Sync to upstream/release/590 (#1008)

* Better indentation in multi-line type mismatch error messages
* Error message clone can no longer cause a stack overflow (when
typechecking with retainFullTypeGraphs set to false); fixes
https://github.com/Roblox/luau/issues/975
* `string.format` with %s is now ~2x faster on strings smaller than 100
characters

Native code generation:
* All VM side exits will block return to the native execution of the
current function to preserve correctness
* Fixed executable page allocation on Apple platforms when using
hardened runtime
* Added statistics for code generation (no. of functions compiler,
memory used for different areas)
* Fixed issue with function entry type checks performed more that once
in some functions

Analysis/include/Luau/Clone.h

@@ -16,6 +16,8 @@ using SeenTypePacks = std::unordered_map<TypePackId, TypePackId>;
 
 struct CloneState
 {
+    NotNull<BuiltinTypes> builtinTypes;
+
     SeenTypes seenTypes;
     SeenTypePacks seenTypePacks;
 

Analysis/include/Luau/Config.h

@@ -1,7 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
-#include "Luau/Linter.h"
+#include "Luau/LinterConfig.h"
 #include "Luau/ParseOptions.h"
 
 #include <string>

Analysis/include/Luau/Differ.h

@@ -128,10 +128,10 @@ struct DiffError
         checkValidInitialization(left, right);
     }
 
-    std::string toString() const;
+    std::string toString(bool multiLine = false) const;
 
 private:
-    std::string toStringALeaf(std::string rootName, const DiffPathNodeLeaf& leaf, const DiffPathNodeLeaf& otherLeaf) const;
+    std::string toStringALeaf(std::string rootName, const DiffPathNodeLeaf& leaf, const DiffPathNodeLeaf& otherLeaf, bool multiLine) const;
     void checkValidInitialization(const DiffPathNodeLeaf& left, const DiffPathNodeLeaf& right);
     void checkNonMissingPropertyLeavesHaveNulloptTableProperty() const;
 };
@@ -152,12 +152,17 @@ struct DifferEnvironment
 {
     TypeId rootLeft;
     TypeId rootRight;
+    std::optional<std::string> externalSymbolLeft;
+    std::optional<std::string> externalSymbolRight;
     DenseHashMap<TypeId, TypeId> genericMatchedPairs;
     DenseHashMap<TypePackId, TypePackId> genericTpMatchedPairs;
 
-    DifferEnvironment(TypeId rootLeft, TypeId rootRight)
+    DifferEnvironment(
+        TypeId rootLeft, TypeId rootRight, std::optional<std::string> externalSymbolLeft, std::optional<std::string> externalSymbolRight)
         : rootLeft(rootLeft)
         , rootRight(rootRight)
+        , externalSymbolLeft(externalSymbolLeft)
+        , externalSymbolRight(externalSymbolRight)
         , genericMatchedPairs(nullptr)
         , genericTpMatchedPairs(nullptr)
     {
@@ -170,6 +175,8 @@ struct DifferEnvironment
     void popVisiting();
     std::vector<std::pair<TypeId, TypeId>>::const_reverse_iterator visitingBegin() const;
     std::vector<std::pair<TypeId, TypeId>>::const_reverse_iterator visitingEnd() const;
+    std::string getDevFixFriendlyNameLeft() const;
+    std::string getDevFixFriendlyNameRight() const;
 
 private:
     // TODO: consider using DenseHashSet
@@ -179,6 +186,7 @@ private:
     std::vector<std::pair<TypeId, TypeId>> visitingStack;
 };
 DifferResult diff(TypeId ty1, TypeId ty2);
+DifferResult diffWithSymbols(TypeId ty1, TypeId ty2, std::optional<std::string> symbol1, std::optional<std::string> symbol2);
 
 /**
  * True if ty is a "simple" type, i.e. cannot contain types.

Analysis/include/Luau/Error.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "Luau/Location.h"
+#include "Luau/NotNull.h"
 #include "Luau/Type.h"
 #include "Luau/Variant.h"
 
@@ -432,7 +433,7 @@ std::string toString(const TypeError& error, TypeErrorToStringOptions options);
 bool containsParseErrorName(const TypeError& error);
 
 // Copy any types named in the error into destArena.
-void copyErrors(ErrorVec& errors, struct TypeArena& destArena);
+void copyErrors(ErrorVec& errors, struct TypeArena& destArena, NotNull<BuiltinTypes> builtinTypes);
 
 // Internal Compiler Error
 struct InternalErrorReporter

Analysis/include/Luau/Linter.h

@@ -1,6 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/LinterConfig.h"
 #include "Luau/Location.h"
 
 #include <memory>
@@ -15,86 +16,15 @@ class AstStat;
 class AstNameTable;
 struct TypeChecker;
 struct Module;
-struct HotComment;
 
 using ScopePtr = std::shared_ptr<struct Scope>;
 
-struct LintWarning
-{
-    // Make sure any new lint codes are documented here: https://luau-lang.org/lint
-    // Note that in Studio, the active set of lint warnings is determined by FStringStudioLuauLints
-    enum Code
-    {
-        Code_Unknown = 0,
-
-        Code_UnknownGlobal = 1, // superseded by type checker
-        Code_DeprecatedGlobal = 2,
-        Code_GlobalUsedAsLocal = 3,
-        Code_LocalShadow = 4,       // disabled in Studio
-        Code_SameLineStatement = 5, // disabled in Studio
-        Code_MultiLineStatement = 6,
-        Code_LocalUnused = 7,    // disabled in Studio
-        Code_FunctionUnused = 8, // disabled in Studio
-        Code_ImportUnused = 9,   // disabled in Studio
-        Code_BuiltinGlobalWrite = 10,
-        Code_PlaceholderRead = 11,
-        Code_UnreachableCode = 12,
-        Code_UnknownType = 13,
-        Code_ForRange = 14,
-        Code_UnbalancedAssignment = 15,
-        Code_ImplicitReturn = 16, // disabled in Studio, superseded by type checker in strict mode
-        Code_DuplicateLocal = 17,
-        Code_FormatString = 18,
-        Code_TableLiteral = 19,
-        Code_UninitializedLocal = 20,
-        Code_DuplicateFunction = 21,
-        Code_DeprecatedApi = 22,
-        Code_TableOperations = 23,
-        Code_DuplicateCondition = 24,
-        Code_MisleadingAndOr = 25,
-        Code_CommentDirective = 26,
-        Code_IntegerParsing = 27,
-        Code_ComparisonPrecedence = 28,
-
-        Code__Count
-    };
-
-    Code code;
-    Location location;
-    std::string text;
-
-    static const char* getName(Code code);
-    static Code parseName(const char* name);
-    static uint64_t parseMask(const std::vector<HotComment>& hotcomments);
-};
-
 struct LintResult
 {
     std::vector<LintWarning> errors;
     std::vector<LintWarning> warnings;
 };
 
-struct LintOptions
-{
-    uint64_t warningMask = 0;
-
-    void enableWarning(LintWarning::Code code)
-    {
-        warningMask |= 1ull << code;
-    }
-    void disableWarning(LintWarning::Code code)
-    {
-        warningMask &= ~(1ull << code);
-    }
-
-    bool isEnabled(LintWarning::Code code) const
-    {
-        return 0 != (warningMask & (1ull << code));
-    }
-
-    void setDefaults();
-};
-
 std::vector<LintWarning> lint(AstStat* root, const AstNameTable& names, const ScopePtr& env, const Module* module,
     const std::vector<HotComment>& hotcomments, const LintOptions& options);
 

Analysis/include/Luau/LinterConfig.h

@@ -0,0 +1,121 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Location.h"
+
+#include <string>
+#include <vector>
+
+namespace Luau
+{
+
+struct HotComment;
+
+struct LintWarning
+{
+    // Make sure any new lint codes are documented here: https://luau-lang.org/lint
+    // Note that in Studio, the active set of lint warnings is determined by FStringStudioLuauLints
+    enum Code
+    {
+        Code_Unknown = 0,
+
+        Code_UnknownGlobal = 1, // superseded by type checker
+        Code_DeprecatedGlobal = 2,
+        Code_GlobalUsedAsLocal = 3,
+        Code_LocalShadow = 4,       // disabled in Studio
+        Code_SameLineStatement = 5, // disabled in Studio
+        Code_MultiLineStatement = 6,
+        Code_LocalUnused = 7,    // disabled in Studio
+        Code_FunctionUnused = 8, // disabled in Studio
+        Code_ImportUnused = 9,   // disabled in Studio
+        Code_BuiltinGlobalWrite = 10,
+        Code_PlaceholderRead = 11,
+        Code_UnreachableCode = 12,
+        Code_UnknownType = 13,
+        Code_ForRange = 14,
+        Code_UnbalancedAssignment = 15,
+        Code_ImplicitReturn = 16, // disabled in Studio, superseded by type checker in strict mode
+        Code_DuplicateLocal = 17,
+        Code_FormatString = 18,
+        Code_TableLiteral = 19,
+        Code_UninitializedLocal = 20,
+        Code_DuplicateFunction = 21,
+        Code_DeprecatedApi = 22,
+        Code_TableOperations = 23,
+        Code_DuplicateCondition = 24,
+        Code_MisleadingAndOr = 25,
+        Code_CommentDirective = 26,
+        Code_IntegerParsing = 27,
+        Code_ComparisonPrecedence = 28,
+
+        Code__Count
+    };
+
+    Code code;
+    Location location;
+    std::string text;
+
+    static const char* getName(Code code);
+    static Code parseName(const char* name);
+    static uint64_t parseMask(const std::vector<HotComment>& hotcomments);
+};
+
+struct LintOptions
+{
+    uint64_t warningMask = 0;
+
+    void enableWarning(LintWarning::Code code)
+    {
+        warningMask |= 1ull << code;
+    }
+    void disableWarning(LintWarning::Code code)
+    {
+        warningMask &= ~(1ull << code);
+    }
+
+    bool isEnabled(LintWarning::Code code) const
+    {
+        return 0 != (warningMask & (1ull << code));
+    }
+
+    void setDefaults();
+};
+
+// clang-format off
+static const char* kWarningNames[] = {
+    "Unknown",
+
+    "UnknownGlobal",
+    "DeprecatedGlobal",
+    "GlobalUsedAsLocal",
+    "LocalShadow",
+    "SameLineStatement",
+    "MultiLineStatement",
+    "LocalUnused",
+    "FunctionUnused",
+    "ImportUnused",
+    "BuiltinGlobalWrite",
+    "PlaceholderRead",
+    "UnreachableCode",
+    "UnknownType",
+    "ForRange",
+    "UnbalancedAssignment",
+    "ImplicitReturn",
+    "DuplicateLocal",
+    "FormatString",
+    "TableLiteral",
+    "UninitializedLocal",
+    "DuplicateFunction",
+    "DeprecatedApi",
+    "TableOperations",
+    "DuplicateCondition",
+    "MisleadingAndOr",
+    "CommentDirective",
+    "IntegerParsing",
+    "ComparisonPrecedence",
+};
+// clang-format on
+
+static_assert(std::size(kWarningNames) == unsigned(LintWarning::Code__Count), "did you forget to add warning to the list?");
+
+} // namespace Luau

Analysis/include/Luau/Substitution.h

@@ -147,9 +147,6 @@ struct Tarjan
     void visitEdge(int index, int parentIndex);
     void visitSCC(int index);
 
-    TarjanResult loop_DEPRECATED();
-    void visitSCC_DEPRECATED(int index);
-
     // Each subclass can decide to ignore some nodes.
     virtual bool ignoreChildren(TypeId ty)
     {
@@ -178,13 +175,6 @@ struct Tarjan
     virtual bool isDirty(TypePackId tp) = 0;
     virtual void foundDirty(TypeId ty) = 0;
     virtual void foundDirty(TypePackId tp) = 0;
-
-    // TODO: remove with FFlagLuauTarjanSingleArr
-    std::vector<TypeId> indexToType;
-    std::vector<TypePackId> indexToPack;
-    std::vector<bool> onStack;
-    std::vector<int> lowlink;
-    std::vector<bool> dirty;
 };
 
 // And finally substitution, which finds all the reachable dirty vertices

Analysis/src/Clone.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/Clone.h"
 
+#include "Luau/NotNull.h"
 #include "Luau/RecursionCounter.h"
 #include "Luau/TxnLog.h"
 #include "Luau/TypePack.h"
@@ -13,12 +14,424 @@ LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTINTVARIABLE(LuauTypeCloneRecursionLimit, 300)
 LUAU_FASTFLAGVARIABLE(LuauCloneCyclicUnions, false)
 
+LUAU_FASTFLAGVARIABLE(LuauStacklessTypeClone, false)
+LUAU_FASTINTVARIABLE(LuauTypeCloneIterationLimit, 100'000)
+
 namespace Luau
 {
 
 namespace
 {
 
+using Kind = Variant<TypeId, TypePackId>;
+
+template<typename T>
+const T* get(const Kind& kind)
+{
+    return get_if<T>(&kind);
+}
+
+class TypeCloner2
+{
+    NotNull<TypeArena> arena;
+    NotNull<BuiltinTypes> builtinTypes;
+
+    // A queue of kinds where we cloned it, but whose interior types hasn't
+    // been updated to point to new clones. Once all of its interior types
+    // has been updated, it gets removed from the queue.
+    std::vector<Kind> queue;
+
+    NotNull<SeenTypes> types;
+    NotNull<SeenTypePacks> packs;
+
+    int steps = 0;
+
+public:
+    TypeCloner2(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, NotNull<SeenTypes> types, NotNull<SeenTypePacks> packs)
+        : arena(arena)
+        , builtinTypes(builtinTypes)
+        , types(types)
+        , packs(packs)
+    {
+    }
+
+    TypeId clone(TypeId ty)
+    {
+        shallowClone(ty);
+        run();
+
+        if (hasExceededIterationLimit())
+        {
+            TypeId error = builtinTypes->errorRecoveryType();
+            (*types)[ty] = error;
+            return error;
+        }
+
+        return find(ty).value_or(builtinTypes->errorRecoveryType());
+    }
+
+    TypePackId clone(TypePackId tp)
+    {
+        shallowClone(tp);
+        run();
+
+        if (hasExceededIterationLimit())
+        {
+            TypePackId error = builtinTypes->errorRecoveryTypePack();
+            (*packs)[tp] = error;
+            return error;
+        }
+
+        return find(tp).value_or(builtinTypes->errorRecoveryTypePack());
+    }
+
+private:
+    bool hasExceededIterationLimit() const
+    {
+        if (FInt::LuauTypeCloneIterationLimit == 0)
+            return false;
+
+        return steps + queue.size() >= size_t(FInt::LuauTypeCloneIterationLimit);
+    }
+
+    void run()
+    {
+        while (!queue.empty())
+        {
+            ++steps;
+
+            if (hasExceededIterationLimit())
+                break;
+
+            Kind kind = queue.back();
+            queue.pop_back();
+
+            if (find(kind))
+                continue;
+
+            cloneChildren(kind);
+        }
+    }
+
+    std::optional<TypeId> find(TypeId ty) const
+    {
+        if (auto it = types->find(ty); it != types->end())
+            return it->second;
+        return std::nullopt;
+    }
+
+    std::optional<TypePackId> find(TypePackId tp) const
+    {
+        if (auto it = packs->find(tp); it != packs->end())
+            return it->second;
+        return std::nullopt;
+    }
+
+    std::optional<Kind> find(Kind kind) const
+    {
+        if (auto ty = get<TypeId>(kind))
+            return find(*ty);
+        else if (auto tp = get<TypePackId>(kind))
+            return find(*tp);
+        else
+        {
+            LUAU_ASSERT(!"Unknown kind?");
+            return std::nullopt;
+        }
+    }
+
+private:
+    TypeId shallowClone(TypeId ty)
+    {
+        if (auto clone = find(ty))
+            return *clone;
+        else if (ty->persistent)
+            return ty;
+
+        // We want to [`Luau::follow`] but without forcing the expansion of [`LazyType`]s.
+        TypeId target = nullptr;
+        if (auto bt = get<BoundType>(ty))
+            target = bt->boundTo;
+        else if (auto tt = get<TableType>(ty); tt && tt->boundTo)
+            target = *tt->boundTo;
+        else
+        {
+            target = arena->addType(ty->ty);
+            asMutable(target)->documentationSymbol = ty->documentationSymbol;
+        }
+
+        LUAU_ASSERT(target);
+        (*types)[ty] = target;
+        queue.push_back(target);
+        return target;
+    }
+
+    TypePackId shallowClone(TypePackId tp)
+    {
+        if (auto clone = find(tp))
+            return *clone;
+        else if (tp->persistent)
+            return tp;
+
+        TypePackId target;
+        if (auto btp = get<BoundTypePack>(tp))
+            target = btp->boundTo;
+        else
+            target = arena->addTypePack(tp->ty);
+
+        LUAU_ASSERT(target);
+        (*packs)[tp] = target;
+        queue.push_back(target);
+        return target;
+    }
+
+    Property shallowClone(const Property& p)
+    {
+        if (FFlag::DebugLuauReadWriteProperties)
+        {
+            std::optional<TypeId> cloneReadTy;
+            if (auto ty = p.readType())
+                cloneReadTy = shallowClone(*ty);
+
+            std::optional<TypeId> cloneWriteTy;
+            if (auto ty = p.writeType())
+                cloneWriteTy = shallowClone(*ty);
+
+            std::optional<Property> cloned = Property::create(cloneReadTy, cloneWriteTy);
+            LUAU_ASSERT(cloned);
+            cloned->deprecated = p.deprecated;
+            cloned->deprecatedSuggestion = p.deprecatedSuggestion;
+            cloned->location = p.location;
+            cloned->tags = p.tags;
+            cloned->documentationSymbol = p.documentationSymbol;
+            return *cloned;
+        }
+        else
+        {
+            return Property{
+                shallowClone(p.type()),
+                p.deprecated,
+                p.deprecatedSuggestion,
+                p.location,
+                p.tags,
+                p.documentationSymbol,
+            };
+        }
+    }
+
+    void cloneChildren(TypeId ty)
+    {
+        return visit(
+            [&](auto&& t) {
+                return cloneChildren(&t);
+            },
+            asMutable(ty)->ty);
+    }
+
+    void cloneChildren(TypePackId tp)
+    {
+        return visit(
+            [&](auto&& t) {
+                return cloneChildren(&t);
+            },
+            asMutable(tp)->ty);
+    }
+
+    void cloneChildren(Kind kind)
+    {
+        if (auto ty = get<TypeId>(kind))
+            return cloneChildren(*ty);
+        else if (auto tp = get<TypePackId>(kind))
+            return cloneChildren(*tp);
+        else
+            LUAU_ASSERT(!"Item holds neither TypeId nor TypePackId when enqueuing its children?");
+    }
+
+    // ErrorType and ErrorTypePack is an alias to this type.
+    void cloneChildren(Unifiable::Error* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(BoundType* t)
+    {
+        t->boundTo = shallowClone(t->boundTo);
+    }
+
+    void cloneChildren(FreeType* t)
+    {
+        // TODO: clone lower and upper bounds.
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(GenericType* t)
+    {
+        // TOOD: clone upper bounds.
+    }
+
+    void cloneChildren(PrimitiveType* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(BlockedType* t)
+    {
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(PendingExpansionType* t)
+    {
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(SingletonType* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(FunctionType* t)
+    {
+        for (TypeId& g : t->generics)
+            g = shallowClone(g);
+
+        for (TypePackId& gp : t->genericPacks)
+            gp = shallowClone(gp);
+
+        t->argTypes = shallowClone(t->argTypes);
+        t->retTypes = shallowClone(t->retTypes);
+    }
+
+    void cloneChildren(TableType* t)
+    {
+        if (t->indexer)
+        {
+            t->indexer->indexType = shallowClone(t->indexer->indexType);
+            t->indexer->indexResultType = shallowClone(t->indexer->indexResultType);
+        }
+
+        for (auto& [_, p] : t->props)
+            p = shallowClone(p);
+
+        for (TypeId& ty : t->instantiatedTypeParams)
+            ty = shallowClone(ty);
+
+        for (TypePackId& tp : t->instantiatedTypePackParams)
+            tp = shallowClone(tp);
+    }
+
+    void cloneChildren(MetatableType* t)
+    {
+        t->table = shallowClone(t->table);
+        t->metatable = shallowClone(t->metatable);
+    }
+
+    void cloneChildren(ClassType* t)
+    {
+        for (auto& [_, p] : t->props)
+            p = shallowClone(p);
+
+        if (t->parent)
+            t->parent = shallowClone(*t->parent);
+
+        if (t->metatable)
+            t->metatable = shallowClone(*t->metatable);
+
+        if (t->indexer)
+        {
+            t->indexer->indexType = shallowClone(t->indexer->indexType);
+            t->indexer->indexResultType = shallowClone(t->indexer->indexResultType);
+        }
+    }
+
+    void cloneChildren(AnyType* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(UnionType* t)
+    {
+        for (TypeId& ty : t->options)
+            ty = shallowClone(ty);
+    }
+
+    void cloneChildren(IntersectionType* t)
+    {
+        for (TypeId& ty : t->parts)
+            ty = shallowClone(ty);
+    }
+
+    void cloneChildren(LazyType* t)
+    {
+        if (auto unwrapped = t->unwrapped.load())
+            t->unwrapped.store(shallowClone(unwrapped));
+    }
+
+    void cloneChildren(UnknownType* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(NeverType* t)
+    {
+        // noop.
+    }
+
+    void cloneChildren(NegationType* t)
+    {
+        t->ty = shallowClone(t->ty);
+    }
+
+    void cloneChildren(TypeFamilyInstanceType* t)
+    {
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(FreeTypePack* t)
+    {
+        // TODO: clone lower and upper bounds.
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(GenericTypePack* t)
+    {
+        // TOOD: clone upper bounds.
+    }
+
+    void cloneChildren(BlockedTypePack* t)
+    {
+        // TODO: In the new solver, we should ice.
+    }
+
+    void cloneChildren(BoundTypePack* t)
+    {
+        t->boundTo = shallowClone(t->boundTo);
+    }
+
+    void cloneChildren(VariadicTypePack* t)
+    {
+        t->ty = shallowClone(t->ty);
+    }
+
+    void cloneChildren(TypePack* t)
+    {
+        for (TypeId& ty : t->head)
+            ty = shallowClone(ty);
+
+        if (t->tail)
+            t->tail = shallowClone(*t->tail);
+    }
+
+    void cloneChildren(TypeFamilyInstanceTypePack* t)
+    {
+        // TODO: In the new solver, we should ice.
+    }
+};
+
+} // namespace
+
+namespace
+{
+
 Property clone(const Property& prop, TypeArena& dest, CloneState& cloneState)
 {
     if (FFlag::DebugLuauReadWriteProperties)
@@ -470,6 +883,13 @@ TypePackId clone(TypePackId tp, TypeArena& dest, CloneState& cloneState)
     if (tp->persistent)
         return tp;
 
+    if (FFlag::LuauStacklessTypeClone)
+    {
+        TypeCloner2 cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+        return cloner.clone(tp);
+    }
+    else
+    {
         RecursionLimiter _ra(&cloneState.recursionCount, FInt::LuauTypeCloneRecursionLimit);
 
         TypePackId& res = cloneState.seenTypePacks[tp];
@@ -482,12 +902,20 @@ TypePackId clone(TypePackId tp, TypeArena& dest, CloneState& cloneState)
 
         return res;
     }
+}
 
 TypeId clone(TypeId typeId, TypeArena& dest, CloneState& cloneState)
 {
     if (typeId->persistent)
         return typeId;
 
+    if (FFlag::LuauStacklessTypeClone)
+    {
+        TypeCloner2 cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+        return cloner.clone(typeId);
+    }
+    else
+    {
         RecursionLimiter _ra(&cloneState.recursionCount, FInt::LuauTypeCloneRecursionLimit);
 
         TypeId& res = cloneState.seenTypes[typeId];
@@ -506,8 +934,37 @@ TypeId clone(TypeId typeId, TypeArena& dest, CloneState& cloneState)
 
         return res;
     }
+}
 
 TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState)
+{
+    if (FFlag::LuauStacklessTypeClone)
+    {
+        TypeCloner2 cloner{NotNull{&dest}, cloneState.builtinTypes, NotNull{&cloneState.seenTypes}, NotNull{&cloneState.seenTypePacks}};
+
+        TypeFun copy = typeFun;
+
+        for (auto& param : copy.typeParams)
+        {
+            param.ty = cloner.clone(param.ty);
+
+            if (param.defaultValue)
+                param.defaultValue = cloner.clone(*param.defaultValue);
+        }
+
+        for (auto& param : copy.typePackParams)
+        {
+            param.tp = cloner.clone(param.tp);
+
+            if (param.defaultValue)
+                param.defaultValue = cloner.clone(*param.defaultValue);
+        }
+
+        copy.type = cloner.clone(copy.type);
+
+        return copy;
+    }
+    else
     {
         TypeFun result;
 
