Sync to upstream/release/552 (#735)

* Reduce the stack utilization of type checking.
* Improve the error message that's reported when a delimiting comma is
missing from a table literal. eg
```lua
local t = {
    first = 1
    second = 2
}```

Analysis/include/Luau/Connective.h

@@ -0,0 +1,68 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Def.h"
+#include "Luau/TypedAllocator.h"
+#include "Luau/TypeVar.h"
+#include "Luau/Variant.h"
+
+#include <memory>
+
+namespace Luau
+{
+
+struct Negation;
+struct Conjunction;
+struct Disjunction;
+struct Equivalence;
+struct Proposition;
+using Connective = Variant<Negation, Conjunction, Disjunction, Equivalence, Proposition>;
+using ConnectiveId = Connective*; // Can and most likely is nullptr.
+
+struct Negation
+{
+    ConnectiveId connective;
+};
+
+struct Conjunction
+{
+    ConnectiveId lhs;
+    ConnectiveId rhs;
+};
+
+struct Disjunction
+{
+    ConnectiveId lhs;
+    ConnectiveId rhs;
+};
+
+struct Equivalence
+{
+    ConnectiveId lhs;
+    ConnectiveId rhs;
+};
+
+struct Proposition
+{
+    DefId def;
+    TypeId discriminantTy;
+};
+
+template<typename T>
+const T* get(ConnectiveId connective)
+{
+    return get_if<T>(connective);
+}
+
+struct ConnectiveArena
+{
+    TypedAllocator<Connective> allocator;
+
+    ConnectiveId negation(ConnectiveId connective);
+    ConnectiveId conjunction(ConnectiveId lhs, ConnectiveId rhs);
+    ConnectiveId disjunction(ConnectiveId lhs, ConnectiveId rhs);
+    ConnectiveId equivalence(ConnectiveId lhs, ConnectiveId rhs);
+    ConnectiveId proposition(DefId def, TypeId discriminantTy);
+};
+
+} // namespace Luau

Analysis/include/Luau/Constraint.h

@@ -132,15 +132,16 @@ struct HasPropConstraint
     std::string prop;
 };
 
-struct RefinementConstraint
+// result ~ if isSingleton D then ~D else unknown where D = discriminantType
+struct SingletonOrTopTypeConstraint
 {
-    DefId def;
+    TypeId resultType;
     TypeId discriminantType;
 };
 
 using ConstraintV = Variant<SubtypeConstraint, PackSubtypeConstraint, GeneralizationConstraint, InstantiationConstraint, UnaryConstraint,
     BinaryConstraint, IterableConstraint, NameConstraint, TypeAliasExpansionConstraint, FunctionCallConstraint, PrimitiveTypeConstraint,
-    HasPropConstraint, RefinementConstraint>;
+    HasPropConstraint, SingletonOrTopTypeConstraint>;
 
 struct Constraint
 {

Analysis/include/Luau/ConstraintGraphBuilder.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "Luau/Ast.h"
+#include "Luau/Connective.h"
 #include "Luau/Constraint.h"
 #include "Luau/DataFlowGraphBuilder.h"
 #include "Luau/Module.h"
@@ -26,11 +27,13 @@ struct DcrLogger;
 struct Inference
 {
     TypeId ty = nullptr;
+    ConnectiveId connective = nullptr;
 
     Inference() = default;
 
-    explicit Inference(TypeId ty)
+    explicit Inference(TypeId ty, ConnectiveId connective = nullptr)
         : ty(ty)
+        , connective(connective)
     {
     }
 };
@@ -38,11 +41,13 @@ struct Inference
 struct InferencePack
 {
     TypePackId tp = nullptr;
+    std::vector<ConnectiveId> connectives;
 
     InferencePack() = default;
 
-    explicit InferencePack(TypePackId tp)
+    explicit InferencePack(TypePackId tp, const std::vector<ConnectiveId>& connectives = {})
         : tp(tp)
+        , connectives(connectives)
     {
     }
 };
@@ -73,6 +78,7 @@ struct ConstraintGraphBuilder
     // Defining scopes for AST nodes.
     DenseHashMap<const AstStatTypeAlias*, ScopePtr> astTypeAliasDefiningScopes{nullptr};
     NotNull<const DataFlowGraph> dfg;
+    ConnectiveArena connectiveArena;
 
     int recursionCount = 0;
 
@@ -126,6 +132,8 @@ struct ConstraintGraphBuilder
      */
     NotNull<Constraint> addConstraint(const ScopePtr& scope, std::unique_ptr<Constraint> c);
 
+    void applyRefinements(const ScopePtr& scope, Location location, ConnectiveId connective);
+
     /**
      * The entry point to the ConstraintGraphBuilder. This will construct a set
      * of scopes, constraints, and free types that can be solved later.
@@ -167,10 +175,10 @@ struct ConstraintGraphBuilder
      *      surrounding context.  Used to implement bidirectional type checking.
      * @return the type of the expression.
      */
-    Inference check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType = {});
+    Inference check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType = {}, bool forceSingleton = false);
 
-    Inference check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType, bool forceSingleton);
-    Inference check(const ScopePtr& scope, AstExprConstantBool* bool_, std::optional<TypeId> expectedType);
+    Inference check(const ScopePtr& scope, AstExprConstantBool* bool_, std::optional<TypeId> expectedType, bool forceSingleton);
     Inference check(const ScopePtr& scope, AstExprLocal* local);
     Inference check(const ScopePtr& scope, AstExprGlobal* global);
     Inference check(const ScopePtr& scope, AstExprIndexName* indexName);
@@ -180,6 +188,7 @@ struct ConstraintGraphBuilder
     Inference check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType);
     Inference check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert);
     Inference check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
+    std::tuple<TypeId, TypeId, ConnectiveId> checkBinary(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
 
     TypePackId checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs);
 

Analysis/include/Luau/ConstraintSolver.h

@@ -110,7 +110,7 @@ struct ConstraintSolver
     bool tryDispatch(const FunctionCallConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const PrimitiveTypeConstraint& c, NotNull<const Constraint> constraint);
     bool tryDispatch(const HasPropConstraint& c, NotNull<const Constraint> constraint);
-    bool tryDispatch(const RefinementConstraint& c, NotNull<const Constraint> constraint);
+    bool tryDispatch(const SingletonOrTopTypeConstraint& c, NotNull<const Constraint> constraint);
 
     // for a, ... in some_table do
     // also handles __iter metamethod

Analysis/include/Luau/Normalize.h

@@ -17,10 +17,8 @@ struct SingletonTypes;
 
 using ModulePtr = std::shared_ptr<Module>;
 
-bool isSubtype(
+bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-    TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice, bool anyIsTop = true);
+bool isSubtype(TypePackId subTy, TypePackId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-bool isSubtype(TypePackId subTy, TypePackId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice,
-    bool anyIsTop = true);
 
 class TypeIds
 {
@@ -169,12 +167,26 @@ struct NormalizedStringType
 
 bool isSubtype(const NormalizedStringType& subStr, const NormalizedStringType& superStr);
 
-// A normalized function type is either `never` (represented by `nullopt`)
+// A normalized function type can be `never`, the top function type `function`,
 // or an intersection of function types.
-// NOTE: type normalization can fail on function types with generics
+//
-// (e.g. because we do not support unions and intersections of generic type packs),
+// NOTE: type normalization can fail on function types with generics (e.g.
-// so this type may contain `error`.
+// because we do not support unions and intersections of generic type packs), so
-using NormalizedFunctionType = std::optional<TypeIds>;
+// this type may contain `error`.
+struct NormalizedFunctionType
+{
+    NormalizedFunctionType();
+
+    bool isTop = false;
+    // TODO: Remove this wrapping optional when clipping
+    // FFlagLuauNegatedFunctionTypes.
+    std::optional<TypeIds> parts;
+
+    void resetToNever();
+    void resetToTop();
+
+    bool isNever() const;
+};
 
 // A normalized generic/free type is a union, where each option is of the form (X & T) where
 // * X is either a free type or a generic
@@ -234,12 +246,14 @@ struct NormalizedType
 
     NormalizedType(NotNull<SingletonTypes> singletonTypes);
 
-    NormalizedType(const NormalizedType&) = delete;
-    NormalizedType(NormalizedType&&) = default;
     NormalizedType() = delete;
     ~NormalizedType() = default;
+
+    NormalizedType(const NormalizedType&) = delete;
+    NormalizedType& operator=(const NormalizedType&) = delete;
+
+    NormalizedType(NormalizedType&&) = default;
     NormalizedType& operator=(NormalizedType&&) = default;
-    NormalizedType& operator=(NormalizedType&) = delete;
 };
 
 class Normalizer
@@ -291,7 +305,7 @@ public:
     bool unionNormalWithTy(NormalizedType& here, TypeId there, int ignoreSmallerTyvars = -1);
 
     // ------- Negations
-    NormalizedType negateNormal(const NormalizedType& here);
+    std::optional<NormalizedType> negateNormal(const NormalizedType& here);
     TypeIds negateAll(const TypeIds& theres);
     TypeId negate(TypeId there);
     void subtractPrimitive(NormalizedType& here, TypeId ty);

Analysis/include/Luau/TypeUtils.h

@@ -35,7 +35,7 @@ std::vector<TypeId> flatten(TypeArena& arena, NotNull<SingletonTypes> singletonT
  * identity) types.
  * @param types the input type list to reduce.
  * @returns the reduced type list.
-*/
+ */
 std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types);
 
 /**
@@ -45,7 +45,7 @@ std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types);
  * @param arena the type arena to allocate the new type in, if necessary
  * @param ty the type to remove nil from
  * @returns a type with nil removed, or nil itself if that were the only option.
-*/
+ */
 TypeId stripNil(NotNull<SingletonTypes> singletonTypes, TypeArena& arena, TypeId ty);
 
 } // namespace Luau

Analysis/include/Luau/TypeVar.h

@@ -115,6 +115,7 @@ struct PrimitiveTypeVar
         Number,
         String,
         Thread,
+        Function,
     };
 
     Type type;
@@ -504,14 +505,6 @@ struct NeverTypeVar
 {
 };
 
-// Invariant 1: there should never be a reason why such UseTypeVar exists without it mapping to another type.
-// Invariant 2: UseTypeVar should always disappear across modules.
-struct UseTypeVar
-{
-    DefId def;
-    NotNull<Scope> scope;
-};
-
 // ~T
 // TODO: Some simplification step that overwrites the type graph to make sure negation
 // types disappear from the user's view, and (?) a debug flag to disable that
@@ -522,9 +515,9 @@ struct NegationTypeVar
 
 using ErrorTypeVar = Unifiable::Error;
 
-using TypeVariant = Unifiable::Variant<TypeId, PrimitiveTypeVar, BlockedTypeVar, PendingExpansionTypeVar, SingletonTypeVar, FunctionTypeVar,
+using TypeVariant =
-    TableTypeVar, MetatableTypeVar, ClassTypeVar, AnyTypeVar, UnionTypeVar, IntersectionTypeVar, LazyTypeVar, UnknownTypeVar, NeverTypeVar,
+    Unifiable::Variant<TypeId, PrimitiveTypeVar, BlockedTypeVar, PendingExpansionTypeVar, SingletonTypeVar, FunctionTypeVar, TableTypeVar,
-    UseTypeVar, NegationTypeVar>;
+        MetatableTypeVar, ClassTypeVar, AnyTypeVar, UnionTypeVar, IntersectionTypeVar, LazyTypeVar, UnknownTypeVar, NeverTypeVar, NegationTypeVar>;
 
 struct TypeVar final
 {
@@ -644,13 +637,14 @@ public:
     const TypeId stringType;
     const TypeId booleanType;
     const TypeId threadType;
+    const TypeId functionType;
     const TypeId trueType;
     const TypeId falseType;
     const TypeId anyType;
     const TypeId unknownType;
     const TypeId neverType;
     const TypeId errorType;
-    const TypeId falsyType; // No type binding!
+    const TypeId falsyType;  // No type binding!
     const TypeId truthyType; // No type binding!
 
     const TypePackId anyTypePack;

Analysis/include/Luau/Unifier.h

@@ -61,7 +61,6 @@ struct Unifier
     ErrorVec errors;
     Location location;
     Variance variance = Covariant;
-    bool anyIsTop = false;  // If true, we consider any to be a top type.  If false, it is a familiar but weird mix of top and bottom all at once.
     bool normalize;         // Normalize unions and intersections if necessary
     bool useScopes = false; // If true, we use the scope hierarchy rather than TypeLevels
     CountMismatch::Context ctx = CountMismatch::Arg;
@@ -131,6 +130,7 @@ public:
     Unifier makeChildUnifier();
 
     void reportError(TypeError err);
+    LUAU_NOINLINE void reportError(Location location, TypeErrorData data);
 
 private:
     bool isNonstrictMode() const;

Analysis/include/Luau/Variant.h

@@ -58,13 +58,15 @@ public:
 
         constexpr int tid = getTypeId<T>();
         typeId = tid;
-        new (&storage) TT(value);
+        new (&storage) TT(std::forward<T>(value));
     }
 
     Variant(const Variant& other)
     {
+        static constexpr FnCopy table[sizeof...(Ts)] = {&fnCopy<Ts>...};
+
         typeId = other.typeId;
-        tableCopy[typeId](&storage, &other.storage);
+        table[typeId](&storage, &other.storage);
     }
 
     Variant(Variant&& other)
@@ -192,7 +194,6 @@ private:
         return *static_cast<const T*>(lhs) == *static_cast<const T*>(rhs);
     }
 
-    static constexpr FnCopy tableCopy[sizeof...(Ts)] = {&fnCopy<Ts>...};
     static constexpr FnMove tableMove[sizeof...(Ts)] = {&fnMove<Ts>...};
     static constexpr FnDtor tableDtor[sizeof...(Ts)] = {&fnDtor<Ts>...};
 

Analysis/include/Luau/VisitTypeVar.h

@@ -155,10 +155,6 @@ struct GenericTypeVarVisitor
     {
         return visit(ty);
     }
-    virtual bool visit(TypeId ty, const UseTypeVar& utv)
-    {
-        return visit(ty);
-    }
     virtual bool visit(TypeId ty, const NegationTypeVar& ntv)
     {
         return visit(ty);
@@ -321,8 +317,6 @@ struct GenericTypeVarVisitor
                     traverse(a);
             }
         }
-        else if (auto utv = get<UseTypeVar>(ty))
-            visit(ty, *utv);
         else if (auto ntv = get<NegationTypeVar>(ty))
             visit(ty, *ntv);
         else if (!FFlag::LuauCompleteVisitor)

Analysis/src/BuiltinDefinitions.cpp

@@ -714,8 +714,7 @@ static bool dcrMagicFunctionPack(MagicFunctionCallContext context)
         result = arena->addType(UnionTypeVar{std::move(options)});
 
     TypeId numberType = context.solver->singletonTypes->numberType;
-    TypeId packedTable = arena->addType(
+    TypeId packedTable = arena->addType(TableTypeVar{{{"n", {numberType}}}, TableIndexer(numberType, result), {}, TableState::Sealed});
-        TableTypeVar{{{"n", {numberType}}}, TableIndexer(numberType, result), {}, TableState::Sealed});
 
     TypePackId tableTypePack = arena->addTypePack({packedTable});
     asMutable(context.result)->ty.emplace<BoundTypePack>(tableTypePack);

Analysis/src/Clone.cpp

@@ -62,7 +62,6 @@ struct TypeCloner
     void operator()(const LazyTypeVar& t);
     void operator()(const UnknownTypeVar& t);
     void operator()(const NeverTypeVar& t);
-    void operator()(const UseTypeVar& t);
     void operator()(const NegationTypeVar& t);
 };
 
@@ -338,12 +337,6 @@ void TypeCloner::operator()(const NeverTypeVar& t)
     defaultClone(t);
 }
 
-void TypeCloner::operator()(const UseTypeVar& t)
-{
-    TypeId result = dest.addType(BoundTypeVar{follow(typeId)});
-    seenTypes[typeId] = result;
-}
-
 void TypeCloner::operator()(const NegationTypeVar& t)
 {
     TypeId result = dest.addType(AnyTypeVar{});

Analysis/src/Connective.cpp

@@ -0,0 +1,32 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/Connective.h"
+
+namespace Luau
+{
+
+ConnectiveId ConnectiveArena::negation(ConnectiveId connective)
+{
+    return NotNull{allocator.allocate(Negation{connective})};
+}
+
+ConnectiveId ConnectiveArena::conjunction(ConnectiveId lhs, ConnectiveId rhs)
+{
+    return NotNull{allocator.allocate(Conjunction{lhs, rhs})};
+}
+
+ConnectiveId ConnectiveArena::disjunction(ConnectiveId lhs, ConnectiveId rhs)
+{
+    return NotNull{allocator.allocate(Disjunction{lhs, rhs})};
+}
+
+ConnectiveId ConnectiveArena::equivalence(ConnectiveId lhs, ConnectiveId rhs)
+{
+    return NotNull{allocator.allocate(Equivalence{lhs, rhs})};
+}
+
+ConnectiveId ConnectiveArena::proposition(DefId def, TypeId discriminantTy)
+{
+    return NotNull{allocator.allocate(Proposition{def, discriminantTy})};
+}
+
+} // namespace Luau

Analysis/src/ConstraintGraphBuilder.cpp

@@ -107,6 +107,101 @@ NotNull<Constraint> ConstraintGraphBuilder::addConstraint(const ScopePtr& scope,
     return NotNull{scope->constraints.emplace_back(std::move(c)).get()};
 }
 
+static void unionRefinements(const std::unordered_map<DefId, TypeId>& lhs, const std::unordered_map<DefId, TypeId>& rhs,
+    std::unordered_map<DefId, TypeId>& dest, NotNull<TypeArena> arena)
+{
+    for (auto [def, ty] : lhs)
+    {
+        auto rhsIt = rhs.find(def);
+        if (rhsIt == rhs.end())
+            continue;
+
+        std::vector<TypeId> discriminants{{ty, rhsIt->second}};
+
+        if (auto destIt = dest.find(def); destIt != dest.end())
+            discriminants.push_back(destIt->second);
+
+        dest[def] = arena->addType(UnionTypeVar{std::move(discriminants)});
+    }
+}
+
+static void computeRefinement(const ScopePtr& scope, ConnectiveId connective, std::unordered_map<DefId, TypeId>* refis, bool sense,
+    NotNull<TypeArena> arena, bool eq, std::vector<SingletonOrTopTypeConstraint>* constraints)
+{
+    using RefinementMap = std::unordered_map<DefId, TypeId>;
+
+    if (!connective)
+        return;
+    else if (auto negation = get<Negation>(connective))
+        return computeRefinement(scope, negation->connective, refis, !sense, arena, eq, constraints);
+    else if (auto conjunction = get<Conjunction>(connective))
+    {
+        RefinementMap lhsRefis;
+        RefinementMap rhsRefis;
+
+        computeRefinement(scope, conjunction->lhs, sense ? refis : &lhsRefis, sense, arena, eq, constraints);
+        computeRefinement(scope, conjunction->rhs, sense ? refis : &rhsRefis, sense, arena, eq, constraints);
+
+        if (!sense)
+            unionRefinements(lhsRefis, rhsRefis, *refis, arena);
+    }
+    else if (auto disjunction = get<Disjunction>(connective))
+    {
+        RefinementMap lhsRefis;
+        RefinementMap rhsRefis;
+
+        computeRefinement(scope, disjunction->lhs, sense ? &lhsRefis : refis, sense, arena, eq, constraints);
+        computeRefinement(scope, disjunction->rhs, sense ? &rhsRefis : refis, sense, arena, eq, constraints);
+
+        if (sense)
+            unionRefinements(lhsRefis, rhsRefis, *refis, arena);
+    }
+    else if (auto equivalence = get<Equivalence>(connective))
+    {
+        computeRefinement(scope, equivalence->lhs, refis, sense, arena, true, constraints);
+        computeRefinement(scope, equivalence->rhs, refis, sense, arena, true, constraints);
+    }
+    else if (auto proposition = get<Proposition>(connective))
+    {
+        TypeId discriminantTy = proposition->discriminantTy;
+        if (!sense && !eq)
+            discriminantTy = arena->addType(NegationTypeVar{proposition->discriminantTy});
+        else if (!sense && eq)
+        {
+            discriminantTy = arena->addType(BlockedTypeVar{});
+            constraints->push_back(SingletonOrTopTypeConstraint{discriminantTy, proposition->discriminantTy});
+        }
+
+        if (auto it = refis->find(proposition->def); it != refis->end())
+            (*refis)[proposition->def] = arena->addType(IntersectionTypeVar{{discriminantTy, it->second}});
+        else
+            (*refis)[proposition->def] = discriminantTy;
+    }
+}
+
+void ConstraintGraphBuilder::applyRefinements(const ScopePtr& scope, Location location, ConnectiveId connective)
+{
+    if (!connective)
+        return;
+
+    std::unordered_map<DefId, TypeId> refinements;
+    std::vector<SingletonOrTopTypeConstraint> constraints;
+    computeRefinement(scope, connective, &refinements, /*sense*/ true, arena, /*eq*/ false, &constraints);
+
+    for (auto [def, discriminantTy] : refinements)
+    {
+        std::optional<TypeId> defTy = scope->lookup(def);
+        if (!defTy)
+            ice->ice("Every DefId must map to a type!");
+
+        TypeId resultTy = arena->addType(IntersectionTypeVar{{*defTy, discriminantTy}});
+        scope->dcrRefinements[def] = resultTy;
+    }
+
+    for (auto& c : constraints)
+        addConstraint(scope, location, c);
+}
+
 void ConstraintGraphBuilder::visit(AstStatBlock* block)
 {
     LUAU_ASSERT(scopes.empty());
@@ -250,14 +345,33 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
 
         if (value->is<AstExprConstantNil>())
         {
-            // HACK: we leave nil-initialized things floating under the assumption that they will later be populated.
+            // HACK: we leave nil-initialized things floating under the
-            // See the test TypeInfer/infer_locals_with_nil_value.
+            // assumption that they will later be populated.
-            // Better flow awareness should make this obsolete.
+            //
+            // See the test TypeInfer/infer_locals_with_nil_value. Better flow
+            // awareness should make this obsolete.
 
             if (!varTypes[i])
                 varTypes[i] = freshType(scope);
         }
-        else if (i == local->values.size - 1)
+        // Only function calls and vararg expressions can produce packs.  All
+        // other expressions produce exactly one value.
+        else if (i != local->values.size - 1 || (!value->is<AstExprCall>() && !value->is<AstExprVarargs>()))
+        {
+            std::optional<TypeId> expectedType;
+            if (hasAnnotation)
+                expectedType = varTypes.at(i);
+
+            TypeId exprType = check(scope, value, expectedType).ty;
+            if (i < varTypes.size())
+            {
+                if (varTypes[i])
+                    addConstraint(scope, local->location, SubtypeConstraint{exprType, varTypes[i]});
+                else
+                    varTypes[i] = exprType;
+            }
+        }
+        else
         {
             std::vector<TypeId> expectedTypes;
             if (hasAnnotation)
@@ -286,21 +400,6 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
                 addConstraint(scope, local->location, PackSubtypeConstraint{exprPack, tailPack});
             }
         }
-        else
-        {
-            std::optional<TypeId> expectedType;
-            if (hasAnnotation)
-                expectedType = varTypes.at(i);
-
-            TypeId exprType = check(scope, value, expectedType).ty;
-            if (i < varTypes.size())
-            {
-                if (varTypes[i])
-                    addConstraint(scope, local->location, SubtypeConstraint{varTypes[i], exprType});
-                else
-                    varTypes[i] = exprType;
-            }
-        }
     }
 
     for (size_t i = 0; i < local->vars.size; ++i)
@@ -569,14 +668,16 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatIf* ifStatement
     // TODO: Optimization opportunity, the interior scope of the condition could be
     // reused for the then body, so we don't need to refine twice.
