LuauSuggestionDistance, 4)
 
+LUAU_FASTFLAGVARIABLE(LuauLintNativeComment, false)
+
 namespace Luau
 {
 
@@ -2825,6 +2827,12 @@ static void lintComments(LintContext& context, const std::vector<HotComment>& ho
                             "optimize directive uses unknown optimization level '%s', 0..2 expected", level);
                 }
             }
+            else if (FFlag::LuauLintNativeComment && first == "native")
+            {
+                if (space != std::string::npos)
+                    emitWarning(context, LintWarning::Code_CommentDirective, hc.location,
+                        "native directive has extra symbols at the end of the line");
+            }
             else
             {
                 static const char* kHotComments[] = {
@@ -2833,6 +2841,7 @@ static void lintComments(LintContext& context, const std::vector<HotComment>& ho
                     "nonstrict",
                     "strict",
                     "optimize",
+                    "native",
                 };
 
                 if (const char* suggestion = fuzzyMatch(first, kHotComments, std::size(kHotComments)))

Analysis/src/Normalize.cpp

@@ -19,7 +19,6 @@ LUAU_FASTINTVARIABLE(LuauNormalizeIterationLimit, 1200);
 LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeBlockedTypes, false);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeCyclicUnions, false);
-LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTFLAG(LuauTransitiveSubtyping)
 LUAU_FASTFLAG(DebugLuauReadWriteProperties)
 
@@ -253,6 +252,14 @@ bool NormalizedType::shouldSuppressErrors() const
     return hasErrors() || get<AnyType>(tops);
 }
 
+bool NormalizedType::hasTopTable() const
+{
+    return hasTables() && std::any_of(tables.begin(), tables.end(), [&](TypeId ty) {
+        auto primTy = get<PrimitiveType>(ty);
+        return primTy && primTy->type == PrimitiveType::Type::Table;
+    });
+}
+
 bool NormalizedType::hasTops() const
 {
     return !get<NeverType>(tops);

Analysis/src/Quantify.cpp

@@ -9,7 +9,6 @@
 #include "Luau/VisitType.h"
 
 LUAU_FASTFLAG(DebugLuauSharedSelf)
-LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 
 namespace Luau
 {

Analysis/src/Scope.cpp

@@ -2,6 +2,8 @@
 
 #include "Luau/Scope.h"
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 namespace Luau
 {
 
@@ -160,14 +162,12 @@ void Scope::inheritRefinements(const ScopePtr& childScope)
                 dcrRefinements[k] = a;
         }
     }
-    else
+
+    for (const auto& [k, a] : childScope->refinements)
     {
-        for (const auto& [k, a] : childScope->refinements)
-        {
-            Symbol symbol = getBaseSymbol(k);
-            if (lookup(symbol))
-                refinements[k] = a;
-        }
+        Symbol symbol = getBaseSymbol(k);
+        if (lookup(symbol))
+            refinements[k] = a;
     }
 }
 

Analysis/src/Simplify.cpp

@@ -364,7 +364,13 @@ Relation relate(TypeId left, TypeId right)
     if (auto ut = get<UnionType>(left))
         return Relation::Intersects;
     else if (auto ut = get<UnionType>(right))
+    {
+        std::vector<Relation> opts;
+        for (TypeId part : ut)
+            if (relate(left, part) == Relation::Subset)
+                return Relation::Subset;
         return Relation::Intersects;
+    }
 
     if (auto rnt = get<NegationType>(right))
     {

Analysis/src/Symbol.cpp

@@ -3,9 +3,23 @@
 
 #include "Luau/Common.h"
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+
 namespace Luau
 {
 
+bool Symbol::operator==(const Symbol& rhs) const
+{
+    if (local)
+        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::DebugLuauDeferredConstraintResolution)
+        return !rhs.local && !rhs.global.value; // Reflexivity: we already know `this` Symbol is empty, so check that rhs is.
+    else
+        return false;
+}
+
 std::string toString(const Symbol& name)
 {
     if (name.local)

Analysis/src/TxnLog.cpp

@@ -9,8 +9,6 @@
 #include <algorithm>
 #include <stdexcept>
 
-LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
-
 namespace Luau
 {
 

Analysis/src/TypeChecker2.cpp

@@ -283,7 +283,8 @@ struct TypeChecker2
         if (errors.empty())
             noTypeFamilyErrors.insert(instance);
 
-        reportErrors(std::move(errors));
+        if (!isErrorSuppressing(location, instance))
+            reportErrors(std::move(errors));
         return instance;
     }
 
@@ -488,7 +489,7 @@ struct TypeChecker2
         u.hideousFixMeGenericsAreActuallyFree = true;
 
         u.tryUnify(actualRetType, expectedRetType);
-        const bool ok = u.errors.empty() && u.log.empty();
+        const bool ok = (u.errors.empty() && u.log.empty()) || isErrorSuppressing(ret->location, actualRetType, ret->location, expectedRetType);
 
         if (!ok)
         {
@@ -526,9 +527,7 @@ struct TypeChecker2
                     TypeId valueType = value ? lookupType(value) : nullptr;
                     if (valueType)
                     {
-                        ErrorVec errors = tryUnify(stack.back(), value->location, valueType, annotationType);
-                        if (!errors.empty())
-                            reportErrors(std::move(errors));
+                        reportErrors(tryUnify(stack.back(), value->location, valueType, annotationType));
                     }
 
                     visit(var->annotation);
@@ -554,9 +553,7 @@ struct TypeChecker2
                     if (var->annotation)
                     {
                         TypeId varType = lookupAnnotation(var->annotation);
-                        ErrorVec errors = tryUnify(stack.back(), value->location, valueTypes.head[j - i], varType);
-                        if (!errors.empty())
-                            reportErrors(std::move(errors));
+                        reportErrors(tryUnify(stack.back(), value->location, valueTypes.head[j - i], varType));
 
                         visit(var->annotation);
                     }
@@ -764,6 +761,11 @@ struct TypeChecker2
             }
         };
 
+        const NormalizedType* iteratorNorm = normalizer.normalize(iteratorTy);
+
+        if (!iteratorNorm)
+            reportError(NormalizationTooComplex{}, firstValue->location);
+
         /*
          * If the first iterator argument is a function
          *  * There must be 1 to 3 iterator arguments.  Name them (nextTy,
@@ -798,7 +800,7 @@ struct TypeChecker2
         {
             // nothing
         }
-        else if (isOptional(iteratorTy))
+        else if (isOptional(iteratorTy) && !(iteratorNorm && iteratorNorm->shouldSuppressErrors()))
         {
             reportError(OptionalValueAccess{iteratorTy}, forInStatement->values.data[0]->location);
         }
@@ -833,7 +835,7 @@ struct TypeChecker2
                         {
                             checkFunction(nextFtv, instantiatedIteratorTypes, true);
                         }
-                        else
+                        else if (!isErrorSuppressing(forInStatement->values.data[0]->location, *instantiatedNextFn))
                         {
                             reportError(CannotCallNonFunction{*instantiatedNextFn}, forInStatement->values.data[0]->location);
                         }
@@ -843,7 +845,7 @@ struct TypeChecker2
                         reportError(UnificationTooComplex{}, forInStatement->values.data[0]->location);
                     }
                 }
-                else
+                else if (!isErrorSuppressing(forInStatement->values.data[0]->location, *iterMmTy))
                 {
                     // TODO: This will not tell the user that this is because the
                     // metamethod isn't callable. This is not ideal, and we should
@@ -859,7 +861,11 @@ struct TypeChecker2
                 reportError(UnificationTooComplex{}, forInStatement->values.data[0]->location);
             }
         }
-        else
+        else if (iteratorNorm && iteratorNorm->hasTopTable())
+        {
+            // nothing
+        }
+        else if (!iteratorNorm || !iteratorNorm->shouldSuppressErrors())
         {
             reportError(CannotCallNonFunction{iteratorTy}, forInStatement->values.data[0]->location);
         }
@@ -882,7 +888,9 @@ struct TypeChecker2
             if (get<NeverType>(lhsType))
                 continue;
 
-            if (!isSubtype(rhsType, lhsType, stack.back()))
+
+            if (!isSubtype(rhsType, lhsType, stack.back()) &&
+                !isErrorSuppressing(assign->vars.data[i]->location, lhsType, assign->values.data[i]->location, rhsType))
             {
                 reportError(TypeMismatch{lhsType, rhsType}, rhs->location);
             }
@@ -1064,8 +1072,8 @@ struct TypeChecker2
     void visitCall(AstExprCall* call)
     {
         TypePack args;
-        std::vector<Location> argLocs;
-        argLocs.reserve(call->args.size + 1);
+        std::vector<AstExpr*> argExprs;
+        argExprs.reserve(call->args.size + 1);
 
         TypeId* originalCallTy = module->astOriginalCallTypes.find(call);
         TypeId* selectedOverloadTy = module->astOverloadResolvedTypes.find(call);
@@ -1088,18 +1096,18 @@ struct TypeChecker2
                 ice->ice("method call expression has no 'self'");
 
             args.head.push_back(lookupType(indexExpr->expr));
-            argLocs.push_back(indexExpr->expr->location);
+            argExprs.push_back(indexExpr->expr);
         }
         else if (findMetatableEntry(builtinTypes, module->errors, *originalCallTy, "__call", call->func->location))
         {
             args.head.insert(args.head.begin(), lookupType(call->func));
-            argLocs.push_back(call->func->location);
+            argExprs.push_back(call->func);
         }
 
         for (size_t i = 0; i < call->args.size; ++i)
         {
             AstExpr* arg = call->args.data[i];
-            argLocs.push_back(arg->location);
+            argExprs.push_back(arg);
             TypeId* argTy = module->astTypes.find(arg);
             if (argTy)
                 args.head.push_back(*argTy);
@@ -1127,20 +1135,20 @@ struct TypeChecker2
             call->location,
         };
 
-        resolver.resolve(fnTy, &args, call->func->location, &argLocs);
+        resolver.resolve(fnTy, &args, call->func, &argExprs);
+        auto norm = normalizer.normalize(fnTy);
+        if (!norm)
+            reportError(NormalizationTooComplex{}, call->func->location);
 
-        if (!resolver.ok.empty())
+        if (norm && norm->shouldSuppressErrors())
+            return; // error suppressing function type!
+        else if (!resolver.ok.empty())
             return; // We found a call that works, so this is ok.
-        else if (auto norm = normalizer.normalize(fnTy); !norm || !normalizer.isInhabited(norm))
-        {
-            if (!norm)
-                reportError(NormalizationTooComplex{}, call->func->location);
-            else
-                return; // Ok. Calling an uninhabited type is no-op.
-        }
+        else if (!norm || !normalizer.isInhabited(norm))
+            return; // Ok. Calling an uninhabited type is no-op.
         else if (!resolver.nonviableOverloads.empty())
         {
-            if (resolver.nonviableOverloads.size() == 1)
+            if (resolver.nonviableOverloads.size() == 1 && !isErrorSuppressing(call->func->location, resolver.nonviableOverloads.front().first))
                 reportErrors(resolver.nonviableOverloads.front().second);
             else
             {
@@ -1224,13 +1232,26 @@ struct TypeChecker2
         InsertionOrderedMap<TypeId, std::pair<Analysis, size_t>> resolution;
 
     private:
-        template<typename Ty>
-        std::optional<ErrorVec> tryUnify(const Location& location, Ty subTy, Ty superTy)
+        std::optional<ErrorVec> tryUnify(const Location& location, TypeId subTy, TypeId superTy, const LiteralProperties* literalProperties = nullptr)
         {
             Unifier u{normalizer, scope, location, Covariant};
             u.ctx = CountMismatch::Arg;
             u.hideousFixMeGenericsAreActuallyFree = true;
-            u.enableScopeTests();
+            u.enableNewSolver();
+            u.tryUnify(subTy, superTy, /*isFunctionCall*/ false, /*isIntersection*/ false, literalProperties);
+
+            if (u.errors.empty())
+                return std::nullopt;
+
+            return std::move(u.errors);
+        }
+
+        std::optional<ErrorVec> tryUnify(const Location& location, TypePackId subTy, TypePackId superTy)
+        {
+            Unifier u{normalizer, scope, location, Covariant};
+            u.ctx = CountMismatch::Arg;
+            u.hideousFixMeGenericsAreActuallyFree = true;
+            u.enableNewSolver();
             u.tryUnify(subTy, superTy);
 
             if (u.errors.empty())
@@ -1240,7 +1261,7 @@ struct TypeChecker2
         }
 
         std::pair<Analysis, ErrorVec> checkOverload(
-            TypeId fnTy, const TypePack* args, Location fnLoc, const std::vector<Location>* argLocs, bool callMetamethodOk = true)
+            TypeId fnTy, const TypePack* args, AstExpr* fnLoc, const std::vector<AstExpr*>* argExprs, bool callMetamethodOk = true)
         {
             fnTy = follow(fnTy);
 
@@ -1248,25 +1269,64 @@ struct TypeChecker2
             if (get<AnyType>(fnTy) || get<ErrorType>(fnTy) || get<NeverType>(fnTy))
                 return {Ok, {}};
             else if (auto fn = get<FunctionType>(fnTy))
-                return checkOverload_(fnTy, fn, args, fnLoc, argLocs); // Intentionally split to reduce the stack pressure of this function.
+                return checkOverload_(fnTy, fn, args, fnLoc, argExprs); // Intentionally split to reduce the stack pressure of this function.
             else if (auto callMm = findMetatableEntry(builtinTypes, discard, fnTy, "__call", callLoc); callMm && callMetamethodOk)
             {
                 // Calling a metamethod forwards the `fnTy` as self.
                 TypePack withSelf = *args;
                 withSelf.head.insert(withSelf.head.begin(), fnTy);
 
-                std::vector<Location> withSelfLocs = *argLocs;
-                withSelfLocs.insert(withSelfLocs.begin(), fnLoc);
+                std::vector<AstExpr*> withSelfExprs = *argExprs;
+                withSelfExprs.insert(withSelfExprs.begin(), fnLoc);
 
-                return checkOverload(*callMm, &withSelf, fnLoc, &withSelfLocs, /*callMetamethodOk=*/false);
+                return checkOverload(*callMm, &withSelf, fnLoc, &withSelfExprs, /*callMetamethodOk=*/false);
             }
             else
                 return {TypeIsNotAFunction, {}}; // Intentionally empty. We can just fabricate the type error later on.
         }
 
+        static bool isLiteral(AstExpr* expr)
+        {
+            if (auto group = expr->as<AstExprGroup>())
+                return isLiteral(group->expr);
+            else if (auto assertion = expr->as<AstExprTypeAssertion>())
+                return isLiteral(assertion->expr);
+
+            return
+                expr->is<AstExprConstantNil>() ||
+                expr->is<AstExprConstantBool>() ||
+                expr->is<AstExprConstantNumber>() ||
+                expr->is<AstExprConstantString>() ||
+                expr->is<AstExprFunction>() ||
+                expr->is<AstExprTable>();
+        }
+
+        static std::unique_ptr<LiteralProperties> buildLiteralPropertiesSet(AstExpr* expr)
+        {
+            const AstExprTable* table = expr->as<AstExprTable>();
+            if (!table)
+                return nullptr;
+
+            std::unique_ptr<LiteralProperties> result = std::make_unique<LiteralProperties>(Name{});
+
+            for (const AstExprTable::Item& item : table->items)
+            {
+                if (item.kind != AstExprTable::Item::Record)
+                    continue;
+
+                AstExprConstantString* keyExpr = item.key->as<AstExprConstantString>();
+                LUAU_ASSERT(keyExpr);
+
+                if (isLiteral(item.value))
+                    result->insert(Name{keyExpr->value.begin(), keyExpr->value.end()});
+            }
+
+            return result;
+        }
+
         LUAU_NOINLINE
         std::pair<Analysis, ErrorVec> checkOverload_(
-            TypeId fnTy, const FunctionType* fn, const TypePack* args, Location fnLoc, const std::vector<Location>* argLocs)
+            TypeId fnTy, const FunctionType* fn, const TypePack* args, AstExpr* fnExpr, const std::vector<AstExpr*>* argExprs)
         {
             TxnLog fake;
             FamilyGraphReductionResult result = reduceFamilies(fnTy, callLoc, arena, builtinTypes, scope, normalizer, &fake, /*force=*/true);
@@ -1286,9 +1346,11 @@ struct TypeChecker2
 
                 TypeId paramTy = *paramIter;
                 TypeId argTy = args->head[argOffset];
-                Location argLoc = argLocs->at(argOffset >= argLocs->size() ? argLocs->size() - 1 : argOffset);
+                AstExpr* argLoc = argExprs->at(argOffset >= argExprs->size() ? argExprs->size() - 1 : argOffset);
 
-                if (auto errors = tryUnify(argLoc, argTy, paramTy))
+                std::unique_ptr<LiteralProperties> literalProperties{buildLiteralPropertiesSet(argLoc)};
+
+                if (auto errors = tryUnify(argLoc->location, argTy, paramTy, literalProperties.get()))
                 {
                     // Since we're stopping right here, we need to decide if this is a nonviable overload or if there is an arity mismatch.
                     // If it's a nonviable overload, then we need to keep going to get all type errors.
@@ -1308,19 +1370,21 @@ struct TypeChecker2
                 // If we can iterate over the head of arguments, then we have exhausted the head of the parameters.
                 LUAU_ASSERT(paramIter == end(fn->argTypes));
 
-                Location argLoc = argLocs->at(argOffset >= argLocs->size() ? argLocs->size() - 1 : argOffset);
+                AstExpr* argExpr = argExprs->at(argOffset >= argExprs->size() ? argExprs->size() - 1 : argOffset);
 
                 if (!paramIter.tail())
                 {
                     auto [minParams, optMaxParams] = getParameterExtents(TxnLog::empty(), fn->argTypes);
-                    TypeError error{argLoc, CountMismatch{minParams, optMaxParams, args->head.size(), CountMismatch::Arg, false}};
+                    TypeError error{argExpr->location, CountMismatch{minParams, optMaxParams, args->head.size(), CountMismatch::Arg, false}};
                     return {ArityMismatch, {error}};
                 }
                 else if (auto vtp = get<VariadicTypePack>(follow(paramIter.tail())))
                 {
-                    if (auto errors = tryUnify(argLoc, args->head[argOffset], vtp->ty))
+                    if (auto errors = tryUnify(argExpr->location, args->head[argOffset], vtp->ty))
                         argumentErrors.insert(argumentErrors.end(), errors->begin(), errors->end());
                 }
+                else if (get<GenericTypePack>(follow(paramIter.tail())))
+                    argumentErrors.push_back(TypeError{argExpr->location, TypePackMismatch{fn->argTypes, arena->addTypePack(*args)}});
 
                 ++argOffset;
             }
@@ -1333,18 +1397,18 @@ struct TypeChecker2
                 // It may have a tail, however, so check that.
                 if (auto vtp = get<VariadicTypePack>(follow(args->tail)))
                 {
-                    Location argLoc = argLocs->at(argLocs->size() - 1);
+                    AstExpr* argExpr = argExprs->at(argExprs->size() - 1);
 
-                    if (auto errors = tryUnify(argLoc, vtp->ty, *paramIter))
+                    if (auto errors = tryUnify(argExpr->location, vtp->ty, *paramIter))
                         argumentErrors.insert(argumentErrors.end(), errors->begin(), errors->end());
                 }
                 else if (!isOptional(*paramIter))
                 {
-                    Location argLoc = argLocs->empty() ? fnLoc : argLocs->at(argLocs->size() - 1);
+                    AstExpr* argExpr = argExprs->empty() ? fnExpr : argExprs->at(argExprs->size() - 1);
 