@@ -537,5 +994,6 @@ TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState)
 
         return result;
     }
+}
 
 } // namespace Luau

Analysis/src/Differ.cpp

@@ -107,15 +107,19 @@ std::string DiffPath::toString(bool prependDot) const
     }
     return pathStr;
 }
-std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLeaf& leaf, const DiffPathNodeLeaf& otherLeaf) const
+std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLeaf& leaf, const DiffPathNodeLeaf& otherLeaf, bool multiLine) const
 {
+    std::string conditionalNewline = multiLine ? "\n" : " ";
+    std::string conditionalIndent = multiLine ? "    " : "";
     std::string pathStr{rootName + diffPath.toString(true)};
     switch (kind)
     {
     case DiffError::Kind::Normal:
     {
         checkNonMissingPropertyLeavesHaveNulloptTableProperty();
-        return pathStr + " has type " + Luau::toString(*leaf.ty);
+        return pathStr + conditionalNewline
+            + "has type" + conditionalNewline
+            + conditionalIndent + Luau::toString(*leaf.ty);
     }
     case DiffError::Kind::MissingTableProperty:
     {
@@ -123,13 +127,17 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
         {
             if (!leaf.tableProperty.has_value())
                 throw InternalCompilerError{"leaf.tableProperty is nullopt"};
-            return pathStr + "." + *leaf.tableProperty + " has type " + Luau::toString(*leaf.ty);
+            return pathStr + "." + *leaf.tableProperty + conditionalNewline
+                + "has type" + conditionalNewline
+                + conditionalIndent + Luau::toString(*leaf.ty);
         }
         else if (otherLeaf.ty.has_value())
         {
             if (!otherLeaf.tableProperty.has_value())
                 throw InternalCompilerError{"otherLeaf.tableProperty is nullopt"};
-            return pathStr + " is missing the property " + *otherLeaf.tableProperty;
+            return pathStr + conditionalNewline
+                + "is missing the property" + conditionalNewline
+                + conditionalIndent + *otherLeaf.tableProperty;
         }
         throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
     }
@@ -140,11 +148,15 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
         {
             if (!leaf.unionIndex.has_value())
                 throw InternalCompilerError{"leaf.unionIndex is nullopt"};
-            return pathStr + " is a union containing type " + Luau::toString(*leaf.ty);
+            return pathStr + conditionalNewline
+                + "is a union containing type" + conditionalNewline
+                + conditionalIndent + Luau::toString(*leaf.ty);
         }
         else if (otherLeaf.ty.has_value())
         {
-            return pathStr + " is a union missing type " + Luau::toString(*otherLeaf.ty);
+            return pathStr + conditionalNewline
+                + "is a union missing type" + conditionalNewline
+                + conditionalIndent + Luau::toString(*otherLeaf.ty);
         }
         throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
     }
@@ -157,11 +169,15 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
         {
             if (!leaf.unionIndex.has_value())
                 throw InternalCompilerError{"leaf.unionIndex is nullopt"};
-            return pathStr + " is an intersection containing type " + Luau::toString(*leaf.ty);
+            return pathStr + conditionalNewline
+                + "is an intersection containing type" + conditionalNewline
+                + conditionalIndent + Luau::toString(*leaf.ty);
         }
         else if (otherLeaf.ty.has_value())
         {
-            return pathStr + " is an intersection missing type " + Luau::toString(*otherLeaf.ty);
+            return pathStr + conditionalNewline
+                + "is an intersection missing type" + conditionalNewline
+                + conditionalIndent + Luau::toString(*otherLeaf.ty);
         }
         throw InternalCompilerError{"Both leaf.ty and otherLeaf.ty is nullopt"};
     }
@@ -169,13 +185,15 @@ std::string DiffError::toStringALeaf(std::string rootName, const DiffPathNodeLea
     {
         if (!leaf.minLength.has_value())
             throw InternalCompilerError{"leaf.minLength is nullopt"};
-        return pathStr + " takes " + std::to_string(*leaf.minLength) + (leaf.isVariadic ? " or more" : "") + " arguments";
+        return pathStr + conditionalNewline
+            + "takes " + std::to_string(*leaf.minLength) + (leaf.isVariadic ? " or more" : "") + " arguments";
     }
     case DiffError::Kind::LengthMismatchInFnRets:
     {
         if (!leaf.minLength.has_value())
             throw InternalCompilerError{"leaf.minLength is nullopt"};
-        return pathStr + " returns " + std::to_string(*leaf.minLength) + (leaf.isVariadic ? " or more" : "") + " values";
+        return pathStr + conditionalNewline
+            + "returns " + std::to_string(*leaf.minLength) + (leaf.isVariadic ? " or more" : "") + " values";
     }
     default:
     {
@@ -190,8 +208,11 @@ void DiffError::checkNonMissingPropertyLeavesHaveNulloptTableProperty() const
         throw InternalCompilerError{"Non-MissingProperty DiffError should have nullopt tableProperty in both leaves"};
 }
 
-std::string getDevFixFriendlyName(TypeId ty)
+std::string getDevFixFriendlyName(const std::optional<std::string>& maybeSymbol, TypeId ty)
 {
+    if (maybeSymbol.has_value())
+        return *maybeSymbol;
+
     if (auto table = get<TableType>(ty))
     {
         if (table->name.has_value())
@@ -206,27 +227,39 @@ std::string getDevFixFriendlyName(TypeId ty)
             return *metatable->syntheticName;
         }
     }
-    // else if (auto primitive = get<PrimitiveType>(ty))
-    //{
-    //    return "<unlabeled-symbol>";
-    //}
     return "<unlabeled-symbol>";
 }
 
-std::string DiffError::toString() const
+std::string DifferEnvironment::getDevFixFriendlyNameLeft() const
 {
+    return getDevFixFriendlyName(externalSymbolLeft, rootLeft);
+}
+
+std::string DifferEnvironment::getDevFixFriendlyNameRight() const
+{
+    return getDevFixFriendlyName(externalSymbolRight, rootRight);
+}
+
+std::string DiffError::toString(bool multiLine) const
+{
+    std::string conditionalNewline = multiLine ? "\n" : " ";
+    std::string conditionalIndent = multiLine ? "    " : "";
     switch (kind)
     {
     case DiffError::Kind::IncompatibleGeneric:
     {
         std::string diffPathStr{diffPath.toString(true)};
-        return "DiffError: these two types are not equal because the left generic at " + leftRootName + diffPathStr +
+        return "DiffError: these two types are not equal because the left generic at" + conditionalNewline
-               " cannot be the same type parameter as the right generic at " + rightRootName + diffPathStr;
+                + conditionalIndent + leftRootName + diffPathStr + conditionalNewline
+                + "cannot be the same type parameter as the right generic at" + conditionalNewline
+                + conditionalIndent + rightRootName + diffPathStr;
     }
     default:
     {
-        return "DiffError: these two types are not equal because the left type at " + toStringALeaf(leftRootName, left, right) +
+        return "DiffError: these two types are not equal because the left type at" + conditionalNewline
-               ", while the right type at " + toStringALeaf(rightRootName, right, left);
+                + conditionalIndent + toStringALeaf(leftRootName, left, right, multiLine) + "," + conditionalNewline +
+                "while the right type at" + conditionalNewline
+                + conditionalIndent + toStringALeaf(rightRootName, right, left, multiLine);
     }
     }
 }
@@ -296,8 +329,8 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
                 DiffError::Kind::MissingTableProperty,
                 DiffPathNodeLeaf::detailsTableProperty(value.type(), field),
                 DiffPathNodeLeaf::nullopts(),
-                getDevFixFriendlyName(env.rootLeft),
+                env.getDevFixFriendlyNameLeft(),
-                getDevFixFriendlyName(env.rootRight),
+                env.getDevFixFriendlyNameRight(),
             }};
         }
     }
@@ -307,8 +340,7 @@ static DifferResult diffTable(DifferEnvironment& env, TypeId left, TypeId right)
         {
             // right has a field the left doesn't
             return DifferResult{DiffError{DiffError::Kind::MissingTableProperty, DiffPathNodeLeaf::nullopts(),
-                DiffPathNodeLeaf::detailsTableProperty(value.type(), field), getDevFixFriendlyName(env.rootLeft),
+                DiffPathNodeLeaf::detailsTableProperty(value.type(), field), env.getDevFixFriendlyNameLeft(), env.getDevFixFriendlyNameRight()}};
-                getDevFixFriendlyName(env.rootRight)}};
         }
     }
     // left and right have the same set of keys
@@ -360,8 +392,8 @@ static DifferResult diffPrimitive(DifferEnvironment& env, TypeId left, TypeId ri
             DiffError::Kind::Normal,
             DiffPathNodeLeaf::detailsNormal(left),
             DiffPathNodeLeaf::detailsNormal(right),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
     return DifferResult{};
@@ -380,8 +412,8 @@ static DifferResult diffSingleton(DifferEnvironment& env, TypeId left, TypeId ri
             DiffError::Kind::Normal,
             DiffPathNodeLeaf::detailsNormal(left),
             DiffPathNodeLeaf::detailsNormal(right),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
     return DifferResult{};
@@ -419,8 +451,8 @@ static DifferResult diffGeneric(DifferEnvironment& env, TypeId left, TypeId righ
             DiffError::Kind::IncompatibleGeneric,
             DiffPathNodeLeaf::nullopts(),
             DiffPathNodeLeaf::nullopts(),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
 
@@ -432,8 +464,8 @@ static DifferResult diffGeneric(DifferEnvironment& env, TypeId left, TypeId righ
         DiffError::Kind::IncompatibleGeneric,
         DiffPathNodeLeaf::nullopts(),
         DiffPathNodeLeaf::nullopts(),
-        getDevFixFriendlyName(env.rootLeft),
+        env.getDevFixFriendlyNameLeft(),
-        getDevFixFriendlyName(env.rootRight),
+        env.getDevFixFriendlyNameRight(),
     }};
 }
 
@@ -468,8 +500,8 @@ static DifferResult diffClass(DifferEnvironment& env, TypeId left, TypeId right)
         DiffError::Kind::Normal,
         DiffPathNodeLeaf::detailsNormal(left),
         DiffPathNodeLeaf::detailsNormal(right),
-        getDevFixFriendlyName(env.rootLeft),
+        env.getDevFixFriendlyNameLeft(),
-        getDevFixFriendlyName(env.rootRight),
+        env.getDevFixFriendlyNameRight(),
     }};
 }
 
@@ -521,16 +553,16 @@ static DifferResult diffUnion(DifferEnvironment& env, TypeId left, TypeId right)
                 DiffError::Kind::MissingUnionMember,
                 DiffPathNodeLeaf::detailsUnionIndex(leftUnion->options[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
                 DiffPathNodeLeaf::nullopts(),
-                getDevFixFriendlyName(env.rootLeft),
+                env.getDevFixFriendlyNameLeft(),
-                getDevFixFriendlyName(env.rootRight),
+                env.getDevFixFriendlyNameRight(),
             }};
         else
             return DifferResult{DiffError{
                 DiffError::Kind::MissingUnionMember,
                 DiffPathNodeLeaf::nullopts(),
                 DiffPathNodeLeaf::detailsUnionIndex(rightUnion->options[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
-                getDevFixFriendlyName(env.rootLeft),
+                env.getDevFixFriendlyNameLeft(),
-                getDevFixFriendlyName(env.rootRight),
+                env.getDevFixFriendlyNameRight(),
             }};
     }
 
@@ -554,16 +586,16 @@ static DifferResult diffIntersection(DifferEnvironment& env, TypeId left, TypeId
                 DiffError::Kind::MissingIntersectionMember,
                 DiffPathNodeLeaf::detailsUnionIndex(leftIntersection->parts[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
                 DiffPathNodeLeaf::nullopts(),
-                getDevFixFriendlyName(env.rootLeft),
+                env.getDevFixFriendlyNameLeft(),
-                getDevFixFriendlyName(env.rootRight),
+                env.getDevFixFriendlyNameRight(),
             }};
         else
             return DifferResult{DiffError{
                 DiffError::Kind::MissingIntersectionMember,
                 DiffPathNodeLeaf::nullopts(),
                 DiffPathNodeLeaf::detailsUnionIndex(rightIntersection->parts[*findSeteqCexResult.mismatchIdx], *findSeteqCexResult.mismatchIdx),
-                getDevFixFriendlyName(env.rootLeft),
+                env.getDevFixFriendlyNameLeft(),
-                getDevFixFriendlyName(env.rootRight),
+                env.getDevFixFriendlyNameRight(),
             }};
     }
 
@@ -583,8 +615,8 @@ static DifferResult diffUsingEnv(DifferEnvironment& env, TypeId left, TypeId rig
             DiffError::Kind::Normal,
             DiffPathNodeLeaf::detailsNormal(left),
             DiffPathNodeLeaf::detailsNormal(right),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
 
@@ -753,8 +785,8 @@ static DifferResult diffCanonicalTpShape(DifferEnvironment& env, DiffError::Kind
         possibleNonNormalErrorKind,
         DiffPathNodeLeaf::detailsLength(int(left.first.size()), left.second.has_value()),
         DiffPathNodeLeaf::detailsLength(int(right.first.size()), right.second.has_value()),
-        getDevFixFriendlyName(env.rootLeft),
+        env.getDevFixFriendlyNameLeft(),
-        getDevFixFriendlyName(env.rootRight),
+        env.getDevFixFriendlyNameRight(),
     }};
 }
 
@@ -769,8 +801,8 @@ static DifferResult diffHandleFlattenedTail(DifferEnvironment& env, DiffError::K
             DiffError::Kind::Normal,
             DiffPathNodeLeaf::detailsNormal(env.visitingBegin()->first),
             DiffPathNodeLeaf::detailsNormal(env.visitingBegin()->second),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
 
@@ -847,8 +879,8 @@ static DifferResult diffGenericTp(DifferEnvironment& env, TypePackId left, TypeP
             DiffError::Kind::IncompatibleGeneric,
             DiffPathNodeLeaf::nullopts(),
             DiffPathNodeLeaf::nullopts(),
-            getDevFixFriendlyName(env.rootLeft),
+            env.getDevFixFriendlyNameLeft(),
-            getDevFixFriendlyName(env.rootRight),
+            env.getDevFixFriendlyNameRight(),
         }};
     }
 
@@ -860,8 +892,8 @@ static DifferResult diffGenericTp(DifferEnvironment& env, TypePackId left, TypeP
         DiffError::Kind::IncompatibleGeneric,
         DiffPathNodeLeaf::nullopts(),
         DiffPathNodeLeaf::nullopts(),
-        getDevFixFriendlyName(env.rootLeft),
+        env.getDevFixFriendlyNameLeft(),
-        getDevFixFriendlyName(env.rootRight),
+        env.getDevFixFriendlyNameRight(),
     }};
 }
 
@@ -910,7 +942,13 @@ std::vector<std::pair<TypeId, TypeId>>::const_reverse_iterator DifferEnvironment
 
 DifferResult diff(TypeId ty1, TypeId ty2)
 {
-    DifferEnvironment differEnv{ty1, ty2};
+    DifferEnvironment differEnv{ty1, ty2, std::nullopt, std::nullopt};
+    return diffUsingEnv(differEnv, ty1, ty2);
+}
+
+DifferResult diffWithSymbols(TypeId ty1, TypeId ty2, std::optional<std::string> symbol1, std::optional<std::string> symbol2)
+{
+    DifferEnvironment differEnv{ty1, ty2, symbol1, symbol2};
     return diffUsingEnv(differEnv, ty1, ty2);
 }
 

Analysis/src/Error.cpp

@@ -4,12 +4,16 @@
 #include "Luau/Clone.h"
 #include "Luau/Common.h"
 #include "Luau/FileResolver.h"
+#include "Luau/NotNull.h"
 #include "Luau/StringUtils.h"
 #include "Luau/ToString.h"
 
+#include <optional>
 #include <stdexcept>
 #include <type_traits>
 
+LUAU_FASTFLAGVARIABLE(LuauIndentTypeMismatch, false)
+LUAU_FASTINTVARIABLE(LuauIndentTypeMismatchMaxTypeLength, 10)
 
 static std::string wrongNumberOfArgsString(
     size_t expectedCount, std::optional<size_t> maximumCount, size_t actualCount, const char* argPrefix = nullptr, bool isVariadic = false)
@@ -66,6 +70,20 @@ struct ErrorConverter
 
         std::string result;
 
+        auto quote = [&](std::string s) {
+            return "'" + s + "'";
+        };
+
+        auto constructErrorMessage = [&](std::string givenType, std::string wantedType, std::optional<std::string> givenModule,
+                                         std::optional<std::string> wantedModule) -> std::string {
+            std::string given = givenModule ? quote(givenType) + " from " + quote(*givenModule) : quote(givenType);
+            std::string wanted = wantedModule ? quote(wantedType) + " from " + quote(*wantedModule) : quote(wantedType);
+            size_t luauIndentTypeMismatchMaxTypeLength = size_t(FInt::LuauIndentTypeMismatchMaxTypeLength);
+            if (givenType.length() <= luauIndentTypeMismatchMaxTypeLength || wantedType.length() <= luauIndentTypeMismatchMaxTypeLength)
+                return "Type " + given + " could not be converted into " + wanted;
+            return "Type\n    " + given + "\ncould not be converted into\n    " + wanted;
+        };
+
         if (givenTypeName == wantedTypeName)
         {
             if (auto givenDefinitionModule = getDefinitionModuleName(tm.givenType))
@@ -76,20 +94,31 @@ struct ErrorConverter
                     {
                         std::string givenModuleName = fileResolver->getHumanReadableModuleName(*givenDefinitionModule);
                         std::string wantedModuleName = fileResolver->getHumanReadableModuleName(*wantedDefinitionModule);
+                        if (FFlag::LuauIndentTypeMismatch)
+                            result = constructErrorMessage(givenTypeName, wantedTypeName, givenModuleName, wantedModuleName);
+                        else
                             result = "Type '" + givenTypeName + "' from '" + givenModuleName + "' could not be converted into '" + wantedTypeName +
                                      "' from '" + wantedModuleName + "'";
                     }
                     else
                     {
-                        result = "Type '" + givenTypeName + "' from '" + *givenDefinitionModule + "' could not be converted into '" + wantedTypeName +
+                        if (FFlag::LuauIndentTypeMismatch)
-                                 "' from '" + *wantedDefinitionModule + "'";
+                            result = constructErrorMessage(givenTypeName, wantedTypeName, *givenDefinitionModule, *wantedDefinitionModule);
+                        else
+                            result = "Type '" + givenTypeName + "' from '" + *givenDefinitionModule + "' could not be converted into '" +
+                                     wantedTypeName + "' from '" + *wantedDefinitionModule + "'";
                     }
                 }
             }
         }
 
         if (result.empty())
+        {
+            if (FFlag::LuauIndentTypeMismatch)
+                result = constructErrorMessage(givenTypeName, wantedTypeName, std::nullopt, std::nullopt);
+            else
                 result = "Type '" + givenTypeName + "' could not be converted into '" + wantedTypeName + "'";
+        }
 
 
         if (tm.error)
@@ -97,7 +126,7 @@ struct ErrorConverter
             result += "\ncaused by:\n  ";
 
             if (!tm.reason.empty())
-                result += tm.reason + " ";
+                result += tm.reason + (FFlag::LuauIndentTypeMismatch ? " \n" : " ");
 
             result += Luau::toString(*tm.error, TypeErrorToStringOptions{fileResolver});
         }
@@ -845,7 +874,7 @@ bool containsParseErrorName(const TypeError& error)
 }
 
 template<typename T>
-void copyError(T& e, TypeArena& destArena, CloneState cloneState)
+void copyError(T& e, TypeArena& destArena, CloneState& cloneState)
 {
     auto clone = [&](auto&& ty) {
         return ::Luau::clone(ty, destArena, cloneState);
@@ -998,9 +1027,9 @@ void copyError(T& e, TypeArena& destArena, CloneState cloneState)
         static_assert(always_false_v<T>, "Non-exhaustive type switch");
 }
 
-void copyErrors(ErrorVec& errors, TypeArena& destArena)
+void copyErrors(ErrorVec& errors, TypeArena& destArena, NotNull<BuiltinTypes> builtinTypes)
 {
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     auto visitErrorData = [&](auto&& e) {
         copyError(e, destArena, cloneState);

Analysis/src/Frontend.cpp

@@ -35,7 +35,6 @@ LUAU_FASTINTVARIABLE(LuauAutocompleteCheckTimeoutMs, 100)
 LUAU_FASTFLAGVARIABLE(DebugLuauDeferredConstraintResolution, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJson, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauReadWriteProperties, false)
-LUAU_FASTFLAGVARIABLE(LuauTypecheckCancellation, false)
 
 namespace Luau
 {
@@ -126,7 +125,7 @@ static ParseResult parseSourceForModule(std::string_view source, Luau::SourceMod
 
 static void persistCheckedTypes(ModulePtr checkedModule, GlobalTypes& globals, ScopePtr targetScope, const std::string& packageName)
 {
-    CloneState cloneState;
+    CloneState cloneState{globals.builtinTypes};
 
     std::vector<TypeId> typesToPersist;
     typesToPersist.reserve(checkedModule->declaredGlobals.size() + checkedModule->exportedTypeBindings.size());
@@ -462,7 +461,7 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
             checkResult.timeoutHits.push_back(item.name);
 
         // If check was manually cancelled, do not return partial results
-        if (FFlag::LuauTypecheckCancellation && item.module->cancelled)
+        if (item.module->cancelled)
             return {};
 
         checkResult.errors.insert(checkResult.errors.end(), item.module->errors.begin(), item.module->errors.end());
@@ -635,7 +634,7 @@ std::vector<ModuleName> Frontend::checkQueuedModules(std::optional<FrontendOptio
                 if (item.exception)
                     itemWithException = i;
 
-                if (FFlag::LuauTypecheckCancellation && item.module && item.module->cancelled)
+                if (item.module && item.module->cancelled)
                     cancelled = true;
 
                 if (itemWithException || cancelled)
@@ -677,7 +676,7 @@ std::vector<ModuleName> Frontend::checkQueuedModules(std::optional<FrontendOptio
         if (remaining != 0 && processing == 0)
         {
             // Typechecking might have been cancelled by user, don't return partial results
-            if (FFlag::LuauTypecheckCancellation && cancelled)
+            if (cancelled)
                 return {};
 
             // We might have stopped because of a pending exception
@@ -910,7 +909,6 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
         else
             typeCheckLimits.unifierIterationLimit = std::nullopt;
 
-        if (FFlag::LuauTypecheckCancellation)
         typeCheckLimits.cancellationToken = item.options.cancellationToken;
 
         ModulePtr moduleForAutocomplete = check(sourceModule, Mode::Strict, requireCycles, environmentScope, /*forAutocomplete*/ true,
@@ -932,7 +930,6 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
 
     TypeCheckLimits typeCheckLimits;
 
-    if (FFlag::LuauTypecheckCancellation)
     typeCheckLimits.cancellationToken = item.options.cancellationToken;
 
     ModulePtr module = check(sourceModule, mode, requireCycles, environmentScope, /*forAutocomplete*/ false, item.recordJsonLog, typeCheckLimits);
@@ -969,7 +966,7 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
         // copyErrors needs to allocate into interfaceTypes as it copies
         // types out of internalTypes, so we unfreeze it here.
         unfreeze(module->interfaceTypes);
-        copyErrors(module->errors, module->interfaceTypes);
+        copyErrors(module->errors, module->interfaceTypes, builtinTypes);
         freeze(module->interfaceTypes);
 
         module->internalTypes.clear();
@@ -1014,7 +1011,7 @@ void Frontend::checkBuildQueueItems(std::vector<BuildQueueItem>& items)
     {
         checkBuildQueueItem(item);
 
-        if (FFlag::LuauTypecheckCancellation && item.module && item.module->cancelled)
+        if (item.module && item.module->cancelled)
             break;
 
         recordItemResult(item);
@@ -1295,8 +1292,6 @@ ModulePtr Frontend::check(const SourceModule& sourceModule, Mode mode, std::vect
         typeChecker.finishTime = typeCheckLimits.finishTime;
         typeChecker.instantiationChildLimit = typeCheckLimits.instantiationChildLimit;
         typeChecker.unifierIterationLimit = typeCheckLimits.unifierIterationLimit;
-
-        if (FFlag::LuauTypecheckCancellation)
         typeChecker.cancellationToken = typeCheckLimits.cancellationToken;
 
         return typeChecker.check(sourceModule, mode, environmentScope);

Analysis/src/Linter.cpp

@@ -14,48 +14,9 @@
 
 LUAU_FASTINTVARIABLE(LuauSuggestionDistance, 4)
 
-LUAU_FASTFLAGVARIABLE(LuauLintNativeComment, false)
-
 namespace Luau
 {
 
-// clang-format off
-static const char* kWarningNames[] = {
-    "Unknown",
-
-    "UnknownGlobal",
-    "DeprecatedGlobal",
-    "GlobalUsedAsLocal",
-    "LocalShadow",
-    "SameLineStatement",
-    "MultiLineStatement",
-    "LocalUnused",
-    "FunctionUnused",
-    "ImportUnused",
-    "BuiltinGlobalWrite",
-    "PlaceholderRead",
-    "UnreachableCode",
-    "UnknownType",
-    "ForRange",
-    "UnbalancedAssignment",
-    "ImplicitReturn",
-    "DuplicateLocal",
-    "FormatString",
-    "TableLiteral",
-    "UninitializedLocal",
-    "DuplicateFunction",
-    "DeprecatedApi",
-    "TableOperations",
-    "DuplicateCondition",
-    "MisleadingAndOr",
-    "CommentDirective",
-    "IntegerParsing",
-    "ComparisonPrecedence",
-};
-// clang-format on
-
-static_assert(std::size(kWarningNames) == unsigned(LintWarning::Code__Count), "did you forget to add warning to the list?");
-
 struct LintContext
 {
     struct Global
@@ -2827,7 +2788,7 @@ static void lintComments(LintContext& context, const std::vector<HotComment>& ho
                             "optimize directive uses unknown optimization level '%s', 0..2 expected", level);
                 }
             }
-            else if (FFlag::LuauLintNativeComment && first == "native")
+            else if (first == "native")
             {
                 if (space != std::string::npos)
                     emitWarning(context, LintWarning::Code_CommentDirective, hc.location,
@@ -2855,12 +2816,6 @@ static void lintComments(LintContext& context, const std::vector<HotComment>& ho
     }
 }
 
-void LintOptions::setDefaults()
-{
-    // By default, we enable all warnings
-    warningMask = ~0ull;
-}
-
 std::vector<LintWarning> lint(AstStat* root, const AstNameTable& names, const ScopePtr& env, const Module* module,
     const std::vector<HotComment>& hotcomments, const LintOptions& options)
 {
@@ -2952,54 +2907,6 @@ std::vector<LintWarning> lint(AstStat* root, const AstNameTable& names, const Sc
     return context.result;
 }
 
-const char* LintWarning::getName(Code code)
-{
-    LUAU_ASSERT(unsigned(code) < Code__Count);
-
-    return kWarningNames[code];
-}
-
-LintWarning::Code LintWarning::parseName(const char* name)
-{
-    for (int code = Code_Unknown; code < Code__Count; ++code)
-        if (strcmp(name, getName(Code(code))) == 0)
-            return Code(code);
-
-    return Code_Unknown;
-}
-
-uint64_t LintWarning::parseMask(const std::vector<HotComment>& hotcomments)
-{
-    uint64_t result = 0;
-
-    for (const HotComment& hc : hotcomments)
-    {
-        if (!hc.header)
-            continue;
-
-        if (hc.content.compare(0, 6, "nolint") != 0)
-            continue;
-
-        size_t name = hc.content.find_first_not_of(" \t", 6);
-
-        // --!nolint disables everything
-        if (name == std::string::npos)
-            return ~0ull;
-
-        // --!nolint needs to be followed by a whitespace character
-        if (name == 6)
-            continue;
-
-        // --!nolint name disables the specific lint
-        LintWarning::Code code = LintWarning::parseName(hc.content.c_str() + name);
-
-        if (code != LintWarning::Code_Unknown)
-            result |= 1ull << int(code);
-    }
-
-    return result;
-}
-
 std::vector<AstName> getDeprecatedGlobals(const AstNameTable& names)
 {
     LintContext context;