     ScopePtr condScope = childScope(ifStatement->condition, scope);
-    check(condScope, ifStatement->condition, std::nullopt);
+    auto [_, connective] = check(condScope, ifStatement->condition, std::nullopt);
 
     ScopePtr thenScope = childScope(ifStatement->thenbody, scope);
+    applyRefinements(thenScope, Location{}, connective);
     visit(thenScope, ifStatement->thenbody);
 
     if (ifStatement->elsebody)
     {
         ScopePtr elseScope = childScope(ifStatement->elsebody, scope);
+        applyRefinements(elseScope, Location{}, connectiveArena.negation(connective));
         visit(elseScope, ifStatement->elsebody);
     }
 }
@@ -925,7 +1026,7 @@ InferencePack ConstraintGraphBuilder::checkPack(const ScopePtr& scope, AstExprCa
     }
 }
 
-Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType, bool forceSingleton)
 {
     RecursionCounter counter{&recursionCount};
 
@@ -938,13 +1039,13 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, st
     Inference result;
 
     if (auto group = expr->as<AstExprGroup>())
-        result = check(scope, group->expr, expectedType);
+        result = check(scope, group->expr, expectedType, forceSingleton);
     else if (auto stringExpr = expr->as<AstExprConstantString>())
-        result = check(scope, stringExpr, expectedType);
+        result = check(scope, stringExpr, expectedType, forceSingleton);
     else if (expr->is<AstExprConstantNumber>())
         result = Inference{singletonTypes->numberType};
     else if (auto boolExpr = expr->as<AstExprConstantBool>())
-        result = check(scope, boolExpr, expectedType);
+        result = check(scope, boolExpr, expectedType, forceSingleton);
     else if (expr->is<AstExprConstantNil>())
         result = Inference{singletonTypes->nilType};
     else if (auto local = expr->as<AstExprLocal>())
@@ -999,8 +1100,11 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, st
     return result;
 }
 
-Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantString* string, std::optional<TypeId> expectedType, bool forceSingleton)
 {
+    if (forceSingleton)
+        return Inference{arena->addType(SingletonTypeVar{StringSingleton{std::string{string->value.data, string->value.size}}})};
+
     if (expectedType)
     {
         const TypeId expectedTy = follow(*expectedType);
@@ -1020,12 +1124,15 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantSt
     return Inference{singletonTypes->stringType};
 }
 
-Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantBool* boolExpr, std::optional<TypeId> expectedType)
+Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantBool* boolExpr, std::optional<TypeId> expectedType, bool forceSingleton)
 {
+    const TypeId singletonType = boolExpr->value ? singletonTypes->trueType : singletonTypes->falseType;
+    if (forceSingleton)
+        return Inference{singletonType};
+
     if (expectedType)
     {
         const TypeId expectedTy = follow(*expectedType);
-        const TypeId singletonType = boolExpr->value ? singletonTypes->trueType : singletonTypes->falseType;
 
         if (get<BlockedTypeVar>(expectedTy) || get<PendingExpansionTypeVar>(expectedTy))
         {
@@ -1045,8 +1152,8 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprConstantBo
 Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* local)
 {
     std::optional<TypeId> resultTy;
-
+    auto def = dfg->getDef(local);
-    if (auto def = dfg->getDef(local))
+    if (def)
         resultTy = scope->lookup(*def);
 
     if (!resultTy)
@@ -1058,7 +1165,10 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* loc
     if (!resultTy)
         return Inference{singletonTypes->errorRecoveryType()}; // TODO: replace with ice, locals should never exist before its definition.
 
-    return Inference{*resultTy};
+    if (def)
+        return Inference{*resultTy, connectiveArena.proposition(*def, singletonTypes->truthyType)};
+    else
+        return Inference{*resultTy};
 }
 
 Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprGlobal* global)
@@ -1107,20 +1217,23 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexExpr*
 
 Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprUnary* unary)
 {
-    TypeId operandType = check(scope, unary->expr).ty;
+    auto [operandType, connective] = check(scope, unary->expr);
     TypeId resultType = arena->addType(BlockedTypeVar{});
     addConstraint(scope, unary->location, UnaryConstraint{unary->op, operandType, resultType});
-    return Inference{resultType};
+
+    if (unary->op == AstExprUnary::Not)
+        return Inference{resultType, connectiveArena.negation(connective)};
+    else
+        return Inference{resultType};
 }
 
 Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType)
 {
-    TypeId leftType = check(scope, binary->left, expectedType).ty;
+    auto [leftType, rightType, connective] = checkBinary(scope, binary, expectedType);
-    TypeId rightType = check(scope, binary->right, expectedType).ty;
 
     TypeId resultType = arena->addType(BlockedTypeVar{});
     addConstraint(scope, binary->location, BinaryConstraint{binary->op, leftType, rightType, resultType});
-    return Inference{resultType};
+    return Inference{resultType, std::move(connective)};
 }
 
 Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType)
@@ -1147,6 +1260,58 @@ Inference ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTypeAssert
     return Inference{resolveType(scope, typeAssert->annotation)};
 }
 
+std::tuple<TypeId, TypeId, ConnectiveId> ConstraintGraphBuilder::checkBinary(
+    const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType)
+{
+    if (binary->op == AstExprBinary::And)
+    {
+        auto [leftType, leftConnective] = check(scope, binary->left, expectedType);
+
+        ScopePtr rightScope = childScope(binary->right, scope);
+        applyRefinements(rightScope, binary->right->location, leftConnective);
+        auto [rightType, rightConnective] = check(rightScope, binary->right, expectedType);
+
+        return {leftType, rightType, connectiveArena.conjunction(leftConnective, rightConnective)};
+    }
+    else if (binary->op == AstExprBinary::Or)
+    {
+        auto [leftType, leftConnective] = check(scope, binary->left, expectedType);
+
+        ScopePtr rightScope = childScope(binary->right, scope);
+        applyRefinements(rightScope, binary->right->location, connectiveArena.negation(leftConnective));
+        auto [rightType, rightConnective] = check(rightScope, binary->right, expectedType);
+
+        return {leftType, rightType, connectiveArena.disjunction(leftConnective, rightConnective)};
+    }
+    else if (binary->op == AstExprBinary::CompareEq || binary->op == AstExprBinary::CompareNe)
+    {
+        TypeId leftType = check(scope, binary->left, expectedType, true).ty;
+        TypeId rightType = check(scope, binary->right, expectedType, true).ty;
+
+        ConnectiveId leftConnective = nullptr;
+        if (auto def = dfg->getDef(binary->left))
+            leftConnective = connectiveArena.proposition(*def, rightType);
+
+        ConnectiveId rightConnective = nullptr;
+        if (auto def = dfg->getDef(binary->right))
+            rightConnective = connectiveArena.proposition(*def, leftType);
+
+        if (binary->op == AstExprBinary::CompareNe)
+        {
+            leftConnective = connectiveArena.negation(leftConnective);
+            rightConnective = connectiveArena.negation(rightConnective);
+        }
+
+        return {leftType, rightType, connectiveArena.equivalence(leftConnective, rightConnective)};
+    }
+    else
+    {
+        TypeId leftType = check(scope, binary->left, expectedType).ty;
+        TypeId rightType = check(scope, binary->right, expectedType).ty;
+        return {leftType, rightType, nullptr};
+    }
+}
+
 TypePackId ConstraintGraphBuilder::checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs)
 {
     std::vector<TypeId> types;
@@ -1841,9 +2006,13 @@ std::vector<std::pair<Name, GenericTypePackDefinition>> ConstraintGraphBuilder::
 
 Inference ConstraintGraphBuilder::flattenPack(const ScopePtr& scope, Location location, InferencePack pack)
 {
-    auto [tp] = pack;
+    const auto& [tp, connectives] = pack;
+    ConnectiveId connective = nullptr;
+    if (!connectives.empty())
+        connective = connectives[0];
+
     if (auto f = first(tp))
-        return Inference{*f};
+        return Inference{*f, connective};
 
     TypeId typeResult = freshType(scope);
     TypePack onePack{{typeResult}, freshTypePack(scope)};
@@ -1851,7 +2020,7 @@ Inference ConstraintGraphBuilder::flattenPack(const ScopePtr& scope, Location lo
 
     addConstraint(scope, location, PackSubtypeConstraint{tp, oneTypePack});
 
-    return Inference{typeResult};
+    return Inference{typeResult, connective};
 }
 
 void ConstraintGraphBuilder::reportError(Location location, TypeErrorData err)

Analysis/src/ConstraintSolver.cpp

@@ -440,8 +440,8 @@ bool ConstraintSolver::tryDispatch(NotNull<const Constraint> constraint, bool fo
         success = tryDispatch(*fcc, constraint);
     else if (auto hpc = get<HasPropConstraint>(*constraint))
         success = tryDispatch(*hpc, constraint);
-    else if (auto rc = get<RefinementConstraint>(*constraint))
+    else if (auto sottc = get<SingletonOrTopTypeConstraint>(*constraint))
-        success = tryDispatch(*rc, constraint);
+        success = tryDispatch(*sottc, constraint);
     else
         LUAU_ASSERT(false);
 
@@ -1274,25 +1274,18 @@ bool ConstraintSolver::tryDispatch(const HasPropConstraint& c, NotNull<const Con
     return true;
 }
 
-bool ConstraintSolver::tryDispatch(const RefinementConstraint& c, NotNull<const Constraint> constraint)
+bool ConstraintSolver::tryDispatch(const SingletonOrTopTypeConstraint& c, NotNull<const Constraint> constraint)
 {
-    // TODO: Figure out exact details on when refinements need to be blocked.
+    if (isBlocked(c.discriminantType))
-    // It's possible that it never needs to be, since we can just use intersection types with the discriminant type?
+        return false;
 
-    if (!constraint->scope->parent)
+    TypeId followed = follow(c.discriminantType);
-        iceReporter.ice("No parent scope");
 
-    std::optional<TypeId> previousTy = constraint->scope->parent->lookup(c.def);
+    // `nil` is a singleton type too! There's only one value of type `nil`.
-    if (!previousTy)
+    if (get<SingletonTypeVar>(followed) || isNil(followed))
-        iceReporter.ice("No previous type");
+        *asMutable(c.resultType) = NegationTypeVar{c.discriminantType};
-
+    else
-    std::optional<TypeId> useTy = constraint->scope->lookup(c.def);
+        *asMutable(c.resultType) = BoundTypeVar{singletonTypes->unknownType};
-    if (!useTy)
-        iceReporter.ice("The def is not bound to a type");
-
-    TypeId resultTy = follow(*useTy);
-    std::vector<TypeId> parts{*previousTy, c.discriminantType};
-    asMutable(resultTy)->ty.emplace<IntersectionTypeVar>(std::move(parts));
 
     return true;
 }

Analysis/src/EmbeddedBuiltinDefinitions.cpp

@@ -13,16 +13,16 @@ declare bit32: {
     bor: (...number) -> number,
     bxor: (...number) -> number,
     btest: (number, ...number) -> boolean,
-    rrotate: (number, number) -> number,
+    rrotate: (x: number, disp: number) -> number,
-    lrotate: (number, number) -> number,
+    lrotate: (x: number, disp: number) -> number,
-    lshift: (number, number) -> number,
+    lshift: (x: number, disp: number) -> number,
-    arshift: (number, number) -> number,
+    arshift: (x: number, disp: number) -> number,
-    rshift: (number, number) -> number,
+    rshift: (x: number, disp: number) -> number,
-    bnot: (number) -> number,
+    bnot: (x: number) -> number,
-    extract: (number, number, number?) -> number,
+    extract: (n: number, field: number, width: number?) -> number,
-    replace: (number, number, number, number?) -> number,
+    replace: (n: number, v: number, field: number, width: number?) -> number,
-    countlz: (number) -> number,
+    countlz: (n: number) -> number,
-    countrz: (number) -> number,
+    countrz: (n: number) -> number,
 }
 
 declare math: {
@@ -93,9 +93,9 @@ type DateTypeResult = {
 }
 
 declare os: {
-    time: (DateTypeArg?) -> number,
+    time: (time: DateTypeArg?) -> number,
-    date: (string?, number?) -> DateTypeResult | string,
+    date: (formatString: string?, time: number?) -> DateTypeResult | string,
-    difftime: (DateTypeResult | number, DateTypeResult | number) -> number,
+    difftime: (t2: DateTypeResult | number, t1: DateTypeResult | number) -> number,
     clock: () -> number,
 }
 
@@ -145,51 +145,51 @@ declare function loadstring<A...>(src: string, chunkname: string?): (((A...) ->
 declare function newproxy(mt: boolean?): any
 
 declare coroutine: {
-    create: <A..., R...>((A...) -> R...) -> thread,
+    create: <A..., R...>(f: (A...) -> R...) -> thread,
-    resume: <A..., R...>(thread, A...) -> (boolean, R...),
+    resume: <A..., R...>(co: thread, A...) -> (boolean, R...),
     running: () -> thread,
-    status: (thread) -> "dead" | "running" | "normal" | "suspended",
+    status: (co: thread) -> "dead" | "running" | "normal" | "suspended",
     -- FIXME: This technically returns a function, but we can't represent this yet.
-    wrap: <A..., R...>((A...) -> R...) -> any,
+    wrap: <A..., R...>(f: (A...) -> R...) -> any,
     yield: <A..., R...>(A...) -> R...,
     isyieldable: () -> boolean,
-    close: (thread) -> (boolean, any)
+    close: (co: thread) -> (boolean, any)
 }
 
 declare table: {
-    concat: <V>({V}, string?, number?, number?) -> string,
+    concat: <V>(t: {V}, sep: string?, i: number?, j: number?) -> string,
-    insert: (<V>({V}, V) -> ()) & (<V>({V}, number, V) -> ()),
+    insert: (<V>(t: {V}, value: V) -> ()) & (<V>(t: {V}, pos: number, value: V) -> ()),
-    maxn: <V>({V}) -> number,
+    maxn: <V>(t: {V}) -> number,
-    remove: <V>({V}, number?) -> V?,
+    remove: <V>(t: {V}, number?) -> V?,
-    sort: <V>({V}, ((V, V) -> boolean)?) -> (),
+    sort: <V>(t: {V}, comp: ((V, V) -> boolean)?) -> (),
-    create: <V>(number, V?) -> {V},
+    create: <V>(count: number, value: V?) -> {V},
-    find: <V>({V}, V, number?) -> number?,
+    find: <V>(haystack: {V}, needle: V, init: number?) -> number?,
 
-    unpack: <V>({V}, number?, number?) -> ...V,
+    unpack: <V>(list: {V}, i: number?, j: number?) -> ...V,
     pack: <V>(...V) -> { n: number, [number]: V },
 
-    getn: <V>({V}) -> number,
+    getn: <V>(t: {V}) -> number,
-    foreach: <K, V>({[K]: V}, (K, V) -> ()) -> (),
+    foreach: <K, V>(t: {[K]: V}, f: (K, V) -> ()) -> (),
     foreachi: <V>({V}, (number, V) -> ()) -> (),
 
-    move: <V>({V}, number, number, number, {V}?) -> {V},
+    move: <V>(src: {V}, a: number, b: number, t: number, dst: {V}?) -> {V},
-    clear: <K, V>({[K]: V}) -> (),
+    clear: <K, V>(table: {[K]: V}) -> (),
 
-    isfrozen: <K, V>({[K]: V}) -> boolean,
+    isfrozen: <K, V>(t: {[K]: V}) -> boolean,
 }
 
 declare debug: {
-    info: (<R...>(thread, number, string) -> R...) & (<R...>(number, string) -> R...) & (<A..., R1..., R2...>((A...) -> R1..., string) -> R2...),
+    info: (<R...>(thread: thread, level: number, options: string) -> R...) & (<R...>(level: number, options: string) -> R...) & (<A..., R1..., R2...>(func: (A...) -> R1..., options: string) -> R2...),
-    traceback: ((string?, number?) -> string) & ((thread, string?, number?) -> string),
+    traceback: ((message: string?, level: number?) -> string) & ((thread: thread, message: string?, level: number?) -> string),
 }
 
 declare utf8: {
     char: (...number) -> string,
     charpattern: string,
-    codes: (string) -> ((string, number) -> (number, number), string, number),
+    codes: (str: string) -> ((string, number) -> (number, number), string, number),
-    codepoint: (string, number?, number?) -> ...number,
+    codepoint: (str: string, i: number?, j: number?) -> ...number,
-    len: (string, number?, number?) -> (number?, number?),
+    len: (s: string, i: number?, j: number?) -> (number?, number?),
-    offset: (string, number?, number?) -> number,
+    offset: (s: string, n: number?, i: number?) -> number,
 }
 
 -- Cannot use `typeof` here because it will produce a polytype when we expect a monotype.

Analysis/src/Normalize.cpp

@@ -7,9 +7,9 @@
 
 #include "Luau/Clone.h"
 #include "Luau/Common.h"
+#include "Luau/RecursionCounter.h"
 #include "Luau/TypeVar.h"
 #include "Luau/Unifier.h"
-#include "Luau/VisitTypeVar.h"
 
 LUAU_FASTFLAGVARIABLE(DebugLuauCopyBeforeNormalizing, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant, false)
@@ -20,6 +20,7 @@ LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeCombineTableFix, false);
 LUAU_FASTFLAGVARIABLE(LuauTypeNormalization2, false);
 LUAU_FASTFLAGVARIABLE(LuauNegatedStringSingletons, false);
+LUAU_FASTFLAGVARIABLE(LuauNegatedFunctionTypes, false);
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTFLAG(LuauOverloadedFunctionSubtypingPerf);
@@ -206,6 +207,28 @@ bool isSubtype(const NormalizedStringType& subStr, const NormalizedStringType& s
     return true;
 }
 
+NormalizedFunctionType::NormalizedFunctionType()
+    : parts(FFlag::LuauNegatedFunctionTypes ? std::optional<TypeIds>{TypeIds{}} : std::nullopt)
+{
+}
+
+void NormalizedFunctionType::resetToTop()
+{
+    isTop = true;
+    parts.emplace();
+}
+
+void NormalizedFunctionType::resetToNever()
+{
+    isTop = false;
+    parts.emplace();
+}
+
+bool NormalizedFunctionType::isNever() const
+{
+    return !isTop && (!parts || parts->empty());
+}
+
 NormalizedType::NormalizedType(NotNull<SingletonTypes> singletonTypes)
     : tops(singletonTypes->neverType)
     , booleans(singletonTypes->neverType)
@@ -220,8 +243,8 @@ NormalizedType::NormalizedType(NotNull<SingletonTypes> singletonTypes)
 static bool isInhabited(const NormalizedType& norm)
 {
     return !get<NeverTypeVar>(norm.tops) || !get<NeverTypeVar>(norm.booleans) || !norm.classes.empty() || !get<NeverTypeVar>(norm.errors) ||
-           !get<NeverTypeVar>(norm.nils) || !get<NeverTypeVar>(norm.numbers) || !norm.strings.isNever() ||
+           !get<NeverTypeVar>(norm.nils) || !get<NeverTypeVar>(norm.numbers) || !norm.strings.isNever() || !get<NeverTypeVar>(norm.threads) ||
-           !get<NeverTypeVar>(norm.threads) || norm.functions || !norm.tables.empty() || !norm.tyvars.empty();
+           !norm.functions.isNever() || !norm.tables.empty() || !norm.tyvars.empty();
 }
 
 static int tyvarIndex(TypeId ty)
@@ -317,10 +340,14 @@ static bool isNormalizedThread(TypeId ty)
 
 static bool areNormalizedFunctions(const NormalizedFunctionType& tys)
 {
-    if (tys)
+    if (tys.parts)
-        for (TypeId ty : *tys)
+    {
+        for (TypeId ty : *tys.parts)
+        {
             if (!get<FunctionTypeVar>(ty) && !get<ErrorTypeVar>(ty))
                 return false;
+        }
+    }
     return true;
 }
 
@@ -420,7 +447,7 @@ void Normalizer::clearNormal(NormalizedType& norm)
     norm.strings.resetToNever();
     norm.threads = singletonTypes->neverType;
     norm.tables.clear();
-    norm.functions = std::nullopt;
+    norm.functions.resetToNever();
     norm.tyvars.clear();
 }
 
@@ -809,20 +836,28 @@ std::optional<TypeId> Normalizer::unionOfFunctions(TypeId here, TypeId there)
 
 void Normalizer::unionFunctions(NormalizedFunctionType& heres, const NormalizedFunctionType& theres)
 {
-    if (!theres)
+    if (FFlag::LuauNegatedFunctionTypes)
+    {
+        if (heres.isTop)
+            return;
+        if (theres.isTop)
+            heres.resetToTop();
+    }
+
+    if (theres.isNever())
         return;
 
     TypeIds tmps;
 
-    if (!heres)
+    if (heres.isNever())
     {
-        tmps.insert(theres->begin(), theres->end());
+        tmps.insert(theres.parts->begin(), theres.parts->end());
-        heres = std::move(tmps);
+        heres.parts = std::move(tmps);
         return;
     }
 
-    for (TypeId here : *heres)
+    for (TypeId here : *heres.parts)
-        for (TypeId there : *theres)
+        for (TypeId there : *theres.parts)
         {
             if (std::optional<TypeId> fun = unionOfFunctions(here, there))
                 tmps.insert(*fun);
@@ -830,28 +865,28 @@ void Normalizer::unionFunctions(NormalizedFunctionType& heres, const NormalizedF
                 tmps.insert(singletonTypes->errorRecoveryType(there));
         }
 
-    heres = std::move(tmps);
+    heres.parts = std::move(tmps);
 }
 
 void Normalizer::unionFunctionsWithFunction(NormalizedFunctionType& heres, TypeId there)
 {
-    if (!heres)
+    if (heres.isNever())
     {
         TypeIds tmps;
         tmps.insert(there);
-        heres = std::move(tmps);
+        heres.parts = std::move(tmps);
         return;
     }
 
     TypeIds tmps;
-    for (TypeId here : *heres)
+    for (TypeId here : *heres.parts)
     {
         if (std::optional<TypeId> fun = unionOfFunctions(here, there))
             tmps.insert(*fun);
         else
             tmps.insert(singletonTypes->errorRecoveryType(there));
     }
-    heres = std::move(tmps);
+    heres.parts = std::move(tmps);
 }
 
 void Normalizer::unionTablesWithTable(TypeIds& heres, TypeId there)
@@ -1004,6 +1039,11 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
             here.strings.resetToString();
         else if (ptv->type == PrimitiveTypeVar::Thread)
             here.threads = there;
+        else if (ptv->type == PrimitiveTypeVar::Function)
+        {
+            LUAU_ASSERT(FFlag::LuauNegatedFunctionTypes);
+            here.functions.resetToTop();
+        }
         else
             LUAU_ASSERT(!"Unreachable");
     }
@@ -1036,8 +1076,11 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
     else if (const NegationTypeVar* ntv = get<NegationTypeVar>(there))
     {
         const NormalizedType* thereNormal = normalize(ntv->ty);
-        NormalizedType tn = negateNormal(*thereNormal);
+        std::optional<NormalizedType> tn = negateNormal(*thereNormal);
-        if (!unionNormals(here, tn))
+        if (!tn)
+            return false;
+
+        if (!unionNormals(here, *tn))
             return false;
     }
     else
@@ -1053,7 +1096,7 @@ bool Normalizer::unionNormalWithTy(NormalizedType& here, TypeId there, int ignor
 
 // ------- Negations
 
-NormalizedType Normalizer::negateNormal(const NormalizedType& here)
+std::optional<NormalizedType> Normalizer::negateNormal(const NormalizedType& here)
 {
     NormalizedType result{singletonTypes};
     if (!get<NeverTypeVar>(here.tops))
@@ -1092,10 +1135,24 @@ NormalizedType Normalizer::negateNormal(const NormalizedType& here)
 
     result.threads = get<NeverTypeVar>(here.threads) ? singletonTypes->threadType : singletonTypes->neverType;
 
+    /*
+     * Things get weird and so, so complicated if we allow negations of
+     * arbitrary function types.  Ordinary code can never form these kinds of
+     * types, so we decline to negate them.
