Merge branch 'upstream' into merge

Analysis/include/Luau/ConstraintGraphBuilder.h

@@ -23,6 +23,30 @@ using ScopePtr = std::shared_ptr<Scope>;
 
 struct DcrLogger;
 
+struct Inference
+{
+    TypeId ty = nullptr;
+
+    Inference() = default;
+
+    explicit Inference(TypeId ty)
+        : ty(ty)
+    {
+    }
+};
+
+struct InferencePack
+{
+    TypePackId tp = nullptr;
+
+    InferencePack() = default;
+
+    explicit InferencePack(TypePackId tp)
+        : tp(tp)
+    {
+    }
+};
+
 struct ConstraintGraphBuilder
 {
     // A list of all the scopes in the module. This vector holds ownership of the
@@ -130,8 +154,10 @@ struct ConstraintGraphBuilder
     void visit(const ScopePtr& scope, AstStatDeclareFunction* declareFunction);
     void visit(const ScopePtr& scope, AstStatError* error);
 
-    TypePackId checkPack(const ScopePtr& scope, AstArray<AstExpr*> exprs, const std::vector<TypeId>& expectedTypes = {});
-    TypePackId checkPack(const ScopePtr& scope, AstExpr* expr, const std::vector<TypeId>& expectedTypes = {});
+    InferencePack checkPack(const ScopePtr& scope, AstArray<AstExpr*> exprs, const std::vector<TypeId>& expectedTypes = {});
+    InferencePack checkPack(const ScopePtr& scope, AstExpr* expr, const std::vector<TypeId>& expectedTypes = {});
+
+    InferencePack checkPack(const ScopePtr& scope, AstExprCall* call, const std::vector<TypeId>& expectedTypes);
 
     /**
      * Checks an expression that is expected to evaluate to one type.
@@ -141,18 +167,19 @@ struct ConstraintGraphBuilder
      *      surrounding context.  Used to implement bidirectional type checking.
      * @return the type of the expression.
      */
-    TypeId check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType = {});
+    Inference check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType = {});
 
-    TypeId check(const ScopePtr& scope, AstExprLocal* local);
-    TypeId check(const ScopePtr& scope, AstExprGlobal* global);
-    TypeId check(const ScopePtr& scope, AstExprIndexName* indexName);
-    TypeId check(const ScopePtr& scope, AstExprIndexExpr* indexExpr);
-    TypeId check(const ScopePtr& scope, AstExprUnary* unary);
-    TypeId check_(const ScopePtr& scope, AstExprUnary* unary);
-    TypeId check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
-    TypeId check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType);
-    TypeId check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert);
-    TypeId check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprConstantBool* bool_, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprLocal* local);
+    Inference check(const ScopePtr& scope, AstExprGlobal* global);
+    Inference check(const ScopePtr& scope, AstExprIndexName* indexName);
+    Inference check(const ScopePtr& scope, AstExprIndexExpr* indexExpr);
+    Inference check(const ScopePtr& scope, AstExprUnary* unary);
+    Inference check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert);
+    Inference check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
 
     TypePackId checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs);
 
@@ -202,7 +229,7 @@ struct ConstraintGraphBuilder
     std::vector<std::pair<Name, GenericTypeDefinition>> createGenerics(const ScopePtr& scope, AstArray<AstGenericType> generics);
     std::vector<std::pair<Name, GenericTypePackDefinition>> createGenericPacks(const ScopePtr& scope, AstArray<AstGenericTypePack> packs);
 
-    TypeId flattenPack(const ScopePtr& scope, Location location, TypePackId tp);
+    Inference flattenPack(const ScopePtr& scope, Location location, InferencePack pack);
 
     void reportError(Location location, TypeErrorData err);
     void reportCodeTooComplex(Location location);

Analysis/include/Luau/Error.h

@@ -7,6 +7,8 @@
 #include "Luau/Variant.h"
 #include "Luau/TypeArena.h"
 
+LUAU_FASTFLAG(LuauIceExceptionInheritanceChange)
+
 namespace Luau
 {
 struct TypeError;
@@ -302,12 +304,20 @@ struct NormalizationTooComplex
     }
 };
 
+struct TypePackMismatch
+{
+    TypePackId wantedTp;
+    TypePackId givenTp;
+
+    bool operator==(const TypePackMismatch& rhs) const;
+};
+
 using TypeErrorData = Variant<TypeMismatch, UnknownSymbol, UnknownProperty, NotATable, CannotExtendTable, OnlyTablesCanHaveMethods,
     DuplicateTypeDefinition, CountMismatch, FunctionDoesNotTakeSelf, FunctionRequiresSelf, OccursCheckFailed, UnknownRequire,
     IncorrectGenericParameterCount, SyntaxError, CodeTooComplex, UnificationTooComplex, UnknownPropButFoundLikeProp, GenericError, InternalError,
     CannotCallNonFunction, ExtraInformation, DeprecatedApiUsed, ModuleHasCyclicDependency, IllegalRequire, FunctionExitsWithoutReturning,
     DuplicateGenericParameter, CannotInferBinaryOperation, MissingProperties, SwappedGenericTypeParameter, OptionalValueAccess, MissingUnionProperty,
-    TypesAreUnrelated, NormalizationTooComplex>;
+    TypesAreUnrelated, NormalizationTooComplex, TypePackMismatch>;
 
 struct TypeError
 {
@@ -374,6 +384,10 @@ struct InternalErrorReporter
 class InternalCompilerError : public std::exception
 {
 public:
+    explicit InternalCompilerError(const std::string& message)
+        : message(message)
+    {
+    }
     explicit InternalCompilerError(const std::string& message, const std::string& moduleName)
         : message(message)
         , moduleName(moduleName)
@@ -388,8 +402,14 @@ public:
     virtual const char* what() const throw();
 
     const std::string message;
-    const std::string moduleName;
+    const std::optional<std::string> moduleName;
     const std::optional<Location> location;
 };
 
+// These two function overloads only exist to facilitate fast flagging a change to InternalCompilerError
+// Both functions can be removed when FFlagLuauIceExceptionInheritanceChange is removed and calling code
+// can directly throw InternalCompilerError.
+[[noreturn]] void throwRuntimeError(const std::string& message);
+[[noreturn]] void throwRuntimeError(const std::string& message, const std::string& moduleName);
+
 } // namespace Luau

Analysis/include/Luau/Normalize.h

@@ -106,9 +106,68 @@ struct std::equal_to<const Luau::TypeIds*>
 namespace Luau
 {
 
-// A normalized string type is either `string` (represented by `nullopt`)
-// or a union of string singletons.
-using NormalizedStringType = std::optional<std::map<std::string, TypeId>>;
+/** A normalized string type is either `string` (represented by `nullopt`) or a
+ * union of string singletons.
+ *
+ * When FFlagLuauNegatedStringSingletons is unset, the representation is as
+ * follows:
+ *
+ * * The `string` data type is represented by the option `singletons` having the
+ *   value `std::nullopt`.
+ * * The type `never` is represented by `singletons` being populated with an
+ *   empty map.
+ * * A union of string singletons is represented by a map populated by the names
+ *   and TypeIds of the singletons contained therein.
+ *
+ * When FFlagLuauNegatedStringSingletons is set, the representation is as
+ * follows:
+ *
+ * * A union of string singletons is finite and includes the singletons named by
+ *   the `singletons` field.
+ * * An intersection of negated string singletons is cofinite and includes the
+ *   singletons excluded by the `singletons` field.  It is implied that cofinite
+ *   values are exclusions from `string` itself.
+ * * The `string` data type is a cofinite set minus zero elements.
+ * * The `never` data type is a finite set plus zero elements.
+ */
+struct NormalizedStringType
+{
+    // When false, this type represents a union of singleton string types.
+    // eg "a" | "b" | "c"
+    //
+    // When true, this type represents string intersected with negated string
+    // singleton types.
+    // eg string & ~"a" & ~"b" & ...
+    bool isCofinite = false;
+
+    // TODO: This field cannot be nullopt when FFlagLuauNegatedStringSingletons
+    // is set. When clipping that flag, we can remove the wrapping optional.
+    std::optional<std::map<std::string, TypeId>> singletons;
+
+    void resetToString();
+    void resetToNever();
+
+    bool isNever() const;
+    bool isString() const;
+
+    /// Returns true if the string has finite domain.
+    ///
+    /// Important subtlety: This method returns true for `never`.  The empty set
+    /// is indeed an empty set.
+    bool isUnion() const;
+
+    /// Returns true if the string has infinite domain.
+    bool isIntersection() const;
+
+    bool includes(const std::string& str) const;
+
+    static const NormalizedStringType never;
+
+    NormalizedStringType() = default;
+    NormalizedStringType(bool isCofinite, std::optional<std::map<std::string, TypeId>> singletons);
+};
+
+bool isSubtype(const NormalizedStringType& subStr, const NormalizedStringType& superStr);
 
 // A normalized function type is either `never` (represented by `nullopt`)
 // or an intersection of function types.
@@ -157,7 +216,7 @@ struct NormalizedType
 
     // The string part of the type.
     // This may be the `string` type, or a union of singletons.
-    NormalizedStringType strings = std::map<std::string, TypeId>{};
+    NormalizedStringType strings;
 
     // The thread part of the type.
     // This type is either never or thread.
@@ -231,8 +290,14 @@ public:
     bool unionNormals(NormalizedType& here, const NormalizedType& there, int ignoreSmallerTyvars = -1);
     bool unionNormalWithTy(NormalizedType& here, TypeId there, int ignoreSmallerTyvars = -1);
 
+    // ------- Negations
+    NormalizedType negateNormal(const NormalizedType& here);
+    TypeIds negateAll(const TypeIds& theres);
+    TypeId negate(TypeId there);
+    void subtractPrimitive(NormalizedType& here, TypeId ty);
+    void subtractSingleton(NormalizedType& here, TypeId ty);
+
     // ------- Normalizing intersections
-    void intersectTysWithTy(TypeIds& here, TypeId there);
     TypeId intersectionOfTops(TypeId here, TypeId there);
     TypeId intersectionOfBools(TypeId here, TypeId there);
     void intersectClasses(TypeIds& heres, const TypeIds& theres);

Analysis/include/Luau/RecursionCounter.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "Luau/Common.h"
+#include "Luau/Error.h"
 
 #include <stdexcept>
 #include <exception>
@@ -9,10 +10,20 @@
 namespace Luau
 {
 
-struct RecursionLimitException : public std::exception
+struct RecursionLimitException : public InternalCompilerError
+{
+    RecursionLimitException()
+        : InternalCompilerError("Internal recursion counter limit exceeded")
+    {
+        LUAU_ASSERT(FFlag::LuauIceExceptionInheritanceChange);
+    }
+};
+
+struct RecursionLimitException_DEPRECATED : public std::exception
 {
     const char* what() const noexcept
     {
+        LUAU_ASSERT(!FFlag::LuauIceExceptionInheritanceChange);
         return "Internal recursion counter limit exceeded";
     }
 };
@@ -42,7 +53,14 @@ struct RecursionLimiter : RecursionCounter
     {
         if (limit > 0 && *count > limit)
         {
-            throw RecursionLimitException();
+            if (FFlag::LuauIceExceptionInheritanceChange)
+            {
+                throw RecursionLimitException();
+            }
+            else
+            {
+                throw RecursionLimitException_DEPRECATED();
+            }
         }
     }
 };

Analysis/include/Luau/ToString.h

@@ -117,6 +117,8 @@ inline std::string toStringNamedFunction(const std::string& funcName, const Func
     return toStringNamedFunction(funcName, ftv, opts);
 }
 
+std::optional<std::string> getFunctionNameAsString(const AstExpr& expr);
+
 // It could be useful to see the text representation of a type during a debugging session instead of exploring the content of the class
 // These functions will dump the type to stdout and can be evaluated in Watch/Immediate windows or as gdb/lldb expression
 std::string dump(TypeId ty);

Analysis/include/Luau/TypeInfer.h

@@ -48,7 +48,17 @@ struct HashBoolNamePair
     size_t operator()(const std::pair<bool, Name>& pair) const;
 };
 
-class TimeLimitError : public std::exception
+class TimeLimitError : public InternalCompilerError
+{
+public:
+    explicit TimeLimitError(const std::string& moduleName)
+        : InternalCompilerError("Typeinfer failed to complete in allotted time", moduleName)
+    {
+        LUAU_ASSERT(FFlag::LuauIceExceptionInheritanceChange);
+    }
+};
+
+class TimeLimitError_DEPRECATED : public std::exception
 {
 public:
     virtual const char* what() const throw();
@@ -236,6 +246,7 @@ public:
 
     [[noreturn]] void ice(const std::string& message, const Location& location);
     [[noreturn]] void ice(const std::string& message);
+    [[noreturn]] void throwTimeLimitError();
 
     ScopePtr childFunctionScope(const ScopePtr& parent, const Location& location, int subLevel = 0);
     ScopePtr childScope(const ScopePtr& parent, const Location& location);

Analysis/include/Luau/Unifier.h

@@ -96,6 +96,8 @@ private:
     void tryUnifyScalarShape(TypeId subTy, TypeId superTy, bool reversed);
     void tryUnifyWithMetatable(TypeId subTy, TypeId superTy, bool reversed);
     void tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed);
+    void tryUnifyTypeWithNegation(TypeId subTy, TypeId superTy);
+    void tryUnifyNegationWithType(TypeId subTy, TypeId superTy);
 
     TypePackId tryApplyOverloadedFunction(TypeId function, const NormalizedFunctionType& overloads, TypePackId args);
 

Analysis/src/AstQuery.cpp

@@ -11,6 +11,8 @@
 
 #include <algorithm>
 
+LUAU_FASTFLAGVARIABLE(LuauCheckOverloadedDocSymbol, false)
+
 namespace Luau
 {
 
@@ -430,6 +432,8 @@ ExprOrLocal findExprOrLocalAtPosition(const SourceModule& source, Position pos)
 static std::optional<DocumentationSymbol> checkOverloadedDocumentationSymbol(
     const Module& module, const TypeId ty, const AstExpr* parentExpr, const std::optional<DocumentationSymbol> documentationSymbol)
 {
+    LUAU_ASSERT(FFlag::LuauCheckOverloadedDocSymbol);
+
     if (!documentationSymbol)
         return std::nullopt;
 
@@ -466,7 +470,38 @@ std::optional<DocumentationSymbol> getDocumentationSymbolAtPosition(const Source
 
     if (std::optional<Binding> binding = findBindingAtPosition(module, source, position))
     {
-        return checkOverloadedDocumentationSymbol(module, binding->typeId, parentExpr, binding->documentationSymbol);
+        if (FFlag::LuauCheckOverloadedDocSymbol)
+        {
+            return checkOverloadedDocumentationSymbol(module, binding->typeId, parentExpr, binding->documentationSymbol);
+        }
+        else
+        {
+            if (binding->documentationSymbol)
+            {
+                // This might be an overloaded function binding.
+                if (get<IntersectionTypeVar>(follow(binding->typeId)))
+                {
+                    TypeId matchingOverload = nullptr;
+                    if (parentExpr && parentExpr->is<AstExprCall>())
+                    {
+                        if (auto it = module.astOverloadResolvedTypes.find(parentExpr))
+                        {
+                            matchingOverload = *it;
+                        }
+                    }
+
+                    if (matchingOverload)
+                    {
+                        std::string overloadSymbol = *binding->documentationSymbol + "/overload/";
+                        // Default toString options are fine for this purpose.
+                        overloadSymbol += toString(matchingOverload);
+                        return overloadSymbol;
+                    }
+                }
+            }
+
+            return binding->documentationSymbol;
+        }
     }
 
     if (targetExpr)
@@ -480,14 +515,20 @@ std::optional<DocumentationSymbol> getDocumentationSymbolAtPosition(const Source
                 {
                     if (auto propIt = ttv->props.find(indexName->index.value); propIt != ttv->props.end())
                     {
-                        return checkOverloadedDocumentationSymbol(module, propIt->second.type, parentExpr, propIt->second.documentationSymbol);
+                        if (FFlag::LuauCheckOverloadedDocSymbol)
+                            return checkOverloadedDocumentationSymbol(module, propIt->second.type, parentExpr, propIt->second.documentationSymbol);
+                        else
+                            return propIt->second.documentationSymbol;
                     }
                 }
                 else if (const ClassTypeVar* ctv = get<ClassTypeVar>(parentTy))
                 {
                     if (auto propIt = ctv->props.find(indexName->index.value); propIt != ctv->props.end())
                     {
-                        return checkOverloadedDocumentationSymbol(module, propIt->second.type, parentExpr, propIt->second.documentationSymbol);
+                        if (FFlag::LuauCheckOverloadedDocSymbol)
+                            return checkOverloadedDocumentationSymbol(module, propIt->second.type, parentExpr, propIt->second.documentationSymbol);
+                        else
+                            return propIt->second.documentationSymbol;
                     }
                 }
             }

Analysis/src/ConstraintGraphBuilder.cpp

@@ -263,7 +263,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
             if (hasAnnotation)
                 expectedTypes.insert(begin(expectedTypes), begin(varTypes) + i, end(varTypes));
 
-            TypePackId exprPack = checkPack(scope, value, expectedTypes);
+            TypePackId exprPack = checkPack(scope, value, expectedTypes).tp;
 
             if (i < local->vars.size)
             {
@@ -292,7 +292,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
             if (hasAnnotation)
                 expectedType = varTypes.at(i);
 
-            TypeId exprType = check(scope, value, expectedType);
+            TypeId exprType = check(scope, value, expectedType).ty;
             if (i < varTypes.size())
             {
                 if (varTypes[i])
@@ -350,7 +350,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatFor* for_)
         if (!expr)
             return;
 
-        TypeId t = check(scope, expr);
+        TypeId t = check(scope, expr).ty;
         addConstraint(scope, expr->location, SubtypeConstraint{t, singletonTypes->numberType});
     };
 
@@ -368,7 +368,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatForIn* forIn)
 {
     ScopePtr loopScope = childScope(forIn, scope);
 
-    TypePackId iterator = checkPack(scope, forIn->values);
+    TypePackId iterator = checkPack(scope, forIn->values).tp;
 
     std::vector<TypeId> variableTypes;
     variableTypes.reserve(forIn->vars.size);
@@ -489,7 +489,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatFunction* funct
     }
     else if (AstExprIndexName* indexName = function->name->as<AstExprIndexName>())
     {
-        TypeId containingTableType = check(scope, indexName->expr);
+        TypeId containingTableType = check(scope, indexName->expr).ty;
 
         functionType = arena->addType(BlockedTypeVar{});
 
@@ -531,7 +531,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatReturn* ret)
     for (TypeId ty : scope->returnType)
         expectedTypes.push_back(ty);
 
-    TypePackId exprTypes = checkPack(scope, ret->list, expectedTypes);
+    TypePackId exprTypes = checkPack(scope, ret->list, expectedTypes).tp;
     addConstraint(scope, ret->location, PackSubtypeConstraint{exprTypes, scope->returnType});
 }
 
@@ -545,7 +545,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatBlock* block)
 void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatAssign* assign)
 {
     TypePackId varPackId = checkLValues(scope, assign->vars);
-    TypePackId valuePack = checkPack(scope, assign->values);
+    TypePackId valuePack = checkPack(scope, assign->values).tp;
 
     addConstraint(scope, assign->location, PackSubtypeConstraint{valuePack, varPackId});
 }
@@ -732,7 +732,6 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatDeclareClass* d
 
 void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatDeclareFunction* global)
 {
-
     std::vector<std::pair<Name, GenericTypeDefinition>> generics = createGenerics(scope, global->generics);
     std::vector<std::pair<Name, GenericTypePackDefinition>> genericPacks = createGenericPacks(scope, global->genericPacks);
 
@@ -779,7 +778,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatError* error)
         check(scope, expr);
 }
 
-TypePackId ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstArray<AstExpr*> exprs, const std::vector<TypeId>& expectedTypes)
+InferencePack ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstArray<AstExpr*> exprs, const std::vector<TypeId>& expectedTypes)
 {
     std::vector<TypeId> head;
     std::optional<TypePackId> tail;
@@ -792,201 +791,180 @@ TypePackId ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstArray<Ast
             std::optional<TypeId> expectedType;
             if (i < expectedTypes.size())
                 expectedType = expectedTypes[i];
-            head.push_back(check(scope, expr));
+            head.push_back(check(scope, expr).ty);
         }
         else
         {
             std::vector<TypeId> expectedTailTypes;
             if (i < expectedTypes.size())
                 expectedTailTypes.assign(begin(expectedTypes) + i, end(expectedTypes));
-            tail = checkPack(scope, expr, expectedTailTypes);
+            tail = checkPack(scope, expr, expectedTailTypes).tp;
         }
     }
 
     if (head.empty() && tail)
-        return *tail;
+        return InferencePack{*tail};
     else
-        return arena->addTypePack(TypePack{std::move(head), tail});
+        return InferencePack{arena->addTypePack(TypePack{std::move(head), tail})};
 }
 
-TypePackId ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstExpr* expr, const std::vector<TypeId>& expectedTypes)
+InferencePack ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstExpr* expr, const std::vector<TypeId>& expectedTypes)
 {
     RecursionCounter counter{&recursionCount};
 
     if (recursionCount >= FInt::LuauCheckRecursionLimit)
     {
         reportCodeTooComplex(expr->location);
-        return singletonTypes->errorRecoveryTypePack();
+        return InferencePack{singletonTypes->errorRecoveryTypePack()};
     }
 
-    TypePackId result = nullptr;
+    InferencePack result;
 
     if (AstExprCall* call = expr->as<AstExprCall>())
-    {
-        TypeId fnType = check(scope, call->func);
-        const size_t constraintIndex = scope->constraints.size();
-        const size_t scopeIndex = scopes.size();
-
-        std::vector<TypeId> args;
-
-        for (AstExpr* arg : call->args)
-        {
-            args.push_back(check(scope, arg));
-        }
-
-        // TODO self
-
-        if (matchSetmetatable(*call))
-        {
-            LUAU_ASSERT(args.size() == 2);
-            TypeId target = args[0];
-            TypeId mt = args[1];
-
-            MetatableTypeVar mtv{target, mt};
-            TypeId resultTy = arena->addType(mtv);
-            result = arena->addTypePack({resultTy});
-        }
-        else
-        {
-            const size_t constraintEndIndex = scope->constraints.size();
-            const size_t scopeEndIndex = scopes.size();
-
-            astOriginalCallTypes[call->func] = fnType;
-
-            TypeId instantiatedType = arena->addType(BlockedTypeVar{});
-            // TODO: How do expectedTypes play into this?  Do they?
-            TypePackId rets = arena->addTypePack(BlockedTypePack{});
-            TypePackId argPack = arena->addTypePack(TypePack{args, {}});
-            FunctionTypeVar ftv(TypeLevel{}, scope.get(), argPack, rets);
-            TypeId inferredFnType = arena->addType(ftv);
-
-            scope->unqueuedConstraints.push_back(
-                std::make_unique<Constraint>(NotNull{scope.get()}, call->func->location, InstantiationConstraint{instantiatedType, fnType}));
-            NotNull<const Constraint> ic(scope->unqueuedConstraints.back().get());
-
-            scope->unqueuedConstraints.push_back(
-                std::make_unique<Constraint>(NotNull{scope.get()}, call->func->location, SubtypeConstraint{inferredFnType, instantiatedType}));
-            NotNull<Constraint> sc(scope->unqueuedConstraints.back().get());
-
-            // We force constraints produced by checking function arguments to wait
-            // until after we have resolved the constraint on the function itself.
-            // This ensures, for instance, that we start inferring the contents of
-            // lambdas under the assumption that their arguments and return types
-            // will be compatible with the enclosing function call.
-            for (size_t ci = constraintIndex; ci < constraintEndIndex; ++ci)
-                scope->constraints[ci]->dependencies.push_back(sc);
-
-            for (size_t si = scopeIndex; si < scopeEndIndex; ++si)
-            {
-                for (auto& c : scopes[si].second->constraints)
-                {
-                    c->dependencies.push_back(sc);
-                }
-            }
-
-            addConstraint(scope, call->func->location,
-                FunctionCallConstraint{
-                    {ic, sc},
-                    fnType,
-                    argPack,
-                    rets,
-                    call,
-                });
-
-            result = rets;
-        }
-    }
+        result = {checkPack(scope, call, expectedTypes)};
     else if (AstExprVarargs* varargs = expr->as<AstExprVarargs>())
     {
         if (scope->varargPack)
-            result = *scope->varargPack;
+            result = InferencePack{*scope->varargPack};
         else
-            result = singletonTypes->errorRecoveryTypePack();
+            result = InferencePack{singletonTypes->errorRecoveryTypePack()};
     }
     else
     {
         std::optional<TypeId> expectedType;
         if (!expectedTypes.empty())
             expectedType = expectedTypes[0];
-        TypeId t = check(scope, expr, expectedType);
-        result = arena->addTypePack({t});
+        TypeId t = check(scope, expr, expectedType).ty;
+        result = InferencePack{arena->addTypePack({t})};
     }
 
-    LUAU_ASSERT(result);
-    astTypePacks[expr] = result;
+    LUAU_ASSERT(result.tp);
+    astTypePacks[expr] = result.tp;
     return result;
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType)
+InferencePack ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstExprCall* call, const std::vector<TypeId>& expectedTypes)
+{
+    TypeId fnType = check(scope, call->func).ty;
+    const size_t constraintIndex = scope->constraints.size();
+    const size_t scopeIndex = scopes.size();
+
+    std::vector<TypeId> args;
+
+    for (AstExpr* arg : call->args)
+    {
+        args.push_back(check(scope, arg).ty);
+    }
+
+    // TODO self
+
+    if (matchSetmetatable(*call))
+    {
+        LUAU_ASSERT(args.size() == 2);
+        TypeId target = args[0];
+        TypeId mt = args[1];
+
+        AstExpr* targetExpr = call->args.data[0];
+
+        MetatableTypeVar mtv{target, mt};
+        TypeId resultTy = arena->addType(mtv);
+
+        if (AstExprLocal* targetLocal = targetExpr->as<AstExprLocal>())
+            scope->bindings[targetLocal->local].typeId = resultTy;
+
+        return InferencePack{arena->addTypePack({resultTy})};
+    }
+    else
+    {
+        const size_t constraintEndIndex = scope->constraints.size();
+        const size_t scopeEndIndex = scopes.size();
+
+        astOriginalCallTypes[call->func] = fnType;
+
+        TypeId instantiatedType = arena->addType(BlockedTypeVar{});
+        // TODO: How do expectedTypes play into this?  Do they?
+        TypePackId rets = arena->addTypePack(BlockedTypePack{});
+        TypePackId argPack = arena->addTypePack(TypePack{args, {}});
+        FunctionTypeVar ftv(TypeLevel{}, scope.get(), argPack, rets);
+        TypeId inferredFnType = arena->addType(ftv);
+
+        scope->unqueuedConstraints.push_back(
+            std::make_unique<Constraint>(NotNull{scope.get()}, call->func->location, InstantiationConstraint{instantiatedType, fnType}));
+        NotNull<const Constraint> ic(scope->unqueuedConstraints.back().get());
+
+        scope->unqueuedConstraints.push_back(
+            std::make_unique<Constraint>(NotNull{scope.get()}, call->func->location, SubtypeConstraint{inferredFnType, instantiatedType}));
+        NotNull<Constraint> sc(scope->unqueuedConstraints.back().get());
+
+        // We force constraints produced by checking function arguments to wait
+        // until after we have resolved the constraint on the function itself.
+        // This ensures, for instance, that we start inferring the contents of
+        // lambdas under the assumption that their arguments and return types
+        // will be compatible with the enclosing function call.
+        for (size_t ci = constraintIndex; ci < constraintEndIndex; ++ci)
+            scope->constraints[ci]->dependencies.push_back(sc);
+
+        for (size_t si = scopeIndex; si < scopeEndIndex; ++si)
+        {
+            for (auto& c : scopes[si].second->constraints)
+            {
+                c->dependencies.push_back(sc);
+            }
+        }
+
+        addConstraint(scope, call->func->location,
+            FunctionCallConstraint{
+                {ic, sc},
+                fnType,
+                argPack,
+                rets,
+                call,
+            });
+
+        return InferencePack{rets};
+    }
+}
+
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType)
 {
     RecursionCounter counter{&recursionCount};
 
     if (recursionCount >= FInt::LuauCheckRecursionLimit)
     {
         reportCodeTooComplex(expr->location);
-        return singletonTypes->errorRecoveryType();
+        return Inference{singletonTypes->errorRecoveryType()};
     }
 