Analysis/src/LinterConfig.cpp

@@ -0,0 +1,63 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/LinterConfig.h"
+
+#include "Luau/ParseResult.h"
+
+namespace Luau
+{
+
+void LintOptions::setDefaults()
+{
+    // By default, we enable all warnings
+    warningMask = ~0ull;
+}
+
+const char* LintWarning::getName(Code code)
+{
+    LUAU_ASSERT(unsigned(code) < Code__Count);
+
+    return kWarningNames[code];
+}
+
+LintWarning::Code LintWarning::parseName(const char* name)
+{
+    for (int code = Code_Unknown; code < Code__Count; ++code)
+        if (strcmp(name, getName(Code(code))) == 0)
+            return Code(code);
+
+    return Code_Unknown;
+}
+
+uint64_t LintWarning::parseMask(const std::vector<HotComment>& hotcomments)
+{
+    uint64_t result = 0;
+
+    for (const HotComment& hc : hotcomments)
+    {
+        if (!hc.header)
+            continue;
+
+        if (hc.content.compare(0, 6, "nolint") != 0)
+            continue;
+
+        size_t name = hc.content.find_first_not_of(" \t", 6);
+
+        // --!nolint disables everything
+        if (name == std::string::npos)
+            return ~0ull;
+
+        // --!nolint needs to be followed by a whitespace character
+        if (name == 6)
+            continue;
+
+        // --!nolint name disables the specific lint
+        LintWarning::Code code = LintWarning::parseName(hc.content.c_str() + name);
+
+        if (code != LintWarning::Code_Unknown)
+            result |= 1ull << int(code);
+    }
+
+    return result;
+}
+
+} // namespace Luau

Analysis/src/Module.cpp

@@ -199,7 +199,7 @@ void Module::clonePublicInterface(NotNull<BuiltinTypes> builtinTypes, InternalEr
     LUAU_ASSERT(interfaceTypes.types.empty());
     LUAU_ASSERT(interfaceTypes.typePacks.empty());
 
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     ScopePtr moduleScope = getModuleScope();
 

Analysis/src/Substitution.cpp

@@ -10,7 +10,6 @@
 
 LUAU_FASTINTVARIABLE(LuauTarjanChildLimit, 10000)
 LUAU_FASTFLAG(DebugLuauReadWriteProperties)
-LUAU_FASTFLAGVARIABLE(LuauTarjanSingleArr, false)
 
 namespace Luau
 {
@@ -269,8 +268,6 @@ std::pair<int, bool> Tarjan::indexify(TypeId ty)
 {
     ty = log->follow(ty);
 
-    if (FFlag::LuauTarjanSingleArr)
-    {
     auto [index, fresh] = typeToIndex.try_insert(ty, false);
 
     if (fresh)
@@ -281,29 +278,11 @@ std::pair<int, bool> Tarjan::indexify(TypeId ty)
 
     return {index, fresh};
 }
-    else
-    {
-        bool fresh = !typeToIndex.contains(ty);
-        int& index = typeToIndex[ty];
-
-        if (fresh)
-        {
-            index = int(indexToType.size());
-            indexToType.push_back(ty);
-            indexToPack.push_back(nullptr);
-            onStack.push_back(false);
-            lowlink.push_back(index);
-        }
-        return {index, fresh};
-    }
-}
 
 std::pair<int, bool> Tarjan::indexify(TypePackId tp)
 {
     tp = log->follow(tp);
 
-    if (FFlag::LuauTarjanSingleArr)
-    {
     auto [index, fresh] = packToIndex.try_insert(tp, false);
 
     if (fresh)
@@ -314,23 +293,6 @@ std::pair<int, bool> Tarjan::indexify(TypePackId tp)
 
     return {index, fresh};
 }
-    else
-    {
-
-        bool fresh = !packToIndex.contains(tp);
-        int& index = packToIndex[tp];
-
-        if (fresh)
-        {
-            index = int(indexToPack.size());
-            indexToType.push_back(nullptr);
-            indexToPack.push_back(tp);
-            onStack.push_back(false);
-            lowlink.push_back(index);
-        }
-        return {index, fresh};
-    }
-}
 
 void Tarjan::visitChild(TypeId ty)
 {
@@ -350,9 +312,6 @@ void Tarjan::visitChild(TypePackId tp)
 
 TarjanResult Tarjan::loop()
 {
-    if (!FFlag::LuauTarjanSingleArr)
-        return loop_DEPRECATED();
-
     // Normally Tarjan is presented recursively, but this is a hot loop, so worth optimizing
     while (!worklist.empty())
     {
@@ -475,28 +434,12 @@ TarjanResult Tarjan::visitRoot(TypePackId tp)
 }
 
 void Tarjan::clearTarjan()
-{
-    if (FFlag::LuauTarjanSingleArr)
 {
     typeToIndex.clear();
     packToIndex.clear();
     nodes.clear();
 
     stack.clear();
-    }
-    else
-    {
-        dirty.clear();
-
-        typeToIndex.clear();
-        packToIndex.clear();
-        indexToType.clear();
-        indexToPack.clear();
-
-        stack.clear();
-        onStack.clear();
-        lowlink.clear();
-    }
 
     edgesTy.clear();
     edgesTp.clear();
@@ -504,34 +447,16 @@ void Tarjan::clearTarjan()
 }
 
 bool Tarjan::getDirty(int index)
-{
-    if (FFlag::LuauTarjanSingleArr)
 {
     LUAU_ASSERT(size_t(index) < nodes.size());
     return nodes[index].dirty;
 }
-    else
-    {
-        if (dirty.size() <= size_t(index))
-            dirty.resize(index + 1, false);
-        return dirty[index];
-    }
-}
 
 void Tarjan::setDirty(int index, bool d)
-{
-    if (FFlag::LuauTarjanSingleArr)
 {
     LUAU_ASSERT(size_t(index) < nodes.size());
     nodes[index].dirty = d;
 }
-    else
-    {
-        if (dirty.size() <= size_t(index))
-            dirty.resize(index + 1, false);
-        dirty[index] = d;
-    }
-}
 
 void Tarjan::visitEdge(int index, int parentIndex)
 {
@@ -541,9 +466,6 @@ void Tarjan::visitEdge(int index, int parentIndex)
 
 void Tarjan::visitSCC(int index)
 {
-    if (!FFlag::LuauTarjanSingleArr)
-        return visitSCC_DEPRECATED(index);
-
     bool d = getDirty(index);
 
     for (auto it = stack.rbegin(); !d && it != stack.rend(); it++)
@@ -588,132 +510,6 @@ TarjanResult Tarjan::findDirty(TypePackId tp)
     return visitRoot(tp);
 }
 
-TarjanResult Tarjan::loop_DEPRECATED()
-{
-    // Normally Tarjan is presented recursively, but this is a hot loop, so worth optimizing
-    while (!worklist.empty())
-    {
-        auto [index, currEdge, lastEdge] = worklist.back();
-
-        // First visit
-        if (currEdge == -1)
-        {
-            ++childCount;
-            if (childLimit > 0 && childLimit <= childCount)
-                return TarjanResult::TooManyChildren;
-
-            stack.push_back(index);
-            onStack[index] = true;
-
-            currEdge = int(edgesTy.size());
-
-            // Fill in edge list of this vertex
-            if (TypeId ty = indexToType[index])
-                visitChildren(ty, index);
-            else if (TypePackId tp = indexToPack[index])
-                visitChildren(tp, index);
-
-            lastEdge = int(edgesTy.size());
-        }
-
-        // Visit children
-        bool foundFresh = false;
-
-        for (; currEdge < lastEdge; currEdge++)
-        {
-            int childIndex = -1;
-            bool fresh = false;
-
-            if (auto ty = edgesTy[currEdge])
-                std::tie(childIndex, fresh) = indexify(ty);
-            else if (auto tp = edgesTp[currEdge])
-                std::tie(childIndex, fresh) = indexify(tp);
-            else
-                LUAU_ASSERT(false);
-
-            if (fresh)
-            {
-                // Original recursion point, update the parent continuation point and start the new element
-                worklist.back() = {index, currEdge + 1, lastEdge};
-                worklist.push_back({childIndex, -1, -1});
-
-                // We need to continue the top-level loop from the start with the new worklist element
-                foundFresh = true;
-                break;
-            }
-            else if (onStack[childIndex])
-            {
-                lowlink[index] = std::min(lowlink[index], childIndex);
-            }
-
-            visitEdge(childIndex, index);
-        }
-
-        if (foundFresh)
-            continue;
-
-        if (lowlink[index] == index)
-        {
-            visitSCC(index);
-            while (!stack.empty())
-            {
-                int popped = stack.back();
-                stack.pop_back();
-                onStack[popped] = false;
-                if (popped == index)
-                    break;
-            }
-        }
-
-        worklist.pop_back();
-
-        // Original return from recursion into a child
-        if (!worklist.empty())
-        {
-            auto [parentIndex, _, parentEndEdge] = worklist.back();
-
-            // No need to keep child edges around
-            edgesTy.resize(parentEndEdge);
-            edgesTp.resize(parentEndEdge);
-
-            lowlink[parentIndex] = std::min(lowlink[parentIndex], lowlink[index]);
-            visitEdge(index, parentIndex);
-        }
-    }
-
-    return TarjanResult::Ok;
-}
-
-
-void Tarjan::visitSCC_DEPRECATED(int index)
-{
-    bool d = getDirty(index);
-
-    for (auto it = stack.rbegin(); !d && it != stack.rend(); it++)
-    {
-        if (TypeId ty = indexToType[*it])
-            d = isDirty(ty);
-        else if (TypePackId tp = indexToPack[*it])
-            d = isDirty(tp);
-        if (*it == index)
-            break;
-    }
-
-    if (!d)
-        return;
-
-    for (auto it = stack.rbegin(); it != stack.rend(); it++)
-    {
-        setDirty(*it, true);
-        if (TypeId ty = indexToType[*it])
-            foundDirty(ty);
-        else if (TypePackId tp = indexToPack[*it])
-            foundDirty(tp);
-        if (*it == index)
-            return;
-    }
-}
-
 std::optional<TypeId> Substitution::substitute(TypeId ty)
 {
     ty = log->follow(ty);

Analysis/src/TypeChecker2.cpp

@@ -2688,7 +2688,7 @@ void check(
     typeChecker.visit(sourceModule.root);
 
     unfreeze(module->interfaceTypes);
-    copyErrors(module->errors, module->interfaceTypes);
+    copyErrors(module->errors, module->interfaceTypes, builtinTypes);
     freeze(module->interfaceTypes);
 }
 

Analysis/src/TypeInfer.cpp

@@ -38,11 +38,9 @@ LUAU_FASTFLAG(LuauInstantiateInSubtyping)
 LUAU_FASTFLAGVARIABLE(LuauAllowIndexClassParameters, false)
 LUAU_FASTFLAGVARIABLE(LuauFixCyclicModuleExports, false)
 LUAU_FASTFLAG(LuauOccursIsntAlwaysFailure)
-LUAU_FASTFLAGVARIABLE(LuauTypecheckTypeguards, false)
 LUAU_FASTFLAGVARIABLE(LuauTinyControlFlowAnalysis, false)
 LUAU_FASTFLAGVARIABLE(LuauAlwaysCommitInferencesOfFunctionCalls, false)
 LUAU_FASTFLAG(LuauParseDeclareClassIndexer)
-LUAU_FASTFLAGVARIABLE(LuauIndexTableIntersectionStringExpr, false)
 
 namespace Luau
 {
@@ -3110,22 +3108,13 @@ WithPredicate<TypeId> TypeChecker::checkExpr(const ScopePtr& scope, const AstExp
     }
     else if (expr.op == AstExprBinary::CompareEq || expr.op == AstExprBinary::CompareNe)
     {
-        if (!FFlag::LuauTypecheckTypeguards)
-        {
-            if (auto predicate = tryGetTypeGuardPredicate(expr))
-                return {booleanType, {std::move(*predicate)}};
-        }
-
         // For these, passing expectedType is worse than simply forcing them, because their implementation
         // may inadvertently check if expectedTypes exist first and use it, instead of forceSingleton first.
         WithPredicate<TypeId> lhs = checkExpr(scope, *expr.left, std::nullopt, /*forceSingleton=*/true);
         WithPredicate<TypeId> rhs = checkExpr(scope, *expr.right, std::nullopt, /*forceSingleton=*/true);
 
-        if (FFlag::LuauTypecheckTypeguards)
-        {
         if (auto predicate = tryGetTypeGuardPredicate(expr))
             return {booleanType, {std::move(*predicate)}};
-        }
 
         PredicateVec predicates;
 
@@ -3405,7 +3394,7 @@ TypeId TypeChecker::checkLValueBinding(const ScopePtr& scope, const AstExprIndex
             reportError(TypeError{expr.location, UnknownProperty{exprType, value->value.data}});
             return errorRecoveryType(scope);
         }
-        else if (FFlag::LuauIndexTableIntersectionStringExpr && get<IntersectionType>(exprType))
+        else if (get<IntersectionType>(exprType))
         {
             Name name = std::string(value->value.data, value->value.size);
 

CodeGen/include/Luau/CodeAllocator.h

@@ -1,6 +1,8 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/CodeGen.h"
+
 #include <vector>
 
 #include <stddef.h>
@@ -16,6 +18,7 @@ constexpr uint32_t kCodeAlignment = 32;
 struct CodeAllocator
 {
     CodeAllocator(size_t blockSize, size_t maxTotalSize);
+    CodeAllocator(size_t blockSize, size_t maxTotalSize, AllocationCallback* allocationCallback, void* allocationCallbackContext);
     ~CodeAllocator();
 
     // Places data and code into the executable page area
@@ -24,7 +27,7 @@ struct CodeAllocator
     bool allocate(
         const uint8_t* data, size_t dataSize, const uint8_t* code, size_t codeSize, uint8_t*& result, size_t& resultSize, uint8_t*& resultCodeStart);
 
-    // Provided to callbacks
+    // Provided to unwind info callbacks
     void* context = nullptr;
 
     // Called when new block is created to create and setup the unwinding information for all the code in the block
@@ -34,12 +37,16 @@ struct CodeAllocator
     // Called to destroy unwinding information returned by 'createBlockUnwindInfo'
     void (*destroyBlockUnwindInfo)(void* context, void* unwindData) = nullptr;
 
+private:
     // Unwind information can be placed inside the block with some implementation-specific reservations at the beginning
     // But to simplify block space checks, we limit the max size of all that data
     static const size_t kMaxReservedDataSize = 256;
 
     bool allocateNewBlock(size_t& unwindInfoSize);
 
+    uint8_t* allocatePages(size_t size) const;
+    void freePages(uint8_t* mem, size_t size) const;
+
     // Current block we use for allocations
     uint8_t* blockPos = nullptr;
     uint8_t* blockEnd = nullptr;
@@ -50,6 +57,9 @@ struct CodeAllocator
 
     size_t blockSize = 0;
     size_t maxTotalSize = 0;
+
+    AllocationCallback* allocationCallback = nullptr;
+    void* allocationCallbackContext = nullptr;
 };
 
 } // namespace CodeGen

CodeGen/include/Luau/CodeGen.h

@@ -18,12 +18,25 @@ enum CodeGenFlags
     CodeGen_OnlyNativeModules = 1 << 0,
 };
 
+struct CompilationStats
+{
+    size_t bytecodeSizeBytes = 0;
+    size_t nativeCodeSizeBytes = 0;
+    size_t nativeDataSizeBytes = 0;
+    size_t nativeMetadataSizeBytes = 0;
+
+    uint32_t functionsCompiled = 0;
+};
+
+using AllocationCallback = void(void* context, void* oldPointer, size_t oldSize, void* newPointer, size_t newSize);
+
 bool isSupported();
 
+void create(lua_State* L, AllocationCallback* allocationCallback, void* allocationCallbackContext);
 void create(lua_State* L);
 
 // Builds target function and all inner functions
-void compile(lua_State* L, int idx, unsigned int flags = 0);
+void compile(lua_State* L, int idx, unsigned int flags = 0, CompilationStats* stats = nullptr);
 
 using AnnotatorFn = void (*)(void* context, std::string& result, int fid, int instpos);
 

CodeGen/include/Luau/ConditionX64.h

@@ -1,6 +1,8 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include "Luau/Common.h"
+
 namespace Luau
 {
 namespace CodeGen
@@ -43,5 +45,68 @@ enum class ConditionX64 : uint8_t
     Count
 };
 
+inline ConditionX64 getReverseCondition(ConditionX64 cond)
+{
+    switch (cond)
+    {
+    case ConditionX64::Overflow:
+        return ConditionX64::NoOverflow;
+    case ConditionX64::NoOverflow:
+        return ConditionX64::Overflow;
+    case ConditionX64::Carry:
+        return ConditionX64::NoCarry;
+    case ConditionX64::NoCarry:
+        return ConditionX64::Carry;
+    case ConditionX64::Below:
+        return ConditionX64::NotBelow;
+    case ConditionX64::BelowEqual:
+        return ConditionX64::NotBelowEqual;
+    case ConditionX64::Above:
+        return ConditionX64::NotAbove;
+    case ConditionX64::AboveEqual:
+        return ConditionX64::NotAboveEqual;
+    case ConditionX64::Equal:
+        return ConditionX64::NotEqual;
+    case ConditionX64::Less:
+        return ConditionX64::NotLess;
+    case ConditionX64::LessEqual:
+        return ConditionX64::NotLessEqual;
+    case ConditionX64::Greater:
+        return ConditionX64::NotGreater;
+    case ConditionX64::GreaterEqual:
+        return ConditionX64::NotGreaterEqual;
+    case ConditionX64::NotBelow:
+        return ConditionX64::Below;
+    case ConditionX64::NotBelowEqual:
+        return ConditionX64::BelowEqual;
+    case ConditionX64::NotAbove:
+        return ConditionX64::Above;
+    case ConditionX64::NotAboveEqual:
+        return ConditionX64::AboveEqual;
+    case ConditionX64::NotEqual:
+        return ConditionX64::Equal;
+    case ConditionX64::NotLess:
+        return ConditionX64::Less;
+    case ConditionX64::NotLessEqual:
+        return ConditionX64::LessEqual;
+    case ConditionX64::NotGreater:
+        return ConditionX64::Greater;
+    case ConditionX64::NotGreaterEqual:
+        return ConditionX64::GreaterEqual;
+    case ConditionX64::Zero:
+        return ConditionX64::NotZero;
+    case ConditionX64::NotZero:
+        return ConditionX64::Zero;
+    case ConditionX64::Parity:
+        return ConditionX64::NotParity;
+    case ConditionX64::NotParity:
+        return ConditionX64::Parity;
+    case ConditionX64::Count:
+        LUAU_ASSERT(!"invalid ConditionX64 value");
+    }
+
+    return ConditionX64::Count;
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/include/Luau/IrData.h

@@ -176,7 +176,7 @@ enum class IrCmd : uint8_t
     CMP_ANY,
 
     // Unconditional jump
-    // A: block/vmexit
+    // A: block/vmexit/undef
     JUMP,
 
     // Jump if TValue is truthy
@@ -369,10 +369,8 @@ enum class IrCmd : uint8_t
     // Guard against tag mismatch
     // A, B: tag
     // C: block/vmexit/undef
-    // D: bool (finish execution in VM on failure)
     // In final x64 lowering, A can also be Rn
-    // When undef is specified instead of a block, execution is aborted on check failure; if D is true, execution is continued in VM interpreter
+    // When undef is specified instead of a block, execution is aborted on check failure
-    // instead.
     CHECK_TAG,
 
     // Guard against a falsy tag+value
@@ -689,6 +687,10 @@ enum class IrOpKind : uint32_t
     VmExit,
 };
 
+// VmExit uses a special value to indicate that pcpos update should be skipped
+// This is only used during type checking at function entry
+constexpr uint32_t kVmExitEntryGuardPc = (1u << 28) - 1;
+
 struct IrOp
 {
     IrOpKind kind : 4;
@@ -851,6 +853,8 @@ struct IrFunction
     std::vector<IrConst> constants;
 
     std::vector<BytecodeMapping> bcMapping;
+    uint32_t entryBlock = 0;
+    uint32_t entryLocation = 0;
 
     // For each instruction, an operand that can be used to recompute the value
     std::vector<IrOp> valueRestoreOps;
@@ -1037,5 +1041,11 @@ inline int vmUpvalueOp(IrOp op)
     return op.index;
 }
 
+inline uint32_t vmExitOp(IrOp op)
+{
+    LUAU_ASSERT(op.kind == IrOpKind::VmExit);
+    return op.index;
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/AssemblyBuilderA64.cpp

@@ -5,6 +5,7 @@
 #include "ByteUtils.h"
 
 #include <stdarg.h>
+#include <stdio.h>
 
 namespace Luau
 {

CodeGen/src/AssemblyBuilderX64.cpp

@@ -5,7 +5,6 @@
 
 #include <stdarg.h>
 #include <stdio.h>
-#include <string.h>
 
 namespace Luau
 {

CodeGen/src/CodeAllocator.cpp

@@ -33,13 +33,17 @@ static size_t alignToPageSize(size_t size)
 }
 
 #if defined(_WIN32)
-static uint8_t* allocatePages(size_t size)
+static uint8_t* allocatePagesImpl(size_t size)
 {
-    return (uint8_t*)VirtualAlloc(nullptr, alignToPageSize(size), MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+    LUAU_ASSERT(size == alignToPageSize(size));
+
+    return (uint8_t*)VirtualAlloc(nullptr, size, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
 }
 
-static void freePages(uint8_t* mem, size_t size)
+static void freePagesImpl(uint8_t* mem, size_t size)
 {
+    LUAU_ASSERT(size == alignToPageSize(size));
+
     if (VirtualFree(mem, 0, MEM_RELEASE) == 0)
         LUAU_ASSERT(!"failed to deallocate block memory");
 }
@@ -62,14 +66,22 @@ static void flushInstructionCache(uint8_t* mem, size_t size)
 #endif
 }
 #else
-static uint8_t* allocatePages(size_t size)
+static uint8_t* allocatePagesImpl(size_t size)
 {
-    return (uint8_t*)mmap(nullptr, alignToPageSize(size), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+    LUAU_ASSERT(size == alignToPageSize(size));
+
+#ifdef __APPLE__
+    return (uint8_t*)mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON | MAP_JIT, -1, 0);
+#else
+    return (uint8_t*)mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+#endif
 }
 
-static void freePages(uint8_t* mem, size_t size)
+static void freePagesImpl(uint8_t* mem, size_t size)
 {
-    if (munmap(mem, alignToPageSize(size)) != 0)
+    LUAU_ASSERT(size == alignToPageSize(size));
+
+    if (munmap(mem, size) != 0)
         LUAU_ASSERT(!"Failed to deallocate block memory");
 }
 
@@ -94,8 +106,15 @@ namespace CodeGen
 {
 
 CodeAllocator::CodeAllocator(size_t blockSize, size_t maxTotalSize)
-    : blockSize(blockSize)
+    : CodeAllocator(blockSize, maxTotalSize, nullptr, nullptr)
-    , maxTotalSize(maxTotalSize)
+{
+}
+
+CodeAllocator::CodeAllocator(size_t blockSize, size_t maxTotalSize, AllocationCallback* allocationCallback, void* allocationCallbackContext)
+    : blockSize{blockSize}
+    , maxTotalSize{maxTotalSize}
+    , allocationCallback{allocationCallback}
+    , allocationCallbackContext{allocationCallbackContext}
 {
     LUAU_ASSERT(blockSize > kMaxReservedDataSize);
     LUAU_ASSERT(maxTotalSize >= blockSize);
@@ -207,5 +226,29 @@ bool CodeAllocator::allocateNewBlock(size_t& unwindInfoSize)
     return true;
 }
 
+uint8_t* CodeAllocator::allocatePages(size_t size) const
+{
+    const size_t pageAlignedSize = alignToPageSize(size);
+
+    uint8_t* const mem = allocatePagesImpl(pageAlignedSize);
+    if (mem == nullptr)
+        return nullptr;
+
+    if (allocationCallback)
+        allocationCallback(allocationCallbackContext, nullptr, 0, mem, pageAlignedSize);
+
+    return mem;
+}
+
+void CodeAllocator::freePages(uint8_t* mem, size_t size) const
+{
+    const size_t pageAlignedSize = alignToPageSize(size);
+
+    if (allocationCallback)
+        allocationCallback(allocationCallbackContext, mem, pageAlignedSize, nullptr, 0);
+
+    freePagesImpl(mem, pageAlignedSize);
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/CodeGen.cpp

@@ -65,7 +65,7 @@ static NativeProto createNativeProto(Proto* proto, const IrBuilder& ir)
     int sizecode = proto->sizecode;
 
     uint32_t* instOffsets = new uint32_t[sizecode];
-    uint32_t instTarget = ir.function.bcMapping[0].asmLocation;
+    uint32_t instTarget = ir.function.entryLocation;
 
     for (int i = 0; i < sizecode; i++)
     {
@@ -74,6 +74,9 @@ static NativeProto createNativeProto(Proto* proto, const IrBuilder& ir)
         instOffsets[i] = ir.function.bcMapping[i].asmLocation - instTarget;
     }
 
+    // Set first instruction offset to 0 so that entering this function still executes any generated entry code.
+    instOffsets[0] = 0;
+
     // entry target will be relocated when assembly is finalized
     return {proto, instOffsets, instTarget};
 }
@@ -202,11 +205,11 @@ bool isSupported()
 #endif
 }
 
-void create(lua_State* L)
+void create(lua_State* L, AllocationCallback* allocationCallback, void* allocationCallbackContext)
 {
     LUAU_ASSERT(isSupported());
 
-    std::unique_ptr<NativeState> data = std::make_unique<NativeState>();
+    std::unique_ptr<NativeState> data = std::make_unique<NativeState>(allocationCallback, allocationCallbackContext);
 