+     */
+    if (FFlag::LuauNegatedFunctionTypes)
+    {
+        if (here.functions.isNever())
+            result.functions.resetToTop();
+        else if (here.functions.isTop)
+            result.functions.resetToNever();
+        else
+            return std::nullopt;
+    }
+
     // TODO: negating tables
-    // TODO: negating functions
     // TODO: negating tyvars?
-    
+
     return result;
 }
 
@@ -1142,21 +1199,25 @@ void Normalizer::subtractPrimitive(NormalizedType& here, TypeId ty)
     LUAU_ASSERT(ptv);
     switch (ptv->type)
     {
-        case PrimitiveTypeVar::NilType:
+    case PrimitiveTypeVar::NilType:
-            here.nils = singletonTypes->neverType;
+        here.nils = singletonTypes->neverType;
-            break;
+        break;
-        case PrimitiveTypeVar::Boolean:
+    case PrimitiveTypeVar::Boolean:
-            here.booleans = singletonTypes->neverType;
+        here.booleans = singletonTypes->neverType;
-            break;
+        break;
-        case PrimitiveTypeVar::Number:
+    case PrimitiveTypeVar::Number:
-            here.numbers = singletonTypes->neverType;
+        here.numbers = singletonTypes->neverType;
-            break;
+        break;
-        case PrimitiveTypeVar::String:
+    case PrimitiveTypeVar::String:
-            here.strings.resetToNever();
+        here.strings.resetToNever();
-            break;
+        break;
-        case PrimitiveTypeVar::Thread:
+    case PrimitiveTypeVar::Thread:
-            here.threads = singletonTypes->neverType;
+        here.threads = singletonTypes->neverType;
-            break;
+        break;
+    case PrimitiveTypeVar::Function:
+        LUAU_ASSERT(FFlag::LuauNegatedStringSingletons);
+        here.functions.resetToNever();
+        break;
     }
 }
 
@@ -1589,7 +1650,7 @@ std::optional<TypeId> Normalizer::intersectionOfFunctions(TypeId here, TypeId th
 
     TypePackId argTypes;
     TypePackId retTypes;
-    
+
     if (hftv->retTypes == tftv->retTypes)
     {
         std::optional<TypePackId> argTypesOpt = unionOfTypePacks(hftv->argTypes, tftv->argTypes);
@@ -1598,7 +1659,7 @@ std::optional<TypeId> Normalizer::intersectionOfFunctions(TypeId here, TypeId th
         argTypes = *argTypesOpt;
         retTypes = hftv->retTypes;
     }
-    else if (FFlag::LuauOverloadedFunctionSubtypingPerf && hftv->argTypes == tftv->argTypes) 
+    else if (FFlag::LuauOverloadedFunctionSubtypingPerf && hftv->argTypes == tftv->argTypes)
     {
         std::optional<TypePackId> retTypesOpt = intersectionOfTypePacks(hftv->argTypes, tftv->argTypes);
         if (!retTypesOpt)
@@ -1738,18 +1799,20 @@ std::optional<TypeId> Normalizer::unionSaturatedFunctions(TypeId here, TypeId th
 
 void Normalizer::intersectFunctionsWithFunction(NormalizedFunctionType& heres, TypeId there)
 {
-    if (!heres)
+    if (heres.isNever())
         return;
 
-    for (auto it = heres->begin(); it != heres->end();)
+    heres.isTop = false;
+
+    for (auto it = heres.parts->begin(); it != heres.parts->end();)
     {
         TypeId here = *it;
         if (get<ErrorTypeVar>(here))
             it++;
         else if (std::optional<TypeId> tmp = intersectionOfFunctions(here, there))
         {
-            heres->erase(it);
+            heres.parts->erase(it);
-            heres->insert(*tmp);
+            heres.parts->insert(*tmp);
             return;
         }
         else
@@ -1757,27 +1820,27 @@ void Normalizer::intersectFunctionsWithFunction(NormalizedFunctionType& heres, T
     }
 
     TypeIds tmps;
-    for (TypeId here : *heres)
+    for (TypeId here : *heres.parts)
     {
         if (std::optional<TypeId> tmp = unionSaturatedFunctions(here, there))
             tmps.insert(*tmp);
     }
-    heres->insert(there);
+    heres.parts->insert(there);
-    heres->insert(tmps.begin(), tmps.end());
+    heres.parts->insert(tmps.begin(), tmps.end());
 }
 
 void Normalizer::intersectFunctions(NormalizedFunctionType& heres, const NormalizedFunctionType& theres)
 {
-    if (!heres)
+    if (heres.isNever())
         return;
-    else if (!theres)
+    else if (theres.isNever())
     {
-        heres = std::nullopt;
+        heres.resetToNever();
         return;
     }
     else
     {
-        for (TypeId there : *theres)
+        for (TypeId there : *theres.parts)
             intersectFunctionsWithFunction(heres, there);
     }
 }
@@ -1935,6 +1998,7 @@ bool Normalizer::intersectNormalWithTy(NormalizedType& here, TypeId there)
         TypeId nils = here.nils;
         TypeId numbers = here.numbers;
         NormalizedStringType strings = std::move(here.strings);
+        NormalizedFunctionType functions = std::move(here.functions);
         TypeId threads = here.threads;
 
         clearNormal(here);
@@ -1949,6 +2013,11 @@ bool Normalizer::intersectNormalWithTy(NormalizedType& here, TypeId there)
             here.strings = std::move(strings);
         else if (ptv->type == PrimitiveTypeVar::Thread)
             here.threads = threads;
+        else if (ptv->type == PrimitiveTypeVar::Function)
+        {
+            LUAU_ASSERT(FFlag::LuauNegatedFunctionTypes);
+            here.functions = std::move(functions);
+        }
         else
             LUAU_ASSERT(!"Unreachable");
     }
@@ -1981,8 +2050,10 @@ bool Normalizer::intersectNormalWithTy(NormalizedType& here, TypeId there)
             for (TypeId part : itv->options)
             {
                 const NormalizedType* normalPart = normalize(part);
-                NormalizedType negated = negateNormal(*normalPart);
+                std::optional<NormalizedType> negated = negateNormal(*normalPart);
-                intersectNormals(here, negated);
+                if (!negated)
+                    return false;
+                intersectNormals(here, *negated);
             }
         }
         else
@@ -2016,14 +2087,16 @@ TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
     result.insert(result.end(), norm.classes.begin(), norm.classes.end());
     if (!get<NeverTypeVar>(norm.errors))
         result.push_back(norm.errors);
-    if (norm.functions)
+    if (FFlag::LuauNegatedFunctionTypes && norm.functions.isTop)
+        result.push_back(singletonTypes->functionType);
+    else if (!norm.functions.isNever())
     {
-        if (norm.functions->size() == 1)
+        if (norm.functions.parts->size() == 1)
-            result.push_back(*norm.functions->begin());
+            result.push_back(*norm.functions.parts->begin());
         else
         {
             std::vector<TypeId> parts;
-            parts.insert(parts.end(), norm.functions->begin(), norm.functions->end());
+            parts.insert(parts.end(), norm.functions.parts->begin(), norm.functions.parts->end());
             result.push_back(arena->addType(IntersectionTypeVar{std::move(parts)}));
         }
     }
@@ -2070,62 +2143,24 @@ TypeId Normalizer::typeFromNormal(const NormalizedType& norm)
         return arena->addType(UnionTypeVar{std::move(result)});
 }
 
-namespace
+bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-
-struct Replacer
-{
-    TypeArena* arena;
-    TypeId sourceType;
-    TypeId replacedType;
-    DenseHashMap<TypeId, TypeId> newTypes;
-
-    Replacer(TypeArena* arena, TypeId sourceType, TypeId replacedType)
-        : arena(arena)
-        , sourceType(sourceType)
-        , replacedType(replacedType)
-        , newTypes(nullptr)
-    {
-    }
-
-    TypeId smartClone(TypeId t)
-    {
-        t = follow(t);
-        TypeId* res = newTypes.find(t);
-        if (res)
-            return *res;
-
-        TypeId result = shallowClone(t, *arena, TxnLog::empty());
-        newTypes[t] = result;
-        newTypes[result] = result;
-
-        return result;
-    }
-};
-
-} // anonymous namespace
-
-bool isSubtype(TypeId subTy, TypeId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice, bool anyIsTop)
 {
     UnifierSharedState sharedState{&ice};
     TypeArena arena;
     Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
     Unifier u{NotNull{&normalizer}, Mode::Strict, scope, Location{}, Covariant};
-    u.anyIsTop = anyIsTop;
 
     u.tryUnify(subTy, superTy);
     const bool ok = u.errors.empty() && u.log.empty();
     return ok;
 }
 
-bool isSubtype(
+bool isSubtype(TypePackId subPack, TypePackId superPack, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-    TypePackId subPack, TypePackId superPack, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice, bool anyIsTop)
 {
     UnifierSharedState sharedState{&ice};
     TypeArena arena;
     Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
     Unifier u{NotNull{&normalizer}, Mode::Strict, scope, Location{}, Covariant};
-    u.anyIsTop = anyIsTop;
 
     u.tryUnify(subPack, superPack);
     const bool ok = u.errors.empty() && u.log.empty();

Analysis/src/ToString.cpp

@@ -10,12 +10,12 @@
 #include <algorithm>
 #include <stdexcept>
 
-LUAU_FASTFLAG(LuauUnknownAndNeverType)
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 LUAU_FASTFLAG(LuauLvaluelessPath)
-LUAU_FASTFLAGVARIABLE(LuauSpecialTypesAsterisked, false)
+LUAU_FASTFLAG(LuauUnknownAndNeverType)
 LUAU_FASTFLAGVARIABLE(LuauFixNameMaps, false)
-LUAU_FASTFLAGVARIABLE(LuauUnseeArrayTtv, false)
 LUAU_FASTFLAGVARIABLE(LuauFunctionReturnStringificationFixup, false)
+LUAU_FASTFLAGVARIABLE(LuauUnseeArrayTtv, false)
 
 /*
  * Prefix generic typenames with gen-
@@ -225,6 +225,20 @@ struct StringifierState
         result.name += s;
     }
 
+    void emitLevel(Scope* scope)
+    {
+        size_t count = 0;
+        for (Scope* s = scope; s; s = s->parent.get())
+            ++count;
+
+        emit(count);
+        emit("-");
+        char buffer[16];
+        uint32_t s = uint32_t(intptr_t(scope) & 0xFFFFFF);
+        snprintf(buffer, sizeof(buffer), "0x%x", s);
+        emit(buffer);
+    }
+
     void emit(TypeLevel level)
     {
         emit(std::to_string(level.level));
@@ -296,10 +310,7 @@ struct TypeVarStringifier
         if (tv->ty.valueless_by_exception())
         {
             state.result.error = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("* VALUELESS BY EXCEPTION *");
-                state.emit("* VALUELESS BY EXCEPTION *");
-            else
-                state.emit("< VALUELESS BY EXCEPTION >");
             return;
         }
 
@@ -377,7 +388,10 @@ struct TypeVarStringifier
         if (FFlag::DebugLuauVerboseTypeNames)
         {
             state.emit("-");
-            state.emit(ftv.level);
+            if (FFlag::DebugLuauDeferredConstraintResolution)
+                state.emitLevel(ftv.scope);
+            else
+                state.emit(ftv.level);
         }
     }
 
@@ -399,6 +413,15 @@ struct TypeVarStringifier
         }
         else
             state.emit(state.getName(ty));
+
+        if (FFlag::DebugLuauVerboseTypeNames)
+        {
+            state.emit("-");
+            if (FFlag::DebugLuauDeferredConstraintResolution)
+                state.emitLevel(gtv.scope);
+            else
+                state.emit(gtv.level);
+        }
     }
 
     void operator()(TypeId, const BlockedTypeVar& btv)
@@ -434,6 +457,9 @@ struct TypeVarStringifier
         case PrimitiveTypeVar::Thread:
             state.emit("thread");
             return;
+        case PrimitiveTypeVar::Function:
+            state.emit("function");
+            return;
         default:
             LUAU_ASSERT(!"Unknown primitive type");
             throwRuntimeError("Unknown primitive type " + std::to_string(ptv.type));
@@ -462,10 +488,7 @@ struct TypeVarStringifier
         if (state.hasSeen(&ftv))
         {
             state.result.cycle = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*CYCLE*");
-                state.emit("*CYCLE*");
-            else
-                state.emit("<CYCLE>");
             return;
         }
 
@@ -573,10 +596,7 @@ struct TypeVarStringifier
         if (state.hasSeen(&ttv))
         {
             state.result.cycle = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*CYCLE*");
-                state.emit("*CYCLE*");
-            else
-                state.emit("<CYCLE>");
             return;
         }
 
@@ -710,10 +730,7 @@ struct TypeVarStringifier
         if (state.hasSeen(&uv))
         {
             state.result.cycle = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*CYCLE*");
-                state.emit("*CYCLE*");
-            else
-                state.emit("<CYCLE>");
             return;
         }
 
@@ -780,10 +797,7 @@ struct TypeVarStringifier
         if (state.hasSeen(&uv))
         {
             state.result.cycle = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*CYCLE*");
-                state.emit("*CYCLE*");
-            else
-                state.emit("<CYCLE>");
             return;
         }
 
@@ -828,10 +842,7 @@ struct TypeVarStringifier
     void operator()(TypeId, const ErrorTypeVar& tv)
     {
         state.result.error = true;
-        if (FFlag::LuauSpecialTypesAsterisked)
+        state.emit(FFlag::LuauUnknownAndNeverType ? "*error-type*" : "*unknown*");
-            state.emit(FFlag::LuauUnknownAndNeverType ? "*error-type*" : "*unknown*");
-        else
-            state.emit(FFlag::LuauUnknownAndNeverType ? "<error-type>" : "*unknown*");
     }
 
     void operator()(TypeId, const LazyTypeVar& ltv)
@@ -850,11 +861,6 @@ struct TypeVarStringifier
         state.emit("never");
     }
 
-    void operator()(TypeId ty, const UseTypeVar&)
-    {
-        stringify(follow(ty));
-    }
-
     void operator()(TypeId, const NegationTypeVar& ntv)
     {
         state.emit("~");
@@ -907,10 +913,7 @@ struct TypePackStringifier
         if (tp->ty.valueless_by_exception())
         {
             state.result.error = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("* VALUELESS TP BY EXCEPTION *");
-                state.emit("* VALUELESS TP BY EXCEPTION *");
-            else
-                state.emit("< VALUELESS TP BY EXCEPTION >");
             return;
         }
 
@@ -934,10 +937,7 @@ struct TypePackStringifier
         if (state.hasSeen(&tp))
         {
             state.result.cycle = true;
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*CYCLETP*");
-                state.emit("*CYCLETP*");
-            else
-                state.emit("<CYCLETP>");
             return;
         }
 
@@ -982,10 +982,7 @@ struct TypePackStringifier
     void operator()(TypePackId, const Unifiable::Error& error)
     {
         state.result.error = true;
-        if (FFlag::LuauSpecialTypesAsterisked)
+        state.emit(FFlag::LuauUnknownAndNeverType ? "*error-type*" : "*unknown*");
-            state.emit(FFlag::LuauUnknownAndNeverType ? "*error-type*" : "*unknown*");
-        else
-            state.emit(FFlag::LuauUnknownAndNeverType ? "<error-type>" : "*unknown*");
     }
 
     void operator()(TypePackId, const VariadicTypePack& pack)
@@ -993,10 +990,7 @@ struct TypePackStringifier
         state.emit("...");
         if (FFlag::DebugLuauVerboseTypeNames && pack.hidden)
         {
-            if (FFlag::LuauSpecialTypesAsterisked)
+            state.emit("*hidden*");
-                state.emit("*hidden*");
-            else
-                state.emit("<hidden>");
         }
         stringify(pack.ty);
     }
@@ -1031,7 +1025,10 @@ struct TypePackStringifier
         if (FFlag::DebugLuauVerboseTypeNames)
         {
             state.emit("-");
-            state.emit(pack.level);
+            if (FFlag::DebugLuauDeferredConstraintResolution)
+                state.emitLevel(pack.scope);
+            else
+                state.emit(pack.level);
         }
 
         state.emit("...");
@@ -1204,10 +1201,7 @@ ToStringResult toStringDetailed(TypeId ty, ToStringOptions& opts)
     {
         result.truncated = true;
 
-        if (FFlag::LuauSpecialTypesAsterisked)
+        result.name += "... *TRUNCATED*";
-            result.name += "... *TRUNCATED*";
-        else
-            result.name += "... <TRUNCATED>";
     }
 
     return result;
@@ -1280,10 +1274,7 @@ ToStringResult toStringDetailed(TypePackId tp, ToStringOptions& opts)
 
     if (opts.maxTypeLength > 0 && result.name.length() > opts.maxTypeLength)
     {
-        if (FFlag::LuauSpecialTypesAsterisked)
+        result.name += "... *TRUNCATED*";
-            result.name += "... *TRUNCATED*";
-        else
-            result.name += "... <TRUNCATED>";
     }
 
     return result;
@@ -1526,9 +1517,12 @@ std::string toString(const Constraint& constraint, ToStringOptions& opts)
         {
             return tos(c.resultType, opts) + " ~ hasProp " + tos(c.subjectType, opts) + ", \"" + c.prop + "\"";
         }
-        else if constexpr (std::is_same_v<T, RefinementConstraint>)
+        else if constexpr (std::is_same_v<T, SingletonOrTopTypeConstraint>)
         {
-            return "TODO";
+            std::string result = tos(c.resultType, opts);
+            std::string discriminant = tos(c.discriminantType, opts);
+
+            return result + " ~ if isSingleton D then ~D else unknown where D = " + discriminant;
         }
         else
             static_assert(always_false_v<T>, "Non-exhaustive constraint switch");

Analysis/src/TypeAttach.cpp

@@ -338,12 +338,6 @@ public:
     {
         return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName{"never"});
     }
-    AstType* operator()(const UseTypeVar& utv)
-    {
-        std::optional<TypeId> ty = utv.scope->lookup(utv.def);
-        LUAU_ASSERT(ty);
-        return Luau::visit(*this, (*ty)->ty);
-    }
     AstType* operator()(const NegationTypeVar& ntv)
     {
         // FIXME: do the same thing we do with ErrorTypeVar

Analysis/src/TypeChecker2.cpp

@@ -301,7 +301,6 @@ struct TypeChecker2
         UnifierSharedState sharedState{&ice};
         Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
         Unifier u{NotNull{&normalizer}, Mode::Strict, stack.back(), ret->location, Covariant};
-        u.anyIsTop = true;
 
         u.tryUnify(actualRetType, expectedRetType);
         const bool ok = u.errors.empty() && u.log.empty();
@@ -331,16 +330,21 @@ struct TypeChecker2
             if (value)
                 visit(value);
 
-            if (i != local->values.size - 1)
+            TypeId* maybeValueType = value ? module->astTypes.find(value) : nullptr;
+            if (i != local->values.size - 1 || maybeValueType)
             {
                 AstLocal* var = i < local->vars.size ? local->vars.data[i] : nullptr;
 
                 if (var && var->annotation)
                 {
-                    TypeId varType = lookupAnnotation(var->annotation);
+                    TypeId annotationType = lookupAnnotation(var->annotation);
                     TypeId valueType = value ? lookupType(value) : nullptr;
-                    if (valueType && !isSubtype(varType, valueType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+                    if (valueType)
-                        reportError(TypeMismatch{varType, valueType}, value->location);
+                    {
+                        ErrorVec errors = tryUnify(stack.back(), value->location, valueType, annotationType);
+                        if (!errors.empty())
+                            reportErrors(std::move(errors));
+                    }
                 }
             }
             else
@@ -606,7 +610,7 @@ struct TypeChecker2
             visit(rhs);
             TypeId rhsType = lookupType(rhs);
 
-            if (!isSubtype(rhsType, lhsType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+            if (!isSubtype(rhsType, lhsType, stack.back(), singletonTypes, ice))
             {
                 reportError(TypeMismatch{lhsType, rhsType}, rhs->location);
             }
@@ -757,7 +761,7 @@ struct TypeChecker2
         TypeId actualType = lookupType(number);
         TypeId numberType = singletonTypes->numberType;
 
-        if (!isSubtype(numberType, actualType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (!isSubtype(numberType, actualType, stack.back(), singletonTypes, ice))
         {
             reportError(TypeMismatch{actualType, numberType}, number->location);
         }
@@ -768,7 +772,7 @@ struct TypeChecker2
         TypeId actualType = lookupType(string);
         TypeId stringType = singletonTypes->stringType;
 
-        if (!isSubtype(actualType, stringType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (!isSubtype(actualType, stringType, stack.back(), singletonTypes, ice))
         {
             reportError(TypeMismatch{actualType, stringType}, string->location);
         }
@@ -857,7 +861,7 @@ struct TypeChecker2
         FunctionTypeVar ftv{argsTp, expectedRetType};
         TypeId expectedType = arena.addType(ftv);
 
-        if (!isSubtype(testFunctionType, expectedType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (!isSubtype(testFunctionType, expectedType, stack.back(), singletonTypes, ice))
         {
             CloneState cloneState;
             expectedType = clone(expectedType, module->internalTypes, cloneState);
@@ -876,7 +880,7 @@ struct TypeChecker2
             getIndexTypeFromType(module->getModuleScope(), leftType, indexName->index.value, indexName->location, /* addErrors */ true);
         if (ty)
         {
-            if (!isSubtype(resultType, *ty, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+            if (!isSubtype(resultType, *ty, stack.back(), singletonTypes, ice))
             {
                 reportError(TypeMismatch{resultType, *ty}, indexName->location);
             }
@@ -909,7 +913,7 @@ struct TypeChecker2
                 TypeId inferredArgTy = *argIt;
                 TypeId annotatedArgTy = lookupAnnotation(arg->annotation);
 
-                if (!isSubtype(annotatedArgTy, inferredArgTy, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+                if (!isSubtype(annotatedArgTy, inferredArgTy, stack.back(), singletonTypes, ice))
                 {
                     reportError(TypeMismatch{annotatedArgTy, inferredArgTy}, arg->location);
                 }
@@ -1203,10 +1207,10 @@ struct TypeChecker2
         TypeId computedType = lookupType(expr->expr);
 
         // Note: As an optimization, we try 'number <: number | string' first, as that is the more likely case.