-    TypeId result = nullptr;
+    Inference result;
 
     if (auto group = expr->as<AstExprGroup>())
         result = check(scope, group->expr, expectedType);
     else if (auto stringExpr = expr->as<AstExprConstantString>())
-    {
-        if (expectedType)
-        {
-            const TypeId expectedTy = follow(*expectedType);
-            if (get<BlockedTypeVar>(expectedTy) || get<PendingExpansionTypeVar>(expectedTy))
-            {
-                result = arena->addType(BlockedTypeVar{});
-                TypeId singletonType = arena->addType(SingletonTypeVar(StringSingleton{std::string(stringExpr->value.data, stringExpr->value.size)}));
-                addConstraint(scope, expr->location, PrimitiveTypeConstraint{result, expectedTy, singletonType, singletonTypes->stringType});
-            }
-            else if (maybeSingleton(expectedTy))
-                result = arena->addType(SingletonTypeVar{StringSingleton{std::string{stringExpr->value.data, stringExpr->value.size}}});
-            else
-                result = singletonTypes->stringType;
-        }
-        else
-            result = singletonTypes->stringType;
-    }
+        result = check(scope, stringExpr, expectedType);
     else if (expr->is<AstExprConstantNumber>())
-        result = singletonTypes->numberType;
+        result = Inference{singletonTypes->numberType};
     else if (auto boolExpr = expr->as<AstExprConstantBool>())
-    {
-        if (expectedType)
-        {
-            const TypeId expectedTy = follow(*expectedType);
-            const TypeId singletonType = boolExpr->value ? singletonTypes->trueType : singletonTypes->falseType;
-
-            if (get<BlockedTypeVar>(expectedTy) || get<PendingExpansionTypeVar>(expectedTy))
-            {
-                result = arena->addType(BlockedTypeVar{});
-                addConstraint(scope, expr->location, PrimitiveTypeConstraint{result, expectedTy, singletonType, singletonTypes->booleanType});
-            }
-            else if (maybeSingleton(expectedTy))
-                result = singletonType;
-            else
-                result = singletonTypes->booleanType;
-        }
-        else
-            result = singletonTypes->booleanType;
-    }
+        result = check(scope, boolExpr, expectedType);
     else if (expr->is<AstExprConstantNil>())
-        result = singletonTypes->nilType;
+        result = Inference{singletonTypes->nilType};
     else if (auto local = expr->as<AstExprLocal>())
         result = check(scope, local);
     else if (auto global = expr->as<AstExprGlobal>())
         result = check(scope, global);
     else if (expr->is<AstExprVarargs>())
         result = flattenPack(scope, expr->location, checkPack(scope, expr));
-    else if (expr->is<AstExprCall>())
-        result = flattenPack(scope, expr->location, checkPack(scope, expr)); // TODO: needs predicates too
+    else if (auto call = expr->as<AstExprCall>())
+    {
+        std::vector<TypeId> expectedTypes;
+        if (expectedType)
+            expectedTypes.push_back(*expectedType);
+        result = flattenPack(scope, expr->location, checkPack(scope, call, expectedTypes)); // TODO: needs predicates too
+    }
     else if (auto a = expr->as<AstExprFunction>())
     {
         FunctionSignature sig = checkFunctionSignature(scope, a);
         checkFunctionBody(sig.bodyScope, a);
-        return sig.signature;
+        return Inference{sig.signature};
     }
     else if (auto indexName = expr->as<AstExprIndexName>())
         result = check(scope, indexName);
@@ -1008,20 +986,63 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::
         for (AstExpr* subExpr : err->expressions)
             check(scope, subExpr);
 
-        result = singletonTypes->errorRecoveryType();
+        result = Inference{singletonTypes->errorRecoveryType()};
     }
     else
     {
         LUAU_ASSERT(0);
-        result = freshType(scope);
+        result = Inference{freshType(scope)};
     }
 
-    LUAU_ASSERT(result);
-    astTypes[expr] = result;
+    LUAU_ASSERT(result.ty);
+    astTypes[expr] = result.ty;
     return result;
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* local)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType)
+{
+    if (expectedType)
+    {
+        const TypeId expectedTy = follow(*expectedType);
+        if (get<BlockedTypeVar>(expectedTy) || get<PendingExpansionTypeVar>(expectedTy))
+        {
+            TypeId ty = arena->addType(BlockedTypeVar{});
+            TypeId singletonType = arena->addType(SingletonTypeVar(StringSingleton{std::string(string->value.data, string->value.size)}));
+            addConstraint(scope, string->location, PrimitiveTypeConstraint{ty, expectedTy, singletonType, singletonTypes->stringType});
+            return Inference{ty};
+        }
+        else if (maybeSingleton(expectedTy))
+            return Inference{arena->addType(SingletonTypeVar{StringSingleton{std::string{string->value.data, string->value.size}}})};
+
+        return Inference{singletonTypes->stringType};
+    }
+
+    return Inference{singletonTypes->stringType};
+}
+
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantBool* boolExpr, std::optional<TypeId> expectedType)
+{
+    if (expectedType)
+    {
+        const TypeId expectedTy = follow(*expectedType);
+        const TypeId singletonType = boolExpr->value ? singletonTypes->trueType : singletonTypes->falseType;
+
+        if (get<BlockedTypeVar>(expectedTy) || get<PendingExpansionTypeVar>(expectedTy))
+        {
+            TypeId ty = arena->addType(BlockedTypeVar{});
+            addConstraint(scope, boolExpr->location, PrimitiveTypeConstraint{ty, expectedTy, singletonType, singletonTypes->booleanType});
+            return Inference{ty};
+        }
+        else if (maybeSingleton(expectedTy))
+            return Inference{singletonType};
+
+        return Inference{singletonTypes->booleanType};
+    }
+
+    return Inference{singletonTypes->booleanType};
+}
+
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* local)
 {
     std::optional<TypeId> resultTy;
 
@@ -1035,26 +1056,26 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* local)
     }
 
     if (!resultTy)
-        return singletonTypes->errorRecoveryType(); // TODO: replace with ice, locals should never exist before its definition.
+        return Inference{singletonTypes->errorRecoveryType()}; // TODO: replace with ice, locals should never exist before its definition.
 
-    return *resultTy;
+    return Inference{*resultTy};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprGlobal* global)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprGlobal* global)
 {
     if (std::optional<TypeId> ty = scope->lookup(global->name))
-        return *ty;
+        return Inference{*ty};
 
     /* prepopulateGlobalScope() has already added all global functions to the environment by this point, so any
      * global that is not already in-scope is definitely an unknown symbol.
      */
     reportError(global->location, UnknownSymbol{global->name.value});
-    return singletonTypes->errorRecoveryType();
+    return Inference{singletonTypes->errorRecoveryType()};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexName* indexName)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexName* indexName)
 {
-    TypeId obj = check(scope, indexName->expr);
+    TypeId obj = check(scope, indexName->expr).ty;
     TypeId result = freshType(scope);
 
     TableTypeVar::Props props{{indexName->index.value, Property{result}}};
@@ -1065,13 +1086,13 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexName* in
 
     addConstraint(scope, indexName->expr->location, SubtypeConstraint{obj, expectedTableType});
 
-    return result;
+    return Inference{result};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexExpr* indexExpr)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexExpr* indexExpr)
 {
-    TypeId obj = check(scope, indexExpr->expr);
-    TypeId indexType = check(scope, indexExpr->index);
+    TypeId obj = check(scope, indexExpr->expr).ty;
+    TypeId indexType = check(scope, indexExpr->index).ty;
 
     TypeId result = freshType(scope);
 
@@ -1081,61 +1102,49 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexExpr* in
 
     addConstraint(scope, indexExpr->expr->location, SubtypeConstraint{obj, tableType});
 
-    return result;
+    return Inference{result};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprUnary* unary)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprUnary* unary)
 {
-    TypeId operandType = check_(scope, unary);
+    TypeId operandType = check(scope, unary->expr).ty;
     TypeId resultType = arena->addType(BlockedTypeVar{});
     addConstraint(scope, unary->location, UnaryConstraint{unary->op, operandType, resultType});
-    return resultType;
+    return Inference{resultType};
 }
 
-TypeId ConstraintGraphBuilder::check_(const ScopePtr& scope, AstExprUnary* unary)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType)
 {
-    if (unary->op == AstExprUnary::Not)
-    {
-        TypeId ty = check(scope, unary->expr, std::nullopt);
-
-        return ty;
-    }
-
-    return check(scope, unary->expr);
-}
-
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType)
-{
-    TypeId leftType = check(scope, binary->left, expectedType);
-    TypeId rightType = check(scope, binary->right, expectedType);
+    TypeId leftType = check(scope, binary->left, expectedType).ty;
+    TypeId rightType = check(scope, binary->right, expectedType).ty;
 
     TypeId resultType = arena->addType(BlockedTypeVar{});
     addConstraint(scope, binary->location, BinaryConstraint{binary->op, leftType, rightType, resultType});
-    return resultType;
+    return Inference{resultType};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType)
 {
     check(scope, ifElse->condition);
 
-    TypeId thenType = check(scope, ifElse->trueExpr, expectedType);
-    TypeId elseType = check(scope, ifElse->falseExpr, expectedType);
+    TypeId thenType = check(scope, ifElse->trueExpr, expectedType).ty;
+    TypeId elseType = check(scope, ifElse->falseExpr, expectedType).ty;
 
     if (ifElse->hasElse)
     {
         TypeId resultType = expectedType ? *expectedType : freshType(scope);
         addConstraint(scope, ifElse->trueExpr->location, SubtypeConstraint{thenType, resultType});
         addConstraint(scope, ifElse->falseExpr->location, SubtypeConstraint{elseType, resultType});
-        return resultType;
+        return Inference{resultType};
     }
 
-    return thenType;
+    return Inference{thenType};
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert)
 {
     check(scope, typeAssert->expr, std::nullopt);
-    return resolveType(scope, typeAssert->annotation);
+    return Inference{resolveType(scope, typeAssert->annotation)};
 }
 
 TypePackId ConstraintGraphBuilder::checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs)
@@ -1286,22 +1295,22 @@ TypeId ConstraintGraphBuilder::checkLValue(const ScopePtr& scope, AstExpr* expr)
 
     auto dottedPath = extractDottedName(expr);
     if (!dottedPath)
-        return check(scope, expr);
+        return check(scope, expr).ty;
     const auto [sym, segments] = std::move(*dottedPath);
 
     if (!sym.local)
-        return check(scope, expr);
+        return check(scope, expr).ty;
 
     auto lookupResult = scope->lookupEx(sym);
     if (!lookupResult)
-        return check(scope, expr);
+        return check(scope, expr).ty;
     const auto [ty, symbolScope] = std::move(*lookupResult);
 
     TypeId replaceTy = arena->freshType(scope.get());
 
     std::optional<TypeId> updatedType = updateTheTableType(arena, ty, segments, replaceTy);
     if (!updatedType)
-        return check(scope, expr);
+        return check(scope, expr).ty;
 
     std::optional<DefId> def = dfg->getDef(sym);
     LUAU_ASSERT(def);
@@ -1310,7 +1319,7 @@ TypeId ConstraintGraphBuilder::checkLValue(const ScopePtr& scope, AstExpr* expr)
     return replaceTy;
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType)
 {
     TypeId ty = arena->addType(TableTypeVar{});
     TableTypeVar* ttv = getMutable<TableTypeVar>(ty);
@@ -1344,16 +1353,14 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTable* expr,
             }
         }
 
-        TypeId itemTy = check(scope, item.value, expectedValueType);
-        if (get<ErrorTypeVar>(follow(itemTy)))
-            return ty;
+        TypeId itemTy = check(scope, item.value, expectedValueType).ty;
 
         if (item.key)
         {
             // Even though we don't need to use the type of the item's key if
             // it's a string constant, we still want to check it to populate
             // astTypes.
-            TypeId keyTy = check(scope, item.key);
+            TypeId keyTy = check(scope, item.key).ty;
 
             if (AstExprConstantString* key = item.key->as<AstExprConstantString>())
             {
@@ -1373,7 +1380,7 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTable* expr,
         }
     }
 
-    return ty;
+    return Inference{ty};
 }
 
 ConstraintGraphBuilder::FunctionSignature ConstraintGraphBuilder::checkFunctionSignature(const ScopePtr& parent, AstExprFunction* fn)
@@ -1541,9 +1548,18 @@ TypeId ConstraintGraphBuilder::resolveType(const ScopePtr& scope, AstType* ty, b
             }
         }
 
-        std::optional<TypeFun> alias = scope->lookupType(ref->name.value);
+        std::optional<TypeFun> alias;
 
-        if (alias.has_value() || ref->prefix.has_value())
+        if (ref->prefix.has_value())
+        {
+            alias = scope->lookupImportedType(ref->prefix->value, ref->name.value);
+        }
+        else
+        {
+            alias = scope->lookupType(ref->name.value);
+        }
+
+        if (alias.has_value())
         {
             // If the alias is not generic, we don't need to set up a blocked
             // type and an instantiation constraint.
@@ -1586,7 +1602,11 @@ TypeId ConstraintGraphBuilder::resolveType(const ScopePtr& scope, AstType* ty, b
         }
         else
         {
-            reportError(ty->location, UnknownSymbol{ref->name.value, UnknownSymbol::Context::Type});
+            std::string typeName;
+            if (ref->prefix)
+                typeName = std::string(ref->prefix->value) + ".";
+            typeName += ref->name.value;
+
             result = singletonTypes->errorRecoveryType();
         }
     }
@@ -1685,7 +1705,7 @@ TypeId ConstraintGraphBuilder::resolveType(const ScopePtr& scope, AstType* ty, b
     else if (auto tof = ty->as<AstTypeTypeof>())
     {
         // TODO: Recursion limit.
-        TypeId exprType = check(scope, tof->expr);
+        TypeId exprType = check(scope, tof->expr).ty;
         result = exprType;
     }
     else if (auto unionAnnotation = ty->as<AstTypeUnion>())
@@ -1694,7 +1714,7 @@ TypeId ConstraintGraphBuilder::resolveType(const ScopePtr& scope, AstType* ty, b
         for (AstType* part : unionAnnotation->types)
         {
             // TODO: Recursion limit.
-            parts.push_back(resolveType(scope, part));
+            parts.push_back(resolveType(scope, part, topLevel));
         }
 
         result = arena->addType(UnionTypeVar{parts});
@@ -1705,7 +1725,7 @@ TypeId ConstraintGraphBuilder::resolveType(const ScopePtr& scope, AstType* ty, b
         for (AstType* part : intersectionAnnotation->types)
         {
             // TODO: Recursion limit.
-            parts.push_back(resolveType(scope, part));
+            parts.push_back(resolveType(scope, part, topLevel));
         }
 
         result = arena->addType(IntersectionTypeVar{parts});
@@ -1795,10 +1815,7 @@ std::vector<std::pair<Name, GenericTypeDefinition>> ConstraintGraphBuilder::crea
         if (generic.defaultValue)
             defaultTy = resolveType(scope, generic.defaultValue);
 
-        result.push_back({generic.name.value, GenericTypeDefinition{
-                                                  genericTy,
-                                                  defaultTy,
-                                              }});
+        result.push_back({generic.name.value, GenericTypeDefinition{genericTy, defaultTy}});
     }
 
     return result;
@@ -1816,19 +1833,17 @@ std::vector<std::pair<Name, GenericTypePackDefinition>> ConstraintGraphBuilder::
         if (generic.defaultValue)
             defaultTy = resolveTypePack(scope, generic.defaultValue);
 
-        result.push_back({generic.name.value, GenericTypePackDefinition{
-                                                  genericTy,
-                                                  defaultTy,
-                                              }});
+        result.push_back({generic.name.value, GenericTypePackDefinition{genericTy, defaultTy}});
     }
 
     return result;
 }
 
-TypeId ConstraintGraphBuilder::flattenPack(const ScopePtr& scope, Location location, TypePackId tp)
+Inference ConstraintGraphBuilder::flattenPack(const ScopePtr& scope, Location location, InferencePack pack)
 {
+    auto [tp] = pack;
     if (auto f = first(tp))
-        return *f;
+        return Inference{*f};
 
     TypeId typeResult = freshType(scope);
     TypePack onePack{{typeResult}, freshTypePack(scope)};
@@ -1836,7 +1851,7 @@ TypeId ConstraintGraphBuilder::flattenPack(const ScopePtr& scope, Location locat
 
     addConstraint(scope, location, PackSubtypeConstraint{tp, oneTypePack});
 
-    return typeResult;
+    return Inference{typeResult};
 }
 
 void ConstraintGraphBuilder::reportError(Location location, TypeErrorData err)

Analysis/src/ConstraintSolver.cpp

@@ -544,6 +544,7 @@ bool ConstraintSolver::tryDispatch(const UnaryConstraint& c, NotNull<const Const
     }
     case AstExprUnary::Len:
     {
+        // __len must return a number.
         asMutable(c.resultType)->ty.emplace<BoundTypeVar>(singletonTypes->numberType);
         return true;
     }
@@ -552,13 +553,46 @@ bool ConstraintSolver::tryDispatch(const UnaryConstraint& c, NotNull<const Const
         if (isNumber(operandType) || get<AnyTypeVar>(operandType) || get<ErrorTypeVar>(operandType))
         {
             asMutable(c.resultType)->ty.emplace<BoundTypeVar>(c.operandType);
-            return true;
         }
-        break;
+        else if (std::optional<TypeId> mm = findMetatableEntry(singletonTypes, errors, operandType, "__unm", constraint->location))
+        {
+            const FunctionTypeVar* ftv = get<FunctionTypeVar>(follow(*mm));
+
+            if (!ftv)
+            {
+                if (std::optional<TypeId> callMm = findMetatableEntry(singletonTypes, errors, follow(*mm), "__call", constraint->location))
+                {
+                    ftv = get<FunctionTypeVar>(follow(*callMm));
+                }
+            }
+
+            if (!ftv)
+            {
+                asMutable(c.resultType)->ty.emplace<BoundTypeVar>(singletonTypes->errorRecoveryType());
+                return true;
+            }
+
+            TypePackId argsPack = arena->addTypePack({operandType});
+            unify(ftv->argTypes, argsPack, constraint->scope);
+
+            TypeId result = singletonTypes->errorRecoveryType();
+            if (ftv)
+            {
+                result = first(ftv->retTypes).value_or(singletonTypes->errorRecoveryType());
+            }
+
+            asMutable(c.resultType)->ty.emplace<BoundTypeVar>(result);
+        }
+        else
+        {
+            asMutable(c.resultType)->ty.emplace<BoundTypeVar>(singletonTypes->errorRecoveryType());
+        }
+
+        return true;
     }
     }
 
-    LUAU_ASSERT(false); // TODO metatable handling
+    LUAU_ASSERT(false);
     return false;
 }
 
@@ -862,6 +896,10 @@ bool ConstraintSolver::tryDispatch(const NameConstraint& c, NotNull<const Constr
         ttv->name = c.name;
     else if (MetatableTypeVar* mtv = getMutable<MetatableTypeVar>(target))
         mtv->syntheticName = c.name;
+    else if (get<IntersectionTypeVar>(target) || get<UnionTypeVar>(target))
+    {
+        // nothing (yet)
+    }
     else
         return block(c.namedType, constraint);
 

Analysis/src/Error.cpp

@@ -7,6 +7,8 @@
 
 #include <stdexcept>
 
+LUAU_FASTFLAGVARIABLE(LuauIceExceptionInheritanceChange, false)
+
 static std::string wrongNumberOfArgsString(
     size_t expectedCount, std::optional<size_t> maximumCount, size_t actualCount, const char* argPrefix = nullptr, bool isVariadic = false)
 {
@@ -460,6 +462,11 @@ struct ErrorConverter
     {
         return "Code is too complex to typecheck! Consider simplifying the code around this area";
     }
+
+    std::string operator()(const TypePackMismatch& e) const
+    {
+        return "Type pack '" + toString(e.givenTp) + "' could not be converted into '" + toString(e.wantedTp) + "'";
+    }
 };
 
 struct InvalidNameChecker
@@ -718,6 +725,11 @@ bool TypesAreUnrelated::operator==(const TypesAreUnrelated& rhs) const
     return left == rhs.left && right == rhs.right;
 }
 
+bool TypePackMismatch::operator==(const TypePackMismatch& rhs) const
+{
+    return *wantedTp == *rhs.wantedTp && *givenTp == *rhs.givenTp;
+}
+
 std::string toString(const TypeError& error)
 {
     return toString(error, TypeErrorToStringOptions{});
@@ -869,6 +881,11 @@ void copyError(T& e, TypeArena& destArena, CloneState cloneState)
     else if constexpr (std::is_same_v<T, NormalizationTooComplex>)
     {
     }
+    else if constexpr (std::is_same_v<T, TypePackMismatch>)
+    {
+        e.wantedTp = clone(e.wantedTp);
+        e.givenTp = clone(e.givenTp);
+    }
     else
         static_assert(always_false_v<T>, "Non-exhaustive type switch");
 }
@@ -913,4 +930,30 @@ const char* InternalCompilerError::what() const throw()
     return this->message.data();
 }
 
+// TODO: Inline me when LuauIceExceptionInheritanceChange is deleted.
+void throwRuntimeError(const std::string& message)
+{
+    if (FFlag::LuauIceExceptionInheritanceChange)
+    {
+        throw InternalCompilerError(message);
+    }
+    else
+    {
+        throw std::runtime_error(message);
+    }
+}
+
+// TODO: Inline me when LuauIceExceptionInheritanceChange is deleted.
+void throwRuntimeError(const std::string& message, const std::string& moduleName)
+{
+    if (FFlag::LuauIceExceptionInheritanceChange)
+    {
+        throw InternalCompilerError(message, moduleName);
+    }
+    else
+    {
+        throw std::runtime_error(message);
+    }
+}
+
 } // namespace Luau

Analysis/src/Frontend.cpp

@@ -31,6 +31,7 @@ LUAU_FASTINTVARIABLE(LuauAutocompleteCheckTimeoutMs, 100)
 LUAU_FASTFLAGVARIABLE(DebugLuauDeferredConstraintResolution, false)
 LUAU_FASTFLAG(DebugLuauLogSolverToJson);
 LUAU_FASTFLAGVARIABLE(LuauFixMarkDirtyReverseDeps, false)
+LUAU_FASTFLAGVARIABLE(LuauPersistTypesAfterGeneratingDocSyms, false)
 
 namespace Luau
 {
@@ -111,24 +112,57 @@ LoadDefinitionFileResult Frontend::loadDefinitionFile(std::string_view source, c
 
     CloneState cloneState;
 
-    for (const auto& [name, ty] : checkedModule->declaredGlobals)
+    if (FFlag::LuauPersistTypesAfterGeneratingDocSyms)
     {
-        TypeId globalTy = clone(ty, globalTypes, cloneState);
-        std::string documentationSymbol = packageName + "/global/" + name;
-        generateDocumentationSymbols(globalTy, documentationSymbol);
-        globalScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
+        std::vector<TypeId> typesToPersist;
+        typesToPersist.reserve(checkedModule->declaredGlobals.size() + checkedModule->getModuleScope()->exportedTypeBindings.size());
 
-        persist(globalTy);
+        for (const auto& [name, ty] : checkedModule->declaredGlobals)
+        {
+            TypeId globalTy = clone(ty, globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/global/" + name;
+            generateDocumentationSymbols(globalTy, documentationSymbol);
+            globalScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
+
+            typesToPersist.push_back(globalTy);
+        }
+
+        for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+        {
+            TypeFun globalTy = clone(ty, globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/globaltype/" + name;
+            generateDocumentationSymbols(globalTy.type, documentationSymbol);
+            globalScope->exportedTypeBindings[name] = globalTy;
+
+            typesToPersist.push_back(globalTy.type);
+        }
+
+        for (TypeId ty : typesToPersist)
+        {
+            persist(ty);
+        }
     }
-
-    for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+    else
     {
-        TypeFun globalTy = clone(ty, globalTypes, cloneState);
-        std::string documentationSymbol = packageName + "/globaltype/" + name;
-        generateDocumentationSymbols(globalTy.type, documentationSymbol);
-        globalScope->exportedTypeBindings[name] = globalTy;
+        for (const auto& [name, ty] : checkedModule->declaredGlobals)
+        {
+            TypeId globalTy = clone(ty, globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/global/" + name;
+            generateDocumentationSymbols(globalTy, documentationSymbol);
+            globalScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
 
-        persist(globalTy.type);
+            persist(globalTy);
+        }
+
+        for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+        {
+            TypeFun globalTy = clone(ty, globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/globaltype/" + name;
+            generateDocumentationSymbols(globalTy.type, documentationSymbol);
+            globalScope->exportedTypeBindings[name] = globalTy;
+
+            persist(globalTy.type);
+        }
     }
 
     return LoadDefinitionFileResult{true, parseResult, checkedModule};
@@ -160,24 +194,57 @@ LoadDefinitionFileResult loadDefinitionFile(TypeChecker& typeChecker, ScopePtr t
 
     CloneState cloneState;
 
-    for (const auto& [name, ty] : checkedModule->declaredGlobals)
+    if (FFlag::LuauPersistTypesAfterGeneratingDocSyms)
     {
-        TypeId globalTy = clone(ty, typeChecker.globalTypes, cloneState);
-        std::string documentationSymbol = packageName + "/global/" + name;
-        generateDocumentationSymbols(globalTy, documentationSymbol);
-        targetScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
+        std::vector<TypeId> typesToPersist;
+        typesToPersist.reserve(checkedModule->declaredGlobals.size() + checkedModule->getModuleScope()->exportedTypeBindings.size());
 
-        persist(globalTy);
+        for (const auto& [name, ty] : checkedModule->declaredGlobals)
+        {
+            TypeId globalTy = clone(ty, typeChecker.globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/global/" + name;
+            generateDocumentationSymbols(globalTy, documentationSymbol);
+            targetScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
+
+            typesToPersist.push_back(globalTy);
+        }
+
+        for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+        {
+            TypeFun globalTy = clone(ty, typeChecker.globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/globaltype/" + name;
+            generateDocumentationSymbols(globalTy.type, documentationSymbol);
+            targetScope->exportedTypeBindings[name] = globalTy;
+
+            typesToPersist.push_back(globalTy.type);
+        }
+
+        for (TypeId ty : typesToPersist)
+        {
+            persist(ty);
+        }
     }
-
-    for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+    else
     {
-        TypeFun globalTy = clone(ty, typeChecker.globalTypes, cloneState);
-        std::string documentationSymbol = packageName + "/globaltype/" + name;
-        generateDocumentationSymbols(globalTy.type, documentationSymbol);
-        targetScope->exportedTypeBindings[name] = globalTy;
+        for (const auto& [name, ty] : checkedModule->declaredGlobals)
+        {
+            TypeId globalTy = clone(ty, typeChecker.globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/global/" + name;
+            generateDocumentationSymbols(globalTy, documentationSymbol);
+            targetScope->bindings[typeChecker.globalNames.names->getOrAdd(name.c_str())] = {globalTy, Location(), false, {}, documentationSymbol};
 
-        persist(globalTy.type);
+            persist(globalTy);
+        }
+
+        for (const auto& [name, ty] : checkedModule->getModuleScope()->exportedTypeBindings)
+        {
+            TypeFun globalTy = clone(ty, typeChecker.globalTypes, cloneState);
+            std::string documentationSymbol = packageName + "/globaltype/" + name;
+            generateDocumentationSymbols(globalTy.type, documentationSymbol);
+            targetScope->exportedTypeBindings[name] = globalTy;
+
+            persist(globalTy.type);
+        }
     }
 
     return LoadDefinitionFileResult{true, parseResult, checkedModule};
@@ -426,13 +493,13 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
         {
             auto it2 = moduleResolverForAutocomplete.modules.find(name);
             if (it2 == moduleResolverForAutocomplete.modules.end() || it2->second == nullptr)
-                throw std::runtime_error("Frontend::modules does not have data for " + name);
+                throwRuntimeError("Frontend::modules does not have data for " + name, name);
         }
         else
         {
             auto it2 = moduleResolver.modules.find(name);
             if (it2 == moduleResolver.modules.end() || it2->second == nullptr)
-                throw std::runtime_error("Frontend::modules does not have data for " + name);
+                throwRuntimeError("Frontend::modules does not have data for " + name, name);
         }
 
         return CheckResult{
@@ -539,7 +606,7 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
         stats.filesNonstrict += mode == Mode::Nonstrict;
 
         if (module == nullptr)
-            throw std::runtime_error("Frontend::check produced a nullptr module for " + moduleName);
+            throwRuntimeError("Frontend::check produced a nullptr module for " + moduleName, moduleName);
 
         if (!frontendOptions.retainFullTypeGraphs)
         {
@@ -1007,11 +1074,11 @@ SourceModule Frontend::parse(const ModuleName& name, std::string_view src, const
 
     double timestamp = getTimestamp();
 
-    auto parseResult = Luau::Parser::parse(src.data(), src.size(), *sourceModule.names, *sourceModule.allocator, parseOptions);
+    Luau::ParseResult parseResult = Luau::Parser::parse(src.data(), src.size(), *sourceModule.names, *sourceModule.allocator, parseOptions);
 
     stats.timeParse += getTimestamp() - timestamp;
     stats.files++;
-    stats.lines += std::count(src.begin(), src.end(), '\n') + (src.size() && src.back() != '\n');
+    stats.lines += parseResult.lines;
 
     if (!parseResult.errors.empty())
         sourceModule.parseErrors.insert(sourceModule.parseErrors.end(), parseResult.errors.begin(), parseResult.errors.end());

Analysis/src/IostreamHelpers.cpp

@@ -188,6 +188,8 @@ static void errorToString(std::ostream& stream, const T& err)
         stream << "TypesAreUnrelated { left = '" + toString(err.left) + "', right = '" + toString(err.right) + "' }";
     else if constexpr (std::is_same_v<T, NormalizationTooComplex>)
         stream << "NormalizationTooComplex { }";
+    else if constexpr (std::is_same_v<T, TypePackMismatch>)
+        stream << "TypePackMismatch { wanted = '" + toString(err.wantedTp) + "', given = '" + toString(err.givenTp) + "' }";
     else
         static_assert(always_false_v<T>, "Non-exhaustive type switch");
 }

Analysis/src/Normalize.cpp

@@ -7,6 +7,7 @@
 
 #include "Luau/Clone.h"
 #include "Luau/Common.h"
+#include "Luau/TypeVar.h"
 #include "Luau/Unifier.h"
 #include "Luau/VisitTypeVar.h"
 