                     // It is ok to have excess parameters as long as they are all optional.
                     auto [minParams, optMaxParams] = getParameterExtents(TxnLog::empty(), fn->argTypes);
-                    TypeError error{argLoc, CountMismatch{minParams, optMaxParams, args->head.size(), CountMismatch::Arg, false}};
+                    TypeError error{argExpr->location, CountMismatch{minParams, optMaxParams, args->head.size(), CountMismatch::Arg, false}};
                     return {ArityMismatch, {error}};
                 }
 
@@ -1355,13 +1419,27 @@ struct TypeChecker2
             LUAU_ASSERT(paramIter == end(fn->argTypes));
             LUAU_ASSERT(argOffset == args->head.size());
 
+            const Location argLoc = argExprs->empty() ? Location{} // TODO
+                : argExprs->at(argExprs->size() - 1)->location;
+
             if (paramIter.tail() && args->tail)
             {
-                Location argLoc = argLocs->at(argLocs->size() - 1);
-
                 if (auto errors = tryUnify(argLoc, *args->tail, *paramIter.tail()))
                     argumentErrors.insert(argumentErrors.end(), errors->begin(), errors->end());
             }
+            else if (paramIter.tail())
+            {
+                const TypePackId paramTail = follow(*paramIter.tail());
+
+                if (get<GenericTypePack>(paramTail))
+                {
+                    argumentErrors.push_back(TypeError{argLoc, TypePackMismatch{fn->argTypes, arena->addTypePack(*args)}});
+                }
+                else if (get<VariadicTypePack>(paramTail))
+                {
+                    // Nothing.  This is ok.
+                }
+            }
 
             return {argumentErrors.empty() ? Ok : OverloadIsNonviable, argumentErrors};
         }
@@ -1409,14 +1487,14 @@ struct TypeChecker2
         }
 
     public:
-        void resolve(TypeId fnTy, const TypePack* args, Location selfLoc, const std::vector<Location>* argLocs)
+        void resolve(TypeId fnTy, const TypePack* args, AstExpr* selfExpr, const std::vector<AstExpr*>* argExprs)
         {
             fnTy = follow(fnTy);
 
             auto it = get<IntersectionType>(fnTy);
             if (!it)
             {
-                auto [analysis, errors] = checkOverload(fnTy, args, selfLoc, argLocs);
+                auto [analysis, errors] = checkOverload(fnTy, args, selfExpr, argExprs);
                 add(analysis, fnTy, std::move(errors));
                 return;
             }
@@ -1426,7 +1504,7 @@ struct TypeChecker2
                 if (resolution.find(ty) != resolution.end())
                     continue;
 
-                auto [analysis, errors] = checkOverload(ty, args, selfLoc, argLocs);
+                auto [analysis, errors] = checkOverload(ty, args, selfExpr, argExprs);
                 add(analysis, ty, std::move(errors));
             }
         }
@@ -1508,8 +1586,7 @@ struct TypeChecker2
             return;
         }
 
-        // TODO!
-        visit(indexExpr->expr, ValueContext::LValue);
+        visit(indexExpr->expr, ValueContext::RValue);
         visit(indexExpr->index, ValueContext::RValue);
 
         NotNull<Scope> scope = stack.back();
@@ -1576,7 +1653,8 @@ struct TypeChecker2
                     TypeId inferredArgTy = *argIt;
                     TypeId annotatedArgTy = lookupAnnotation(arg->annotation);
 
-                    if (!isSubtype(inferredArgTy, annotatedArgTy, stack.back()))
+                    if (!isSubtype(inferredArgTy, annotatedArgTy, stack.back()) &&
+                        !isErrorSuppressing(arg->location, inferredArgTy, arg->annotation->location, annotatedArgTy))
                     {
                         reportError(TypeMismatch{inferredArgTy, annotatedArgTy}, arg->location);
                     }
@@ -1610,7 +1688,7 @@ struct TypeChecker2
         TypeId operandType = lookupType(expr->expr);
         TypeId resultType = lookupType(expr);
 
-        if (get<AnyType>(operandType) || get<ErrorType>(operandType) || get<NeverType>(operandType))
+        if (isErrorSuppressing(expr->expr->location, operandType))
             return;
 
         if (auto it = kUnaryOpMetamethods.find(expr->op); it != kUnaryOpMetamethods.end())
@@ -1645,7 +1723,7 @@ struct TypeChecker2
                     TypeId expectedFunction = testArena.addType(FunctionType{expectedArgs, expectedRet});
 
                     ErrorVec errors = tryUnify(scope, expr->location, *mm, expectedFunction);
-                    if (!errors.empty())
+                    if (!errors.empty() && !isErrorSuppressing(expr->expr->location, *firstArg, expr->expr->location, operandType))
                     {
                         reportError(TypeMismatch{*firstArg, operandType}, expr->location);
                         return;
@@ -1660,7 +1738,10 @@ struct TypeChecker2
         {
             DenseHashSet<TypeId> seen{nullptr};
             int recursionCount = 0;
+            const NormalizedType* nty = normalizer.normalize(operandType);
 
+            if (nty && nty->shouldSuppressErrors())
+                return;
 
             if (!hasLength(operandType, seen, &recursionCount))
             {
@@ -1719,6 +1800,8 @@ struct TypeChecker2
             return leftType;
         else if (get<AnyType>(rightType) || get<ErrorType>(rightType) || get<NeverType>(rightType))
             return rightType;
+        else if ((normLeft && normLeft->shouldSuppressErrors()) || (normRight && normRight->shouldSuppressErrors()))
+            return builtinTypes->anyType; // we can't say anything better if it's error suppressing but not any or error alone.
 
         if ((get<BlockedType>(leftType) || get<FreeType>(leftType) || get<GenericType>(leftType)) && !isEquality && !isLogical)
         {
@@ -1933,6 +2016,9 @@ struct TypeChecker2
         case AstExprBinary::Op::CompareLe:
         case AstExprBinary::Op::CompareLt:
         {
+            if (normLeft && normLeft->shouldSuppressErrors())
+                return builtinTypes->numberType;
+
             if (normLeft && normLeft->isExactlyNumber())
             {
                 reportErrors(tryUnify(scope, expr->right->location, rightType, builtinTypes->numberType));
@@ -2324,7 +2410,7 @@ struct TypeChecker2
         TypeArena arena;
         Unifier u{NotNull{&normalizer}, scope, Location{}, Covariant};
         u.hideousFixMeGenericsAreActuallyFree = genericsOkay;
-        u.enableScopeTests();
+        u.enableNewSolver();
 
         u.tryUnify(subTy, superTy);
         const bool ok = u.errors.empty() && u.log.empty();
@@ -2338,9 +2424,12 @@ struct TypeChecker2
         Unifier u{NotNull{&normalizer}, scope, location, Covariant};
         u.ctx = context;
         u.hideousFixMeGenericsAreActuallyFree = genericsOkay;
-        u.enableScopeTests();
+        u.enableNewSolver();
         u.tryUnify(subTy, superTy);
 
+        if (isErrorSuppressing(location, subTy, location, superTy))
+            return {};
+
         return std::move(u.errors);
     }
 
@@ -2376,6 +2465,7 @@ struct TypeChecker2
             return;
         }
 
+        // if the type is error suppressing, we don't actually have any work left to do.
         if (norm->shouldSuppressErrors())
             return;
 
@@ -2542,6 +2632,50 @@ struct TypeChecker2
         if (!candidates.empty())
             data = TypeErrorData(UnknownPropButFoundLikeProp{utk->table, utk->key, candidates});
     }
+
+    bool isErrorSuppressing(Location loc, TypeId ty)
+    {
+        switch (shouldSuppressErrors(NotNull{&normalizer}, ty))
+        {
+        case ErrorSuppression::DoNotSuppress:
+            return false;
+        case ErrorSuppression::Suppress:
+            return true;
+        case ErrorSuppression::NormalizationFailed:
+            reportError(NormalizationTooComplex{}, loc);
+            return false;
+        };
+
+        LUAU_ASSERT(false);
+        return false; // UNREACHABLE
+    }
+
+    bool isErrorSuppressing(Location loc1, TypeId ty1, Location loc2, TypeId ty2)
+    {
+        return isErrorSuppressing(loc1, ty1) || isErrorSuppressing(loc2, ty2);
+    }
+
+    bool isErrorSuppressing(Location loc, TypePackId tp)
+    {
+        switch (shouldSuppressErrors(NotNull{&normalizer}, tp))
+        {
+        case ErrorSuppression::DoNotSuppress:
+            return false;
+        case ErrorSuppression::Suppress:
+            return true;
+        case ErrorSuppression::NormalizationFailed:
+            reportError(NormalizationTooComplex{}, loc);
+            return false;
+        };
+
+        LUAU_ASSERT(false);
+        return false; // UNREACHABLE
+    }
+
+    bool isErrorSuppressing(Location loc1, TypePackId tp1, Location loc2, TypePackId tp2)
+    {
+        return isErrorSuppressing(loc1, tp1) || isErrorSuppressing(loc2, tp2);
+    }
 };
 
 void check(

Analysis/src/TypeInfer.cpp

@@ -36,6 +36,7 @@ LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauSharedSelf, false)
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
 LUAU_FASTFLAGVARIABLE(LuauAllowIndexClassParameters, false)
+LUAU_FASTFLAGVARIABLE(LuauFixCyclicModuleExports, false)
 LUAU_FASTFLAG(LuauOccursIsntAlwaysFailure)
 LUAU_FASTFLAGVARIABLE(LuauTypecheckTypeguards, false)
 LUAU_FASTFLAGVARIABLE(LuauTinyControlFlowAnalysis, false)
@@ -269,6 +270,8 @@ ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mo
     currentModule.reset(new Module);
     currentModule->name = module.name;
     currentModule->humanReadableName = module.humanReadableName;
+    currentModule->internalTypes.owningModule = currentModule.get();
+    currentModule->interfaceTypes.owningModule = currentModule.get();
     currentModule->type = module.type;
     currentModule->allocator = module.allocator;
     currentModule->names = module.names;
@@ -1193,6 +1196,19 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatLocal& local)
                     {
                         scope->importedTypeBindings[name] = module->exportedTypeBindings;
                         scope->importedModules[name] = moduleInfo->name;
+
+                        if (FFlag::LuauFixCyclicModuleExports)
+                        {
+                            // Imported types of requires that transitively refer to current module have to be replaced with 'any'
+                            for (const auto& [location, path] : requireCycles)
+                            {
+                                if (!path.empty() && path.front() == moduleInfo->name)
+                                {
+                                    for (auto& [name, tf] : scope->importedTypeBindings[name])
+                                        tf = TypeFun{{}, {}, anyType};
+                                }
+                            }
+                        }
                     }
 
                     // In non-strict mode we force the module type on the variable, in strict mode it is already unified

Analysis/src/TypeUtils.cpp

@@ -295,4 +295,58 @@ TypeId stripNil(NotNull<BuiltinTypes> builtinTypes, TypeArena& arena, TypeId ty)
     return follow(ty);
 }
 
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypeId ty)
+{
+    const NormalizedType* normType = normalizer->normalize(ty);
+
+    if (!normType)
+        return ErrorSuppression::NormalizationFailed;
+
+    return (normType->shouldSuppressErrors()) ? ErrorSuppression::Suppress : ErrorSuppression::DoNotSuppress;
+}
+
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypePackId tp)
+{
+    auto [tys, tail] = flatten(tp);
+
+    // check the head, one type at a time
+    for (TypeId ty : tys)
+    {
+        auto result = shouldSuppressErrors(normalizer, ty);
+        if (result != ErrorSuppression::DoNotSuppress)
+            return result;
+    }
+
+    // check the tail if we have one and it's finite
+    if (tail && finite(*tail))
+        return shouldSuppressErrors(normalizer, *tail);
+
+    return ErrorSuppression::DoNotSuppress;
+}
+
+// This is a useful helper because it is often the case that we are looking at specifically a pair of types that might suppress.
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypeId ty1, TypeId ty2)
+{
+    auto result = shouldSuppressErrors(normalizer, ty1);
+
+    // if ty1 is do not suppress, ty2 determines our overall behavior
+    if (result == ErrorSuppression::DoNotSuppress)
+        return shouldSuppressErrors(normalizer, ty2);
+
+    // otherwise, ty1 is either suppress or normalization failure which are both the appropriate overarching result
+    return result;
+}
+
+ErrorSuppression shouldSuppressErrors(NotNull<Normalizer> normalizer, TypePackId tp1, TypePackId tp2)
+{
+    auto result = shouldSuppressErrors(normalizer, tp1);
+
+    // if tp1 is do not suppress, tp2 determines our overall behavior
+    if (result == ErrorSuppression::DoNotSuppress)
+        return shouldSuppressErrors(normalizer, tp2);
+
+    // otherwise, tp1 is either suppress or normalization failure which are both the appropriate overarching result
+    return result;
+}
+
 } // namespace Luau

Analysis/src/Unifier.cpp

@@ -22,7 +22,6 @@ LUAU_FASTFLAGVARIABLE(LuauInstantiateInSubtyping, false)
 LUAU_FASTFLAGVARIABLE(LuauMaintainScopesInUnifier, false)
 LUAU_FASTFLAGVARIABLE(LuauTransitiveSubtyping, false)
 LUAU_FASTFLAGVARIABLE(LuauOccursIsntAlwaysFailure, false)
-LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTFLAG(LuauNormalizeBlockedTypes)
 LUAU_FASTFLAG(LuauAlwaysCommitInferencesOfFunctionCalls)
 
@@ -50,7 +49,7 @@ struct PromoteTypeLevels final : TypeOnceVisitor
     template<typename TID, typename T>
     void promote(TID ty, T* t)
     {
-        if (FFlag::DebugLuauDeferredConstraintResolution && !t)
+        if (useScopes && !t)
             return;
 
         LUAU_ASSERT(t);
@@ -369,7 +368,6 @@ static std::optional<std::pair<Luau::Name, const SingletonType*>> getTableMatchT
     return std::nullopt;
 }
 
-// TODO: Inline and clip with FFlag::DebugLuauDeferredConstraintResolution
 template<typename TY_A, typename TY_B>
 static bool subsumes(bool useScopes, TY_A* left, TY_B* right)
 {
@@ -406,11 +404,11 @@ Unifier::Unifier(NotNull<Normalizer> normalizer, NotNull<Scope> scope, const Loc
     LUAU_ASSERT(sharedState.iceHandler);
 }
 
-void Unifier::tryUnify(TypeId subTy, TypeId superTy, bool isFunctionCall, bool isIntersection)
+void Unifier::tryUnify(TypeId subTy, TypeId superTy, bool isFunctionCall, bool isIntersection, const LiteralProperties* literalProperties)
 {
     sharedState.counters.iterationCount = 0;
 
-    tryUnify_(subTy, superTy, isFunctionCall, isIntersection);
+    tryUnify_(subTy, superTy, isFunctionCall, isIntersection, literalProperties);
 }
 
 static bool isBlocked(const TxnLog& log, TypeId ty)
@@ -425,7 +423,7 @@ static bool isBlocked(const TxnLog& log, TypePackId tp)
     return get<BlockedTypePack>(tp);
 }
 
-void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool isIntersection)
+void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool isIntersection, const LiteralProperties* literalProperties)
 {
     RecursionLimiter _ra(&sharedState.counters.recursionCount, sharedState.counters.recursionLimit);
 
@@ -443,6 +441,16 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     if (superTy == subTy)
         return;
 
+    if (isBlocked(log, subTy) && isBlocked(log, superTy))
+    {
+        blockedTypes.push_back(subTy);
+        blockedTypes.push_back(superTy);
+    }
+    else if (isBlocked(log, subTy))
+        blockedTypes.push_back(subTy);
+    else if (isBlocked(log, superTy))
+        blockedTypes.push_back(superTy);
+
     if (log.get<TypeFamilyInstanceType>(superTy))
     {
         // We do not report errors from reducing here. This is because we will
@@ -470,7 +478,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     auto superFree = log.getMutable<FreeType>(superTy);
     auto subFree = log.getMutable<FreeType>(subTy);
 
-    if (superFree && subFree && subsumes(useScopes, superFree, subFree))
+    if (superFree && subFree && subsumes(useNewSolver, superFree, subFree))
     {
         if (!occursCheck(subTy, superTy, /* reversed = */ false))
             log.replace(subTy, BoundType(superTy));
@@ -481,7 +489,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     {
         if (!occursCheck(superTy, subTy, /* reversed = */ true))
         {
-            if (subsumes(useScopes, superFree, subFree))
+            if (subsumes(useNewSolver, superFree, subFree))
             {
                 log.changeLevel(subTy, superFree->level);
             }
@@ -495,7 +503,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     {
         // Unification can't change the level of a generic.
         auto subGeneric = log.getMutable<GenericType>(subTy);
-        if (subGeneric && !subsumes(useScopes, subGeneric, superFree))
+        if (subGeneric && !subsumes(useNewSolver, subGeneric, superFree))
         {
             // TODO: a more informative error message? CLI-39912
             reportError(location, GenericError{"Generic subtype escaping scope"});
@@ -504,7 +512,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
         if (!occursCheck(superTy, subTy, /* reversed = */ true))
         {
-            promoteTypeLevels(log, types, superFree->level, superFree->scope, useScopes, subTy);
+            promoteTypeLevels(log, types, superFree->level, superFree->scope, useNewSolver, subTy);
 
             Widen widen{types, builtinTypes};
             log.replace(superTy, BoundType(widen(subTy)));
@@ -521,7 +529,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
         // Unification can't change the level of a generic.
         auto superGeneric = log.getMutable<GenericType>(superTy);
-        if (superGeneric && !subsumes(useScopes, superGeneric, subFree))
+        if (superGeneric && !subsumes(useNewSolver, superGeneric, subFree))
         {
             // TODO: a more informative error message? CLI-39912
             reportError(location, GenericError{"Generic supertype escaping scope"});
@@ -530,7 +538,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
         if (!occursCheck(subTy, superTy, /* reversed = */ false))
         {
-            promoteTypeLevels(log, types, subFree->level, subFree->scope, useScopes, superTy);
+            promoteTypeLevels(log, types, subFree->level, subFree->scope, useNewSolver, superTy);
             log.replace(subTy, BoundType(superTy));
         }
 
@@ -542,7 +550,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
         auto superGeneric = log.getMutable<GenericType>(superTy);
         auto subGeneric = log.getMutable<GenericType>(subTy);
 
-        if (superGeneric && subGeneric && subsumes(useScopes, superGeneric, subGeneric))
+        if (superGeneric && subGeneric && subsumes(useNewSolver, superGeneric, subGeneric))
         {
             if (!occursCheck(subTy, superTy, /* reversed = */ false))
                 log.replace(subTy, BoundType(superTy));
@@ -637,16 +645,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
     size_t errorCount = errors.size();
 
-    if (isBlocked(log, subTy) && isBlocked(log, superTy))
-    {
-        blockedTypes.push_back(subTy);
-        blockedTypes.push_back(superTy);
-    }
-    else if (isBlocked(log, subTy))
-        blockedTypes.push_back(subTy);
-    else if (isBlocked(log, superTy))
-        blockedTypes.push_back(superTy);
-    else if (const UnionType* subUnion = log.getMutable<UnionType>(subTy))
+    if (const UnionType* subUnion = log.getMutable<UnionType>(subTy))
     {
         tryUnifyUnionWithType(subTy, subUnion, superTy);
     }
@@ -717,7 +716,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
     else if (log.getMutable<TableType>(superTy) && log.getMutable<TableType>(subTy))
     {
-        tryUnifyTables(subTy, superTy, isIntersection);
+        tryUnifyTables(subTy, superTy, isIntersection, literalProperties);
     }
     else if (log.get<TableType>(superTy) && (log.get<PrimitiveType>(subTy) || log.get<SingletonType>(subTy)))
     {
@@ -772,7 +771,7 @@ void Unifier::tryUnifyUnionWithType(TypeId subTy, const UnionType* subUnion, Typ
         Unifier innerState = makeChildUnifier();
         innerState.tryUnify_(type, superTy);
 