-        if (isSubtype(annotationType, computedType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (isSubtype(annotationType, computedType, stack.back(), singletonTypes, ice))
             return;
 
-        if (isSubtype(computedType, annotationType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (isSubtype(computedType, annotationType, stack.back(), singletonTypes, ice))
             return;
 
         reportError(TypesAreUnrelated{computedType, annotationType}, expr->location);
@@ -1507,7 +1511,6 @@ struct TypeChecker2
         UnifierSharedState sharedState{&ice};
         Normalizer normalizer{&module->internalTypes, singletonTypes, NotNull{&sharedState}};
         Unifier u{NotNull{&normalizer}, Mode::Strict, scope, location, Covariant};
-        u.anyIsTop = true;
         u.tryUnify(subTy, superTy);
 
         return std::move(u.errors);

Analysis/src/TypeVar.cpp

@@ -57,13 +57,6 @@ TypeId follow(TypeId t, std::function<TypeId(TypeId)> mapper)
             return btv->boundTo;
         else if (auto ttv = get<TableTypeVar>(mapper(ty)))
             return ttv->boundTo;
-        else if (auto utv = get<UseTypeVar>(mapper(ty)))
-        {
-            std::optional<TypeId> ty = utv->scope->lookup(utv->def);
-            if (!ty)
-                throwRuntimeError("UseTypeVar must map to another TypeId");
-            return *ty;
-        }
         else
             return std::nullopt;
     };
@@ -761,6 +754,7 @@ SingletonTypes::SingletonTypes()
     , stringType(arena->addType(TypeVar{PrimitiveTypeVar{PrimitiveTypeVar::String}, /*persistent*/ true}))
     , booleanType(arena->addType(TypeVar{PrimitiveTypeVar{PrimitiveTypeVar::Boolean}, /*persistent*/ true}))
     , threadType(arena->addType(TypeVar{PrimitiveTypeVar{PrimitiveTypeVar::Thread}, /*persistent*/ true}))
+    , functionType(arena->addType(TypeVar{PrimitiveTypeVar{PrimitiveTypeVar::Function}, /*persistent*/ true}))
     , trueType(arena->addType(TypeVar{SingletonTypeVar{BooleanSingleton{true}}, /*persistent*/ true}))
     , falseType(arena->addType(TypeVar{SingletonTypeVar{BooleanSingleton{false}}, /*persistent*/ true}))
     , anyType(arena->addType(TypeVar{AnyTypeVar{}, /*persistent*/ true}))
@@ -946,7 +940,8 @@ void persist(TypeId ty)
             queue.push_back(mtv->table);
             queue.push_back(mtv->metatable);
         }
-        else if (get<GenericTypeVar>(t) || get<AnyTypeVar>(t) || get<FreeTypeVar>(t) || get<SingletonTypeVar>(t) || get<PrimitiveTypeVar>(t) || get<NegationTypeVar>(t))
+        else if (get<GenericTypeVar>(t) || get<AnyTypeVar>(t) || get<FreeTypeVar>(t) || get<SingletonTypeVar>(t) || get<PrimitiveTypeVar>(t) ||
+                 get<NegationTypeVar>(t))
         {
         }
         else

Analysis/src/Unifier.cpp

@@ -8,6 +8,7 @@
 #include "Luau/TypePack.h"
 #include "Luau/TypeUtils.h"
 #include "Luau/TimeTrace.h"
+#include "Luau/TypeVar.h"
 #include "Luau/VisitTypeVar.h"
 #include "Luau/ToString.h"
 
@@ -23,6 +24,7 @@ LUAU_FASTFLAGVARIABLE(LuauInstantiateInSubtyping, false)
 LUAU_FASTFLAGVARIABLE(LuauOverloadedFunctionSubtypingPerf, false);
 LUAU_FASTFLAG(LuauClassTypeVarsInSubstitution)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+LUAU_FASTFLAG(LuauNegatedFunctionTypes)
 
 namespace Luau
 {
@@ -363,7 +365,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
     if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
     {
-        reportError(TypeError{location, UnificationTooComplex{}});
+        reportError(location, UnificationTooComplex{});
         return;
     }
 
@@ -404,7 +406,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
         if (subGeneric && !subsumes(useScopes, subGeneric, superFree))
         {
             // TODO: a more informative error message? CLI-39912
-            reportError(TypeError{location, GenericError{"Generic subtype escaping scope"}});
+            reportError(location, GenericError{"Generic subtype escaping scope"});
             return;
         }
 
@@ -433,7 +435,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
         if (superGeneric && !subsumes(useScopes, superGeneric, subFree))
         {
             // TODO: a more informative error message? CLI-39912
-            reportError(TypeError{location, GenericError{"Generic supertype escaping scope"}});
+            reportError(location, GenericError{"Generic supertype escaping scope"});
             return;
         }
 
@@ -450,15 +452,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
         return tryUnifyWithAny(subTy, superTy);
 
     if (get<AnyTypeVar>(subTy))
-    {
+        return tryUnifyWithAny(superTy, subTy);
-        if (anyIsTop)
-        {
-            reportError(TypeError{location, TypeMismatch{superTy, subTy}});
-            return;
-        }
-        else
-            return tryUnifyWithAny(superTy, subTy);
-    }
 
     if (log.get<ErrorTypeVar>(subTy))
         return tryUnifyWithAny(superTy, subTy);
@@ -478,7 +472,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
         if (auto error = sharedState.cachedUnifyError.find({subTy, superTy}))
         {
-            reportError(TypeError{location, *error});
+            reportError(location, *error);
             return;
         }
     }
@@ -520,6 +514,12 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     else if ((log.getMutable<PrimitiveTypeVar>(superTy) || log.getMutable<SingletonTypeVar>(superTy)) && log.getMutable<SingletonTypeVar>(subTy))
         tryUnifySingletons(subTy, superTy);
 
+    else if (auto ptv = get<PrimitiveTypeVar>(superTy);
+             FFlag::LuauNegatedFunctionTypes && ptv && ptv->type == PrimitiveTypeVar::Function && get<FunctionTypeVar>(subTy))
+    {
+        // Ok.  Do nothing.  forall functions F, F <: function
+    }
+
     else if (log.getMutable<FunctionTypeVar>(superTy) && log.getMutable<FunctionTypeVar>(subTy))
         tryUnifyFunctions(subTy, superTy, isFunctionCall);
 
@@ -559,7 +559,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
         tryUnifyNegationWithType(subTy, superTy);
 
     else
-        reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+        reportError(location, TypeMismatch{superTy, subTy});
 
     if (cacheEnabled)
         cacheResult(subTy, superTy, errorCount);
@@ -633,9 +633,9 @@ void Unifier::tryUnifyUnionWithType(TypeId subTy, const UnionTypeVar* subUnion,
     else if (failed)
     {
         if (firstFailedOption)
-            reportError(TypeError{location, TypeMismatch{superTy, subTy, "Not all union options are compatible.", *firstFailedOption}});
+            reportError(location, TypeMismatch{superTy, subTy, "Not all union options are compatible.", *firstFailedOption});
         else
-            reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+            reportError(location, TypeMismatch{superTy, subTy});
     }
 }
 
@@ -734,7 +734,7 @@ void Unifier::tryUnifyTypeWithUnion(TypeId subTy, TypeId superTy, const UnionTyp
         const NormalizedType* subNorm = normalizer->normalize(subTy);
         const NormalizedType* superNorm = normalizer->normalize(superTy);
         if (!subNorm || !superNorm)
-            reportError(TypeError{location, UnificationTooComplex{}});
+            reportError(location, UnificationTooComplex{});
         else if ((failedOptionCount == 1 || foundHeuristic) && failedOption)
             tryUnifyNormalizedTypes(subTy, superTy, *subNorm, *superNorm, "None of the union options are compatible. For example:", *failedOption);
         else
@@ -743,9 +743,9 @@ void Unifier::tryUnifyTypeWithUnion(TypeId subTy, TypeId superTy, const UnionTyp
     else if (!found)
     {
         if ((failedOptionCount == 1 || foundHeuristic) && failedOption)
-            reportError(TypeError{location, TypeMismatch{superTy, subTy, "None of the union options are compatible. For example:", *failedOption}});
+            reportError(location, TypeMismatch{superTy, subTy, "None of the union options are compatible. For example:", *failedOption});
         else
-            reportError(TypeError{location, TypeMismatch{superTy, subTy, "none of the union options are compatible"}});
+            reportError(location, TypeMismatch{superTy, subTy, "none of the union options are compatible"});
     }
 }
 
@@ -774,7 +774,7 @@ void Unifier::tryUnifyTypeWithIntersection(TypeId subTy, TypeId superTy, const I
     if (unificationTooComplex)
         reportError(*unificationTooComplex);
     else if (firstFailedOption)
-        reportError(TypeError{location, TypeMismatch{superTy, subTy, "Not all intersection parts are compatible.", *firstFailedOption}});
+        reportError(location, TypeMismatch{superTy, subTy, "Not all intersection parts are compatible.", *firstFailedOption});
 }
 
 void Unifier::tryUnifyIntersectionWithType(TypeId subTy, const IntersectionTypeVar* uv, TypeId superTy, bool cacheEnabled, bool isFunctionCall)
@@ -832,11 +832,11 @@ void Unifier::tryUnifyIntersectionWithType(TypeId subTy, const IntersectionTypeV
         if (subNorm && superNorm)
             tryUnifyNormalizedTypes(subTy, superTy, *subNorm, *superNorm, "none of the intersection parts are compatible");
         else
-            reportError(TypeError{location, UnificationTooComplex{}});
+            reportError(location, UnificationTooComplex{});
     }
     else if (!found)
     {
-        reportError(TypeError{location, TypeMismatch{superTy, subTy, "none of the intersection parts are compatible"}});
+        reportError(location, TypeMismatch{superTy, subTy, "none of the intersection parts are compatible"});
     }
 }
 
@@ -848,37 +848,37 @@ void Unifier::tryUnifyNormalizedTypes(
     if (get<UnknownTypeVar>(superNorm.tops) || get<AnyTypeVar>(superNorm.tops) || get<AnyTypeVar>(subNorm.tops))
         return;
     else if (get<UnknownTypeVar>(subNorm.tops))
-        return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+        return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     if (get<ErrorTypeVar>(subNorm.errors))
         if (!get<ErrorTypeVar>(superNorm.errors))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     if (get<PrimitiveTypeVar>(subNorm.booleans))
     {
         if (!get<PrimitiveTypeVar>(superNorm.booleans))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
     }
     else if (const SingletonTypeVar* stv = get<SingletonTypeVar>(subNorm.booleans))
     {
         if (!get<PrimitiveTypeVar>(superNorm.booleans) && stv != get<SingletonTypeVar>(superNorm.booleans))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
     }
 
     if (get<PrimitiveTypeVar>(subNorm.nils))
         if (!get<PrimitiveTypeVar>(superNorm.nils))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     if (get<PrimitiveTypeVar>(subNorm.numbers))
         if (!get<PrimitiveTypeVar>(superNorm.numbers))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     if (!isSubtype(subNorm.strings, superNorm.strings))
-        return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+        return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     if (get<PrimitiveTypeVar>(subNorm.threads))
         if (!get<PrimitiveTypeVar>(superNorm.errors))
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
 
     for (TypeId subClass : subNorm.classes)
     {
@@ -894,7 +894,7 @@ void Unifier::tryUnifyNormalizedTypes(
             }
         }
         if (!found)
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
     }
 
     for (TypeId subTable : subNorm.tables)
@@ -919,21 +919,19 @@ void Unifier::tryUnifyNormalizedTypes(
                 return reportError(*e);
         }
         if (!found)
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
     }
 
-    if (subNorm.functions)
+    if (!subNorm.functions.isNever())
     {
-        if (!superNorm.functions)
+        if (superNorm.functions.isNever())
-            return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+            return reportError(location, TypeMismatch{superTy, subTy, reason, error});
-        if (superNorm.functions->empty())
+        for (TypeId superFun : *superNorm.functions.parts)
-            return;
-        for (TypeId superFun : *superNorm.functions)
         {
             Unifier innerState = makeChildUnifier();
             const FunctionTypeVar* superFtv = get<FunctionTypeVar>(superFun);
             if (!superFtv)
-                return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+                return reportError(location, TypeMismatch{superTy, subTy, reason, error});
             TypePackId tgt = innerState.tryApplyOverloadedFunction(subTy, subNorm.functions, superFtv->argTypes);
             innerState.tryUnify_(tgt, superFtv->retTypes);
             if (innerState.errors.empty())
@@ -941,7 +939,7 @@ void Unifier::tryUnifyNormalizedTypes(
             else if (auto e = hasUnificationTooComplex(innerState.errors))
                 return reportError(*e);
             else
-                return reportError(TypeError{location, TypeMismatch{superTy, subTy, reason, error}});
+                return reportError(location, TypeMismatch{superTy, subTy, reason, error});
         }
     }
 
@@ -959,15 +957,15 @@ void Unifier::tryUnifyNormalizedTypes(
 
 TypePackId Unifier::tryApplyOverloadedFunction(TypeId function, const NormalizedFunctionType& overloads, TypePackId args)
 {
-    if (!overloads || overloads->empty())
+    if (overloads.isNever())
     {
-        reportError(TypeError{location, CannotCallNonFunction{function}});
+        reportError(location, CannotCallNonFunction{function});
         return singletonTypes->errorRecoveryTypePack();
     }
 
     std::optional<TypePackId> result;
     const FunctionTypeVar* firstFun = nullptr;
-    for (TypeId overload : *overloads)
+    for (TypeId overload : *overloads.parts)
     {
         if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(overload))
         {
@@ -1015,12 +1013,12 @@ TypePackId Unifier::tryApplyOverloadedFunction(TypeId function, const Normalized
         // TODO: better error reporting?
         // The logic for error reporting overload resolution
         // is currently over in TypeInfer.cpp, should we move it?
-        reportError(TypeError{location, GenericError{"No matching overload."}});
+        reportError(location, GenericError{"No matching overload."});
         return singletonTypes->errorRecoveryTypePack(firstFun->retTypes);
     }
     else
     {
-        reportError(TypeError{location, CannotCallNonFunction{function}});
+        reportError(location, CannotCallNonFunction{function});
         return singletonTypes->errorRecoveryTypePack();
     }
 }
@@ -1199,7 +1197,7 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
 
     if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
     {
-        reportError(TypeError{location, UnificationTooComplex{}});
+        reportError(location, UnificationTooComplex{});
         return;
     }
 
@@ -1372,7 +1370,7 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
                 size_t actualSize = size(subTp);
                 if (ctx == CountMismatch::FunctionResult || ctx == CountMismatch::ExprListResult)
                     std::swap(expectedSize, actualSize);
-                reportError(TypeError{location, CountMismatch{expectedSize, std::nullopt, actualSize, ctx}});
+                reportError(location, CountMismatch{expectedSize, std::nullopt, actualSize, ctx});
 
                 while (superIter.good())
                 {
@@ -1394,9 +1392,9 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
     else
     {
         if (FFlag::LuauReportTypeMismatchForTypePackUnificationFailure)
-            reportError(TypeError{location, TypePackMismatch{subTp, superTp}});
+            reportError(location, TypePackMismatch{subTp, superTp});
         else
-            reportError(TypeError{location, GenericError{"Failed to unify type packs"}});
+            reportError(location, GenericError{"Failed to unify type packs"});
     }
 }
 
@@ -1408,7 +1406,7 @@ void Unifier::tryUnifyPrimitives(TypeId subTy, TypeId superTy)
         ice("passed non primitive types to unifyPrimitives");
 
     if (superPrim->type != subPrim->type)
-        reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+        reportError(location, TypeMismatch{superTy, subTy});
 }
 
 void Unifier::tryUnifySingletons(TypeId subTy, TypeId superTy)
@@ -1429,7 +1427,7 @@ void Unifier::tryUnifySingletons(TypeId subTy, TypeId superTy)
     if (superPrim && superPrim->type == PrimitiveTypeVar::String && get<StringSingleton>(subSingleton) && variance == Covariant)
         return;
 
-    reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+    reportError(location, TypeMismatch{superTy, subTy});
 }
 
 void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCall)
@@ -1465,21 +1463,21 @@ void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCal
         }
         else
         {
-            reportError(TypeError{location, UnificationTooComplex{}});
+            reportError(location, UnificationTooComplex{});
         }
     }
     else if (numGenerics != subFunction->generics.size())
     {
         numGenerics = std::min(superFunction->generics.size(), subFunction->generics.size());
 
-        reportError(TypeError{location, TypeMismatch{superTy, subTy, "different number of generic type parameters"}});
+        reportError(location, TypeMismatch{superTy, subTy, "different number of generic type parameters"});
     }
 
     if (numGenericPacks != subFunction->genericPacks.size())
     {
         numGenericPacks = std::min(superFunction->genericPacks.size(), subFunction->genericPacks.size());
 
-        reportError(TypeError{location, TypeMismatch{superTy, subTy, "different number of generic type pack parameters"}});
+        reportError(location, TypeMismatch{superTy, subTy, "different number of generic type pack parameters"});
     }
 
     for (size_t i = 0; i < numGenerics; i++)
@@ -1506,11 +1504,10 @@ void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCal
         if (auto e = hasUnificationTooComplex(innerState.errors))
             reportError(*e);
         else if (!innerState.errors.empty() && innerState.firstPackErrorPos)
-            reportError(
+            reportError(location, TypeMismatch{superTy, subTy, format("Argument #%d type is not compatible.", *innerState.firstPackErrorPos),
-                TypeError{location, TypeMismatch{superTy, subTy, format("Argument #%d type is not compatible.", *innerState.firstPackErrorPos),
+                                      innerState.errors.front()});
-                                        innerState.errors.front()}});
         else if (!innerState.errors.empty())
-            reportError(TypeError{location, TypeMismatch{superTy, subTy, "", innerState.errors.front()}});
+            reportError(location, TypeMismatch{superTy, subTy, "", innerState.errors.front()});
 
         innerState.ctx = CountMismatch::FunctionResult;
         innerState.tryUnify_(subFunction->retTypes, superFunction->retTypes);
@@ -1520,13 +1517,12 @@ void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCal
             if (auto e = hasUnificationTooComplex(innerState.errors))
                 reportError(*e);
             else if (!innerState.errors.empty() && size(superFunction->retTypes) == 1 && finite(superFunction->retTypes))
-                reportError(TypeError{location, TypeMismatch{superTy, subTy, "Return type is not compatible.", innerState.errors.front()}});
+                reportError(location, TypeMismatch{superTy, subTy, "Return type is not compatible.", innerState.errors.front()});
             else if (!innerState.errors.empty() && innerState.firstPackErrorPos)
-                reportError(
+                reportError(location, TypeMismatch{superTy, subTy, format("Return #%d type is not compatible.", *innerState.firstPackErrorPos),
-                    TypeError{location, TypeMismatch{superTy, subTy, format("Return #%d type is not compatible.", *innerState.firstPackErrorPos),
+                                          innerState.errors.front()});
-                                            innerState.errors.front()}});
             else if (!innerState.errors.empty())
-                reportError(TypeError{location, TypeMismatch{superTy, subTy, "", innerState.errors.front()}});
+                reportError(location, TypeMismatch{superTy, subTy, "", innerState.errors.front()});
         }
 
         log.concat(std::move(innerState.log));
@@ -1608,7 +1604,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
             }
             else
             {
-                reportError(TypeError{location, UnificationTooComplex{}});
+                reportError(location, UnificationTooComplex{});
             }
         }
     }
@@ -1626,7 +1622,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
 
         if (!missingProperties.empty())
         {
-            reportError(TypeError{location, MissingProperties{superTy, subTy, std::move(missingProperties)}});
+            reportError(location, MissingProperties{superTy, subTy, std::move(missingProperties)});
             return;
         }
     }
@@ -1644,7 +1640,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
 
         if (!extraProperties.empty())
         {
-            reportError(TypeError{location, MissingProperties{superTy, subTy, std::move(extraProperties), MissingProperties::Extra}});
+            reportError(location, MissingProperties{superTy, subTy, std::move(extraProperties), MissingProperties::Extra});
             return;
         }
     }
@@ -1825,13 +1821,13 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
 
     if (!missingProperties.empty())
     {
-        reportError(TypeError{location, MissingProperties{superTy, subTy, std::move(missingProperties)}});
+        reportError(location, MissingProperties{superTy, subTy, std::move(missingProperties)});
         return;
     }
 
     if (!extraProperties.empty())
     {
-        reportError(TypeError{location, MissingProperties{superTy, subTy, std::move(extraProperties), MissingProperties::Extra}});
+        reportError(location, MissingProperties{superTy, subTy, std::move(extraProperties), MissingProperties::Extra});
         return;
     }
 
@@ -1867,14 +1863,14 @@ void Unifier::tryUnifyScalarShape(TypeId subTy, TypeId superTy, bool reversed)
         std::swap(subTy, superTy);
 
     if (auto ttv = log.get<TableTypeVar>(superTy); !ttv || ttv->state != TableState::Free)
-        return reportError(TypeError{location, TypeMismatch{osuperTy, osubTy}});
+        return reportError(location, TypeMismatch{osuperTy, osubTy});
 
     auto fail = [&](std::optional<TypeError> e) {
         std::string reason = "The former's metatable does not satisfy the requirements.";
         if (e)
-            reportError(TypeError{location, TypeMismatch{osuperTy, osubTy, reason, *e}});
+            reportError(location, TypeMismatch{osuperTy, osubTy, reason, *e});
         else
-            reportError(TypeError{location, TypeMismatch{osuperTy, osubTy, reason}});
+            reportError(location, TypeMismatch{osuperTy, osubTy, reason});
     };
 
     // Given t1 where t1 = { lower: (t1) -> (a, b...) }
@@ -1906,7 +1902,7 @@ void Unifier::tryUnifyScalarShape(TypeId subTy, TypeId superTy, bool reversed)
         }
     }
 
-    reportError(TypeError{location, TypeMismatch{osuperTy, osubTy}});
+    reportError(location, TypeMismatch{osuperTy, osubTy});
     return;
 }
 
@@ -1947,7 +1943,7 @@ void Unifier::tryUnifyWithMetatable(TypeId subTy, TypeId superTy, bool reversed)
         if (auto e = hasUnificationTooComplex(innerState.errors))
             reportError(*e);
         else if (!innerState.errors.empty())
-            reportError(TypeError{location, TypeMismatch{reversed ? subTy : superTy, reversed ? superTy : subTy, "", innerState.errors.front()}});
+            reportError(location, TypeMismatch{reversed ? subTy : superTy, reversed ? superTy : subTy, "", innerState.errors.front()});
 
         log.concat(std::move(innerState.log));
     }
@@ -2024,9 +2020,9 @@ void Unifier::tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed)
 
     auto fail = [&]() {
         if (!reversed)
-            reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+            reportError(location, TypeMismatch{superTy, subTy});
         else
-            reportError(TypeError{location, TypeMismatch{subTy, superTy}});
+            reportError(location, TypeMismatch{subTy, superTy});
     };
 
     const ClassTypeVar* superClass = get<ClassTypeVar>(superTy);
@@ -2071,7 +2067,7 @@ void Unifier::tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed)
             if (!classProp)
             {
                 ok = false;
-                reportError(TypeError{location, UnknownProperty{superTy, propName}});
+                reportError(location, UnknownProperty{superTy, propName});
             }
             else
             {
@@ -2095,7 +2091,7 @@ void Unifier::tryUnifyWithClass(TypeId subTy, TypeId superTy, bool reversed)
         {
             ok = false;
             std::string msg = "Class " + superClass->name + " does not have an indexer";
-            reportError(TypeError{location, GenericError{msg}});
+            reportError(location, GenericError{msg});
         }
 
         if (!ok)
@@ -2116,13 +2112,13 @@ void Unifier::tryUnifyTypeWithNegation(TypeId subTy, TypeId superTy)
     const NormalizedType* subNorm = normalizer->normalize(subTy);
     const NormalizedType* superNorm = normalizer->normalize(superTy);
     if (!subNorm || !superNorm)
-        return reportError(TypeError{location, UnificationTooComplex{}});
+        return reportError(location, UnificationTooComplex{});
 
     // T </: ~U iff T <: U
     Unifier state = makeChildUnifier();
     state.tryUnifyNormalizedTypes(subTy, superTy, *subNorm, *superNorm, "");
     if (state.errors.empty())
-        reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+        reportError(location, TypeMismatch{superTy, subTy});
 }
 
 void Unifier::tryUnifyNegationWithType(TypeId subTy, TypeId superTy)
@@ -2132,7 +2128,7 @@ void Unifier::tryUnifyNegationWithType(TypeId subTy, TypeId superTy)
         ice("tryUnifyNegationWithType subTy must be a negation type");
 
     // TODO: ~T </: U iff T <: U
-    reportError(TypeError{location, TypeMismatch{superTy, subTy}});
+    reportError(location, TypeMismatch{superTy, subTy});
 }
 
 static void queueTypePack(std::vector<TypeId>& queue, DenseHashSet<TypePackId>& seenTypePacks, Unifier& state, TypePackId a, TypePackId anyTypePack)
@@ -2195,7 +2191,7 @@ void Unifier::tryUnifyVariadics(TypePackId subTp, TypePackId superTp, bool rever
             }
             else if (get<Unifiable::Generic>(tail))
             {
-                reportError(TypeError{location, GenericError{"Cannot unify variadic and generic packs"}});
+                reportError(location, GenericError{"Cannot unify variadic and generic packs"});
             }
             else if (get<Unifiable::Error>(tail))
             {
@@ -2209,7 +2205,7 @@ void Unifier::tryUnifyVariadics(TypePackId subTp, TypePackId superTp, bool rever
     }
     else
     {
-        reportError(TypeError{location, GenericError{"Failed to unify variadic packs"}});
+        reportError(location, GenericError{"Failed to unify variadic packs"});
     }
 }
 
@@ -2351,7 +2347,7 @@ bool Unifier::occursCheck(DenseHashSet<TypeId>& seen, TypeId needle, TypeId hays
 
     if (needle == haystack)
     {
-        reportError(TypeError{location, OccursCheckFailed{}});
+        reportError(location, OccursCheckFailed{});
         log.replace(needle, *singletonTypes->errorRecoveryType());
 
         return true;
@@ -2402,7 +2398,7 @@ bool Unifier::occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, Typ
     {
         if (needle == haystack)
         {
-            reportError(TypeError{location, OccursCheckFailed{}});
+            reportError(location, OccursCheckFailed{});
             log.replace(needle, *singletonTypes->errorRecoveryTypePack());
 
             return true;
@@ -2423,18 +2419,31 @@ bool Unifier::occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, Typ
 Unifier Unifier::makeChildUnifier()
 {
     Unifier u = Unifier{normalizer, mode, scope, location, variance, &log};
-    u.anyIsTop = anyIsTop;
     u.normalize = normalize;
+    u.useScopes = useScopes;
     return u;
 }
 
 // A utility function that appends the given error to the unifier's error log.