@@ -18,6 +19,7 @@ LUAU_FASTINTVARIABLE(LuauNormalizeIterationLimit, 1200);
 LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeCombineTableFix, false);
 LUAU_FASTFLAGVARIABLE(LuauTypeNormalization2, false);
+LUAU_FASTFLAGVARIABLE(LuauNegatedStringSingletons, false);
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTFLAG(LuauOverloadedFunctionSubtypingPerf);
@@ -107,12 +109,110 @@ bool TypeIds::operator==(const TypeIds& there) const
     return hash == there.hash && types == there.types;
 }
 
+NormalizedStringType::NormalizedStringType(bool isCofinite, std::optional<std::map<std::string, TypeId>> singletons)
+    : isCofinite(isCofinite)
+    , singletons(std::move(singletons))
+{
+    if (!FFlag::LuauNegatedStringSingletons)
+        LUAU_ASSERT(!isCofinite);
+}
+
+void NormalizedStringType::resetToString()
+{
+    if (FFlag::LuauNegatedStringSingletons)
+    {
+        isCofinite = true;
+        singletons->clear();
+    }
+    else
+        singletons.reset();
+}
+
+void NormalizedStringType::resetToNever()
+{
+    if (FFlag::LuauNegatedStringSingletons)
+    {
+        isCofinite = false;
+        singletons.emplace();
+    }
+    else
+    {
+        if (singletons)
+            singletons->clear();
+        else
+            singletons.emplace();
+    }
+}
+
+bool NormalizedStringType::isNever() const
+{
+    if (FFlag::LuauNegatedStringSingletons)
+        return !isCofinite && singletons->empty();
+    else
+        return singletons && singletons->empty();
+}
+
+bool NormalizedStringType::isString() const
+{
+    if (FFlag::LuauNegatedStringSingletons)
+        return isCofinite && singletons->empty();
+    else
+        return !singletons;
+}
+
+bool NormalizedStringType::isUnion() const
+{
+    if (FFlag::LuauNegatedStringSingletons)
+        return !isCofinite;
+    else
+        return singletons.has_value();
+}
+
+bool NormalizedStringType::isIntersection() const
+{
+    if (FFlag::LuauNegatedStringSingletons)
+        return isCofinite;
+    else
+        return false;
+}
+
+bool NormalizedStringType::includes(const std::string& str) const
+{
+    if (isString())
+        return true;
+    else if (isUnion() && singletons->count(str))
+        return true;
+    else if (isIntersection() && !singletons->count(str))
+        return true;
+    else
+        return false;
+}
+
+const NormalizedStringType NormalizedStringType::never{false, {{}}};
+
+bool isSubtype(const NormalizedStringType& subStr, const NormalizedStringType& superStr)
+{
+    if (subStr.isUnion() && superStr.isUnion())
+    {
+        for (auto [name, ty] : *subStr.singletons)
+        {
+            if (!superStr.singletons->count(name))
+                return false;
+        }
+    }
+    else if (subStr.isString() && superStr.isUnion())
+        return false;
+
+    return true;
+}
+
 NormalizedType::NormalizedType(NotNull<SingletonTypes> singletonTypes)
     : tops(singletonTypes->neverType)
     , booleans(singletonTypes->neverType)
     , errors(singletonTypes->neverType)
     , nils(singletonTypes->neverType)
     , numbers(singletonTypes->neverType)
+    , strings{NormalizedStringType::never}
     , threads(singletonTypes->neverType)
 {
 }
@@ -120,7 +220,7 @@ NormalizedType::NormalizedType(NotNull<SingletonTypes> singletonTypes)
 static bool isInhabited(const NormalizedType& norm)
 {
     return !get<NeverTypeVar>(norm.tops) || !get<NeverTypeVar>(norm.booleans) || !norm.classes.empty() || !get<NeverTypeVar>(norm.errors) ||
-           !get<NeverTypeVar>(norm.nils) || !get<NeverTypeVar>(norm.numbers) || !norm.strings || !norm.strings->empty() ||
+           !get<NeverTypeVar>(norm.nils) || !get<NeverTypeVar>(norm.numbers) || !norm.strings.isNever() ||
            !get<NeverTypeVar>(norm.threads) || norm.functions || !norm.tables.empty() || !norm.tyvars.empty();
 }
 
@@ -183,10 +283,10 @@ static bool isNormalizedNumber(TypeId ty)
 
 static bool isNormalizedString(const NormalizedStringType& ty)
 {
-    if (!ty)
+    if (ty.isString())
         return true;
 
-    for (auto& [str, ty] : *ty)
+    for (auto& [str, ty] : *ty.singletons)
     {
         if (const SingletonTypeVar* stv = get<SingletonTypeVar>(ty))
         {
@@ -317,10 +417,7 @@ void Normalizer::clearNormal(NormalizedType& norm)
     norm.errors = singletonTypes->neverType;
     norm.nils = singletonTypes->neverType;
     norm.numbers = singletonTypes->neverType;
-    if (norm.strings)
-        norm.strings->clear();
-    else
-        norm.strings.emplace();
+    norm.strings.resetToNever();
     norm.threads = singletonTypes->neverType;
     norm.tables.clear();
     norm.functions = std::nullopt;
@@ -495,10 +592,56 @@ void Normalizer::unionClasses(TypeIds& heres, const TypeIds& theres)
 
 void Normalizer::unionStrings(NormalizedStringType& here, const NormalizedStringType& there)
 {
-    if (!there)
-        here.reset();
-    else if (here)
-        here->insert(there->begin(), there->end());
+    if (FFlag::LuauNegatedStringSingletons)
+    {
+        if (there.isString())
+            here.resetToString();
+        else if (here.isUnion() && there.isUnion())
+            here.singletons->insert(there.singletons->begin(), there.singletons->end());
+        else if (here.isUnion() && there.isIntersection())
+        {
+            here.isCofinite = true;
+            for (const auto& pair : *there.singletons)
+            {
+                auto it = here.singletons->find(pair.first);
+                if (it != end(*here.singletons))
+                    here.singletons->erase(it);
+                else
+                    here.singletons->insert(pair);
+            }
+        }
+        else if (here.isIntersection() && there.isUnion())
+        {
+            for (const auto& [name, ty] : *there.singletons)
+                here.singletons->erase(name);
+        }
+        else if (here.isIntersection() && there.isIntersection())
+        {
+            auto iter = begin(*here.singletons);
+            auto endIter = end(*here.singletons);
+
+            while (iter != endIter)
+            {
+                if (!there.singletons->count(iter->first))
+                {
+                    auto eraseIt = iter;
+                    ++iter;
+                    here.singletons->erase(eraseIt);
+                }
+                else
+                    ++iter;
+            }
+        }
+        else
+            LUAU_ASSERT(!"Unreachable");
+    }
+    else
+    {
+        if (there.isString())
+            here.resetToString();
+        else if (here.isUnion())
+            here.singletons->insert(there.singletons->begin(), there.singletons->end());
+    }
 }
 
 std::optional<TypePackId> Normalizer::unionOfTypePacks(TypePackId here, TypePackId there)
@@ -858,7 +1001,7 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
         else if (ptv->type == PrimitiveTypeVar::Number)
             here.numbers = there;
         else if (ptv->type == PrimitiveTypeVar::String)
-            here.strings = std::nullopt;
+            here.strings.resetToString();
         else if (ptv->type == PrimitiveTypeVar::Thread)
             here.threads = there;
         else
@@ -870,12 +1013,33 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
             here.booleans = unionOfBools(here.booleans, there);
         else if (const StringSingleton* sstv = get<StringSingleton>(stv))
         {
-            if (here.strings)
-                here.strings->insert({sstv->value, there});
+            if (FFlag::LuauNegatedStringSingletons)
+            {
+                if (here.strings.isCofinite)
+                {
+                    auto it = here.strings.singletons->find(sstv->value);
+                    if (it != here.strings.singletons->end())
+                        here.strings.singletons->erase(it);
+                }
+                else
+                    here.strings.singletons->insert({sstv->value, there});
+            }
+            else
+            {
+                if (here.strings.isUnion())
+                    here.strings.singletons->insert({sstv->value, there});
+            }
         }
         else
             LUAU_ASSERT(!"Unreachable");
     }
+    else if (const NegationTypeVar* ntv = get<NegationTypeVar>(there))
+    {
+        const NormalizedType* thereNormal = normalize(ntv->ty);
+        NormalizedType tn = negateNormal(*thereNormal);
+        if (!unionNormals(here, tn))
+            return false;
+    }
     else
         LUAU_ASSERT(!"Unreachable");
 
@@ -887,6 +1051,159 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
     return true;
 }
 
+// ------- Negations
+
+NormalizedType Normalizer::negateNormal(const NormalizedType& here)
+{
+    NormalizedType result{singletonTypes};
+    if (!get<NeverTypeVar>(here.tops))
+    {
+        // The negation of unknown or any is never.  Easy.
+        return result;
+    }
+
+    if (!get<NeverTypeVar>(here.errors))
+    {
+        // Negating an error yields the same error.
+        result.errors = here.errors;
+        return result;
+    }
+
+    if (get<NeverTypeVar>(here.booleans))
+        result.booleans = singletonTypes->booleanType;
+    else if (get<PrimitiveTypeVar>(here.booleans))
+        result.booleans = singletonTypes->neverType;
+    else if (auto stv = get<SingletonTypeVar>(here.booleans))
+    {
+        auto boolean = get<BooleanSingleton>(stv);
+        LUAU_ASSERT(boolean != nullptr);
+        if (boolean->value)
+            result.booleans = singletonTypes->falseType;
+        else
+            result.booleans = singletonTypes->trueType;
+    }
+
+    result.classes = negateAll(here.classes);
+    result.nils = get<NeverTypeVar>(here.nils) ? singletonTypes->nilType : singletonTypes->neverType;
+    result.numbers = get<NeverTypeVar>(here.numbers) ? singletonTypes->numberType : singletonTypes->neverType;
+
+    result.strings = here.strings;
+    result.strings.isCofinite = !result.strings.isCofinite;
+
+    result.threads = get<NeverTypeVar>(here.threads) ? singletonTypes->threadType : singletonTypes->neverType;
+
+    // TODO: negating tables
+    // TODO: negating functions
+    // TODO: negating tyvars?
+    
+    return result;
+}
+
+TypeIds Normalizer::negateAll(const TypeIds& theres)
+{
+    TypeIds tys;
+    for (TypeId there : theres)
+        tys.insert(negate(there));
+    return tys;
+}
+
+TypeId Normalizer::negate(TypeId there)
+{
+    there = follow(there);
+    if (get<AnyTypeVar>(there))
+        return there;
+    else if (get<UnknownTypeVar>(there))
+        return singletonTypes->neverType;
+    else if (get<NeverTypeVar>(there))
+        return singletonTypes->unknownType;
+    else if (auto ntv = get<NegationTypeVar>(there))
+        return ntv->ty; // TODO: do we want to normalize this?
+    else if (auto utv = get<UnionTypeVar>(there))
+    {
+        std::vector<TypeId> parts;
+        for (TypeId option : utv)
+            parts.push_back(negate(option));
+        return arena->addType(IntersectionTypeVar{std::move(parts)});
+    }
+    else if (auto itv = get<IntersectionTypeVar>(there))
+    {
+        std::vector<TypeId> options;
+        for (TypeId part : itv)
+            options.push_back(negate(part));
+        return arena->addType(UnionTypeVar{std::move(options)});
+    }
+    else
+        return there;
+}
+
+void Normalizer::subtractPrimitive(NormalizedType& here, TypeId ty)
+{
+    const PrimitiveTypeVar* ptv = get<PrimitiveTypeVar>(follow(ty));
+    LUAU_ASSERT(ptv);
+    switch (ptv->type)
+    {
+        case PrimitiveTypeVar::NilType:
+            here.nils = singletonTypes->neverType;
+            break;
+        case PrimitiveTypeVar::Boolean:
+            here.booleans = singletonTypes->neverType;
+            break;
+        case PrimitiveTypeVar::Number:
+            here.numbers = singletonTypes->neverType;
+            break;
+        case PrimitiveTypeVar::String:
+            here.strings.resetToNever();
+            break;
+        case PrimitiveTypeVar::Thread:
+            here.threads = singletonTypes->neverType;
+            break;
+    }
+}
+
+void Normalizer::subtractSingleton(NormalizedType& here, TypeId ty)
+{
+    LUAU_ASSERT(FFlag::LuauNegatedStringSingletons);
+
+    const SingletonTypeVar* stv = get<SingletonTypeVar>(ty);
+    LUAU_ASSERT(stv);
+
+    if (const StringSingleton* ss = get<StringSingleton>(stv))
+    {
+        if (here.strings.isCofinite)
+            here.strings.singletons->insert({ss->value, ty});
+        else
+        {
+            auto it = here.strings.singletons->find(ss->value);
+            if (it != here.strings.singletons->end())
+                here.strings.singletons->erase(it);
+        }
+    }
+    else if (const BooleanSingleton* bs = get<BooleanSingleton>(stv))
+    {
+        if (get<NeverTypeVar>(here.booleans))
+        {
+            // Nothing
+        }
+        else if (get<PrimitiveTypeVar>(here.booleans))
+            here.booleans = bs->value ? singletonTypes->falseType : singletonTypes->trueType;
+        else if (auto hereSingleton = get<SingletonTypeVar>(here.booleans))
+        {
+            const BooleanSingleton* hereBooleanSingleton = get<BooleanSingleton>(hereSingleton);
+            LUAU_ASSERT(hereBooleanSingleton);
+
+            // Crucial subtlety: ty (and thus bs) are the value that is being
+            // negated out. We therefore reduce to never when the values match,
+            // rather than when they differ.
+            if (bs->value == hereBooleanSingleton->value)
+                here.booleans = singletonTypes->neverType;
+        }
+        else
+            LUAU_ASSERT(!"Unreachable");
+    }
+    else
+        LUAU_ASSERT(!"Unreachable");
+}
+
 // ------- Normalizing intersections
 TypeId Normalizer::intersectionOfTops(TypeId here, TypeId there)
 {
@@ -971,17 +1288,17 @@ void Normalizer::intersectClassesWithClass(TypeIds& heres, TypeId there)
 
 void Normalizer::intersectStrings(NormalizedStringType& here, const NormalizedStringType& there)
 {
-    if (!there)
+    if (there.isString())
         return;
-    if (!here)
-        here.emplace();
+    if (here.isString())
+        here.resetToNever();
 
-    for (auto it = here->begin(); it != here->end();)
+    for (auto it = here.singletons->begin(); it != here.singletons->end();)
     {
-        if (there->count(it->first))
+        if (there.singletons->count(it->first))
             it++;
         else
-            it = here->erase(it);
+            it = here.singletons->erase(it);
     }
 }
 
@@ -1646,12 +1963,35 @@ bool Normalizer::intersectNormalWithTy(NormalizedType& here, TypeId there)
             here.booleans = intersectionOfBools(booleans, there);
         else if (const StringSingleton* sstv = get<StringSingleton>(stv))
         {
-            if (!strings || strings->count(sstv->value))
-                here.strings->insert({sstv->value, there});
+            if (strings.includes(sstv->value))
+                here.strings.singletons->insert({sstv->value, there});
         }
         else
             LUAU_ASSERT(!"Unreachable");
     }
+    else if (const NegationTypeVar* ntv = get<NegationTypeVar>(there); FFlag::LuauNegatedStringSingletons && ntv)
+    {
+        TypeId t = follow(ntv->ty);
+        if (const PrimitiveTypeVar* ptv = get<PrimitiveTypeVar>(t))
+            subtractPrimitive(here, ntv->ty);
+        else if (const SingletonTypeVar* stv = get<SingletonTypeVar>(t))
+            subtractSingleton(here, follow(ntv->ty));
+        else if (const UnionTypeVar* itv = get<UnionTypeVar>(t))
+        {
+            for (TypeId part : itv->options)
+            {
+                const NormalizedType* normalPart = normalize(part);
+                NormalizedType negated = negateNormal(*normalPart);
+                intersectNormals(here, negated);
+            }
+        }
+        else
+        {
+            // TODO negated unions, intersections, table, and function.
+            // Report a TypeError for other types.
+            LUAU_ASSERT(!"Unimplemented");
+        }
+    }
     else
         LUAU_ASSERT(!"Unreachable");
 
@@ -1691,11 +2031,25 @@ TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
         result.push_back(norm.nils);
     if (!get<NeverTypeVar>(norm.numbers))
         result.push_back(norm.numbers);
-    if (norm.strings)
-        for (auto& [_, ty] : *norm.strings)
-            result.push_back(ty);
-    else
+    if (norm.strings.isString())
         result.push_back(singletonTypes->stringType);
+    else if (norm.strings.isUnion())
+    {
+        for (auto& [_, ty] : *norm.strings.singletons)
+            result.push_back(ty);
+    }
+    else if (FFlag::LuauNegatedStringSingletons && norm.strings.isIntersection())
+    {
+        std::vector<TypeId> parts;
+        parts.push_back(singletonTypes->stringType);
+        for (const auto& [name, ty] : *norm.strings.singletons)
+            parts.push_back(arena->addType(NegationTypeVar{ty}));
+
+        result.push_back(arena->addType(IntersectionTypeVar{std::move(parts)}));
+    }
+    if (!get<NeverTypeVar>(norm.threads))
+        result.push_back(singletonTypes->threadType);
+
     result.insert(result.end(), norm.tables.begin(), norm.tables.end());
     for (auto& [tyvar, intersect] : norm.tyvars)
     {

Analysis/src/ToString.cpp

@@ -11,6 +11,7 @@
 #include <stdexcept>
 
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
+LUAU_FASTFLAG(LuauLvaluelessPath)
 LUAU_FASTFLAGVARIABLE(LuauSpecialTypesAsterisked, false)
 LUAU_FASTFLAGVARIABLE(LuauFixNameMaps, false)
 LUAU_FASTFLAGVARIABLE(LuauUnseeArrayTtv, false)
@@ -435,7 +436,7 @@ struct TypeVarStringifier
             return;
         default:
             LUAU_ASSERT(!"Unknown primitive type");
-            throw std::runtime_error("Unknown primitive type " + std::to_string(ptv.type));
+            throwRuntimeError("Unknown primitive type " + std::to_string(ptv.type));
         }
     }
 
@@ -452,7 +453,7 @@ struct TypeVarStringifier
         else
         {
             LUAU_ASSERT(!"Unknown singleton type");
-            throw std::runtime_error("Unknown singleton type");
+            throwRuntimeError("Unknown singleton type");
         }
     }
 
@@ -1548,6 +1549,8 @@ std::string dump(const Constraint& c)
 
 std::string toString(const LValue& lvalue)
 {
+    LUAU_ASSERT(!FFlag::LuauLvaluelessPath);
+
     std::string s;
     for (const LValue* current = &lvalue; current; current = baseof(*current))
     {
@@ -1562,4 +1565,37 @@ std::string toString(const LValue& lvalue)
     return s;
 }
 
+std::optional<std::string> getFunctionNameAsString(const AstExpr& expr)
+{
+    LUAU_ASSERT(FFlag::LuauLvaluelessPath);
+
+    const AstExpr* curr = &expr;
+    std::string s;
+
+    for (;;)
+    {
+        if (auto local = curr->as<AstExprLocal>())
+            return local->local->name.value + s;
+
+        if (auto global = curr->as<AstExprGlobal>())
+            return global->name.value + s;
+
+        if (auto indexname = curr->as<AstExprIndexName>())
+        {
+            curr = indexname->expr;
+
+            s = "." + std::string(indexname->index.value) + s;
+        }
+        else if (auto group = curr->as<AstExprGroup>())
+        {
+            curr = group->expr;
+        }
+        else
+        {
+            return std::nullopt;
+        }
+    }
+
+    return s;
+}
 } // namespace Luau

Analysis/src/TopoSortStatements.cpp

@@ -1,6 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/TopoSortStatements.h"
 
+#include "Luau/Error.h"
 /* Decide the order in which we typecheck Lua statements in a block.
  *
  * Algorithm:
@@ -149,7 +150,7 @@ Identifier mkName(const AstStatFunction& function)
     auto name = mkName(*function.name);
     LUAU_ASSERT(bool(name));
     if (!name)
-        throw std::runtime_error("Internal error: Function declaration has a bad name");
+        throwRuntimeError("Internal error: Function declaration has a bad name");
 
     return *name;
 }
@@ -255,7 +256,7 @@ struct ArcCollector : public AstVisitor
     {
         auto name = mkName(*node->name);
         if (!name)
-            throw std::runtime_error("Internal error: AstStatFunction has a bad name");
+            throwRuntimeError("Internal error: AstStatFunction has a bad name");
 
         add(*name);
         return true;

Analysis/src/TypeAttach.cpp

@@ -347,7 +347,7 @@ public:
     AstType* operator()(const NegationTypeVar& ntv)
     {
         // FIXME: do the same thing we do with ErrorTypeVar
-        throw std::runtime_error("Cannot convert NegationTypeVar into AstNode");
+        throwRuntimeError("Cannot convert NegationTypeVar into AstNode");
     }
 
 private:

Analysis/src/TypeChecker2.cpp

@@ -934,8 +934,62 @@ struct TypeChecker2
 
     void visit(AstExprUnary* expr)
     {
-        // TODO!
         visit(expr->expr);
+
+        NotNull<Scope> scope = stack.back();
+        TypeId operandType = lookupType(expr->expr);
+
+        if (get<AnyTypeVar>(operandType) || get<ErrorTypeVar>(operandType) || get<NeverTypeVar>(operandType))
+            return;
+
+        if (auto it = kUnaryOpMetamethods.find(expr->op); it != kUnaryOpMetamethods.end())
+        {
+            std::optional<TypeId> mm = findMetatableEntry(singletonTypes, module->errors, operandType, it->second, expr->location);
+            if (mm)
+            {
+                if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(follow(*mm)))
+                {
+                    TypePackId expectedArgs = module->internalTypes.addTypePack({operandType});
+                    reportErrors(tryUnify(scope, expr->location, ftv->argTypes, expectedArgs));
+
+                    if (std::optional<TypeId> ret = first(ftv->retTypes))
+                    {
+                        if (expr->op == AstExprUnary::Op::Len)
+                        {
+                            reportErrors(tryUnify(scope, expr->location, follow(*ret), singletonTypes->numberType));
+                        }
+                    }
+                    else
+                    {
+                        reportError(GenericError{format("Metamethod '%s' must return a value", it->second)}, expr->location);
+                    }
+                }
+
+                return;
+            }
+        }
+
+        if (expr->op == AstExprUnary::Op::Len)
+        {
+            DenseHashSet<TypeId> seen{nullptr};
+            int recursionCount = 0;
+
+            if (!hasLength(operandType, seen, &recursionCount))
+            {
+                reportError(NotATable{operandType}, expr->location);
+            }
+        }
+        else if (expr->op == AstExprUnary::Op::Minus)
+        {
+            reportErrors(tryUnify(scope, expr->location, operandType, singletonTypes->numberType));
+        }
+        else if (expr->op == AstExprUnary::Op::Not)
+        {
+        }
+        else
+        {
+            LUAU_ASSERT(!"Unhandled unary operator");
+        }
     }
 
     void visit(AstExprBinary* expr)
@@ -1240,9 +1294,8 @@ struct TypeChecker2
         Scope* scope = findInnermostScope(ty->location);
         LUAU_ASSERT(scope);
 
-        // TODO: Imported types
-
-        std::optional<TypeFun> alias = scope->lookupType(ty->name.value);
+        std::optional<TypeFun> alias =
+            (ty->prefix) ? scope->lookupImportedType(ty->prefix->value, ty->name.value) : scope->lookupType(ty->name.value);
 
         if (alias.has_value())
         {

Analysis/src/TypeInfer.cpp

@@ -36,6 +36,7 @@ LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification, false)
 LUAU_FASTFLAGVARIABLE(LuauReturnAnyInsteadOfICE, false) // Eventually removed as false.
 LUAU_FASTFLAGVARIABLE(DebugLuauSharedSelf, false)
 LUAU_FASTFLAGVARIABLE(LuauAnyifyModuleReturnGenerics, false)
+LUAU_FASTFLAGVARIABLE(LuauLvaluelessPath, false)
 LUAU_FASTFLAGVARIABLE(LuauUnknownAndNeverType, false)
 LUAU_FASTFLAGVARIABLE(LuauBinaryNeedsExpectedTypesToo, false)
 LUAU_FASTFLAGVARIABLE(LuauFixVarargExprHeadType, false)
@@ -43,15 +44,15 @@ LUAU_FASTFLAGVARIABLE(LuauNeverTypesAndOperatorsInference, false)
 LUAU_FASTFLAGVARIABLE(LuauReturnsFromCallsitesAreNotWidened, false)
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
 LUAU_FASTFLAGVARIABLE(LuauCompleteVisitor, false)
-LUAU_FASTFLAGVARIABLE(LuauUnionOfTypesFollow, false)
 LUAU_FASTFLAGVARIABLE(LuauReportShadowedTypeAlias, false)
 LUAU_FASTFLAGVARIABLE(LuauBetterMessagingOnCountMismatch, false)
+LUAU_FASTFLAGVARIABLE(LuauArgMismatchReportFunctionLocation, false)
 
 namespace Luau
 {
-
-const char* TimeLimitError::what() const throw()
+const char* TimeLimitError_DEPRECATED::what() const throw()
 {
+    LUAU_ASSERT(!FFlag::LuauIceExceptionInheritanceChange);
     return "Typeinfer failed to complete in allotted time";
 }
 
@@ -264,6 +265,11 @@ ModulePtr TypeChecker::check(const SourceModule& module, Mode mode, std::optiona
         reportErrorCodeTooComplex(module.root->location);
         return std::move(currentModule);
     }
+    catch (const RecursionLimitException_DEPRECATED&)
+    {
+        reportErrorCodeTooComplex(module.root->location);
+        return std::move(currentModule);
+    }
 }
 
 ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mode mode, std::optional<ScopePtr> environmentScope)
@@ -308,6 +314,10 @@ ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mo
     {
         currentModule->timeout = true;
     }
+    catch (const TimeLimitError_DEPRECATED&)
+    {
+        currentModule->timeout = true;
+    }
 
     if (FFlag::DebugLuauSharedSelf)
     {
@@ -415,7 +425,7 @@ void TypeChecker::check(const ScopePtr& scope, const AstStat& program)
         ice("Unknown AstStat");
 
     if (finishTime && TimeTrace::getClock() > *finishTime)
-        throw TimeLimitError();
+        throwTimeLimitError();
 }
 
 // This particular overload is for do...end. If you need to not increase the scope level, use checkBlock directly.
@@ -442,6 +452,11 @@ void TypeChecker::checkBlock(const ScopePtr& scope, const AstStatBlock& block)
         reportErrorCodeTooComplex(block.location);
         return;
     }
+    catch (const RecursionLimitException_DEPRECATED&)
+    {
+        reportErrorCodeTooComplex(block.location);
+        return;
+    }
 }
 
 struct InplaceDemoter : TypeVarOnceVisitor
@@ -2456,11 +2471,8 @@ std::string opToMetaTableEntry(const AstExprBinary::Op& op)
 
 TypeId TypeChecker::unionOfTypes(TypeId a, TypeId b, const ScopePtr& scope, const Location& location, bool unifyFreeTypes)
 {
-    if (FFlag::LuauUnionOfTypesFollow)
-    {
-        a = follow(a);
-        b = follow(b);
-    }
+    a = follow(a);
+    b = follow(b);
 
     if (unifyFreeTypes && (get<FreeTypeVar>(a) || get<FreeTypeVar>(b)))
     {
@@ -3596,8 +3608,17 @@ void TypeChecker::checkArgumentList(const ScopePtr& scope, const AstExpr& funNam
             location = {state.location.begin, argLocations.back().end};
 
         std::string namePath;
-        if (std::optional<LValue> lValue = tryGetLValue(funName))
-            namePath = toString(*lValue);
+
+        if (FFlag::LuauLvaluelessPath)
+        {
+            if (std::optional<std::string> path = getFunctionNameAsString(funName))
+                namePath = *path;
+        }
+        else
+        {
+            if (std::optional<LValue> lValue = tryGetLValue(funName))
+                namePath = toString(*lValue);
+        }
 
         auto [minParams, optMaxParams] = getParameterExtents(&state.log, paramPack);
         state.reportError(TypeError{location,
@@ -3706,11 +3727,28 @@ void TypeChecker::checkArgumentList(const ScopePtr& scope, const AstExpr& funNam
                     bool isVariadic = tail && Luau::isVariadic(*tail);
 
                     std::string namePath;
-                    if (std::optional<LValue> lValue = tryGetLValue(funName))
-                        namePath = toString(*lValue);
 
-                    state.reportError(TypeError{
-                        state.location, CountMismatch{minParams, optMaxParams, paramIndex, CountMismatch::Context::Arg, isVariadic, namePath}});
+                    if (FFlag::LuauLvaluelessPath)
+                    {
+                        if (std::optional<std::string> path = getFunctionNameAsString(funName))
+                            namePath = *path;
+                    }
+                    else
+                    {
+                        if (std::optional<LValue> lValue = tryGetLValue(funName))
+                            namePath = toString(*lValue);
+                    }
+
+                    if (FFlag::LuauArgMismatchReportFunctionLocation)
+                    {
+                        state.reportError(TypeError{
+                            funName.location, CountMismatch{minParams, optMaxParams, paramIndex, CountMismatch::Context::Arg, isVariadic, namePath}});
+                    }
+                    else
+                    {
+                        state.reportError(TypeError{
+                            state.location, CountMismatch{minParams, optMaxParams, paramIndex, CountMismatch::Context::Arg, isVariadic, namePath}});
+                    }
                     return;
                 }
                 ++paramIter;
@@ -4647,6 +4685,19 @@ void TypeChecker::ice(const std::string& message)
     iceHandler->ice(message);
 }
 