-        if (FFlag::DebugLuauDeferredConstraintResolution)
+        if (useNewSolver)
             logs.push_back(std::move(innerState.log));
 
         if (auto e = hasUnificationTooComplex(innerState.errors))
@@ -955,7 +954,7 @@ void Unifier::tryUnifyTypeWithUnion(TypeId subTy, TypeId superTy, const UnionTyp
         if (FFlag::LuauTransitiveSubtyping ? !innerState.failure : innerState.errors.empty())
         {
             found = true;
-            if (FFlag::DebugLuauDeferredConstraintResolution)
+            if (useNewSolver)
                 logs.push_back(std::move(innerState.log));
             else
             {
@@ -980,7 +979,7 @@ void Unifier::tryUnifyTypeWithUnion(TypeId subTy, TypeId superTy, const UnionTyp
         }
     }
 
-    if (FFlag::DebugLuauDeferredConstraintResolution)
+    if (useNewSolver)
         log.concatAsUnion(combineLogsIntoUnion(std::move(logs)), NotNull{types});
 
     if (unificationTooComplex)
@@ -1061,14 +1060,14 @@ void Unifier::tryUnifyTypeWithIntersection(TypeId subTy, TypeId superTy, const I
                 firstFailedOption = {innerState.errors.front()};
         }
 
-        if (FFlag::DebugLuauDeferredConstraintResolution)
+        if (useNewSolver)
             logs.push_back(std::move(innerState.log));
         else
             log.concat(std::move(innerState.log));
         failure |= innerState.failure;
     }
 
-    if (FFlag::DebugLuauDeferredConstraintResolution)
+    if (useNewSolver)
         log.concat(combineLogsIntoIntersection(std::move(logs)));
 
     if (unificationTooComplex)
@@ -1118,7 +1117,7 @@ void Unifier::tryUnifyIntersectionWithType(TypeId subTy, const IntersectionType*
         }
     }
 
-    if (FFlag::DebugLuauDeferredConstraintResolution && normalize)
+    if (useNewSolver && normalize)
     {
         // We cannot normalize a type that contains blocked types.  We have to
         // stop for now if we find any.
@@ -1161,7 +1160,7 @@ void Unifier::tryUnifyIntersectionWithType(TypeId subTy, const IntersectionType*
         {
             found = true;
             errorsSuppressed = innerState.failure;
-            if (FFlag::DebugLuauDeferredConstraintResolution || (FFlag::LuauTransitiveSubtyping && innerState.failure))
+            if (useNewSolver || (FFlag::LuauTransitiveSubtyping && innerState.failure))
                 logs.push_back(std::move(innerState.log));
             else
             {
@@ -1176,7 +1175,7 @@ void Unifier::tryUnifyIntersectionWithType(TypeId subTy, const IntersectionType*
         }
     }
 
-    if (FFlag::DebugLuauDeferredConstraintResolution)
+    if (useNewSolver)
         log.concat(combineLogsIntoIntersection(std::move(logs)));
     else if (FFlag::LuauTransitiveSubtyping && errorsSuppressed)
         log.concat(std::move(logs.front()));
@@ -1296,7 +1295,7 @@ void Unifier::tryUnifyNormalizedTypes(
             }
         }
 
-        if (FFlag::DebugLuauDeferredConstraintResolution)
+        if (useNewSolver)
         {
             for (TypeId superTable : superNorm.tables)
             {
@@ -1527,6 +1526,15 @@ struct WeirdIter
         return pack != nullptr && index < pack->head.size();
     }
 
+    std::optional<TypePackId> tail() const
+    {
+        if (!pack)
+            return packId;
+
+        LUAU_ASSERT(index == pack->head.size());
+        return pack->tail;
+    }
+
     bool advance()
     {
         if (!pack)
@@ -1588,9 +1596,9 @@ struct WeirdIter
     }
 };
 
-void Unifier::enableScopeTests()
+void Unifier::enableNewSolver()
 {
-    useScopes = true;
+    useNewSolver = true;
     log.useScopes = true;
 }
 
@@ -1664,25 +1672,26 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
         blockedTypePacks.push_back(superTp);
     }
     else if (isBlocked(log, subTp))
-    {
         blockedTypePacks.push_back(subTp);
-    }
     else if (isBlocked(log, superTp))
-    {
         blockedTypePacks.push_back(superTp);
-    }
-    if (log.getMutable<FreeTypePack>(superTp))
+
+    if (auto superFree = log.getMutable<FreeTypePack>(superTp))
     {
         if (!occursCheck(superTp, subTp, /* reversed = */ true))
         {
             Widen widen{types, builtinTypes};
+            if (useNewSolver)
+                promoteTypeLevels(log, types, superFree->level, superFree->scope, /*useScopes*/ true, subTp);
             log.replace(superTp, Unifiable::Bound<TypePackId>(widen(subTp)));
         }
     }
-    else if (log.getMutable<FreeTypePack>(subTp))
+    else if (auto subFree = log.getMutable<FreeTypePack>(subTp))
     {
         if (!occursCheck(subTp, superTp, /* reversed = */ false))
         {
+            if (useNewSolver)
+                promoteTypeLevels(log, types, subFree->level, subFree->scope, /*useScopes*/ true, superTp);
             log.replace(subTp, Unifiable::Bound<TypePackId>(superTp));
         }
     }
@@ -1771,28 +1780,74 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
             // If both are at the end, we're done
             if (!superIter.good() && !subIter.good())
             {
-                const bool lFreeTail = superTpv->tail && log.getMutable<FreeTypePack>(log.follow(*superTpv->tail)) != nullptr;
-                const bool rFreeTail = subTpv->tail && log.getMutable<FreeTypePack>(log.follow(*subTpv->tail)) != nullptr;
-                if (lFreeTail && rFreeTail)
+                if (useNewSolver)
                 {
-                    tryUnify_(*subTpv->tail, *superTpv->tail);
-                }
-                else if (lFreeTail)
-                {
-                    tryUnify_(emptyTp, *superTpv->tail);
-                }
-                else if (rFreeTail)
-                {
-                    tryUnify_(emptyTp, *subTpv->tail);
-                }
-                else if (subTpv->tail && superTpv->tail)
-                {
-                    if (log.getMutable<VariadicTypePack>(superIter.packId))
-                        tryUnifyVariadics(subIter.packId, superIter.packId, false, int(subIter.index));
-                    else if (log.getMutable<VariadicTypePack>(subIter.packId))
-                        tryUnifyVariadics(superIter.packId, subIter.packId, true, int(superIter.index));
+                    if (subIter.tail() && superIter.tail())
+                        tryUnify_(*subIter.tail(), *superIter.tail());
+                    else if (subIter.tail())
+                    {
+                        const TypePackId subTail = log.follow(*subIter.tail());
+
+                        if (log.get<FreeTypePack>(subTail))
+                            tryUnify_(subTail, emptyTp);
+                        else if (log.get<GenericTypePack>(subTail))
+                            reportError(location, TypePackMismatch{subTail, emptyTp});
+                        else if (log.get<VariadicTypePack>(subTail) || log.get<ErrorTypePack>(subTail))
+                        {
+                            // Nothing.  This is ok.
+                        }
+                        else
+                        {
+                            ice("Unexpected subtype tail pack " + toString(subTail), location);
+                        }
+                    }
+                    else if (superIter.tail())
+                    {
+                        const TypePackId superTail = log.follow(*superIter.tail());
+
+                        if (log.get<FreeTypePack>(superTail))
+                            tryUnify_(emptyTp, superTail);
+                        else if (log.get<GenericTypePack>(superTail))
+                            reportError(location, TypePackMismatch{emptyTp, superTail});
+                        else if (log.get<VariadicTypePack>(superTail) || log.get<ErrorTypePack>(superTail))
+                        {
+                            // Nothing.  This is ok.
+                        }
+                        else
+                        {
+                            ice("Unexpected supertype tail pack " + toString(superTail), location);
+                        }
+                    }
                     else
+                    {
+                        // Nothing.  This is ok.
+                    }
+                }
+                else
+                {
+                    const bool lFreeTail = superTpv->tail && log.getMutable<FreeTypePack>(log.follow(*superTpv->tail)) != nullptr;
+                    const bool rFreeTail = subTpv->tail && log.getMutable<FreeTypePack>(log.follow(*subTpv->tail)) != nullptr;
+                    if (lFreeTail && rFreeTail)
+                    {
                         tryUnify_(*subTpv->tail, *superTpv->tail);
+                    }
+                    else if (lFreeTail)
+                    {
+                        tryUnify_(emptyTp, *superTpv->tail);
+                    }
+                    else if (rFreeTail)
+                    {
+                        tryUnify_(emptyTp, *subTpv->tail);
+                    }
+                    else if (subTpv->tail && superTpv->tail)
+                    {
+                        if (log.getMutable<VariadicTypePack>(superIter.packId))
+                            tryUnifyVariadics(subIter.packId, superIter.packId, false, int(subIter.index));
+                        else if (log.getMutable<VariadicTypePack>(subIter.packId))
+                            tryUnifyVariadics(superIter.packId, subIter.packId, true, int(superIter.index));
+                        else
+                            tryUnify_(*subTpv->tail, *superTpv->tail);
+                    }
                 }
 
                 break;
@@ -2049,7 +2104,7 @@ struct Resetter
 
 } // namespace
 
-void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
+void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection, const LiteralProperties* literalProperties)
 {
     if (isPrim(log.follow(subTy), PrimitiveType::Table))
         subTy = builtinTypes->emptyTableType;
@@ -2134,7 +2189,8 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         {
             // TODO: read-only properties don't need invariance
             Resetter resetter{&variance};
-            variance = Invariant;
+            if (!literalProperties || !literalProperties->contains(name))
+                variance = Invariant;
 
             Unifier innerState = makeChildUnifier();
             innerState.tryUnify_(r->second.type(), prop.type());
@@ -2150,7 +2206,8 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
             // TODO: read-only indexers don't need invariance
             // TODO: really we should only allow this if prop.type is optional.
             Resetter resetter{&variance};
-            variance = Invariant;
+            if (!literalProperties || !literalProperties->contains(name))
+                variance = Invariant;
 
             Unifier innerState = makeChildUnifier();
             innerState.tryUnify_(subTable->indexer->indexResultType, prop.type());
@@ -2213,10 +2270,17 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
             // TODO: read-only indexers don't need invariance
             // TODO: really we should only allow this if prop.type is optional.
             Resetter resetter{&variance};
-            variance = Invariant;
+            if (!literalProperties || !literalProperties->contains(name))
+                variance = Invariant;
 
             Unifier innerState = makeChildUnifier();
-            innerState.tryUnify_(superTable->indexer->indexResultType, prop.type());
+            if (useNewSolver)
+                innerState.tryUnify_(prop.type(), superTable->indexer->indexResultType);
+            else
+            {
+                // Incredibly, the old solver depends on this bug somehow.
+                innerState.tryUnify_(superTable->indexer->indexResultType, prop.type());
+            }
 
             checkChildUnifierTypeMismatch(innerState.errors, name, superTy, subTy);
 
@@ -2478,7 +2542,7 @@ void Unifier::tryUnifyWithMetatable(TypeId subTy, TypeId superTy, bool reversed)
         {
         case TableState::Free:
         {
-            if (FFlag::DebugLuauDeferredConstraintResolution)
+            if (useNewSolver)
             {
                 Unifier innerState = makeChildUnifier();
                 bool missingProperty = false;
@@ -2843,8 +2907,8 @@ std::optional<TypeId> Unifier::findTablePropertyRespectingMeta(TypeId lhsType, N
 
 TxnLog Unifier::combineLogsIntoIntersection(std::vector<TxnLog> logs)
 {
-    LUAU_ASSERT(FFlag::DebugLuauDeferredConstraintResolution);
-    TxnLog result(useScopes);
+    LUAU_ASSERT(useNewSolver);
+    TxnLog result(useNewSolver);
     for (TxnLog& log : logs)
         result.concatAsIntersections(std::move(log), NotNull{types});
     return result;
@@ -2852,7 +2916,7 @@ TxnLog Unifier::combineLogsIntoIntersection(std::vector<TxnLog> logs)
 
 TxnLog Unifier::combineLogsIntoUnion(std::vector<TxnLog> logs)
 {
-    TxnLog result(useScopes);
+    TxnLog result(useNewSolver);
     for (TxnLog& log : logs)
         result.concatAsUnion(std::move(log), NotNull{types});
     return result;
@@ -3012,8 +3076,8 @@ Unifier Unifier::makeChildUnifier()
     u.normalize = normalize;
     u.checkInhabited = checkInhabited;
 
-    if (useScopes)
-        u.enableScopeTests();
+    if (useNewSolver)
+        u.enableNewSolver();
 
     return u;
 }

CLI/Repl.cpp

@@ -274,9 +274,6 @@ std::string runCode(lua_State* L, const std::string& source)
         return error;
     }
 
-    if (codegen)
-        Luau::CodeGen::compile(L, -1);
-
     lua_State* T = lua_newthread(L);
 
     lua_pushvalue(L, -2);

CodeGen/include/Luau/CodeGen.h

@@ -12,12 +12,18 @@ namespace Luau
 namespace CodeGen
 {
 
+enum CodeGenFlags
+{
+    // Only run native codegen for modules that have been marked with --!native
+    CodeGen_OnlyNativeModules = 1 << 0,
+};
+
 bool isSupported();
 
 void create(lua_State* L);
 
 // Builds target function and all inner functions
-void compile(lua_State* L, int idx);
+void compile(lua_State* L, int idx, unsigned int flags = 0);
 
 using AnnotatorFn = void (*)(void* context, std::string& result, int fid, int instpos);
 

CodeGen/include/Luau/IrData.h

@@ -77,6 +77,12 @@ enum class IrCmd : uint8_t
     // B: unsigned int (hash)
     GET_HASH_NODE_ADDR,
 
+    // Get pointer (TValue) to Closure upvalue.
+    // A: pointer or undef (Closure)
+    // B: UPn
+    // When undef is specified, uses current function Closure.
+    GET_CLOSURE_UPVAL_ADDR,
+
     // Store a tag into TValue
     // A: Rn
     // B: tag
@@ -542,10 +548,10 @@ enum class IrCmd : uint8_t
     FALLBACK_GETVARARGS,
 
     // Create closure from a child proto
-    // A: unsigned int (bytecode instruction index)
-    // B: Rn (dest)
+    // A: unsigned int (nups)
+    // B: pointer (table)
     // C: unsigned int (protoid)
-    FALLBACK_NEWCLOSURE,
+    NEWCLOSURE,
 
     // Create closure from a pre-created function object (reusing it unless environments diverge)
     // A: unsigned int (bytecode instruction index)
@@ -600,6 +606,10 @@ enum class IrCmd : uint8_t
     // Returns the string name of a type either from a __type metatable field or just based on the tag, alternative for typeof(x)
     // A: Rn
     GET_TYPEOF,
+
+    // Find or create an upval at the given level
+    // A: Rn (level)
+    FINDUPVAL,
 };
 
 enum class IrConstKind : uint8_t

CodeGen/include/Luau/IrUtils.h

@@ -150,6 +150,7 @@ inline bool hasResult(IrCmd cmd)
     case IrCmd::GET_ARR_ADDR:
     case IrCmd::GET_SLOT_NODE_ADDR:
     case IrCmd::GET_HASH_NODE_ADDR:
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
     case IrCmd::ADD_INT:
     case IrCmd::SUB_INT:
     case IrCmd::ADD_NUM:
@@ -192,6 +193,8 @@ inline bool hasResult(IrCmd cmd)
     case IrCmd::INVOKE_LIBM:
     case IrCmd::GET_TYPE:
     case IrCmd::GET_TYPEOF:
+    case IrCmd::NEWCLOSURE:
+    case IrCmd::FINDUPVAL:
         return true;
     default:
         break;

CodeGen/include/luacodegen.h

@@ -6,7 +6,7 @@
 #define LUACODEGEN_API extern
 #endif
 
-struct lua_State;
+typedef struct lua_State lua_State;
 
 // returns 1 if Luau code generator is supported, 0 otherwise
 LUACODEGEN_API int luau_codegen_supported(void);

CodeGen/src/CodeGen.cpp

@@ -239,7 +239,7 @@ void create(lua_State* L)
     ecb->enter = onEnter;
 }
 
-void compile(lua_State* L, int idx)
+void compile(lua_State* L, int idx, unsigned int flags)
 {
     LUAU_ASSERT(lua_isLfunction(L, idx));
     const TValue* func = luaA_toobject(L, idx);
@@ -249,6 +249,13 @@ void compile(lua_State* L, int idx)
     if (!data)
         return;
 
+    Proto* root = clvalue(func)->l.p;
+    if ((flags & CodeGen_OnlyNativeModules) != 0 && (root->flags & LPF_NATIVE_MODULE) == 0)
+        return;
+
+    std::vector<Proto*> protos;
+    gatherFunctions(protos, root);
+
 #if defined(__aarch64__)
     static unsigned int cpuFeatures = getCpuFeaturesA64();
     A64::AssemblyBuilderA64 build(/* logText= */ false, cpuFeatures);
@@ -256,9 +263,6 @@ void compile(lua_State* L, int idx)
     X64::AssemblyBuilderX64 build(/* logText= */ false);
 #endif
 
-    std::vector<Proto*> protos;
-    gatherFunctions(protos, clvalue(func)->l.p);
-
     ModuleHelpers helpers;
 #if defined(__aarch64__)
     A64::assembleHelpers(build, helpers);

CodeGen/src/IrAnalysis.cpp

@@ -427,9 +427,6 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
         case IrCmd::FALLBACK_GETVARARGS:
             defRange(vmRegOp(inst.b), function.intOp(inst.c));
             break;
-        case IrCmd::FALLBACK_NEWCLOSURE:
-            def(inst.b);
-            break;
         case IrCmd::FALLBACK_DUPCLOSURE:
             def(inst.b);
             break;
@@ -448,6 +445,10 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
             use(inst.a);
             break;
 
+        case IrCmd::FINDUPVAL:
+            use(inst.a);
+            break;
+
         default:
             // All instructions which reference registers have to be handled explicitly
             LUAU_ASSERT(inst.a.kind != IrOpKind::VmReg);

CodeGen/src/IrBuilder.cpp

@@ -452,7 +452,7 @@ void IrBuilder::translateInst(LuauOpcode op, const Instruction* pc, int i)
         inst(IrCmd::FALLBACK_GETVARARGS, constUint(i), vmReg(LUAU_INSN_A(*pc)), constInt(LUAU_INSN_B(*pc) - 1));
         break;
     case LOP_NEWCLOSURE:
-        inst(IrCmd::FALLBACK_NEWCLOSURE, constUint(i), vmReg(LUAU_INSN_A(*pc)), constUint(LUAU_INSN_D(*pc)));
+        translateInstNewClosure(*this, pc, i);
         break;
     case LOP_DUPCLOSURE:
         inst(IrCmd::FALLBACK_DUPCLOSURE, constUint(i), vmReg(LUAU_INSN_A(*pc)), vmConst(LUAU_INSN_D(*pc)));