 // This allows setting a breakpoint wherever the unifier reports an error.
+//
+// Note: report error accepts its arguments by value intentionally to reduce the stack usage of functions which call `reportError`.
+void Unifier::reportError(Location location, TypeErrorData data)
+{
+    errors.emplace_back(std::move(location), std::move(data));
+}
+
+// A utility function that appends the given error to the unifier's error log.
+// This allows setting a breakpoint wherever the unifier reports an error.
+//
+// Note: to conserve stack space in calling functions it is generally preferred to call `Unifier::reportError(Location location, TypeErrorData data)`
+// instead of this method.
 void Unifier::reportError(TypeError err)
 {
     errors.push_back(std::move(err));
 }
 
+
 bool Unifier::isNonstrictMode() const
 {
     return (mode == Mode::Nonstrict) || (mode == Mode::NoCheck);
@@ -2445,7 +2454,7 @@ void Unifier::checkChildUnifierTypeMismatch(const ErrorVec& innerErrors, TypeId
     if (auto e = hasUnificationTooComplex(innerErrors))
         reportError(*e);
     else if (!innerErrors.empty())
-        reportError(TypeError{location, TypeMismatch{wantedType, givenType}});
+        reportError(location, TypeMismatch{wantedType, givenType});
 }
 
 void Unifier::checkChildUnifierTypeMismatch(const ErrorVec& innerErrors, const std::string& prop, TypeId wantedType, TypeId givenType)

Ast/src/Parser.cpp

@@ -25,6 +25,7 @@ LUAU_DYNAMIC_FASTFLAGVARIABLE(LuaReportParseIntegerIssues, false)
 LUAU_FASTFLAGVARIABLE(LuauInterpolatedStringBaseSupport, false)
 
 LUAU_FASTFLAGVARIABLE(LuauCommaParenWarnings, false)
+LUAU_FASTFLAGVARIABLE(LuauTableConstructorRecovery, false)
 
 bool lua_telemetry_parsed_out_of_range_bin_integer = false;
 bool lua_telemetry_parsed_out_of_range_hex_integer = false;
@@ -2310,9 +2311,13 @@ AstExpr* Parser::parseTableConstructor()
 
     MatchLexeme matchBrace = lexer.current();
     expectAndConsume('{', "table literal");
+    unsigned lastElementIndent = 0;
 
     while (lexer.current().type != '}')
     {
+        if (FFlag::LuauTableConstructorRecovery)
+            lastElementIndent = lexer.current().location.begin.column;
+
         if (lexer.current().type == '[')
         {
             MatchLexeme matchLocationBracket = lexer.current();
@@ -2357,10 +2362,14 @@ AstExpr* Parser::parseTableConstructor()
         {
             nextLexeme();
         }
-        else
+        else if (FFlag::LuauTableConstructorRecovery && (lexer.current().type == '[' || lexer.current().type == Lexeme::Name) &&
+                 lexer.current().location.begin.column == lastElementIndent)
         {
-            if (lexer.current().type != '}')
+            report(lexer.current().location, "Expected ',' after table constructor element");
-                break;
+        }
+        else if (lexer.current().type != '}')
+        {
+            break;
         }
     }
 

CLI/Repl.cpp

@@ -978,7 +978,8 @@ int replMain(int argc, char** argv)
         if (compileFormat == CompileFormat::Null)
             printf("Compiled %d KLOC into %d KB bytecode\n", int(stats.lines / 1000), int(stats.bytecode / 1024));
         else if (compileFormat == CompileFormat::CodegenNull)
-            printf("Compiled %d KLOC into %d KB bytecode => %d KB native code\n", int(stats.lines / 1000), int(stats.bytecode / 1024), int(stats.codegen / 1024));
+            printf("Compiled %d KLOC into %d KB bytecode => %d KB native code\n", int(stats.lines / 1000), int(stats.bytecode / 1024),
+                int(stats.codegen / 1024));
 
         return failed ? 1 : 0;
     }

CodeGen/include/Luau/AddressA64.h

@@ -0,0 +1,52 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/RegisterA64.h"
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+enum class AddressKindA64 : uint8_t
+{
+    imm, // reg + imm
+    reg, // reg + reg
+
+    // TODO:
+    // reg + reg << shift
+    // reg + sext(reg) << shift
+    // reg + uext(reg) << shift
+    // pc + offset
+};
+
+struct AddressA64
+{
+    AddressA64(RegisterA64 base, int off = 0)
+        : kind(AddressKindA64::imm)
+        , base(base)
+        , offset(xzr)
+        , data(off)
+    {
+        LUAU_ASSERT(base.kind == KindA64::x);
+        LUAU_ASSERT(off >= 0 && off < 4096);
+    }
+
+    AddressA64(RegisterA64 base, RegisterA64 offset)
+        : kind(AddressKindA64::reg)
+        , base(base)
+        , offset(offset)
+        , data(0)
+    {
+        LUAU_ASSERT(base.kind == KindA64::x);
+        LUAU_ASSERT(offset.kind == KindA64::x);
+    }
+
+    AddressKindA64 kind;
+    RegisterA64 base;
+    RegisterA64 offset;
+    int data;
+};
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/include/Luau/AssemblyBuilderA64.h

@@ -0,0 +1,144 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/RegisterA64.h"
+#include "Luau/AddressA64.h"
+#include "Luau/ConditionA64.h"
+#include "Luau/Label.h"
+
+#include <string>
+#include <vector>
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+class AssemblyBuilderA64
+{
+public:
+    explicit AssemblyBuilderA64(bool logText);
+    ~AssemblyBuilderA64();
+
+    // Moves
+    void mov(RegisterA64 dst, RegisterA64 src);
+    void mov(RegisterA64 dst, uint16_t src, int shift = 0);
+    void movk(RegisterA64 dst, uint16_t src, int shift = 0);
+
+    // Arithmetics
+    void add(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift = 0);
+    void add(RegisterA64 dst, RegisterA64 src1, int src2);
+    void sub(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift = 0);
+    void sub(RegisterA64 dst, RegisterA64 src1, int src2);
+    void neg(RegisterA64 dst, RegisterA64 src);
+
+    // Comparisons
+    // Note: some arithmetic instructions also have versions that update flags (ADDS etc) but we aren't using them atm
+    // TODO: add cmp
+
+    // Binary
+    // Note: shifted-register support and bitfield operations are omitted for simplicity
+    // TODO: support immediate arguments (they have odd encoding and forbid many values)
+    // TODO: support not variants for and/or/eor (required to support not...)
+    void and_(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void orr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void eor(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void lsl(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void lsr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void asr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void ror(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2);
+    void clz(RegisterA64 dst, RegisterA64 src);
+    void rbit(RegisterA64 dst, RegisterA64 src);
+
+    // Load
+    // Note: paired loads are currently omitted for simplicity
+    void ldr(RegisterA64 dst, AddressA64 src);
+    void ldrb(RegisterA64 dst, AddressA64 src);
+    void ldrh(RegisterA64 dst, AddressA64 src);
+    void ldrsb(RegisterA64 dst, AddressA64 src);
+    void ldrsh(RegisterA64 dst, AddressA64 src);
+    void ldrsw(RegisterA64 dst, AddressA64 src);
+
+    // Store
+    void str(RegisterA64 src, AddressA64 dst);
+    void strb(RegisterA64 src, AddressA64 dst);
+    void strh(RegisterA64 src, AddressA64 dst);
+
+    // Control flow
+    // Note: tbz/tbnz are currently not supported because they have 15-bit offsets and we don't support branch thunks
+    void b(ConditionA64 cond, Label& label);
+    void cbz(RegisterA64 src, Label& label);
+    void cbnz(RegisterA64 src, Label& label);
+    void ret();
+
+    // Run final checks
+    bool finalize();
+
+    // Places a label at current location and returns it
+    Label setLabel();
+
+    // Assigns label position to the current location
+    void setLabel(Label& label);
+
+    void logAppend(const char* fmt, ...) LUAU_PRINTF_ATTR(2, 3);
+
+    uint32_t getCodeSize() const;
+
+    // Resulting data and code that need to be copied over one after the other
+    // The *end* of 'data' has to be aligned to 16 bytes, this will also align 'code'
+    std::vector<uint8_t> data;
+    std::vector<uint32_t> code;
+
+    std::string text;
+
+    const bool logText = false;
+
+private:
+    // Instruction archetypes
+    void place0(const char* name, uint32_t word);
+    void placeSR3(const char* name, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, uint8_t op, int shift = 0);
+    void placeSR2(const char* name, RegisterA64 dst, RegisterA64 src, uint8_t op);
+    void placeR3(const char* name, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, uint8_t op, uint8_t op2);
+    void placeR1(const char* name, RegisterA64 dst, RegisterA64 src, uint32_t op);
+    void placeI12(const char* name, RegisterA64 dst, RegisterA64 src1, int src2, uint8_t op);
+    void placeI16(const char* name, RegisterA64 dst, int src, uint8_t op, int shift = 0);
+    void placeA(const char* name, RegisterA64 dst, AddressA64 src, uint8_t op, uint8_t size);
+    void placeBC(const char* name, Label& label, uint8_t op, uint8_t cond);
+    void placeBR(const char* name, Label& label, uint8_t op, RegisterA64 cond);
+
+    void place(uint32_t word);
+    void placeLabel(Label& label);
+
+    void commit();
+    LUAU_NOINLINE void extend();
+
+    // Data
+    size_t allocateData(size_t size, size_t align);
+
+    // Logging of assembly in text form
+    LUAU_NOINLINE void log(const char* opcode);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift = 0);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 dst, RegisterA64 src1, int src2);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 dst, RegisterA64 src);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 dst, int src, int shift = 0);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 dst, AddressA64 src);
+    LUAU_NOINLINE void log(const char* opcode, RegisterA64 src, Label label);
+    LUAU_NOINLINE void log(const char* opcode, Label label);
+    LUAU_NOINLINE void log(Label label);
+    LUAU_NOINLINE void log(RegisterA64 reg);
+    LUAU_NOINLINE void log(AddressA64 addr);
+
+    uint32_t nextLabel = 1;
+    std::vector<Label> pendingLabels;
+    std::vector<uint32_t> labelLocations;
+
+    bool finalized = false;
+
+    size_t dataPos = 0;
+
+    uint32_t* codePos = nullptr;
+    uint32_t* codeEnd = nullptr;
+};
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/include/Luau/AssemblyBuilderX64.h

@@ -2,8 +2,8 @@
 #pragma once
 
 #include "Luau/Common.h"
-#include "Luau/Condition.h"
 #include "Luau/Label.h"
+#include "Luau/ConditionX64.h"
 #include "Luau/OperandX64.h"
 #include "Luau/RegisterX64.h"
 
@@ -84,7 +84,7 @@ public:
     void ret();
 
     // Control flow
-    void jcc(Condition cond, Label& label);
+    void jcc(ConditionX64 cond, Label& label);
     void jmp(Label& label);
     void jmp(OperandX64 op);
 

CodeGen/include/Luau/ConditionA64.h

@@ -0,0 +1,37 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+enum class ConditionA64
+{
+    Equal,
+    NotEqual,
+
+    CarrySet,
+    CarryClear,
+
+    Minus,
+    Plus,
+
+    Overflow,
+    NoOverflow,
+
+    UnsignedGreater,
+    UnsignedLessEqual,
+
+    GreaterEqual,
+    Less,
+    Greater,
+    LessEqual,
+
+    Always,
+
+    Count
+};
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/include/Luau/ConditionX64.h

@@ -6,7 +6,7 @@ namespace Luau
 namespace CodeGen
 {
 
-enum class Condition
+enum class ConditionX64 : uint8_t
 {
     Overflow,
     NoOverflow,

CodeGen/include/Luau/OperandX64.h

@@ -61,7 +61,7 @@ struct OperandX64
     constexpr OperandX64 operator[](OperandX64&& addr) const
     {
         LUAU_ASSERT(cat == CategoryX64::mem);
-        LUAU_ASSERT(memSize != SizeX64::none && index == noreg && scale == 1 && base == noreg && imm == 0);
+        LUAU_ASSERT(index == noreg && scale == 1 && base == noreg && imm == 0);
         LUAU_ASSERT(addr.memSize == SizeX64::none);
 
         addr.cat = CategoryX64::mem;
@@ -70,13 +70,13 @@ struct OperandX64
     }
 };
 
+constexpr OperandX64 addr{SizeX64::none, noreg, 1, noreg, 0};
 constexpr OperandX64 byte{SizeX64::byte, noreg, 1, noreg, 0};
 constexpr OperandX64 word{SizeX64::word, noreg, 1, noreg, 0};
 constexpr OperandX64 dword{SizeX64::dword, noreg, 1, noreg, 0};
 constexpr OperandX64 qword{SizeX64::qword, noreg, 1, noreg, 0};
 constexpr OperandX64 xmmword{SizeX64::xmmword, noreg, 1, noreg, 0};
 constexpr OperandX64 ymmword{SizeX64::ymmword, noreg, 1, noreg, 0};
-constexpr OperandX64 ptr{sizeof(void*) == 4 ? SizeX64::dword : SizeX64::qword, noreg, 1, noreg, 0};
 
 constexpr OperandX64 operator*(RegisterX64 reg, uint8_t scale)
 {

CodeGen/include/Luau/RegisterA64.h

@@ -0,0 +1,105 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Common.h"
+
+#include <stdint.h>
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+enum class KindA64 : uint8_t
+{
+    none,
+    w, // 32-bit GPR
+    x, // 64-bit GPR
+};
+
+struct RegisterA64
+{
+    KindA64 kind : 3;
+    uint8_t index : 5;
+
+    constexpr bool operator==(RegisterA64 rhs) const
+    {
+        return kind == rhs.kind && index == rhs.index;
+    }
+
+    constexpr bool operator!=(RegisterA64 rhs) const
+    {
+        return !(*this == rhs);
+    }
+};
+
+constexpr RegisterA64 w0{KindA64::w, 0};
+constexpr RegisterA64 w1{KindA64::w, 1};
+constexpr RegisterA64 w2{KindA64::w, 2};
+constexpr RegisterA64 w3{KindA64::w, 3};
+constexpr RegisterA64 w4{KindA64::w, 4};
+constexpr RegisterA64 w5{KindA64::w, 5};
+constexpr RegisterA64 w6{KindA64::w, 6};
+constexpr RegisterA64 w7{KindA64::w, 7};
+constexpr RegisterA64 w8{KindA64::w, 8};
+constexpr RegisterA64 w9{KindA64::w, 9};
+constexpr RegisterA64 w10{KindA64::w, 10};
+constexpr RegisterA64 w11{KindA64::w, 11};
+constexpr RegisterA64 w12{KindA64::w, 12};
+constexpr RegisterA64 w13{KindA64::w, 13};
+constexpr RegisterA64 w14{KindA64::w, 14};
+constexpr RegisterA64 w15{KindA64::w, 15};
+constexpr RegisterA64 w16{KindA64::w, 16};
+constexpr RegisterA64 w17{KindA64::w, 17};
+constexpr RegisterA64 w18{KindA64::w, 18};
+constexpr RegisterA64 w19{KindA64::w, 19};
+constexpr RegisterA64 w20{KindA64::w, 20};
+constexpr RegisterA64 w21{KindA64::w, 21};
+constexpr RegisterA64 w22{KindA64::w, 22};
+constexpr RegisterA64 w23{KindA64::w, 23};
+constexpr RegisterA64 w24{KindA64::w, 24};
+constexpr RegisterA64 w25{KindA64::w, 25};
+constexpr RegisterA64 w26{KindA64::w, 26};
+constexpr RegisterA64 w27{KindA64::w, 27};
+constexpr RegisterA64 w28{KindA64::w, 28};
+constexpr RegisterA64 w29{KindA64::w, 29};
+constexpr RegisterA64 w30{KindA64::w, 30};
+constexpr RegisterA64 wzr{KindA64::w, 31};
+
+constexpr RegisterA64 x0{KindA64::x, 0};
+constexpr RegisterA64 x1{KindA64::x, 1};
+constexpr RegisterA64 x2{KindA64::x, 2};
+constexpr RegisterA64 x3{KindA64::x, 3};
+constexpr RegisterA64 x4{KindA64::x, 4};
+constexpr RegisterA64 x5{KindA64::x, 5};
+constexpr RegisterA64 x6{KindA64::x, 6};
+constexpr RegisterA64 x7{KindA64::x, 7};
+constexpr RegisterA64 x8{KindA64::x, 8};
+constexpr RegisterA64 x9{KindA64::x, 9};
+constexpr RegisterA64 x10{KindA64::x, 10};
+constexpr RegisterA64 x11{KindA64::x, 11};
+constexpr RegisterA64 x12{KindA64::x, 12};
+constexpr RegisterA64 x13{KindA64::x, 13};
+constexpr RegisterA64 x14{KindA64::x, 14};
+constexpr RegisterA64 x15{KindA64::x, 15};
+constexpr RegisterA64 x16{KindA64::x, 16};
+constexpr RegisterA64 x17{KindA64::x, 17};
+constexpr RegisterA64 x18{KindA64::x, 18};
+constexpr RegisterA64 x19{KindA64::x, 19};
+constexpr RegisterA64 x20{KindA64::x, 20};
+constexpr RegisterA64 x21{KindA64::x, 21};
+constexpr RegisterA64 x22{KindA64::x, 22};
+constexpr RegisterA64 x23{KindA64::x, 23};
+constexpr RegisterA64 x24{KindA64::x, 24};
+constexpr RegisterA64 x25{KindA64::x, 25};
+constexpr RegisterA64 x26{KindA64::x, 26};
+constexpr RegisterA64 x27{KindA64::x, 27};
+constexpr RegisterA64 x28{KindA64::x, 28};
+constexpr RegisterA64 x29{KindA64::x, 29};
+constexpr RegisterA64 x30{KindA64::x, 30};
+constexpr RegisterA64 xzr{KindA64::x, 31};
+
+constexpr RegisterA64 sp{KindA64::none, 31};
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/include/Luau/RegisterX64.h

@@ -128,5 +128,10 @@ constexpr RegisterX64 dwordReg(RegisterX64 reg)
     return RegisterX64{SizeX64::dword, reg.index};
 }
 
+constexpr RegisterX64 qwordReg(RegisterX64 reg)
+{
+    return RegisterX64{SizeX64::qword, reg.index};
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/AssemblyBuilderA64.cpp

@@ -0,0 +1,607 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/AssemblyBuilderA64.h"
+
+#include "ByteUtils.h"
+
+#include <stdarg.h>
+
+namespace Luau
+{
+namespace CodeGen
+{
+
+static const uint8_t codeForCondition[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14};
+static_assert(sizeof(codeForCondition) / sizeof(codeForCondition[0]) == size_t(ConditionA64::Count), "all conditions have to be covered");
+
+static const char* textForCondition[] = {
+    "b.eq", "b.ne", "b.cs", "b.cc", "b.mi", "b.pl", "b.vs", "b.vc", "b.hi", "b.ls", "b.ge", "b.lt", "b.gt", "b.le", "b.al"};
+static_assert(sizeof(textForCondition) / sizeof(textForCondition[0]) == size_t(ConditionA64::Count), "all conditions have to be covered");
+
+const unsigned kMaxAlign = 32;
+
+AssemblyBuilderA64::AssemblyBuilderA64(bool logText)
+    : logText(logText)
+{
+    data.resize(4096);
+    dataPos = data.size(); // data is filled backwards
+
+    code.resize(1024);
+    codePos = code.data();
+    codeEnd = code.data() + code.size();
+}
+
+AssemblyBuilderA64::~AssemblyBuilderA64()
+{
+    LUAU_ASSERT(finalized);
+}
+
+void AssemblyBuilderA64::mov(RegisterA64 dst, RegisterA64 src)
+{
+    placeSR2("mov", dst, src, 0b01'01010);
+}
+
+void AssemblyBuilderA64::mov(RegisterA64 dst, uint16_t src, int shift)
+{
+    placeI16("mov", dst, src, 0b10'100101, shift);
+}
+
+void AssemblyBuilderA64::movk(RegisterA64 dst, uint16_t src, int shift)
+{
+    placeI16("movk", dst, src, 0b11'100101, shift);
+}
+
+void AssemblyBuilderA64::add(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift)
+{
+    placeSR3("add", dst, src1, src2, 0b00'01011, shift);
+}
+
+void AssemblyBuilderA64::add(RegisterA64 dst, RegisterA64 src1, int src2)
+{
+    placeI12("add", dst, src1, src2, 0b00'10001);
+}
+
+void AssemblyBuilderA64::sub(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift)
+{
+    placeSR3("sub", dst, src1, src2, 0b10'01011, shift);
+}
+
+void AssemblyBuilderA64::sub(RegisterA64 dst, RegisterA64 src1, int src2)
+{
+    placeI12("sub", dst, src1, src2, 0b10'10001);
+}
+
+void AssemblyBuilderA64::neg(RegisterA64 dst, RegisterA64 src)
+{
+    placeSR2("neg", dst, src, 0b10'01011);
+}
+
+void AssemblyBuilderA64::and_(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeSR3("and", dst, src1, src2, 0b00'01010);
+}
+
+void AssemblyBuilderA64::orr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeSR3("orr", dst, src1, src2, 0b01'01010);
+}
+
+void AssemblyBuilderA64::eor(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeSR3("eor", dst, src1, src2, 0b10'01010);
+}
+
+void AssemblyBuilderA64::lsl(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeR3("lsl", dst, src1, src2, 0b11010110, 0b0010'00);
+}
+
+void AssemblyBuilderA64::lsr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeR3("lsr", dst, src1, src2, 0b11010110, 0b0010'01);
+}
+
+void AssemblyBuilderA64::asr(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeR3("asr", dst, src1, src2, 0b11010110, 0b0010'10);
+}
+
+void AssemblyBuilderA64::ror(RegisterA64 dst, RegisterA64 src1, RegisterA64 src2)
+{
+    placeR3("ror", dst, src1, src2, 0b11010110, 0b0010'11);
+}
+
+void AssemblyBuilderA64::clz(RegisterA64 dst, RegisterA64 src)
+{
+    placeR1("clz", dst, src, 0b10'11010110'00000'00010'0);
+}
+
+void AssemblyBuilderA64::rbit(RegisterA64 dst, RegisterA64 src)
+{
+    placeR1("rbit", dst, src, 0b10'11010110'00000'0000'00);
+}
+
+void AssemblyBuilderA64::ldr(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::x || dst.kind == KindA64::w);
+
+    placeA("ldr", dst, src, 0b11100001, 0b10 | uint8_t(dst.kind == KindA64::x));
+}
+
+void AssemblyBuilderA64::ldrb(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::w);
+
+    placeA("ldrb", dst, src, 0b11100001, 0b00);
+}
+
+void AssemblyBuilderA64::ldrh(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::w);
+
+    placeA("ldrh", dst, src, 0b11100001, 0b01);
+}
+
+void AssemblyBuilderA64::ldrsb(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::x || dst.kind == KindA64::w);
+
+    placeA("ldrsb", dst, src, 0b11100010 | uint8_t(dst.kind == KindA64::w), 0b00);
+}
+
+void AssemblyBuilderA64::ldrsh(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::x || dst.kind == KindA64::w);
+
+    placeA("ldrsh", dst, src, 0b11100010 | uint8_t(dst.kind == KindA64::w), 0b01);
+}
+
+void AssemblyBuilderA64::ldrsw(RegisterA64 dst, AddressA64 src)
+{
+    LUAU_ASSERT(dst.kind == KindA64::x);
+
+    placeA("ldrsw", dst, src, 0b11100010, 0b10);
+}
+
+void AssemblyBuilderA64::str(RegisterA64 src, AddressA64 dst)
+{
+    LUAU_ASSERT(src.kind == KindA64::x || src.kind == KindA64::w);
+
+    placeA("str", src, dst, 0b11100000, 0b10 | uint8_t(src.kind == KindA64::x));
+}
+
+void AssemblyBuilderA64::strb(RegisterA64 src, AddressA64 dst)
+{
+    LUAU_ASSERT(src.kind == KindA64::w);
+
+    placeA("strb", src, dst, 0b11100000, 0b00);
+}
+
+void AssemblyBuilderA64::strh(RegisterA64 src, AddressA64 dst)
+{
+    LUAU_ASSERT(src.kind == KindA64::w);
+
+    placeA("strh", src, dst, 0b11100000, 0b01);
+}
+
+void AssemblyBuilderA64::b(ConditionA64 cond, Label& label)
+{
+    placeBC(textForCondition[int(cond)], label, 0b0101010'0, codeForCondition[int(cond)]);
+}
+
+void AssemblyBuilderA64::cbz(RegisterA64 src, Label& label)
+{
+    placeBR("cbz", label, 0b011010'0, src);
+}
+
+void AssemblyBuilderA64::cbnz(RegisterA64 src, Label& label)
+{
+    placeBR("cbnz", label, 0b011010'1, src);
+}
+
+void AssemblyBuilderA64::ret()
+{
+    place0("ret", 0b1101011'0'0'10'11111'0000'0'0'11110'00000);
+}
+
+bool AssemblyBuilderA64::finalize()
+{
+    bool success = true;
+
+    code.resize(codePos - code.data());
+
+    // Resolve jump targets
+    for (Label fixup : pendingLabels)
+    {
+        // If this assertion fires, a label was used in jmp without calling setLabel
+        LUAU_ASSERT(labelLocations[fixup.id - 1] != ~0u);
+
+        int value = int(labelLocations[fixup.id - 1]) - int(fixup.location);
+
+        // imm19 encoding word offset, at bit offset 5
+        // note that 18 bits of word offsets = 20 bits of byte offsets = +-1MB
+        if (value > -(1 << 18) && value < (1 << 18))
+            code[fixup.location] |= (value & ((1 << 19) - 1)) << 5;
+        else
+            success = false; // overflow
+    }
+
+    size_t dataSize = data.size() - dataPos;
+
+    // Shrink data
+    if (dataSize > 0)
+        memmove(&data[0], &data[dataPos], dataSize);
+
+    data.resize(dataSize);
+
+    finalized = true;
+
+    return success;
+}
+
+Label AssemblyBuilderA64::setLabel()
+{
+    Label label{nextLabel++, getCodeSize()};
+    labelLocations.push_back(~0u);
+
+    if (logText)
+        log(label);
+
+    return label;
+}
+
+void AssemblyBuilderA64::setLabel(Label& label)
+{
+    if (label.id == 0)
+    {
+        label.id = nextLabel++;
+        labelLocations.push_back(~0u);
+    }
+
+    label.location = getCodeSize();
+    labelLocations[label.id - 1] = label.location;
+
+    if (logText)
+        log(label);
+}
+
+void AssemblyBuilderA64::logAppend(const char* fmt, ...)