 #if defined(_WIN32)
     data->unwindBuilder = std::make_unique<UnwindBuilderWin>();
@@ -239,7 +242,12 @@ void create(lua_State* L)
     ecb->enter = onEnter;
 }
 
-void compile(lua_State* L, int idx, unsigned int flags)
+void create(lua_State* L)
+{
+    create(L, nullptr, nullptr);
+}
+
+void compile(lua_State* L, int idx, unsigned int flags, CompilationStats* stats)
 {
     LUAU_ASSERT(lua_isLfunction(L, idx));
     const TValue* func = luaA_toobject(L, idx);
@@ -318,13 +326,28 @@ void compile(lua_State* L, int idx, unsigned int flags)
         }
     }
 
-    for (NativeProto result : results)
+    for (const NativeProto& result : results)
     {
         // the memory is now managed by VM and will be freed via onDestroyFunction
         result.p->execdata = result.execdata;
         result.p->exectarget = uintptr_t(codeStart) + result.exectarget;
         result.p->codeentry = &kCodeEntryInsn;
     }
+
+    if (stats != nullptr)
+    {
+        for (const NativeProto& result : results)
+        {
+            stats->bytecodeSizeBytes += result.p->sizecode * sizeof(Instruction);
+
+            // Account for the native -> bytecode instruction offsets mapping:
+            stats->nativeMetadataSizeBytes += result.p->sizecode * sizeof(uint32_t);
+        }
+
+        stats->functionsCompiled += uint32_t(results.size());
+        stats->nativeCodeSizeBytes += build.code.size();
+        stats->nativeDataSizeBytes += build.data.size();
+    }
 }
 
 void setPerfLog(void* context, PerfLogFn logFn)

CodeGen/src/CodeGenA64.cpp

@@ -24,15 +24,6 @@ struct EntryLocations
     Label epilogueStart;
 };
 
-static void emitClearNativeFlag(AssemblyBuilderA64& build)
-{
-    build.ldr(x0, mem(rState, offsetof(lua_State, ci)));
-    build.ldr(w1, mem(x0, offsetof(CallInfo, flags)));
-    build.mov(w2, ~LUA_CALLINFO_NATIVE);
-    build.and_(w1, w1, w2);
-    build.str(w1, mem(x0, offsetof(CallInfo, flags)));
-}
-
 static void emitExit(AssemblyBuilderA64& build, bool continueInVm)
 {
     build.mov(x0, continueInVm);
@@ -40,14 +31,21 @@ static void emitExit(AssemblyBuilderA64& build, bool continueInVm)
     build.br(x1);
 }
 
-static void emitUpdatePcAndContinueInVm(AssemblyBuilderA64& build)
+static void emitUpdatePcForExit(AssemblyBuilderA64& build)
 {
     // x0 = pcpos * sizeof(Instruction)
     build.add(x0, rCode, x0);
     build.ldr(x1, mem(rState, offsetof(lua_State, ci)));
     build.str(x0, mem(x1, offsetof(CallInfo, savedpc)));
+}
 
-    emitExit(build, /* continueInVm */ true);
+static void emitClearNativeFlag(AssemblyBuilderA64& build)
+{
+    build.ldr(x0, mem(rState, offsetof(lua_State, ci)));
+    build.ldr(w1, mem(x0, offsetof(CallInfo, flags)));
+    build.mov(w2, ~LUA_CALLINFO_NATIVE);
+    build.and_(w1, w1, w2);
+    build.str(w1, mem(x0, offsetof(CallInfo, flags)));
 }
 
 static void emitInterrupt(AssemblyBuilderA64& build)
@@ -305,6 +303,11 @@ bool initHeaderFunctions(NativeState& data)
 
 void assembleHelpers(AssemblyBuilderA64& build, ModuleHelpers& helpers)
 {
+    if (build.logText)
+        build.logAppend("; updatePcAndContinueInVm\n");
+    build.setLabel(helpers.updatePcAndContinueInVm);
+    emitUpdatePcForExit(build);
+
     if (build.logText)
         build.logAppend("; exitContinueVmClearNativeFlag\n");
     build.setLabel(helpers.exitContinueVmClearNativeFlag);
@@ -320,11 +323,6 @@ void assembleHelpers(AssemblyBuilderA64& build, ModuleHelpers& helpers)
     build.setLabel(helpers.exitNoContinueVm);
     emitExit(build, /* continueInVm */ false);
 
-    if (build.logText)
-        build.logAppend("; updatePcAndContinueInVm\n");
-    build.setLabel(helpers.updatePcAndContinueInVm);
-    emitUpdatePcAndContinueInVm(build);
-
     if (build.logText)
         build.logAppend("; reentry\n");
     build.setLabel(helpers.reentry);

CodeGen/src/CodeGenLower.h

@@ -130,6 +130,11 @@ inline bool lowerImpl(AssemblyBuilder& build, IrLowering& lowering, IrFunction&
 
         build.setLabel(block.label);
 
+        if (blockIndex == function.entryBlock)
+        {
+            function.entryLocation = build.getLabelOffset(block.label);
+        }
+
         IrBlock& nextBlock = getNextBlock(function, sortedBlocks, dummy, i);
 
         for (uint32_t index = block.start; index <= block.finish; index++)

CodeGen/src/CodeGenX64.cpp

@@ -180,6 +180,11 @@ bool initHeaderFunctions(NativeState& data)
 
 void assembleHelpers(X64::AssemblyBuilderX64& build, ModuleHelpers& helpers)
 {
+    if (build.logText)
+        build.logAppend("; updatePcAndContinueInVm\n");
+    build.setLabel(helpers.updatePcAndContinueInVm);
+    emitUpdatePcForExit(build);
+
     if (build.logText)
         build.logAppend("; exitContinueVmClearNativeFlag\n");
     build.setLabel(helpers.exitContinueVmClearNativeFlag);
@@ -195,11 +200,6 @@ void assembleHelpers(X64::AssemblyBuilderX64& build, ModuleHelpers& helpers)
     build.setLabel(helpers.exitNoContinueVm);
     emitExit(build, /* continueInVm */ false);
 
-    if (build.logText)
-        build.logAppend("; updatePcAndContinueInVm\n");
-    build.setLabel(helpers.updatePcAndContinueInVm);
-    emitUpdatePcAndContinueInVm(build);
-
     if (build.logText)
         build.logAppend("; continueCallInVm\n");
     build.setLabel(helpers.continueCallInVm);

CodeGen/src/EmitBuiltinsX64.cpp

@@ -1,8 +1,9 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "EmitBuiltinsX64.h"
 
-#include "Luau/AssemblyBuilderX64.h"
 #include "Luau/Bytecode.h"
+
+#include "Luau/AssemblyBuilderX64.h"
 #include "Luau/IrCallWrapperX64.h"
 #include "Luau/IrRegAllocX64.h"
 

CodeGen/src/EmitCommon.h

@@ -25,7 +25,7 @@ struct ModuleHelpers
     Label exitContinueVm;
     Label exitNoContinueVm;
     Label exitContinueVmClearNativeFlag;
-    Label updatePcAndContinueInVm;
+    Label updatePcAndContinueInVm; // no reentry
     Label return_;
     Label interrupt;
 

CodeGen/src/EmitCommonX64.cpp

@@ -328,14 +328,12 @@ void emitFallback(IrRegAllocX64& regs, AssemblyBuilderX64& build, int offset, in
     emitUpdateBase(build);
 }
 
-void emitUpdatePcAndContinueInVm(AssemblyBuilderX64& build)
+void emitUpdatePcForExit(AssemblyBuilderX64& build)
 {
     // edx = pcpos * sizeof(Instruction)
     build.add(rdx, sCode);
     build.mov(rax, qword[rState + offsetof(lua_State, ci)]);
     build.mov(qword[rax + offsetof(CallInfo, savedpc)], rdx);
-
-    emitExit(build, /* continueInVm */ true);
 }
 
 void emitContinueCallInVm(AssemblyBuilderX64& build)

CodeGen/src/EmitCommonX64.h

@@ -180,7 +180,7 @@ void emitUpdateBase(AssemblyBuilderX64& build);
 void emitInterrupt(AssemblyBuilderX64& build);
 void emitFallback(IrRegAllocX64& regs, AssemblyBuilderX64& build, int offset, int pcpos);
 
-void emitUpdatePcAndContinueInVm(AssemblyBuilderX64& build);
+void emitUpdatePcForExit(AssemblyBuilderX64& build);
 void emitContinueCallInVm(AssemblyBuilderX64& build);
 
 void emitReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers);

CodeGen/src/IrAnalysis.cpp

@@ -186,75 +186,12 @@ void requireVariadicSequence(RegisterSet& sourceRs, const RegisterSet& defRs, ui
     }
 }
 
-static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock& block, RegisterSet& defRs, std::bitset<256>& capturedRegs)
+template<typename T>
+static void visitVmRegDefsUses(T& visitor, IrFunction& function, const IrBlock& block)
 {
-    RegisterSet inRs;
-
-    auto def = [&](IrOp op, int offset = 0) {
-        defRs.regs.set(vmRegOp(op) + offset, true);
-    };
-
-    auto use = [&](IrOp op, int offset = 0) {
-        if (!defRs.regs.test(vmRegOp(op) + offset))
-            inRs.regs.set(vmRegOp(op) + offset, true);
-    };
-
-    auto maybeDef = [&](IrOp op) {
-        if (op.kind == IrOpKind::VmReg)
-            defRs.regs.set(vmRegOp(op), true);
-    };
-
-    auto maybeUse = [&](IrOp op) {
-        if (op.kind == IrOpKind::VmReg)
-        {
-            if (!defRs.regs.test(vmRegOp(op)))
-                inRs.regs.set(vmRegOp(op), true);
-        }
-    };
-
-    auto defVarargs = [&](uint8_t varargStart) {
-        defRs.varargSeq = true;
-        defRs.varargStart = varargStart;
-    };
-
-    auto useVarargs = [&](uint8_t varargStart) {
-        requireVariadicSequence(inRs, defRs, varargStart);
-
-        // Variadic sequence has been consumed
-        defRs.varargSeq = false;
-        defRs.varargStart = 0;
-    };
-
-    auto defRange = [&](int start, int count) {
-        if (count == -1)
-        {
-            defVarargs(start);
-        }
-        else
-        {
-            for (int i = start; i < start + count; i++)
-                defRs.regs.set(i, true);
-        }
-    };
-
-    auto useRange = [&](int start, int count) {
-        if (count == -1)
-        {
-            useVarargs(start);
-        }
-        else
-        {
-            for (int i = start; i < start + count; i++)
-            {
-                if (!defRs.regs.test(i))
-                    inRs.regs.set(i, true);
-            }
-        }
-    };
-
     for (uint32_t instIdx = block.start; instIdx <= block.finish; instIdx++)
     {
-        const IrInst& inst = function.instructions[instIdx];
+        IrInst& inst = function.instructions[instIdx];
 
         // For correct analysis, all instruction uses must be handled before handling the definitions
         switch (inst.cmd)
@@ -264,7 +201,7 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
         case IrCmd::LOAD_DOUBLE:
         case IrCmd::LOAD_INT:
         case IrCmd::LOAD_TVALUE:
-            maybeUse(inst.a); // Argument can also be a VmConst
+            visitor.maybeUse(inst.a); // Argument can also be a VmConst
             break;
         case IrCmd::STORE_TAG:
         case IrCmd::STORE_POINTER:
@@ -272,63 +209,63 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
         case IrCmd::STORE_INT:
         case IrCmd::STORE_VECTOR:
         case IrCmd::STORE_TVALUE:
-            maybeDef(inst.a); // Argument can also be a pointer value
+            visitor.maybeDef(inst.a); // Argument can also be a pointer value
             break;
         case IrCmd::CMP_ANY:
-            use(inst.a);
+            visitor.use(inst.a);
-            use(inst.b);
+            visitor.use(inst.b);
             break;
         case IrCmd::JUMP_IF_TRUTHY:
         case IrCmd::JUMP_IF_FALSY:
-            use(inst.a);
+            visitor.use(inst.a);
             break;
             // A <- B, C
         case IrCmd::DO_ARITH:
         case IrCmd::GET_TABLE:
-            use(inst.b);
+            visitor.use(inst.b);
-            maybeUse(inst.c); // Argument can also be a VmConst
+            visitor.maybeUse(inst.c); // Argument can also be a VmConst
 
-            def(inst.a);
+            visitor.def(inst.a);
             break;
         case IrCmd::SET_TABLE:
-            use(inst.a);
+            visitor.use(inst.a);
-            use(inst.b);
+            visitor.use(inst.b);
-            maybeUse(inst.c); // Argument can also be a VmConst
+            visitor.maybeUse(inst.c); // Argument can also be a VmConst
             break;
             // A <- B
         case IrCmd::DO_LEN:
-            use(inst.b);
+            visitor.use(inst.b);
 
-            def(inst.a);
+            visitor.def(inst.a);
             break;
         case IrCmd::GET_IMPORT:
-            def(inst.a);
+            visitor.def(inst.a);
             break;
         case IrCmd::CONCAT:
-            useRange(vmRegOp(inst.a), function.uintOp(inst.b));
+            visitor.useRange(vmRegOp(inst.a), function.uintOp(inst.b));
 
-            defRange(vmRegOp(inst.a), function.uintOp(inst.b));
+            visitor.defRange(vmRegOp(inst.a), function.uintOp(inst.b));
             break;
         case IrCmd::GET_UPVALUE:
-            def(inst.a);
+            visitor.def(inst.a);
             break;
         case IrCmd::SET_UPVALUE:
-            use(inst.b);
+            visitor.use(inst.b);
             break;
         case IrCmd::PREPARE_FORN:
-            use(inst.a);
+            visitor.use(inst.a);
-            use(inst.b);
+            visitor.use(inst.b);
-            use(inst.c);
+            visitor.use(inst.c);
 
-            def(inst.a);
+            visitor.def(inst.a);
-            def(inst.b);
+            visitor.def(inst.b);
-            def(inst.c);
+            visitor.def(inst.c);
             break;
         case IrCmd::INTERRUPT:
             break;
         case IrCmd::BARRIER_OBJ:
         case IrCmd::BARRIER_TABLE_FORWARD:
-            use(inst.b);
+            visitor.use(inst.b);
             break;
         case IrCmd::CLOSE_UPVALS:
             // Closing an upvalue should be counted as a register use (it copies the fresh register value)
@@ -336,23 +273,23 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
             // Because we don't plan to optimize captured registers atm, we skip full dataflow analysis for them right now
             break;
         case IrCmd::CAPTURE:
-            maybeUse(inst.a);
+            visitor.maybeUse(inst.a);
 
             if (function.uintOp(inst.b) == 1)
-                capturedRegs.set(vmRegOp(inst.a), true);
+                visitor.capture(vmRegOp(inst.a));
             break;
         case IrCmd::SETLIST:
-            use(inst.b);
+            visitor.use(inst.b);
-            useRange(vmRegOp(inst.c), function.intOp(inst.d));
+            visitor.useRange(vmRegOp(inst.c), function.intOp(inst.d));
             break;
         case IrCmd::CALL:
-            use(inst.a);
+            visitor.use(inst.a);
-            useRange(vmRegOp(inst.a) + 1, function.intOp(inst.b));
+            visitor.useRange(vmRegOp(inst.a) + 1, function.intOp(inst.b));
 
-            defRange(vmRegOp(inst.a), function.intOp(inst.c));
+            visitor.defRange(vmRegOp(inst.a), function.intOp(inst.c));
             break;
         case IrCmd::RETURN:
-            useRange(vmRegOp(inst.a), function.intOp(inst.b));
+            visitor.useRange(vmRegOp(inst.a), function.intOp(inst.b));
             break;
 
             // TODO: FASTCALL is more restrictive than INVOKE_FASTCALL; we should either determine the exact semantics, or rework it
@@ -364,89 +301,89 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
                 {
                     LUAU_ASSERT(inst.d.kind == IrOpKind::VmReg && vmRegOp(inst.d) == vmRegOp(inst.c) + 1);
 
-                    useRange(vmRegOp(inst.c), count);
+                    visitor.useRange(vmRegOp(inst.c), count);
                 }
                 else
                 {
                     if (count >= 1)
-                        use(inst.c);
+                        visitor.use(inst.c);
 
                     if (count >= 2)
-                        maybeUse(inst.d); // Argument can also be a VmConst
+                        visitor.maybeUse(inst.d); // Argument can also be a VmConst
                 }
             }
             else
             {
-                useVarargs(vmRegOp(inst.c));
+                visitor.useVarargs(vmRegOp(inst.c));
             }
 
             // Multiple return sequences (count == -1) are defined by ADJUST_STACK_TO_REG
             if (int count = function.intOp(inst.f); count != -1)
-                defRange(vmRegOp(inst.b), count);
+                visitor.defRange(vmRegOp(inst.b), count);
             break;
         case IrCmd::FORGLOOP:
             // First register is not used by instruction, we check that it's still 'nil' with CHECK_TAG
-            use(inst.a, 1);
+            visitor.use(inst.a, 1);
-            use(inst.a, 2);
+            visitor.use(inst.a, 2);
 
-            def(inst.a, 2);
+            visitor.def(inst.a, 2);
-            defRange(vmRegOp(inst.a) + 3, function.intOp(inst.b));
+            visitor.defRange(vmRegOp(inst.a) + 3, function.intOp(inst.b));
             break;
         case IrCmd::FORGLOOP_FALLBACK:
-            useRange(vmRegOp(inst.a), 3);
+            visitor.useRange(vmRegOp(inst.a), 3);
 
-            def(inst.a, 2);
+            visitor.def(inst.a, 2);
-            defRange(vmRegOp(inst.a) + 3, uint8_t(function.intOp(inst.b))); // ignore most significant bit
+            visitor.defRange(vmRegOp(inst.a) + 3, uint8_t(function.intOp(inst.b))); // ignore most significant bit
             break;
         case IrCmd::FORGPREP_XNEXT_FALLBACK:
-            use(inst.b);
+            visitor.use(inst.b);
             break;
         case IrCmd::FALLBACK_GETGLOBAL:
-            def(inst.b);
+            visitor.def(inst.b);
             break;
         case IrCmd::FALLBACK_SETGLOBAL:
-            use(inst.b);
+            visitor.use(inst.b);
             break;
         case IrCmd::FALLBACK_GETTABLEKS:
-            use(inst.c);
+            visitor.use(inst.c);
 
-            def(inst.b);
+            visitor.def(inst.b);
             break;
         case IrCmd::FALLBACK_SETTABLEKS:
-            use(inst.b);
+            visitor.use(inst.b);
-            use(inst.c);
+            visitor.use(inst.c);
             break;
         case IrCmd::FALLBACK_NAMECALL:
-            use(inst.c);
+            visitor.use(inst.c);
 
-            defRange(vmRegOp(inst.b), 2);
+            visitor.defRange(vmRegOp(inst.b), 2);
             break;
         case IrCmd::FALLBACK_PREPVARARGS:
             // No effect on explicitly referenced registers
             break;
         case IrCmd::FALLBACK_GETVARARGS:
-            defRange(vmRegOp(inst.b), function.intOp(inst.c));
+            visitor.defRange(vmRegOp(inst.b), function.intOp(inst.c));
             break;
         case IrCmd::FALLBACK_DUPCLOSURE:
-            def(inst.b);
+            visitor.def(inst.b);
             break;
         case IrCmd::FALLBACK_FORGPREP:
-            use(inst.b);
+            visitor.use(inst.b);
 
-            defRange(vmRegOp(inst.b), 3);
+            visitor.defRange(vmRegOp(inst.b), 3);
             break;
         case IrCmd::ADJUST_STACK_TO_REG:
-            defRange(vmRegOp(inst.a), -1);
+            visitor.defRange(vmRegOp(inst.a), -1);
             break;
         case IrCmd::ADJUST_STACK_TO_TOP:
             // While this can be considered to be a vararg consumer, it is already handled in fastcall instructions
             break;
         case IrCmd::GET_TYPEOF:
-            use(inst.a);
+            visitor.use(inst.a);
             break;
 
         case IrCmd::FINDUPVAL:
-            use(inst.a);
+            visitor.use(inst.a);
             break;
 
         default:
@@ -460,8 +397,102 @@ static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock&
             break;
         }
     }
+}
 
-    return inRs;
+struct BlockVmRegLiveInComputation
+{
+    BlockVmRegLiveInComputation(RegisterSet& defRs, std::bitset<256>& capturedRegs)
+        : defRs(defRs)
+        , capturedRegs(capturedRegs)
+    {
+    }
+
+    RegisterSet& defRs;
+    std::bitset<256>& capturedRegs;
+
+    RegisterSet inRs;
+
+    void def(IrOp op, int offset = 0)
+    {
+        defRs.regs.set(vmRegOp(op) + offset, true);
+    }
+
+    void use(IrOp op, int offset = 0)
+    {
+        if (!defRs.regs.test(vmRegOp(op) + offset))
+            inRs.regs.set(vmRegOp(op) + offset, true);
+    }
+
+    void maybeDef(IrOp op)
+    {
+        if (op.kind == IrOpKind::VmReg)
+            defRs.regs.set(vmRegOp(op), true);
+    }
+
+    void maybeUse(IrOp op)
+    {
+        if (op.kind == IrOpKind::VmReg)
+        {
+            if (!defRs.regs.test(vmRegOp(op)))
+                inRs.regs.set(vmRegOp(op), true);
+        }
+    }
+
+    void defVarargs(uint8_t varargStart)
+    {
+        defRs.varargSeq = true;
+        defRs.varargStart = varargStart;
+    }
+
+    void useVarargs(uint8_t varargStart)
+    {
+        requireVariadicSequence(inRs, defRs, varargStart);
+
+        // Variadic sequence has been consumed
+        defRs.varargSeq = false;
+        defRs.varargStart = 0;
+    }
+
+    void defRange(int start, int count)
+    {
+        if (count == -1)
+        {
+            defVarargs(start);
+        }
+        else
+        {
+            for (int i = start; i < start + count; i++)
+                defRs.regs.set(i, true);
+        }
+    }
+
+    void useRange(int start, int count)
+    {
+        if (count == -1)
+        {
+            useVarargs(start);
+        }
+        else
+        {
+            for (int i = start; i < start + count; i++)
+            {
+                if (!defRs.regs.test(i))
+                    inRs.regs.set(i, true);
+            }
+        }
+    }
+
+    void capture(int reg)
+    {
+        capturedRegs.set(reg, true);
+    }
+};
+
+static RegisterSet computeBlockLiveInRegSet(IrFunction& function, const IrBlock& block, RegisterSet& defRs, std::bitset<256>& capturedRegs)
+{
+    BlockVmRegLiveInComputation visitor(defRs, capturedRegs);
+    visitVmRegDefsUses(visitor, function, block);
+    return visitor.inRs;
 }
 
 // The algorithm used here is commonly known as backwards data-flow analysis.