CodeGen/src/IrDump.cpp

@@ -61,6 +61,12 @@ static const char* getTagName(uint8_t tag)
         return "tuserdata";
     case LUA_TTHREAD:
         return "tthread";
+    case LUA_TPROTO:
+        return "tproto";
+    case LUA_TUPVAL:
+        return "tupval";
+    case LUA_TDEADKEY:
+        return "tdeadkey";
     default:
         LUAU_ASSERT(!"Unknown type tag");
         LUAU_UNREACHABLE();
@@ -93,6 +99,8 @@ const char* getCmdName(IrCmd cmd)
         return "GET_SLOT_NODE_ADDR";
     case IrCmd::GET_HASH_NODE_ADDR:
         return "GET_HASH_NODE_ADDR";
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
+        return "GET_CLOSURE_UPVAL_ADDR";
     case IrCmd::STORE_TAG:
         return "STORE_TAG";
     case IrCmd::STORE_POINTER:
@@ -267,8 +275,8 @@ const char* getCmdName(IrCmd cmd)
         return "FALLBACK_PREPVARARGS";
     case IrCmd::FALLBACK_GETVARARGS:
         return "FALLBACK_GETVARARGS";
-    case IrCmd::FALLBACK_NEWCLOSURE:
-        return "FALLBACK_NEWCLOSURE";
+    case IrCmd::NEWCLOSURE:
+        return "NEWCLOSURE";
     case IrCmd::FALLBACK_DUPCLOSURE:
         return "FALLBACK_DUPCLOSURE";
     case IrCmd::FALLBACK_FORGPREP:
@@ -303,6 +311,8 @@ const char* getCmdName(IrCmd cmd)
         return "GET_TYPE";
     case IrCmd::GET_TYPEOF:
         return "GET_TYPEOF";
+    case IrCmd::FINDUPVAL:
+        return "FINDUPVAL";
     }
 
     LUAU_UNREACHABLE();

CodeGen/src/IrLoweringA64.cpp

@@ -314,6 +314,14 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         build.add(inst.regA64, inst.regA64, zextReg(temp2), kLuaNodeSizeLog2);
         break;
     }
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
+    {
+        inst.regA64 = regs.allocReuse(KindA64::x, index, {inst.a});
+        RegisterA64 cl = inst.a.kind == IrOpKind::Undef ? rClosure : regOp(inst.a);
+
+        build.add(inst.regA64, cl, uint16_t(offsetof(Closure, l.uprefs) + sizeof(TValue) * vmUpvalueOp(inst.b)));
+        break;
+    }
     case IrCmd::STORE_TAG:
     {
         RegisterA64 temp = regs.allocTemp(KindA64::w);
@@ -1044,13 +1052,20 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         bool continueInVm = (inst.d.kind == IrOpKind::Constant && intOp(inst.d));
         Label fresh; // used when guard aborts execution or jumps to a VM exit
         Label& fail = continueInVm ? helpers.exitContinueVmClearNativeFlag : getTargetLabel(inst.c, fresh);
+
+        // To support DebugLuauAbortingChecks, CHECK_TAG with VmReg has to be handled
+        RegisterA64 tag = inst.a.kind == IrOpKind::VmReg ? regs.allocTemp(KindA64::w) : regOp(inst.a);
+
+        if (inst.a.kind == IrOpKind::VmReg)
+            build.ldr(tag, mem(rBase, vmRegOp(inst.a) * sizeof(TValue) + offsetof(TValue, tt)));
+
         if (tagOp(inst.b) == 0)
         {
-            build.cbnz(regOp(inst.a), fail);
+            build.cbnz(tag, fail);
         }
         else
         {
-            build.cmp(regOp(inst.a), tagOp(inst.b));
+            build.cmp(tag, tagOp(inst.b));
             build.b(ConditionA64::NotEqual, fail);
         }
         if (!continueInVm)
@@ -1517,13 +1532,26 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         regs.spill(build, index);
         emitFallback(build, offsetof(NativeContext, executeGETVARARGS), uintOp(inst.a));
         break;
-    case IrCmd::FALLBACK_NEWCLOSURE:
-        LUAU_ASSERT(inst.b.kind == IrOpKind::VmReg);
-        LUAU_ASSERT(inst.c.kind == IrOpKind::Constant);
+    case IrCmd::NEWCLOSURE:
+    {
+        RegisterA64 reg = regOp(inst.b); // note: we need to call regOp before spill so that we don't do redundant reloads
 
-        regs.spill(build, index);
-        emitFallback(build, offsetof(NativeContext, executeNEWCLOSURE), uintOp(inst.a));
+        regs.spill(build, index, {reg});
+        build.mov(x2, reg);
+
+        build.mov(x0, rState);
+        build.mov(w1, uintOp(inst.a));
+
+        build.ldr(x3, mem(rClosure, offsetof(Closure, l.p)));
+        build.ldr(x3, mem(x3, offsetof(Proto, p)));
+        build.ldr(x3, mem(x3, sizeof(Proto*) * uintOp(inst.c)));
+
+        build.ldr(x4, mem(rNativeContext, offsetof(NativeContext, luaF_newLclosure)));
+        build.blr(x4);
+
+        inst.regA64 = regs.takeReg(x0, index);
         break;
+    }
     case IrCmd::FALLBACK_DUPCLOSURE:
         LUAU_ASSERT(inst.b.kind == IrOpKind::VmReg);
         LUAU_ASSERT(inst.c.kind == IrOpKind::VmConst);
@@ -1743,6 +1771,18 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         break;
     }
 
+    case IrCmd::FINDUPVAL:
+    {
+        regs.spill(build, index);
+        build.mov(x0, rState);
+        build.add(x1, rBase, uint16_t(vmRegOp(inst.a) * sizeof(TValue)));
+        build.ldr(x2, mem(rNativeContext, offsetof(NativeContext, luaF_findupval)));
+        build.blr(x2);
+
+        inst.regA64 = regs.takeReg(x0, index);
+        break;
+    }
+
         // To handle unsupported instructions, add "case IrCmd::OP" and make sure to set error = true!
     }
 

CodeGen/src/IrLoweringX64.cpp

@@ -186,14 +186,40 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         build.add(inst.regX64, tmp.reg);
         break;
     };
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
+    {
+        inst.regX64 = regs.allocRegOrReuse(SizeX64::qword, index, {inst.a});
+
+        if (inst.a.kind == IrOpKind::Undef)
+        {
+            build.mov(inst.regX64, sClosure);
+        }
+        else
+        {
+            RegisterX64 cl = regOp(inst.a);
+            if (inst.regX64 != cl)
+                build.mov(inst.regX64, cl);
+        }
+
+        build.add(inst.regX64, offsetof(Closure, l.uprefs) + sizeof(TValue) * vmUpvalueOp(inst.b));
+        break;
+    }
     case IrCmd::STORE_TAG:
         if (inst.b.kind == IrOpKind::Constant)
-            build.mov(luauRegTag(vmRegOp(inst.a)), tagOp(inst.b));
+        {
+            if (inst.a.kind == IrOpKind::Inst)
+                build.mov(dword[regOp(inst.a) + offsetof(TValue, tt)], tagOp(inst.b));
+            else
+                build.mov(luauRegTag(vmRegOp(inst.a)), tagOp(inst.b));
+        }
         else
             LUAU_ASSERT(!"Unsupported instruction form");
         break;
     case IrCmd::STORE_POINTER:
-        build.mov(luauRegValue(vmRegOp(inst.a)), regOp(inst.b));
+        if (inst.a.kind == IrOpKind::Inst)
+            build.mov(qword[regOp(inst.a) + offsetof(TValue, value)], regOp(inst.b));
+        else
+            build.mov(luauRegValue(vmRegOp(inst.a)), regOp(inst.b));
         break;
     case IrCmd::STORE_DOUBLE:
         if (inst.b.kind == IrOpKind::Constant)
@@ -1207,12 +1233,25 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
 
         emitFallback(regs, build, offsetof(NativeContext, executeGETVARARGS), uintOp(inst.a));
         break;
-    case IrCmd::FALLBACK_NEWCLOSURE:
-        LUAU_ASSERT(inst.b.kind == IrOpKind::VmReg);
-        LUAU_ASSERT(inst.c.kind == IrOpKind::Constant);
+    case IrCmd::NEWCLOSURE:
+    {
+        ScopedRegX64 tmp2{regs, SizeX64::qword};
+        build.mov(tmp2.reg, sClosure);
+        build.mov(tmp2.reg, qword[tmp2.reg + offsetof(Closure, l.p)]);
+        build.mov(tmp2.reg, qword[tmp2.reg + offsetof(Proto, p)]);
+        build.mov(tmp2.reg, qword[tmp2.reg + sizeof(Proto*) * uintOp(inst.c)]);
 
-        emitFallback(regs, build, offsetof(NativeContext, executeNEWCLOSURE), uintOp(inst.a));
+        IrCallWrapperX64 callWrap(regs, build, index);
+        callWrap.addArgument(SizeX64::qword, rState);
+        callWrap.addArgument(SizeX64::dword, uintOp(inst.a), inst.a);
+        callWrap.addArgument(SizeX64::qword, regOp(inst.b), inst.b);
+        callWrap.addArgument(SizeX64::qword, tmp2);
+
+        callWrap.call(qword[rNativeContext + offsetof(NativeContext, luaF_newLclosure)]);
+
+        inst.regX64 = regs.takeReg(rax, index);
         break;
+    }
     case IrCmd::FALLBACK_DUPCLOSURE:
         LUAU_ASSERT(inst.b.kind == IrOpKind::VmReg);
         LUAU_ASSERT(inst.c.kind == IrOpKind::VmConst);
@@ -1412,6 +1451,17 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         break;
     }
 
+    case IrCmd::FINDUPVAL:
+    {
+        IrCallWrapperX64 callWrap(regs, build);
+        callWrap.addArgument(SizeX64::qword, rState);
+        callWrap.addArgument(SizeX64::qword, luauRegAddress(vmRegOp(inst.a)));
+        callWrap.call(qword[rNativeContext + offsetof(NativeContext, luaF_findupval)]);
+
+        inst.regX64 = regs.takeReg(rax, index);
+        break;
+    }
+
     // Pseudo instructions
     case IrCmd::NOP:
     case IrCmd::SUBSTITUTE:

CodeGen/src/IrTranslation.cpp

@@ -1213,5 +1213,61 @@ void translateInstOrX(IrBuilder& build, const Instruction* pc, int pcpos, IrOp c
     }
 }
 
+void translateInstNewClosure(IrBuilder& build, const Instruction* pc, int pcpos)
+{
+    LUAU_ASSERT(unsigned(LUAU_INSN_D(*pc)) < unsigned(build.function.proto->sizep));
+
+    int ra = LUAU_INSN_A(*pc);
+    Proto* pv = build.function.proto->p[LUAU_INSN_D(*pc)];
+
+    build.inst(IrCmd::SET_SAVEDPC, build.constUint(pcpos + 1));
+
+    IrOp env = build.inst(IrCmd::LOAD_ENV);
+    IrOp ncl = build.inst(IrCmd::NEWCLOSURE, build.constUint(pv->nups), env, build.constUint(LUAU_INSN_D(*pc)));
+
+    build.inst(IrCmd::STORE_POINTER, build.vmReg(ra), ncl);
+    build.inst(IrCmd::STORE_TAG, build.vmReg(ra), build.constTag(LUA_TFUNCTION));
+
+    for (int ui = 0; ui < pv->nups; ++ui)
+    {
+        Instruction uinsn = pc[ui + 1];
+        LUAU_ASSERT(LUAU_INSN_OP(uinsn) == LOP_CAPTURE);
+
+        IrOp dst = build.inst(IrCmd::GET_CLOSURE_UPVAL_ADDR, ncl, build.vmUpvalue(ui));
+
+        switch (LUAU_INSN_A(uinsn))
+        {
+        case LCT_VAL:
+        {
+            IrOp src = build.inst(IrCmd::LOAD_TVALUE, build.vmReg(LUAU_INSN_B(uinsn)));
+            build.inst(IrCmd::STORE_TVALUE, dst, src);
+            break;
+        }
+
+        case LCT_REF:
+        {
+            IrOp src = build.inst(IrCmd::FINDUPVAL, build.vmReg(LUAU_INSN_B(uinsn)));
+            build.inst(IrCmd::STORE_POINTER, dst, src);
+            build.inst(IrCmd::STORE_TAG, dst, build.constTag(LUA_TUPVAL));
+            break;
+        }
+
+        case LCT_UPVAL:
+        {
+            IrOp src = build.inst(IrCmd::GET_CLOSURE_UPVAL_ADDR, build.undef(), build.vmUpvalue(LUAU_INSN_B(uinsn)));
+            IrOp load = build.inst(IrCmd::LOAD_TVALUE, src);
+            build.inst(IrCmd::STORE_TVALUE, dst, load);
+            break;
+        }
+
+        default:
+            LUAU_ASSERT(!"Unknown upvalue capture type");
+            LUAU_UNREACHABLE(); // improves switch() codegen by eliding opcode bounds checks
+        }
+    }
+
+    build.inst(IrCmd::CHECK_GC);
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/IrTranslation.h

@@ -65,6 +65,7 @@ void translateInstCapture(IrBuilder& build, const Instruction* pc, int pcpos);
 void translateInstNamecall(IrBuilder& build, const Instruction* pc, int pcpos);
 void translateInstAndX(IrBuilder& build, const Instruction* pc, int pcpos, IrOp c);
 void translateInstOrX(IrBuilder& build, const Instruction* pc, int pcpos, IrOp c);
+void translateInstNewClosure(IrBuilder& build, const Instruction* pc, int pcpos);
 
 inline int getOpLength(LuauOpcode op)
 {

CodeGen/src/IrUtils.cpp

@@ -38,6 +38,7 @@ IrValueKind getCmdValueKind(IrCmd cmd)
     case IrCmd::GET_ARR_ADDR:
     case IrCmd::GET_SLOT_NODE_ADDR:
     case IrCmd::GET_HASH_NODE_ADDR:
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
         return IrValueKind::Pointer;
     case IrCmd::STORE_TAG:
     case IrCmd::STORE_POINTER:
@@ -141,7 +142,9 @@ IrValueKind getCmdValueKind(IrCmd cmd)
     case IrCmd::FALLBACK_NAMECALL:
     case IrCmd::FALLBACK_PREPVARARGS:
     case IrCmd::FALLBACK_GETVARARGS:
-    case IrCmd::FALLBACK_NEWCLOSURE:
+        return IrValueKind::None;
+    case IrCmd::NEWCLOSURE:
+        return IrValueKind::Pointer;
     case IrCmd::FALLBACK_DUPCLOSURE:
     case IrCmd::FALLBACK_FORGPREP:
         return IrValueKind::None;
@@ -164,6 +167,8 @@ IrValueKind getCmdValueKind(IrCmd cmd)
     case IrCmd::GET_TYPE:
     case IrCmd::GET_TYPEOF:
         return IrValueKind::Pointer;
+    case IrCmd::FINDUPVAL:
+        return IrValueKind::Pointer;
     }
 
     LUAU_UNREACHABLE();

CodeGen/src/IrValueLocationTracking.cpp

@@ -77,7 +77,6 @@ void IrValueLocationTracking::beforeInstLowering(IrInst& inst)
     case IrCmd::FALLBACK_GETVARARGS:
         invalidateRestoreVmRegs(vmRegOp(inst.b), function.intOp(inst.c));
         break;
-    case IrCmd::FALLBACK_NEWCLOSURE:
     case IrCmd::FALLBACK_DUPCLOSURE:
         invalidateRestoreOp(inst.b);
         break;
@@ -109,6 +108,8 @@ void IrValueLocationTracking::beforeInstLowering(IrInst& inst)
     case IrCmd::FALLBACK_PREPVARARGS:
     case IrCmd::ADJUST_STACK_TO_TOP:
     case IrCmd::GET_TYPEOF:
+    case IrCmd::NEWCLOSURE:
+    case IrCmd::FINDUPVAL:
         break;
 
         // These instrucitons read VmReg only after optimizeMemoryOperandsX64

CodeGen/src/NativeState.cpp

@@ -56,6 +56,8 @@ void initFunctions(NativeState& data)
     data.context.luaC_step = luaC_step;
 
     data.context.luaF_close = luaF_close;
+    data.context.luaF_findupval = luaF_findupval;
+    data.context.luaF_newLclosure = luaF_newLclosure;
 
     data.context.luaT_gettm = luaT_gettm;
     data.context.luaT_objtypenamestr = luaT_objtypenamestr;

CodeGen/src/NativeState.h

@@ -52,6 +52,8 @@ struct NativeContext
     size_t (*luaC_step)(lua_State* L, bool assist) = nullptr;
 
     void (*luaF_close)(lua_State* L, StkId level) = nullptr;
+    UpVal* (*luaF_findupval)(lua_State* L, StkId level) = nullptr;
+    Closure* (*luaF_newLclosure)(lua_State* L, int nelems, Table* e, Proto* p) = nullptr;
 
     const TValue* (*luaT_gettm)(Table* events, TMS event, TString* ename) = nullptr;
     const TString* (*luaT_objtypenamestr)(lua_State* L, const TValue* o) = nullptr;

CodeGen/src/OptimizeConstProp.cpp

@@ -415,6 +415,8 @@ static void handleBuiltinEffects(ConstPropState& state, LuauBuiltinFunction bfid
     case LBF_RAWLEN:
     case LBF_BIT32_EXTRACTK:
     case LBF_GETMETATABLE:
+    case LBF_TONUMBER:
+    case LBF_TOSTRING:
         break;
     case LBF_SETMETATABLE:
         state.invalidateHeap(); // TODO: only knownNoMetatable is affected and we might know which one
@@ -760,6 +762,7 @@ static void constPropInInst(ConstPropState& state, IrBuilder& build, IrFunction&
     case IrCmd::GET_ARR_ADDR:
     case IrCmd::GET_SLOT_NODE_ADDR:
     case IrCmd::GET_HASH_NODE_ADDR:
+    case IrCmd::GET_CLOSURE_UPVAL_ADDR:
         break;
     case IrCmd::ADD_INT:
     case IrCmd::SUB_INT:
@@ -823,6 +826,7 @@ static void constPropInInst(ConstPropState& state, IrBuilder& build, IrFunction&
     case IrCmd::BITXOR_UINT:
     case IrCmd::BITOR_UINT:
     case IrCmd::BITNOT_UINT:
+        break;
     case IrCmd::BITLSHIFT_UINT:
     case IrCmd::BITRSHIFT_UINT:
     case IrCmd::BITARSHIFT_UINT:
@@ -833,6 +837,7 @@ static void constPropInInst(ConstPropState& state, IrBuilder& build, IrFunction&
     case IrCmd::INVOKE_LIBM:
     case IrCmd::GET_TYPE:
     case IrCmd::GET_TYPEOF:
+    case IrCmd::FINDUPVAL:
         break;
 
     case IrCmd::JUMP_CMP_ANY:
@@ -923,8 +928,7 @@ static void constPropInInst(ConstPropState& state, IrBuilder& build, IrFunction&
     case IrCmd::FALLBACK_GETVARARGS:
         state.invalidateRegisterRange(vmRegOp(inst.b), function.intOp(inst.c));
         break;
-    case IrCmd::FALLBACK_NEWCLOSURE:
-        state.invalidate(inst.b);
+    case IrCmd::NEWCLOSURE:
         break;
     case IrCmd::FALLBACK_DUPCLOSURE:
         state.invalidate(inst.b);

Common/include/Luau/Bytecode.h

@@ -44,6 +44,7 @@
 // Version 1: Baseline version for the open-source release. Supported until 0.521.
 // Version 2: Adds Proto::linedefined. Supported until 0.544.
 // Version 3: Adds FORGPREP/JUMPXEQK* and enhances AUX encoding for FORGLOOP. Removes FORGLOOP_NEXT/INEXT and JUMPIFEQK/JUMPIFNOTEQK. Currently supported.
+// Version 4: Adds Proto::flags and typeinfo. Currently supported.
 