+{
+    char buf[256];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(buf, sizeof(buf), fmt, args);
+    va_end(args);
+    text.append(buf);
+}
+
+uint32_t AssemblyBuilderA64::getCodeSize() const
+{
+    return uint32_t(codePos - code.data());
+}
+
+void AssemblyBuilderA64::place0(const char* name, uint32_t op)
+{
+    if (logText)
+        log(name);
+
+    place(op);
+    commit();
+}
+
+void AssemblyBuilderA64::placeSR3(const char* name, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, uint8_t op, int shift)
+{
+    if (logText)
+        log(name, dst, src1, src2, shift);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(dst.kind == src1.kind && dst.kind == src2.kind);
+    LUAU_ASSERT(shift >= 0 && shift < 64); // right shift requires changing some encoding bits
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (src1.index << 5) | (shift << 10) | (src2.index << 16) | (op << 24) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeSR2(const char* name, RegisterA64 dst, RegisterA64 src, uint8_t op)
+{
+    if (logText)
+        log(name, dst, src);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(dst.kind == src.kind);
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (0x1f << 5) | (src.index << 16) | (op << 24) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeR3(const char* name, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, uint8_t op, uint8_t op2)
+{
+    if (logText)
+        log(name, dst, src1, src2);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(dst.kind == src1.kind && dst.kind == src2.kind);
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (src1.index << 5) | (op2 << 10) | (src2.index << 16) | (op << 21) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeR1(const char* name, RegisterA64 dst, RegisterA64 src, uint32_t op)
+{
+    if (logText)
+        log(name, dst, src);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(dst.kind == src.kind);
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (src.index << 5) | (op << 10) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeI12(const char* name, RegisterA64 dst, RegisterA64 src1, int src2, uint8_t op)
+{
+    if (logText)
+        log(name, dst, src1, src2);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(dst.kind == src1.kind);
+    LUAU_ASSERT(src2 >= 0 && src2 < (1 << 12));
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (src1.index << 5) | (src2 << 10) | (op << 24) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeI16(const char* name, RegisterA64 dst, int src, uint8_t op, int shift)
+{
+    if (logText)
+        log(name, dst, src, shift);
+
+    LUAU_ASSERT(dst.kind == KindA64::w || dst.kind == KindA64::x);
+    LUAU_ASSERT(src >= 0 && src <= 0xffff);
+    LUAU_ASSERT(shift == 0 || shift == 16 || shift == 32 || shift == 48);
+
+    uint32_t sf = (dst.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(dst.index | (src << 5) | ((shift >> 4) << 21) | (op << 23) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::placeA(const char* name, RegisterA64 dst, AddressA64 src, uint8_t op, uint8_t size)
+{
+    if (logText)
+        log(name, dst, src);
+
+    switch (src.kind)
+    {
+    case AddressKindA64::imm:
+        LUAU_ASSERT(src.data % (1 << size) == 0);
+        place(dst.index | (src.base.index << 5) | ((src.data >> size) << 10) | (op << 22) | (1 << 24) | (size << 30));
+        break;
+    case AddressKindA64::reg:
+        place(dst.index | (src.base.index << 5) | (0b10 << 10) | (0b011 << 13) | (src.offset.index << 16) | (1 << 21) | (op << 22) | (size << 30));
+        break;
+    }
+
+    commit();
+}
+
+void AssemblyBuilderA64::placeBC(const char* name, Label& label, uint8_t op, uint8_t cond)
+{
+    placeLabel(label);
+
+    if (logText)
+        log(name, label);
+
+    place(cond | (op << 24));
+    commit();
+}
+
+void AssemblyBuilderA64::placeBR(const char* name, Label& label, uint8_t op, RegisterA64 cond)
+{
+    placeLabel(label);
+
+    if (logText)
+        log(name, cond, label);
+
+    LUAU_ASSERT(cond.kind == KindA64::w || cond.kind == KindA64::x);
+
+    uint32_t sf = (cond.kind == KindA64::x) ? 0x80000000 : 0;
+
+    place(cond.index | (op << 24) | sf);
+    commit();
+}
+
+void AssemblyBuilderA64::place(uint32_t word)
+{
+    LUAU_ASSERT(codePos < codeEnd);
+    *codePos++ = word;
+}
+
+void AssemblyBuilderA64::placeLabel(Label& label)
+{
+    if (label.location == ~0u)
+    {
+        if (label.id == 0)
+        {
+            label.id = nextLabel++;
+            labelLocations.push_back(~0u);
+        }
+
+        pendingLabels.push_back({label.id, getCodeSize()});
+    }
+    else
+    {
+        // note: if label has an assigned location we can in theory avoid patching it later, but
+        // we need to handle potential overflow of 19-bit offsets
+        LUAU_ASSERT(label.id != 0);
+        labelLocations[label.id - 1] = label.location;
+        pendingLabels.push_back({label.id, getCodeSize()});
+    }
+}
+
+void AssemblyBuilderA64::commit()
+{
+    LUAU_ASSERT(codePos <= codeEnd);
+
+    if (codeEnd == codePos)
+        extend();
+}
+
+void AssemblyBuilderA64::extend()
+{
+    uint32_t count = getCodeSize();
+
+    code.resize(code.size() * 2);
+    codePos = code.data() + count;
+    codeEnd = code.data() + code.size();
+}
+
+size_t AssemblyBuilderA64::allocateData(size_t size, size_t align)
+{
+    LUAU_ASSERT(align > 0 && align <= kMaxAlign && (align & (align - 1)) == 0);
+
+    if (dataPos < size)
+    {
+        size_t oldSize = data.size();
+        data.resize(data.size() * 2);
+        memcpy(&data[oldSize], &data[0], oldSize);
+        memset(&data[0], 0, oldSize);
+        dataPos += oldSize;
+    }
+
+    dataPos = (dataPos - size) & ~(align - 1);
+
+    return dataPos;
+}
+
+void AssemblyBuilderA64::log(const char* opcode)
+{
+    logAppend(" %s\n", opcode);
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 dst, RegisterA64 src1, RegisterA64 src2, int shift)
+{
+    logAppend(" %-12s", opcode);
+    log(dst);
+    text.append(",");
+    log(src1);
+    text.append(",");
+    log(src2);
+    if (shift > 0)
+        logAppend(" LSL #%d", shift);
+    text.append("\n");
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 dst, RegisterA64 src1, int src2)
+{
+    logAppend(" %-12s", opcode);
+    log(dst);
+    text.append(",");
+    log(src1);
+    text.append(",");
+    logAppend("#%d", src2);
+    text.append("\n");
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 dst, AddressA64 src)
+{
+    logAppend(" %-12s", opcode);
+    log(dst);
+    text.append(",");
+    log(src);
+    text.append("\n");
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 dst, RegisterA64 src)
+{
+    logAppend(" %-12s", opcode);
+    log(dst);
+    text.append(",");
+    log(src);
+    text.append("\n");
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 dst, int src, int shift)
+{
+    logAppend(" %-12s", opcode);
+    log(dst);
+    text.append(",");
+    logAppend("#%d", src);
+    if (shift > 0)
+        logAppend(" LSL #%d", shift);
+    text.append("\n");
+}
+
+void AssemblyBuilderA64::log(const char* opcode, RegisterA64 src, Label label)
+{
+    logAppend(" %-12s", opcode);
+    log(src);
+    text.append(",");
+    logAppend(".L%d\n", label.id);
+}
+
+void AssemblyBuilderA64::log(const char* opcode, Label label)
+{
+    logAppend(" %-12s.L%d\n", opcode, label.id);
+}
+
+void AssemblyBuilderA64::log(Label label)
+{
+    logAppend(".L%d:\n", label.id);
+}
+
+void AssemblyBuilderA64::log(RegisterA64 reg)
+{
+    switch (reg.kind)
+    {
+    case KindA64::w:
+        if (reg.index == 31)
+            logAppend("wzr");
+        else
+            logAppend("w%d", reg.index);
+        break;
+
+    case KindA64::x:
+        if (reg.index == 31)
+            logAppend("xzr");
+        else
+            logAppend("x%d", reg.index);
+        break;
+
+    case KindA64::none:
+        LUAU_ASSERT(!"Unexpected register kind");
+    }
+}
+
+void AssemblyBuilderA64::log(AddressA64 addr)
+{
+    text.append("[");
+    switch (addr.kind)
+    {
+    case AddressKindA64::imm:
+        log(addr.base);
+        if (addr.data != 0)
+            logAppend(",#%d", addr.data);
+        break;
+    case AddressKindA64::reg:
+        log(addr.base);
+        text.append(",");
+        log(addr.offset);
+        if (addr.data != 0)
+            logAppend(" LSL #%d", addr.data);
+        break;
+    }
+    text.append("]");
+}
+
+} // namespace CodeGen
+} // namespace Luau

CodeGen/src/AssemblyBuilderX64.cpp

@@ -13,13 +13,13 @@ namespace CodeGen
 {
 // TODO: more assertions on operand sizes
 
-const uint8_t codeForCondition[] = {
+static const uint8_t codeForCondition[] = {
     0x0, 0x1, 0x2, 0x3, 0x2, 0x6, 0x7, 0x3, 0x4, 0xc, 0xe, 0xf, 0xd, 0x3, 0x7, 0x6, 0x2, 0x5, 0xd, 0xf, 0xe, 0xc, 0x4, 0x5, 0xa, 0xb};
-static_assert(sizeof(codeForCondition) / sizeof(codeForCondition[0]) == size_t(Condition::Count), "all conditions have to be covered");
+static_assert(sizeof(codeForCondition) / sizeof(codeForCondition[0]) == size_t(ConditionX64::Count), "all conditions have to be covered");
 
-const char* textForCondition[] = {"jo", "jno", "jc", "jnc", "jb", "jbe", "ja", "jae", "je", "jl", "jle", "jg", "jge", "jnb", "jnbe", "jna", "jnae",
+static const char* textForCondition[] = {"jo", "jno", "jc", "jnc", "jb", "jbe", "ja", "jae", "je", "jl", "jle", "jg", "jge", "jnb", "jnbe", "jna",
-    "jne", "jnl", "jnle", "jng", "jnge", "jz", "jnz", "jp", "jnp"};
+    "jnae", "jne", "jnl", "jnle", "jng", "jnge", "jz", "jnz", "jp", "jnp"};
-static_assert(sizeof(textForCondition) / sizeof(textForCondition[0]) == size_t(Condition::Count), "all conditions have to be covered");
+static_assert(sizeof(textForCondition) / sizeof(textForCondition[0]) == size_t(ConditionX64::Count), "all conditions have to be covered");
 
 #define OP_PLUS_REG(op, reg) ((op) + (reg & 0x7))
 #define OP_PLUS_CC(op, cc) ((op) + uint8_t(cc))
@@ -328,7 +328,10 @@ void AssemblyBuilderX64::lea(OperandX64 lhs, OperandX64 rhs)
     if (logText)
         log("lea", lhs, rhs);
 
-    LUAU_ASSERT(rhs.cat == CategoryX64::mem);
+    LUAU_ASSERT(lhs.cat == CategoryX64::reg && rhs.cat == CategoryX64::mem && rhs.memSize == SizeX64::none);
+    LUAU_ASSERT(rhs.base == rip || rhs.base.size == lhs.base.size);
+    LUAU_ASSERT(rhs.index == noreg || rhs.index.size == lhs.base.size);
+    rhs.memSize = lhs.base.size;
     placeBinaryRegAndRegMem(lhs, rhs, 0x8d, 0x8d);
 }
 
@@ -363,7 +366,7 @@ void AssemblyBuilderX64::ret()
     commit();
 }
 
-void AssemblyBuilderX64::jcc(Condition cond, Label& label)
+void AssemblyBuilderX64::jcc(ConditionX64 cond, Label& label)
 {
     placeJcc(textForCondition[size_t(cond)], label, codeForCondition[size_t(cond)]);
 }
@@ -781,7 +784,7 @@ OperandX64 AssemblyBuilderX64::bytes(const void* ptr, size_t size, size_t align)
 {
     size_t pos = allocateData(size, align);
     memcpy(&data[pos], ptr, size);
-    return OperandX64(SizeX64::qword, noreg, 1, rip, int32_t(pos - data.size()));
+    return OperandX64(SizeX64::none, noreg, 1, rip, int32_t(pos - data.size()));
 }
 
 void AssemblyBuilderX64::logAppend(const char* fmt, ...)