CodeGen/src/IrBuilder.cpp

@@ -1,7 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/IrBuilder.h"
 
-#include "Luau/IrAnalysis.h"
+#include "Luau/IrData.h"
 #include "Luau/IrUtils.h"
 
 #include "IrTranslation.h"
@@ -22,10 +22,14 @@ IrBuilder::IrBuilder()
 {
 }
 
+static bool hasTypedParameters(Proto* proto)
+{
+    return proto->typeinfo && proto->numparams != 0;
+}
+
 static void buildArgumentTypeChecks(IrBuilder& build, Proto* proto)
 {
-    if (!proto->typeinfo || proto->numparams == 0)
+    LUAU_ASSERT(hasTypedParameters(proto));
-        return;
 
     for (int i = 0; i < proto->numparams; ++i)
     {
@@ -53,31 +57,31 @@ static void buildArgumentTypeChecks(IrBuilder& build, Proto* proto)
         switch (tag)
         {
         case LBC_TYPE_NIL:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TNIL), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TNIL), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_BOOLEAN:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TBOOLEAN), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TBOOLEAN), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_NUMBER:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TNUMBER), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TNUMBER), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_STRING:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TSTRING), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TSTRING), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_TABLE:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TTABLE), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TTABLE), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_FUNCTION:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TFUNCTION), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TFUNCTION), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_THREAD:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TTHREAD), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TTHREAD), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_USERDATA:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TUSERDATA), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TUSERDATA), build.vmExit(kVmExitEntryGuardPc));
             break;
         case LBC_TYPE_VECTOR:
-            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TVECTOR), build.undef(), build.constInt(1));
+            build.inst(IrCmd::CHECK_TAG, load, build.constTag(LUA_TVECTOR), build.vmExit(kVmExitEntryGuardPc));
             break;
         }
 
@@ -103,11 +107,28 @@ void IrBuilder::buildFunctionIr(Proto* proto)
     function.proto = proto;
     function.variadic = proto->is_vararg != 0;
 
+    // Reserve entry block
+    bool generateTypeChecks = hasTypedParameters(proto);
+    IrOp entry = generateTypeChecks ? block(IrBlockKind::Internal) : IrOp{};
+
     // Rebuild original control flow blocks
     rebuildBytecodeBasicBlocks(proto);
 
     function.bcMapping.resize(proto->sizecode, {~0u, ~0u});
 
+    if (generateTypeChecks)
+    {
+        beginBlock(entry);
+        buildArgumentTypeChecks(*this, proto);
+        inst(IrCmd::JUMP, blockAtInst(0));
+    }
+    else
+    {
+        entry = blockAtInst(0);
+    }
+
+    function.entryBlock = entry.index;
+
     // Translate all instructions to IR inside blocks
     for (int i = 0; i < proto->sizecode;)
     {
@@ -123,9 +144,6 @@ void IrBuilder::buildFunctionIr(Proto* proto)
         if (instIndexToBlock[i] != kNoAssociatedBlockIndex)
             beginBlock(blockAtInst(i));
 
-        if (i == 0)
-            buildArgumentTypeChecks(*this, proto);
-
         // We skip dead bytecode instructions when they appear after block was already terminated
         if (!inTerminatedBlock)
         {

CodeGen/src/IrDump.cpp

@@ -402,7 +402,7 @@ void toString(IrToStringContext& ctx, IrOp op)
         append(ctx.result, "U%d", vmUpvalueOp(op));
         break;
     case IrOpKind::VmExit:
-        append(ctx.result, "exit(%d)", op.index);
+        append(ctx.result, "exit(%d)", vmExitOp(op));
         break;
     }
 }

CodeGen/src/IrLoweringA64.cpp

@@ -1,10 +1,8 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "IrLoweringA64.h"
 
-#include "Luau/CodeGen.h"
 #include "Luau/DenseHash.h"
-#include "Luau/IrAnalysis.h"
+#include "Luau/IrData.h"
-#include "Luau/IrDump.h"
 #include "Luau/IrUtils.h"
 
 #include "EmitCommonA64.h"
@@ -189,7 +187,7 @@ IrLoweringA64::IrLoweringA64(AssemblyBuilderA64& build, ModuleHelpers& helpers,
     });
 }
 
-void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
+void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, const IrBlock& next)
 {
     valueTracker.beforeInstLowering(inst);
 
@@ -566,7 +564,7 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         break;
     }
     case IrCmd::JUMP:
-        if (inst.a.kind == IrOpKind::VmExit)
+        if (inst.a.kind == IrOpKind::Undef || inst.a.kind == IrOpKind::VmExit)
         {
             Label fresh;
             build.b(getTargetLabel(inst.a, fresh));
@@ -1047,9 +1045,8 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         break;
     case IrCmd::CHECK_TAG:
     {
-        bool continueInVm = (inst.d.kind == IrOpKind::Constant && intOp(inst.d));
         Label fresh; // used when guard aborts execution or jumps to a VM exit
-        Label& fail = continueInVm ? helpers.exitContinueVmClearNativeFlag : getTargetLabel(inst.c, fresh);
+        Label& fail = getTargetLabel(inst.c, fresh);
 
         // To support DebugLuauAbortingChecks, CHECK_TAG with VmReg has to be handled
         RegisterA64 tag = inst.a.kind == IrOpKind::VmReg ? regs.allocTemp(KindA64::w) : regOp(inst.a);
@@ -1066,7 +1063,7 @@ void IrLoweringA64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
             build.cmp(tag, tagOp(inst.b));
             build.b(ConditionA64::NotEqual, fail);
         }
-        if (!continueInVm)
+
         finalizeTargetLabel(inst.c, fresh);
         break;
     }
@@ -1862,7 +1859,10 @@ void IrLoweringA64::finishFunction()
 
     for (ExitHandler& handler : exitHandlers)
     {
+        LUAU_ASSERT(handler.pcpos != kVmExitEntryGuardPc);
+
         build.setLabel(handler.self);
+
         build.mov(x0, handler.pcpos * sizeof(Instruction));
         build.b(helpers.updatePcAndContinueInVm);
     }
@@ -1873,12 +1873,12 @@ bool IrLoweringA64::hasError() const
     return error || regs.error;
 }
 
-bool IrLoweringA64::isFallthroughBlock(IrBlock target, IrBlock next)
+bool IrLoweringA64::isFallthroughBlock(const IrBlock& target, const IrBlock& next)
 {
     return target.start == next.start;
 }
 
-void IrLoweringA64::jumpOrFallthrough(IrBlock& target, IrBlock& next)
+void IrLoweringA64::jumpOrFallthrough(IrBlock& target, const IrBlock& next)
 {
     if (!isFallthroughBlock(target, next))
         build.b(target.label);
@@ -1891,7 +1891,11 @@ Label& IrLoweringA64::getTargetLabel(IrOp op, Label& fresh)
 
     if (op.kind == IrOpKind::VmExit)
     {
-        if (uint32_t* index = exitHandlerMap.find(op.index))
+        // Special exit case that doesn't have to update pcpos
+        if (vmExitOp(op) == kVmExitEntryGuardPc)
+            return helpers.exitContinueVmClearNativeFlag;
+
+        if (uint32_t* index = exitHandlerMap.find(vmExitOp(op)))
             return exitHandlers[*index].self;
 
         return fresh;
@@ -1906,10 +1910,10 @@ void IrLoweringA64::finalizeTargetLabel(IrOp op, Label& fresh)
     {
         emitAbort(build, fresh);
     }
-    else if (op.kind == IrOpKind::VmExit && fresh.id != 0)
+    else if (op.kind == IrOpKind::VmExit && fresh.id != 0 && fresh.id != helpers.exitContinueVmClearNativeFlag.id)
     {
-        exitHandlerMap[op.index] = uint32_t(exitHandlers.size());
+        exitHandlerMap[vmExitOp(op)] = uint32_t(exitHandlers.size());
-        exitHandlers.push_back({fresh, op.index});
+        exitHandlers.push_back({fresh, vmExitOp(op)});
     }
 }
 

CodeGen/src/IrLoweringA64.h

@@ -25,14 +25,14 @@ struct IrLoweringA64
 {
     IrLoweringA64(AssemblyBuilderA64& build, ModuleHelpers& helpers, IrFunction& function);
 
-    void lowerInst(IrInst& inst, uint32_t index, IrBlock& next);
+    void lowerInst(IrInst& inst, uint32_t index, const IrBlock& next);
     void finishBlock();
     void finishFunction();
 
     bool hasError() const;
 
-    bool isFallthroughBlock(IrBlock target, IrBlock next);
+    bool isFallthroughBlock(const IrBlock& target, const IrBlock& next);
-    void jumpOrFallthrough(IrBlock& target, IrBlock& next);
+    void jumpOrFallthrough(IrBlock& target, const IrBlock& next);
 
     Label& getTargetLabel(IrOp op, Label& fresh);
     void finalizeTargetLabel(IrOp op, Label& fresh);

CodeGen/src/IrLoweringX64.cpp

@@ -1,19 +1,19 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "IrLoweringX64.h"
 
-#include "Luau/CodeGen.h"
 #include "Luau/DenseHash.h"
-#include "Luau/IrAnalysis.h"
+#include "Luau/IrData.h"
-#include "Luau/IrCallWrapperX64.h"
-#include "Luau/IrDump.h"
 #include "Luau/IrUtils.h"
 
+#include "Luau/IrCallWrapperX64.h"
+
 #include "EmitBuiltinsX64.h"
 #include "EmitCommonX64.h"
 #include "EmitInstructionX64.h"
 #include "NativeState.h"
 
 #include "lstate.h"
+#include "lgc.h"
 
 namespace Luau
 {
@@ -59,7 +59,7 @@ void IrLoweringX64::storeDoubleAsFloat(OperandX64 dst, IrOp src)
     build.vmovss(dst, tmp.reg);
 }
 
-void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
+void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, const IrBlock& next)
 {
     regs.currInstIdx = index;
 
@@ -565,24 +565,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         break;
     }
     case IrCmd::JUMP:
-        if (inst.a.kind == IrOpKind::VmExit)
+        jumpOrAbortOnUndef(inst.a, next);
-        {
-            if (uint32_t* index = exitHandlerMap.find(inst.a.index))
-            {
-                build.jmp(exitHandlers[*index].self);
-            }
-            else
-            {
-                Label self;
-                build.jmp(self);
-                exitHandlerMap[inst.a.index] = uint32_t(exitHandlers.size());
-                exitHandlers.push_back({self, inst.a.index});
-            }
-        }
-        else
-        {
-            jumpOrFallthrough(blockOp(inst.a), next);
-        }
         break;
     case IrCmd::JUMP_IF_TRUTHY:
         jumpIfTruthy(build, vmRegOp(inst.a), labelOp(inst.b), labelOp(inst.c));
@@ -975,12 +958,9 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         callPrepareForN(regs, build, vmRegOp(inst.a), vmRegOp(inst.b), vmRegOp(inst.c));
         break;
     case IrCmd::CHECK_TAG:
-    {
-        bool continueInVm = (inst.d.kind == IrOpKind::Constant && intOp(inst.d));
         build.cmp(memRegTagOp(inst.a), tagOp(inst.b));
-        jumpOrAbortOnUndef(ConditionX64::NotEqual, ConditionX64::Equal, inst.c, continueInVm);
+        jumpOrAbortOnUndef(ConditionX64::NotEqual, inst.c, next);
         break;
-    }
     case IrCmd::CHECK_TRUTHY:
     {
         // Constant tags which don't require boolean value check should've been removed in constant folding
@@ -992,7 +972,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         {
             // Fail to fallback on 'nil' (falsy)
             build.cmp(memRegTagOp(inst.a), LUA_TNIL);
-            jumpOrAbortOnUndef(ConditionX64::Equal, ConditionX64::NotEqual, inst.c);
+            jumpOrAbortOnUndef(ConditionX64::Equal, inst.c, next);
 
             // Skip value test if it's not a boolean (truthy)
             build.cmp(memRegTagOp(inst.a), LUA_TBOOLEAN);
@@ -1001,7 +981,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
 
         // fail to fallback on 'false' boolean value (falsy)
         build.cmp(memRegUintOp(inst.b), 0);
-        jumpOrAbortOnUndef(ConditionX64::Equal, ConditionX64::NotEqual, inst.c);
+        jumpOrAbortOnUndef(ConditionX64::Equal, inst.c, next);
 
         if (inst.a.kind != IrOpKind::Constant)
             build.setLabel(skip);
@@ -1009,11 +989,11 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
     }
     case IrCmd::CHECK_READONLY:
         build.cmp(byte[regOp(inst.a) + offsetof(Table, readonly)], 0);
-        jumpOrAbortOnUndef(ConditionX64::NotEqual, ConditionX64::Equal, inst.b);
+        jumpOrAbortOnUndef(ConditionX64::NotEqual, inst.b, next);
         break;
     case IrCmd::CHECK_NO_METATABLE:
         build.cmp(qword[regOp(inst.a) + offsetof(Table, metatable)], 0);
-        jumpOrAbortOnUndef(ConditionX64::NotEqual, ConditionX64::Equal, inst.b);
+        jumpOrAbortOnUndef(ConditionX64::NotEqual, inst.b, next);
         break;
     case IrCmd::CHECK_SAFE_ENV:
     {
@@ -1023,7 +1003,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         build.mov(tmp.reg, qword[tmp.reg + offsetof(Closure, env)]);
         build.cmp(byte[tmp.reg + offsetof(Table, safeenv)], 0);
 
-        jumpOrAbortOnUndef(ConditionX64::Equal, ConditionX64::NotEqual, inst.a);
+        jumpOrAbortOnUndef(ConditionX64::Equal, inst.a, next);
         break;
     }
     case IrCmd::CHECK_ARRAY_SIZE:
@@ -1034,7 +1014,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
         else
             LUAU_ASSERT(!"Unsupported instruction form");
 
-        jumpOrAbortOnUndef(ConditionX64::BelowEqual, ConditionX64::NotBelowEqual, inst.c);
+        jumpOrAbortOnUndef(ConditionX64::BelowEqual, inst.c, next);
         break;
     case IrCmd::JUMP_SLOT_MATCH:
     case IrCmd::CHECK_SLOT_MATCH:
@@ -1080,7 +1060,7 @@ void IrLoweringX64::lowerInst(IrInst& inst, uint32_t index, IrBlock& next)
 
         build.mov(tmp.reg, dword[regOp(inst.a) + offsetof(LuaNode, key) + kOffsetOfTKeyTagNext]);
         build.shr(tmp.reg, kTKeyTagBits);
-        jumpOrAbortOnUndef(ConditionX64::NotZero, ConditionX64::Zero, inst.b);
+        jumpOrAbortOnUndef(ConditionX64::NotZero, inst.b, next);
         break;
     }
     case IrCmd::INTERRUPT:
@@ -1583,7 +1563,10 @@ void IrLoweringX64::finishFunction()
 
     for (ExitHandler& handler : exitHandlers)
     {
+        LUAU_ASSERT(handler.pcpos != kVmExitEntryGuardPc);
+
         build.setLabel(handler.self);
+
         build.mov(edx, handler.pcpos * sizeof(Instruction));
         build.jmp(helpers.updatePcAndContinueInVm);
     }
@@ -1598,50 +1581,81 @@ bool IrLoweringX64::hasError() const
     return false;
 }
 
-bool IrLoweringX64::isFallthroughBlock(IrBlock target, IrBlock next)
+bool IrLoweringX64::isFallthroughBlock(const IrBlock& target, const IrBlock& next)
 {
     return target.start == next.start;
 }
 
-void IrLoweringX64::jumpOrFallthrough(IrBlock& target, IrBlock& next)
+Label& IrLoweringX64::getTargetLabel(IrOp op, Label& fresh)
+{
+    if (op.kind == IrOpKind::Undef)
+        return fresh;
+
+    if (op.kind == IrOpKind::VmExit)
+    {
+        // Special exit case that doesn't have to update pcpos
+        if (vmExitOp(op) == kVmExitEntryGuardPc)
+            return helpers.exitContinueVmClearNativeFlag;
+
+        if (uint32_t* index = exitHandlerMap.find(vmExitOp(op)))
+            return exitHandlers[*index].self;
+
+        return fresh;
+    }
+
+    return labelOp(op);
+}
+
+void IrLoweringX64::finalizeTargetLabel(IrOp op, Label& fresh)
+{
+    if (op.kind == IrOpKind::VmExit && fresh.id != 0 && fresh.id != helpers.exitContinueVmClearNativeFlag.id)
+    {
+        exitHandlerMap[vmExitOp(op)] = uint32_t(exitHandlers.size());
+        exitHandlers.push_back({fresh, vmExitOp(op)});
+    }
+}
+
+void IrLoweringX64::jumpOrFallthrough(IrBlock& target, const IrBlock& next)
 {
     if (!isFallthroughBlock(target, next))
         build.jmp(target.label);
 }
 
-void IrLoweringX64::jumpOrAbortOnUndef(ConditionX64 cond, ConditionX64 condInverse, IrOp targetOrUndef, bool continueInVm)
+void IrLoweringX64::jumpOrAbortOnUndef(ConditionX64 cond, IrOp target, const IrBlock& next)
 {
-    if (targetOrUndef.kind == IrOpKind::Undef)
+    Label fresh;
+    Label& label = getTargetLabel(target, fresh);
+
+    if (target.kind == IrOpKind::Undef)
     {
-        if (continueInVm)
+        if (cond == ConditionX64::Count)
         {
-            build.jcc(cond, helpers.exitContinueVmClearNativeFlag);
+            build.ud2(); // Unconditional jump to abort is just an abort
-            return;
+        }
+        else
+        {
+            build.jcc(getReverseCondition(cond), label);
+            build.ud2();
+            build.setLabel(label);
+        }
+    }
+    else if (cond == ConditionX64::Count)
+    {
+        // Unconditional jump can be skipped if it's a fallthrough
+        if (target.kind == IrOpKind::VmExit || !isFallthroughBlock(blockOp(target), next))
+            build.jmp(label);
+    }
+    else
+    {
+        build.jcc(cond, label);
     }
 
-        Label skip;
+    finalizeTargetLabel(target, fresh);
-        build.jcc(condInverse, skip);
-        build.ud2();
-        build.setLabel(skip);
 }
-    else if (targetOrUndef.kind == IrOpKind::VmExit)
+
+void IrLoweringX64::jumpOrAbortOnUndef(IrOp target, const IrBlock& next)
 {
-        if (uint32_t* index = exitHandlerMap.find(targetOrUndef.index))
+    jumpOrAbortOnUndef(ConditionX64::Count, target, next);
-        {
-            build.jcc(cond, exitHandlers[*index].self);
-        }
-        else
-        {
-            Label self;
-            build.jcc(cond, self);
-            exitHandlerMap[targetOrUndef.index] = uint32_t(exitHandlers.size());
-            exitHandlers.push_back({self, targetOrUndef.index});
-        }
-    }
-    else
-    {
-        build.jcc(cond, labelOp(targetOrUndef));
-    }
 }
 
 OperandX64 IrLoweringX64::memRegDoubleOp(IrOp op)

CodeGen/src/IrLoweringX64.h

@@ -27,15 +27,20 @@ struct IrLoweringX64
 {
     IrLoweringX64(AssemblyBuilderX64& build, ModuleHelpers& helpers, IrFunction& function);
 
-    void lowerInst(IrInst& inst, uint32_t index, IrBlock& next);
+    void lowerInst(IrInst& inst, uint32_t index, const IrBlock& next);
     void finishBlock();
     void finishFunction();
 
     bool hasError() const;
 
-    bool isFallthroughBlock(IrBlock target, IrBlock next);
+    bool isFallthroughBlock(const IrBlock& target, const IrBlock& next);
-    void jumpOrFallthrough(IrBlock& target, IrBlock& next);
+    void jumpOrFallthrough(IrBlock& target, const IrBlock& next);
-    void jumpOrAbortOnUndef(ConditionX64 cond, ConditionX64 condInverse, IrOp targetOrUndef, bool continueInVm = false);
+
+    Label& getTargetLabel(IrOp op, Label& fresh);
+    void finalizeTargetLabel(IrOp op, Label& fresh);
+
+    void jumpOrAbortOnUndef(ConditionX64 cond, IrOp target, const IrBlock& next);
+    void jumpOrAbortOnUndef(IrOp target, const IrBlock& next);
 
     void storeDoubleAsFloat(OperandX64 dst, IrOp src);
 

CodeGen/src/NativeState.cpp

@@ -23,7 +23,12 @@ constexpr unsigned kBlockSize = 4 * 1024 * 1024;
 constexpr unsigned kMaxTotalSize = 256 * 1024 * 1024;
 
 NativeState::NativeState()
-    : codeAllocator(kBlockSize, kMaxTotalSize)
+    : NativeState(nullptr, nullptr)
+{
+}
+
+NativeState::NativeState(AllocationCallback* allocationCallback, void* allocationCallbackContext)
+    : codeAllocator{kBlockSize, kMaxTotalSize, allocationCallback, allocationCallbackContext}
 {
 }
 

CodeGen/src/NativeState.h

@@ -112,6 +112,7 @@ using GateFn = int (*)(lua_State*, Proto*, uintptr_t, NativeContext*);
 struct NativeState
 {
     NativeState();
+    NativeState(AllocationCallback* allocationCallback, void* allocationCallbackContext);
     ~NativeState();
 
     CodeAllocator codeAllocator;

CodeGen/src/OptimizeConstProp.cpp

@@ -2,7 +2,7 @@
 #include "Luau/OptimizeConstProp.h"
 
 #include "Luau/DenseHash.h"
-#include "Luau/IrAnalysis.h"
+#include "Luau/IrData.h"
 #include "Luau/IrBuilder.h"
 #include "Luau/IrUtils.h"
 

Compiler/src/Compiler.cpp

@@ -26,9 +26,6 @@ LUAU_FASTINTVARIABLE(LuauCompileInlineThreshold, 25)
 LUAU_FASTINTVARIABLE(LuauCompileInlineThresholdMaxBoost, 300)
 LUAU_FASTINTVARIABLE(LuauCompileInlineDepth, 5)
 
-LUAU_FASTFLAGVARIABLE(LuauCompileFunctionType, false)
-LUAU_FASTFLAGVARIABLE(LuauCompileNativeComment, false)
-
 LUAU_FASTFLAGVARIABLE(LuauCompileFixBuiltinArity, false)
 
 LUAU_FASTFLAGVARIABLE(LuauCompileFoldMathK, false)
@@ -209,12 +206,9 @@ struct Compiler
 
         setDebugLine(func);
 
-        if (FFlag::LuauCompileFunctionType)
-        {
         // note: we move types out of typeMap which is safe because compileFunction is only called once per function
         if (std::string* funcType = typeMap.find(func))
             bytecode.setFunctionTypeInfo(std::move(*funcType));
-        }
 
         if (func->vararg)
             bytecode.emitABC(LOP_PREPVARARGS, uint8_t(self + func->args.size), 0, 0);
@@ -3620,7 +3614,6 @@ struct Compiler
         {
             node->body->visit(this);
 
-            if (FFlag::LuauCompileFunctionType)
             for (AstLocal* arg : node->args)
                 hasTypes |= arg->annotation != nullptr;
 
@@ -3863,7 +3856,7 @@ void compileOrThrow(BytecodeBuilder& bytecode, const ParseResult& parseResult, c
         if (hc.header && hc.content.compare(0, 9, "optimize ") == 0)
             options.optimizationLevel = std::max(0, std::min(2, atoi(hc.content.c_str() + 9)));
 
-        if (FFlag::LuauCompileNativeComment && hc.header && hc.content == "native")
+        if (hc.header && hc.content == "native")
         {
             mainFlags |= LPF_NATIVE_MODULE;
             options.optimizationLevel = 2; // note: this might be removed in the future in favor of --!optimize
@@ -3916,7 +3909,7 @@ void compileOrThrow(BytecodeBuilder& bytecode, const ParseResult& parseResult, c
     root->visit(&functionVisitor);
 
     // computes type information for all functions based on type annotations
-    if (FFlag::LuauCompileFunctionType && functionVisitor.hasTypes)
+    if (functionVisitor.hasTypes)
         buildTypeMap(compiler.typeMap, root, options.vectorType);
 
     for (AstExprFunction* expr : functions)

Compiler/src/Types.cpp

@@ -1,8 +1,8 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-#include "Luau/BytecodeBuilder.h"
-
 #include "Types.h"
 
+#include "Luau/BytecodeBuilder.h"
+
 namespace Luau
 {
 

Compiler/src/Types.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "Luau/Ast.h"
+#include "Luau/DenseHash.h"
 
 #include <string>
 

Sources.cmake

@@ -163,6 +163,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/include/Luau/IostreamHelpers.h
     Analysis/include/Luau/JsonEmitter.h
     Analysis/include/Luau/Linter.h
+    Analysis/include/Luau/LinterConfig.h
     Analysis/include/Luau/LValue.h
     Analysis/include/Luau/Metamethods.h
     Analysis/include/Luau/Module.h
@@ -221,6 +222,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/src/IostreamHelpers.cpp
     Analysis/src/JsonEmitter.cpp
     Analysis/src/Linter.cpp
+    Analysis/src/LinterConfig.cpp
     Analysis/src/LValue.cpp
     Analysis/src/Module.cpp
     Analysis/src/Normalize.cpp

VM/src/lmathlib.cpp

@@ -7,8 +7,6 @@
 #include <math.h>
 #include <time.h>
 
-LUAU_FASTFLAGVARIABLE(LuauFasterNoise, false)
-
 #undef PI
 #define PI (3.14159265358979323846)
 #define RADIANS_PER_DEGREE (PI / 180.0)
@@ -277,27 +275,6 @@ static int math_randomseed(lua_State* L)
     return 0;
 }
 
-// TODO: Delete with LuauFasterNoise
-static const unsigned char kPerlin[512] = {151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99,
-    37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174,
-    20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41,
-    55, 46, 245, 40, 244, 102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86,
-    164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17,
-    182, 189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98, 108, 110,
-    79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14,
-    239, 107, 49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24,
-    72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180,
-
-    151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247,
-    120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74,
-    165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54, 65,
-    25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52,
-    217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213,
-    119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112,
-    104, 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199,
-    106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61,
-    156, 180};
-
 static const unsigned char kPerlinHash[257] = {151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99,
     37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174,
     20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41,
@@ -321,61 +298,14 @@ static float perlin_lerp(float t, float a, float b)
     return a + t * (b - a);
 }
 
-static float grad(unsigned char hash, float x, float y, float z)
-{
-    LUAU_ASSERT(!FFlag::LuauFasterNoise);
-    unsigned char h = hash & 15;
-    float u = (h < 8) ? x : y;
-    float v = (h < 4) ? y : (h == 12 || h == 14) ? x : z;
-
-    return (h & 1 ? -u : u) + (h & 2 ? -v : v);
-}
-
 static float perlin_grad(int hash, float x, float y, float z)
 {
     const float* g = kPerlinGrad[hash & 15];
     return g[0] * x + g[1] * y + g[2] * z;
 }
 
-static float perlin_dep(float x, float y, float z)
-{
-    LUAU_ASSERT(!FFlag::LuauFasterNoise);
-    float xflr = floorf(x);
-    float yflr = floorf(y);
-    float zflr = floorf(z);
-
-    int xi = int(xflr) & 255;
-    int yi = int(yflr) & 255;
-    int zi = int(zflr) & 255;
-
-    float xf = x - xflr;
-    float yf = y - yflr;
-    float zf = z - zflr;
-
-    float u = perlin_fade(xf);
-    float v = perlin_fade(yf);
-    float w = perlin_fade(zf);
-
-    const unsigned char* p = kPerlin;
-
-    int a = p[xi] + yi;
-    int aa = p[a] + zi;
-    int ab = p[a + 1] + zi;
-
-    int b = p[xi + 1] + yi;
-    int ba = p[b] + zi;
-    int bb = p[b + 1] + zi;
-
-    return perlin_lerp(w,
-        perlin_lerp(v, perlin_lerp(u, grad(p[aa], xf, yf, zf), grad(p[ba], xf - 1, yf, zf)),
-            perlin_lerp(u, grad(p[ab], xf, yf - 1, zf), grad(p[bb], xf - 1, yf - 1, zf))),
-        perlin_lerp(v, perlin_lerp(u, grad(p[aa + 1], xf, yf, zf - 1), grad(p[ba + 1], xf - 1, yf, zf - 1)),
-            perlin_lerp(u, grad(p[ab + 1], xf, yf - 1, zf - 1), grad(p[bb + 1], xf - 1, yf - 1, zf - 1))));
-}
-
 static float perlin(float x, float y, float z)
 {
-    LUAU_ASSERT(FFlag::LuauFasterNoise);
     float xflr = floorf(x);
     float yflr = floorf(y);
     float zflr = floorf(z);
@@ -411,8 +341,6 @@ static float perlin(float x, float y, float z)
 }
 
 static int math_noise(lua_State* L)
-{
-    if (FFlag::LuauFasterNoise)
 {
     int nx, ny, nz;
     double x = lua_tonumberx(L, 1, &nx);
@@ -428,18 +356,6 @@ static int math_noise(lua_State* L)
     lua_pushnumber(L, r);
     return 1;
 }
-    else
-    {
-        double x = luaL_checknumber(L, 1);
-        double y = luaL_optnumber(L, 2, 0.0);
-        double z = luaL_optnumber(L, 3, 0.0);
-
-        double r = perlin_dep((float)x, (float)y, (float)z);
-
-        lua_pushnumber(L, r);
-        return 1;
-    }
-}
 
 static int math_clamp(lua_State* L)
 {

VM/src/lstrlib.cpp

@@ -9,6 +9,7 @@
 #include <stdio.h>
 
 LUAU_FASTFLAGVARIABLE(LuauFasterInterp, false)
+LUAU_FASTFLAGVARIABLE(LuauFasterFormatS, false)
 