 // Bytecode opcode, part of the instruction header
 enum LuauOpcode
@@ -543,6 +544,10 @@ enum LuauBuiltinFunction
     // get/setmetatable
     LBF_GETMETATABLE,
     LBF_SETMETATABLE,
+
+    // tonumber/tostring
+    LBF_TONUMBER,
+    LBF_TOSTRING,
 };
 
 // Capture type, used in LOP_CAPTURE
@@ -552,3 +557,10 @@ enum LuauCaptureType
     LCT_REF,
     LCT_UPVAL,
 };
+
+// Proto flag bitmask, stored in Proto::flags
+enum LuauProtoFlag
+{
+    // used to tag main proto for modules with --!native
+    LPF_NATIVE_MODULE = 1 << 0,
+};

Compiler/src/Builtins.cpp

@@ -4,6 +4,9 @@
 #include "Luau/Bytecode.h"
 #include "Luau/Compiler.h"
 
+LUAU_FASTFLAGVARIABLE(LuauCompileBuiltinTonumber, false)
+LUAU_FASTFLAGVARIABLE(LuauCompileBuiltinTostring, false)
+
 namespace Luau
 {
 namespace Compile
@@ -69,6 +72,11 @@ static int getBuiltinFunctionId(const Builtin& builtin, const CompileOptions& op
     if (builtin.isGlobal("setmetatable"))
         return LBF_SETMETATABLE;
 
+    if (FFlag::LuauCompileBuiltinTonumber && builtin.isGlobal("tonumber"))
+        return LBF_TONUMBER;
+    if (FFlag::LuauCompileBuiltinTostring && builtin.isGlobal("tostring"))
+        return LBF_TOSTRING;
+
     if (builtin.object == "math")
     {
         if (builtin.method == "abs")
@@ -257,10 +265,10 @@ BuiltinInfo getBuiltinInfo(int bfid)
     case LBF_MATH_ABS:
     case LBF_MATH_ACOS:
     case LBF_MATH_ASIN:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_ATAN2:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_ATAN:
     case LBF_MATH_CEIL:
@@ -269,19 +277,19 @@ BuiltinInfo getBuiltinInfo(int bfid)
     case LBF_MATH_DEG:
     case LBF_MATH_EXP:
     case LBF_MATH_FLOOR:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_FMOD:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_FREXP:
-        return {1, 2};
+        return {1, 2, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_LDEXP:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_LOG10:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_LOG:
         return {-1, 1}; // 1 or 2 parameters
@@ -291,10 +299,10 @@ BuiltinInfo getBuiltinInfo(int bfid)
         return {-1, 1}; // variadic
 
     case LBF_MATH_MODF:
-        return {1, 2};
+        return {1, 2, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_POW:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_RAD:
     case LBF_MATH_SINH:
@@ -302,16 +310,16 @@ BuiltinInfo getBuiltinInfo(int bfid)
     case LBF_MATH_SQRT:
     case LBF_MATH_TANH:
     case LBF_MATH_TAN:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_BIT32_ARSHIFT:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_BIT32_BAND:
         return {-1, 1}; // variadic
 
     case LBF_BIT32_BNOT:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_BIT32_BOR:
     case LBF_BIT32_BXOR:
@@ -323,14 +331,14 @@ BuiltinInfo getBuiltinInfo(int bfid)
 
     case LBF_BIT32_LROTATE:
     case LBF_BIT32_LSHIFT:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_BIT32_REPLACE:
         return {-1, 1}; // 3 or 4 parameters
 
     case LBF_BIT32_RROTATE:
     case LBF_BIT32_RSHIFT:
-        return {2, 1};
+        return {2, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_TYPE:
         return {1, 1};
@@ -342,7 +350,7 @@ BuiltinInfo getBuiltinInfo(int bfid)
         return {-1, 1}; // variadic
 
     case LBF_STRING_LEN:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_TYPEOF:
         return {1, 1};
@@ -351,11 +359,11 @@ BuiltinInfo getBuiltinInfo(int bfid)
         return {-1, 1}; // 2 or 3 parameters
 
     case LBF_MATH_CLAMP:
-        return {3, 1};
+        return {3, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_MATH_SIGN:
     case LBF_MATH_ROUND:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_RAWSET:
         return {3, 1};
@@ -375,22 +383,28 @@ BuiltinInfo getBuiltinInfo(int bfid)
 
     case LBF_BIT32_COUNTLZ:
     case LBF_BIT32_COUNTRZ:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_SELECT_VARARG:
         return {-1, -1}; // variadic
 
     case LBF_RAWLEN:
-        return {1, 1};
+        return {1, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_BIT32_EXTRACTK:
-        return {3, 1};
+        return {3, 1, BuiltinInfo::Flag_NoneSafe};
 
     case LBF_GETMETATABLE:
         return {1, 1};
 
     case LBF_SETMETATABLE:
         return {2, 1};
+
+    case LBF_TONUMBER:
+        return {-1, 1}; // 1 or 2 parameters
+
+    case LBF_TOSTRING:
+        return {1, 1};
     };
 
     LUAU_UNREACHABLE();

Compiler/src/Builtins.h

@@ -41,8 +41,17 @@ void analyzeBuiltins(DenseHashMap<AstExprCall*, int>& result, const DenseHashMap
 
 struct BuiltinInfo
 {
+    enum Flags
+    {
+        // none-safe builtins are builtins that have the same behavior for arguments that are nil or none
+        // this allows the compiler to compile calls to builtins more efficiently in certain cases
+        // for example, math.abs(x()) may compile x() as if it returns one value; if it returns no values, abs() will get nil instead of none
+        Flag_NoneSafe = 1 << 0,
+    };
+
     int params;
     int results;
+    unsigned int flags;
 };
 
 BuiltinInfo getBuiltinInfo(int bfid);

Compiler/src/Compiler.cpp

@@ -27,6 +27,9 @@ LUAU_FASTINTVARIABLE(LuauCompileInlineThresholdMaxBoost, 300)
 LUAU_FASTINTVARIABLE(LuauCompileInlineDepth, 5)
 
 LUAU_FASTFLAGVARIABLE(LuauCompileFunctionType, false)
+LUAU_FASTFLAGVARIABLE(LuauCompileNativeComment, false)
+
+LUAU_FASTFLAGVARIABLE(LuauCompileFixBuiltinArity, false)
 
 namespace Luau
 {
@@ -187,7 +190,7 @@ struct Compiler
             return node->as<AstExprFunction>();
     }
 
-    uint32_t compileFunction(AstExprFunction* func)
+    uint32_t compileFunction(AstExprFunction* func, uint8_t protoflags)
     {
         LUAU_TIMETRACE_SCOPE("Compiler::compileFunction", "Compiler");
 
@@ -262,7 +265,7 @@ struct Compiler
         if (bytecode.getInstructionCount() > kMaxInstructionCount)
             CompileError::raise(func->location, "Exceeded function instruction limit; split the function into parts to compile");
 
-        bytecode.endFunction(uint8_t(stackSize), uint8_t(upvals.size()));
+        bytecode.endFunction(uint8_t(stackSize), uint8_t(upvals.size()), protoflags);
 
         Function& f = functions[func];
         f.id = fid;
@@ -792,8 +795,19 @@ struct Compiler
         {
             if (!isExprMultRet(expr->args.data[expr->args.size - 1]))
                 return compileExprFastcallN(expr, target, targetCount, targetTop, multRet, regs, bfid);
-            else if (options.optimizationLevel >= 2 && int(expr->args.size) == getBuiltinInfo(bfid).params)
-                return compileExprFastcallN(expr, target, targetCount, targetTop, multRet, regs, bfid);
+            else if (options.optimizationLevel >= 2)
+            {
+                if (FFlag::LuauCompileFixBuiltinArity)
+                {
+                    // when a builtin is none-safe with matching arity, even if the last expression returns 0 or >1 arguments,
+                    // we can rely on the behavior of the function being the same (none-safe means nil and none are interchangeable)
+                    BuiltinInfo info = getBuiltinInfo(bfid);
+                    if (int(expr->args.size) == info.params && (info.flags & BuiltinInfo::Flag_NoneSafe) != 0)
+                        return compileExprFastcallN(expr, target, targetCount, targetTop, multRet, regs, bfid);
+                }
+                else if (int(expr->args.size) == getBuiltinInfo(bfid).params)
+                    return compileExprFastcallN(expr, target, targetCount, targetTop, multRet, regs, bfid);
+            }
         }
 
         if (expr->self)
@@ -3147,7 +3161,7 @@ struct Compiler
             }
         }
 
-        // compute expressions with side effects for lulz
+        // compute expressions with side effects
         for (size_t i = stat->vars.size; i < stat->values.size; ++i)
         {
             RegScope rsi(this);
@@ -3834,11 +3848,20 @@ void compileOrThrow(BytecodeBuilder& bytecode, const ParseResult& parseResult, c
     LUAU_ASSERT(parseResult.errors.empty());
 
     CompileOptions options = inputOptions;
+    uint8_t mainFlags = 0;
 
     for (const HotComment& hc : parseResult.hotcomments)
+    {
         if (hc.header && hc.content.compare(0, 9, "optimize ") == 0)
             options.optimizationLevel = std::max(0, std::min(2, atoi(hc.content.c_str() + 9)));
 
+        if (FFlag::LuauCompileNativeComment && hc.header && hc.content == "native")
+        {
+            mainFlags |= LPF_NATIVE_MODULE;
+            options.optimizationLevel = 2; // note: this might be removed in the future in favor of --!optimize
+        }
+    }
+
     AstStatBlock* root = parseResult.root;
 
     Compiler compiler(bytecode, options);
@@ -3884,12 +3907,12 @@ void compileOrThrow(BytecodeBuilder& bytecode, const ParseResult& parseResult, c
     root->visit(&functionVisitor);
 
     for (AstExprFunction* expr : functions)
-        compiler.compileFunction(expr);
+        compiler.compileFunction(expr, 0);
 
     AstExprFunction main(root->location, /*generics= */ AstArray<AstGenericType>(), /*genericPacks= */ AstArray<AstGenericTypePack>(),
         /* self= */ nullptr, AstArray<AstLocal*>(), /* vararg= */ true, /* varargLocation= */ Luau::Location(), root, /* functionDepth= */ 0,
         /* debugname= */ AstName());
-    uint32_t mainid = compiler.compileFunction(&main);
+    uint32_t mainid = compiler.compileFunction(&main, mainFlags);
 
     const Compiler::Function* mainf = compiler.functions.find(&main);
     LUAU_ASSERT(mainf && mainf->upvals.empty());

Compiler/src/CostModel.cpp

@@ -6,6 +6,8 @@
 
 #include <limits.h>
 
+LUAU_FASTFLAGVARIABLE(LuauAssignmentHasCost, false)
+
 namespace Luau
 {
 namespace Compile
@@ -302,12 +304,14 @@ struct CostVisitor : AstVisitor
         return false;
     }
 
-    bool visit(AstStat* node) override
+    bool visit(AstStatIf* node) override
     {
-        if (node->is<AstStatIf>())
+        // unconditional 'else' may require a jump after the 'if' body
+        // note: this ignores cases when 'then' always terminates and also assumes comparison requires an extra instruction which may be false
+        if (!FFlag::LuauAssignmentHasCost)
             result += 2;
-        else if (node->is<AstStatBreak>() || node->is<AstStatContinue>())
-            result += 1;
+        else
+            result += 1 + (node->elsebody && !node->elsebody->is<AstStatIf>());
 
         return true;
     }
@@ -333,7 +337,21 @@ struct CostVisitor : AstVisitor
         for (size_t i = 0; i < node->vars.size; ++i)
             assign(node->vars.data[i]);
 
-        return true;
+        if (!FFlag::LuauAssignmentHasCost)
+            return true;
+
+        for (size_t i = 0; i < node->vars.size || i < node->values.size; ++i)
+        {
+            Cost ac;
+            if (i < node->vars.size)
+                ac += model(node->vars.data[i]);
+            if (i < node->values.size)
+                ac += model(node->values.data[i]);
+            // local->local or constant->local assignment is not free
+            result += ac.model == 0 ? Cost(1) : ac;
+        }
+
+        return false;
     }
 
     bool visit(AstStatCompoundAssign* node) override
@@ -345,6 +363,20 @@ struct CostVisitor : AstVisitor
 
         return true;
     }
+
+    bool visit(AstStatBreak* node) override
+    {
+        result += 1;
+
+        return false;
+    }
+
+    bool visit(AstStatContinue* node) override
+    {
+        result += 1;
+
+        return false;
+    }
 };
 
 uint64_t modelCost(AstNode* root, AstLocal* const* vars, size_t varCount, const DenseHashMap<AstExprCall*, int>& builtins)

Sources.cmake

@@ -186,6 +186,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/include/Luau/TypeArena.h
     Analysis/include/Luau/TypeAttach.h
     Analysis/include/Luau/TypeChecker2.h
+    Analysis/include/Luau/TypeCheckLimits.h
     Analysis/include/Luau/TypedAllocator.h
     Analysis/include/Luau/TypeFamily.h
     Analysis/include/Luau/TypeInfer.h

VM/include/luaconf.h

@@ -123,7 +123,7 @@
 
 // enables callbacks to redirect code execution from Luau VM to a custom implementation
 #ifndef LUA_CUSTOM_EXECUTION
-#define LUA_CUSTOM_EXECUTION 0
+#define LUA_CUSTOM_EXECUTION 1
 #endif
 
 // }==================================================================

VM/src/laux.cpp

@@ -336,7 +336,7 @@ const char* luaL_findtable(lua_State* L, int idx, const char* fname, int szhint)
 const char* luaL_typename(lua_State* L, int idx)
 {
     const TValue* obj = luaA_toobject(L, idx);
-    return luaT_objtypename(L, obj);
+    return obj ? luaT_objtypename(L, obj) : "no value";
 }
 
 /*

VM/src/lbuiltins.cpp

@@ -23,6 +23,8 @@
 #endif
 #endif
 
+LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauFastcallGC, false)
+
 // luauF functions implement FASTCALL instruction that performs a direct execution of some builtin functions from the VM
 // The rule of thumb is that FASTCALL functions can not call user code, yield, fail, or reallocate stack.
 // If types of the arguments mismatch, luauF_* needs to return -1 and the execution will fall back to the usual call path
@@ -830,6 +832,8 @@ static int luauF_char(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 
     if (nparams < int(sizeof(buffer)) && nresults <= 1)
     {
+        if (DFFlag::LuauFastcallGC && luaC_needsGC(L))
+            return -1; // we can't call luaC_checkGC so fall back to C implementation
 
         if (nparams >= 1)
         {
@@ -900,6 +904,9 @@ static int luauF_sub(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
         int i = int(nvalue(args));
         int j = int(nvalue(args + 1));
 
+        if (DFFlag::LuauFastcallGC && luaC_needsGC(L))
+            return -1; // we can't call luaC_checkGC so fall back to C implementation
+
         if (i >= 1 && j >= i && unsigned(j - 1) < unsigned(ts->len))
         {
             setsvalue(L, res, luaS_newlstr(L, getstr(ts) + (i - 1), j - i + 1));
@@ -1247,6 +1254,73 @@ static int luauF_setmetatable(lua_State* L, StkId res, TValue* arg0, int nresult
     return -1;
 }
 
+static int luauF_tonumber(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
+{
+    if (nparams == 1 && nresults <= 1)
+    {
+        double num;
+
+        if (ttisnumber(arg0))
+        {
+            setnvalue(res, nvalue(arg0));
+            return 1;
+        }
+        else if (ttisstring(arg0) && luaO_str2d(svalue(arg0), &num))
+        {
+            setnvalue(res, num);
+            return 1;
+        }
+        else
+        {
+            setnilvalue(res);
+            return 1;
+        }
+    }
+
+    return -1;
+}
+
+static int luauF_tostring(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
+{
+    if (nparams >= 1 && nresults <= 1)
+    {
+        switch (ttype(arg0))
+        {
+        case LUA_TNIL:
+        {
+            TString* s = L->global->ttname[LUA_TNIL];
+            setsvalue(L, res, s);
+            return 1;
+        }
+        case LUA_TBOOLEAN:
+        {
+            TString* s = bvalue(arg0) ? luaS_newliteral(L, "true") : luaS_newliteral(L, "false");
+            setsvalue(L, res, s);
+            return 1;
+        }
+        case LUA_TNUMBER:
+        {
+            if (DFFlag::LuauFastcallGC && luaC_needsGC(L))
+                return -1; // we can't call luaC_checkGC so fall back to C implementation
+
+            char s[LUAI_MAXNUM2STR];
+            char* e = luai_num2str(s, nvalue(arg0));
+            setsvalue(L, res, luaS_newlstr(L, s, e - s));
+            return 1;
+        }
+        case LUA_TSTRING:
+        {
+            setsvalue(L, res, tsvalue(arg0));
+            return 1;
+        }
+        }
+
+        // fall back to generic C implementation
+    }
+
+    return -1;
+}
+
 static int luauF_missing(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     return -1;
@@ -1411,6 +1485,9 @@ const luau_FastFunction luauF_table[256] = {
     luauF_getmetatable,
     luauF_setmetatable,
 
+    luauF_tonumber,
+    luauF_tostring,
+
 // When adding builtins, add them above this line; what follows is 64 "dummy" entries with luauF_missing fallback.
 // This is important so that older versions of the runtime that don't support newer builtins automatically fall back via luauF_missing.
 // Given the builtin addition velocity this should always provide a larger compatibility window than bytecode versions suggest.