@@ -1072,7 +1075,7 @@ void AssemblyBuilderX64::placeVex(OperandX64 dst, OperandX64 src1, OperandX64 sr
     place(AVX_3_3(setW, src1.base, dst.base.size == SizeX64::ymmword, prefix));
 }
 
-uint8_t getScaleEncoding(uint8_t scale)
+static uint8_t getScaleEncoding(uint8_t scale)
 {
     static const uint8_t scales[9] = {0xff, 0, 1, 0xff, 2, 0xff, 0xff, 0xff, 3};
 

CodeGen/src/CodeGen.cpp

@@ -51,10 +51,15 @@ static void assembleHelpers(AssemblyBuilderX64& build, ModuleHelpers& helpers)
         build.logAppend("; exitNoContinueVm\n");
     helpers.exitNoContinueVm = build.setLabel();
     emitExit(build, /* continueInVm */ false);
+
+    if (build.logText)
+        build.logAppend("; continueCallInVm\n");
+    helpers.continueCallInVm = build.setLabel();
+    emitContinueCallInVm(build);
 }
 
-static int emitInst(
+static int emitInst(AssemblyBuilderX64& build, NativeState& data, ModuleHelpers& helpers, Proto* proto, LuauOpcode op, const Instruction* pc, int i,
-    AssemblyBuilderX64& build, NativeState& data, ModuleHelpers& helpers, Proto* proto, LuauOpcode op, const Instruction* pc, int i, Label* labelarr, Label& fallback)
+    Label* labelarr, Label& fallback)
 {
     int skip = 0;
 
@@ -86,6 +91,9 @@ static int emitInst(
     case LOP_SETGLOBAL:
         emitInstSetGlobal(build, pc, i, labelarr, fallback);
         break;
+    case LOP_CALL:
+        emitInstCall(build, helpers, pc, i, labelarr);
+        break;
     case LOP_RETURN:
         emitInstReturn(build, helpers, pc, i, labelarr);
         break;
@@ -123,19 +131,19 @@ static int emitInst(
         emitInstJumpIfEq(build, pc, i, labelarr, /* not_ */ false, fallback);
         break;
     case LOP_JUMPIFLE:
-        emitInstJumpIfCond(build, pc, i, labelarr, Condition::LessEqual, fallback);
+        emitInstJumpIfCond(build, pc, i, labelarr, ConditionX64::LessEqual, fallback);
         break;
     case LOP_JUMPIFLT:
-        emitInstJumpIfCond(build, pc, i, labelarr, Condition::Less, fallback);
+        emitInstJumpIfCond(build, pc, i, labelarr, ConditionX64::Less, fallback);
         break;
     case LOP_JUMPIFNOTEQ:
         emitInstJumpIfEq(build, pc, i, labelarr, /* not_ */ true, fallback);
         break;
     case LOP_JUMPIFNOTLE:
-        emitInstJumpIfCond(build, pc, i, labelarr, Condition::NotLessEqual, fallback);
+        emitInstJumpIfCond(build, pc, i, labelarr, ConditionX64::NotLessEqual, fallback);
         break;
     case LOP_JUMPIFNOTLT:
-        emitInstJumpIfCond(build, pc, i, labelarr, Condition::NotLess, fallback);
+        emitInstJumpIfCond(build, pc, i, labelarr, ConditionX64::NotLess, fallback);
         break;
     case LOP_JUMPX:
         emitInstJumpX(build, pc, i, labelarr);
@@ -291,19 +299,19 @@ static void emitInstFallback(AssemblyBuilderX64& build, NativeState& data, LuauO
         emitInstJumpIfEqFallback(build, pc, i, labelarr, /* not_ */ false);
         break;
     case LOP_JUMPIFLE:
-        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::LessEqual);
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, ConditionX64::LessEqual);
         break;
     case LOP_JUMPIFLT:
-        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::Less);
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, ConditionX64::Less);
         break;
     case LOP_JUMPIFNOTEQ:
         emitInstJumpIfEqFallback(build, pc, i, labelarr, /* not_ */ true);
         break;
     case LOP_JUMPIFNOTLE:
-        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::NotLessEqual);
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, ConditionX64::NotLessEqual);
         break;
     case LOP_JUMPIFNOTLT:
-        emitInstJumpIfCondFallback(build, pc, i, labelarr, Condition::NotLess);
+        emitInstJumpIfCondFallback(build, pc, i, labelarr, ConditionX64::NotLess);
         break;
     case LOP_ADD:
         emitInstBinaryFallback(build, pc, i, TM_ADD);
@@ -687,6 +695,9 @@ void compile(lua_State* L, int idx)
     {
         for (int i = 0; i < result->proto->sizecode; i++)
             result->instTargets[i] += uintptr_t(codeStart + result->location);
+
+        LUAU_ASSERT(result->proto->sizecode);
+        result->entryTarget = result->instTargets[0];
     }
 
     // Link native proto objects to Proto; the memory is now managed by VM and will be freed via onDestroyFunction

CodeGen/src/CodeGenUtils.cpp

@@ -72,5 +72,59 @@ void forgPrepXnextFallback(lua_State* L, TValue* ra, int pc)
     }
 }
 
+Closure* callProlog(lua_State* L, TValue* ra, StkId argtop, int nresults)
+{
+    // slow-path: not a function call
+    if (LUAU_UNLIKELY(!ttisfunction(ra)))
+    {
+        luaV_tryfuncTM(L, ra);
+        argtop++; // __call adds an extra self
+    }
+
+    Closure* ccl = clvalue(ra);
+
+    CallInfo* ci = incr_ci(L);
+    ci->func = ra;
+    ci->base = ra + 1;
+    ci->top = argtop + ccl->stacksize; // note: technically UB since we haven't reallocated the stack yet
+    ci->savedpc = NULL;
+    ci->flags = 0;
+    ci->nresults = nresults;
+
+    L->base = ci->base;
+    L->top = argtop;
+
+    // note: this reallocs stack, but we don't need to VM_PROTECT this
+    // this is because we're going to modify base/savedpc manually anyhow
+    // crucially, we can't use ra/argtop after this line
+    luaD_checkstack(L, ccl->stacksize);
+
+    return ccl;
+}
+
+void callEpilogC(lua_State* L, int nresults, int n)
+{
+    // ci is our callinfo, cip is our parent
+    CallInfo* ci = L->ci;
+    CallInfo* cip = ci - 1;
+
+    // copy return values into parent stack (but only up to nresults!), fill the rest with nil
+    // note: in MULTRET context nresults starts as -1 so i != 0 condition never activates intentionally
+    StkId res = ci->func;
+    StkId vali = L->top - n;
+    StkId valend = L->top;
+
+    int i;
+    for (i = nresults; i != 0 && vali < valend; i--)
+        setobj2s(L, res++, vali++);
+    while (i-- > 0)
+        setnilvalue(res++);
+
+    // pop the stack frame
+    L->ci = cip;
+    L->base = cip->base;
+    L->top = (nresults == LUA_MULTRET) ? res : cip->top;
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/CodeGenUtils.h

@@ -13,5 +13,8 @@ bool forgLoopNonTableFallback(lua_State* L, int insnA, int aux);
 
 void forgPrepXnextFallback(lua_State* L, TValue* ra, int pc);
 
+Closure* callProlog(lua_State* L, TValue* ra, StkId argtop, int nresults);
+void callEpilogC(lua_State* L, int nresults, int n);
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/CodeGenX64.cpp

@@ -87,7 +87,7 @@ bool initEntryFunction(NativeState& data)
     unwind.allocStack(stacksize + localssize);
 
     // Setup frame pointer
-    build.lea(rbp, qword[rsp + stacksize]);
+    build.lea(rbp, addr[rsp + stacksize]);
     unwind.setupFrameReg(rbp, stacksize);
 
     unwind.finish();
@@ -113,7 +113,7 @@ bool initEntryFunction(NativeState& data)
     Label returnOff = build.setLabel();
 
     // Cleanup and exit
-    build.lea(rsp, qword[rbp + localssize]);
+    build.lea(rsp, addr[rbp + localssize]);
     build.pop(r15);
     build.pop(r14);
     build.pop(r13);

CodeGen/src/EmitCommonX64.cpp

@@ -14,7 +14,7 @@ namespace Luau
 namespace CodeGen
 {
 
-void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs, OperandX64 rhs, Condition cond, Label& label)
+void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs, OperandX64 rhs, ConditionX64 cond, Label& label)
 {
     // Refresher on comi/ucomi EFLAGS:
     // CF only: less
@@ -35,53 +35,54 @@ void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs,
     // And because of NaN, integer check interchangeability like 'not less or equal' <-> 'greater' does not hold
     switch (cond)
     {
-    case Condition::NotLessEqual:
+    case ConditionX64::NotLessEqual:
         // (b < a) is the same as !(a <= b). jnae checks CF=1 which means < or NaN
-        build.jcc(Condition::NotAboveEqual, label);
+        build.jcc(ConditionX64::NotAboveEqual, label);
         break;
-    case Condition::LessEqual:
+    case ConditionX64::LessEqual:
         // (b >= a) is the same as (a <= b). jae checks CF=0 which means >= and not NaN
-        build.jcc(Condition::AboveEqual, label);
+        build.jcc(ConditionX64::AboveEqual, label);
         break;
-    case Condition::NotLess:
+    case ConditionX64::NotLess:
         // (b <= a) is the same as !(a < b). jna checks CF=1 or ZF=1 which means <= or NaN
-        build.jcc(Condition::NotAbove, label);
+        build.jcc(ConditionX64::NotAbove, label);
         break;
-    case Condition::Less:
+    case ConditionX64::Less:
         // (b > a) is the same as (a < b). ja checks CF=0 and ZF=0 which means > and not NaN
-        build.jcc(Condition::Above, label);
+        build.jcc(ConditionX64::Above, label);
         break;
-    case Condition::NotEqual:
+    case ConditionX64::NotEqual:
         // ZF=0 or PF=1 means != or NaN
-        build.jcc(Condition::NotZero, label);
+        build.jcc(ConditionX64::NotZero, label);
-        build.jcc(Condition::Parity, label);
+        build.jcc(ConditionX64::Parity, label);
         break;
     default:
         LUAU_ASSERT(!"Unsupported condition");
     }
 }
 
-void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, Condition cond, Label& label, int pcpos)
+void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, ConditionX64 cond, Label& label, int pcpos)
 {
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(ra));
+    build.lea(rArg2, luauRegAddress(ra));
-    build.lea(rArg3, luauRegValue(rb));
+    build.lea(rArg3, luauRegAddress(rb));
 
-    if (cond == Condition::NotLessEqual || cond == Condition::LessEqual)
+    if (cond == ConditionX64::NotLessEqual || cond == ConditionX64::LessEqual)
         build.call(qword[rNativeContext + offsetof(NativeContext, luaV_lessequal)]);
-    else if (cond == Condition::NotLess || cond == Condition::Less)
+    else if (cond == ConditionX64::NotLess || cond == ConditionX64::Less)
         build.call(qword[rNativeContext + offsetof(NativeContext, luaV_lessthan)]);
-    else if (cond == Condition::NotEqual || cond == Condition::Equal)
+    else if (cond == ConditionX64::NotEqual || cond == ConditionX64::Equal)
         build.call(qword[rNativeContext + offsetof(NativeContext, luaV_equalval)]);
     else
         LUAU_ASSERT(!"Unsupported condition");
 
     emitUpdateBase(build);
     build.test(eax, eax);
-    build.jcc(
+    build.jcc(cond == ConditionX64::NotLessEqual || cond == ConditionX64::NotLess || cond == ConditionX64::NotEqual ? ConditionX64::Zero
-        cond == Condition::NotLessEqual || cond == Condition::NotLess || cond == Condition::NotEqual ? Condition::Zero : Condition::NotZero, label);
+                                                                                                                    : ConditionX64::NotZero,
+        label);
 }
 
 RegisterX64 getTableNodeAtCachedSlot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int pcpos)
@@ -120,7 +121,7 @@ void convertNumberToIndexOrJump(AssemblyBuilderX64& build, RegisterX64 tmp, Regi
     build.vucomisd(tmp, numd); // Sets ZF=1 if equal or NaN
     // We don't need non-integer values
     // But to skip the PF=1 check, we proceed with NaN because 0x80000000 index is out of bounds
-    build.jcc(Condition::NotZero, label);
+    build.jcc(ConditionX64::NotZero, label);
 }
 
 void callArithHelper(AssemblyBuilderX64& build, int ra, int rb, OperandX64 c, int pcpos, TMS tm)
@@ -133,8 +134,8 @@ void callArithHelper(AssemblyBuilderX64& build, int ra, int rb, OperandX64 c, in
         build.mov(rArg5, tm);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(ra));
+    build.lea(rArg2, luauRegAddress(ra));
-    build.lea(rArg3, luauRegValue(rb));
+    build.lea(rArg3, luauRegAddress(rb));
     build.lea(rArg4, c);
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_doarith)]);
 
@@ -146,8 +147,8 @@ void callLengthHelper(AssemblyBuilderX64& build, int ra, int rb, int pcpos)
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(ra));
+    build.lea(rArg2, luauRegAddress(ra));
-    build.lea(rArg3, luauRegValue(rb));
+    build.lea(rArg3, luauRegAddress(rb));
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_dolen)]);
 
     emitUpdateBase(build);
@@ -158,9 +159,9 @@ void callPrepareForN(AssemblyBuilderX64& build, int limit, int step, int init, i
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(limit));
+    build.lea(rArg2, luauRegAddress(limit));
-    build.lea(rArg3, luauRegValue(step));
+    build.lea(rArg3, luauRegAddress(step));
-    build.lea(rArg4, luauRegValue(init));
+    build.lea(rArg4, luauRegAddress(init));
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_prepareFORN)]);
 }
 
@@ -169,9 +170,9 @@ void callGetTable(AssemblyBuilderX64& build, int rb, OperandX64 c, int ra, int p
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(rb));
+    build.lea(rArg2, luauRegAddress(rb));
     build.lea(rArg3, c);
-    build.lea(rArg4, luauRegValue(ra));
+    build.lea(rArg4, luauRegAddress(ra));
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_gettable)]);
 
     emitUpdateBase(build);
@@ -182,9 +183,9 @@ void callSetTable(AssemblyBuilderX64& build, int rb, OperandX64 c, int ra, int p
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(rb));
+    build.lea(rArg2, luauRegAddress(rb));
     build.lea(rArg3, c);
-    build.lea(rArg4, luauRegValue(ra));
+    build.lea(rArg4, luauRegAddress(ra));
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_settable)]);
 
     emitUpdateBase(build);
@@ -197,16 +198,16 @@ static void callBarrierImpl(AssemblyBuilderX64& build, RegisterX64 tmp, Register
 
     // iscollectable(ra)
     build.cmp(luauRegTag(ra), LUA_TSTRING);
-    build.jcc(Condition::Less, skip);
+    build.jcc(ConditionX64::Less, skip);
 
     // isblack(obj2gco(o))
     build.test(byte[object + offsetof(GCheader, marked)], bitmask(BLACKBIT));
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     // iswhite(gcvalue(ra))
     build.mov(tmp, luauRegValue(ra));
     build.test(byte[tmp + offsetof(GCheader, marked)], bit2mask(WHITE0BIT, WHITE1BIT));
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     LUAU_ASSERT(object != rArg3);
     build.mov(rArg3, tmp);
@@ -229,12 +230,12 @@ void callBarrierTableFast(AssemblyBuilderX64& build, RegisterX64 table, Label& s
 {
     // isblack(obj2gco(t))
     build.test(byte[table + offsetof(GCheader, marked)], bitmask(BLACKBIT));
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     // Argument setup re-ordered to avoid conflicts with table register
     if (table != rArg2)
         build.mov(rArg2, table);
-    build.lea(rArg3, qword[rArg2 + offsetof(Table, gclist)]);
+    build.lea(rArg3, addr[rArg2 + offsetof(Table, gclist)]);
     build.mov(rArg1, rState);
     build.call(qword[rNativeContext + offsetof(NativeContext, luaC_barrierback)]);
 }
@@ -244,13 +245,13 @@ void callCheckGc(AssemblyBuilderX64& build, int pcpos, bool savepc, Label& skip)
     build.mov(rax, qword[rState + offsetof(lua_State, global)]);
     build.mov(rdx, qword[rax + offsetof(global_State, totalbytes)]);
     build.cmp(rdx, qword[rax + offsetof(global_State, GCthreshold)]);
-    build.jcc(Condition::Below, skip);
+    build.jcc(ConditionX64::Below, skip);
 
     if (savepc)
         emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.mov(rArg2, 1);
+    build.mov(dwordReg(rArg2), 1);
     build.call(qword[rNativeContext + offsetof(NativeContext, luaC_step)]);
 
     emitUpdateBase(build);
@@ -288,7 +289,7 @@ void emitInterrupt(AssemblyBuilderX64& build, int pcpos)
     build.mov(r8, qword[rState + offsetof(lua_State, global)]);
     build.mov(r8, qword[r8 + offsetof(global_State, cb.interrupt)]);
     build.test(r8, r8);
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     emitSetSavedPc(build, pcpos + 1); // uses rax/rdx
 
@@ -301,7 +302,7 @@ void emitInterrupt(AssemblyBuilderX64& build, int pcpos)
     // Check if we need to exit
     build.mov(al, byte[rState + offsetof(lua_State, status)]);
     build.test(al, al);
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     build.mov(rax, qword[rState + offsetof(lua_State, ci)]);
     build.sub(qword[rax + offsetof(CallInfo, savedpc)], sizeof(Instruction));
@@ -329,17 +330,6 @@ void emitFallback(AssemblyBuilderX64& build, NativeState& data, int op, int pcpo
     build.mov(rArg4, rConstants);
     build.call(qword[rNativeContext + offsetof(NativeContext, fallback) + op * sizeof(NativeFallback) + offsetof(NativeFallback, fallback)]);
 
-    // Some instructions may interrupt the execution
-    if (opinfo.flags & kFallbackCheckInterrupt)
-    {
-        Label skip;
-
-        build.test(rax, rax);
-        build.jcc(Condition::NotZero, skip);
-        emitExit(build, /* continueInVm */ false);
-        build.setLabel(skip);
-    }
-
     emitUpdateBase(build);
 
     // Some instructions may jump to a different instruction or a completely different function
@@ -359,50 +349,17 @@ void emitFallback(AssemblyBuilderX64& build, NativeState& data, int op, int pcpo
         build.mov(rcx, qword[rdx + offsetof(NativeProto, instTargets)]);
         build.jmp(qword[rax * 2 + rcx]);
     }
-    else if (opinfo.flags & kFallbackUpdateCi)
+}
-    {
-        // Need to update state of the current function before we jump away
-        build.mov(rcx, qword[rState + offsetof(lua_State, ci)]); // L->ci
-        build.mov(rcx, qword[rcx + offsetof(CallInfo, func)]);   // L->ci->func
-        build.mov(rcx, qword[rcx + offsetof(TValue, value.gc)]); // L->ci->func->value.gc aka cl
-        build.mov(sClosure, rcx);
-        build.mov(rsi, qword[rcx + offsetof(Closure, l.p)]);    // cl->l.p aka proto
-        build.mov(rConstants, qword[rsi + offsetof(Proto, k)]); // proto->k
-        build.mov(rcx, qword[rsi + offsetof(Proto, code)]);     // proto->code
-        build.mov(sCode, rcx);
 
-        // We'll need original instruction pointer later to handle return to interpreter
+void emitContinueCallInVm(AssemblyBuilderX64& build)
-        if (op == LOP_CALL)
+{
-            build.mov(r9, rax);
+    RegisterX64 proto = rcx; // Sync with emitInstCall
 
-        // Get instruction index from instruction pointer
+    build.mov(rdx, qword[proto + offsetof(Proto, code)]);
-        // To get instruction index from instruction pointer, we need to divide byte offset by 4
+    build.mov(rax, qword[rState + offsetof(lua_State, ci)]);
-        // But we will actually need to scale instruction index by 8 back to byte offset later so it cancels out
+    build.mov(qword[rax + offsetof(CallInfo, savedpc)], rdx);
-        build.sub(rax, sCode);
 
-        // We need to check if the new function can be executed natively
+    emitExit(build, /* continueInVm */ true);
-        Label returnToInterpreter;
-
-        build.mov(rdx, qword[rsi + offsetofProtoExecData]);
-        build.test(rdx, rdx);
-        build.jcc(Condition::Zero, returnToInterpreter);
-
-        // Get new instruction location and jump to it
-        build.mov(rcx, qword[rdx + offsetof(NativeProto, instTargets)]);
-        build.jmp(qword[rax * 2 + rcx]);
-
-        build.setLabel(returnToInterpreter);
-
-        // If we are returning to the interpreter to make a call, we need to update the current instruction
-        if (op == LOP_CALL)
-        {
-            build.mov(rax, qword[rState + offsetof(lua_State, ci)]);
-            build.mov(qword[rax + offsetof(CallInfo, savedpc)], r9);
-        }
-
-        // Continue in the interpreter
-        emitExit(build, /* continueInVm */ true);
-    }
 }
 
 } // namespace CodeGen

CodeGen/src/EmitCommonX64.h

@@ -72,6 +72,7 @@ struct ModuleHelpers
 {
     Label exitContinueVm;
     Label exitNoContinueVm;
+    Label continueCallInVm;
 };
 
 inline OperandX64 luauReg(int ri)
@@ -79,6 +80,11 @@ inline OperandX64 luauReg(int ri)
     return xmmword[rBase + ri * sizeof(TValue)];
 }
 
+inline OperandX64 luauRegAddress(int ri)
+{
+    return addr[rBase + ri * sizeof(TValue)];
+}
+
 inline OperandX64 luauRegValue(int ri)
 {
     return qword[rBase + ri * sizeof(TValue) + offsetof(TValue, value)];
@@ -99,6 +105,11 @@ inline OperandX64 luauConstant(int ki)
     return xmmword[rConstants + ki * sizeof(TValue)];
 }
 
+inline OperandX64 luauConstantAddress(int ki)
+{
+    return addr[rConstants + ki * sizeof(TValue)];
+}
+
 inline OperandX64 luauConstantTag(int ki)
 {
     return dword[rConstants + ki * sizeof(TValue) + offsetof(TValue, tt)];
@@ -144,13 +155,13 @@ inline void setNodeValue(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64
 inline void jumpIfTagIs(AssemblyBuilderX64& build, int ri, lua_Type tag, Label& label)
 {
     build.cmp(luauRegTag(ri), tag);
-    build.jcc(Condition::Equal, label);
+    build.jcc(ConditionX64::Equal, label);
 }
 
 inline void jumpIfTagIsNot(AssemblyBuilderX64& build, int ri, lua_Type tag, Label& label)
 {
     build.cmp(luauRegTag(ri), tag);
-    build.jcc(Condition::NotEqual, label);
+    build.jcc(ConditionX64::NotEqual, label);
 }
 
 // Note: fallthrough label should be placed after this condition
@@ -160,7 +171,7 @@ inline void jumpIfFalsy(AssemblyBuilderX64& build, int ri, Label& target, Label&
     jumpIfTagIsNot(build, ri, LUA_TBOOLEAN, fallthrough); // true if not nil or boolean
 
     build.cmp(luauRegValueBoolean(ri), 0);
-    build.jcc(Condition::Equal, target); // true if boolean value is 'true'
+    build.jcc(ConditionX64::Equal, target); // true if boolean value is 'true'
 }
 
 // Note: fallthrough label should be placed after this condition
@@ -170,13 +181,13 @@ inline void jumpIfTruthy(AssemblyBuilderX64& build, int ri, Label& target, Label
     jumpIfTagIsNot(build, ri, LUA_TBOOLEAN, target); // true if not nil or boolean
 
     build.cmp(luauRegValueBoolean(ri), 0);
-    build.jcc(Condition::NotEqual, target); // true if boolean value is 'true'
+    build.jcc(ConditionX64::NotEqual, target); // true if boolean value is 'true'
 }
 
 inline void jumpIfMetatablePresent(AssemblyBuilderX64& build, RegisterX64 table, Label& target)
 {
     build.cmp(qword[table + offsetof(Table, metatable)], 0);
-    build.jcc(Condition::NotEqual, target);
+    build.jcc(ConditionX64::NotEqual, target);
 }
 
 inline void jumpIfUnsafeEnv(AssemblyBuilderX64& build, RegisterX64 tmp, Label& label)
@@ -184,13 +195,13 @@ inline void jumpIfUnsafeEnv(AssemblyBuilderX64& build, RegisterX64 tmp, Label& l
     build.mov(tmp, sClosure);
     build.mov(tmp, qword[tmp + offsetof(Closure, env)]);
     build.test(byte[tmp + offsetof(Table, safeenv)], 1);
-    build.jcc(Condition::Zero, label); // Not a safe environment
+    build.jcc(ConditionX64::Zero, label); // Not a safe environment
 }
 
 inline void jumpIfTableIsReadOnly(AssemblyBuilderX64& build, RegisterX64 table, Label& label)
 {
     build.cmp(byte[table + offsetof(Table, readonly)], 0);
-    build.jcc(Condition::NotEqual, label);
+    build.jcc(ConditionX64::NotEqual, label);
 }
 
 inline void jumpIfNodeKeyTagIsNot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 node, lua_Type tag, Label& label)
@@ -200,13 +211,13 @@ inline void jumpIfNodeKeyTagIsNot(AssemblyBuilderX64& build, RegisterX64 tmp, Re
     build.mov(tmp, luauNodeKeyTag(node));
     build.and_(tmp, kLuaNodeTagMask);
     build.cmp(tmp, tag);
-    build.jcc(Condition::NotEqual, label);
+    build.jcc(ConditionX64::NotEqual, label);
 }
 
 inline void jumpIfNodeValueTagIs(AssemblyBuilderX64& build, RegisterX64 node, lua_Type tag, Label& label)
 {
     build.cmp(dword[node + offsetof(LuaNode, val) + offsetof(TValue, tt)], tag);
-    build.jcc(Condition::Equal, label);
+    build.jcc(ConditionX64::Equal, label);
 }
 
 inline void jumpIfNodeKeyNotInExpectedSlot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 node, OperandX64 expectedKey, Label& label)
@@ -215,13 +226,13 @@ inline void jumpIfNodeKeyNotInExpectedSlot(AssemblyBuilderX64& build, RegisterX6
 
     build.mov(tmp, expectedKey);
     build.cmp(tmp, luauNodeKeyValue(node));
-    build.jcc(Condition::NotEqual, label);
+    build.jcc(ConditionX64::NotEqual, label);
 
     jumpIfNodeValueTagIs(build, node, LUA_TNIL, label);
 }
 
-void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs, OperandX64 rhs, Condition cond, Label& label);
+void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs, OperandX64 rhs, ConditionX64 cond, Label& label);
-void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, Condition cond, Label& label, int pcpos);