+// TODO: Inline me when LuauIceExceptionInheritanceChange is deleted.
+void TypeChecker::throwTimeLimitError()
+{
+    if (FFlag::LuauIceExceptionInheritanceChange)
+    {
+        throw TimeLimitError(iceHandler->moduleName);
+    }
+    else
+    {
+        throw TimeLimitError_DEPRECATED();
+    }
+}
+
 void TypeChecker::prepareErrorsForDisplay(ErrorVec& errVec)
 {
     // Remove errors with names that were generated by recovery from a parse error

Analysis/src/TypePack.cpp

@@ -1,6 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/TypePack.h"
 
+#include "Luau/Error.h"
 #include "Luau/TxnLog.h"
 
 #include <stdexcept>
@@ -234,7 +235,7 @@ TypePackId follow(TypePackId tp, std::function<TypePackId(TypePackId)> mapper)
                 cycleTester = nullptr;
 
             if (tp == cycleTester)
-                throw std::runtime_error("Luau::follow detected a TypeVar cycle!!");
+                throwRuntimeError("Luau::follow detected a TypeVar cycle!!");
         }
     }
 }

Analysis/src/TypeVar.cpp

@@ -61,7 +61,7 @@ TypeId follow(TypeId t, std::function<TypeId(TypeId)> mapper)
         {
             std::optional<TypeId> ty = utv->scope->lookup(utv->def);
             if (!ty)
-                throw std::runtime_error("UseTypeVar must map to another TypeId");
+                throwRuntimeError("UseTypeVar must map to another TypeId");
             return *ty;
         }
         else
@@ -73,7 +73,7 @@ TypeId follow(TypeId t, std::function<TypeId(TypeId)> mapper)
         {
             TypeId res = ltv->thunk();
             if (get<LazyTypeVar>(res))
-                throw std::runtime_error("Lazy TypeVar cannot resolve to another Lazy TypeVar");
+                throwRuntimeError("Lazy TypeVar cannot resolve to another Lazy TypeVar");
 
             *asMutable(ty) = BoundTypeVar(res);
         }
@@ -111,7 +111,7 @@ TypeId follow(TypeId t, std::function<TypeId(TypeId)> mapper)
                 cycleTester = nullptr;
 
             if (t == cycleTester)
-                throw std::runtime_error("Luau::follow detected a TypeVar cycle!!");
+                throwRuntimeError("Luau::follow detected a TypeVar cycle!!");
         }
     }
 }
@@ -946,7 +946,7 @@ void persist(TypeId ty)
             queue.push_back(mtv->table);
             queue.push_back(mtv->metatable);
         }
-        else if (get<GenericTypeVar>(t) || get<AnyTypeVar>(t) || get<FreeTypeVar>(t) || get<SingletonTypeVar>(t) || get<PrimitiveTypeVar>(t))
+        else if (get<GenericTypeVar>(t) || get<AnyTypeVar>(t) || get<FreeTypeVar>(t) || get<SingletonTypeVar>(t) || get<PrimitiveTypeVar>(t) || get<NegationTypeVar>(t))
         {
         }
         else

Analysis/src/Unifier.cpp

@@ -16,6 +16,7 @@
 LUAU_FASTINT(LuauTypeInferTypePackLoopLimit);
 LUAU_FASTFLAG(LuauErrorRecoveryType);
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
+LUAU_FASTFLAGVARIABLE(LuauReportTypeMismatchForTypePackUnificationFailure, false)
 LUAU_FASTFLAGVARIABLE(LuauSubtypeNormalizer, false);
 LUAU_FASTFLAGVARIABLE(LuauScalarShapeSubtyping, false)
 LUAU_FASTFLAGVARIABLE(LuauInstantiateInSubtyping, false)
@@ -273,7 +274,7 @@ TypeId Widen::clean(TypeId ty)
 
 TypePackId Widen::clean(TypePackId)
 {
-    throw std::runtime_error("Widen attempted to clean a dirty type pack?");
+    throwRuntimeError("Widen attempted to clean a dirty type pack?");
 }
 
 bool Widen::ignoreChildren(TypeId ty)
@@ -551,6 +552,12 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     else if (log.getMutable<ClassTypeVar>(subTy))
         tryUnifyWithClass(subTy, superTy, /*reversed*/ true);
 
+    else if (log.get<NegationTypeVar>(superTy))
+        tryUnifyTypeWithNegation(subTy, superTy);
+
+    else if (log.get<NegationTypeVar>(subTy))
+        tryUnifyNegationWithType(subTy, superTy);
+
     else
         reportError(TypeError{location, TypeMismatch{superTy, subTy}});
 
@@ -866,13 +873,7 @@ void Unifier::tryUnifyNormalizedTypes(
         if (!get<PrimitiveTypeVar>(superNorm.numbers))
             return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
 
-    if (subNorm.strings && superNorm.strings)
-    {
-        for (auto [name, ty] : *subNorm.strings)
-            if (!superNorm.strings->count(name))
-                return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
-    }
-    else if (!subNorm.strings && superNorm.strings)
+    if (!isSubtype(subNorm.strings, superNorm.strings))
         return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
 
     if (get<PrimitiveTypeVar>(subNorm.threads))
@@ -1392,7 +1393,10 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
     }
     else
     {
-        reportError(TypeError{location, GenericError{"Failed to unify type packs"}});
+        if (FFlag::LuauReportTypeMismatchForTypePackUnificationFailure)
+            reportError(TypeError{location, TypePackMismatch{subTp, superTp}});
+        else
+            reportError(TypeError{location, GenericError{"Failed to unify type packs"}});
     }
 }
 
@@ -1441,7 +1445,10 @@ void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCal
 
     bool shouldInstantiate = (numGenerics == 0 && subFunction->generics.size() > 0) || (numGenericPacks == 0 && subFunction->genericPacks.size() > 0);
 
-    if (FFlag::LuauInstantiateInSubtyping && variance == Covariant && shouldInstantiate)
+    // TODO: This is unsound when the context is invariant, but the annotation burden without allowing it and without
+    // read-only properties is too high for lua-apps. Read-only properties _should_ resolve their issue by allowing
+    // generic methods in tables to be marked read-only.
+    if (FFlag::LuauInstantiateInSubtyping && shouldInstantiate)
     {
         Instantiation instantiation{&log, types, scope->level, scope};
 
@@ -1576,6 +1583,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
 {
     TableTypeVar* superTable = log.getMutable<TableTypeVar>(superTy);
     TableTypeVar* subTable = log.getMutable<TableTypeVar>(subTy);
+    TableTypeVar* instantiatedSubTable = subTable;
 
     if (!superTable || !subTable)
         ice("passed non-table types to unifyTables");
@@ -1593,6 +1601,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
             if (instantiated.has_value())
             {
                 subTable = log.getMutable<TableTypeVar>(*instantiated);
+                instantiatedSubTable = subTable;
 
                 if (!subTable)
                     ice("instantiation made a table type into a non-table type in tryUnifyTables");
@@ -1696,7 +1705,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         // txn log.
         TableTypeVar* newSuperTable = log.getMutable<TableTypeVar>(superTy);
         TableTypeVar* newSubTable = log.getMutable<TableTypeVar>(subTy);
-        if (superTable != newSuperTable || subTable != newSubTable)
+        if (superTable != newSuperTable || (subTable != newSubTable && subTable != instantiatedSubTable))
         {
             if (errors.empty())
                 return tryUnifyTables(subTy, superTy, isIntersection);
@@ -1758,7 +1767,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         // txn log.
         TableTypeVar* newSuperTable = log.getMutable<TableTypeVar>(superTy);
         TableTypeVar* newSubTable = log.getMutable<TableTypeVar>(subTy);
-        if (superTable != newSuperTable || subTable != newSubTable)
+        if (superTable != newSuperTable || (subTable != newSubTable && subTable != instantiatedSubTable))
         {
             if (errors.empty())
                 return tryUnifyTables(subTy, superTy, isIntersection);
@@ -2098,6 +2107,34 @@ void Unifier::tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed)
         return fail();
 }
 
+void Unifier::tryUnifyTypeWithNegation(TypeId subTy, TypeId superTy)
+{
+    const NegationTypeVar* ntv = get<NegationTypeVar>(superTy);
+    if (!ntv)
+        ice("tryUnifyTypeWithNegation superTy must be a negation type");
+
+    const NormalizedType* subNorm = normalizer->normalize(subTy);
+    const NormalizedType* superNorm = normalizer->normalize(superTy);
+    if (!subNorm || !superNorm)
+        return reportError(TypeError{location, UnificationTooComplex{}});
+
+    // T </: ~U iff T <: U
+    Unifier state = makeChildUnifier();
+    state.tryUnifyNormalizedTypes(subTy, superTy, *subNorm, *superNorm, "");
+    if (state.errors.empty())
+        reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+}
+
+void Unifier::tryUnifyNegationWithType(TypeId subTy, TypeId superTy)
+{
+    const NegationTypeVar* ntv = get<NegationTypeVar>(subTy);
+    if (!ntv)
+        ice("tryUnifyNegationWithType subTy must be a negation type");
+
+    // TODO: ~T </: U iff T <: U
+    reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+}
+
 static void queueTypePack(std::vector<TypeId>& queue, DenseHashSet<TypePackId>& seenTypePacks, Unifier& state, TypePackId a, TypePackId anyTypePack)
 {
     while (true)

Ast/include/Luau/ParseResult.h

@@ -58,6 +58,8 @@ struct Comment
 struct ParseResult
 {
     AstStatBlock* root;
+    size_t lines = 0;
+
     std::vector<HotComment> hotcomments;
     std::vector<ParseError> errors;
 

Ast/include/Luau/Parser.h

@@ -302,8 +302,8 @@ private:
     AstStatError* reportStatError(const Location& location, const AstArray<AstExpr*>& expressions, const AstArray<AstStat*>& statements,
         const char* format, ...) LUAU_PRINTF_ATTR(5, 6);
     AstExprError* reportExprError(const Location& location, const AstArray<AstExpr*>& expressions, const char* format, ...) LUAU_PRINTF_ATTR(4, 5);
-    AstTypeError* reportTypeAnnotationError(const Location& location, const AstArray<AstType*>& types, bool isMissing, const char* format, ...)
-        LUAU_PRINTF_ATTR(5, 6);
+    AstTypeError* reportTypeAnnotationError(const Location& location, const AstArray<AstType*>& types, const char* format, ...)
+        LUAU_PRINTF_ATTR(4, 5);
     // `parseErrorLocation` is associated with the parser error
     // `astErrorLocation` is associated with the AstTypeError created
     // It can be useful to have different error locations so that the parse error can include the next lexeme, while the AstTypeError can precisely

Ast/src/Parser.cpp

@@ -23,7 +23,6 @@ LUAU_FASTFLAGVARIABLE(LuauErrorDoubleHexPrefix, false)
 LUAU_DYNAMIC_FASTFLAGVARIABLE(LuaReportParseIntegerIssues, false)
 
 LUAU_FASTFLAGVARIABLE(LuauInterpolatedStringBaseSupport, false)
-LUAU_FASTFLAGVARIABLE(LuauTypeAnnotationLocationChange, false)
 
 LUAU_FASTFLAGVARIABLE(LuauCommaParenWarnings, false)
 
@@ -164,15 +163,16 @@ ParseResult Parser::parse(const char* buffer, size_t bufferSize, AstNameTable& n
     try
     {
         AstStatBlock* root = p.parseChunk();
+        size_t lines = p.lexer.current().location.end.line + (bufferSize > 0 && buffer[bufferSize - 1] != '\n');
 
-        return ParseResult{root, std::move(p.hotcomments), std::move(p.parseErrors), std::move(p.commentLocations)};
+        return ParseResult{root, lines, std::move(p.hotcomments), std::move(p.parseErrors), std::move(p.commentLocations)};
     }
     catch (ParseError& err)
     {
         // when catching a fatal error, append it to the list of non-fatal errors and return
         p.parseErrors.push_back(err);
 
-        return ParseResult{nullptr, {}, p.parseErrors};
+        return ParseResult{nullptr, 0, {}, p.parseErrors};
     }
 }
 
@@ -811,9 +811,8 @@ AstDeclaredClassProp Parser::parseDeclaredClassMethod()
 
     if (args.size() == 0 || args[0].name.name != "self" || args[0].annotation != nullptr)
     {
-        return AstDeclaredClassProp{fnName.name,
-            reportTypeAnnotationError(Location(start, end), {}, /*isMissing*/ false, "'self' must be present as the unannotated first parameter"),
-            true};
+        return AstDeclaredClassProp{
+            fnName.name, reportTypeAnnotationError(Location(start, end), {}, "'self' must be present as the unannotated first parameter"), true};
     }
 
     // Skip the first index.
@@ -824,8 +823,7 @@ AstDeclaredClassProp Parser::parseDeclaredClassMethod()
         if (args[i].annotation)
             vars.push_back(args[i].annotation);
         else
-            vars.push_back(reportTypeAnnotationError(
-                Location(start, end), {}, /*isMissing*/ false, "All declaration parameters aside from 'self' must be annotated"));
+            vars.push_back(reportTypeAnnotationError(Location(start, end), {}, "All declaration parameters aside from 'self' must be annotated"));
     }
 
     if (vararg && !varargAnnotation)
@@ -1537,7 +1535,7 @@ AstType* Parser::parseTypeAnnotation(TempVector<AstType*>& parts, const Location
 
     if (isUnion && isIntersection)
     {
-        return reportTypeAnnotationError(Location(begin, parts.back()->location), copy(parts), /*isMissing*/ false,
+        return reportTypeAnnotationError(Location(begin, parts.back()->location), copy(parts),
             "Mixing union and intersection types is not allowed; consider wrapping in parentheses.");
     }
 
@@ -1623,18 +1621,18 @@ AstTypeOrPack Parser::parseSimpleTypeAnnotation(bool allowPack)
             return {allocator.alloc<AstTypeSingletonString>(start, svalue)};
         }
         else
-            return {reportTypeAnnotationError(start, {}, /*isMissing*/ false, "String literal contains malformed escape sequence")};
+            return {reportTypeAnnotationError(start, {}, "String literal contains malformed escape sequence")};
     }
     else if (lexer.current().type == Lexeme::InterpStringBegin || lexer.current().type == Lexeme::InterpStringSimple)
     {
         parseInterpString();
 
-        return {reportTypeAnnotationError(start, {}, /*isMissing*/ false, "Interpolated string literals cannot be used as types")};
+        return {reportTypeAnnotationError(start, {}, "Interpolated string literals cannot be used as types")};
     }
     else if (lexer.current().type == Lexeme::BrokenString)
     {
         nextLexeme();
-        return {reportTypeAnnotationError(start, {}, /*isMissing*/ false, "Malformed string")};
+        return {reportTypeAnnotationError(start, {}, "Malformed string")};
     }
     else if (lexer.current().type == Lexeme::Name)
     {
@@ -1693,33 +1691,20 @@ AstTypeOrPack Parser::parseSimpleTypeAnnotation(bool allowPack)
     {
         nextLexeme();
 
-        return {reportTypeAnnotationError(start, {}, /*isMissing*/ false,
+        return {reportTypeAnnotationError(start, {},
                     "Using 'function' as a type annotation is not supported, consider replacing with a function type annotation e.g. '(...any) -> "
                     "...any'"),
             {}};
     }
     else
     {
-        if (FFlag::LuauTypeAnnotationLocationChange)
-        {
-            // For a missing type annotation, capture 'space' between last token and the next one
-            Location astErrorlocation(lexer.previousLocation().end, start.begin);
-            // The parse error includes the next lexeme to make it easier to display where the error is (e.g. in an IDE or a CLI error message).
-            // Including the current lexeme also makes the parse error consistent with other parse errors returned by Luau.
-            Location parseErrorLocation(lexer.previousLocation().end, start.end);
-            return {
-                reportMissingTypeAnnotationError(parseErrorLocation, astErrorlocation, "Expected type, got %s", lexer.current().toString().c_str()),
-                {}};
-        }
-        else
-        {
-            Location location = lexer.current().location;
-
-            // For a missing type annotation, capture 'space' between last token and the next one
-            location = Location(lexer.previousLocation().end, lexer.current().location.begin);
-
-            return {reportTypeAnnotationError(location, {}, /*isMissing*/ true, "Expected type, got %s", lexer.current().toString().c_str()), {}};
-        }
+        // For a missing type annotation, capture 'space' between last token and the next one
+        Location astErrorlocation(lexer.previousLocation().end, start.begin);
+        // The parse error includes the next lexeme to make it easier to display where the error is (e.g. in an IDE or a CLI error message).
+        // Including the current lexeme also makes the parse error consistent with other parse errors returned by Luau.
+        Location parseErrorLocation(lexer.previousLocation().end, start.end);
+        return {
+            reportMissingTypeAnnotationError(parseErrorLocation, astErrorlocation, "Expected type, got %s", lexer.current().toString().c_str()), {}};
     }
 }
 
@@ -3033,27 +3018,18 @@ AstExprError* Parser::reportExprError(const Location& location, const AstArray<A
     return allocator.alloc<AstExprError>(location, expressions, unsigned(parseErrors.size() - 1));
 }
 
-AstTypeError* Parser::reportTypeAnnotationError(const Location& location, const AstArray<AstType*>& types, bool isMissing, const char* format, ...)
+AstTypeError* Parser::reportTypeAnnotationError(const Location& location, const AstArray<AstType*>& types, const char* format, ...)
 {
-    if (FFlag::LuauTypeAnnotationLocationChange)
-    {
-        // Missing type annotations should be using `reportMissingTypeAnnotationError` when LuauTypeAnnotationLocationChange is enabled
-        // Note: `isMissing` can be removed once FFlag::LuauTypeAnnotationLocationChange is removed since it will always be true.
-        LUAU_ASSERT(!isMissing);
-    }
-
     va_list args;
     va_start(args, format);
     report(location, format, args);
     va_end(args);
 
-    return allocator.alloc<AstTypeError>(location, types, isMissing, unsigned(parseErrors.size() - 1));
+    return allocator.alloc<AstTypeError>(location, types, false, unsigned(parseErrors.size() - 1));
 }
 
 AstTypeError* Parser::reportMissingTypeAnnotationError(const Location& parseErrorLocation, const Location& astErrorLocation, const char* format, ...)
 {
-    LUAU_ASSERT(FFlag::LuauTypeAnnotationLocationChange);
-
     va_list args;
     va_start(args, format);
     report(parseErrorLocation, format, args);

CLI/Repl.cpp

@@ -16,7 +16,6 @@
 
 #include "isocline.h"
 
-#include <algorithm>
 #include <memory>
 
 #ifdef _WIN32
@@ -688,11 +687,11 @@ static std::string getCodegenAssembly(const char* name, const std::string& bytec
     return "";
 }
 
-static void annotateInstruction(void* context, std::string& text, int fid, int instid)
+static void annotateInstruction(void* context, std::string& text, int fid, int instpos)
 {
     Luau::BytecodeBuilder& bcb = *(Luau::BytecodeBuilder*)context;
 
-    bcb.annotateInstruction(text, fid, instid);
+    bcb.annotateInstruction(text, fid, instpos);
 }
 
 struct CompileStats
@@ -711,7 +710,8 @@ static bool compileFile(const char* name, CompileFormat format, CompileStats& st
         return false;
     }
 
-    stats.lines += std::count(source->begin(), source->end(), '\n');
+    // NOTE: Normally, you should use Luau::compile or luau_compile (see lua_require as an example)
+    // This function is much more complicated because it supports many output human-readable formats through internal interfaces
 
     try
     {
@@ -736,7 +736,16 @@ static bool compileFile(const char* name, CompileFormat format, CompileStats& st
             bcb.setDumpSource(*source);
         }
 
-        Luau::compileOrThrow(bcb, *source, copts());
+        Luau::Allocator allocator;
+        Luau::AstNameTable names(allocator);
+        Luau::ParseResult result = Luau::Parser::parse(source->c_str(), source->size(), names, allocator);
+
+        if (!result.errors.empty())
+            throw Luau::ParseErrors(result.errors);
+
+        stats.lines += result.lines;
+
+        Luau::compileOrThrow(bcb, result, names, copts());
         stats.bytecode += bcb.getBytecode().size();
 
         switch (format)

CMakeLists.txt

@@ -143,6 +143,11 @@ if (MSVC AND MSVC_VERSION GREATER_EQUAL 1924)
     set_source_files_properties(VM/src/lvmexecute.cpp PROPERTIES COMPILE_FLAGS /d2ssa-pre-)
 endif()
 
+if (NOT MSVC)
+    # disable support for math_errno which allows compilers to lower sqrt() into a single CPU instruction
+    target_compile_options(Luau.VM PRIVATE -fno-math-errno)
+endif()
+
 if(MSVC AND LUAU_BUILD_CLI)
     # the default stack size that MSVC linker uses is 1 MB; we need more stack space in Debug because stack frames are larger
     set_target_properties(Luau.Analyze.CLI PROPERTIES LINK_FLAGS_DEBUG /STACK:2097152)

CodeGen/include/Luau/CodeGen.h

@@ -17,7 +17,7 @@ void create(lua_State* L);
 // Builds target function and all inner functions
 void compile(lua_State* L, int idx);
 
-using annotatorFn = void (*)(void* context, std::string& result, int fid, int instid);
+using annotatorFn = void (*)(void* context, std::string& result, int fid, int instpos);
 
 struct AssemblyOptions
 {

CodeGen/src/CodeGen.cpp

@@ -34,7 +34,350 @@ namespace CodeGen
 
 constexpr uint32_t kFunctionAlignment = 32;
 
-static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& data, Proto* proto, AssemblyOptions options)
+struct InstructionOutline
+{
+    int pcpos;
+    int length;
+};
+
+static void assembleHelpers(AssemblyBuilderX64& build, ModuleHelpers& helpers)
+{
+    if (build.logText)
+        build.logAppend("; exitContinueVm\n");
+    helpers.exitContinueVm = build.setLabel();
+    emitExit(build, /* continueInVm */ true);
+
+    if (build.logText)
+        build.logAppend("; exitNoContinueVm\n");
+    helpers.exitNoContinueVm = build.setLabel();
+    emitExit(build, /* continueInVm */ false);
+}
+
+static int emitInst(
+    AssemblyBuilderX64& build, NativeState& data, ModuleHelpers& helpers, Proto* proto, LuauOpcode op, const Instruction* pc, int i, Label* labelarr, Label& fallback)
+{
+    int skip = 0;
+
+    switch (op)
+    {
+    case LOP_NOP:
+        break;
+    case LOP_LOADNIL:
+        emitInstLoadNil(build, pc);
+        break;
+    case LOP_LOADB:
+        emitInstLoadB(build, pc, i, labelarr);
+        break;
+    case LOP_LOADN:
+        emitInstLoadN(build, pc);
+        break;
+    case LOP_LOADK:
+        emitInstLoadK(build, pc);
+        break;
+    case LOP_LOADKX:
+        emitInstLoadKX(build, pc);
+        break;
+    case LOP_MOVE:
+        emitInstMove(build, pc);
+        break;
+    case LOP_GETGLOBAL:
+        emitInstGetGlobal(build, pc, i, fallback);
+        break;
+    case LOP_SETGLOBAL:
+        emitInstSetGlobal(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_RETURN:
+        emitInstReturn(build, helpers, pc, i, labelarr);
+        break;
+    case LOP_GETTABLE:
+        emitInstGetTable(build, pc, i, fallback);
+        break;
+    case LOP_SETTABLE:
+        emitInstSetTable(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_GETTABLEKS:
+        emitInstGetTableKS(build, pc, i, fallback);
+        break;
+    case LOP_SETTABLEKS:
+        emitInstSetTableKS(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_GETTABLEN:
+        emitInstGetTableN(build, pc, i, fallback);
+        break;
+    case LOP_SETTABLEN:
+        emitInstSetTableN(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_JUMP:
+        emitInstJump(build, pc, i, labelarr);
+        break;
+    case LOP_JUMPBACK:
+        emitInstJumpBack(build, pc, i, labelarr);
+        break;
+    case LOP_JUMPIF:
+        emitInstJumpIf(build, pc, i, labelarr, /* not_ */ false);
+        break;
+    case LOP_JUMPIFNOT:
+        emitInstJumpIf(build, pc, i, labelarr, /* not_ */ true);
+        break;
+    case LOP_JUMPIFEQ:
+        emitInstJumpIfEq(build, pc, i, labelarr, /* not_ */ false, fallback);
+        break;
+    case LOP_JUMPIFLE:
+        emitInstJumpIfCond(build, pc, i, labelarr, Condition::LessEqual, fallback);
+        break;
+    case LOP_JUMPIFLT:
+        emitInstJumpIfCond(build, pc, i, labelarr, Condition::Less, fallback);
+        break;
+    case LOP_JUMPIFNOTEQ:
+        emitInstJumpIfEq(build, pc, i, labelarr, /* not_ */ true, fallback);
+        break;
+    case LOP_JUMPIFNOTLE:
+        emitInstJumpIfCond(build, pc, i, labelarr, Condition::NotLessEqual, fallback);
+        break;
+    case LOP_JUMPIFNOTLT:
+        emitInstJumpIfCond(build, pc, i, labelarr, Condition::NotLess, fallback);
+        break;
+    case LOP_JUMPX:
+        emitInstJumpX(build, pc, i, labelarr);
+        break;
+    case LOP_JUMPXEQKNIL:
+        emitInstJumpxEqNil(build, pc, i, labelarr);
+        break;
+    case LOP_JUMPXEQKB:
+        emitInstJumpxEqB(build, pc, i, labelarr);
+        break;
+    case LOP_JUMPXEQKN:
+        emitInstJumpxEqN(build, pc, proto->k, i, labelarr);
+        break;
+    case LOP_JUMPXEQKS:
+        emitInstJumpxEqS(build, pc, i, labelarr);
+        break;
+    case LOP_ADD:
+        emitInstBinary(build, pc, i, TM_ADD, fallback);
+        break;
+    case LOP_SUB:
+        emitInstBinary(build, pc, i, TM_SUB, fallback);
+        break;
+    case LOP_MUL:
+        emitInstBinary(build, pc, i, TM_MUL, fallback);
+        break;
+    case LOP_DIV:
+        emitInstBinary(build, pc, i, TM_DIV, fallback);
+        break;
+    case LOP_MOD:
+        emitInstBinary(build, pc, i, TM_MOD, fallback);
+        break;
+    case LOP_POW:
+        emitInstBinary(build, pc, i, TM_POW, fallback);
+        break;
+    case LOP_ADDK:
+        emitInstBinaryK(build, pc, i, TM_ADD, fallback);
+        break;
+    case LOP_SUBK:
+        emitInstBinaryK(build, pc, i, TM_SUB, fallback);
+        break;
+    case LOP_MULK:
+        emitInstBinaryK(build, pc, i, TM_MUL, fallback);
+        break;
+    case LOP_DIVK:
+        emitInstBinaryK(build, pc, i, TM_DIV, fallback);
+        break;
+    case LOP_MODK:
+        emitInstBinaryK(build, pc, i, TM_MOD, fallback);
+        break;
+    case LOP_POWK:
+        emitInstPowK(build, pc, proto->k, i, fallback);
+        break;
+    case LOP_NOT:
+        emitInstNot(build, pc);
+        break;
+    case LOP_MINUS:
+        emitInstMinus(build, pc, i, fallback);
+        break;
+    case LOP_LENGTH:
+        emitInstLength(build, pc, i, fallback);
+        break;
+    case LOP_NEWTABLE:
+        emitInstNewTable(build, pc, i, labelarr);
+        break;
+    case LOP_DUPTABLE:
+        emitInstDupTable(build, pc, i, labelarr);
+        break;
+    case LOP_SETLIST:
+        emitInstSetList(build, pc, i, labelarr);
+        break;
+    case LOP_GETUPVAL:
+        emitInstGetUpval(build, pc, i);
+        break;
+    case LOP_SETUPVAL:
+        emitInstSetUpval(build, pc, i, labelarr);
+        break;
+    case LOP_CLOSEUPVALS:
+        emitInstCloseUpvals(build, pc, i, labelarr);
+        break;
+    case LOP_FASTCALL:
+        skip = emitInstFastCall(build, pc, i, labelarr);
+        break;
+    case LOP_FASTCALL1:
+        skip = emitInstFastCall1(build, pc, i, labelarr);
+        break;
+    case LOP_FASTCALL2:
+        skip = emitInstFastCall2(build, pc, i, labelarr);
+        break;
+    case LOP_FASTCALL2K:
+        skip = emitInstFastCall2K(build, pc, i, labelarr);
+        break;
+    case LOP_FORNPREP:
+        emitInstForNPrep(build, pc, i, labelarr);
+        break;
+    case LOP_FORNLOOP:
+        emitInstForNLoop(build, pc, i, labelarr);
+        break;
+    case LOP_FORGLOOP:
+        emitinstForGLoop(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_FORGPREP_NEXT:
+        emitInstForGPrepNext(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_FORGPREP_INEXT:
+        emitInstForGPrepInext(build, pc, i, labelarr, fallback);
+        break;
+    case LOP_AND:
+        emitInstAnd(build, pc);
+        break;
+    case LOP_ANDK:
+        emitInstAndK(build, pc);
+        break;
+    case LOP_OR:
+        emitInstOr(build, pc);
+        break;
+    case LOP_ORK:
+        emitInstOrK(build, pc);
+        break;
+    case LOP_GETIMPORT:
+        emitInstGetImport(build, pc, fallback);
+        break;
+    case LOP_CONCAT:
+        emitInstConcat(build, pc, i, labelarr);
+        break;
+    default:
+        emitFallback(build, data, op, i);
+        break;
+    }
+
+    return skip;
+}
+
+static void emitInstFallback(AssemblyBuilderX64& build, NativeState& data, LuauOpcode op, const Instruction* pc, int i, Label* labelarr)
+{
+    switch (op)
+    {
+    case LOP_GETIMPORT:
+        emitInstGetImportFallback(build, pc, i);
+        break;
+    case LOP_GETTABLE:
+        emitInstGetTableFallback(build, pc, i);
+        break;
+    case LOP_SETTABLE:
+        emitInstSetTableFallback(build, pc, i);
+        break;
+    case LOP_GETTABLEN:
+        emitInstGetTableNFallback(build, pc, i);
+        break;
+    case LOP_SETTABLEN:
+        emitInstSetTableNFallback(build, pc, i);
+        break;
+    case LOP_JUMPIFEQ:
+        emitInstJumpIfEqFallback(build, pc, i, labelarr, /* not_ */ false);
+        break;
+    case LOP_JUMPIFLE:
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::LessEqual);
+        break;
+    case LOP_JUMPIFLT:
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::Less);
+        break;
+    case LOP_JUMPIFNOTEQ:
+        emitInstJumpIfEqFallback(build, pc, i, labelarr, /* not_ */ true);
+        break;
+    case LOP_JUMPIFNOTLE:
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::NotLessEqual);
+        break;
+    case LOP_JUMPIFNOTLT:
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::NotLess);
+        break;
+    case LOP_ADD:
+        emitInstBinaryFallback(build, pc, i, TM_ADD);
+        break;
+    case LOP_SUB:
+        emitInstBinaryFallback(build, pc, i, TM_SUB);
+        break;
+    case LOP_MUL:
+        emitInstBinaryFallback(build, pc, i, TM_MUL);
+        break;
+    case LOP_DIV:
+        emitInstBinaryFallback(build, pc, i, TM_DIV);
+        break;
+    case LOP_MOD:
+        emitInstBinaryFallback(build, pc, i, TM_MOD);
+        break;
+    case LOP_POW:
+        emitInstBinaryFallback(build, pc, i, TM_POW);
+        break;
+    case LOP_ADDK:
+        emitInstBinaryKFallback(build, pc, i, TM_ADD);
+        break;
+    case LOP_SUBK:
+        emitInstBinaryKFallback(build, pc, i, TM_SUB);
+        break;
+    case LOP_MULK:
+        emitInstBinaryKFallback(build, pc, i, TM_MUL);
+        break;
+    case LOP_DIVK:
+        emitInstBinaryKFallback(build, pc, i, TM_DIV);
+        break;
+    case LOP_MODK:
+        emitInstBinaryKFallback(build, pc, i, TM_MOD);
+        break;
+    case LOP_POWK:
+        emitInstBinaryKFallback(build, pc, i, TM_POW);
+        break;
+    case LOP_MINUS:
+        emitInstMinusFallback(build, pc, i);
+        break;
+    case LOP_LENGTH:
+        emitInstLengthFallback(build, pc, i);
+        break;
+    case LOP_FORGLOOP:
+        emitinstForGLoopFallback(build, pc, i, labelarr);
+        break;
+    case LOP_FORGPREP_NEXT:
+    case LOP_FORGPREP_INEXT:
+        emitInstForGPrepXnextFallback(build, pc, i, labelarr);
+        break;
+    case LOP_GETGLOBAL:
+        // TODO: luaV_gettable + cachedslot update instead of full fallback
+        emitFallback(build, data, op, i);
+        break;
+    case LOP_SETGLOBAL:
+        // TODO: luaV_settable + cachedslot update instead of full fallback
+        emitFallback(build, data, op, i);
+        break;
+    case LOP_GETTABLEKS:
+        // Full fallback required for LOP_GETTABLEKS because 'luaV_gettable' doesn't handle builtin vector field access
+        // It is also required to perform cached slot update
+        // TODO: extra fast-paths could be lowered before the full fallback
+        emitFallback(build, data, op, i);
+        break;
+    case LOP_SETTABLEKS:
+        // TODO: luaV_settable + cachedslot update instead of full fallback
+        emitFallback(build, data, op, i);
+        break;
+    default:
+        LUAU_ASSERT(!"Expected fallback for instruction");
+    }
+}
+
+static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& data, ModuleHelpers& helpers, Proto* proto, AssemblyOptions options)
 {
     NativeProto* result = new NativeProto();
 