VM/src/lfunc.cpp

@@ -36,6 +36,7 @@ Proto* luaF_newproto(lua_State* L)
     f->execdata = NULL;
     f->exectarget = 0;
     f->typeinfo = NULL;
+    f->userdata = NULL;
 
     return f;
 }

VM/src/lgc.h

@@ -73,10 +73,12 @@
 
 #define luaC_white(g) cast_to(uint8_t, ((g)->currentwhite) & WHITEBITS)
 
+#define luaC_needsGC(L) (L->global->totalbytes >= L->global->GCthreshold)
+
 #define luaC_checkGC(L) \
     { \
         condhardstacktests(luaD_reallocstack(L, L->stacksize - EXTRA_STACK)); \
-        if (L->global->totalbytes >= L->global->GCthreshold) \
+        if (luaC_needsGC(L)) \
         { \
             condhardmemtests(luaC_validate(L), 1); \
             luaC_step(L, true); \

VM/src/lmathlib.cpp

@@ -7,6 +7,8 @@
 #include <math.h>
 #include <time.h>
 
+LUAU_FASTFLAGVARIABLE(LuauFasterNoise, false)
+
 #undef PI
 #define PI (3.14159265358979323846)
 #define RADIANS_PER_DEGREE (PI / 180.0)
@@ -275,6 +277,7 @@ static int math_randomseed(lua_State* L)
     return 0;
 }
 
+// TODO: Delete with LuauFasterNoise
 static const unsigned char kPerlin[512] = {151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99,
     37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174,
     20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41,
@@ -295,18 +298,32 @@ static const unsigned char kPerlin[512] = {151, 160, 137, 91, 90, 15, 131, 13, 2
     106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61,
     156, 180};
 
-static float fade(float t)
+static const unsigned char kPerlinHash[257] = {151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99,
+    37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174,
+    20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41,
+    55, 46, 245, 40, 244, 102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86,
+    164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17,
+    182, 189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98, 108, 110,
+    79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14,
+    239, 107, 49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24,
+    72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180, 151};
+
+const float kPerlinGrad[16][3] = {{1, 1, 0}, {-1, 1, 0}, {1, -1, 0}, {-1, -1, 0}, {1, 0, 1}, {-1, 0, 1}, {1, 0, -1}, {-1, 0, -1}, {0, 1, 1},
+    {0, -1, 1}, {0, 1, -1}, {0, -1, -1}, {1, 1, 0}, {0, -1, 1}, {-1, 1, 0}, {0, -1, -1}};
+
+static float perlin_fade(float t)
 {
     return t * t * t * (t * (t * 6 - 15) + 10);
 }
 
-static float math_lerp(float t, float a, float b)
+static float perlin_lerp(float t, float a, float b)
 {
     return a + t * (b - a);
 }
 
 static float grad(unsigned char hash, float x, float y, float z)
 {
+    LUAU_ASSERT(!FFlag::LuauFasterNoise);
     unsigned char h = hash & 15;
     float u = (h < 8) ? x : y;
     float v = (h < 4) ? y : (h == 12 || h == 14) ? x : z;
@@ -314,8 +331,15 @@ static float grad(unsigned char hash, float x, float y, float z)
     return (h & 1 ? -u : u) + (h & 2 ? -v : v);
 }
 
-static float perlin(float x, float y, float z)
+static float perlin_grad(int hash, float x, float y, float z)
 {
+    const float* g = kPerlinGrad[hash & 15];
+    return g[0] * x + g[1] * y + g[2] * z;
+}
+
+static float perlin_dep(float x, float y, float z)
+{
+    LUAU_ASSERT(!FFlag::LuauFasterNoise);
     float xflr = floorf(x);
     float yflr = floorf(y);
     float zflr = floorf(z);
@@ -328,9 +352,9 @@ static float perlin(float x, float y, float z)
     float yf = y - yflr;
     float zf = z - zflr;
 
-    float u = fade(xf);
-    float v = fade(yf);
-    float w = fade(zf);
+    float u = perlin_fade(xf);
+    float v = perlin_fade(yf);
+    float w = perlin_fade(zf);
 
     const unsigned char* p = kPerlin;
 
@@ -342,24 +366,79 @@ static float perlin(float x, float y, float z)
     int ba = p[b] + zi;
     int bb = p[b + 1] + zi;
 
-    return math_lerp(w,
-        math_lerp(v, math_lerp(u, grad(p[aa], xf, yf, zf), grad(p[ba], xf - 1, yf, zf)),
-            math_lerp(u, grad(p[ab], xf, yf - 1, zf), grad(p[bb], xf - 1, yf - 1, zf))),
-        math_lerp(v, math_lerp(u, grad(p[aa + 1], xf, yf, zf - 1), grad(p[ba + 1], xf - 1, yf, zf - 1)),
-            math_lerp(u, grad(p[ab + 1], xf, yf - 1, zf - 1), grad(p[bb + 1], xf - 1, yf - 1, zf - 1))));
+    return perlin_lerp(w,
+        perlin_lerp(v, perlin_lerp(u, grad(p[aa], xf, yf, zf), grad(p[ba], xf - 1, yf, zf)),
+            perlin_lerp(u, grad(p[ab], xf, yf - 1, zf), grad(p[bb], xf - 1, yf - 1, zf))),
+        perlin_lerp(v, perlin_lerp(u, grad(p[aa + 1], xf, yf, zf - 1), grad(p[ba + 1], xf - 1, yf, zf - 1)),
+            perlin_lerp(u, grad(p[ab + 1], xf, yf - 1, zf - 1), grad(p[bb + 1], xf - 1, yf - 1, zf - 1))));
+}
+
+static float perlin(float x, float y, float z)
+{
+    LUAU_ASSERT(FFlag::LuauFasterNoise);
+    float xflr = floorf(x);
+    float yflr = floorf(y);
+    float zflr = floorf(z);
+
+    int xi = int(xflr) & 255;
+    int yi = int(yflr) & 255;
+    int zi = int(zflr) & 255;
+
+    float xf = x - xflr;
+    float yf = y - yflr;
+    float zf = z - zflr;
+
+    float u = perlin_fade(xf);
+    float v = perlin_fade(yf);
+    float w = perlin_fade(zf);
+
+    const unsigned char* p = kPerlinHash;
+
+    int a = (p[xi] + yi) & 255;
+    int aa = (p[a] + zi) & 255;
+    int ab = (p[a + 1] + zi) & 255;
+
+    int b = (p[xi + 1] + yi) & 255;
+    int ba = (p[b] + zi) & 255;
+    int bb = (p[b + 1] + zi) & 255;
+
+    float la = perlin_lerp(u, perlin_grad(p[aa], xf, yf, zf), perlin_grad(p[ba], xf - 1, yf, zf));
+    float lb = perlin_lerp(u, perlin_grad(p[ab], xf, yf - 1, zf), perlin_grad(p[bb], xf - 1, yf - 1, zf));
+    float la1 = perlin_lerp(u, perlin_grad(p[aa + 1], xf, yf, zf - 1), perlin_grad(p[ba + 1], xf - 1, yf, zf - 1));
+    float lb1 = perlin_lerp(u, perlin_grad(p[ab + 1], xf, yf - 1, zf - 1), perlin_grad(p[bb + 1], xf - 1, yf - 1, zf - 1));
+
+    return perlin_lerp(w, perlin_lerp(v, la, lb), perlin_lerp(v, la1, lb1));
 }
 
 static int math_noise(lua_State* L)
 {
-    double x = luaL_checknumber(L, 1);
-    double y = luaL_optnumber(L, 2, 0.0);
-    double z = luaL_optnumber(L, 3, 0.0);
+    if (FFlag::LuauFasterNoise)
+    {
+        int nx, ny, nz;
+        double x = lua_tonumberx(L, 1, &nx);
+        double y = lua_tonumberx(L, 2, &ny);
+        double z = lua_tonumberx(L, 3, &nz);
 
-    double r = perlin((float)x, (float)y, (float)z);
+        luaL_argexpected(L, nx, 1, "number");
+        luaL_argexpected(L, ny || lua_isnoneornil(L, 2), 2, "number");
+        luaL_argexpected(L, nz || lua_isnoneornil(L, 3), 3, "number");
 
-    lua_pushnumber(L, r);
+        double r = perlin((float)x, (float)y, (float)z);
 
-    return 1;
+        lua_pushnumber(L, r);
+        return 1;
+    }
+    else
+    {
+        double x = luaL_checknumber(L, 1);
+        double y = luaL_optnumber(L, 2, 0.0);
+        double z = luaL_optnumber(L, 3, 0.0);
+
+        double r = perlin_dep((float)x, (float)y, (float)z);
+
+        lua_pushnumber(L, r);
+        return 1;
+    }
 }
 
 static int math_clamp(lua_State* L)

VM/src/lobject.h

@@ -290,6 +290,8 @@ typedef struct Proto
 
     uint8_t* typeinfo;
 
+    void* userdata;
+
     GCObject* gclist;
 
 

VM/src/ltablib.cpp

@@ -10,6 +10,8 @@
 #include "ldebug.h"
 #include "lvm.h"
 
+LUAU_FASTFLAGVARIABLE(LuauFasterTableConcat, false)
+
 static int foreachi(lua_State* L)
 {
     luaL_checktype(L, 1, LUA_TTABLE);
@@ -219,8 +221,8 @@ static int tmove(lua_State* L)
 
 static void addfield(lua_State* L, luaL_Buffer* b, int i)
 {
-    lua_rawgeti(L, 1, i);
-    if (!lua_isstring(L, -1))
+    int tt = lua_rawgeti(L, 1, i);
+    if (FFlag::LuauFasterTableConcat ? (tt != LUA_TSTRING && tt != LUA_TNUMBER) : !lua_isstring(L, -1))
         luaL_error(L, "invalid value (%s) at index %d in table for 'concat'", luaL_typename(L, -1), i);
     luaL_addvalue(b);
 }

VM/src/lvmexecute.cpp

@@ -131,6 +131,9 @@
     goto dispatchContinue
 #endif
 
+// Does VM support native execution via ExecutionCallbacks? We mostly assume it does but keep the define to make it easy to quantify the cost.
+#define VM_HAS_NATIVE LUA_CUSTOM_EXECUTION
+
 LUAU_NOINLINE void luau_callhook(lua_State* L, lua_Hook hook, void* userdata)
 {
     ptrdiff_t base = savestack(L, L->base);
@@ -207,7 +210,7 @@ static void luau_execute(lua_State* L)
     LUAU_ASSERT(L->isactive);
     LUAU_ASSERT(!isblack(obj2gco(L))); // we don't use luaC_threadbarrier because active threads never turn black
 
-#if LUA_CUSTOM_EXECUTION
+#if VM_HAS_NATIVE
     if ((L->ci->flags & LUA_CALLINFO_NATIVE) && !SingleStep)
     {
         Proto* p = clvalue(L->ci->func)->l.p;
@@ -1036,7 +1039,7 @@ reentry:
                 Closure* nextcl = clvalue(cip->func);
                 Proto* nextproto = nextcl->l.p;
 
-#if LUA_CUSTOM_EXECUTION
+#if VM_HAS_NATIVE
                 if (LUAU_UNLIKELY((cip->flags & LUA_CALLINFO_NATIVE) && !SingleStep))
                 {
                     if (L->global->ecb.enter(L, nextproto) == 1)
@@ -2371,7 +2374,7 @@ reentry:
                 ci->flags = LUA_CALLINFO_NATIVE;
                 ci->savedpc = p->code;
 
-#if LUA_CUSTOM_EXECUTION
+#if VM_HAS_NATIVE
                 if (L->global->ecb.enter(L, p) == 1)
                     goto reentry;
                 else
@@ -2890,7 +2893,7 @@ int luau_precall(lua_State* L, StkId func, int nresults)
 
         ci->savedpc = p->code;
 
-#if LUA_CUSTOM_EXECUTION
+#if VM_HAS_NATIVE
         if (p->execdata)
             ci->flags = LUA_CALLINFO_NATIVE;
 #endif

bench/micro_tests/test_ToNumberString.lua

@@ -0,0 +1,22 @@
+local bench = script and require(script.Parent.bench_support) or require("bench_support")
+
+bench.runCode(function()
+    for j=1,1e6 do
+        tonumber("42")
+        tonumber(42)
+    end
+end, "tonumber")
+
+bench.runCode(function()
+    for j=1,1e6 do
+        tostring(nil)
+        tostring("test")
+        tostring(42)
+    end
+end, "tostring")
+
+bench.runCode(function()
+    for j=1,1e6 do
+        tostring(j)
+    end
+end, "tostring-gc")

tests/Autocomplete.test.cpp

@@ -15,6 +15,7 @@
 
 LUAU_FASTFLAG(LuauTraceTypesInNonstrictMode2)
 LUAU_FASTFLAG(LuauSetMetatableDoesNotTimeTravel)
+LUAU_FASTFLAG(LuauAutocompleteLastTypecheck)
 
 using namespace Luau;
 
@@ -33,14 +34,40 @@ struct ACFixtureImpl : BaseType
 
     AutocompleteResult autocomplete(unsigned row, unsigned column)
     {
+        if (FFlag::LuauAutocompleteLastTypecheck)
+        {
+            FrontendOptions opts;
+            opts.forAutocomplete = true;
+            this->frontend.check("MainModule", opts);
+        }
+
         return Luau::autocomplete(this->frontend, "MainModule", Position{row, column}, nullCallback);
     }
 
     AutocompleteResult autocomplete(char marker, StringCompletionCallback callback = nullCallback)
     {
+        if (FFlag::LuauAutocompleteLastTypecheck)
+        {
+            FrontendOptions opts;
+            opts.forAutocomplete = true;
+            this->frontend.check("MainModule", opts);
+        }
+
         return Luau::autocomplete(this->frontend, "MainModule", getPosition(marker), callback);
     }
 
+    AutocompleteResult autocomplete(const ModuleName& name, Position pos, StringCompletionCallback callback = nullCallback)
+    {
+        if (FFlag::LuauAutocompleteLastTypecheck)
+        {
+            FrontendOptions opts;
+            opts.forAutocomplete = true;
+            this->frontend.check(name, opts);
+        }
+
+        return Luau::autocomplete(this->frontend, name, pos, callback);
+    }
+
     CheckResult check(const std::string& source)
     {
         markerPosition.clear();
@@ -99,7 +126,7 @@ struct ACFixtureImpl : BaseType
         LUAU_ASSERT(i != markerPosition.end());
         return i->second;
     }
-
+    ScopedFastFlag flag{"LuauAutocompleteHideSelfArg", true};
     // Maps a marker character (0-9 inclusive) to a position in the source code.
     std::map<char, Position> markerPosition;
 };
@@ -1319,7 +1346,7 @@ local a: aa
 
     frontend.check("Module/B");
 
-    auto ac = Luau::autocomplete(frontend, "Module/B", Position{2, 11}, nullCallback);
+    auto ac = autocomplete("Module/B", Position{2, 11});
 
     CHECK(ac.entryMap.count("aaa"));
     CHECK_EQ(ac.context, AutocompleteContext::Type);
@@ -1342,7 +1369,7 @@ local a: aaa.
 
     frontend.check("Module/B");
 
-    auto ac = Luau::autocomplete(frontend, "Module/B", Position{2, 13}, nullCallback);
+    auto ac = autocomplete("Module/B", Position{2, 13});
 
     CHECK_EQ(2, ac.entryMap.size());
     CHECK(ac.entryMap.count("A"));
@@ -1999,7 +2026,7 @@ ex.a(function(x:
 
     frontend.check("Module/B");
 
-    auto ac = Luau::autocomplete(frontend, "Module/B", Position{2, 16}, nullCallback);
+    auto ac = autocomplete("Module/B", Position{2, 16});
 
     CHECK(!ac.entryMap.count("done"));
 
@@ -2010,7 +2037,7 @@ ex.b(function(x:
 
     frontend.check("Module/C");
 
-    ac = Luau::autocomplete(frontend, "Module/C", Position{2, 16}, nullCallback);
+    ac = autocomplete("Module/C", Position{2, 16});
 
     CHECK(!ac.entryMap.count("(done) -> number"));
 }
@@ -2033,7 +2060,7 @@ ex.a(function(x:
 
     frontend.check("Module/B");
 
-    auto ac = Luau::autocomplete(frontend, "Module/B", Position{2, 16}, nullCallback);
+    auto ac = autocomplete("Module/B", Position{2, 16});
 
     CHECK(!ac.entryMap.count("done"));
     CHECK(ac.entryMap.count("ex.done"));
@@ -2046,7 +2073,7 @@ ex.b(function(x:
 
     frontend.check("Module/C");
 
-    ac = Luau::autocomplete(frontend, "Module/C", Position{2, 16}, nullCallback);
+    ac = autocomplete("Module/C", Position{2, 16});
 
     CHECK(!ac.entryMap.count("(done) -> number"));
     CHECK(ac.entryMap.count("(ex.done) -> number"));
@@ -2360,7 +2387,7 @@ local a: aaa.do
 
     frontend.check("Module/B");
 
-    auto ac = Luau::autocomplete(frontend, "Module/B", Position{2, 15}, nullCallback);
+    auto ac = autocomplete("Module/B", Position{2, 15});
 
     CHECK_EQ(2, ac.entryMap.size());
     CHECK(ac.entryMap.count("done"));
@@ -2372,7 +2399,7 @@ TEST_CASE_FIXTURE(ACFixture, "comments")
 {
     fileResolver.source["Comments"] = "--!str";
 
-    auto ac = Luau::autocomplete(frontend, "Comments", Position{0, 6}, nullCallback);
+    auto ac = autocomplete("Comments", Position{0, 6});
     CHECK_EQ(0, ac.entryMap.size());
 }
 
@@ -2391,7 +2418,7 @@ TEST_CASE_FIXTURE(ACBuiltinsFixture, "autocompleteProp_index_function_metamethod
         --          | Column 20
     )";
 
-    auto ac = Luau::autocomplete(frontend, "Module/A", Position{9, 20}, nullCallback);
+    auto ac = autocomplete("Module/A", Position{9, 20});
     REQUIRE_EQ(1, ac.entryMap.size());
     CHECK(ac.entryMap.count("x"));
 }
@@ -2484,7 +2511,7 @@ TEST_CASE_FIXTURE(ACFixture, "not_the_var_we_are_defining")
 {
     fileResolver.source["Module/A"] = "abc,de";
 
-    auto ac = Luau::autocomplete(frontend, "Module/A", Position{0, 6}, nullCallback);
+    auto ac = autocomplete("Module/A", Position{0, 6});
     CHECK(!ac.entryMap.count("de"));
 }
 
@@ -2495,7 +2522,7 @@ TEST_CASE_FIXTURE(ACFixture, "recursive_function_global")
 end
 )";
 
-    auto ac = Luau::autocomplete(frontend, "global", Position{1, 0}, nullCallback);
+    auto ac = autocomplete("global", Position{1, 0});
     CHECK(ac.entryMap.count("abc"));
 }
 
@@ -2508,7 +2535,7 @@ TEST_CASE_FIXTURE(ACFixture, "recursive_function_local")
 end
 )";
 
-    auto ac = Luau::autocomplete(frontend, "local", Position{1, 0}, nullCallback);
+    auto ac = autocomplete("local", Position{1, 0});
     CHECK(ac.entryMap.count("abc"));
 }
 
@@ -3147,6 +3174,8 @@ t:@1
         REQUIRE(ac.entryMap.count("two"));
         CHECK(!ac.entryMap["one"].wrongIndexType);
         CHECK(ac.entryMap["two"].wrongIndexType);
+        CHECK(ac.entryMap["one"].indexedWithSelf);
+        CHECK(ac.entryMap["two"].indexedWithSelf);
     }
 
     {
@@ -3161,6 +3190,8 @@ t.@1
         REQUIRE(ac.entryMap.count("two"));
         CHECK(ac.entryMap["one"].wrongIndexType);
         CHECK(!ac.entryMap["two"].wrongIndexType);
+        CHECK(!ac.entryMap["one"].indexedWithSelf);
+        CHECK(!ac.entryMap["two"].indexedWithSelf);
     }
 }
 
@@ -3190,6 +3221,7 @@ t:@1
 
     REQUIRE(ac.entryMap.count("m"));
     CHECK(!ac.entryMap["m"].wrongIndexType);
+    CHECK(ac.entryMap["m"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls")
@@ -3204,6 +3236,7 @@ t:@1
 
     REQUIRE(ac.entryMap.count("m"));
     CHECK(ac.entryMap["m"].wrongIndexType);
+    CHECK(ac.entryMap["m"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls_2")
@@ -3219,6 +3252,7 @@ t:@1
 
     REQUIRE(ac.entryMap.count("f"));
     CHECK(ac.entryMap["f"].wrongIndexType);
+    CHECK(ac.entryMap["f"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "do_wrong_compatible_self_calls")
@@ -3234,6 +3268,22 @@ t:@1
     REQUIRE(ac.entryMap.count("m"));
     // We can make changes to mark this as a wrong way to call even though it's compatible
     CHECK(!ac.entryMap["m"].wrongIndexType);
+    CHECK(ac.entryMap["m"].indexedWithSelf);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "do_wrong_compatible_nonself_calls")
+{
+    check(R"(
+local t = {}
+function t:m(x: string) end
+t.@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("m"));
+    CHECK(!ac.entryMap["m"].wrongIndexType);
+    CHECK(!ac.entryMap["m"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "no_wrong_compatible_self_calls_with_generics")
@@ -3249,6 +3299,7 @@ t:@1
     REQUIRE(ac.entryMap.count("m"));
     // While this call is compatible with the type, this requires instantiation of a generic type which we don't perform
     CHECK(ac.entryMap["m"].wrongIndexType);
+    CHECK(ac.entryMap["m"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "string_prim_self_calls_are_fine")
@@ -3262,10 +3313,13 @@ s:@1
 