 // macro to `unsign' a character
 #define uchar(c) ((unsigned char)(c))
@@ -1028,6 +1029,22 @@ static int str_format(lua_State* L)
             {
                 size_t l;
                 const char* s = luaL_checklstring(L, arg, &l);
+                if (FFlag::LuauFasterFormatS)
+                {
+                    // no precision and string is too long to be formatted, or no format necessary to begin with
+                    if (form[2] == '\0' || (!strchr(form, '.') && l >= 100))
+                    {
+                        luaL_addlstring(&b, s, l, -1);
+                        continue; // skip the `luaL_addlstring' at the end
+                    }
+                    else
+                    {
+                        snprintf(buff, sizeof(buff), form, s);
+                        break;
+                    }
+                }
+                else
+                {
                     if (!strchr(form, '.') && l >= 100)
                     {
                         /* no precision and string is too long to be formatted;
@@ -1042,6 +1059,7 @@ static int str_format(lua_State* L)
                         break;
                     }
                 }
+            }
             case '*':
             {
                 if (FFlag::LuauFasterInterp || formatItemSize != 1)

VM/src/ltablib.cpp

@@ -10,8 +10,6 @@
 #include "ldebug.h"
 #include "lvm.h"
 
-LUAU_FASTFLAGVARIABLE(LuauFasterTableConcat, false)
-
 static int foreachi(lua_State* L)
 {
     luaL_checktype(L, 1, LUA_TTABLE);
@@ -222,7 +220,7 @@ static int tmove(lua_State* L)
 static void addfield(lua_State* L, luaL_Buffer* b, int i)
 {
     int tt = lua_rawgeti(L, 1, i);
-    if (FFlag::LuauFasterTableConcat ? (tt != LUA_TSTRING && tt != LUA_TNUMBER) : !lua_isstring(L, -1))
+    if (tt != LUA_TSTRING && tt != LUA_TNUMBER)
         luaL_error(L, "invalid value (%s) at index %d in table for 'concat'", luaL_typename(L, -1), i);
     luaL_addvalue(b);
 }

VM/src/lvmload.cpp

@@ -13,8 +13,6 @@
 
 #include <string.h>
 
-LUAU_FASTFLAGVARIABLE(LuauLoadCheckGC, false)
-
 // TODO: RAII deallocation doesn't work for longjmp builds if a memory error happens
 template<typename T>
 struct TempBuffer
@@ -181,7 +179,6 @@ int luau_load(lua_State* L, const char* chunkname, const char* data, size_t size
     }
 
     // we will allocate a fair amount of memory so check GC before we do
-    if (FFlag::LuauLoadCheckGC)
     luaC_checkGC(L);
 
     // pause GC for the duration of deserialization - some objects we're creating aren't rooted

bench/micro_tests/test_StringInterp.lua

@@ -36,6 +36,13 @@ bench.runCode(function()
     end
 end, "interp: interp number")
 
+bench.runCode(function()
+    local ok = "hello!"
+    for j=1,1e6 do
+        local _ = string.format("j=%s", ok)
+    end
+end, "interp: %s format")
+
 bench.runCode(function()
 	local ok = "hello!"
     for j=1,1e6 do

tests/CodeAllocator.test.cpp

@@ -47,6 +47,56 @@ TEST_CASE("CodeAllocation")
     CHECK(nativeEntry == nativeData + kCodeAlignment);
 }
 
+TEST_CASE("CodeAllocationCallbacks")
+{
+    struct AllocationData
+    {
+        size_t bytesAllocated = 0;
+        size_t bytesFreed = 0;
+    };
+
+    AllocationData allocationData{};
+
+    const auto allocationCallback = [](void* context, void* oldPointer, size_t oldSize, void* newPointer, size_t newSize)
+    {
+        AllocationData& allocationData = *static_cast<AllocationData*>(context);
+        if (oldPointer != nullptr)
+        {
+            CHECK(oldSize != 0);
+
+            allocationData.bytesFreed += oldSize;
+        }
+
+        if (newPointer != nullptr)
+        {
+            CHECK(newSize != 0);
+
+            allocationData.bytesAllocated += newSize;
+        }
+    };
+
+    const size_t blockSize = 1024 * 1024;
+    const size_t maxTotalSize = 1024 * 1024;
+
+    {
+        CodeAllocator allocator(blockSize, maxTotalSize, allocationCallback, &allocationData);
+
+        uint8_t* nativeData = nullptr;
+        size_t sizeNativeData = 0;
+        uint8_t* nativeEntry = nullptr;
+
+        std::vector<uint8_t> code;
+        code.resize(128);
+
+        REQUIRE(allocator.allocate(nullptr, 0, code.data(), code.size(), nativeData, sizeNativeData, nativeEntry));
+        CHECK(allocationData.bytesAllocated == blockSize);
+        CHECK(allocationData.bytesFreed == 0);
+    }
+
+    CHECK(allocationData.bytesAllocated == blockSize);
+    CHECK(allocationData.bytesFreed == blockSize);
+}
+
 TEST_CASE("CodeAllocationFailure")
 {
     size_t blockSize = 3000;

tests/Compiler.test.cpp

@@ -7100,8 +7100,6 @@ L1: RETURN R3 1
 
 TEST_CASE("EncodedTypeTable")
 {
-    ScopedFastFlag sff("LuauCompileFunctionType", true);
-
     CHECK_EQ("\n" + compileTypeTable(R"(
 function myfunc(test: string, num: number)
     print(test)
@@ -7153,8 +7151,6 @@ Str:test(234)
 
 TEST_CASE("HostTypesAreUserdata")
 {
-    ScopedFastFlag sff("LuauCompileFunctionType", true);
-
     CHECK_EQ("\n" + compileTypeTable(R"(
 function myfunc(test: string, num: number)
     print(test)
@@ -7181,8 +7177,6 @@ end
 
 TEST_CASE("HostTypesVector")
 {
-    ScopedFastFlag sff("LuauCompileFunctionType", true);
-
     CHECK_EQ("\n" + compileTypeTable(R"(
 function myfunc(test: Instance, pos: Vector3)
 end
@@ -7206,8 +7200,6 @@ end
 
 TEST_CASE("TypeAliasScoping")
 {
-    ScopedFastFlag sff("LuauCompileFunctionType", true);
-
     CHECK_EQ("\n" + compileTypeTable(R"(
 do
     type Part = number
@@ -7242,8 +7234,6 @@ type Instance = string
 
 TEST_CASE("TypeAliasResolve")
 {
-    ScopedFastFlag sff("LuauCompileFunctionType", true);
-
     CHECK_EQ("\n" + compileTypeTable(R"(
 type Foo1 = number
 type Foo2 = { number }

tests/Conformance.test.cpp

@@ -266,6 +266,12 @@ static void* limitedRealloc(void* ud, void* ptr, size_t osize, size_t nsize)
 
 TEST_SUITE_BEGIN("Conformance");
 
+TEST_CASE("CodegenSupported")
+{
+    if (codegen && !luau_codegen_supported())
+        MESSAGE("Native code generation is not supported by the current configuration and will be disabled");
+}
+
 TEST_CASE("Assert")
 {
     runConformance("assert.lua");
@@ -1726,7 +1732,6 @@ TEST_CASE("Native")
 TEST_CASE("NativeTypeAnnotations")
 {
     ScopedFastFlag bytecodeVersion4("BytecodeVersion4", true);
-    ScopedFastFlag luauCompileFunctionType("LuauCompileFunctionType", true);
 
     // This tests requires code to run natively, otherwise all 'is_native' checks will fail
     if (!codegen || !luau_codegen_supported())

tests/Differ.test.cpp

@@ -1528,4 +1528,43 @@ TEST_CASE_FIXTURE(DifferFixture, "equal_generictp_cyclic")
     compareTypesEq("foo", "almostFoo");
 }
 
+TEST_CASE_FIXTURE(DifferFixture, "symbol_forward")
+{
+    CheckResult result = check(R"(
+        local foo = 5
+        local almostFoo = "five"
+    )");
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    INFO(Luau::toString(requireType("foo")));
+    INFO(Luau::toString(requireType("almostFoo")));
+
+    compareTypesNe("foo", "almostFoo",
+        R"(DiffError: these two types are not equal because the left type at foo has type number, while the right type at almostFoo has type string)",
+        true);
+}
+
+TEST_CASE_FIXTURE(DifferFixture, "newlines")
+{
+    CheckResult result = check(R"(
+        local foo = 5
+        local almostFoo = "five"
+    )");
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    INFO(Luau::toString(requireType("foo")));
+    INFO(Luau::toString(requireType("almostFoo")));
+
+    compareTypesNe("foo", "almostFoo",
+        R"(DiffError: these two types are not equal because the left type at
+    foo
+has type
+    number,
+while the right type at
+    almostFoo
+has type
+    string)",
+        true, true);
+}
+
 TEST_SUITE_END();

tests/Fixture.h

@@ -160,14 +160,37 @@ void createSomeClasses(Frontend* frontend);
 template<typename BaseFixture>
 struct DifferFixtureGeneric : BaseFixture
 {
-    void compareNe(TypeId left, TypeId right, const std::string& expectedMessage)
+    std::string normalizeWhitespace(std::string msg)
+    {
+        std::string normalizedMsg = "";
+        bool wasWhitespace = true;
+        for (char c : msg)
+        {
+            bool isWhitespace = c == ' ' || c == '\n';
+            if (wasWhitespace && isWhitespace)
+                continue;
+            normalizedMsg += isWhitespace ? ' ' : c;
+            wasWhitespace = isWhitespace;
+        }
+        if (wasWhitespace)
+            normalizedMsg.pop_back();
+        return normalizedMsg;
+    }
+
+    void compareNe(TypeId left, TypeId right, const std::string& expectedMessage, bool multiLine)
+    {
+        compareNe(left, std::nullopt, right, std::nullopt, expectedMessage, multiLine);
+    }
+
+    void compareNe(TypeId left, std::optional<std::string> symbolLeft, TypeId right, std::optional<std::string> symbolRight,
+        const std::string& expectedMessage, bool multiLine)
     {
         std::string diffMessage;
         try
         {
-            DifferResult diffRes = diff(left, right);
+            DifferResult diffRes = diffWithSymbols(left, right, symbolLeft, symbolRight);
             REQUIRE_MESSAGE(diffRes.diffError.has_value(), "Differ did not report type error, even though types are unequal");
-            diffMessage = diffRes.diffError->toString();
+            diffMessage = diffRes.diffError->toString(multiLine);
         }
         catch (const InternalCompilerError& e)
         {
@@ -176,9 +199,19 @@ struct DifferFixtureGeneric : BaseFixture
         CHECK_EQ(expectedMessage, diffMessage);
     }
 
-    void compareTypesNe(const std::string& leftSymbol, const std::string& rightSymbol, const std::string& expectedMessage)
+    void compareTypesNe(const std::string& leftSymbol, const std::string& rightSymbol, const std::string& expectedMessage, bool forwardSymbol = false,
+        bool multiLine = false)
     {
-        compareNe(BaseFixture::requireType(leftSymbol), BaseFixture::requireType(rightSymbol), expectedMessage);
+        if (forwardSymbol)
+        {
+            compareNe(
+                BaseFixture::requireType(leftSymbol), leftSymbol, BaseFixture::requireType(rightSymbol), rightSymbol, expectedMessage, multiLine);
+        }
+        else
+        {
+            compareNe(
+                BaseFixture::requireType(leftSymbol), std::nullopt, BaseFixture::requireType(rightSymbol), std::nullopt, expectedMessage, multiLine);
+        }
     }
 
     void compareEq(TypeId left, TypeId right)

tests/Linter.test.cpp

@@ -1657,8 +1657,6 @@ _ = (math.random() < 0.5 and false) or 42 -- currently ignored
 
 TEST_CASE_FIXTURE(Fixture, "WrongComment")
 {
-    ScopedFastFlag sff("LuauLintNativeComment", true);
-
     LintResult result = lint(R"(
 --!strict
 --!struct

tests/Module.test.cpp

@@ -1,5 +1,6 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Clone.h"
+#include "Luau/Common.h"
 #include "Luau/Module.h"
 #include "Luau/Scope.h"
 #include "Luau/RecursionCounter.h"
@@ -7,11 +8,13 @@
 
 #include "Fixture.h"
 
+#include "ScopedFlags.h"
 #include "doctest.h"
 
 using namespace Luau;
 
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
+LUAU_FASTFLAG(LuauStacklessTypeClone)
 
 TEST_SUITE_BEGIN("ModuleTests");
 
@@ -78,7 +81,7 @@ TEST_CASE_FIXTURE(Fixture, "is_within_comment_parse_result")
 TEST_CASE_FIXTURE(Fixture, "dont_clone_persistent_primitive")
 {
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     // numberType is persistent.  We leave it as-is.
     TypeId newNumber = clone(builtinTypes->numberType, dest, cloneState);
@@ -88,7 +91,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_clone_persistent_primitive")
 TEST_CASE_FIXTURE(Fixture, "deepClone_non_persistent_primitive")
 {
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     // Create a new number type that isn't persistent
     unfreeze(frontend.globals.globalTypes);
@@ -129,7 +132,7 @@ TEST_CASE_FIXTURE(Fixture, "deepClone_cyclic_table")
     TypeId ty = requireType("Cyclic");
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
     TypeId cloneTy = clone(ty, dest, cloneState);
 
     TableType* ttv = getMutable<TableType>(cloneTy);
@@ -147,7 +150,7 @@ TEST_CASE_FIXTURE(Fixture, "deepClone_cyclic_table")
     REQUIRE(methodReturnType);
 
     CHECK_MESSAGE(methodReturnType == cloneTy, toString(methodType, {true}) << " should be pointer identical to " << toString(cloneTy, {true}));
-    CHECK_EQ(2, dest.typePacks.size()); // one for the function args, and another for its return type
+    CHECK_EQ(FFlag::LuauStacklessTypeClone ? 1 : 2, dest.typePacks.size()); // one for the function args, and another for its return type
     CHECK_EQ(2, dest.types.size());                                         // One table and one function
 }
 
@@ -165,7 +168,7 @@ TEST_CASE_FIXTURE(Fixture, "deepClone_cyclic_table_2")
 
     TypeArena dest;
 
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
     TypeId cloneTy = clone(tableTy, dest, cloneState);
     TableType* ctt = getMutable<TableType>(cloneTy);
     REQUIRE(ctt);
@@ -209,7 +212,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "builtin_types_point_into_globalTypes_arena")
 TEST_CASE_FIXTURE(Fixture, "deepClone_union")
 {
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     unfreeze(frontend.globals.globalTypes);
     TypeId oldUnion = frontend.globals.globalTypes.addType(UnionType{{builtinTypes->numberType, builtinTypes->stringType}});
@@ -224,7 +227,7 @@ TEST_CASE_FIXTURE(Fixture, "deepClone_union")
 TEST_CASE_FIXTURE(Fixture, "deepClone_intersection")
 {
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     unfreeze(frontend.globals.globalTypes);
     TypeId oldIntersection = frontend.globals.globalTypes.addType(IntersectionType{{builtinTypes->numberType, builtinTypes->stringType}});
@@ -251,7 +254,7 @@ TEST_CASE_FIXTURE(Fixture, "clone_class")
         std::nullopt, &exampleMetaClass, {}, {}, "Test"}};
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     TypeId cloned = clone(&exampleClass, dest, cloneState);
     const ClassType* ctv = get<ClassType>(cloned);
@@ -274,12 +277,12 @@ TEST_CASE_FIXTURE(Fixture, "clone_free_types")
     TypePackVar freeTp(FreeTypePack{TypeLevel{}});
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     TypeId clonedTy = clone(freeTy, dest, cloneState);
     CHECK(get<FreeType>(clonedTy));
 
-    cloneState = {};
+    cloneState = {builtinTypes};
     TypePackId clonedTp = clone(&freeTp, dest, cloneState);
     CHECK(get<FreeTypePack>(clonedTp));
 }
@@ -291,7 +294,7 @@ TEST_CASE_FIXTURE(Fixture, "clone_free_tables")
     ttv->state = TableState::Free;
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     TypeId cloned = clone(&tableTy, dest, cloneState);
     const TableType* clonedTtv = get<TableType>(cloned);
@@ -332,6 +335,8 @@ TEST_CASE_FIXTURE(Fixture, "clone_recursion_limit")
 #else
     int limit = 400;
 #endif
+
+    ScopedFastFlag sff{"LuauStacklessTypeClone", false};
     ScopedFastInt luauTypeCloneRecursionLimit{"LuauTypeCloneRecursionLimit", limit};
 
     TypeArena src;
@@ -348,11 +353,39 @@ TEST_CASE_FIXTURE(Fixture, "clone_recursion_limit")
     }
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     CHECK_THROWS_AS(clone(table, dest, cloneState), RecursionLimitException);
 }
 
+TEST_CASE_FIXTURE(Fixture, "clone_iteration_limit")
+{
+    ScopedFastFlag sff{"LuauStacklessTypeClone", true};
+    ScopedFastInt sfi{"LuauTypeCloneIterationLimit", 500};
+
+    TypeArena src;
+
+    TypeId table = src.addType(TableType{});
+    TypeId nested = table;
+
+    for (int i = 0; i < 2500; i++)
+    {
+        TableType* ttv = getMutable<TableType>(nested);
+        ttv->props["a"].setType(src.addType(TableType{}));
+        nested = ttv->props["a"].type();
+    }
+
+    TypeArena dest;
+    CloneState cloneState{builtinTypes};
+
+    TypeId ty = clone(table, dest, cloneState);
+    CHECK(get<ErrorType>(ty));
+
+    // Cloning it again is an important test.
+    TypeId ty2 = clone(table, dest, cloneState);
+    CHECK(get<ErrorType>(ty2));
+}
+
 // Unions should never be cyclic, but we should clone them correctly even if
 // they are.
 TEST_CASE_FIXTURE(Fixture, "clone_cyclic_union")
@@ -368,7 +401,7 @@ TEST_CASE_FIXTURE(Fixture, "clone_cyclic_union")
     uu->options.push_back(u);
 
     TypeArena dest;
-    CloneState cloneState;
+    CloneState cloneState{builtinTypes};
 
     TypeId cloned = clone(u, dest, cloneState);
     REQUIRE(cloned);

tests/ToString.test.cpp

@@ -831,4 +831,39 @@ TEST_CASE_FIXTURE(Fixture, "tostring_unsee_ttv_if_array")
     CHECK(toString(requireType("y")) == "({string}, {string}) -> ()");
 }
 
+TEST_CASE_FIXTURE(Fixture, "tostring_error_mismatch")
+{
+    ScopedFastFlag sff[] = {
+        {"LuauIndentTypeMismatch", true},
+    };
+
+    ScopedFastInt sfi[] = {
+        {"LuauIndentTypeMismatchMaxTypeLength", 10},
+    };
+
+    CheckResult result = check(R"(
+--!strict
+   function f1() : {a : number, b : string, c : { d : number}}
+     return { a = 1, b = "a", c = {d = "a"}}
+   end
+
+)");
+    std::string expected = R"(Type
+    '{ a: number, b: string, c: { d: string } }'
+could not be converted into
+    '{| a: number, b: string, c: {| d: number |} |}'
+caused by:
+  Property 'c' is not compatible. 
+Type
+    '{ d: string }'
+could not be converted into
+    '{| d: number |}'
+caused by:
+  Property 'd' is not compatible. 
+Type 'string' could not be converted into 'number' in an invariant context)";
+    std::string actual = toString(result.errors[0]);
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK(expected == actual);
+}
 TEST_SUITE_END();

tests/TypeInfer.aliases.test.cpp

@@ -187,8 +187,11 @@ TEST_CASE_FIXTURE(Fixture, "mutually_recursive_aliases")
 
 TEST_CASE_FIXTURE(Fixture, "generic_aliases")
 {
-    ScopedFastFlag sff_DebugLuauDeferredConstraintResolution{"DebugLuauDeferredConstraintResolution", true};
+    ScopedFastFlag sff[] = {
-
+        {"DebugLuauDeferredConstraintResolution", true},
+        {"LuauIndentTypeMismatch", true},
+    };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
         type T<a> = { v: a }
         local x: T<number> = { v = 123 }
@@ -197,18 +200,22 @@ TEST_CASE_FIXTURE(Fixture, "generic_aliases")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-
+    const std::string expected = R"(Type 'bad' could not be converted into 'T<number>'
-    const char* expectedError = "Type 'bad' could not be converted into 'T<number>'\n"
+caused by:
-                                "caused by:\n"
+  Property 'v' is not compatible. 
-                                "  Property 'v' is not compatible. Type 'string' could not be converted into 'number' in an invariant context";
+Type 'string' could not be converted into 'number' in an invariant context)";
-
     CHECK(result.errors[0].location == Location{{4, 31}, {4, 44}});
-    CHECK(toString(result.errors[0]) == expectedError);
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "dependent_generic_aliases")
 {
-    ScopedFastFlag sff_DebugLuauDeferredConstraintResolution{"DebugLuauDeferredConstraintResolution", true};
+    ScopedFastFlag sff[] = {
+        {"DebugLuauDeferredConstraintResolution", true},
+        {"LuauIndentTypeMismatch", true},
+    };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
 
     CheckResult result = check(R"(
         type T<a> = { v: a }
@@ -218,15 +225,16 @@ TEST_CASE_FIXTURE(Fixture, "dependent_generic_aliases")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-
+    const std::string expected = R"(Type 'bad' could not be converted into 'U<number>'
-    std::string expectedError = "Type 'bad' could not be converted into 'U<number>'\n"
+caused by:
-                                "caused by:\n"
+  Property 't' is not compatible. 
-                                "  Property 't' is not compatible. Type '{ v: string }' could not be converted into 'T<number>'\n"
+Type '{ v: string }' could not be converted into 'T<number>'
-                                "caused by:\n"
+caused by:
-                                "  Property 'v' is not compatible. Type 'string' could not be converted into 'number' in an invariant context";
+  Property 'v' is not compatible. 
+Type 'string' could not be converted into 'number' in an invariant context)";
 
     CHECK(result.errors[0].location == Location{{4, 31}, {4, 52}});
-    CHECK(toString(result.errors[0]) == expectedError);
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "mutually_recursive_generic_aliases")
@@ -261,7 +269,7 @@ TEST_CASE_FIXTURE(Fixture, "mutually_recursive_types_errors")
     // We had a UAF in this example caused by not cloning type function arguments
     ModulePtr module = frontend.moduleResolver.getModule("MainModule");
     unfreeze(module->interfaceTypes);
-    copyErrors(module->errors, module->interfaceTypes);
+    copyErrors(module->errors, module->interfaceTypes, builtinTypes);
     freeze(module->interfaceTypes);
     module->internalTypes.clear();
     module->astTypes.clear();

tests/TypeInfer.builtins.test.cpp

@@ -132,7 +132,11 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "sort_with_predicate")
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "sort_with_bad_predicate")
 {
-    ScopedFastFlag sff{"LuauAlwaysCommitInferencesOfFunctionCalls", true};
+    ScopedFastFlag sff[] = {
+        {"LuauAlwaysCommitInferencesOfFunctionCalls", true},
+        {"LuauIndentTypeMismatch", true},
+    };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
 
     CheckResult result = check(R"(
         --!strict
@@ -142,12 +146,20 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "sort_with_bad_predicate")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(R"(Type '(number, number) -> boolean' could not be converted into '((string, string) -> boolean)?'
+    const std::string expected = R"(Type
+    '(number, number) -> boolean'
+could not be converted into
+    '((string, string) -> boolean)?'
 caused by:
-  None of the union options are compatible. For example: Type '(number, number) -> boolean' could not be converted into '(string, string) -> boolean'
+  None of the union options are compatible. For example: 
+Type
+    '(number, number) -> boolean'
+could not be converted into
+    '(string, string) -> boolean'
 caused by:
-  Argument #1 type is not compatible. Type 'string' could not be converted into 'number')",
+  Argument #1 type is not compatible. 
-        toString(result.errors[0]));
+Type 'string' could not be converted into 'number')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "strings_have_methods")

tests/TypeInfer.classes.test.cpp

@@ -367,8 +367,11 @@ b.X = 2 -- real Vector2.X is also read-only
 
 TEST_CASE_FIXTURE(ClassFixture, "detailed_class_unification_error")
 {
-    ScopedFastFlag sff{"LuauAlwaysCommitInferencesOfFunctionCalls", true};
+    ScopedFastFlag sff[] = {
-
+        {"LuauAlwaysCommitInferencesOfFunctionCalls", true},
+        {"LuauIndentTypeMismatch", true},
+    };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
 local function foo(v)
     return v.X :: number + string.len(v.Y)
@@ -380,10 +383,11 @@ b(a)
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-
+    const std::string expected = R"(Type 'Vector2' could not be converted into '{- X: number, Y: string -}'
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'Vector2' could not be converted into '{- X: number, Y: string -}'
 caused by:
-  Property 'Y' is not compatible. Type 'number' could not be converted into 'string')");
+  Property 'Y' is not compatible. 
+Type 'number' could not be converted into 'string')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(ClassFixture, "class_type_mismatch_with_name_conflict")
@@ -453,6 +457,8 @@ TEST_CASE_FIXTURE(ClassFixture, "index_instance_property_nonstrict")
 
 TEST_CASE_FIXTURE(ClassFixture, "type_mismatch_invariance_required_for_error")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
 type A = { x: ChildClass }
 type B = { x: BaseClass }
@@ -462,9 +468,11 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'A' could not be converted into 'B'
+    const std::string expected = R"(Type 'A' could not be converted into 'B'
 caused by:
-  Property 'x' is not compatible. Type 'ChildClass' could not be converted into 'BaseClass' in an invariant context)");
+  Property 'x' is not compatible. 
+Type 'ChildClass' could not be converted into 'BaseClass' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(ClassFixture, "callable_classes")

tests/TypeInfer.functions.test.cpp

@@ -1095,6 +1095,9 @@ TEST_CASE_FIXTURE(Fixture, "return_type_by_overload")
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "infer_anonymous_function_arguments")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     // Simple direct arg to arg propagation
     CheckResult result = check(R"(
 type Table = { x: number, y: number }
@@ -1150,129 +1153,27 @@ f(function(a, b, c, ...) return a + b end)
 
     LUAU_REQUIRE_ERRORS(result);
 