@@ -59,222 +402,65 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
     std::vector<Label> instFallbacks;
     instFallbacks.resize(proto->sizecode);
 
+    std::vector<InstructionOutline> instOutlines;
+    instOutlines.reserve(64);
+
     build.align(kFunctionAlignment, AlignmentDataX64::Ud2);
 
     Label start = build.setLabel();
 
-    for (int i = 0, instid = 0; i < proto->sizecode; ++instid)
+    for (int i = 0; i < proto->sizecode;)
     {
         const Instruction* pc = &proto->code[i];
         LuauOpcode op = LuauOpcode(LUAU_INSN_OP(*pc));
 
+        int nexti = i + getOpLength(op);
+        LUAU_ASSERT(nexti <= proto->sizecode);
+
         build.setLabel(instLabels[i]);
 
         if (options.annotator)
-            options.annotator(options.annotatorContext, build.text, proto->bytecodeid, instid);
+            options.annotator(options.annotatorContext, build.text, proto->bytecodeid, i);
 
-        switch (op)
-        {
-        case LOP_NOP:
-            break;
-        case LOP_LOADNIL:
-            emitInstLoadNil(build, pc);
-            break;
-        case LOP_LOADB:
-            emitInstLoadB(build, pc, i, instLabels.data());
-            break;
-        case LOP_LOADN:
-            emitInstLoadN(build, pc);
-            break;
-        case LOP_LOADK:
-            emitInstLoadK(build, pc);
-            break;
-        case LOP_LOADKX:
-            emitInstLoadKX(build, pc);
-            break;
-        case LOP_MOVE:
-            emitInstMove(build, pc);
-            break;
-        case LOP_GETGLOBAL:
-            emitInstGetGlobal(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_SETGLOBAL:
-            emitInstSetGlobal(build, pc, i, instLabels.data(), instFallbacks[i]);
-            break;
-        case LOP_GETTABLE:
-            emitInstGetTable(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_SETTABLE:
-            emitInstSetTable(build, pc, i, instLabels.data(), instFallbacks[i]);
-            break;
-        case LOP_GETTABLEKS:
-            emitInstGetTableKS(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_SETTABLEKS:
-            emitInstSetTableKS(build, pc, i, instLabels.data(), instFallbacks[i]);
-            break;
-        case LOP_GETTABLEN:
-            emitInstGetTableN(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_SETTABLEN:
-            emitInstSetTableN(build, pc, i, instLabels.data(), instFallbacks[i]);
-            break;
-        case LOP_JUMP:
-            emitInstJump(build, pc, i, instLabels.data());
-            break;
-        case LOP_JUMPBACK:
-            emitInstJumpBack(build, pc, i, instLabels.data());
-            break;
-        case LOP_JUMPIF:
-            emitInstJumpIf(build, pc, i, instLabels.data(), /* not_ */ false);
-            break;
-        case LOP_JUMPIFNOT:
-            emitInstJumpIf(build, pc, i, instLabels.data(), /* not_ */ true);
-            break;
-        case LOP_JUMPIFEQ:
-            emitInstJumpIfEq(build, pc, i, instLabels.data(), /* not_ */ false, instFallbacks[i]);
-            break;
-        case LOP_JUMPIFLE:
-            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::LessEqual, instFallbacks[i]);
-            break;
-        case LOP_JUMPIFLT:
-            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::Less, instFallbacks[i]);
-            break;
-        case LOP_JUMPIFNOTEQ:
-            emitInstJumpIfEq(build, pc, i, instLabels.data(), /* not_ */ true, instFallbacks[i]);
-            break;
-        case LOP_JUMPIFNOTLE:
-            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::NotLessEqual, instFallbacks[i]);
-            break;
-        case LOP_JUMPIFNOTLT:
-            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::NotLess, instFallbacks[i]);
-            break;
-        case LOP_JUMPX:
-            emitInstJumpX(build, pc, i, instLabels.data());
-            break;
-        case LOP_JUMPXEQKNIL:
-            emitInstJumpxEqNil(build, pc, i, instLabels.data());
-            break;
-        case LOP_JUMPXEQKB:
-            emitInstJumpxEqB(build, pc, i, instLabels.data());
-            break;
-        case LOP_JUMPXEQKN:
-            emitInstJumpxEqN(build, pc, proto->k, i, instLabels.data());
-            break;
-        case LOP_JUMPXEQKS:
-            emitInstJumpxEqS(build, pc, i, instLabels.data());
-            break;
-        case LOP_ADD:
-            emitInstBinary(build, pc, i, TM_ADD, instFallbacks[i]);
-            break;
-        case LOP_SUB:
-            emitInstBinary(build, pc, i, TM_SUB, instFallbacks[i]);
-            break;
-        case LOP_MUL:
-            emitInstBinary(build, pc, i, TM_MUL, instFallbacks[i]);
-            break;
-        case LOP_DIV:
-            emitInstBinary(build, pc, i, TM_DIV, instFallbacks[i]);
-            break;
-        case LOP_MOD:
-            emitInstBinary(build, pc, i, TM_MOD, instFallbacks[i]);
-            break;
-        case LOP_POW:
-            emitInstBinary(build, pc, i, TM_POW, instFallbacks[i]);
-            break;
-        case LOP_ADDK:
-            emitInstBinaryK(build, pc, i, TM_ADD, instFallbacks[i]);
-            break;
-        case LOP_SUBK:
-            emitInstBinaryK(build, pc, i, TM_SUB, instFallbacks[i]);
-            break;
-        case LOP_MULK:
-            emitInstBinaryK(build, pc, i, TM_MUL, instFallbacks[i]);
-            break;
-        case LOP_DIVK:
-            emitInstBinaryK(build, pc, i, TM_DIV, instFallbacks[i]);
-            break;
-        case LOP_MODK:
-            emitInstBinaryK(build, pc, i, TM_MOD, instFallbacks[i]);
-            break;
-        case LOP_POWK:
-            emitInstPowK(build, pc, proto->k, i, instFallbacks[i]);
-            break;
-        case LOP_NOT:
-            emitInstNot(build, pc);
-            break;
-        case LOP_MINUS:
-            emitInstMinus(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_LENGTH:
-            emitInstLength(build, pc, i, instFallbacks[i]);
-            break;
-        case LOP_NEWTABLE:
-            emitInstNewTable(build, pc, i, instLabels.data());
-            break;
-        case LOP_DUPTABLE:
-            emitInstDupTable(build, pc, i, instLabels.data());
-            break;
-        case LOP_SETLIST:
-            emitInstSetList(build, pc, i, instLabels.data());
-            break;
-        case LOP_GETUPVAL:
-            emitInstGetUpval(build, pc, i);
-            break;
-        case LOP_SETUPVAL:
-            emitInstSetUpval(build, pc, i, instLabels.data());
-            break;
-        case LOP_CLOSEUPVALS:
-            emitInstCloseUpvals(build, pc, i, instLabels.data());
-            break;
-        case LOP_FASTCALL:
-            emitInstFastCall(build, pc, i, instLabels.data());
-            break;
-        case LOP_FASTCALL1:
-            emitInstFastCall1(build, pc, i, instLabels.data());
-            break;
-        case LOP_FASTCALL2:
-            emitInstFastCall2(build, pc, i, instLabels.data());
-            break;
-        case LOP_FASTCALL2K:
-            emitInstFastCall2K(build, pc, i, instLabels.data());
-            break;
-        case LOP_FORNPREP:
-            emitInstForNPrep(build, pc, i, instLabels.data());
-            break;
-        case LOP_FORNLOOP:
-            emitInstForNLoop(build, pc, i, instLabels.data());
-            break;
-        case LOP_AND:
-            emitInstAnd(build, pc);
-            break;
-        case LOP_ANDK:
-            emitInstAndK(build, pc);
-            break;
-        case LOP_OR:
-            emitInstOr(build, pc);
-            break;
-        case LOP_ORK:
-            emitInstOrK(build, pc);
-            break;
-        case LOP_GETIMPORT:
-            emitInstGetImport(build, pc, instFallbacks[i]);
-            break;
-        case LOP_CONCAT:
-            emitInstConcat(build, pc, i, instLabels.data());
-            break;
-        default:
-            emitFallback(build, data, op, i);
-            break;
-        }
+        int skip = emitInst(build, data, helpers, proto, op, pc, i, instLabels.data(), instFallbacks[i]);
 
-        i += getOpLength(op);
+        if (skip != 0)
+            instOutlines.push_back({nexti, skip});
+
+        i = nexti + skip;
         LUAU_ASSERT(i <= proto->sizecode);
     }
 
     size_t textSize = build.text.size();
     uint32_t codeSize = build.getCodeSize();
 
+    if (options.annotator && !options.skipOutlinedCode)
+        build.logAppend("; outlined instructions\n");
+
+    for (auto [pcpos, length] : instOutlines)
+    {
+        int i = pcpos;
+
+        while (i < pcpos + length)
+        {
+            const Instruction* pc = &proto->code[i];
+            LuauOpcode op = LuauOpcode(LUAU_INSN_OP(*pc));
+
+            build.setLabel(instLabels[i]);
+
+            if (options.annotator && !options.skipOutlinedCode)
+                options.annotator(options.annotatorContext, build.text, proto->bytecodeid, i);
+
+            int skip = emitInst(build, data, helpers, proto, op, pc, i, instLabels.data(), instFallbacks[i]);
+            LUAU_ASSERT(skip == 0);
+
+            i += getOpLength(op);
+        }
+
+        if (i < proto->sizecode)
+            build.jmp(instLabels[i]);
+    }
+
     if (options.annotator && !options.skipOutlinedCode)
         build.logAppend("; outlined code\n");
 
@@ -297,104 +483,7 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
 
         build.setLabel(instFallbacks[i]);
 
-        switch (op)
-        {
-        case LOP_GETIMPORT:
-            emitInstGetImportFallback(build, pc, i);
-            break;
-        case LOP_GETTABLE:
-            emitInstGetTableFallback(build, pc, i);
-            break;
-        case LOP_SETTABLE:
-            emitInstSetTableFallback(build, pc, i);
-            break;
-        case LOP_GETTABLEN:
-            emitInstGetTableNFallback(build, pc, i);
-            break;
-        case LOP_SETTABLEN:
-            emitInstSetTableNFallback(build, pc, i);
-            break;
-        case LOP_JUMPIFEQ:
-            emitInstJumpIfEqFallback(build, pc, i, instLabels.data(), /* not_ */ false);
-            break;
-        case LOP_JUMPIFLE:
-            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::LessEqual);
-            break;
-        case LOP_JUMPIFLT:
-            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::Less);
-            break;
-        case LOP_JUMPIFNOTEQ:
-            emitInstJumpIfEqFallback(build, pc, i, instLabels.data(), /* not_ */ true);
-            break;
-        case LOP_JUMPIFNOTLE:
-            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::NotLessEqual);
-            break;
-        case LOP_JUMPIFNOTLT:
-            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::NotLess);
-            break;
-        case LOP_ADD:
-            emitInstBinaryFallback(build, pc, i, TM_ADD);
-            break;
-        case LOP_SUB:
-            emitInstBinaryFallback(build, pc, i, TM_SUB);
-            break;
-        case LOP_MUL:
-            emitInstBinaryFallback(build, pc, i, TM_MUL);
-            break;
-        case LOP_DIV:
-            emitInstBinaryFallback(build, pc, i, TM_DIV);
-            break;
-        case LOP_MOD:
-            emitInstBinaryFallback(build, pc, i, TM_MOD);
-            break;
-        case LOP_POW:
-            emitInstBinaryFallback(build, pc, i, TM_POW);
-            break;
-        case LOP_ADDK:
-            emitInstBinaryKFallback(build, pc, i, TM_ADD);
-            break;
-        case LOP_SUBK:
-            emitInstBinaryKFallback(build, pc, i, TM_SUB);
-            break;
-        case LOP_MULK:
-            emitInstBinaryKFallback(build, pc, i, TM_MUL);
-            break;
-        case LOP_DIVK:
-            emitInstBinaryKFallback(build, pc, i, TM_DIV);
-            break;
-        case LOP_MODK:
-            emitInstBinaryKFallback(build, pc, i, TM_MOD);
-            break;
-        case LOP_POWK:
-            emitInstBinaryKFallback(build, pc, i, TM_POW);
-            break;
-        case LOP_MINUS:
-            emitInstMinusFallback(build, pc, i);
-            break;
-        case LOP_LENGTH:
-            emitInstLengthFallback(build, pc, i);
-            break;
-        case LOP_GETGLOBAL:
-            // TODO: luaV_gettable + cachedslot update instead of full fallback
-            emitFallback(build, data, op, i);
-            break;
-        case LOP_SETGLOBAL:
-            // TODO: luaV_settable + cachedslot update instead of full fallback
-            emitFallback(build, data, op, i);
-            break;
-        case LOP_GETTABLEKS:
-            // Full fallback required for LOP_GETTABLEKS because 'luaV_gettable' doesn't handle builtin vector field access
-            // It is also required to perform cached slot update
-            // TODO: extra fast-paths could be lowered before the full fallback
-            emitFallback(build, data, op, i);
-            break;
-        case LOP_SETTABLEKS:
-            // TODO: luaV_settable + cachedslot update instead of full fallback
-            emitFallback(build, data, op, i);
-            break;
-        default:
-            LUAU_ASSERT(!"Expected fallback for instruction");
-        }
+        emitInstFallback(build, data, op, pc, i, instLabels.data());
 
         // Jump back to the next instruction handler
         if (nexti < proto->sizecode)
@@ -568,13 +657,16 @@ void compile(lua_State* L, int idx)
     std::vector<Proto*> protos;
     gatherFunctions(protos, clvalue(func)->l.p);
 
+    ModuleHelpers helpers;
+    assembleHelpers(build, helpers);
+
     std::vector<NativeProto*> results;
     results.reserve(protos.size());
 
     // Skip protos that have been compiled during previous invocations of CodeGen::compile
     for (Proto* p : protos)
         if (p && getProtoExecData(p) == nullptr)
-            results.push_back(assembleFunction(build, *data, p, {}));
+            results.push_back(assembleFunction(build, *data, helpers, p, {}));
 
     build.finalize();
 
@@ -615,10 +707,13 @@ std::string getAssembly(lua_State* L, int idx, AssemblyOptions options)
     std::vector<Proto*> protos;
     gatherFunctions(protos, clvalue(func)->l.p);
 
+    ModuleHelpers helpers;
+    assembleHelpers(build, helpers);
+
     for (Proto* p : protos)
         if (p)
         {
-            NativeProto* nativeProto = assembleFunction(build, data, p, options);
+            NativeProto* nativeProto = assembleFunction(build, data, helpers, p, options);
             destroyNativeProto(nativeProto);
         }
 

CodeGen/src/CodeGenUtils.cpp

@@ -0,0 +1,76 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "CodeGenUtils.h"
+
+#include "ldo.h"
+#include "ltable.h"
+
+#include "FallbacksProlog.h"
+
+#include <string.h>
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+bool forgLoopNodeIter(lua_State* L, Table* h, int index, TValue* ra)
+{
+    // then we advance index through the hash portion
+    while (unsigned(index - h->sizearray) < unsigned(1 << h->lsizenode))
+    {
+        LuaNode* n = &h->node[index - h->sizearray];
+
+        if (!ttisnil(gval(n)))
+        {
+            setpvalue(ra + 2, reinterpret_cast<void*>(uintptr_t(index + 1)));
+            getnodekey(L, ra + 3, n);
+            setobj(L, ra + 4, gval(n));
+
+            return true;
+        }
+
+        index++;
+    }
+
+    return false;
+}
+
+bool forgLoopNonTableFallback(lua_State* L, int insnA, int aux)
+{
+    TValue* base = L->base;
+    TValue* ra = VM_REG(insnA);
+
+    // note: it's safe to push arguments past top for complicated reasons (see lvmexecute.cpp)
+    setobj2s(L, ra + 3 + 2, ra + 2);
+    setobj2s(L, ra + 3 + 1, ra + 1);
+    setobj2s(L, ra + 3, ra);
+
+    L->top = ra + 3 + 3; // func + 2 args (state and index)
+    LUAU_ASSERT(L->top <= L->stack_last);
+
+    luaD_call(L, ra + 3, uint8_t(aux));
+    L->top = L->ci->top;
+
+    // recompute ra since stack might have been reallocated
+    base = L->base;
+    ra = VM_REG(insnA);
+
+    // copy first variable back into the iteration index
+    setobj2s(L, ra + 2, ra + 3);
+
+    return !ttisnil(ra + 3);
+}
+
+void forgPrepXnextFallback(lua_State* L, TValue* ra, int pc)
+{
+    if (!ttisfunction(ra))
+    {
+        Closure* cl = clvalue(L->ci->func);
+        L->ci->savedpc = cl->l.p->code + pc;
+
+        luaG_typeerror(L, ra, "iterate over");
+    }
+}
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/src/CodeGenUtils.h

@@ -0,0 +1,17 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "lobject.h"
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+bool forgLoopNodeIter(lua_State* L, Table* h, int index, TValue* ra);
+bool forgLoopNonTableFallback(lua_State* L, int insnA, int aux);
+
+void forgPrepXnextFallback(lua_State* L, TValue* ra, int pc);
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/src/EmitCommonX64.h

@@ -67,6 +67,13 @@ constexpr unsigned kLuaNodeTagMask = 0xf;
 constexpr unsigned kOffsetOfLuaNodeTag = 12; // offsetof cannot be used on a bit field
 constexpr unsigned kOffsetOfInstructionC = 3;
 
+// Leaf functions that are placed in every module to perform common instruction sequences
+struct ModuleHelpers
+{
+    Label exitContinueVm;
+    Label exitNoContinueVm;
+};
+
 inline OperandX64 luauReg(int ri)
 {
     return xmmword[rBase + ri * sizeof(TValue)];
@@ -107,6 +114,12 @@ inline OperandX64 luauNodeKeyValue(RegisterX64 node)
     return qword[node + offsetof(LuaNode, key) + offsetof(TKey, value)];
 }
 
+// Note: tag has dirty upper bits
+inline OperandX64 luauNodeKeyTag(RegisterX64 node)
+{
+    return dword[node + offsetof(LuaNode, key) + kOffsetOfLuaNodeTag];
+}
+
 inline OperandX64 luauNodeValue(RegisterX64 node)
 {
     return xmmword[node + offsetof(LuaNode, val)];
@@ -184,7 +197,7 @@ inline void jumpIfNodeKeyTagIsNot(AssemblyBuilderX64& build, RegisterX64 tmp, Re
 {
     tmp.size = SizeX64::dword;
 
-    build.mov(tmp, dword[node + offsetof(LuaNode, key) + kOffsetOfLuaNodeTag]);
+    build.mov(tmp, luauNodeKeyTag(node));
     build.and_(tmp, kLuaNodeTagMask);
     build.cmp(tmp, tag);
     build.jcc(Condition::NotEqual, label);

CodeGen/src/EmitInstructionX64.cpp

@@ -34,7 +34,7 @@ void emitInstLoadB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos,
     build.mov(luauRegTag(ra), LUA_TBOOLEAN);
 
     if (int target = LUAU_INSN_C(*pc))
-        build.jmp(labelarr[pcpos + target + 1]);
+        build.jmp(labelarr[pcpos + 1 + target]);
 }
 
 void emitInstLoadN(AssemblyBuilderX64& build, const Instruction* pc)
@@ -72,23 +72,185 @@ void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc)
     build.vmovups(luauReg(ra), xmm0);
 }
 
+void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    emitInterrupt(build, pcpos);
+
+    int ra = LUAU_INSN_A(*pc);
+    int b = LUAU_INSN_B(*pc) - 1;
+
+    RegisterX64 ci = r8;
+    RegisterX64 cip = r9;
+    RegisterX64 res = rdi;
+    RegisterX64 nresults = esi;
+
+    build.mov(ci, qword[rState + offsetof(lua_State, ci)]);
+    build.lea(cip, qword[ci - sizeof(CallInfo)]);
+
+    // res = ci->func; note: we assume CALL always puts func+args and expects results to start at func
+    build.mov(res, qword[ci + offsetof(CallInfo, func)]);
+    // nresults = ci->nresults
+    build.mov(nresults, dword[ci + offsetof(CallInfo, nresults)]);
+
+    {
+        Label skipResultCopy;
+
+        RegisterX64 counter = ecx;
+
+        if (b == 0)
+        {
+            // Our instruction doesn't have any results, so just fill results expected in parent with 'nil'
+            build.test(nresults, nresults);                  // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+
+            build.mov(counter, nresults);
+
+            Label repeatNilLoop = build.setLabel();
+            build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
+            build.add(res, sizeof(TValue));
+            build.dec(counter);
+            build.jcc(Condition::NotZero, repeatNilLoop);
+        }
+        else if (b == 1)
+        {
+            // Try setting our 1 result
+            build.test(nresults, nresults);
+            build.jcc(Condition::Zero, skipResultCopy);
+
+            build.lea(counter, dword[nresults - 1]);
+
+            build.vmovups(xmm0, luauReg(ra));
+            build.vmovups(xmmword[res], xmm0);
+            build.add(res, sizeof(TValue));
+
+            // Fill the rest of the expected results with 'nil'
+            build.test(counter, counter);                    // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+
+            Label repeatNilLoop = build.setLabel();
+            build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
+            build.add(res, sizeof(TValue));
+            build.dec(counter);
+            build.jcc(Condition::NotZero, repeatNilLoop);
+        }
+        else
+        {
+            RegisterX64 vali = rax;
+            RegisterX64 valend = rdx;
+
+            // Copy return values into parent stack (but only up to nresults!)
+            build.test(nresults, nresults);
+            build.jcc(Condition::Zero, skipResultCopy);
+
+            // vali = ra
+            build.lea(vali, luauRegValue(ra));
+
+            // Copy as much as possible for MULTRET calls, and only as much as needed otherwise
+            if (b == LUA_MULTRET)
+                build.mov(valend, qword[rState + offsetof(lua_State, top)]); // valend = L->top
+            else
+                build.lea(valend, luauRegValue(ra + b)); // valend = ra + b
+
+            build.mov(counter, nresults);
+
+            Label repeatValueLoop, exitValueLoop;
+
+            build.setLabel(repeatValueLoop);
+            build.cmp(vali, valend);
+            build.jcc(Condition::NotBelow, exitValueLoop);
+
+            build.vmovups(xmm0, xmmword[vali]);
+            build.vmovups(xmmword[res], xmm0);
+            build.add(vali, sizeof(TValue));
+            build.add(res, sizeof(TValue));
+            build.dec(counter);
+            build.jcc(Condition::NotZero, repeatValueLoop);
+
+            build.setLabel(exitValueLoop);
+
+            // Fill the rest of the expected results with 'nil'
+            build.test(counter, counter);                    // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+
+            Label repeatNilLoop = build.setLabel();
+            build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
+            build.add(res, sizeof(TValue));
+            build.dec(counter);
+            build.jcc(Condition::NotZero, repeatNilLoop);
+        }
+
+        build.setLabel(skipResultCopy);
+    }
+
+    build.mov(qword[rState + offsetof(lua_State, ci)], cip);     // L->ci = cip
+    build.mov(rBase, qword[cip + offsetof(CallInfo, base)]);     // sync base = L->base while we have a chance
+    build.mov(qword[rState + offsetof(lua_State, base)], rBase); // L->base = cip->base
+
+    // Start with result for LUA_MULTRET/exit value
+    build.mov(qword[rState + offsetof(lua_State, top)], res); // L->top = res
+
+    // Unlikely, but this might be the last return from VM
+    build.test(byte[ci + offsetof(CallInfo, flags)], LUA_CALLINFO_RETURN);
+    build.jcc(Condition::NotZero, helpers.exitNoContinueVm);
+
+    Label skipFixedRetTop;
+    build.test(nresults, nresults);              // test here will set SF=1 for a negative number and it always sets OF to 0
+    build.jcc(Condition::Less, skipFixedRetTop); // jl jumps if SF != OF
+    build.mov(rax, qword[cip + offsetof(CallInfo, top)]);
+    build.mov(qword[rState + offsetof(lua_State, top)], rax); // L->top = cip->top
+    build.setLabel(skipFixedRetTop);
+
+    // Returning back to the previous function is a bit tricky
+    // Registers alive: r9 (cip)
+    RegisterX64 proto = rcx;
+    RegisterX64 execdata = rbx;
+
+    // Change closure
+    build.mov(rax, qword[cip + offsetof(CallInfo, func)]);
+    build.mov(rax, qword[rax + offsetof(TValue, value.gc)]);
+    build.mov(sClosure, rax);
+
+    build.mov(proto, qword[rax + offsetof(Closure, l.p)]);
+
+    build.mov(execdata, qword[proto + offsetofProtoExecData]);
+    build.test(execdata, execdata);
+    build.jcc(Condition::Zero, helpers.exitContinueVm); // Continue in interpreter if function has no native data
+
+    // Change constants
+    build.mov(rConstants, qword[proto + offsetof(Proto, k)]);
+
+    // Change code
+    build.mov(rdx, qword[proto + offsetof(Proto, code)]);
+    build.mov(sCode, rdx);
+
+    build.mov(rax, qword[cip + offsetof(CallInfo, savedpc)]);
+
+    // To get instruction index from instruction pointer, we need to divide byte offset by 4
+    // But we will actually need to scale instruction index by 8 back to byte offset later so it cancels out
+    build.sub(rax, rdx);
+
+    // Get new instruction location and jump to it
+    build.mov(rdx, qword[execdata + offsetof(NativeProto, instTargets)]);
+    build.jmp(qword[rdx + rax * 2]);
+}
+
 void emitInstJump(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
-    build.jmp(labelarr[pcpos + LUAU_INSN_D(*pc) + 1]);
+    build.jmp(labelarr[pcpos + 1 + LUAU_INSN_D(*pc)]);
 }
 
 void emitInstJumpBack(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     emitInterrupt(build, pcpos);
 