     REQUIRE(ac.entryMap.count("byte"));
     CHECK(ac.entryMap["byte"].wrongIndexType == false);
+    CHECK(ac.entryMap["byte"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("char"));
     CHECK(ac.entryMap["char"].wrongIndexType == true);
+    CHECK(ac.entryMap["char"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("sub"));
     CHECK(ac.entryMap["sub"].wrongIndexType == false);
+    CHECK(ac.entryMap["sub"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "string_prim_non_self_calls_are_avoided")
@@ -3279,8 +3333,10 @@ s.@1
 
     REQUIRE(ac.entryMap.count("char"));
     CHECK(ac.entryMap["char"].wrongIndexType == false);
+    CHECK(!ac.entryMap["char"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("sub"));
     CHECK(ac.entryMap["sub"].wrongIndexType == true);
+    CHECK(!ac.entryMap["sub"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACBuiltinsFixture, "library_non_self_calls_are_fine")
@@ -3293,10 +3349,13 @@ string.@1
 
     REQUIRE(ac.entryMap.count("byte"));
     CHECK(ac.entryMap["byte"].wrongIndexType == false);
+    CHECK(!ac.entryMap["byte"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("char"));
     CHECK(ac.entryMap["char"].wrongIndexType == false);
+    CHECK(!ac.entryMap["char"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("sub"));
     CHECK(ac.entryMap["sub"].wrongIndexType == false);
+    CHECK(!ac.entryMap["sub"].indexedWithSelf);
 
     check(R"(
 table.@1
@@ -3306,10 +3365,13 @@ table.@1
 
     REQUIRE(ac.entryMap.count("remove"));
     CHECK(ac.entryMap["remove"].wrongIndexType == false);
+    CHECK(!ac.entryMap["remove"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("getn"));
     CHECK(ac.entryMap["getn"].wrongIndexType == false);
+    CHECK(!ac.entryMap["getn"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("insert"));
     CHECK(ac.entryMap["insert"].wrongIndexType == false);
+    CHECK(!ac.entryMap["insert"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACBuiltinsFixture, "library_self_calls_are_invalid")
@@ -3322,13 +3384,16 @@ string:@1
 
     REQUIRE(ac.entryMap.count("byte"));
     CHECK(ac.entryMap["byte"].wrongIndexType == true);
+    CHECK(ac.entryMap["byte"].indexedWithSelf);
     REQUIRE(ac.entryMap.count("char"));
     CHECK(ac.entryMap["char"].wrongIndexType == true);
+    CHECK(ac.entryMap["char"].indexedWithSelf);
 
     // We want the next test to evaluate to 'true', but we have to allow function defined with 'self' to be callable with ':'
     // We may change the definition of the string metatable to not use 'self' types in the future (like byte/char/pack/unpack)
     REQUIRE(ac.entryMap.count("sub"));
     CHECK(ac.entryMap["sub"].wrongIndexType == false);
+    CHECK(ac.entryMap["sub"].indexedWithSelf);
 }
 
 TEST_CASE_FIXTURE(ACFixture, "source_module_preservation_and_invalidation")
@@ -3489,4 +3554,480 @@ TEST_CASE_FIXTURE(ACFixture, "frontend_use_correct_global_scope")
     CHECK(ac.entryMap.count("Name"));
 }
 
+TEST_CASE_FIXTURE(ACFixture, "string_completion_outside_quotes")
+{
+    ScopedFastFlag flag{"LuauDisableCompletionOutsideQuotes", true};
+
+    loadDefinition(R"(
+        declare function require(path: string): any
+    )");
+
+    std::optional<Binding> require = frontend.globalsForAutocomplete.globalScope->linearSearchForBinding("require");
+    REQUIRE(require);
+    Luau::unfreeze(frontend.globalsForAutocomplete.globalTypes);
+    attachTag(require->typeId, "RequireCall");
+    Luau::freeze(frontend.globalsForAutocomplete.globalTypes);
+
+    check(R"(
+        local x = require(@1"@2"@3)
+    )");
+
+    StringCompletionCallback callback = [](std::string, std::optional<const ClassType*>,
+                                            std::optional<std::string> contents) -> std::optional<AutocompleteEntryMap>
+    {
+        Luau::AutocompleteEntryMap results = {{"test", Luau::AutocompleteEntry{Luau::AutocompleteEntryKind::String, std::nullopt, false, false}}};
+        return results;
+    };
+
+    auto ac = autocomplete('2', callback);
+
+    CHECK_EQ(1, ac.entryMap.size());
+    CHECK(ac.entryMap.count("test"));
+
+    ac = autocomplete('1', callback);
+
+    CHECK_EQ(0, ac.entryMap.size());
+
+    ac = autocomplete('3', callback);
+
+    CHECK_EQ(0, ac.entryMap.size());
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_empty")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: () -> ())
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function()  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (number, string) -> ())
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: number, a1: string)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_args_single_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (number, string) -> (string))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: number, a1: string): string  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_args_multi_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (number, string) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: number, a1: string): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled__noargs_multi_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: () -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled__varargs_multi_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (...number) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(...: number): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_multi_varargs_multi_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (string, ...number) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: string, ...: number): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_multi_varargs_varargs_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (string, ...number) -> ...number)
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: string, ...: number): ...number  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_multi_varargs_multi_varargs_return")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (string, ...number) -> (boolean, ...number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: string, ...: number): (boolean, ...number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_named_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (foo: number, bar: string) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(foo: number, bar: string): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_partially_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (number, bar: string) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(a0: number, bar: string): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_partially_args_last")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (foo: number, string) -> (string, number))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(foo: number, a1: string): (string, number)  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_typeof_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local t = { a = 1, b = 2 }
+
+local function foo(a: (foo: typeof(t)) -> ())
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(foo)  end"; // Cannot utter this type.
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_table_literal_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: (tbl: { x: number, y: number }) -> number) return a({x=2, y = 3}) end
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(tbl: { x: number, y: number }): number  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_typeof_returns")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local t = { a = 1, b = 2 }
+
+local function foo(a: () -> typeof(t))
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function()  end"; // Cannot utter this type.
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_table_literal_args")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: () -> { x: number, y: number }) return {x=2, y = 3} end
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(): { x: number, y: number }  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_typeof_vararg")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local t = { a = 1, b = 2 }
+
+local function foo(a: (...typeof(t)) -> ())
+    a()
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(...)  end"; // Cannot utter this type.
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_generic_type_pack_vararg")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo<A>(a: (...A) -> number, ...: A)
+	return a(...)
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(...): number  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "anonymous_autofilled_generic_on_argument_type_pack_vararg")
+{
+    ScopedFastFlag flag{"LuauAnonymousAutofilled", true};
+
+    check(R"(
+local function foo(a: <T...>(...: T...) -> number)
+	return a(4, 5, 6)
+end
+
+foo(@1)
+    )");
+
+    const std::optional<std::string> EXPECTED_INSERT = "function(...): number  end";
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count(kGeneratedAnonymousFunctionEntryName) == 1);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].kind == Luau::AutocompleteEntryKind::GeneratedFunction);
+    CHECK(ac.entryMap[kGeneratedAnonymousFunctionEntryName].typeCorrect == Luau::TypeCorrectKind::Correct);
+    REQUIRE(ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+    CHECK_EQ(EXPECTED_INSERT, *ac.entryMap[kGeneratedAnonymousFunctionEntryName].insertText);
+}
+
 TEST_SUITE_END();

tests/Compiler.test.cpp

@@ -6978,6 +6978,8 @@ L3: RETURN R0 0
 
 TEST_CASE("BuiltinArity")
 {
+    ScopedFastFlag sff("LuauCompileFixBuiltinArity", true);
+
     // by default we can't assume that we know parameter/result count for builtins as they can be overridden at runtime
     CHECK_EQ("\n" + compileFunction(R"(
 return math.abs(unknown())
@@ -7037,6 +7039,21 @@ FASTCALL 34 L0
 GETIMPORT R0 4 [bit32.extract]
 CALL R0 -1 1
 L0: RETURN R0 1
+)");
+
+    // some builtins are not variadic and have a fixed number of arguments but are not none-safe, meaning that we can't replace calls that may
+    // return none with calls that will return nil
+    CHECK_EQ("\n" + compileFunction(R"(
+return type(unknown())
+)",
+                        0, 2),
+        R"(
+GETIMPORT R1 1 [unknown]
+CALL R1 0 -1
+FASTCALL 40 L0
+GETIMPORT R0 3 [type]
+CALL R0 -1 1
+L0: RETURN R0 1
 )");
 
     // importantly, this optimization also helps us get around the multret inlining restriction for builtin wrappers

tests/Conformance.test.cpp

@@ -273,6 +273,8 @@ TEST_CASE("Assert")
 
 TEST_CASE("Basic")
 {
+    ScopedFastFlag sff("LuauCompileFixBuiltinArity", true);
+
     runConformance("basic.lua");
 }
 
@@ -326,6 +328,8 @@ TEST_CASE("Clear")
 
 TEST_CASE("Strings")
 {
+    ScopedFastFlag sff("LuauCompileFixBuiltinArity", true);
+
     runConformance("strings.lua");
 }
 
@@ -1112,6 +1116,34 @@ static bool endsWith(const std::string& str, const std::string& suffix)
     return suffix == std::string_view(str.c_str() + str.length() - suffix.length(), suffix.length());
 }
 
+TEST_CASE("ApiType")
+{
+    StateRef globalState(luaL_newstate(), lua_close);
+    lua_State* L = globalState.get();
+
+    lua_pushnumber(L, 2);
+    CHECK(strcmp(luaL_typename(L, -1), "number") == 0);
+    CHECK(strcmp(luaL_typename(L, 1), "number") == 0);
+    CHECK(lua_type(L, -1) == LUA_TNUMBER);
+    CHECK(lua_type(L, 1) == LUA_TNUMBER);
+
+    CHECK(strcmp(luaL_typename(L, 2), "no value") == 0);
+    CHECK(lua_type(L, 2) == LUA_TNONE);
+    CHECK(strcmp(lua_typename(L, lua_type(L, 2)), "no value") == 0);
+
+    lua_newuserdata(L, 0);
+    CHECK(strcmp(luaL_typename(L, -1), "userdata") == 0);
+    CHECK(lua_type(L, -1) == LUA_TUSERDATA);
+
+    lua_newtable(L);
+    lua_pushstring(L, "hello");
+    lua_setfield(L, -2, "__type");
+    lua_setmetatable(L, -2);
+
+    CHECK(strcmp(luaL_typename(L, -1), "hello") == 0);
+    CHECK(lua_type(L, -1) == LUA_TUSERDATA);
+}
+
 #if !LUA_USE_LONGJMP
 TEST_CASE("ExceptionObject")
 {

tests/ConstraintGraphBuilderFixture.cpp

@@ -21,7 +21,7 @@ void ConstraintGraphBuilderFixture::generateConstraints(const std::string& code)
     AstStatBlock* root = parse(code);
     dfg = std::make_unique<DataFlowGraph>(DataFlowGraphBuilder::build(root, NotNull{&ice}));
     cgb = std::make_unique<ConstraintGraphBuilder>(mainModule, &arena, NotNull(&moduleResolver), builtinTypes, NotNull(&ice),
-        frontend.globals.globalScope, /*prepareModuleScope*/ nullptr, &logger, NotNull{dfg.get()});
+        frontend.globals.globalScope, /*prepareModuleScope*/ nullptr, &logger, NotNull{dfg.get()}, std::vector<RequireCycle>());
     cgb->visit(root);
     rootScope = cgb->rootScope;
     constraints = Luau::borrowConstraints(cgb->constraints);
@@ -30,7 +30,7 @@ void ConstraintGraphBuilderFixture::generateConstraints(const std::string& code)
 void ConstraintGraphBuilderFixture::solve(const std::string& code)
 {
     generateConstraints(code);
-    ConstraintSolver cs{NotNull{&normalizer}, NotNull{rootScope}, constraints, "MainModule", NotNull(&moduleResolver), {}, &logger};
+    ConstraintSolver cs{NotNull{&normalizer}, NotNull{rootScope}, constraints, "MainModule", NotNull(&moduleResolver), {}, &logger, {}};
     cs.run();
 }
 

tests/CostModel.test.cpp

@@ -133,6 +133,8 @@ end
 
 TEST_CASE("ControlFlow")
 {
+    ScopedFastFlag sff("LuauAssignmentHasCost", true);
+
     uint64_t model = modelFunction(R"(
 function test(a)
     while a < 0 do
@@ -156,8 +158,8 @@ end
     const bool args1[] = {false};
     const bool args2[] = {true};
 
-    CHECK_EQ(82, Luau::Compile::computeCost(model, args1, 1));
-    CHECK_EQ(79, Luau::Compile::computeCost(model, args2, 1));
+    CHECK_EQ(76, Luau::Compile::computeCost(model, args1, 1));
+    CHECK_EQ(73, Luau::Compile::computeCost(model, args2, 1));
 }
 
 TEST_CASE("Conditional")
@@ -240,4 +242,25 @@ end
     CHECK_EQ(3, Luau::Compile::computeCost(model, args2, 1));
 }
 
+TEST_CASE("MultipleAssignments")
+{
+    ScopedFastFlag sff("LuauAssignmentHasCost", true);
+
+    uint64_t model = modelFunction(R"(
+function test(a)
+    local x = 0
+    x = a
+    x = a + 1
+    x, x, x = a
+    x = a, a, a
+end
+)");
+
+    const bool args1[] = {false};
+    const bool args2[] = {true};
+
+    CHECK_EQ(8, Luau::Compile::computeCost(model, args1, 1));
+    CHECK_EQ(7, Luau::Compile::computeCost(model, args2, 1));
+}
+
 TEST_SUITE_END();

tests/Fixture.cpp

@@ -176,7 +176,7 @@ AstStatBlock* Fixture::parse(const std::string& source, const ParseOptions& pars
             if (FFlag::DebugLuauDeferredConstraintResolution)
             {
                 ModulePtr module = Luau::check(*sourceModule, {}, builtinTypes, NotNull{&ice}, NotNull{&moduleResolver}, NotNull{&fileResolver},
-                    frontend.globals.globalScope, /*prepareModuleScope*/ nullptr, frontend.options);
+                    frontend.globals.globalScope, /*prepareModuleScope*/ nullptr, frontend.options, {});
 
                 Luau::lint(sourceModule->root, *sourceModule->names, frontend.globals.globalScope, module.get(), sourceModule->hotcomments, {});
             }
@@ -415,6 +415,17 @@ TypeId Fixture::requireTypeAlias(const std::string& name)
     return *ty;
 }
 
+TypeId Fixture::requireExportedType(const ModuleName& moduleName, const std::string& name)
+{
+    ModulePtr module = frontend.moduleResolver.getModule(moduleName);
+    REQUIRE(module);
+
+    auto it = module->exportedTypeBindings.find(name);
+    REQUIRE(it != module->exportedTypeBindings.end());
+
+    return it->second.type;
+}
+
 std::string Fixture::decorateWithTypes(const std::string& code)
 {
     fileResolver.source[mainModuleName] = code;

tests/Fixture.h

@@ -2,6 +2,8 @@
 #pragma once
 
 #include "Luau/Config.h"
+#include "Luau/Differ.h"
+#include "Luau/Error.h"
 #include "Luau/FileResolver.h"
 #include "Luau/Frontend.h"
 #include "Luau/IostreamHelpers.h"
@@ -15,6 +17,7 @@
 #include "IostreamOptional.h"
 #include "ScopedFlags.h"
 
+#include "doctest.h"
 #include <string>
 #include <unordered_map>
 #include <optional>
@@ -92,6 +95,7 @@ struct Fixture
     std::optional<TypeId> lookupType(const std::string& name);
     std::optional<TypeId> lookupImportedType(const std::string& moduleAlias, const std::string& name);
     TypeId requireTypeAlias(const std::string& name);
+    TypeId requireExportedType(const ModuleName& moduleName, const std::string& name);
 
     ScopedFastFlag sff_DebugLuauFreezeArena;
 
@@ -153,6 +157,51 @@ std::optional<TypeId> linearSearchForBinding(Scope* scope, const char* name);
 void registerHiddenTypes(Frontend* frontend);
 void createSomeClasses(Frontend* frontend);
 
+template<typename BaseFixture>
+struct DifferFixtureGeneric : BaseFixture
+{
+    void compareNe(TypeId left, TypeId right, const std::string& expectedMessage)
+    {
+        std::string diffMessage;
+        try
+        {
+            DifferResult diffRes = diff(left, right);
+            REQUIRE_MESSAGE(diffRes.diffError.has_value(), "Differ did not report type error, even though types are unequal");
+            diffMessage = diffRes.diffError->toString();
+        }
+        catch (const InternalCompilerError& e)
+        {
+            REQUIRE_MESSAGE(false, ("InternalCompilerError: " + e.message));
+        }
+        CHECK_EQ(expectedMessage, diffMessage);
+    }
+
+    void compareTypesNe(const std::string& leftSymbol, const std::string& rightSymbol, const std::string& expectedMessage)
+    {
+        compareNe(BaseFixture::requireType(leftSymbol), BaseFixture::requireType(rightSymbol), expectedMessage);
+    }
+
+    void compareEq(TypeId left, TypeId right)
+    {
+        try
+        {
+            DifferResult diffRes = diff(left, right);
+            CHECK_MESSAGE(!diffRes.diffError.has_value(), diffRes.diffError->toString());
+        }
+        catch (const InternalCompilerError& e)
+        {
+            REQUIRE_MESSAGE(false, ("InternalCompilerError: " + e.message));
+        }
+    }
+
+    void compareTypesEq(const std::string& leftSymbol, const std::string& rightSymbol)
+    {
+        compareEq(BaseFixture::requireType(leftSymbol), BaseFixture::requireType(rightSymbol));
+    }
+};
+using DifferFixture = DifferFixtureGeneric<Fixture>;
+using DifferFixtureWithBuiltins = DifferFixtureGeneric<BuiltinsFixture>;
+
 } // namespace Luau
 
 #define LUAU_REQUIRE_ERRORS(result) \

tests/Frontend.test.cpp

@@ -444,6 +444,53 @@ TEST_CASE_FIXTURE(FrontendFixture, "cycle_incremental_type_surface_longer")
     CHECK_EQ(toString(tyB), "any");
 }
 
+TEST_CASE_FIXTURE(FrontendFixture, "cycle_incremental_type_surface_exports")
+{
+    ScopedFastFlag luauFixCyclicModuleExports{"LuauFixCyclicModuleExports", true};
+
+    fileResolver.source["game/A"] = R"(
+local b = require(game.B)
+export type atype = { x: b.btype }
+return {mod_a = 1}
+    )";
+
+    fileResolver.source["game/B"] = R"(
+export type btype = { x: number }
+
+local function bf()
+    local a = require(game.A)
+    local bfl : a.atype = nil
+    return {bfl.x}
+end
+return {mod_b = 2}
+    )";
+
+    ToStringOptions opts;
+    opts.exhaustive = true;
+
+    CheckResult resultA = frontend.check("game/A");
+    LUAU_REQUIRE_ERRORS(resultA);
+
+    CheckResult resultB = frontend.check("game/B");
+    LUAU_REQUIRE_ERRORS(resultB);
+
+    TypeId tyB = requireExportedType("game/B", "btype");
+    CHECK_EQ(toString(tyB, opts), "{| x: number |}");
+
+    TypeId tyA = requireExportedType("game/A", "atype");
+    CHECK_EQ(toString(tyA, opts), "{| x: any |}");
+
+    frontend.markDirty("game/B");
+    resultB = frontend.check("game/B");
+    LUAU_REQUIRE_ERRORS(resultB);
+
+    tyB = requireExportedType("game/B", "btype");
+    CHECK_EQ(toString(tyB, opts), "{| x: number |}");
+
+    tyA = requireExportedType("game/A", "atype");
+    CHECK_EQ(toString(tyA, opts), "{| x: any |}");
+}
+
 TEST_CASE_FIXTURE(FrontendFixture, "dont_reparse_clean_file_when_linting")
 {
     fileResolver.source["Modules/A"] = R"(

tests/Linter.test.cpp

@@ -1657,6 +1657,8 @@ _ = (math.random() < 0.5 and false) or 42 -- currently ignored
 