+    std::string expected;
     if (FFlag::LuauInstantiateInSubtyping)
     {
-        CHECK_EQ(R"(Type '<a>(number, number, a) -> number' could not be converted into '(number, number) -> number'
+        expected = R"(Type
+    '<a>(number, number, a) -> number'
+could not be converted into
+    '(number, number) -> number'
 caused by:
-  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
+  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)";
-            toString(result.errors[0]));
     }
     else
     {
-        CHECK_EQ(R"(Type '(number, number, a) -> number' could not be converted into '(number, number) -> number'
+        expected = R"(Type
+    '(number, number, a) -> number'
+could not be converted into
+    '(number, number) -> number'
 caused by:
-  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
+  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)";
-            toString(result.errors[0]));
     }
 
-    // Infer from variadic packs into elements
+    CHECK_EQ(expected, toString(result.errors[0]));
-    result = check(R"(
-function f(a: (...number) -> number) return a(1, 2) end
-f(function(a, b) return a + b end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-
-    // Infer from variadic packs into variadic packs
-    result = check(R"(
-type Table = { x: number, y: number }
-function f(a: (...Table) -> number) return a({x = 1, y = 2}, {x = 3, y = 4}) end
-f(function(a, ...) local b = ... return b.z end)
-    )");
-
-    LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));
-
-    // Return type inference
-    result = check(R"(
-type Table = { x: number, y: number }
-function f(a: (number) -> Table) return a(4) end
-f(function(x) return x * 2 end)
-    )");
-
-    LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ("Type 'number' could not be converted into 'Table'", toString(result.errors[0]));
-
-    // Return type doesn't inference 'nil'
-    result = check(R"(
-        function f(a: (number) -> nil) return a(4) end
-        f(function(x) print(x) end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-}
-
-TEST_CASE_FIXTURE(BuiltinsFixture, "infer_anonymous_function_arguments")
-{
-    // Simple direct arg to arg propagation
-    CheckResult result = check(R"(
-type Table = { x: number, y: number }
-local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
-f(function(a) return a.x + a.y end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-
-    // An optional function is accepted, but since we already provide a function, nil can be ignored
-    result = check(R"(
-type Table = { x: number, y: number }
-local function f(a: ((Table) -> number)?) if a then return a({x = 1, y = 2}) else return 0 end end
-f(function(a) return a.x + a.y end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-
-    // Make sure self calls match correct index
-    result = check(R"(
-type Table = { x: number, y: number }
-local x = {}
-x.b = {x = 1, y = 2}
-function x:f(a: (Table) -> number) return a(self.b) end
-x:f(function(a) return a.x + a.y end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-
-    // Mix inferred and explicit argument types
-    result = check(R"(
-function f(a: (a: number, b: number, c: boolean) -> number) return a(1, 2, true) end
-f(function(a: number, b, c) return c and a + b or b - a end)
-    )");
-
-    LUAU_REQUIRE_NO_ERRORS(result);
-
-    // Anonymous function has a variadic pack
-    result = check(R"(
-type Table = { x: number, y: number }
-local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
-f(function(...) return select(1, ...).z end)
-    )");
-
-    LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));
-
-    // Can't accept more arguments than provided
-    result = check(R"(
-function f(a: (a: number, b: number) -> number) return a(1, 2) end
-f(function(a, b, c, ...) return a + b end)
-    )");
-
-    LUAU_REQUIRE_ERRORS(result);
-
-    if (FFlag::LuauInstantiateInSubtyping)
-    {
-        CHECK_EQ(R"(Type '<a>(number, number, a) -> number' could not be converted into '(number, number) -> number'
-caused by:
-  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
-            toString(result.errors[0]));
-    }
-    else
-    {
-        CHECK_EQ(R"(Type '(number, number, a) -> number' could not be converted into '(number, number) -> number'
-caused by:
-  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
-            toString(result.errors[0]));
-    }
 
     // Infer from variadic packs into elements
     result = check(R"(
@@ -1376,6 +1277,8 @@ end
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_arg_count")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
 type A = (number, number) -> string
 type B = (number) -> string
@@ -1385,13 +1288,20 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number) -> string'
+    const std::string expected = R"(Type
+    '(number, number) -> string'
+could not be converted into
+    '(number) -> string'
 caused by:
-  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)");
+  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_arg")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type A = (number, number) -> string
 type B = (number, string) -> string
@@ -1401,13 +1311,21 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number, string) -> string'
+    const std::string expected = R"(Type
+    '(number, number) -> string'
+could not be converted into
+    '(number, string) -> string'
 caused by:
-  Argument #2 type is not compatible. Type 'string' could not be converted into 'number')");
+  Argument #2 type is not compatible. 
+Type 'string' could not be converted into 'number')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret_count")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type A = (number, number) -> (number)
 type B = (number, number) -> (number, boolean)
@@ -1417,13 +1335,20 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> number' could not be converted into '(number, number) -> (number, boolean)'
+    const std::string expected = R"(Type
+    '(number, number) -> number'
+could not be converted into
+    '(number, number) -> (number, boolean)'
 caused by:
-  Function only returns 1 value, but 2 are required here)");
+  Function only returns 1 value, but 2 are required here)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type A = (number, number) -> string
 type B = (number, number) -> number
@@ -1433,13 +1358,21 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number, number) -> number'
+    const std::string expected = R"(Type
+    '(number, number) -> string'
+could not be converted into
+    '(number, number) -> number'
 caused by:
-  Return type is not compatible. Type 'string' could not be converted into 'number')");
+  Return type is not compatible. 
+Type 'string' could not be converted into 'number')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret_mult")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type A = (number, number) -> (number, string)
 type B = (number, number) -> (number, boolean)
@@ -1449,10 +1382,14 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        R"(Type '(number, number) -> (number, string)' could not be converted into '(number, number) -> (number, boolean)'
+    '(number, number) -> (number, string)'
+could not be converted into
+    '(number, number) -> (number, boolean)'
 caused by:
-  Return #2 type is not compatible. Type 'string' could not be converted into 'boolean')");
+  Return #2 type is not compatible. 
+Type 'string' could not be converted into 'boolean')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_quantify_right_type")
@@ -1561,6 +1498,9 @@ TEST_CASE_FIXTURE(Fixture, "inferred_higher_order_functions_are_quantified_at_th
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_non_self_unsealed_overwrite")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 local t = { f = nil :: ((x: number) -> number)? }
 
@@ -1575,11 +1515,19 @@ end
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(2, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(string) -> string' could not be converted into '((number) -> number)?'
+    CHECK_EQ(toString(result.errors[0]), R"(Type
+    '(string) -> string'
+could not be converted into
+    '((number) -> number)?'
 caused by:
-  None of the union options are compatible. For example: Type '(string) -> string' could not be converted into '(number) -> number'
+  None of the union options are compatible. For example: 
+Type
+    '(string) -> string'
+could not be converted into
+    '(number) -> number'
 caused by:
-  Argument #1 type is not compatible. Type 'number' could not be converted into 'string')");
+  Argument #1 type is not compatible. 
+Type 'number' could not be converted into 'string')");
     CHECK_EQ(toString(result.errors[1]), R"(Type 'string' could not be converted into 'number')");
 }
 
@@ -1595,6 +1543,9 @@ TEST_CASE_FIXTURE(Fixture, "strict_mode_ok_with_missing_arguments")
 
 TEST_CASE_FIXTURE(Fixture, "function_statement_sealed_table_assignment_through_indexer")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 local t: {[string]: () -> number} = {}
 
@@ -1603,7 +1554,10 @@ function t:b() return 2 end -- not OK
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(R"(Type '(*error-type*) -> number' could not be converted into '() -> number'
+    CHECK_EQ(R"(Type
+    '(*error-type*) -> number'
+could not be converted into
+    '() -> number'
 caused by:
   Argument count mismatch. Function expects 1 argument, but none are specified)",
         toString(result.errors[0]));
@@ -1800,6 +1754,9 @@ foo(string.find("hello", "e"))
 
 TEST_CASE_FIXTURE(Fixture, "luau_subtyping_is_np_hard")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 --!strict
 
@@ -1832,11 +1789,11 @@ z = y -- Not OK, so the line is colorable
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        "Type '((\"blue\" | \"red\") -> (\"blue\" | \"red\") -> (\"blue\" | \"red\") -> boolean) & ((\"blue\" | \"red\") -> (\"blue\") -> (\"blue\") "
+    '(("blue" | "red") -> ("blue" | "red") -> ("blue" | "red") -> boolean) & (("blue" | "red") -> ("blue") -> ("blue") -> false) & (("blue" | "red") -> ("red") -> ("red") -> false) & (("blue") -> ("blue") -> ("blue" | "red") -> false) & (("red") -> ("red") -> ("blue" | "red") -> false)'
-        "-> false) & ((\"blue\" | \"red\") -> (\"red\") -> (\"red\") -> false) & ((\"blue\") -> (\"blue\") -> (\"blue\" | \"red\") -> false) & "
+could not be converted into
-        "((\"red\") -> (\"red\") -> (\"blue\" | \"red\") -> false)' could not be converted into '(\"blue\" | \"red\") -> (\"blue\" | \"red\") -> "
+    '("blue" | "red") -> ("blue" | "red") -> ("blue" | "red") -> false'; none of the intersection parts are compatible)";
-        "(\"blue\" | \"red\") -> false'; none of the intersection parts are compatible");
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "function_is_supertype_of_concrete_functions")
@@ -1994,7 +1951,11 @@ TEST_CASE_FIXTURE(Fixture, "function_exprs_are_generalized_at_signature_scope_no
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "param_1_and_2_both_takes_the_same_generic_but_their_arguments_are_incompatible")
 {
-    ScopedFastFlag sff{"LuauAlwaysCommitInferencesOfFunctionCalls", true};
+    ScopedFastFlag sff[] = {
+        {"LuauIndentTypeMismatch", true},
+        {"LuauAlwaysCommitInferencesOfFunctionCalls", true},
+    };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
 
     CheckResult result = check(R"(
         local function foo<a>(x: a, y: a?)
@@ -2038,11 +1999,12 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "param_1_and_2_both_takes_the_same_generic_bu
 
     LUAU_REQUIRE_ERROR_COUNT(2, result);
 
-    CHECK_EQ(toString(result.errors[0]), R"(Type '{ x: number }' could not be converted into 'vec2?'
+    const std::string expected = R"(Type '{ x: number }' could not be converted into 'vec2?'
 caused by:
-  None of the union options are compatible. For example: Table type '{ x: number }' not compatible with type 'vec2' because the former is missing field 'y')");
+  None of the union options are compatible. For example: 
-
+Table type '{ x: number }' not compatible with type 'vec2' because the former is missing field 'y')";
-    CHECK_EQ(toString(result.errors[1]), "Type 'vec2' could not be converted into 'number'");
+    CHECK_EQ(expected, toString(result.errors[0]));
+    CHECK_EQ("Type 'vec2' could not be converted into 'number'", toString(result.errors[1]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "param_1_and_2_both_takes_the_same_generic_but_their_arguments_are_incompatible_2")

tests/TypeInfer.generics.test.cpp

@@ -713,6 +713,9 @@ end
 
 TEST_CASE_FIXTURE(Fixture, "generic_functions_should_be_memory_safe")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 --!strict
 -- At one point this produced a UAF
@@ -725,12 +728,14 @@ y.a.c = y
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type 'y' could not be converted into 'T<string>'
-        R"(Type 'y' could not be converted into 'T<string>'
 caused by:
-  Property 'a' is not compatible. Type '{ c: T<string>?, d: number }' could not be converted into 'U<string>'
+  Property 'a' is not compatible. 
+Type '{ c: T<string>?, d: number }' could not be converted into 'U<string>'
 caused by:
-  Property 'd' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property 'd' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "generic_type_pack_unification1")

tests/TypeInfer.intersectionTypes.test.cpp

@@ -317,6 +317,9 @@ TEST_CASE_FIXTURE(Fixture, "table_intersection_write_sealed")
 
 TEST_CASE_FIXTURE(Fixture, "table_intersection_write_sealed_indirect")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         type X = { x: (number) -> number }
         type Y = { y: (string) -> string }
@@ -333,9 +336,13 @@ TEST_CASE_FIXTURE(Fixture, "table_intersection_write_sealed_indirect")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(4, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(string, number) -> string' could not be converted into '(string) -> string'
+    const std::string expected = R"(Type
+    '(string, number) -> string'
+could not be converted into
+    '(string) -> string'
 caused by:
-  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)");
+  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)";
+    CHECK_EQ(expected, toString(result.errors[0]));
     CHECK_EQ(toString(result.errors[1]), "Cannot add property 'z' to table 'X & Y'");
     CHECK_EQ(toString(result.errors[2]), "Type 'number' could not be converted into 'string'");
     CHECK_EQ(toString(result.errors[3]), "Cannot add property 'w' to table 'X & Y'");
@@ -343,6 +350,9 @@ caused by:
 
 TEST_CASE_FIXTURE(Fixture, "table_write_sealed_indirect")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     // After normalization, previous 'table_intersection_write_sealed_indirect' is identical to this one
     CheckResult result = check(R"(
     type XY = { x: (number) -> number, y: (string) -> string }
@@ -357,9 +367,14 @@ TEST_CASE_FIXTURE(Fixture, "table_write_sealed_indirect")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(4, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '(string, number) -> string' could not be converted into '(string) -> string'
+    const std::string expected = R"(Type
+    '(string, number) -> string'
+could not be converted into
+    '(string) -> string'
 caused by:
-  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)");
+  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)";
+    CHECK_EQ(expected, toString(result.errors[0]));
+
     CHECK_EQ(toString(result.errors[1]), "Cannot add property 'z' to table 'XY'");
     CHECK_EQ(toString(result.errors[2]), "Type 'number' could not be converted into 'string'");
     CHECK_EQ(toString(result.errors[3]), "Cannot add property 'w' to table 'XY'");
@@ -377,6 +392,9 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "table_intersection_setmetatable")
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_intersection_part")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type X = { x: number }
 type Y = { y: number }
@@ -386,9 +404,11 @@ local a: XYZ = 3
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'number' could not be converted into 'X & Y & Z'
+    const std::string expected = R"(Type 'number' could not be converted into 'X & Y & Z'
 caused by:
-  Not all intersection parts are compatible. Type 'number' could not be converted into 'X')");
+  Not all intersection parts are compatible. 
+Type 'number' could not be converted into 'X')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_intersection_all")
@@ -462,6 +482,9 @@ TEST_CASE_FIXTURE(Fixture, "intersect_false_and_bool_and_false")
 
 TEST_CASE_FIXTURE(Fixture, "intersect_saturate_overloaded_functions")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : ((number?) -> number?) & ((string?) -> string?)
         local y : (nil) -> nil = x -- OK
@@ -469,12 +492,18 @@ TEST_CASE_FIXTURE(Fixture, "intersect_saturate_overloaded_functions")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number?) -> number?) & ((string?) -> string?)' could not be converted into '(number) -> number'; "
+    const std::string expected = R"(Type
-                                         "none of the intersection parts are compatible");
+    '((number?) -> number?) & ((string?) -> string?)'
+could not be converted into
+    '(number) -> number'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_saturate_overloaded_functions")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : ((number) -> number) & ((string) -> string)
         local y : ((number | string) -> (number | string)) = x -- OK
@@ -482,12 +511,18 @@ TEST_CASE_FIXTURE(Fixture, "union_saturate_overloaded_functions")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number) -> number) & ((string) -> string)' could not be converted into '(boolean | number) -> "
+    const std::string expected = R"(Type
-                                         "boolean | number'; none of the intersection parts are compatible");
+    '((number) -> number) & ((string) -> string)'
+could not be converted into
+    '(boolean | number) -> boolean | number'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "intersection_of_tables")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : { p : number?, q : string? } & { p : number?, q : number?, r : number? }
         local y : { p : number?, q : nil, r : number? } = x -- OK
@@ -495,12 +530,18 @@ TEST_CASE_FIXTURE(Fixture, "intersection_of_tables")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '{| p: number?, q: number?, r: number? |} & {| p: number?, q: string? |}' could not be converted into "
+    const std::string expected = R"(Type
-                                         "'{| p: nil |}'; none of the intersection parts are compatible");
+    '{| p: number?, q: number?, r: number? |} & {| p: number?, q: string? |}'
+could not be converted into
+    '{| p: nil |}'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "intersection_of_tables_with_top_properties")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : { p : number?, q : any } & { p : unknown, q : string? }
         local y : { p : number?, q : string? } = x -- OK
@@ -532,9 +573,11 @@ TEST_CASE_FIXTURE(Fixture, "intersection_of_tables_with_top_properties")
     else
     {
         LUAU_REQUIRE_ERROR_COUNT(1, result);
-        CHECK_EQ(toString(result.errors[0]),
+        const std::string expected = R"(Type
-            "Type '{| p: number?, q: any |} & {| p: unknown, q: string? |}' could not be converted into '{| p: string?, "
+    '{| p: number?, q: any |} & {| p: unknown, q: string? |}'
-            "q: number? |}'; none of the intersection parts are compatible");
+could not be converted into
+    '{| p: string?, q: number? |}'; none of the intersection parts are compatible)";
+        CHECK_EQ(expected, toString(result.errors[0]));
     }
 }
 
@@ -551,6 +594,9 @@ TEST_CASE_FIXTURE(Fixture, "intersection_of_tables_with_never_properties")
 
 TEST_CASE_FIXTURE(Fixture, "overloaded_functions_returning_intersections")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : ((number?) -> ({ p : number } & { q : number })) & ((string?) -> ({ p : number } & { r : number }))
         local y : (nil) -> { p : number, q : number, r : number} = x -- OK
@@ -558,13 +604,18 @@ TEST_CASE_FIXTURE(Fixture, "overloaded_functions_returning_intersections")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        "Type '((number?) -> {| p: number |} & {| q: number |}) & ((string?) -> {| p: number |} & {| r: number |})' could not be converted into "
+    '((number?) -> {| p: number |} & {| q: number |}) & ((string?) -> {| p: number |} & {| r: number |})'
-        "'(number?) -> {| p: number, q: number, r: number |}'; none of the intersection parts are compatible");
+could not be converted into
+    '(number?) -> {| p: number, q: number, r: number |}'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generic")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a>()
         local x : ((number?) -> (a | number)) & ((string?) -> (a | string))
@@ -574,12 +625,18 @@ TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generic")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number?) -> a | number) & ((string?) -> a | string)' could not be converted into '(number?) -> a'; "
+    const std::string expected = R"(Type
-                                         "none of the intersection parts are compatible");
+    '((number?) -> a | number) & ((string?) -> a | string)'
+could not be converted into
+    '(number?) -> a'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generics")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a,b,c>()
         local x : ((a?) -> (a | b)) & ((c?) -> (b | c))
@@ -589,12 +646,18 @@ TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generics")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        "Type '((a?) -> a | b) & ((c?) -> b | c)' could not be converted into '(a?) -> (a & c) | b'; none of the intersection parts are compatible");
+    '((a?) -> a | b) & ((c?) -> b | c)'
+could not be converted into
+    '(a?) -> (a & c) | b'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generic_packs")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...,b...>()
         local x : ((number?, a...) -> (number?, b...)) & ((string?, a...) -> (string?, b...))
@@ -604,12 +667,18 @@ TEST_CASE_FIXTURE(Fixture, "overloaded_functions_mentioning_generic_packs")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number?, a...) -> (number?, b...)) & ((string?, a...) -> (string?, b...))' could not be converted "
+    const std::string expected = R"(Type
-                                         "into '(nil, b...) -> (nil, a...)'; none of the intersection parts are compatible");
+    '((number?, a...) -> (number?, b...)) & ((string?, a...) -> (string?, b...))'
+could not be converted into
+    '(nil, b...) -> (nil, a...)'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_unknown_result")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...,b...>()
         local x : ((number) -> number) & ((nil) -> unknown)
@@ -619,12 +688,18 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_unknown_result")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((nil) -> unknown) & ((number) -> number)' could not be converted into '(number?) -> number?'; none "
+    const std::string expected = R"(Type
-                                         "of the intersection parts are compatible");
+    '((nil) -> unknown) & ((number) -> number)'
+could not be converted into
+    '(number?) -> number?'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_unknown_arguments")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...,b...>()
         local x : ((number) -> number?) & ((unknown) -> string?)
@@ -634,12 +709,18 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_unknown_arguments")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number) -> number?) & ((unknown) -> string?)' could not be converted into '(number?) -> nil'; none "
+    const std::string expected = R"(Type
-                                         "of the intersection parts are compatible");
+    '((number) -> number?) & ((unknown) -> string?)'
+could not be converted into
+    '(number?) -> nil'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_never_result")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...,b...>()
         local x : ((number) -> number) & ((nil) -> never)
@@ -649,12 +730,18 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_never_result")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((nil) -> never) & ((number) -> number)' could not be converted into '(number?) -> never'; none of "
+    const std::string expected = R"(Type
-                                         "the intersection parts are compatible");
+    '((nil) -> never) & ((number) -> number)'
+could not be converted into
+    '(number?) -> never'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_never_arguments")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...,b...>()
         local x : ((number) -> number?) & ((never) -> string?)
@@ -664,12 +751,18 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_never_arguments")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((never) -> string?) & ((number) -> number?)' could not be converted into '(number?) -> nil'; none "
+    const std::string expected = R"(Type
-                                         "of the intersection parts are compatible");
+    '((never) -> string?) & ((number) -> number?)'
+could not be converted into
+    '(number?) -> nil'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_overlapping_results_and_variadics")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : ((string?) -> (string | number)) & ((number?) -> ...number)
         local y : ((nil) -> (number, number?)) = x -- OK
@@ -677,8 +770,11 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_overlapping_results_and_
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((number?) -> (...number)) & ((string?) -> number | string)' could not be converted into '(number | "
+    const std::string expected = R"(Type
-                                         "string) -> (number, number?)'; none of the intersection parts are compatible");
+    '((number?) -> (...number)) & ((string?) -> number | string)'
+could not be converted into
+    '(number | string) -> (number, number?)'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_1")
@@ -713,6 +809,9 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_2")
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_3")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...>()
         local x : (() -> a...) & (() -> (number?,a...))
@@ -722,12 +821,18 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_3")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        "Type '(() -> (a...)) & (() -> (number?, a...))' could not be converted into '() -> number'; none of the intersection parts are compatible");
+    '(() -> (a...)) & (() -> (number?, a...))'
+could not be converted into
+    '() -> number'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_4")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
       function f<a...>()
         local x : ((a...) -> ()) & ((number,a...) -> number)
@@ -737,8 +842,11 @@ TEST_CASE_FIXTURE(Fixture, "overloadeded_functions_with_weird_typepacks_4")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((a...) -> ()) & ((number, a...) -> number)' could not be converted into '(number?) -> ()'; none of "
+    const std::string expected = R"(Type
-                                         "the intersection parts are compatible");
+    '((a...) -> ()) & ((number, a...) -> number)'
+could not be converted into
+    '(number?) -> ()'; none of the intersection parts are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "intersect_metatables")
@@ -897,8 +1005,6 @@ local y = x.Bar
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "index_property_table_intersection_2")
 {
-    ScopedFastFlag sff{"LuauIndexTableIntersectionStringExpr", true};
-
     CheckResult result = check(R"(
 type Foo = {
 	Bar: string,

tests/TypeInfer.modules.test.cpp

@@ -389,6 +389,9 @@ type Table = typeof(tbl)
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "module_type_conflict")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     fileResolver.source["game/A"] = R"(
 export type T = { x: number }
 return {}
@@ -407,15 +410,19 @@ local b: B.T = a
     )";
 
     CheckResult result = frontend.check("game/C");
-    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    const std::string expected = R"(Type 'T' from 'game/A' could not be converted into 'T' from 'game/B'
-
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'T' from 'game/A' could not be converted into 'T' from 'game/B'
 caused by:
-  Property 'x' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property 'x' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "module_type_conflict_instantiated")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     fileResolver.source["game/A"] = R"(
 export type Wrap<T> = { x: T }
 return {}
@@ -441,11 +448,12 @@ local b: B.T = a
     )";
 
     CheckResult result = frontend.check("game/D");
-    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    const std::string expected = R"(Type 'T' from 'game/B' could not be converted into 'T' from 'game/C'
-
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'T' from 'game/B' could not be converted into 'T' from 'game/C'
 caused by:
-  Property 'x' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property 'x' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "constrained_anyification_clone_immutable_types")

tests/TypeInfer.oop.test.cpp

@@ -9,6 +9,7 @@
 
 #include "Fixture.h"
 
+#include "ScopedFlags.h"
 #include "doctest.h"
 
 using namespace Luau;
@@ -404,4 +405,92 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "cycle_between_object_constructor_and_alias")
     CHECK_MESSAGE(get<MetatableType>(follow(aliasType)), "Expected metatable type but got: " << toString(aliasType));
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "promise_type_error_too_complex")
+{
+    ScopedFastFlag sff{"LuauStacklessTypeClone", true};
+
+    frontend.options.retainFullTypeGraphs = false;
+
+    // Used `luau-reduce` tool to extract a minimal reproduction.
+    // Credit: https://github.com/evaera/roblox-lua-promise/blob/v4.0.0/lib/init.lua
+    CheckResult result = check(R"(
+        --!strict
+
+        local Promise = {}
+        Promise.prototype = {}
+        Promise.__index = Promise.prototype
+
+        function Promise._new(traceback, callback, parent)
+            if parent ~= nil and not Promise.is(parent)then
+            end
+
+            local self = {
+                _parent = parent,
+            }
+
+            parent._consumers[self] = true
+            setmetatable(self, Promise)
+            self:_reject()
+
+            return self
+        end
+
+        function Promise.resolve(...)
+            return Promise._new(debug.traceback(nil, 2), function(resolve)
+            end)
+        end
+
+        function Promise.reject(...)
+            return Promise._new(debug.traceback(nil, 2), function(_, reject)
+            end)
+        end
+
+        function Promise._try(traceback, callback, ...)
+            return Promise._new(traceback, function(resolve)
+            end)
+        end
+
+        function Promise.try(callback, ...)
+            return Promise._try(debug.traceback(nil, 2), callback, ...)
+        end
+
+        function Promise._all(traceback, promises, amount)
+            if #promises == 0 or amount == 0 then
+                return Promise.resolve({})
+            end
+            return Promise._new(traceback, function(resolve, reject, onCancel)
+            end)
+        end
+
+        function Promise.all(promises)
+            return Promise._all(debug.traceback(nil, 2), promises)
+        end
+
+        function Promise.allSettled(promises)
+            return Promise.resolve({})
+        end
+
+        function Promise.race(promises)
+            return Promise._new(debug.traceback(nil, 2), function(resolve, reject, onCancel)
+            end)
+        end
+
+        function Promise.each(list, predicate)
+            return Promise._new(debug.traceback(nil, 2), function(resolve, reject, onCancel)
+                local predicatePromise = Promise.resolve(predicate(value, index))
+                local success, result = predicatePromise:await()
+            end)
+        end
+
+        function Promise.is(object)
+        end
+
+        function Promise.prototype:_reject(...)
+            self:_finalize()
+        end
+    )");
+
+    LUAU_REQUIRE_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.provisional.test.cpp