-    build.jmp(labelarr[pcpos + LUAU_INSN_D(*pc) + 1]);
+    build.jmp(labelarr[pcpos + 1 + LUAU_INSN_D(*pc)]);
 }
 
 void emitInstJumpIf(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
 {
     int ra = LUAU_INSN_A(*pc);
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
     Label& exit = labelarr[pcpos + 1];
 
     if (not_)
@@ -102,7 +264,7 @@ void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     int ra = LUAU_INSN_A(*pc);
     int rb = pc[1];
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
     Label& exit = labelarr[pcpos + 2];
 
     build.mov(eax, luauRegTag(ra));
@@ -121,7 +283,7 @@ void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
 void emitInstJumpIfEqFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
 {
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], not_ ? Condition::NotEqual : Condition::Equal, target, pcpos);
 }
@@ -131,7 +293,7 @@ void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pc
     int ra = LUAU_INSN_A(*pc);
     int rb = pc[1];
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     // fast-path: number
     jumpIfTagIsNot(build, ra, LUA_TNUMBER, fallback);
@@ -142,7 +304,7 @@ void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pc
 
 void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond)
 {
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], cond, target, pcpos);
 }
@@ -151,7 +313,7 @@ void emitInstJumpX(AssemblyBuilderX64& build, const Instruction* pc, int pcpos,
 {
     emitInterrupt(build, pcpos);
 
-    build.jmp(labelarr[pcpos + LUAU_INSN_E(*pc) + 1]);
+    build.jmp(labelarr[pcpos + 1 + LUAU_INSN_E(*pc)]);
 }
 
 void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
@@ -159,7 +321,7 @@ void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pc
     int ra = LUAU_INSN_A(*pc);
     bool not_ = (pc[1] & 0x80000000) != 0;
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     build.cmp(luauRegTag(ra), LUA_TNIL);
     build.jcc(not_ ? Condition::NotEqual : Condition::Equal, target);
@@ -171,7 +333,7 @@ void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     uint32_t aux = pc[1];
     bool not_ = (aux & 0x80000000) != 0;
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
     Label& exit = labelarr[pcpos + 2];
 
     jumpIfTagIsNot(build, ra, LUA_TBOOLEAN, not_ ? target : exit);
@@ -187,7 +349,7 @@ void emitInstJumpxEqN(AssemblyBuilderX64& build, const Instruction* pc, const TV
     bool not_ = (aux & 0x80000000) != 0;
     TValue kv = k[aux & 0xffffff];
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
     Label& exit = labelarr[pcpos + 2];
 
     jumpIfTagIsNot(build, ra, LUA_TNUMBER, not_ ? target : exit);
@@ -212,7 +374,7 @@ void emitInstJumpxEqS(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     uint32_t aux = pc[1];
     bool not_ = (aux & 0x80000000) != 0;
 
-    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
     Label& exit = labelarr[pcpos + 2];
 
     jumpIfTagIsNot(build, ra, LUA_TSTRING, not_ ? target : exit);
@@ -596,8 +758,8 @@ void emitInstCloseUpvals(AssemblyBuilderX64& build, const Instruction* pc, int p
     build.call(qword[rNativeContext + offsetof(NativeContext, luaF_close)]);
 }
 
-static void emitInstFastCallN(
-    AssemblyBuilderX64& build, const Instruction* pc, bool customParams, int customParamCount, OperandX64 customArgs, int pcpos, Label* labelarr)
+static int emitInstFastCallN(AssemblyBuilderX64& build, const Instruction* pc, bool customParams, int customParamCount, OperandX64 customArgs,
+    int pcpos, int instLen, Label* labelarr)
 {
     int bfid = LUAU_INSN_A(*pc);
     int skip = LUAU_INSN_C(*pc);
@@ -611,7 +773,7 @@ static void emitInstFastCallN(
     int arg = customParams ? LUAU_INSN_B(*pc) : ra + 1;
     OperandX64 args = customParams ? customArgs : luauRegValue(ra + 2);
 
-    Label exit;
+    Label& exit = labelarr[pcpos + instLen];
 
     jumpIfUnsafeEnv(build, rax, exit);
 
@@ -633,10 +795,7 @@ static void emitInstFastCallN(
             build.mov(qword[rState + offsetof(lua_State, top)], rax);
         }
 
-        // TODO: once we start outlining the fallback, we will be able to fallthrough to the next instruction
-        build.jmp(labelarr[pcpos + skip + 2]);
-        build.setLabel(exit);
-        return;
+        return skip + 2 - instLen; // Return fallback instruction sequence length
     }
 
     // TODO: we can skip saving pc for some well-behaved builtins which we didn't inline
@@ -705,37 +864,35 @@ static void emitInstFastCallN(
         build.mov(qword[rState + offsetof(lua_State, top)], rax);
     }
 
-    build.jmp(labelarr[pcpos + skip + 2]);
-
-    build.setLabel(exit);
-
-    // TODO: fallback to LOP_CALL after a fast call should be outlined
+    return skip + 2 - instLen; // Return fallback instruction sequence length
 }
 
-void emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+int emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
-    emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 1, /* customArgs */ 0, pcpos, labelarr);
+    return emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 1, /* customArgs */ 0, pcpos, /* instLen */ 1, labelarr);
 }
 
-void emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+int emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
-    emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauRegValue(pc[1]), pcpos, labelarr);
+    return emitInstFastCallN(
+        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauRegValue(pc[1]), pcpos, /* instLen */ 2, labelarr);
 }
 
-void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+int emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
-    emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauConstantValue(pc[1]), pcpos, labelarr);
+    return emitInstFastCallN(
+        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauConstantValue(pc[1]), pcpos, /* instLen */ 2, labelarr);
 }
 
-void emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+int emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
-    emitInstFastCallN(build, pc, /* customParams */ false, /* customParamCount */ 0, /* customArgs */ 0, pcpos, labelarr);
+    return emitInstFastCallN(build, pc, /* customParams */ false, /* customParamCount */ 0, /* customArgs */ 0, pcpos, /* instLen */ 1, labelarr);
 }
 
 void emitInstForNPrep(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
-    Label& loopExit = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& loopExit = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     Label tryConvert, exit;
 
@@ -784,7 +941,7 @@ void emitInstForNLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     emitInterrupt(build, pcpos);
 
     int ra = LUAU_INSN_A(*pc);
-    Label& loopRepeat = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+    Label& loopRepeat = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     RegisterX64 limit = xmm0;
     RegisterX64 step = xmm1;
@@ -814,6 +971,162 @@ void emitInstForNLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     build.setLabel(exit);
 }
 
+void emitinstForGLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int aux = pc[1];
+
+    Label& loopRepeat = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
+    Label& exit = labelarr[pcpos + 2];
+
+    emitInterrupt(build, pcpos);
+
+    // fast-path: builtin table iteration
+    jumpIfTagIsNot(build, ra, LUA_TNIL, fallback);
+
+    // Registers are chosen in this way to simplify fallback code for the node part
+    RegisterX64 table = rArg2;
+    RegisterX64 index = rArg3;
+    RegisterX64 elemPtr = rax;
+
+    build.mov(table, luauRegValue(ra + 1));
+    build.mov(index, luauRegValue(ra + 2));
+
+    // &array[index]
+    build.mov(dwordReg(elemPtr), dwordReg(index));
+    build.shl(dwordReg(elemPtr), kTValueSizeLog2);
+    build.add(elemPtr, qword[table + offsetof(Table, array)]);
+
+    // Clear extra variables since we might have more than two
+    for (int i = 2; i < aux; ++i)
+        build.mov(luauRegTag(ra + 3 + i), LUA_TNIL);
+
+    // ipairs-style traversal is terminated early when array part ends of nil array element is encountered
+    bool isIpairsIter = aux < 0;
+
+    Label skipArray, skipArrayNil;
+
+    // First we advance index through the array portion
+    // while (unsigned(index) < unsigned(sizearray))
+    Label arrayLoop = build.setLabel();
+    build.cmp(dwordReg(index), dword[table + offsetof(Table, sizearray)]);
+    build.jcc(Condition::NotBelow, isIpairsIter ? exit : skipArray);
+
+    // If element is nil, we increment the index; if it's not, we still need 'index + 1' inside
+    build.inc(index);
+
+    build.cmp(dword[elemPtr + offsetof(TValue, tt)], LUA_TNIL);
+    build.jcc(Condition::Equal, isIpairsIter ? exit : skipArrayNil);
+
+    // setpvalue(ra + 2, reinterpret_cast<void*>(uintptr_t(index + 1)));
+    build.mov(luauRegValue(ra + 2), index);
+    // Tag should already be set to lightuserdata
+
+    // setnvalue(ra + 3, double(index + 1));
+    build.vcvtsi2sd(xmm0, xmm0, dwordReg(index));
+    build.vmovsd(luauRegValue(ra + 3), xmm0);
+    build.mov(luauRegTag(ra + 3), LUA_TNUMBER);
+
+    // setobj2s(L, ra + 4, e);
+    setLuauReg(build, xmm2, ra + 4, xmmword[elemPtr]);
+
+    build.jmp(loopRepeat);
+
+    if (!isIpairsIter)
+    {
+        build.setLabel(skipArrayNil);
+
+        // Index already incremented, advance to next array element
+        build.add(elemPtr, sizeof(TValue));
+        build.jmp(arrayLoop);
+
+        build.setLabel(skipArray);
+
+        // Call helper to assign next node value or to signal loop exit
+        build.mov(rArg1, rState);
+        // rArg2 and rArg3 are already set
+        build.lea(rArg4, luauRegValue(ra));
+        build.call(qword[rNativeContext + offsetof(NativeContext, forgLoopNodeIter)]);
+        build.test(al, al);
+        build.jcc(Condition::NotZero, loopRepeat);
+    }
+}
+
+void emitinstForGLoopFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int aux = pc[1];
+
+    Label& loopRepeat = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rArg1, rState);
+    build.mov(rArg2, ra);
+    build.mov(rArg3, aux);
+    build.call(qword[rNativeContext + offsetof(NativeContext, forgLoopNonTableFallback)]);
+    emitUpdateBase(build);
+    build.test(al, al);
+    build.jcc(Condition::NotZero, loopRepeat);
+}
+
+void emitInstForGPrepNext(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
+
+    // fast-path: pairs/next
+    jumpIfUnsafeEnv(build, rax, fallback);
+    jumpIfTagIsNot(build, ra + 1, LUA_TTABLE, fallback);
+    jumpIfTagIsNot(build, ra + 2, LUA_TNIL, fallback);
+
+    build.mov(luauRegTag(ra), LUA_TNIL);
+
+    // setpvalue(ra + 2, reinterpret_cast<void*>(uintptr_t(0)));
+    build.mov(luauRegValue(ra + 2), 0);
+    build.mov(luauRegTag(ra + 2), LUA_TLIGHTUSERDATA);
+
+    build.jmp(target);
+}
+
+void emitInstForGPrepInext(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
+
+    // fast-path: ipairs/inext
+    jumpIfUnsafeEnv(build, rax, fallback);
+    jumpIfTagIsNot(build, ra + 1, LUA_TTABLE, fallback);
+    jumpIfTagIsNot(build, ra + 2, LUA_TNUMBER, fallback);
+
+    build.vxorpd(xmm0, xmm0, xmm0);
+    build.vmovsd(xmm1, luauRegValue(ra + 2));
+    jumpOnNumberCmp(build, noreg, xmm0, xmm1, Condition::NotEqual, fallback);
+
+    build.mov(luauRegTag(ra), LUA_TNIL);
+
+    // setpvalue(ra + 2, reinterpret_cast<void*>(uintptr_t(0)));
+    build.mov(luauRegValue(ra + 2), 0);
+    build.mov(luauRegTag(ra + 2), LUA_TLIGHTUSERDATA);
+
+    build.jmp(target);
+}
+
+void emitInstForGPrepXnextFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+
+    Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
+
+    build.mov(rArg1, rState);
+    build.lea(rArg2, luauRegValue(ra));
+    build.mov(rArg3, pcpos + 1);
+    build.call(qword[rNativeContext + offsetof(NativeContext, forgPrepXnextFallback)]);
+    build.jmp(target);
+}
+
 static void emitInstAndX(AssemblyBuilderX64& build, int ra, int rb, OperandX64 c)
 {
     Label target, fallthrough;

CodeGen/src/EmitInstructionX64.h

@@ -16,7 +16,7 @@ namespace CodeGen
 class AssemblyBuilderX64;
 enum class Condition;
 struct Label;
-struct NativeState;
+struct ModuleHelpers;
 
 void emitInstLoadNil(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstLoadB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
@@ -24,6 +24,7 @@ void emitInstLoadN(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstLoadK(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstLoadKX(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc);
+void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJump(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpBack(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpIf(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
@@ -52,12 +53,17 @@ void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
 void emitInstGetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
 void emitInstSetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstCloseUpvals(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+int emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+int emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+int emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+int emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstForNPrep(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstForNLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+void emitinstForGLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitinstForGLoopFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstForGPrepNext(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitInstForGPrepInext(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitInstForGPrepXnextFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstAnd(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstAndK(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstOr(AssemblyBuilderX64& build, const Instruction* pc);

CodeGen/src/NativeState.cpp

@@ -3,6 +3,7 @@
 
 #include "Luau/UnwindBuilder.h"
 
+#include "CodeGenUtils.h"
 #include "CustomExecUtils.h"
 #include "Fallbacks.h"
 
@@ -13,14 +14,10 @@
 #include "lvm.h"
 
 #include <math.h>
+#include <string.h>
 
 #define CODEGEN_SET_FALLBACK(op, flags) data.context.fallback[op] = {execute_##op, flags}
 
-static int luauF_missing(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
-{
-    return -1;
-}
-
 namespace Luau
 {
 namespace CodeGen
@@ -42,11 +39,7 @@ void initFallbackTable(NativeState& data)
     CODEGEN_SET_FALLBACK(LOP_NEWCLOSURE, 0);
     CODEGEN_SET_FALLBACK(LOP_NAMECALL, 0);
     CODEGEN_SET_FALLBACK(LOP_CALL, kFallbackUpdateCi | kFallbackCheckInterrupt);
-    CODEGEN_SET_FALLBACK(LOP_RETURN, kFallbackUpdateCi | kFallbackCheckInterrupt);
     CODEGEN_SET_FALLBACK(LOP_FORGPREP, kFallbackUpdatePc);
-    CODEGEN_SET_FALLBACK(LOP_FORGLOOP, kFallbackUpdatePc | kFallbackCheckInterrupt);
-    CODEGEN_SET_FALLBACK(LOP_FORGPREP_INEXT, kFallbackUpdatePc);
-    CODEGEN_SET_FALLBACK(LOP_FORGPREP_NEXT, kFallbackUpdatePc);
     CODEGEN_SET_FALLBACK(LOP_GETVARARGS, 0);
     CODEGEN_SET_FALLBACK(LOP_DUPCLOSURE, 0);
     CODEGEN_SET_FALLBACK(LOP_PREPVARARGS, 0);
@@ -62,12 +55,8 @@ void initFallbackTable(NativeState& data)
 
 void initHelperFunctions(NativeState& data)
 {
-    static_assert(sizeof(data.context.luauF_table) / sizeof(data.context.luauF_table[0]) == sizeof(luauF_table) / sizeof(luauF_table[0]),
-        "fast call tables are not of the same length");
-
-    // Replace missing fast call functions with an empty placeholder that forces LOP_CALL fallback
-    for (size_t i = 0; i < sizeof(data.context.luauF_table) / sizeof(data.context.luauF_table[0]); i++)
-        data.context.luauF_table[i] = luauF_table[i] ? luauF_table[i] : luauF_missing;
+    static_assert(sizeof(data.context.luauF_table) == sizeof(luauF_table), "fastcall tables are not of the same length");
+    memcpy(data.context.luauF_table, luauF_table, sizeof(luauF_table));
 
     data.context.luaV_lessthan = luaV_lessthan;
     data.context.luaV_lessequal = luaV_lessequal;
@@ -93,6 +82,10 @@ void initHelperFunctions(NativeState& data)
     data.context.luaF_close = luaF_close;
 
     data.context.libm_pow = pow;
+
+    data.context.forgLoopNodeIter = forgLoopNodeIter;
+    data.context.forgLoopNonTableFallback = forgLoopNonTableFallback;
+    data.context.forgPrepXnextFallback = forgPrepXnextFallback;
 }
 
 } // namespace CodeGen

CodeGen/src/NativeState.h

@@ -3,13 +3,16 @@
 
 #include "Luau/Bytecode.h"
 #include "Luau/CodeAllocator.h"
+#include "Luau/Label.h"
 
 #include <memory>
 
 #include <stdint.h>
 
+#include "ldebug.h"
 #include "lobject.h"
 #include "ltm.h"
+#include "lstate.h"
 
 typedef int (*luau_FastFunction)(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams);
 
@@ -77,6 +80,11 @@ struct NativeContext
     void (*luaF_close)(lua_State* L, StkId level) = nullptr;
 
     double (*libm_pow)(double, double) = nullptr;
+
+    // Helper functions
+    bool (*forgLoopNodeIter)(lua_State* L, Table* h, int index, TValue* ra) = nullptr;
+    bool (*forgLoopNonTableFallback)(lua_State* L, int insnA, int aux) = nullptr;
+    void (*forgPrepXnextFallback)(lua_State* L, TValue* ra, int pc) = nullptr;
 };
 
 struct NativeState

Compiler/include/Luau/BytecodeBuilder.h

@@ -117,7 +117,7 @@ public:
     std::string dumpEverything() const;
     std::string dumpSourceRemarks() const;
 
-    void annotateInstruction(std::string& result, uint32_t fid, uint32_t instid) const;
+    void annotateInstruction(std::string& result, uint32_t fid, uint32_t instpos) const;
 
     static uint32_t getImportId(int32_t id0);
     static uint32_t getImportId(int32_t id0, int32_t id1);

Compiler/src/BytecodeBuilder.cpp

@@ -1977,14 +1977,14 @@ std::string BytecodeBuilder::dumpCurrentFunction(std::vector<int>& dumpinstoffs)
         if (labels[i] == 0)
             labels[i] = nextLabel++;
 
-    dumpinstoffs.reserve(insns.size());
+    dumpinstoffs.resize(insns.size() + 1, -1);
 
     for (size_t i = 0; i < insns.size();)
     {
         const uint32_t* code = &insns[i];
         uint8_t op = LUAU_INSN_OP(*code);
 
-        dumpinstoffs.push_back(int(result.size()));
+        dumpinstoffs[i] = int(result.size());
 
         if (op == LOP_PREPVARARGS)
         {
@@ -2028,7 +2028,7 @@ std::string BytecodeBuilder::dumpCurrentFunction(std::vector<int>& dumpinstoffs)
         LUAU_ASSERT(i <= insns.size());
     }
 
-    dumpinstoffs.push_back(int(result.size()));
+    dumpinstoffs[insns.size()] = int(result.size());
 
     return result;
 }
@@ -2119,7 +2119,7 @@ std::string BytecodeBuilder::dumpSourceRemarks() const
     return result;
 }
 
-void BytecodeBuilder::annotateInstruction(std::string& result, uint32_t fid, uint32_t instid) const
+void BytecodeBuilder::annotateInstruction(std::string& result, uint32_t fid, uint32_t instpos) const
 {
     if ((dumpFlags & Dump_Code) == 0)
         return;
@@ -2130,9 +2130,15 @@ void BytecodeBuilder::annotateInstruction(std::string& result, uint32_t fid, uin
     const std::string& dump = function.dump;
     const std::vector<int>& dumpinstoffs = function.dumpinstoffs;
 
-    LUAU_ASSERT(instid + 1 < dumpinstoffs.size());
+    uint32_t next = instpos + 1;
 
-    formatAppend(result, "%.*s", dumpinstoffs[instid + 1] - dumpinstoffs[instid], dump.data() + dumpinstoffs[instid]);
+    LUAU_ASSERT(next < dumpinstoffs.size());
+
+    // Skip locations of multi-dword instructions
+    while (next < dumpinstoffs.size() && dumpinstoffs[next] == -1)
+        next++;
+
+    formatAppend(result, "%.*s", dumpinstoffs[next] - dumpinstoffs[instpos], dump.data() + dumpinstoffs[instpos]);
 }
 
 } // namespace Luau

Makefile

@@ -75,7 +75,7 @@ endif
 
 # configuration-specific flags
 ifeq ($(config),release)
-	CXXFLAGS+=-O2 -DNDEBUG
+	CXXFLAGS+=-O2 -DNDEBUG -fno-math-errno
 endif
 
 ifeq ($(config),coverage)
@@ -102,7 +102,7 @@ ifeq ($(config),fuzz)
 endif
 
 ifeq ($(config),profile)
-	CXXFLAGS+=-O2 -DNDEBUG -gdwarf-4 -DCALLGRIND=1
+	CXXFLAGS+=-O2 -DNDEBUG -fno-math-errno -gdwarf-4 -DCALLGRIND=1
 endif
 
 ifeq ($(protobuf),download)

Sources.cmake

@@ -71,6 +71,7 @@ target_sources(Luau.CodeGen PRIVATE
     CodeGen/src/CodeAllocator.cpp
     CodeGen/src/CodeBlockUnwind.cpp
     CodeGen/src/CodeGen.cpp
+    CodeGen/src/CodeGenUtils.cpp
     CodeGen/src/CodeGenX64.cpp
     CodeGen/src/EmitBuiltinsX64.cpp
     CodeGen/src/EmitCommonX64.cpp
@@ -82,6 +83,7 @@ target_sources(Luau.CodeGen PRIVATE
 
     CodeGen/src/ByteUtils.h
     CodeGen/src/CustomExecUtils.h
+    CodeGen/src/CodeGenUtils.h
     CodeGen/src/CodeGenX64.h
     CodeGen/src/EmitBuiltinsX64.h
     CodeGen/src/EmitCommonX64.h
@@ -339,6 +341,7 @@ if(TARGET Luau.UnitTest)
         tests/TypeInfer.intersectionTypes.test.cpp
         tests/TypeInfer.loops.test.cpp
         tests/TypeInfer.modules.test.cpp
+        tests/TypeInfer.negations.test.cpp
         tests/TypeInfer.oop.test.cpp
         tests/TypeInfer.operators.test.cpp
         tests/TypeInfer.primitives.test.cpp

VM/include/luaconf.h

@@ -20,6 +20,14 @@
 #define LUAU_FASTMATH_END
 #endif
 
+// Some functions like floor/ceil have SSE4.1 equivalents but we currently support systems without SSE4.1
+// On newer GCC and Clang we can use function multi-versioning to generate SSE4.1 code plus CPUID based dispatch.
+#if !defined(__APPLE__) && (defined(__x86_64__) || defined(_M_X64)) && ((defined(__clang__) && __clang_major__ >= 14) || (defined(__GNUC__) && __GNUC__ >= 6)) && !defined(__SSE4_1__)
+#define LUAU_DISPATCH_SSE41 __attribute__((target_clones("default", "sse4.1")))
+#else
+#define LUAU_DISPATCH_SSE41
+#endif
+
 // Used on functions that have a printf-like interface to validate them statically
 #if defined(__GNUC__)
 #define LUA_PRINTF_ATTR(fmt, arg) __attribute__((format(printf, fmt, arg)))

VM/src/lbuiltins.cpp

@@ -96,6 +96,7 @@ static int luauF_atan(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
+LUAU_DISPATCH_SSE41
 static int luauF_ceil(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -159,6 +160,7 @@ static int luauF_exp(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
+LUAU_DISPATCH_SSE41
 static int luauF_floor(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -936,6 +938,7 @@ static int luauF_sign(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
+LUAU_DISPATCH_SSE41
 static int luauF_round(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -1239,7 +1242,12 @@ static int luauF_setmetatable(lua_State* L, StkId res, TValue* arg0, int nresult
     return -1;
 }
 
-luau_FastFunction luauF_table[256] = {
+static int luauF_missing(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
+{
+    return -1;
+}
+
+const luau_FastFunction luauF_table[256] = {
     NULL,
     luauF_assert,
 
@@ -1317,4 +1325,20 @@ luau_FastFunction luauF_table[256] = {
 
     luauF_getmetatable,
     luauF_setmetatable,
+
+    // 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.
+#define MISSING8 luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing
+
+    MISSING8,
+    MISSING8,
+    MISSING8,
+    MISSING8,
+    MISSING8,
+    MISSING8,
+    MISSING8,
+    MISSING8,
+
+#undef MISSING8
 };

VM/src/lbuiltins.h

@@ -6,4 +6,4 @@
 
 typedef int (*luau_FastFunction)(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams);
 
-extern luau_FastFunction luauF_table[256];
+extern const luau_FastFunction luauF_table[256];

VM/src/lnumutils.h

@@ -34,6 +34,7 @@ inline bool luai_vecisnan(const float* a)
 }
 
 LUAU_FASTMATH_BEGIN
+LUAU_DISPATCH_SSE41
 inline double luai_nummod(double a, double b)
 {
     return a - floor(a / b) * b;

VM/src/lvmexecute.cpp

@@ -16,8 +16,6 @@
 
 #include <string.h>
 
-LUAU_FASTFLAGVARIABLE(LuauNoTopRestoreInFastCall, false)
-
 // Disable c99-designator to avoid the warning in CGOTO dispatch table
 #ifdef __clang__
 #if __has_warning("-Wc99-designator")
@@ -2094,12 +2092,17 @@ reentry:
 
                 Table* h = hvalue(ra);
 
+                // TODO: we really don't need this anymore
                 if (!ttistable(ra))
                     return; // temporary workaround to weaken a rather powerful exploitation primitive in case of a MITM attack on bytecode
 
                 int last = index + c - 1;
                 if (last > h->sizearray)
+                {
+                    VM_PROTECT_PC(); // luaH_resizearray may fail due to OOM
+
                     luaH_resizearray(L, h, last);
+                }
 
                 TValue* array = h->array;
 
@@ -2542,8 +2545,9 @@ reentry:
                 nparams = (nparams == LUA_MULTRET) ? int(L->top - ra - 1) : nparams;
 
                 luau_FastFunction f = luauF_table[bfid];
+                LUAU_ASSERT(f);
 
-                if (cl->env->safeenv && f)
+                if (cl->env->safeenv)
                 {
                     VM_PROTECT_PC(); // f may fail due to OOM
 
@@ -2620,8 +2624,9 @@ reentry:
                 int nresults = LUAU_INSN_C(call) - 1;
 
                 luau_FastFunction f = luauF_table[bfid];
+                LUAU_ASSERT(f);
 
-                if (cl->env->safeenv && f)
+                if (cl->env->safeenv)
                 {
                     VM_PROTECT_PC(); // f may fail due to OOM
 
@@ -2629,15 +2634,8 @@ reentry:
 
                     if (n >= 0)
                     {
-                        if (FFlag::LuauNoTopRestoreInFastCall)
-                        {
-                            if (nresults == LUA_MULTRET)
-                                L->top = ra + n;
-                        }
-                        else
-                        {
-                            L->top = (nresults == LUA_MULTRET) ? ra + n : L->ci->top;
-                        }
+                        if (nresults == LUA_MULTRET)
+                            L->top = ra + n;
 
                         pc += skip + 1; // skip instructions that compute function as well as CALL
                         LUAU_ASSERT(unsigned(pc - cl->l.p->code) < unsigned(cl->l.p->sizecode));
@@ -2676,8 +2674,9 @@ reentry:
                 int nresults = LUAU_INSN_C(call) - 1;
 
                 luau_FastFunction f = luauF_table[bfid];
+                LUAU_ASSERT(f);
 
-                if (cl->env->safeenv && f)
+                if (cl->env->safeenv)
                 {
                     VM_PROTECT_PC(); // f may fail due to OOM
 
@@ -2685,15 +2684,8 @@ reentry:
 
                     if (n >= 0)
                     {
-                        if (FFlag::LuauNoTopRestoreInFastCall)
-                        {
-                            if (nresults == LUA_MULTRET)
-                                L->top = ra + n;
-                        }
-                        else
-                        {
-                            L->top = (nresults == LUA_MULTRET) ? ra + n : L->ci->top;
-                        }
+                        if (nresults == LUA_MULTRET)
+                            L->top = ra + n;
 
                         pc += skip + 1; // skip instructions that compute function as well as CALL
                         LUAU_ASSERT(unsigned(pc - cl->l.p->code) < unsigned(cl->l.p->sizecode));
@@ -2732,8 +2724,9 @@ reentry:
                 int nresults = LUAU_INSN_C(call) - 1;
 
                 luau_FastFunction f = luauF_table[bfid];
+                LUAU_ASSERT(f);
 
-                if (cl->env->safeenv && f)
+                if (cl->env->safeenv)
                 {
                     VM_PROTECT_PC(); // f may fail due to OOM
 