 TEST_CASE_FIXTURE(Fixture, "WrongComment")
 {
+    ScopedFastFlag sff("LuauLintNativeComment", true);
+
     LintResult result = lint(R"(
 --!strict
 --!struct
@@ -1666,17 +1668,19 @@ TEST_CASE_FIXTURE(Fixture, "WrongComment")
 --!nolint UnknownGlobal
 --! no more lint
 --!strict here
+--!native on
 do end
 --!nolint
 )");
 
-    REQUIRE(6 == result.warnings.size());
+    REQUIRE(7 == result.warnings.size());
     CHECK_EQ(result.warnings[0].text, "Unknown comment directive 'struct'; did you mean 'strict'?");
     CHECK_EQ(result.warnings[1].text, "Unknown comment directive 'nolintGlobal'");
     CHECK_EQ(result.warnings[2].text, "nolint directive refers to unknown lint rule 'Global'");
     CHECK_EQ(result.warnings[3].text, "nolint directive refers to unknown lint rule 'KnownGlobal'; did you mean 'UnknownGlobal'?");
     CHECK_EQ(result.warnings[4].text, "Comment directive with the type checking mode has extra symbols at the end of the line");
-    CHECK_EQ(result.warnings[5].text, "Comment directive is ignored because it is placed after the first non-comment token");
+    CHECK_EQ(result.warnings[5].text, "native directive has extra symbols at the end of the line");
+    CHECK_EQ(result.warnings[6].text, "Comment directive is ignored because it is placed after the first non-comment token");
 }
 
 TEST_CASE_FIXTURE(Fixture, "WrongCommentMuteSelf")

tests/Simplify.test.cpp

@@ -114,6 +114,17 @@ struct SimplifyFixture : Fixture
 
 TEST_SUITE_BEGIN("Simplify");
 
+TEST_CASE_FIXTURE(SimplifyFixture, "overload_negation_refinement_is_never")
+{
+    TypeId f1 = mkFunction(stringTy, numberTy);
+    TypeId f2 = mkFunction(numberTy, stringTy);
+    TypeId intersection = arena->addType(IntersectionType{{f1, f2}});
+    TypeId unionT = arena->addType(UnionType{{errorTy, functionTy}});
+    TypeId negationT = mkNegation(unionT);
+    // The intersection of string -> number & number -> string, ~(error | function)
+    CHECK(neverTy == intersect(intersection, negationT));
+}
+
 TEST_CASE_FIXTURE(SimplifyFixture, "unknown_and_other_tops_and_bottom_types")
 {
     CHECK(unknownTy == intersect(unknownTy, unknownTy));

tests/StringUtils.test.cpp

@@ -59,7 +59,7 @@ TEST_CASE("BenchmarkLevenshteinDistance")
     auto end = std::chrono::steady_clock::now();
     auto time = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
 
-    std::cout << "Running levenshtein distance " << count << " times took " << time.count() << "ms" << std::endl;
+    MESSAGE("Running levenshtein distance ", count, " times took ", time.count(), "ms");
 }
 #endif
 

tests/ToString.test.cpp

@@ -11,6 +11,7 @@
 using namespace Luau;
 
 LUAU_FASTFLAG(LuauRecursiveTypeParameterRestriction);
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 
 TEST_SUITE_BEGIN("ToString");
 

tests/TypeInfer.anyerror.test.cpp

@@ -13,6 +13,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("TypeInferAnyError");
 
 TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_returns_any")

tests/TypeInfer.classes.test.cpp

@@ -12,6 +12,8 @@
 using namespace Luau;
 using std::nullopt;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("TypeInferClasses");
 
 TEST_CASE_FIXTURE(ClassFixture, "call_method_of_a_class")

tests/TypeInfer.functions.test.cpp

@@ -14,7 +14,8 @@
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauInstantiateInSubtyping)
+LUAU_FASTFLAG(LuauInstantiateInSubtyping);
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 
 TEST_SUITE_BEGIN("TypeInferFunctions");
 
@@ -2094,6 +2095,25 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "attempt_to_call_an_intersection_of_tables_wi
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "generic_packs_are_not_variadic")
+{
+    ScopedFastFlag sff{"DebugLuauDeferredConstraintResolution", true};
+
+    CheckResult result = check(R"(
+        local function apply<a, b..., c...>(f: (a, b...) -> c..., x: a)
+            return f(x)
+        end
+
+        local function add(x: number, y: number)
+            return x + y
+        end
+
+        apply(add, 5)
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
 TEST_CASE_FIXTURE(BuiltinsFixture, "num_is_solved_before_num_or_str")
 {
     CheckResult result = check(R"(

tests/TypeInfer.generics.test.cpp

@@ -9,7 +9,8 @@
 
 #include "doctest.h"
 
-LUAU_FASTFLAG(LuauInstantiateInSubtyping)
+LUAU_FASTFLAG(LuauInstantiateInSubtyping);
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 
 using namespace Luau;
 

tests/TypeInfer.intersectionTypes.test.cpp

@@ -8,6 +8,7 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 
 TEST_SUITE_BEGIN("IntersectionTypes");
 

tests/TypeInfer.provisional.test.cpp

@@ -9,6 +9,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("ProvisionalTests");
 
 // These tests check for behavior that differs from the final behavior we'd
@@ -502,6 +504,9 @@ TEST_CASE_FIXTURE(Fixture, "free_options_cannot_be_unified_together")
     Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
     Unifier u{NotNull{&normalizer}, NotNull{scope.get()}, Location{}, Variance::Covariant};
 
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+        u.enableNewSolver();
+
     u.tryUnify(option1, option2);
 
     CHECK(!u.failure);
@@ -565,7 +570,7 @@ return wrapStrictTable(Constants, "Constants")
     std::optional<TypeId> result = first(m->returnType);
     REQUIRE(result);
     if (FFlag::DebugLuauDeferredConstraintResolution)
-        CHECK_EQ("(any & ~table)?", toString(*result));
+        CHECK_EQ("(any & ~(*error-type* | table))?", toString(*result));
     else
         CHECK_MESSAGE(get<AnyType>(*result), *result);
 }
@@ -905,6 +910,9 @@ TEST_CASE_FIXTURE(Fixture, "free_options_can_be_unified_together")
     Normalizer normalizer{&arena, builtinTypes, NotNull{&sharedState}};
     Unifier u{NotNull{&normalizer}, NotNull{scope.get()}, Location{}, Variance::Covariant};
 
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+        u.enableNewSolver();
+
     u.tryUnify(option1, option2);
 
     CHECK(!u.failure);

tests/TypeInfer.refinements.test.cpp

@@ -1820,4 +1820,46 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "refinements_should_preserve_error_suppressio
         LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "many_refinements_on_val")
+{
+    CheckResult result = check(R"(
+        local function is_nan(val: any): boolean
+            return type(val) == "number" and val ~= val
+        end
+
+        local function is_js_boolean(val: any): boolean
+            return not not val and val ~= 0 and val ~= "" and not is_nan(val)
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("(any) -> boolean", toString(requireType("is_nan")));
+    CHECK_EQ("(any) -> boolean", toString(requireType("is_js_boolean")));
+}
+
+TEST_CASE_FIXTURE(BuiltinsFixture, "refine_unknown_to_table")
+{
+    ScopedFastFlag sff{"DebugLuauDeferredConstraintResolution", true};
+    // this test is DCR-only as an instance of DCR fixing a bug in the old solver
+
+    CheckResult result = check(R"(
+        local a : unknown = nil
+
+        local idx, val
+
+        if typeof(a) == "table" then
+            for i, v in a do
+                idx = i
+                val = v
+            end
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("unknown", toString(requireType("idx")));
+    CHECK_EQ("unknown", toString(requireType("val")));
+}
+
 TEST_SUITE_END();

tests/TypeInfer.singletons.test.cpp

@@ -7,6 +7,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("TypeSingletons");
 
 TEST_CASE_FIXTURE(Fixture, "function_args_infer_singletons")

tests/TypeInfer.tables.test.cpp

@@ -132,6 +132,24 @@ TEST_CASE_FIXTURE(Fixture, "cannot_change_type_of_table_prop")
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "report_sensible_error_when_adding_a_value_to_a_nonexistent_prop")
+{
+    CheckResult result = check(R"(
+        local t = {}
+        t.foo[1] = 'one'
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    INFO(result.errors[0]);
+
+    UnknownProperty* err = get<UnknownProperty>(result.errors[0]);
+    REQUIRE(err);
+
+    CHECK("t" == toString(err->table));
+    CHECK("foo" == err->key);
+}
+
 TEST_CASE_FIXTURE(Fixture, "function_calls_can_produce_tables")
 {
     CheckResult result = check("function get_table() return {prop=999} end    get_table().prop = 0");
@@ -439,8 +457,6 @@ TEST_CASE_FIXTURE(Fixture, "table_param_row_polymorphism_2")
     )");
 
     LUAU_REQUIRE_NO_ERRORS(result);
-    for (const auto& e : result.errors)
-        std::cout << "Error: " << e << std::endl;
 
     TypeId qType = requireType("q");
     const TableType* qTable = get<TableType>(qType);
@@ -3642,4 +3658,75 @@ end
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "certain_properties_of_table_literal_arguments_can_be_covariant")
+{
+    CheckResult result = check(R"(
+        function f(a: {[string]: string | {any} | nil })
+            return a
+        end
+
+        local x = f({
+            title = "Feature.VirtualEvents.EnableNotificationsModalTitle",
+            body = "Feature.VirtualEvents.EnableNotificationsModalBody",
+            notNow = "Feature.VirtualEvents.NotNowButton",
+            getNotified = "Feature.VirtualEvents.GetNotifiedButton",
+        })
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "subproperties_can_also_be_covariantly_tested")
+{
+    CheckResult result = check(R"(
+        type T = {
+            [string]: {[string]: (string | number)?}
+        }
+
+        function f(t: T)
+            return t
+        end
+
+        local x = f({
+            subprop={x="hello"}
+        })
+
+        local y = f({
+            subprop={x=41}
+        })
+
+        local z = f({
+            subprop={}
+        })
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "cyclic_shifted_tables")
+{
+    CheckResult result = check(R"(
+        local function id<a>(x: a): a
+          return x
+        end
+
+        -- Remove name from cyclic table
+        local foo = id({})
+        foo.foo = id({})
+        foo.foo.foo = id({})
+        foo.foo.foo.foo = id({})
+        foo.foo.foo.foo.foo = foo
+
+        local almostFoo = id({})
+        almostFoo.foo = id({})
+        almostFoo.foo.foo = id({})
+        almostFoo.foo.foo.foo = id({})
+        almostFoo.foo.foo.foo.foo = almostFoo
+        -- Shift
+        almostFoo = almostFoo.foo.foo
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.test.cpp

@@ -224,7 +224,7 @@ TEST_CASE_FIXTURE(Fixture, "crazy_complexity")
         A:A():A():A():A():A():A():A():A():A():A():A()
     )");
 
-    std::cout << "OK!  Allocated " << typeChecker.types.size() << " types" << std::endl;
+    MESSAGE("OK!  Allocated ", typeChecker.types.size(), " types");
 }
 #endif
 
@@ -1332,4 +1332,43 @@ TEST_CASE_FIXTURE(Fixture, "handle_self_referential_HasProp_constraints")
     )");
 }
 
+/* We had an issue where we were unifying two type packs
+ *
+ * free-2-0... and (string, free-4-0...)
+ *
+ * The correct thing to do here is to promote everything on the right side to
+ * level 2-0 before binding the left pack to the right.  If we fail to do this,
+ * then the code fragment here fails to typecheck because the argument and
+ * return types of C are generalized before we ever get to checking the body of
+ * C.
+ */
+TEST_CASE_FIXTURE(Fixture, "promote_tail_type_packs")
+{
+    CheckResult result = check(R"(
+        --!strict
+
+        local A: any = nil
+
+        local C
+        local D = A(
+            A({}, {
+                __call = function(a): string
+                    local E: string = C(a)
+                    return E
+                end
+            }),
+            {
+                F = function(s: typeof(C))
+                end
+            }
+        )
+
+        function C(b: any): string
+            return ''
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.tryUnify.test.cpp

@@ -345,7 +345,6 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "metatables_unify_against_shape_of_free_table
 {
     ScopedFastFlag sff[] = {
         {"LuauTransitiveSubtyping", true},
-        {"DebugLuauDeferredConstraintResolution", true},
     };
 
     TableType::Props freeProps{
@@ -369,6 +368,7 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "metatables_unify_against_shape_of_free_table
     TypeId target = arena.addType(TableType{TableState::Unsealed, TypeLevel{}});
     TypeId metatable = arena.addType(MetatableType{target, mt});
 
+    state.enableNewSolver();
     state.tryUnify(metatable, free);
     state.log.commit();
 
@@ -439,11 +439,10 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "unifying_two_unions_under_dcr_does_not_creat
     const TypeId innerType = arena.freshType(nestedScope.get());
 
     ScopedFastFlag sffs[]{
-        {"DebugLuauDeferredConstraintResolution", true},
         {"LuauAlwaysCommitInferencesOfFunctionCalls", true},
     };
 
-    state.enableScopeTests();
+    state.enableNewSolver();
 
     SUBCASE("equal_scopes")
     {

tests/TypeInfer.typePacks.cpp

@@ -9,6 +9,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("TypePackTests");
 
 TEST_CASE_FIXTURE(Fixture, "infer_multi_return")

tests/TypeInfer.unionTypes.test.cpp

@@ -8,6 +8,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("UnionTypes");
 
 TEST_CASE_FIXTURE(Fixture, "return_types_can_be_disjoint")

tests/TypeInfer.unknownnever.test.cpp

@@ -6,6 +6,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+
 TEST_SUITE_BEGIN("TypeInferUnknownNever");
 
 TEST_CASE_FIXTURE(Fixture, "string_subtype_and_unknown_supertype")

tests/conformance/basic.lua

@@ -944,6 +944,11 @@ end)(true) == 5050)
 assert(pcall(typeof) == false)
 assert(pcall(type) == false)
 
+function nothing() end
+
+assert(pcall(function() return typeof(nothing()) end) == false)
+assert(pcall(function() return type(nothing()) end) == false)
+
 -- typeof == type in absence of custom userdata
 assert(concat(typeof(5), typeof(nil), typeof({}), typeof(newproxy())) == "number,nil,table,userdata")
 

tests/conformance/math.lua

@@ -235,6 +235,12 @@ assert(flag);
 
 assert(select(2, pcall(math.random, 1, 2, 3)):match("wrong number of arguments"))
 
+-- argument count
+function nothing() end
+
+assert(pcall(math.abs) == false)
+assert(pcall(function() return math.abs(nothing()) end) == false)
+
 -- min/max
 assert(math.min(1) == 1)
 assert(math.min(1, 2) == 1)
@@ -249,6 +255,7 @@ assert(math.max(1, -1, 2) == 2)
 assert(math.noise(0.5) == 0)
 assert(math.noise(0.5, 0.5) == -0.25)
 assert(math.noise(0.5, 0.5, -0.5) == 0.125)
+assert(math.noise(455.7204209769105, 340.80410508750134, 121.80087666537628) == 0.5010709762573242)
 
 local inf = math.huge * 2
 local nan = 0 / 0

tests/conformance/strings.lua

@@ -107,6 +107,12 @@ assert(tostring(1234567890123) == '1234567890123')
 assert(#tostring('\0') == 1)
 assert(tostring(true) == "true")
 assert(tostring(false) == "false")
+
+function nothing() end
+
+assert(pcall(tostring) == false)
+assert(pcall(function() return tostring(nothing()) end) == false)
+
 print('+')
 
 x = '"ílo"\n\\'

tests/main.cpp

@@ -201,7 +201,7 @@ static FValueResult<bool> parseFFlag(std::string_view view)
     auto [name, value] = parseFValueHelper(view);
     bool state = value ? *value == "true" : true;
     if (value && value != "true" && value != "false")
-        std::cerr << "Ignored '" << name << "' because '" << *value << "' is not a valid FFlag state." << std::endl;
+        fprintf(stderr, "Ignored '%s' because '%s' is not a valid flag state\n", name.c_str(), value->c_str());
 
     return {name, state};
 }
@@ -264,9 +264,7 @@ int main(int argc, char** argv)
             if (skipFastFlag(flag->name))
                 continue;
 
-            if (flag->dynamic)
-                std::cout << 'D';
-            std::cout << "FFlag" << flag->name << std::endl;
+            printf("%sFFlag%s\n", flag->dynamic ? "D" : "", flag->name);
         }
 
         return 0;
@@ -286,7 +284,7 @@ int main(int argc, char** argv)
     if (doctest::parseIntOption(argc, argv, "-O", doctest::option_int, level))
     {
         if (level < 0 || level > 2)
-            std::cerr << "Optimization level must be between 0 and 2 inclusive." << std::endl;
+            fprintf(stderr, "Optimization level must be between 0 and 2 inclusive\n");
         else
             optimizationLevel = level;
     }

tools/faillist.txt

@@ -1,4 +1,6 @@
 AstQuery.last_argument_function_call_type
+AutocompleteTest.anonymous_autofilled_generic_on_argument_type_pack_vararg
+AutocompleteTest.anonymous_autofilled_generic_type_pack_vararg
 BuiltinTests.aliased_string_format
 BuiltinTests.assert_removes_falsy_types
 BuiltinTests.assert_removes_falsy_types2
@@ -55,7 +57,6 @@ ProvisionalTests.typeguard_inference_incomplete
 RefinementTest.discriminate_from_truthiness_of_x
 RefinementTest.not_t_or_some_prop_of_t
 RefinementTest.refine_a_property_of_some_global
-RefinementTest.refinements_should_preserve_error_suppression
 RefinementTest.truthy_constraint_on_properties
 RefinementTest.type_narrow_to_vector
 RefinementTest.typeguard_cast_free_table_to_vector
@@ -69,9 +70,6 @@ TableTests.dont_crash_when_setmetatable_does_not_produce_a_metatabletypevar
 TableTests.dont_hang_when_trying_to_look_up_in_cyclic_metatable_index
 TableTests.dont_suggest_exact_match_keys
 TableTests.error_detailed_metatable_prop
-TableTests.expected_indexer_from_table_union
-TableTests.expected_indexer_value_type_extra
-TableTests.expected_indexer_value_type_extra_2
 TableTests.explicitly_typed_table
 TableTests.explicitly_typed_table_with_indexer
 TableTests.fuzz_table_unify_instantiated_table
@@ -128,6 +126,7 @@ TypeInfer.follow_on_new_types_in_substitution
 TypeInfer.fuzz_free_table_type_change_during_index_check
 TypeInfer.infer_assignment_value_types_mutable_lval
 TypeInfer.no_stack_overflow_from_isoptional
+TypeInfer.recursive_function_that_invokes_itself_with_a_refinement_of_its_parameter_2
 TypeInfer.tc_after_error_recovery_no_replacement_name_in_error
 TypeInfer.type_infer_recursion_limit_no_ice
 TypeInfer.type_infer_recursion_limit_normalizer