@@ -787,6 +787,9 @@ TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_with_mismatching_arity_but_any_is
 
 TEST_CASE_FIXTURE(Fixture, "assign_table_with_refined_property_with_a_similar_type_is_illegal")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local t: {x: number?} = {x = nil}
 
@@ -796,11 +799,14 @@ TEST_CASE_FIXTURE(Fixture, "assign_table_with_refined_property_with_a_similar_ty
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-
+    const std::string expected = R"(Type
-    CHECK_EQ(R"(Type '{| x: number? |}' could not be converted into '{| x: number |}'
+    '{| x: number? |}'
+could not be converted into
+    '{| x: number |}'
 caused by:
-  Property 'x' is not compatible. Type 'number?' could not be converted into 'number' in an invariant context)",
+  Property 'x' is not compatible. 
-        toString(result.errors[0]));
+Type 'number?' could not be converted into 'number' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_with_a_singleton_argument")

tests/TypeInfer.singletons.test.cpp

@@ -316,6 +316,9 @@ TEST_CASE_FIXTURE(Fixture, "table_properties_type_error_escapes")
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_tagged_union_mismatch_string")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type Cat = { tag: 'cat', catfood: string }
 type Dog = { tag: 'dog', dogfood: string }
@@ -325,14 +328,18 @@ local a: Animal = { tag = 'cat', cafood = 'something' }
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(R"(Type 'a' could not be converted into 'Cat | Dog'
+    const std::string expected = R"(Type 'a' could not be converted into 'Cat | Dog'
 caused by:
-  None of the union options are compatible. For example: Table type 'a' not compatible with type 'Cat' because the former is missing field 'catfood')",
+  None of the union options are compatible. For example: 
-        toString(result.errors[0]));
+Table type 'a' not compatible with type 'Cat' because the former is missing field 'catfood')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_tagged_union_mismatch_bool")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 type Good = { success: true, result: string }
 type Bad = { success: false, error: string }
@@ -342,18 +349,20 @@ local a: Result = { success = false, result = 'something' }
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(R"(Type 'a' could not be converted into 'Bad | Good'
+    const std::string expected = R"(Type 'a' could not be converted into 'Bad | Good'
 caused by:
-  None of the union options are compatible. For example: Table type 'a' not compatible with type 'Bad' because the former is missing field 'error')",
+  None of the union options are compatible. For example: 
-        toString(result.errors[0]));
+Table type 'a' not compatible with type 'Bad' because the former is missing field 'error')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "parametric_tagged_union_alias")
 {
     ScopedFastFlag sff[] = {
         {"DebugLuauDeferredConstraintResolution", true},
+        {"LuauIndentTypeMismatch", true},
     };
-
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
         type Ok<T> = {success: true, result: T}
         type Err<T> = {success: false, error: T}
@@ -365,10 +374,10 @@ TEST_CASE_FIXTURE(Fixture, "parametric_tagged_union_alias")
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
-    const std::string expectedError = "Type 'a' could not be converted into 'Err<number> | Ok<string>'\n"
+    const std::string expectedError = R"(Type 'a' could not be converted into 'Err<number> | Ok<string>'
-                                      "caused by:\n"
+caused by:
-                                      "  None of the union options are compatible. For example: Table type 'a'"
+  None of the union options are compatible. For example: 
-                                      " not compatible with type 'Err<number>' because the former is missing field 'error'";
+Table type 'a' not compatible with type 'Err<number>' because the former is missing field 'error')";
 
     CHECK(toString(result.errors[0]) == expectedError);
 }

tests/TypeInfer.tables.test.cpp

@@ -2083,6 +2083,8 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_should_cope_with_optional_prope
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_prop")
 {
+    ScopedFastFlag sff[] = {{"LuauIndentTypeMismatch", true}};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
     CheckResult result = check(R"(
 type A = { x: number, y: number }
 type B = { x: number, y: string }
@@ -2092,13 +2094,17 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'A' could not be converted into 'B'
+    const std::string expected = R"(Type 'A' could not be converted into 'B'
 caused by:
-  Property 'y' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property 'y' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_prop_nested")
 {
+    ScopedFastFlag sff[] = {{"LuauIndentTypeMismatch", true}};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
     CheckResult result = check(R"(
 type AS = { x: number, y: number }
 type BS = { x: number, y: string }
@@ -2111,15 +2117,21 @@ local b: B = a
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'A' could not be converted into 'B'
+    const std::string expected = R"(Type 'A' could not be converted into 'B'
 caused by:
-  Property 'b' is not compatible. Type 'AS' could not be converted into 'BS'
+  Property 'b' is not compatible. 
+Type 'AS' could not be converted into 'BS'
 caused by:
-  Property 'y' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property 'y' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "error_detailed_metatable_prop")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 local a1 = setmetatable({ x = 2, y = 3 }, { __call = function(s) end });
 local b1 = setmetatable({ x = 2, y = "hello" }, { __call = function(s) end });
@@ -2130,33 +2142,68 @@ local b2 = setmetatable({ x = 2, y = 4 }, { __call = function(s, t) end });
 local c2: typeof(a2) = b2
     )");
 
-    LUAU_REQUIRE_ERROR_COUNT(2, result);
+    const std::string expected1 = R"(Type 'b1' could not be converted into 'a1'
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'b1' could not be converted into 'a1'
 caused by:
-  Type '{ x: number, y: string }' could not be converted into '{ x: number, y: number }'
+  Type
+    '{ x: number, y: string }'
+could not be converted into
+    '{ x: number, y: number }'
 caused by:
-  Property 'y' is not compatible. Type 'string' could not be converted into 'number' in an invariant context)");
+  Property 'y' is not compatible. 
+Type 'string' could not be converted into 'number' in an invariant context)";
+    const std::string expected2 = R"(Type 'b2' could not be converted into 'a2'
+caused by:
+  Type
+    '{ __call: <a, b>(a, b) -> () }'
+could not be converted into
+    '{ __call: <a>(a) -> () }'
+caused by:
+  Property '__call' is not compatible. 
+Type
+    '<a, b>(a, b) -> ()'
+could not be converted into
+    '<a>(a) -> ()'; different number of generic type parameters)";
+    const std::string expected3 = R"(Type 'b2' could not be converted into 'a2'
+caused by:
+  Type
+    '{ __call: <a, b>(a, b) -> () }'
+could not be converted into
+    '{ __call: <a>(a) -> () }'
+caused by:
+  Property '__call' is not compatible. 
+Type
+    '<a, b>(a, b) -> ()'
+could not be converted into
+    '<a>(a) -> ()'; different number of generic type parameters)";
 
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+    CHECK_EQ(expected1, toString(result.errors[0]));
     if (FFlag::LuauInstantiateInSubtyping)
     {
-        CHECK_EQ(toString(result.errors[1]), R"(Type 'b2' could not be converted into 'a2'
+        CHECK_EQ(expected2, toString(result.errors[1]));
-caused by:
-  Type '{ __call: <a, b>(a, b) -> () }' could not be converted into '{ __call: <a>(a) -> () }'
-caused by:
-  Property '__call' is not compatible. Type '<a, b>(a, b) -> ()' could not be converted into '<a>(a) -> ()'; different number of generic type parameters)");
     }
     else
     {
-        CHECK_EQ(toString(result.errors[1]), R"(Type 'b2' could not be converted into 'a2'
+        std::string expected3 = R"(Type 'b2' could not be converted into 'a2'
 caused by:
-  Type '{ __call: (a, b) -> () }' could not be converted into '{ __call: <a>(a) -> () }'
+  Type
+    '{ __call: (a, b) -> () }'
+could not be converted into
+    '{ __call: <a>(a) -> () }'
 caused by:
-  Property '__call' is not compatible. Type '(a, b) -> ()' could not be converted into '<a>(a) -> ()'; different number of generic type parameters)");
+  Property '__call' is not compatible. 
+Type
+    '(a, b) -> ()'
+could not be converted into
+    '<a>(a) -> ()'; different number of generic type parameters)";
+        CHECK_EQ(expected3, toString(result.errors[1]));
     }
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_indexer_key")
 {
+    ScopedFastFlag sff[] = {{"LuauIndentTypeMismatch", true}};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
     CheckResult result = check(R"(
         type A = { [number]: string }
         type B = { [string]: string }
@@ -2166,13 +2213,17 @@ TEST_CASE_FIXTURE(Fixture, "error_detailed_indexer_key")
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'A' could not be converted into 'B'
+    const std::string expected = R"(Type 'A' could not be converted into 'B'
 caused by:
-  Property '[indexer key]' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property '[indexer key]' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_indexer_value")
 {
+    ScopedFastFlag sff[] = {{"LuauIndentTypeMismatch", true}};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
     CheckResult result = check(R"(
         type A = { [number]: number }
         type B = { [number]: string }
@@ -2182,9 +2233,11 @@ TEST_CASE_FIXTURE(Fixture, "error_detailed_indexer_value")
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'A' could not be converted into 'B'
+    const std::string expected = R"(Type 'A' could not be converted into 'B'
 caused by:
-  Property '[indexer value]' is not compatible. Type 'number' could not be converted into 'string' in an invariant context)");
+  Property '[indexer value]' is not compatible. 
+Type 'number' could not be converted into 'string' in an invariant context)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "explicitly_typed_table")
@@ -2204,6 +2257,8 @@ a.p = { x = 9 }
 
 TEST_CASE_FIXTURE(Fixture, "explicitly_typed_table_error")
 {
+    ScopedFastFlag sff[] = {{"LuauIndentTypeMismatch", true}};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
     CheckResult result = check(R"(
 --!strict
 type Super = { x : number }
@@ -2218,9 +2273,11 @@ local y: number = tmp.p.y
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'tmp' could not be converted into 'HasSuper'
+    const std::string expected = R"(Type 'tmp' could not be converted into 'HasSuper'
 caused by:
-  Property 'p' is not compatible. Table type '{ x: number, y: number }' not compatible with type 'Super' because the former has extra field 'y')");
+  Property 'p' is not compatible. 
+Table type '{ x: number, y: number }' not compatible with type 'Super' because the former has extra field 'y')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "explicitly_typed_table_with_indexer")
@@ -3302,7 +3359,13 @@ TEST_CASE_FIXTURE(Fixture, "scalar_is_a_subtype_of_a_compatible_polymorphic_shap
 
 TEST_CASE_FIXTURE(Fixture, "scalar_is_not_a_subtype_of_a_compatible_polymorphic_shape_type")
 {
-    ScopedFastFlag sff{"LuauAlwaysCommitInferencesOfFunctionCalls", true};
+    ScopedFastInt sfi[] = {{"LuauIndentTypeMismatchMaxTypeLength", 10}};
+    ScopedFastFlag sff[] = {
+        {"LuauAlwaysCommitInferencesOfFunctionCalls", true},
+        {"LuauIndentTypeMismatch", true},
+    };
+
+
 
     CheckResult result = check(R"(
         local function f(s)
@@ -3316,22 +3379,32 @@ TEST_CASE_FIXTURE(Fixture, "scalar_is_not_a_subtype_of_a_compatible_polymorphic_
 
     LUAU_REQUIRE_ERROR_COUNT(3, result);
 
-    CHECK_EQ(R"(Type 'string' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
+    const std::string expected1 =
+        R"(Type 'string' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
 caused by:
-  The former's metatable does not satisfy the requirements. Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')",
+  The former's metatable does not satisfy the requirements. 
-        toString(result.errors[0]));
+Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')";
+    CHECK_EQ(expected1, toString(result.errors[0]));
 
-    CHECK_EQ(R"(Type '"bar"' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
-caused by:
-  The former's metatable does not satisfy the requirements. Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')",
-        toString(result.errors[1]));
 
-    CHECK_EQ(R"(Type '"bar" | "baz"' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
+    const std::string expected2 =
+        R"(Type '"bar"' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
 caused by:
-  Not all union options are compatible. Type '"bar"' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
+  The former's metatable does not satisfy the requirements. 
+Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')";
+    CHECK_EQ(expected2, toString(result.errors[1]));
+
+    const std::string expected3 = R"(Type
+    '"bar" | "baz"'
+could not be converted into
+    't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
 caused by:
-  The former's metatable does not satisfy the requirements. Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')",
+  Not all union options are compatible. 
-        toString(result.errors[2]));
+Type '"bar"' could not be converted into 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}'
+caused by:
+  The former's metatable does not satisfy the requirements. 
+Table type 'typeof(string)' not compatible with type 't1 where t1 = {- absolutely_no_scalar_has_this_method: (t1) -> (a...) -}' because the former is missing field 'absolutely_no_scalar_has_this_method')";
+    CHECK_EQ(expected3, toString(result.errors[2]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "a_free_shape_can_turn_into_a_scalar_if_it_is_compatible")
@@ -3349,6 +3422,9 @@ TEST_CASE_FIXTURE(Fixture, "a_free_shape_can_turn_into_a_scalar_if_it_is_compati
 
 TEST_CASE_FIXTURE(Fixture, "a_free_shape_cannot_turn_into_a_scalar_if_it_is_not_compatible")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local function f(s): string
             local foo = s:absolutely_no_scalar_has_this_method()
@@ -3356,11 +3432,13 @@ TEST_CASE_FIXTURE(Fixture, "a_free_shape_cannot_turn_into_a_scalar_if_it_is_not_
         end
     )");
 
-    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    const std::string expected =
-    CHECK_EQ(R"(Type 't1 where t1 = {+ absolutely_no_scalar_has_this_method: (t1) -> (a, b...) +}' could not be converted into 'string'
+        R"(Type 't1 where t1 = {+ absolutely_no_scalar_has_this_method: (t1) -> (a, b...) +}' could not be converted into 'string'
 caused by:
-  The former's metatable does not satisfy the requirements. Table type 'typeof(string)' not compatible with type 't1 where t1 = {+ absolutely_no_scalar_has_this_method: (t1) -> (a, b...) +}' because the former is missing field 'absolutely_no_scalar_has_this_method')",
+  The former's metatable does not satisfy the requirements. 
-        toString(result.errors[0]));
+Table type 'typeof(string)' not compatible with type 't1 where t1 = {+ absolutely_no_scalar_has_this_method: (t1) -> (a, b...) +}' because the former is missing field 'absolutely_no_scalar_has_this_method')";
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(expected, toString(result.errors[0]));
     CHECK_EQ("<a, b...>(t1) -> string where t1 = {+ absolutely_no_scalar_has_this_method: (t1) -> (a, b...) +}", toString(requireType("f")));
 }
 

tests/TypeInfer.test.cpp

@@ -992,6 +992,9 @@ end
 
 TEST_CASE_FIXTURE(Fixture, "cli_50041_committing_txnlog_in_apollo_client_error")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         --!strict
         --!nolint
@@ -1028,16 +1031,23 @@ TEST_CASE_FIXTURE(Fixture, "cli_50041_committing_txnlog_in_apollo_client_error")
         // unsound.
 
         LUAU_REQUIRE_ERROR_COUNT(1, result);
-
+        const std::string expected = R"(Type 'Policies' from 'MainModule' could not be converted into 'Policies' from 'MainModule'
-        CHECK_EQ(
-            R"(Type 'Policies' from 'MainModule' could not be converted into 'Policies' from 'MainModule'
 caused by:
-  Property 'getStoreFieldName' is not compatible. Type '(Policies, FieldSpecifier & {| from: number? |}) -> (a, b...)' could not be converted into '(Policies, FieldSpecifier) -> string'
+  Property 'getStoreFieldName' is not compatible. 
+Type
+    '(Policies, FieldSpecifier & {| from: number? |}) -> (a, b...)'
+could not be converted into
+    '(Policies, FieldSpecifier) -> string'
 caused by:
-  Argument #2 type is not compatible. Type 'FieldSpecifier' could not be converted into 'FieldSpecifier & {| from: number? |}'
+  Argument #2 type is not compatible. 
+Type
+    'FieldSpecifier'
+could not be converted into
+    'FieldSpecifier & {| from: number? |}'
 caused by:
-  Not all intersection parts are compatible. Table type 'FieldSpecifier' not compatible with type '{| from: number? |}' because the former has extra field 'fieldName')",
+  Not all intersection parts are compatible. 
-            toString(result.errors[0]));
+Table type 'FieldSpecifier' not compatible with type '{| from: number? |}' because the former has extra field 'fieldName')";
+        CHECK_EQ(expected, toString(result.errors[0]));
     }
     else
     {
@@ -1205,8 +1215,6 @@ end
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "typechecking_in_type_guards")
 {
-    ScopedFastFlag sff{"LuauTypecheckTypeguards", true};
-
     CheckResult result = check(R"(
 local a = type(foo) == 'nil'
 local b = typeof(foo) ~= 'nil'

tests/TypeInfer.tryUnify.test.cpp

@@ -345,7 +345,9 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "metatables_unify_against_shape_of_free_table
 {
     ScopedFastFlag sff[] = {
         {"LuauTransitiveSubtyping", true},
+        {"LuauIndentTypeMismatch", true},
     };
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
 
     TableType::Props freeProps{
         {"foo", {builtinTypes->numberType}},
@@ -373,11 +375,13 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "metatables_unify_against_shape_of_free_table
     state.log.commit();
 
     REQUIRE_EQ(state.errors.size(), 1);
-
+    const std::string expected = R"(Type
-    std::string expected = "Type '{ @metatable {| __index: {| foo: string |} |}, {  } }' could not be converted into '{- foo: number -}'\n"
+    '{ @metatable {| __index: {| foo: string |} |}, {  } }'
-                           "caused by:\n"
+could not be converted into
-                           "  Type 'number' could not be converted into 'string'";
+    '{- foo: number -}'
-    CHECK_EQ(toString(state.errors[0]), expected);
+caused by:
+  Type 'number' could not be converted into 'string')";
+    CHECK_EQ(expected, toString(state.errors[0]));
 }
 
 TEST_CASE_FIXTURE(TryUnifyFixture, "fuzz_tail_unification_issue")

tests/TypeInfer.typePacks.cpp

@@ -872,6 +872,9 @@ type R = { m: F<R> }
 
 TEST_CASE_FIXTURE(Fixture, "pack_tail_unification_check")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
 local a: () -> (number, ...string)
 local b: () -> (number, ...boolean)
@@ -879,9 +882,13 @@ a = b
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type '() -> (number, ...boolean)' could not be converted into '() -> (number, ...string)'
+    const std::string expected = R"(Type
+    '() -> (number, ...boolean)'
+could not be converted into
+    '() -> (number, ...string)'
 caused by:
-  Type 'boolean' could not be converted into 'string')");
+  Type 'boolean' could not be converted into 'string')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 // TODO: File a Jira about this

tests/TypeInfer.unionTypes.test.cpp

@@ -459,6 +459,8 @@ local oh : boolean = t.y
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_union_part")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
 type X = { x: number }
 type Y = { y: number }
@@ -471,9 +473,11 @@ local b: { w: number } = a
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'X | Y | Z' could not be converted into '{| w: number |}'
+    const std::string expected = R"(Type 'X | Y | Z' could not be converted into '{| w: number |}'
 caused by:
-  Not all union options are compatible. Table type 'X' not compatible with type '{| w: number |}' because the former is missing field 'w')");
+  Not all union options are compatible. 
+Table type 'X' not compatible with type '{| w: number |}' because the former is missing field 'w')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_union_all")
@@ -494,6 +498,8 @@ local a: XYZ = { w = 4 }
 
 TEST_CASE_FIXTURE(Fixture, "error_detailed_optional")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
 type X = { x: number }
 
@@ -501,9 +507,11 @@ local a: X? = { w = 4 }
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), R"(Type 'a' could not be converted into 'X?'
+    const std::string expected = R"(Type 'a' could not be converted into 'X?'
 caused by:
-  None of the union options are compatible. For example: Table type 'a' not compatible with type 'X' because the former is missing field 'x')");
+  None of the union options are compatible. For example: 
+Table type 'a' not compatible with type 'X' because the former is missing field 'x')";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 // We had a bug where a cyclic union caused a stack overflow.
@@ -524,6 +532,9 @@ TEST_CASE_FIXTURE(Fixture, "dont_allow_cyclic_unions_to_be_inferred")
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "table_union_write_indirect")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         type A = { x: number, y: (number) -> string } | { z: number, y: (number) -> string }
 
@@ -540,8 +551,11 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "table_union_write_indirect")
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
     // NOTE: union normalization will improve this message
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        R"(Type '(string) -> number' could not be converted into '((number) -> string) | ((number) -> string)'; none of the union options are compatible)");
+    '(string) -> number'
+could not be converted into
+    '((number) -> string) | ((number) -> string)'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_true_and_false")
@@ -606,6 +620,8 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_mentioning_generics")
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_mentioning_generic_typepacks")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
       function f<a...>()
         local x : (number, a...) -> (number?, a...)
@@ -615,12 +631,17 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_mentioning_generic_typepacks")
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '(number, a...) -> (number?, a...)' could not be converted into '((number) -> number) | ((number?, "
+    const std::string expected = R"(Type
-                                         "a...) -> (number?, a...))'; none of the union options are compatible");
+    '(number, a...) -> (number?, a...)'
+could not be converted into
+    '((number) -> number) | ((number?, a...) -> (number?, a...))'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_arg_arities")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
     CheckResult result = check(R"(
         local x : (number) -> number?
         local y : ((number?) -> number) | ((number | string) -> nil) = x -- OK
@@ -628,12 +649,18 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_arg_arities")
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '(number) -> number?' could not be converted into '((number) -> nil) | ((number, string?) -> "
+    const std::string expected = R"(Type
-                                         "number)'; none of the union options are compatible");
+    '(number) -> number?'
+could not be converted into
+    '((number) -> nil) | ((number, string?) -> number)'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_result_arities")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : () -> (number | string)
         local y : (() -> number) | (() -> string) = x -- OK
@@ -641,12 +668,18 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_result_arities")
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '() -> number | string' could not be converted into '(() -> (string, string)) | (() -> number)'; none "
+    const std::string expected = R"(Type
-                                         "of the union options are compatible");
+    '() -> number | string'
+could not be converted into
+    '(() -> (string, string)) | (() -> number)'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_variadics")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : (...nil) -> (...number?)
         local y : ((...string?) -> (...number)) | ((...number?) -> nil) = x -- OK
@@ -654,12 +687,18 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_variadics")
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '(...nil) -> (...number?)' could not be converted into '((...string?) -> (...number)) | ((...string?) "
+    const std::string expected = R"(Type
-                                         "-> nil)'; none of the union options are compatible");
+    '(...nil) -> (...number?)'
+could not be converted into
+    '((...string?) -> (...number)) | ((...string?) -> nil)'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_arg_variadics")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : (number) -> ()
         local y : ((number?) -> ()) | ((...number) -> ()) = x -- OK
@@ -667,12 +706,18 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_arg_variadics")
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]),
+    const std::string expected = R"(Type
-        "Type '(number) -> ()' could not be converted into '((...number?) -> ()) | ((number?) -> ())'; none of the union options are compatible");
+    '(number) -> ()'
+could not be converted into
+    '((...number?) -> ()) | ((number?) -> ())'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_result_variadics")
 {
+    ScopedFastFlag sff{"LuauIndentTypeMismatch", true};
+    ScopedFastInt sfi{"LuauIndentTypeMismatchMaxTypeLength", 10};
+
     CheckResult result = check(R"(
         local x : () -> (number?, ...number)
         local y : (() -> (...number)) | (() -> nil) = x -- OK
@@ -680,8 +725,11 @@ TEST_CASE_FIXTURE(Fixture, "union_of_functions_with_mismatching_result_variadics
      )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '() -> (number?, ...number)' could not be converted into '(() -> (...number)) | (() -> number)'; none "
+    const std::string expected = R"(Type
-                                         "of the union options are compatible");
+    '() -> (number?, ...number)'
+could not be converted into
+    '(() -> (...number)) | (() -> number)'; none of the union options are compatible)";
+    CHECK_EQ(expected, toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "less_greedy_unification_with_union_types")

tests/conformance/native.lua

@@ -14,6 +14,17 @@ assert((function(x, y)
   return c, b, t, t1, t2
 end)(5, 10) == 50)
 
+assert((function(x)
+  local oops -- split to prevent inlining
+  function oops()
+  end
+
+  -- x is checked to be a number here; we can not execute a reentry from oops() because optimizer assumes this holds until return
+  local y = math.abs(x)
+  oops()
+  return y * x
+end)("42") == 1764)
+
 local function fuzzfail1(...)
   repeat
     _ = nil

tests/conformance/native_types.lua

@@ -68,5 +68,16 @@ ecall(checkuserdata, 2)
 call(checkvector, vector(1, 2, 3))
 ecall(checkvector, 2)
 
+local function mutation_causes_bad_exit(a: number, count: number, sum: number)
+  repeat
+    a = 's'
+    sum += count
+    pcall(function() end)
+    count -= 1
+  until count == 0
+  return sum
+end
+
+assert(call(mutation_causes_bad_exit, 5, 10, 0) == 55)
 
 return('OK')

tests/main.cpp

@@ -161,8 +161,10 @@ struct BoostLikeReporter : doctest::IReporter
     }
 
     void log_message(const doctest::MessageData& md) override
-    { //
+    {
-        printf("%s(%d): ERROR: %s\n", md.m_file, md.m_line, md.m_string.c_str());
+        const char* severity = (md.m_severity & doctest::assertType::is_warn) ? "WARNING" : "ERROR";
+
+        printf("%s(%d): %s: %s\n", md.m_file, md.m_line, severity, md.m_string.c_str());
     }
 
     // called when a test case is skipped either because it doesn't pass the filters, has a skip decorator