@@ -2741,15 +2734,8 @@ reentry:
 
                     if (n >= 0)
                     {
-                        if (FFlag::LuauNoTopRestoreInFastCall)
-                        {
-                            if (nresults == LUA_MULTRET)
-                                L->top = ra + n;
-                        }
-                        else
-                        {
-                            L->top = (nresults == LUA_MULTRET) ? ra + n : L->ci->top;
-                        }
+                        if (nresults == LUA_MULTRET)
+                            L->top = ra + n;
 
                         pc += skip + 1; // skip instructions that compute function as well as CALL
                         LUAU_ASSERT(unsigned(pc - cl->l.p->code) < unsigned(cl->l.p->sizecode));

bench/tests/voxelgen.lua

@@ -0,0 +1,456 @@
+local bench = script and require(script.Parent.bench_support) or require("bench_support")
+
+-- Based on voxel terrain generator by Stickmasterluke
+
+local kSelectedBiomes = {
+    ['Mountains'] = true,
+    ['Canyons'] = true,
+    ['Dunes'] = true,
+    ['Arctic'] = true,
+    ['Lavaflow'] = true,
+    ['Hills'] = true,
+    ['Plains'] = true,
+    ['Marsh'] = true,
+    ['Water'] = true,
+}
+
+---------Directly used in Generation---------
+local masterSeed = 618033988
+local mapWidth = 32
+local mapHeight = 32
+local biomeSize = 16
+local generateCaves = true
+local waterLevel = .48
+local surfaceThickness = .018
+local biomes = {}
+---------------------------------------------
+
+local rock = "Rock"
+local snow = "Snow"
+local ice = "Glacier"
+local grass = "Grass"
+local ground = "Ground"
+local mud = "Mud"
+local slate = "Slate"
+local concrete = "Concrete"
+local lava = "CrackedLava"
+local basalt = "Basalt"
+local air = "Air"
+local sand = "Sand"
+local sandstone = "Sandstone"
+local water = "Water"
+
+math.randomseed(6180339)
+local theseed={}
+for i=1,999 do
+    table.insert(theseed,math.random())
+end
+
+local function getPerlin(x,y,z,seed,scale,raw)
+    local seed = seed or 0
+    local scale = scale or 1
+    if not raw then
+        return math.noise(x/scale+(seed*17)+masterSeed,y/scale-masterSeed,z/scale-seed*seed)*.5 + .5 -- accounts for bleeding from interpolated line
+    else
+        return math.noise(x/scale+(seed*17)+masterSeed,y/scale-masterSeed,z/scale-seed*seed)
+    end
+end
+
+local function getNoise(x,y,z,seed1)
+    local x = x or 0
+    local y = y or 0
+    local z = z or 0
+    local seed1 = seed1 or 7
+    local wtf=x+y+z+seed1+masterSeed + (masterSeed-x)*(seed1+z) + (seed1-y)*(masterSeed+z)      -- + x*(y+z) + z*(masterSeed+seed1) + seed1*(x+y)           --x+y+z+seed1+masterSeed + x*y*masterSeed-y*z+(z+masterSeed)*x  --((x+y)*(y-seed1)*seed1)-(x+z)*seed2+x*11+z*23-y*17
+    return theseed[(math.floor(wtf%(#theseed)))+1]
+end
+
+local function thresholdFilter(value, bottom, size)
+    if value <= bottom then
+        return 0
+    elseif value >= bottom+size then
+        return 1
+    else
+        return (value-bottom)/size
+    end
+end
+
+local function ridgedFilter(value)  --absolute and flip for ridges. and normalize
+    return value<.5 and value*2 or 2-value*2
+end
+
+local function ridgedFlippedFilter(value)                   --unflipped
+    return value < .5 and 1-value*2 or value*2-1
+end
+
+local function advancedRidgedFilter(value, cutoff)
+    local cutoff = cutoff or .5
+    value = value - cutoff
+    return 1 - (value < 0 and -value or value) * 1/(1-cutoff)
+end
+
+local function fractalize(operation,x,y,z, operationCount, scale, offset, gain)
+    local operationCount = operationCount or 3
+    local scale = scale or .5
+    local offset = 0
+    local gain = gain or 1
+    local totalValue = 0
+    local totalScale = 0
+    for i=1, operationCount do
+        local thisScale = scale^(i-1)
+        totalScale = totalScale + thisScale
+        totalValue = totalValue + (offset + gain * operation(x,y,z,i))*thisScale
+    end
+    return totalValue/totalScale
+end
+
+local function mountainsOperation(x,y,z,i)
+    return ridgedFilter(getPerlin(x,y,z,100+i,(1/i)*160))
+end
+
+local canyonBandingMaterial = {rock,mud,sand,sand,sandstone,sandstone,sandstone,sandstone,sandstone,sandstone,}
+
+local function findBiomeInfo(choiceBiome,x,y,z,verticalGradientTurbulence)
+    local choiceBiomeValue = .5
+    local choiceBiomeSurface = grass
+    local choiceBiomeFill = rock
+    if choiceBiome == 'City' then
+        choiceBiomeValue = .55
+        choiceBiomeSurface = concrete
+        choiceBiomeFill = slate
+    elseif choiceBiome == 'Water' then
+        choiceBiomeValue = .36+getPerlin(x,y,z,2,50)*.08
+        choiceBiomeSurface = 
+            (1-verticalGradientTurbulence < .44 and slate)
+            or sand
+    elseif choiceBiome == 'Marsh' then
+        local preLedge = getPerlin(x+getPerlin(x,0,z,5,7,true)*10+getPerlin(x,0,z,6,30,true)*50,0,z+getPerlin(x,0,z,9,7,true)*10+getPerlin(x,0,z,10,30,true)*50,2,70)   --could use some turbulence
+        local grassyLedge = thresholdFilter(preLedge,.65,0)
+        local largeGradient = getPerlin(x,y,z,4,100)
+        local smallGradient = getPerlin(x,y,z,3,20)
+        local smallGradientThreshold = thresholdFilter(smallGradient,.5,0)
+        choiceBiomeValue = waterLevel-.04
+            +preLedge*grassyLedge*.025
+            +largeGradient*.035
+            +smallGradient*.025
+        choiceBiomeSurface =
+            (grassyLedge >= 1 and grass)
+            or (1-verticalGradientTurbulence < waterLevel-.01 and mud)
+            or (1-verticalGradientTurbulence < waterLevel+.01 and ground)
+            or grass
+        choiceBiomeFill = slate
+    elseif choiceBiome == 'Plains' then
+        local rivulet = ridgedFlippedFilter(getPerlin(x+getPerlin(x,y,z,17,40)*25,0,z+getPerlin(x,y,z,19,40)*25,2,200))
+        local rivuletThreshold = thresholdFilter(rivulet,.01,0)
+
+        local rockMap = thresholdFilter(ridgedFlippedFilter(getPerlin(x,0,z,101,7)),.3,.7)      --rocks
+            * thresholdFilter(getPerlin(x,0,z,102,50),.6,.05)                                   --zoning
+
+        choiceBiomeValue = .5           --.51
+        +getPerlin(x,y,z,2,100)*.02     --.05
+        +rivulet*.05                    --.02
+        +rockMap*.05        --.03
+        +rivuletThreshold*.005
+
+        local verticalGradient = 1-((y-1)/(mapHeight-1))
+        local surfaceGradient = verticalGradient*.5 + choiceBiomeValue*.5
+        local thinSurface = surfaceGradient > .5-surfaceThickness*.4 and surfaceGradient < .5+surfaceThickness*.4
+        choiceBiomeSurface =
+            (rockMap>0 and rock)
+            or (not thinSurface and mud)
+            or (thinSurface and rivuletThreshold <=0 and water)
+            or (1-verticalGradientTurbulence < waterLevel-.01 and sand)
+            or grass
+        choiceBiomeFill =
+            (rockMap>0 and rock)
+            or sandstone
+    elseif choiceBiome == 'Canyons' then
+        local canyonNoise = ridgedFlippedFilter(getPerlin(x,0,z,2,200))
+        local canyonNoiseTurbed = ridgedFlippedFilter(getPerlin(x+getPerlin(x,0,z,5,20,true)*20,0,z+getPerlin(x,0,z,9,20,true)*20,2,200))
+        local sandbank = thresholdFilter(canyonNoiseTurbed,0,.05)
+        local canyonTop = thresholdFilter(canyonNoiseTurbed,.125,0)
+        local mesaSlope = thresholdFilter(canyonNoise,.33,.12)
+        local mesaTop = thresholdFilter(canyonNoiseTurbed,.49,0)
+        choiceBiomeValue = .42
+            +getPerlin(x,y,z,2,70)*.05
+            +canyonNoise*.05
+            +sandbank*.04                                       --canyon bottom slope
+            +thresholdFilter(canyonNoiseTurbed,.05,0)*.08       --canyon cliff
+            +thresholdFilter(canyonNoiseTurbed,.05,.075)*.04    --canyon cliff top slope
+            +canyonTop*.01                                      --canyon cliff top ledge
+
+            +thresholdFilter(canyonNoiseTurbed,.0575,.2725)*.01 --plane slope
+
+            +mesaSlope*.06          --mesa slope
+            +thresholdFilter(canyonNoiseTurbed,.45,0)*.14       --mesa cliff
+            +thresholdFilter(canyonNoiseTurbed,.45,.04)*.025    --mesa cap
+            +mesaTop*.02                                        --mesa top ledge
+        choiceBiomeSurface =
+            (1-verticalGradientTurbulence < waterLevel+.015 and sand)       --this for biome blending in to lakes
+            or (sandbank>0 and sandbank<1 and sand)                         --this for canyonbase sandbanks
+            --or (canyonTop>0 and canyonTop<=1 and mesaSlope<=0 and grass)      --this for grassy canyon tops
+            --or (mesaTop>0 and mesaTop<=1 and grass)                           --this for grassy mesa tops
+            or sandstone
+        choiceBiomeFill = canyonBandingMaterial[math.ceil((1-getNoise(1,y,2))*10)]
+    elseif choiceBiome == 'Hills' then
+        local rivulet = ridgedFlippedFilter(getPerlin(x+getPerlin(x,y,z,17,20)*20,0,z+getPerlin(x,y,z,19,20)*20,2,200))^(1/2)
+        local largeHills = getPerlin(x,y,z,3,60)
+        choiceBiomeValue = .48
+            +largeHills*.05
+                +(.05
+                +largeHills*.1
+                +getPerlin(x,y,z,4,25)*.125)
+                *rivulet
+        local surfaceMaterialGradient = (1-verticalGradientTurbulence)*.9 + rivulet*.1
+        choiceBiomeSurface =
+            (surfaceMaterialGradient < waterLevel-.015 and mud)
+            or (surfaceMaterialGradient < waterLevel and ground)
+            or grass
+        choiceBiomeFill = slate
+    elseif choiceBiome == 'Dunes' then
+        local duneTurbulence = getPerlin(x,0,z,227,20)*24
+        local layer1 = ridgedFilter(getPerlin(x,0,z,201,40))
+        local layer2 = ridgedFilter(getPerlin(x/10+duneTurbulence,0,z+duneTurbulence,200,48))
+        choiceBiomeValue = .4+.1*(layer1 + layer2)
+        choiceBiomeSurface = sand
+        choiceBiomeFill = sandstone
+    elseif choiceBiome == 'Mountains' then
+        local rivulet = ridgedFlippedFilter(getPerlin(x+getPerlin(x,y,z,17,20)*20,0,z+getPerlin(x,y,z,19,20)*20,2,200))
+        choiceBiomeValue = -.4      --.3
+            +fractalize(mountainsOperation,x,y/20,z, 8, .65)*1.2
+            +rivulet*.2
+        choiceBiomeSurface =
+            (verticalGradientTurbulence < .275 and snow)
+            or (verticalGradientTurbulence < .35 and rock)
+            or (verticalGradientTurbulence < .4 and ground)
+            or (1-verticalGradientTurbulence < waterLevel and rock)
+            or (1-verticalGradientTurbulence < waterLevel+.01 and mud)
+            or (1-verticalGradientTurbulence < waterLevel+.015 and ground)
+            or grass
+    elseif choiceBiome == 'Lavaflow' then
+        local crackX = x+getPerlin(x,y*.25,z,21,8,true)*5
+        local crackY = y+getPerlin(x,y*.25,z,22,8,true)*5
+        local crackZ = z+getPerlin(x,y*.25,z,23,8,true)*5
+        local crack1 = ridgedFilter(getPerlin(crackX+getPerlin(x,y,z,22,30,true)*30,crackY,crackZ+getPerlin(x,y,z,24,30,true)*30,2,120))
+        local crack2 = ridgedFilter(getPerlin(crackX,crackY,crackZ,3,40))*(crack1*.25+.75)
+        local crack3 = ridgedFilter(getPerlin(crackX,crackY,crackZ,4,20))*(crack2*.25+.75)
+
+        local generalHills = thresholdFilter(getPerlin(x,y,z,9,40),.25,.5)*getPerlin(x,y,z,10,60)
+
+        local cracks = math.max(0,1-thresholdFilter(crack1,.975,0)-thresholdFilter(crack2,.925,0)-thresholdFilter(crack3,.9,0))
+
+        local spires = thresholdFilter(getPerlin(crackX/40,crackY/300,crackZ/30,123,1),.6,.4)
+
+        choiceBiomeValue = waterLevel+.02
+            +cracks*(.5+generalHills*.5)*.02
+            +generalHills*.05
+            +spires*.3
+            +((1-verticalGradientTurbulence > waterLevel+.01 or spires>0) and .04 or 0)         --This lets it lip over water
+
+        choiceBiomeFill = (spires>0 and rock) or (cracks<1 and lava) or basalt
+        choiceBiomeSurface = (choiceBiomeFill == lava and 1-verticalGradientTurbulence < waterLevel and basalt) or choiceBiomeFill
+    elseif choiceBiome == 'Arctic' then
+        local preBoundary = getPerlin(x+getPerlin(x,0,z,5,8,true)*5,y/8,z+getPerlin(x,0,z,9,8,true)*5,2,20)
+        --local cliffs = thresholdFilter(preBoundary,.5,0)
+        local boundary = ridgedFilter(preBoundary)
+        local roughChunks = getPerlin(x,y/4,z,436,2)
+        local boundaryMask = thresholdFilter(boundary,.8,.1)    --,.7,.25)
+        local boundaryTypeMask = getPerlin(x,0,z,6,74)-.5
+        local boundaryComp = 0
+        if boundaryTypeMask < 0 then                            --divergent
+            boundaryComp = (boundary > (1+boundaryTypeMask*.5) and -.17 or 0)
+                            --* boundaryTypeMask*-2
+        else                                                    --convergent
+            boundaryComp = boundaryMask*.1*roughChunks
+                            * boundaryTypeMask
+        end
+        choiceBiomeValue = .55
+            +boundary*.05*boundaryTypeMask      --.1    --soft slope up or down to boundary
+            +boundaryComp                               --convergent/divergent effects
+            +getPerlin(x,0,z,123,25)*.025   --*cliffs   --gentle rolling slopes
+
+        choiceBiomeSurface = (1-verticalGradientTurbulence < waterLevel-.1 and ice) or (boundaryMask>.6 and boundaryTypeMask>.1 and roughChunks>.5 and ice) or snow
+        choiceBiomeFill = ice
+    end
+    return choiceBiomeValue, choiceBiomeSurface, choiceBiomeFill
+end
+
+function findBiomeTransitionValue(biome,weight,value,averageValue)
+    if biome == 'Arctic' then
+        return (weight>.2 and 1 or 0)*value
+    elseif biome == 'Canyons' then
+        return (weight>.7 and 1 or 0)*value
+    elseif biome == 'Mountains' then
+        local weight = weight^3         --This improves the ease of mountains transitioning to other biomes
+        return averageValue*(1-weight)+value*weight
+    else
+        return averageValue*(1-weight)+value*weight
+    end
+end
+
+function generate()
+    local mapWidth = mapWidth
+    local biomeSize = biomeSize
+    local biomeBlendPercent = .25   --(biomeSize==50 or biomeSize == 100) and .5 or .25
+    local biomeBlendPercentInverse = 1-biomeBlendPercent
+    local biomeBlendDistortion = biomeBlendPercent
+    local smoothScale = .5/mapHeight
+
+    biomes = {}
+    for i,v in pairs(kSelectedBiomes) do
+        if v then
+            table.insert(biomes,i)
+        end
+    end
+    if #biomes<=0 then
+        table.insert(biomes,'Hills')
+    end
+    table.sort(biomes)
+    --local oMap = {}
+    --local mMap = {}
+    for x = 1, mapWidth do
+        local oMapX = {}
+        --oMap[x] = oMapX
+        local mMapX = {}
+        --mMap[x] = mMapX
+        for z = 1, mapWidth do
+            local biomeNoCave = false
+            local cellToBiomeX = x/biomeSize + getPerlin(x,0,z,233,biomeSize*.3)*.25 + getPerlin(x,0,z,235,biomeSize*.05)*.075
+            local cellToBiomeZ = z/biomeSize + getPerlin(x,0,z,234,biomeSize*.3)*.25 + getPerlin(x,0,z,236,biomeSize*.05)*.075
+            local closestDistance = 1000000
+            local biomePoints = {}
+            for vx=-1,1 do
+                for vz=-1,1 do
+                    local gridPointX = math.floor(cellToBiomeX+vx+.5)
+                    local gridPointZ = math.floor(cellToBiomeZ+vz+.5)
+                    --local pointX, pointZ = getBiomePoint(gridPointX,gridPointZ)
+                    local pointX = gridPointX+(getNoise(gridPointX,gridPointZ,53)-.5)*.75   --de-uniforming grid for vornonoi
+                    local pointZ = gridPointZ+(getNoise(gridPointX,gridPointZ,73)-.5)*.75
+
+                    local dist = math.sqrt((pointX-cellToBiomeX)^2 + (pointZ-cellToBiomeZ)^2)
+                    if dist < closestDistance then
+                        closestDistance = dist
+                    end
+                    table.insert(biomePoints,{
+                        x = pointX,
+                        z = pointZ,
+                        dist = dist,
+                        biomeNoise = getNoise(gridPointX,gridPointZ),
+                        weight = 0
+                    })
+                end
+            end
+            local weightTotal = 0
+            local weightPoints = {}
+            for _,point in pairs(biomePoints) do
+                local weight = point.dist == closestDistance and 1 or ((closestDistance / point.dist)-biomeBlendPercentInverse)/biomeBlendPercent
+                if weight > 0 then
+                    local weight = weight^2.1       --this smooths the biome transition from linear to cubic InOut
+                    weightTotal = weightTotal + weight
+                    local biome = biomes[math.ceil(#biomes*(1-point.biomeNoise))]   --inverting the noise so that it is limited as (0,1]. One less addition operation when finding a random list index
+                    weightPoints[biome] = {
+                        weight = weightPoints[biome] and weightPoints[biome].weight + weight or weight
+                    }
+                end
+            end
+            for biome,info in pairs(weightPoints) do
+                info.weight = info.weight / weightTotal
+                if biome == 'Arctic' then       --biomes that don't have caves that breach the surface
+                    biomeNoCave = true
+                end
+            end
+
+
+            for y = 1, mapHeight do
+                local oMapY = oMapX[y] or {}
+                oMapX[y] = oMapY
+                local mMapY = mMapX[y] or {}
+                mMapX[y] = mMapY
+
+                --[[local oMapY = {}
+                oMapX[y] = oMapY
+                local mMapY = {}
+                mMapX[z] = mMapY]]
+
+
+                local verticalGradient = 1-((y-1)/(mapHeight-1))
+                local caves = 0
+                local verticalGradientTurbulence = verticalGradient*.9 + .1*getPerlin(x,y,z,107,15)
+                local choiceValue = 0
+                local choiceSurface = lava
+                local choiceFill = rock
+
+                if verticalGradient > .65 or verticalGradient < .1 then
+                    --under surface of every biome; don't get biome data; waste of time.
+                    choiceValue = .5
+                elseif #biomes == 1 then
+                    choiceValue, choiceSurface, choiceFill = findBiomeInfo(biomes[1],x,y,z,verticalGradientTurbulence)
+                else
+                    local averageValue = 0
+                    --local findChoiceMaterial = -getNoise(x,y,z,19)
+                    for biome,info in pairs(weightPoints) do
+                        local biomeValue, biomeSurface, biomeFill = findBiomeInfo(biome,x,y,z,verticalGradientTurbulence)
+                        info.biomeValue = biomeValue
+                        info.biomeSurface = biomeSurface
+                        info.biomeFill = biomeFill
+                        local value = biomeValue * info.weight
+                        averageValue = averageValue + value
+                        --[[if findChoiceMaterial < 0 and findChoiceMaterial + weight >= 0 then
+                            choiceMaterial = biomeMaterial
+                        end
+                        findChoiceMaterial = findChoiceMaterial + weight]]
+                    end
+                    for biome,info in pairs(weightPoints) do
+                        local value = findBiomeTransitionValue(biome,info.weight,info.biomeValue,averageValue)
+                        if value > choiceValue then
+                            choiceValue = value
+                            choiceSurface = info.biomeSurface
+                            choiceFill = info.biomeFill
+                        end
+                    end
+                end
+
+                local preCaveComp = verticalGradient*.5 + choiceValue*.5
+
+                local surface = preCaveComp > .5-surfaceThickness and preCaveComp < .5+surfaceThickness
+
+                if generateCaves                                                                --user wants caves
+                    and (not biomeNoCave or verticalGradient > .65)                             --biome allows caves or deep enough
+                        and not (surface and (1-verticalGradient) < waterLevel+.005)            --caves only breach surface above waterlevel
+                            and not (surface and (1-verticalGradient) > waterLevel+.58) then    --caves don't go too high so that they don't cut up mountain tops
+                                local ridged2 = ridgedFilter(getPerlin(x,y,z,4,30))
+                                local caves2 = thresholdFilter(ridged2,.84,.01)
+                                local ridged3 = ridgedFilter(getPerlin(x,y,z,5,30))
+                                local caves3 = thresholdFilter(ridged3,.84,.01)
+                                local ridged4 = ridgedFilter(getPerlin(x,y,z,6,30))
+                                local caves4 = thresholdFilter(ridged4,.84,.01)
+                                local caveOpenings = (surface and 1 or 0) * thresholdFilter(getPerlin(x,0,z,143,62),.35,0)  --.45
+                                caves = caves2 * caves3 * caves4 - caveOpenings
+                                caves = caves < 0 and 0 or caves > 1 and 1 or caves
+                end
+
+                local comp = preCaveComp - caves
+
+                local smoothedResult = thresholdFilter(comp,.5,smoothScale)
+
+                ---below water level                  -above surface        -no terrain
+                if 1-verticalGradient < waterLevel and preCaveComp <= .5 and smoothedResult <= 0 then
+                    smoothedResult = 1
+                    choiceSurface = water
+                    choiceFill = water
+                    surface = true
+                end
+
+                oMapY[z] = (y == 1 and 1) or smoothedResult
+                mMapY[z] = (y == 1 and lava) or (smoothedResult <= 0 and air) or (surface and choiceSurface) or choiceFill
+            end
+        end
+
+        -- local regionStart = Vector3.new(mapWidth*-2+(x-1)*4,mapHeight*-2,mapWidth*-2)
+        -- local regionEnd = Vector3.new(mapWidth*-2+x*4,mapHeight*2,mapWidth*2)
+        -- local mapRegion = Region3.new(regionStart, regionEnd)
+        -- terrain:WriteVoxels(mapRegion, 4, {mMapX}, {oMapX})
+    end
+end
+
+bench.runCode(generate, "voxelgen")

tests/AstQuery.test.cpp

@@ -91,6 +91,8 @@ TEST_CASE_FIXTURE(DocumentationSymbolFixture, "class_method")
 
 TEST_CASE_FIXTURE(DocumentationSymbolFixture, "overloaded_class_method")
 {
+    ScopedFastFlag luauCheckOverloadedDocSymbol{"LuauCheckOverloadedDocSymbol", true};
+
     loadDefinition(R"(
         declare class Foo
             function bar(self, x: string): number
@@ -125,6 +127,8 @@ TEST_CASE_FIXTURE(DocumentationSymbolFixture, "table_function_prop")
 
 TEST_CASE_FIXTURE(DocumentationSymbolFixture, "table_overloaded_function_prop")
 {
+    ScopedFastFlag luauCheckOverloadedDocSymbol{"LuauCheckOverloadedDocSymbol", true};
+
     loadDefinition(R"(
         declare Foo: {
             new: ((number) -> string) & ((string) -> number)

tests/Fixture.cpp

@@ -506,6 +506,15 @@ std::optional<TypeId> linearSearchForBinding(Scope* scope, const char* name)
     return std::nullopt;
 }
 
+void registerNotType(Fixture& fixture, TypeArena& arena)
+{
+    TypeId t = arena.addType(GenericTypeVar{"T"});
+    GenericTypeDefinition genericT{t};
+
+    ScopePtr moduleScope = fixture.frontend.getGlobalScope();
+    moduleScope->exportedTypeBindings["Not"] = TypeFun{{genericT}, arena.addType(NegationTypeVar{t})};
+}
+
 void dump(const std::vector<Constraint>& constraints)
 {
     ToStringOptions opts;

tests/Fixture.h

@@ -186,6 +186,8 @@ std::optional<TypeId> lookupName(ScopePtr scope, const std::string& name); // Wa
 
 std::optional<TypeId> linearSearchForBinding(Scope* scope, const char* name);
 
+void registerNotType(Fixture& fixture, TypeArena& arena);
+
 } // namespace Luau
 
 #define LUAU_REQUIRE_ERRORS(result) \

tests/Module.test.cpp

@@ -11,6 +11,7 @@
 using namespace Luau;
 
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+LUAU_FASTFLAG(LuauIceExceptionInheritanceChange);
 
 TEST_SUITE_BEGIN("ModuleTests");
 
@@ -278,7 +279,14 @@ TEST_CASE_FIXTURE(Fixture, "clone_recursion_limit")
     TypeArena dest;
     CloneState cloneState;
 
-    CHECK_THROWS_AS(clone(table, dest, cloneState), RecursionLimitException);
+    if (FFlag::LuauIceExceptionInheritanceChange)
+    {
+        CHECK_THROWS_AS(clone(table, dest, cloneState), RecursionLimitException);
+    }
+    else
+    {
+        CHECK_THROWS_AS(clone(table, dest, cloneState), RecursionLimitException_DEPRECATED);
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "any_persistance_does_not_leak")

tests/Normalize.test.cpp

@@ -10,13 +10,16 @@
 
 using namespace Luau;
 
-struct NormalizeFixture : Fixture
+namespace
+{
+struct IsSubtypeFixture : Fixture
 {
     bool isSubtype(TypeId a, TypeId b)
     {
         return ::Luau::isSubtype(a, b, NotNull{getMainModule()->getModuleScope().get()}, singletonTypes, ice);
     }
 };
+}
 
 void createSomeClasses(Frontend& frontend)
 {
@@ -55,7 +58,7 @@ void createSomeClasses(Frontend& frontend)
 
 TEST_SUITE_BEGIN("isSubtype");
 
-TEST_CASE_FIXTURE(NormalizeFixture, "primitives")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "primitives")
 {
     check(R"(
         local a = 41
@@ -75,7 +78,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "primitives")
     CHECK(!isSubtype(d, a));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "functions")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "functions")
 {
     check(R"(
         function a(x: number): number return x end
@@ -96,7 +99,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "functions")
     CHECK(isSubtype(a, d));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "functions_and_any")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_and_any")
 {
     check(R"(
         function a(n: number) return "string" end
@@ -114,7 +117,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "functions_and_any")
     CHECK(!isSubtype(a, b));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "variadic_functions_with_no_head")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "variadic_functions_with_no_head")
 {
     check(R"(
         local a: (...number) -> ()
@@ -129,7 +132,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "variadic_functions_with_no_head")
 }
 
 #if 0
-TEST_CASE_FIXTURE(NormalizeFixture, "variadic_function_with_head")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "variadic_function_with_head")
 {
     check(R"(
         local a: (...number) -> ()
@@ -144,7 +147,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "variadic_function_with_head")
 }
 #endif
 
-TEST_CASE_FIXTURE(NormalizeFixture, "union")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "union")
 {
     check(R"(
         local a: number | string
@@ -171,7 +174,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "union")
     CHECK(!isSubtype(d, b));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "table_with_union_prop")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "table_with_union_prop")
 {
     check(R"(
         local a: {x: number}
@@ -185,7 +188,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "table_with_union_prop")
     CHECK(!isSubtype(b, a));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "table_with_any_prop")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "table_with_any_prop")
 {
     check(R"(
         local a: {x: number}
@@ -199,7 +202,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "table_with_any_prop")
     CHECK(!isSubtype(b, a));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "intersection")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "intersection")
 {
     ScopedFastFlag sffs[]{
         {"LuauSubtypeNormalizer", true},
@@ -229,7 +232,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "intersection")
     CHECK(isSubtype(a, d));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "union_and_intersection")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "union_and_intersection")
 {
     check(R"(
             local a: number & string
@@ -243,7 +246,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "union_and_intersection")
     CHECK(isSubtype(a, b));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "tables")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "tables")
 {
     check(R"(
         local a: {x: number}
@@ -271,7 +274,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "tables")
 }
 
 #if 0
-TEST_CASE_FIXTURE(NormalizeFixture, "table_indexers_are_invariant")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "table_indexers_are_invariant")
 {
     check(R"(
         local a: {[string]: number}
@@ -290,7 +293,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "table_indexers_are_invariant")
     CHECK(isSubtype(a, c));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "mismatched_indexers")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "mismatched_indexers")
 {
     check(R"(
         local a: {x: number}
@@ -309,7 +312,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "mismatched_indexers")
     CHECK(isSubtype(b, c));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "cyclic_table")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "cyclic_table")
 {
     check(R"(
         type A = {method: (A) -> ()}
@@ -348,7 +351,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "cyclic_table")
 }
 #endif
 
-TEST_CASE_FIXTURE(NormalizeFixture, "classes")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "classes")
 {
     createSomeClasses(frontend);
 
@@ -365,7 +368,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "classes")
 }
 
 #if 0
-TEST_CASE_FIXTURE(NormalizeFixture, "metatable" * doctest::expected_failures{1})
+TEST_CASE_FIXTURE(IsSubtypeFixture, "metatable" * doctest::expected_failures{1})
 {
      check(R"(
         local T = {}
@@ -389,8 +392,112 @@ TEST_CASE_FIXTURE(NormalizeFixture, "metatable" * doctest::expected_failures{1})
 
 TEST_SUITE_END();
 
+struct NormalizeFixture : Fixture
+{
+    ScopedFastFlag sff{"LuauNegatedStringSingletons", true};
+
+    TypeArena arena;
+    InternalErrorReporter iceHandler;
+    UnifierSharedState unifierState{&iceHandler};
+    Normalizer normalizer{&arena, singletonTypes, NotNull{&unifierState}};
+
+    NormalizeFixture()
+    {
+        registerNotType(*this, arena);
+    }
+
+    TypeId normal(const std::string& annotation)
+    {
+        CheckResult result = check("type _Res = " + annotation);
+        LUAU_REQUIRE_NO_ERRORS(result);
+        std::optional<TypeId> ty = lookupType("_Res");
+        REQUIRE(ty);
+        const NormalizedType* norm = normalizer.normalize(*ty);
+        REQUIRE(norm);
+        return normalizer.typeFromNormal(*norm);
+    }
+};
+
 TEST_SUITE_BEGIN("Normalize");
 
+TEST_CASE_FIXTURE(NormalizeFixture, "negate_string")
+{
+    CHECK("number" == toString(normal(R"(
+        (number | string) & Not<string>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "negate_string_from_cofinite_string_intersection")
+{
+    CHECK("number" == toString(normal(R"(
+        (number | (string & Not<"hello"> & Not<"world">)) & Not<string>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "no_op_negation_is_dropped")
+{
+    CHECK("number" == toString(normal(R"(
+        number & Not<string>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "union_of_negation")
+{
+    CHECK("string" == toString(normal(R"(
+        (string & Not<"hello">) | "hello"
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "intersect_truthy")
+{
+    CHECK("number | string | true" == toString(normal(R"(
+        (string | number | boolean | nil) & Not<false | nil>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "intersect_truthy_expressed_as_intersection")
+{
+    CHECK("number | string | true" == toString(normal(R"(
+        (string | number | boolean | nil) & Not<false> & Not<nil>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "union_of_union")
+{
+    CHECK(R"("alpha" | "beta" | "gamma")" == toString(normal(R"(
+        ("alpha" | "beta") | "gamma"
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "union_of_negations")
+{
+    CHECK(R"(string & ~"world")" == toString(normal(R"(
+        (string & Not<"hello"> & Not<"world">) | (string & Not<"goodbye"> & Not<"world">)
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "negate_boolean")
+{
+    CHECK("true" == toString(normal(R"(
+        boolean & Not<false>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "negate_boolean_2")
+{
+    CHECK("never" == toString(normal(R"(
+        true & Not<true>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "bare_negation")
+{
+    // TODO: We don't yet have a way to say number | string | thread | nil | Class | Table | Function
+    CHECK("(number | string | thread)?" == toString(normal(R"(
+        Not<boolean>
+    )")));
+}
+
 TEST_CASE_FIXTURE(Fixture, "higher_order_function")
 {
     check(R"(

tests/Parser.test.cpp

@@ -1736,8 +1736,6 @@ TEST_CASE_FIXTURE(Fixture, "parse_error_type_annotation")
 
 TEST_CASE_FIXTURE(Fixture, "parse_error_missing_type_annotation")
 {
-    ScopedFastFlag LuauTypeAnnotationLocationChange{"LuauTypeAnnotationLocationChange", true};
-
     {
         ParseResult result = tryParse("local x:");
         CHECK(result.errors.size() == 1);

tests/ToString.test.cpp

@@ -512,9 +512,11 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "toStringDetailed2")
 
     TableTypeVar* tMeta5 = getMutable<TableTypeVar>(tMeta4->props["__index"].type);
     REQUIRE(tMeta5);
+    REQUIRE(tMeta5->props.count("one") > 0);
 
     TableTypeVar* tMeta6 = getMutable<TableTypeVar>(tMeta3->table);
     REQUIRE(tMeta6);
+    REQUIRE(tMeta6->props.count("two") > 0);
 
     ToStringResult oneResult = toStringDetailed(tMeta5->props["one"].type, opts);
     if (!FFlag::LuauFixNameMaps)

tests/TypeInfer.aliases.test.cpp

@@ -913,4 +913,14 @@ TEST_CASE_FIXTURE(Fixture, "it_is_ok_to_shadow_user_defined_alias")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "cannot_create_cyclic_type_with_unknown_module")
+{
+    CheckResult result = check(R"(
+        type AAA = B.AAA
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK(toString(result.errors[0]) == "Unknown type 'B.AAA'");
+}
+
 TEST_SUITE_END();

tests/TypeInfer.annotations.test.cpp

@@ -7,6 +7,8 @@
 
 #include "doctest.h"
 
+LUAU_FASTFLAG(LuauIceExceptionInheritanceChange)
+
 using namespace Luau;
 
 TEST_SUITE_BEGIN("AnnotationTests");
@@ -664,8 +666,8 @@ TEST_CASE_FIXTURE(Fixture, "luau_ice_triggers_an_ice_exception_with_flag")
     AssertionCatcher ac;
 
     CHECK_THROWS_AS(check(R"(
-            local a: _luau_ice = 55
-        )"),
+        local a: _luau_ice = 55
+    )"),
         InternalCompilerError);
 
     LUAU_ASSERT(1 == AssertionCatcher::tripped);
@@ -682,8 +684,8 @@ TEST_CASE_FIXTURE(Fixture, "luau_ice_triggers_an_ice_exception_with_flag_handler
     };
 
     CHECK_THROWS_AS(check(R"(
-            local a: _luau_ice = 55
-        )"),
+        local a: _luau_ice = 55
+    )"),
         InternalCompilerError);
 
     CHECK_EQ(true, caught);

tests/TypeInfer.anyerror.test.cpp

@@ -348,8 +348,6 @@ TEST_CASE_FIXTURE(Fixture, "prop_access_on_any_with_other_options")
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "union_of_types_regression_test")
 {
-    ScopedFastFlag LuauUnionOfTypesFollow{"LuauUnionOfTypesFollow", true};
-
     CheckResult result = check(R"(
 --!strict
 local stat

tests/TypeInfer.definitions.test.cpp

@@ -309,6 +309,23 @@ TEST_CASE_FIXTURE(Fixture, "definitions_documentation_symbols")
     CHECK_EQ(yTtv->props["x"].documentationSymbol, "@test/global/y.x");
 }
 
+TEST_CASE_FIXTURE(Fixture, "definitions_symbols_are_generated_for_recursively_referenced_types")
+{
+    ScopedFastFlag LuauPersistTypesAfterGeneratingDocSyms("LuauPersistTypesAfterGeneratingDocSyms", true);
+
+    loadDefinition(R"(
+        declare class MyClass
+            function myMethod(self)
+        end
+
+        declare function myFunc(): MyClass
+    )");
+
+    std::optional<TypeFun> myClassTy = typeChecker.globalScope->lookupType("MyClass");
+    REQUIRE(bool(myClassTy));
+    CHECK_EQ(myClassTy->type->documentationSymbol, "@test/globaltype/MyClass");
+}
+
 TEST_CASE_FIXTURE(Fixture, "documentation_symbols_dont_attach_to_persistent_types")
 {
     loadDefinition(R"(

tests/TypeInfer.functions.test.cpp

@@ -229,6 +229,48 @@ TEST_CASE_FIXTURE(Fixture, "too_many_arguments")
     CHECK_EQ(0, acm->actual);
 }
 
+TEST_CASE_FIXTURE(Fixture, "too_many_arguments_error_location")
+{
+    ScopedFastFlag sff{"LuauArgMismatchReportFunctionLocation", true};
+
+    CheckResult result = check(R"(
+        --!strict
+
+        function myfunction(a: number, b:number) end
+        myfunction(1)
+
+        function getmyfunction()
+            return myfunction
+        end
+        getmyfunction()()
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+
+    {
+        TypeError err = result.errors[0];
+
+        // Ensure the location matches the location of the function identifier
+        CHECK_EQ(err.location, Location(Position(4, 8), Position(4, 18)));
+
+        auto acm = get<CountMismatch>(err);
+        REQUIRE(acm);
+        CHECK_EQ(2, acm->expected);
+        CHECK_EQ(1, acm->actual);
+    }
+    {
+        TypeError err = result.errors[1];
+
+        // Ensure the location matches the location of the expression returning the function
+        CHECK_EQ(err.location, Location(Position(9, 8), Position(9, 23)));
+
+        auto acm = get<CountMismatch>(err);
+        REQUIRE(acm);
+        CHECK_EQ(2, acm->expected);
+        CHECK_EQ(0, acm->actual);
+    }
+}
+
 TEST_CASE_FIXTURE(Fixture, "recursive_function")
 {
     CheckResult result = check(R"(
@@ -1659,17 +1701,20 @@ foo3()
 string.find()
 
 local t = {}
-function t.foo(x: number, y: string?, ...: any) end
+function t.foo(x: number, y: string?, ...: any) return 1 end
 function t:bar(x: number, y: string?) end
 t.foo()
 
 t:bar()
 
-local u = { a = t }
+local u = { a = t, b = function() return t end }
 u.a.foo()
+local x = (u.a).foo()
+
+u.b().foo()
     )");
 
-    LUAU_REQUIRE_ERROR_COUNT(7, result);
+    LUAU_REQUIRE_ERROR_COUNT(9, result);
     CHECK_EQ(toString(result.errors[0]), "Argument count mismatch. Function 'foo1' expects 1 argument, but none are specified");
     CHECK_EQ(toString(result.errors[1]), "Argument count mismatch. Function 'foo2' expects 1 to 2 arguments, but none are specified");
     CHECK_EQ(toString(result.errors[2]), "Argument count mismatch. Function 'foo3' expects 1 to 3 arguments, but none are specified");
@@ -1677,6 +1722,8 @@ u.a.foo()
     CHECK_EQ(toString(result.errors[4]), "Argument count mismatch. Function 't.foo' expects at least 1 argument, but none are specified");
     CHECK_EQ(toString(result.errors[5]), "Argument count mismatch. Function 't.bar' expects 2 to 3 arguments, but only 1 is specified");
     CHECK_EQ(toString(result.errors[6]), "Argument count mismatch. Function 'u.a.foo' expects at least 1 argument, but none are specified");
+    CHECK_EQ(toString(result.errors[7]), "Argument count mismatch. Function 'u.a.foo' expects at least 1 argument, but none are specified");
+    CHECK_EQ(toString(result.errors[8]), "Argument count mismatch. Function expects at least 1 argument, but none are specified");
 }
 
 // This might be surprising, but since 'any' became optional, unannotated functions in non-strict 'expect' 0 arguments

tests/TypeInfer.modules.test.cpp

@@ -251,23 +251,7 @@ end
 return m
 )");
 
-    if (FFlag::LuauInstantiateInSubtyping)
-    {
-        // though this didn't error before the flag, it seems as though it should error since fields of a table are invariant.
-        // the user's intent would likely be that these "method" fields would be read-only, but without an annotation, accepting this should be
-        // unsound.
-
-        LUAU_REQUIRE_ERROR_COUNT(1, result);
-
-        CHECK_EQ(R"(Type 'n' could not be converted into 't1 where t1 = {- Clone: (t1) -> (a...) -}'
-caused by:
-  Property 'Clone' is not compatible. Type '<a>(a) -> ()' could not be converted into 't1 where t1 = ({- Clone: t1 -}) -> (a...)'; different number of generic type parameters)",
-            toString(result.errors[0]));
-    }
-    else
-    {
-        LUAU_REQUIRE_NO_ERRORS(result);
-    }
+    LUAU_REQUIRE_NO_ERRORS(result);
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "custom_require_global")

tests/TypeInfer.negations.test.cpp

@@ -0,0 +1,52 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Fixture.h"
+
+#include "doctest.h"
+#include "Luau/Common.h"
+#include "ScopedFlags.h"
+
+using namespace Luau;
+
+namespace
+{
+struct NegationFixture : Fixture
+{
+    TypeArena arena;
+    ScopedFastFlag sff[2] {
+        {"LuauNegatedStringSingletons", true},
+        {"LuauSubtypeNormalizer", true},
+    };
+
+    NegationFixture()
+    {
+        registerNotType(*this, arena);
+    }
+};
+}
+
+TEST_SUITE_BEGIN("Negations");
+
+TEST_CASE_FIXTURE(NegationFixture, "negated_string_is_a_subtype_of_string")
+{
+    CheckResult result = check(R"(
+        function foo(arg: string) end
+        local a: string & Not<"Hello">
+        foo(a)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(NegationFixture, "string_is_not_a_subtype_of_negated_string")
+{
+    CheckResult result = check(R"(
+        function foo(arg: string & Not<"hello">) end
+        local a: string
+        foo(a)
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.operators.test.cpp

@@ -434,16 +434,17 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_unary_minus")
 {
     CheckResult result = check(R"(
         --!strict
-        local foo = {
-            value = 10
-        }
+        local foo
         local mt = {}
-        setmetatable(foo, mt)
 
         mt.__unm = function(val: typeof(foo)): string
-            return val.value .. "test"
+            return tostring(val.value) .. "test"
         end
 
+        foo = setmetatable({
+            value = 10
+        }, mt)
+
         local a = -foo
 
         local b = 1+-1
@@ -459,25 +460,32 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_unary_minus")
     CHECK_EQ("string", toString(requireType("a")));
     CHECK_EQ("number", toString(requireType("b")));
 
-    GenericError* gen = get<GenericError>(result.errors[0]);
-    REQUIRE_EQ(gen->message, "Unary operator '-' not supported by type 'bar'");
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+    {
+        CHECK(toString(result.errors[0]) == "Type '{ value: number }' could not be converted into 'number'");
+    }
+    else
+    {
+        GenericError* gen = get<GenericError>(result.errors[0]);
+        REQUIRE(gen);
+        REQUIRE_EQ(gen->message, "Unary operator '-' not supported by type 'bar'");
+    }
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_unary_minus_error")
 {
     CheckResult result = check(R"(
         --!strict
-        local foo = {
-            value = 10
-        }
-
         local mt = {}
-        setmetatable(foo, mt)
 
         mt.__unm = function(val: boolean): string
             return "test"
         end
 
+        local foo = setmetatable({
+            value = 10
+        }, mt)
+
         local a = -foo
     )");
 
@@ -494,16 +502,16 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_unary_len_error")
 {
     CheckResult result = check(R"(
         --!strict
-        local foo = {
-            value = 10
-        }
         local mt = {}
-        setmetatable(foo, mt)
 
-        mt.__len = function(val: any): string
+        mt.__len = function(val): string
             return "test"
         end
 
+        local foo = setmetatable({
+            value = 10,
+        }, mt)
+
         local a = #foo
     )");
 

tests/TypeInfer.provisional.test.cpp

@@ -624,15 +624,18 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_with_a_singleton_argument")
     CHECK_EQ("{string | string}", toString(requireType("t")));
 }
 
-struct NormalizeFixture : Fixture
+namespace
+{
+struct IsSubtypeFixture : Fixture
 {
     bool isSubtype(TypeId a, TypeId b)
     {
         return ::Luau::isSubtype(a, b, NotNull{getMainModule()->getModuleScope().get()}, singletonTypes, ice);
     }
 };
+}
 
-TEST_CASE_FIXTURE(NormalizeFixture, "intersection_of_functions_of_different_arities")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "intersection_of_functions_of_different_arities")
 {
     check(R"(
         type A = (any) -> ()
@@ -653,7 +656,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "intersection_of_functions_of_different_arit
     CHECK("((any) -> ()) & ((any, any) -> ())" == toString(requireType("t")));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "functions_with_mismatching_arity")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_with_mismatching_arity")
 {
     check(R"(
         local a: (number) -> ()
@@ -676,7 +679,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "functions_with_mismatching_arity")
     CHECK(!isSubtype(b, c));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "functions_with_mismatching_arity_but_optional_parameters")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_with_mismatching_arity_but_optional_parameters")
 {
     /*
      * (T0..TN) <: (T0..TN, A?)
@@ -736,7 +739,7 @@ TEST_CASE_FIXTURE(NormalizeFixture, "functions_with_mismatching_arity_but_option
     // CHECK(!isSubtype(b, c));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "functions_with_mismatching_arity_but_any_is_an_optional_param")
+TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_with_mismatching_arity_but_any_is_an_optional_param")
 {
     check(R"(
         local a: (number?) -> ()

tests/TypeInfer.tables.test.cpp

@@ -1,5 +1,8 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/BuiltinDefinitions.h"
+#include "Luau/Common.h"
+#include "Luau/Frontend.h"
+#include "Luau/ToString.h"
 #include "Luau/TypeInfer.h"
 #include "Luau/TypeVar.h"
 
@@ -14,6 +17,7 @@ using namespace Luau;
 LUAU_FASTFLAG(LuauLowerBoundsCalculation);
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
+LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
 
 TEST_SUITE_BEGIN("TableTests");
 
@@ -1957,7 +1961,11 @@ TEST_CASE_FIXTURE(Fixture, "invariant_table_properties_means_instantiating_table
         local c : string = t.m("hi")
     )");
 
-    LUAU_REQUIRE_ERRORS(result);
+    // TODO: test behavior is wrong with LuauInstantiateInSubtyping until we can re-enable the covariant requirement for instantiation in subtyping
+    if (FFlag::LuauInstantiateInSubtyping)
+        LUAU_REQUIRE_NO_ERRORS(result);
+    else
+        LUAU_REQUIRE_ERRORS(result);
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_should_cope_with_optional_properties_in_nonstrict")
@@ -3262,11 +3270,13 @@ TEST_CASE_FIXTURE(Fixture, "invariant_table_properties_means_instantiating_table
         local c : string = t.m("hi")
     )");
 
-    LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 't' could not be converted into '{| m: (number) -> number |}'
-caused by:
-  Property 'm' is not compatible. Type '<a>(a) -> a' could not be converted into '(number) -> number'; different number of generic type parameters)");
-    // this error message is not great since the underlying issue is that the context is invariant,
+    LUAU_REQUIRE_NO_ERRORS(result);
+    // TODO: test behavior is wrong until we can re-enable the covariant requirement for instantiation in subtyping
+//     LUAU_REQUIRE_ERRORS(result);
+//     CHECK_EQ(toString(result.errors[0]), R"(Type 't' could not be converted into '{| m: (number) -> number |}'
+// caused by:
+//   Property 'm' is not compatible. Type '<a>(a) -> a' could not be converted into '(number) -> number'; different number of generic type parameters)");
+//     // this error message is not great since the underlying issue is that the context is invariant,
     // and `(number) -> number` cannot be a subtype of `<a>(a) -> a`.
 }
 
@@ -3292,4 +3302,43 @@ local g : ({ p : number, q : string }) -> ({ p : number, r : boolean }) = f
     CHECK_EQ("r", error->properties[0]);
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "setmetatable_has_a_side_effect")
+{
+    if (!FFlag::DebugLuauDeferredConstraintResolution)
+        return;
+
+    CheckResult result = check(R"(
+        local mt = {
+            __add = function(x, y)
+                return 123
+            end,
+        }
+
+        local foo = {}
+        setmetatable(foo, mt)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK(toString(requireType("foo")) == "{ @metatable { __add: (a, b) -> number }, {  } }");
+}
+
+TEST_CASE_FIXTURE(BuiltinsFixture, "tables_should_be_fully_populated")
+{
+    CheckResult result = check(R"(
+        local t = {
+            x = 5 :: NonexistingTypeWhichEndsUpReturningAnErrorType,
+            y = 5
+        }
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    ToStringOptions opts;
+    opts.exhaustive = true;
+    if (FFlag::LuauSpecialTypesAsterisked)
+        CHECK_EQ("{ x: *error-type*, y: number }", toString(requireType("t"), opts));
+    else
+        CHECK_EQ("{ x: <error-type>, y: number }", toString(requireType("t"), opts));
+}
+
 TEST_SUITE_END();

tests/VisitTypeVar.test.cpp

@@ -22,7 +22,14 @@ TEST_CASE_FIXTURE(Fixture, "throw_when_limit_is_exceeded")
 
     TypeId tType = requireType("t");
 
-    CHECK_THROWS_AS(toString(tType), RecursionLimitException);
+    if (FFlag::LuauIceExceptionInheritanceChange)
+    {
+        CHECK_THROWS_AS(toString(tType), RecursionLimitException);
+    }
+    else
+    {
+        CHECK_THROWS_AS(toString(tType), RecursionLimitException_DEPRECATED);
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "dont_throw_when_limit_is_high_enough")

tools/faillist.txt

@@ -1,14 +1,14 @@
-AnnotationTests.builtin_types_are_not_exported
 AnnotationTests.corecursive_types_error_on_tight_loop
 AnnotationTests.duplicate_type_param_name
 AnnotationTests.for_loop_counter_annotation_is_checked
 AnnotationTests.generic_aliases_are_cloned_properly
 AnnotationTests.instantiation_clone_has_to_follow
+AnnotationTests.luau_print_is_not_special_without_the_flag
 AnnotationTests.occurs_check_on_cyclic_intersection_typevar
 AnnotationTests.occurs_check_on_cyclic_union_typevar
 AnnotationTests.too_many_type_params
 AnnotationTests.two_type_params
-AnnotationTests.use_type_required_from_another_file
+AnnotationTests.unknown_type_reference_generates_error
 AstQuery.last_argument_function_call_type
 AstQuery::getDocumentationSymbolAtPosition.overloaded_fn
 AutocompleteTest.autocomplete_first_function_arg_expected_type
@@ -86,7 +86,6 @@ BuiltinTests.table_pack
 BuiltinTests.table_pack_reduce
 BuiltinTests.table_pack_variadic
 BuiltinTests.tonumber_returns_optional_number_type
-BuiltinTests.tonumber_returns_optional_number_type2
 DefinitionTests.class_definition_overload_metamethods
 DefinitionTests.class_definition_string_props
 DefinitionTests.declaring_generic_functions
@@ -96,7 +95,6 @@ FrontendTest.imported_table_modification_2
 FrontendTest.it_should_be_safe_to_stringify_errors_when_full_type_graph_is_discarded
 FrontendTest.nocheck_cycle_used_by_checked
 FrontendTest.reexport_cyclic_type
-FrontendTest.reexport_type_alias
 FrontendTest.trace_requires_in_nonstrict_mode
 GenericsTests.apply_type_function_nested_generics1
 GenericsTests.apply_type_function_nested_generics2
@@ -105,7 +103,6 @@ GenericsTests.calling_self_generic_methods
 GenericsTests.check_generic_typepack_function
 GenericsTests.check_mutual_generic_functions
 GenericsTests.correctly_instantiate_polymorphic_member_functions
-GenericsTests.do_not_always_instantiate_generic_intersection_types
 GenericsTests.do_not_infer_generic_functions
 GenericsTests.duplicate_generic_type_packs
 GenericsTests.duplicate_generic_types
@@ -143,7 +140,6 @@ IntersectionTypes.table_write_sealed_indirect
 ModuleTests.any_persistance_does_not_leak
 ModuleTests.clone_self_property
 ModuleTests.deepClone_cyclic_table
-ModuleTests.do_not_clone_reexports
 NonstrictModeTests.for_in_iterator_variables_are_any
 NonstrictModeTests.function_parameters_are_any
 NonstrictModeTests.inconsistent_module_return_types_are_ok
@@ -158,7 +154,6 @@ NonstrictModeTests.parameters_having_type_any_are_optional
 NonstrictModeTests.table_dot_insert_and_recursive_calls
 NonstrictModeTests.table_props_are_any
 Normalize.cyclic_table_normalizes_sensibly
-Normalize.intersection_combine_on_bound_self
 ParseErrorRecovery.generic_type_list_recovery
 ParseErrorRecovery.recovery_of_parenthesized_expressions
 ParserTests.parse_nesting_based_end_detection_failsafe_earlier
@@ -249,7 +244,6 @@ TableTests.defining_a_self_method_for_a_builtin_sealed_table_must_fail
 TableTests.defining_a_self_method_for_a_local_sealed_table_must_fail
 TableTests.dont_crash_when_setmetatable_does_not_produce_a_metatabletypevar
 TableTests.dont_hang_when_trying_to_look_up_in_cyclic_metatable_index
-TableTests.dont_invalidate_the_properties_iterator_of_free_table_when_rolled_back
 TableTests.dont_leak_free_table_props
 TableTests.dont_quantify_table_that_belongs_to_outer_scope
 TableTests.dont_suggest_exact_match_keys
@@ -279,7 +273,6 @@ TableTests.inferring_crazy_table_should_also_be_quick
 TableTests.instantiate_table_cloning_3
 TableTests.invariant_table_properties_means_instantiating_tables_in_call_is_unsound
 TableTests.leaking_bad_metatable_errors
-TableTests.length_operator_union_errors
 TableTests.less_exponential_blowup_please
 TableTests.meta_add
 TableTests.meta_add_both_ways
@@ -347,9 +340,9 @@ TryUnifyTests.members_of_failed_typepack_unification_are_unified_with_errorType
 TryUnifyTests.result_of_failed_typepack_unification_is_constrained
 TryUnifyTests.typepack_unification_should_trim_free_tails
 TryUnifyTests.variadics_should_use_reversed_properly
+TypeAliases.cannot_create_cyclic_type_with_unknown_module
 TypeAliases.forward_declared_alias_is_not_clobbered_by_prior_unification_with_any
 TypeAliases.generic_param_remap
-TypeAliases.mismatched_generic_pack_type_param
 TypeAliases.mismatched_generic_type_param
 TypeAliases.mutually_recursive_types_restriction_not_ok_1
 TypeAliases.mutually_recursive_types_restriction_not_ok_2
@@ -363,7 +356,7 @@ TypeAliases.type_alias_fwd_declaration_is_precise
 TypeAliases.type_alias_local_mutation
 TypeAliases.type_alias_local_rename
 TypeAliases.type_alias_of_an_imported_recursive_generic_type
-TypeAliases.type_alias_of_an_imported_recursive_type
+TypeInfer.check_type_infer_recursion_count
 TypeInfer.checking_should_not_ice
 TypeInfer.cli_50041_committing_txnlog_in_apollo_client_error
 TypeInfer.dont_report_type_errors_within_an_AstExprError
@@ -394,6 +387,7 @@ TypeInferClasses.warn_when_prop_almost_matches
 TypeInferClasses.we_can_report_when_someone_is_trying_to_use_a_table_rather_than_a_class
 TypeInferFunctions.calling_function_with_anytypepack_doesnt_leak_free_types
 TypeInferFunctions.calling_function_with_incorrect_argument_type_yields_errors_spanning_argument
+TypeInferFunctions.cannot_hoist_interior_defns_into_signature
 TypeInferFunctions.dont_give_other_overloads_message_if_only_one_argument_matching_overload_exists
 TypeInferFunctions.dont_infer_parameter_types_for_functions_from_their_call_site
 TypeInferFunctions.duplicate_functions_with_different_signatures_not_allowed_in_nonstrict
@@ -439,12 +433,9 @@ TypeInferLoops.varlist_declared_by_for_in_loop_should_be_free
 TypeInferModules.bound_free_table_export_is_ok
 TypeInferModules.custom_require_global
 TypeInferModules.do_not_modify_imported_types
-TypeInferModules.do_not_modify_imported_types_2
-TypeInferModules.do_not_modify_imported_types_3
 TypeInferModules.module_type_conflict
 TypeInferModules.module_type_conflict_instantiated
 TypeInferModules.require_a_variadic_function
-TypeInferModules.require_types
 TypeInferModules.type_error_of_unknown_qualified_type
 TypeInferOOP.CheckMethodsOfSealed
 TypeInferOOP.dont_suggest_using_colon_rather_than_dot_if_another_overload_works
@@ -468,9 +459,6 @@ TypeInferOperators.produce_the_correct_error_message_when_comparing_a_table_with
 TypeInferOperators.refine_and_or
 TypeInferOperators.typecheck_overloaded_multiply_that_is_an_intersection
 TypeInferOperators.typecheck_overloaded_multiply_that_is_an_intersection_on_rhs
-TypeInferOperators.typecheck_unary_len_error
-TypeInferOperators.typecheck_unary_minus
-TypeInferOperators.typecheck_unary_minus_error
 TypeInferOperators.UnknownGlobalCompoundAssign
 TypeInferPrimitives.CheckMethodsOfNumber
 TypeInferPrimitives.singleton_types
@@ -489,6 +477,7 @@ TypeInferUnknownNever.math_operators_and_never
 TypeInferUnknownNever.type_packs_containing_never_is_itself_uninhabitable
 TypeInferUnknownNever.type_packs_containing_never_is_itself_uninhabitable2
 TypeInferUnknownNever.unary_minus_of_never
+TypePackTests.detect_cyclic_typepacks2
 TypePackTests.higher_order_function
 TypePackTests.pack_tail_unification_check
 TypePackTests.parenthesized_varargs_returns_any