+void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, ConditionX64 cond, Label& label, int pcpos);
 
 RegisterX64 getTableNodeAtCachedSlot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int pcpos);
 void convertNumberToIndexOrJump(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 numd, RegisterX64 numi, int ri, Label& label);
@@ -242,5 +253,8 @@ void emitSetSavedPc(AssemblyBuilderX64& build, int pcpos); // Note: only uses ra
 void emitInterrupt(AssemblyBuilderX64& build, int pcpos);
 void emitFallback(AssemblyBuilderX64& build, NativeState& data, int op, int pcpos);
 
+void emitContinueCallInVm(AssemblyBuilderX64& build);
+void emitExitFromLastReturn(AssemblyBuilderX64& build);
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/EmitInstructionX64.cpp

@@ -11,9 +11,6 @@
 #include "lobject.h"
 #include "ltm.h"
 
-// TODO: all uses of luauRegValue and luauConstantValue need to be audited; some need to be changed to luauReg/ConstantAddress (doesn't exist yet)
-// (the problem with existing use is that it includes additional offsetof(TValue, value) which happens to be 0 but isn't guaranteed to be)
-
 namespace Luau
 {
 namespace CodeGen
@@ -72,6 +69,159 @@ void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc)
     build.vmovups(luauReg(ra), xmm0);
 }
 
+void emitInstCall(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int nparams = LUAU_INSN_B(*pc) - 1;
+    int nresults = LUAU_INSN_C(*pc) - 1;
+
+    emitInterrupt(build, pcpos);
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rArg1, rState);
+    build.lea(rArg2, luauRegAddress(ra));
+
+    if (nparams == LUA_MULTRET)
+        build.mov(rArg3, qword[rState + offsetof(lua_State, top)]);
+    else
+        build.lea(rArg3, luauRegAddress(ra + 1 + nparams));
+
+    build.mov(dwordReg(rArg4), nresults);
+    build.call(qword[rNativeContext + offsetof(NativeContext, callProlog)]);
+    RegisterX64 ccl = rax; // Returned from callProlog
+
+    emitUpdateBase(build);
+
+    Label cFuncCall;
+
+    build.test(byte[ccl + offsetof(Closure, isC)], 1);
+    build.jcc(ConditionX64::NotZero, cFuncCall);
+
+    {
+        RegisterX64 proto = rcx; // Sync with emitContinueCallInVm
+        RegisterX64 ci = rdx;
+        RegisterX64 argi = rsi;
+        RegisterX64 argend = rdi;
+
+        build.mov(proto, qword[ccl + offsetof(Closure, l.p)]);
+
+        // Switch current Closure
+        build.mov(sClosure, ccl); // Last use of 'ccl'
+
+        build.mov(ci, qword[rState + offsetof(lua_State, ci)]);
+
+        Label fillnil, exitfillnil;
+
+        // argi = L->top
+        build.mov(argi, qword[rState + offsetof(lua_State, top)]);
+
+        // argend = L->base + p->numparams
+        build.movzx(eax, byte[proto + offsetof(Proto, numparams)]);
+        build.shl(eax, kTValueSizeLog2);
+        build.lea(argend, addr[rBase + rax]);
+
+        // while (argi < argend) setnilvalue(argi++);
+        build.setLabel(fillnil);
+        build.cmp(argi, argend);
+        build.jcc(ConditionX64::NotBelow, exitfillnil);
+
+        build.mov(dword[argi + offsetof(TValue, tt)], LUA_TNIL);
+        build.add(argi, sizeof(TValue));
+        build.jmp(fillnil); // This loop rarely runs so it's not worth repeating cmp/jcc
+
+        build.setLabel(exitfillnil);
+
+        // Set L->top to ci->top as most function expect (no vararg)
+        build.mov(rax, qword[ci + offsetof(CallInfo, top)]);
+        build.mov(qword[rState + offsetof(lua_State, top)], rax);
+
+        build.mov(rax, qword[proto + offsetofProtoExecData]); // We'll need this value later
+
+        // But if it is vararg, update it to 'argi'
+        Label skipVararg;
+
+        build.test(byte[proto + offsetof(Proto, is_vararg)], 1);
+        build.jcc(ConditionX64::Zero, skipVararg);
+
+        build.mov(qword[rState + offsetof(lua_State, top)], argi);
+        build.setLabel(skipVararg);
+
+        // Check native function data
+        build.test(rax, rax);
+        build.jcc(ConditionX64::Zero, helpers.continueCallInVm);
+
+        // Switch current constants
+        build.mov(rConstants, qword[proto + offsetof(Proto, k)]);
+
+        // Switch current code
+        build.mov(rdx, qword[proto + offsetof(Proto, code)]);
+        build.mov(sCode, rdx);
+
+        build.jmp(qword[rax + offsetof(NativeProto, entryTarget)]);
+    }
+
+    build.setLabel(cFuncCall);
+
+    {
+        // results = ccl->c.f(L);
+        build.mov(rArg1, rState);
+        build.call(qword[ccl + offsetof(Closure, c.f)]); // Last use of 'ccl'
+        RegisterX64 results = eax;
+
+        build.test(results, results);                            // test here will set SF=1 for a negative number and it always sets OF to 0
+        build.jcc(ConditionX64::Less, helpers.exitNoContinueVm); // jl jumps if SF != OF
+
+        // We have special handling for small number of expected results below
+        if (nresults != 0 && nresults != 1)
+        {
+            build.mov(rArg1, rState);
+            build.mov(dwordReg(rArg2), nresults);
+            build.mov(dwordReg(rArg3), results);
+            build.call(qword[rNativeContext + offsetof(NativeContext, callEpilogC)]);
+
+            emitUpdateBase(build);
+            return;
+        }
+
+        RegisterX64 ci = rdx;
+        RegisterX64 cip = rcx;
+        RegisterX64 vali = rsi;
+
+        build.mov(ci, qword[rState + offsetof(lua_State, ci)]);
+        build.lea(cip, addr[ci - sizeof(CallInfo)]);
+
+        // L->base = cip->base
+        build.mov(rBase, qword[cip + offsetof(CallInfo, base)]);
+        build.mov(qword[rState + offsetof(lua_State, base)], rBase);
+
+        if (nresults == 1)
+        {
+            // Opportunistically copy the result we expected from (L->top - results)
+            build.mov(vali, qword[rState + offsetof(lua_State, top)]);
+            build.shl(results, kTValueSizeLog2);
+            build.sub(vali, qwordReg(results));
+            build.vmovups(xmm0, xmmword[vali]);
+            build.vmovups(luauReg(ra), xmm0);
+
+            Label skipnil;
+
+            // If there was no result, override the value with 'nil'
+            build.test(results, results);
+            build.jcc(ConditionX64::NotZero, skipnil);
+            build.mov(luauRegTag(ra), LUA_TNIL);
+            build.setLabel(skipnil);
+        }
+
+        // L->ci = cip
+        build.mov(qword[rState + offsetof(lua_State, ci)], cip);
+
+        // L->top = cip->top
+        build.mov(rax, qword[cip + offsetof(CallInfo, top)]);
+        build.mov(qword[rState + offsetof(lua_State, top)], rax);
+    }
+}
+
 void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr)
 {
     emitInterrupt(build, pcpos);
@@ -85,7 +235,7 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
     RegisterX64 nresults = esi;
 
     build.mov(ci, qword[rState + offsetof(lua_State, ci)]);
-    build.lea(cip, qword[ci - sizeof(CallInfo)]);
+    build.lea(cip, addr[ci - sizeof(CallInfo)]);
 
     // res = ci->func; note: we assume CALL always puts func+args and expects results to start at func
     build.mov(res, qword[ci + offsetof(CallInfo, func)]);
@@ -100,8 +250,8 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
         if (b == 0)
         {
             // Our instruction doesn't have any results, so just fill results expected in parent with 'nil'
-            build.test(nresults, nresults);                  // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.test(nresults, nresults);                     // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
-            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+            build.jcc(ConditionX64::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
 
             build.mov(counter, nresults);
 
@@ -109,29 +259,29 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
             build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
             build.add(res, sizeof(TValue));
             build.dec(counter);
-            build.jcc(Condition::NotZero, repeatNilLoop);
+            build.jcc(ConditionX64::NotZero, repeatNilLoop);
         }
         else if (b == 1)
         {
             // Try setting our 1 result
             build.test(nresults, nresults);
-            build.jcc(Condition::Zero, skipResultCopy);
+            build.jcc(ConditionX64::Zero, skipResultCopy);
 
-            build.lea(counter, dword[nresults - 1]);
+            build.lea(counter, addr[nresults - 1]);
 
             build.vmovups(xmm0, luauReg(ra));
             build.vmovups(xmmword[res], xmm0);
             build.add(res, sizeof(TValue));
 
             // Fill the rest of the expected results with 'nil'
-            build.test(counter, counter);                    // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.test(counter, counter);                       // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
-            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+            build.jcc(ConditionX64::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
 
             Label repeatNilLoop = build.setLabel();
             build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
             build.add(res, sizeof(TValue));
             build.dec(counter);
-            build.jcc(Condition::NotZero, repeatNilLoop);
+            build.jcc(ConditionX64::NotZero, repeatNilLoop);
         }
         else
         {
@@ -140,16 +290,16 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
 
             // Copy return values into parent stack (but only up to nresults!)
             build.test(nresults, nresults);
-            build.jcc(Condition::Zero, skipResultCopy);
+            build.jcc(ConditionX64::Zero, skipResultCopy);
 
             // vali = ra
-            build.lea(vali, luauRegValue(ra));
+            build.lea(vali, luauRegAddress(ra));
 
             // Copy as much as possible for MULTRET calls, and only as much as needed otherwise
             if (b == LUA_MULTRET)
                 build.mov(valend, qword[rState + offsetof(lua_State, top)]); // valend = L->top
             else
-                build.lea(valend, luauRegValue(ra + b)); // valend = ra + b
+                build.lea(valend, luauRegAddress(ra + b)); // valend = ra + b
 
             build.mov(counter, nresults);
 
@@ -157,26 +307,26 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
 
             build.setLabel(repeatValueLoop);
             build.cmp(vali, valend);
-            build.jcc(Condition::NotBelow, exitValueLoop);
+            build.jcc(ConditionX64::NotBelow, exitValueLoop);
 
             build.vmovups(xmm0, xmmword[vali]);
             build.vmovups(xmmword[res], xmm0);
             build.add(vali, sizeof(TValue));
             build.add(res, sizeof(TValue));
             build.dec(counter);
-            build.jcc(Condition::NotZero, repeatValueLoop);
+            build.jcc(ConditionX64::NotZero, repeatValueLoop);
 
             build.setLabel(exitValueLoop);
 
             // Fill the rest of the expected results with 'nil'
-            build.test(counter, counter);                    // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
+            build.test(counter, counter);                       // test here will set SF=1 for a negative number, ZF=1 for zero and OF=0
-            build.jcc(Condition::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
+            build.jcc(ConditionX64::LessEqual, skipResultCopy); // jle jumps if SF != OF or ZF == 1
 
             Label repeatNilLoop = build.setLabel();
             build.mov(dword[res + offsetof(TValue, tt)], LUA_TNIL);
             build.add(res, sizeof(TValue));
             build.dec(counter);
-            build.jcc(Condition::NotZero, repeatNilLoop);
+            build.jcc(ConditionX64::NotZero, repeatNilLoop);
         }
 
         build.setLabel(skipResultCopy);
@@ -191,11 +341,11 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
 
     // Unlikely, but this might be the last return from VM
     build.test(byte[ci + offsetof(CallInfo, flags)], LUA_CALLINFO_RETURN);
-    build.jcc(Condition::NotZero, helpers.exitNoContinueVm);
+    build.jcc(ConditionX64::NotZero, helpers.exitNoContinueVm);
 
     Label skipFixedRetTop;
-    build.test(nresults, nresults);              // test here will set SF=1 for a negative number and it always sets OF to 0
+    build.test(nresults, nresults);                 // test here will set SF=1 for a negative number and it always sets OF to 0
-    build.jcc(Condition::Less, skipFixedRetTop); // jl jumps if SF != OF
+    build.jcc(ConditionX64::Less, skipFixedRetTop); // jl jumps if SF != OF
     build.mov(rax, qword[cip + offsetof(CallInfo, top)]);
     build.mov(qword[rState + offsetof(lua_State, top)], rax); // L->top = cip->top
     build.setLabel(skipFixedRetTop);
@@ -214,7 +364,7 @@ void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Ins
 
     build.mov(execdata, qword[proto + offsetofProtoExecData]);
     build.test(execdata, execdata);
-    build.jcc(Condition::Zero, helpers.exitContinueVm); // Continue in interpreter if function has no native data
+    build.jcc(ConditionX64::Zero, helpers.exitContinueVm); // Continue in interpreter if function has no native data
 
     // Change constants
     build.mov(rConstants, qword[proto + offsetof(Proto, k)]);
@@ -269,13 +419,13 @@ void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
     build.mov(eax, luauRegTag(ra));
     build.cmp(eax, luauRegTag(rb));
-    build.jcc(Condition::NotEqual, not_ ? target : exit);
+    build.jcc(ConditionX64::NotEqual, not_ ? target : exit);
 
     // fast-path: number
     build.cmp(eax, LUA_TNUMBER);
-    build.jcc(Condition::NotEqual, fallback);
+    build.jcc(ConditionX64::NotEqual, fallback);
 
-    jumpOnNumberCmp(build, xmm0, luauRegValue(ra), luauRegValue(rb), Condition::NotEqual, not_ ? target : exit);
+    jumpOnNumberCmp(build, xmm0, luauRegValue(ra), luauRegValue(rb), ConditionX64::NotEqual, not_ ? target : exit);
 
     if (!not_)
         build.jmp(target);
@@ -285,10 +435,10 @@ void emitInstJumpIfEqFallback(AssemblyBuilderX64& build, const Instruction* pc,
 {
     Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
-    jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], not_ ? Condition::NotEqual : Condition::Equal, target, pcpos);
+    jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], not_ ? ConditionX64::NotEqual : ConditionX64::Equal, target, pcpos);
 }
 
-void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond, Label& fallback)
+void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, ConditionX64 cond, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = pc[1];
@@ -302,7 +452,7 @@ void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pc
     jumpOnNumberCmp(build, xmm0, luauRegValue(ra), luauRegValue(rb), cond, target);
 }
 
-void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond)
+void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, ConditionX64 cond)
 {
     Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
@@ -324,7 +474,7 @@ void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pc
     Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     build.cmp(luauRegTag(ra), LUA_TNIL);
-    build.jcc(not_ ? Condition::NotEqual : Condition::Equal, target);
+    build.jcc(not_ ? ConditionX64::NotEqual : ConditionX64::Equal, target);
 }
 
 void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
@@ -339,7 +489,7 @@ void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     jumpIfTagIsNot(build, ra, LUA_TBOOLEAN, not_ ? target : exit);
 
     build.test(luauRegValueBoolean(ra), 1);
-    build.jcc((aux & 0x1) ^ not_ ? Condition::NotZero : Condition::Zero, target);
+    build.jcc((aux & 0x1) ^ not_ ? ConditionX64::NotZero : ConditionX64::Zero, target);
 }
 
 void emitInstJumpxEqN(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
@@ -356,15 +506,15 @@ void emitInstJumpxEqN(AssemblyBuilderX64& build, const Instruction* pc, const TV
 
     if (not_)
     {
-        jumpOnNumberCmp(build, xmm0, luauRegValue(ra), build.f64(kv.value.n), Condition::NotEqual, target);
+        jumpOnNumberCmp(build, xmm0, luauRegValue(ra), build.f64(kv.value.n), ConditionX64::NotEqual, target);
     }
     else
     {
         // Compact equality check requires two labels, so it's not supported in generic 'jumpOnNumberCmp'
         build.vmovsd(xmm0, luauRegValue(ra));
         build.vucomisd(xmm0, build.f64(kv.value.n));
-        build.jcc(Condition::Parity, exit); // We first have to check PF=1 for NaN operands, because it also sets ZF=1
+        build.jcc(ConditionX64::Parity, exit); // We first have to check PF=1 for NaN operands, because it also sets ZF=1
-        build.jcc(Condition::Zero, target); // Now that NaN is out of the way, we can check ZF=1 for equality
+        build.jcc(ConditionX64::Zero, target); // Now that NaN is out of the way, we can check ZF=1 for equality
     }
 }
 
@@ -381,7 +531,7 @@ void emitInstJumpxEqS(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
     build.mov(rax, luauRegValue(ra));
     build.cmp(rax, luauConstantValue(aux & 0xffffff));
-    build.jcc(not_ ? Condition::NotEqual : Condition::Equal, target);
+    build.jcc(not_ ? ConditionX64::NotEqual : ConditionX64::Equal, target);
 }
 
 static void emitInstBinaryNumeric(AssemblyBuilderX64& build, int ra, int rb, int rc, OperandX64 opc, int pcpos, TMS tm, Label& fallback)
@@ -437,7 +587,7 @@ void emitInstBinary(AssemblyBuilderX64& build, const Instruction* pc, int pcpos,
 
 void emitInstBinaryFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm)
 {
-    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, tm);
+    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauRegAddress(LUAU_INSN_C(*pc)), pcpos, tm);
 }
 
 void emitInstBinaryK(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm, Label& fallback)
@@ -447,7 +597,7 @@ void emitInstBinaryK(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
 
 void emitInstBinaryKFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm)
 {
-    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauConstantValue(LUAU_INSN_C(*pc)), pcpos, tm);
+    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauConstantAddress(LUAU_INSN_C(*pc)), pcpos, tm);
 }
 
 void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label& fallback)
@@ -525,7 +675,7 @@ void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos,
 
 void emitInstMinusFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
 {
-    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauRegValue(LUAU_INSN_B(*pc)), pcpos, TM_UNM);
+    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauRegAddress(LUAU_INSN_B(*pc)), pcpos, TM_UNM);
 }
 
 void emitInstLength(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
@@ -563,8 +713,8 @@ void emitInstNewTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.mov(rArg2, aux);
+    build.mov(dwordReg(rArg2), aux);
-    build.mov(rArg3, b == 0 ? 0 : 1 << (b - 1));
+    build.mov(dwordReg(rArg3), 1 << (b - 1));
     build.call(qword[rNativeContext + offsetof(NativeContext, luaH_new)]);
     build.mov(luauRegValue(ra), rax);
     build.mov(luauRegTag(ra), LUA_TTABLE);
@@ -610,7 +760,7 @@ void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
 
         // c = L->top - rb
         build.mov(cscaled, qword[rState + offsetof(lua_State, top)]);
-        build.lea(tmp, luauRegValue(rb));
+        build.lea(tmp, luauRegAddress(rb));
         build.sub(cscaled, tmp); // Using byte difference
 
         // L->top = L->ci->top
@@ -633,7 +783,7 @@ void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
 
     // Resize if h->sizearray < last
     build.cmp(dword[table + offsetof(Table, sizearray)], last);
-    build.jcc(Condition::NotBelow, skipResize);
+    build.jcc(ConditionX64::NotBelow, skipResize);
 
     // Argument setup reordered to avoid conflicts
     LUAU_ASSERT(rArg3 != table);
@@ -676,7 +826,7 @@ void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
         if (c == LUA_MULTRET)
         {
             build.cmp(offset, limit);
-            build.jcc(Condition::NotBelow, endLoop);
+            build.jcc(ConditionX64::NotBelow, endLoop);
         }
 
         build.setLabel(repeatLoop);
@@ -687,7 +837,7 @@ void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos
 
         build.add(offset, sizeof(TValue));
         build.cmp(offset, limit);
-        build.jcc(Condition::Below, repeatLoop);
+        build.jcc(ConditionX64::Below, repeatLoop);
 
         build.setLabel(endLoop);
     }
@@ -707,7 +857,7 @@ void emitInstGetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     Label skip;
     // TODO: jumpIfTagIsNot can be generalized to take OperandX64 and then we can use it here; let's wait until we see this more though
     build.cmp(dword[rax + offsetof(TValue, tt)], LUA_TUPVAL);
-    build.jcc(Condition::NotEqual, skip);
+    build.jcc(ConditionX64::NotEqual, skip);
 
     // UpVal.v points to the value (either on stack, or on heap inside each UpVal, but we can deref it unconditionally)
     build.mov(rax, qword[rax + offsetof(TValue, value.gc)]);
@@ -746,12 +896,12 @@ void emitInstCloseUpvals(AssemblyBuilderX64& build, const Instruction* pc, int p
     // L->openupval != 0
     build.mov(rax, qword[rState + offsetof(lua_State, openupval)]);
     build.test(rax, rax);
-    build.jcc(Condition::Zero, skip);
+    build.jcc(ConditionX64::Zero, skip);
 
     // ra <= L->openuval->v
-    build.lea(rcx, qword[rBase + ra * sizeof(TValue)]);
+    build.lea(rcx, addr[rBase + ra * sizeof(TValue)]);
     build.cmp(rcx, qword[rax + offsetof(UpVal, v)]);
-    build.jcc(Condition::Above, skip);
+    build.jcc(ConditionX64::Above, skip);
 
     build.mov(rArg2, rcx);
     build.mov(rArg1, rState);
@@ -771,7 +921,7 @@ static int emitInstFastCallN(AssemblyBuilderX64& build, const Instruction* pc, b
     int nparams = customParams ? customParamCount : LUAU_INSN_B(call) - 1;
     int nresults = LUAU_INSN_C(call) - 1;
     int arg = customParams ? LUAU_INSN_B(*pc) : ra + 1;
-    OperandX64 args = customParams ? customArgs : luauRegValue(ra + 2);
+    OperandX64 args = customParams ? customArgs : luauRegAddress(ra + 2);
 
     Label& exit = labelarr[pcpos + instLen];
 
@@ -784,7 +934,7 @@ static int emitInstFastCallN(AssemblyBuilderX64& build, const Instruction* pc, b
         if (nresults == LUA_MULTRET)
         {
             // L->top = ra + n;
-            build.lea(rax, qword[rBase + (ra + br.actualResultCount) * sizeof(TValue)]);
+            build.lea(rax, addr[rBase + (ra + br.actualResultCount) * sizeof(TValue)]);
             build.mov(qword[rState + offsetof(lua_State, top)], rax);
         }
         else if (nparams == LUA_MULTRET)
@@ -822,7 +972,7 @@ static int emitInstFastCallN(AssemblyBuilderX64& build, const Instruction* pc, b
         // TODO: for SystemV ABI we can compute the result directly into rArg6
         // L->top - (ra + 1)
         build.mov(rcx, qword[rState + offsetof(lua_State, top)]);
-        build.lea(rdx, qword[rBase + (ra + 1) * sizeof(TValue)]);
+        build.lea(rdx, addr[rBase + (ra + 1) * sizeof(TValue)]);
         build.sub(rcx, rdx);
         build.shr(rcx, kTValueSizeLog2);
 
@@ -840,20 +990,20 @@ static int emitInstFastCallN(AssemblyBuilderX64& build, const Instruction* pc, b
     }
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(ra));
+    build.lea(rArg2, luauRegAddress(ra));
-    build.lea(rArg3, luauRegValue(arg));
+    build.lea(rArg3, luauRegAddress(arg));
-    build.mov(rArg4, nresults);
+    build.mov(dwordReg(rArg4), nresults);
 
     build.call(rax);
 
-    build.test(eax, eax);             // test here will set SF=1 for a negative number and it always sets OF to 0
+    build.test(eax, eax);                // test here will set SF=1 for a negative number and it always sets OF to 0
-    build.jcc(Condition::Less, exit); // jl jumps if SF != OF
+    build.jcc(ConditionX64::Less, exit); // jl jumps if SF != OF
 
     if (nresults == LUA_MULTRET)
     {
         // L->top = ra + n;
         build.shl(rax, kTValueSizeLog2);
-        build.lea(rax, qword[rBase + rax + ra * sizeof(TValue)]);
+        build.lea(rax, addr[rBase + rax + ra * sizeof(TValue)]);
         build.mov(qword[rState + offsetof(lua_State, top)], rax);
     }
     else if (nparams == LUA_MULTRET)
@@ -875,13 +1025,13 @@ int emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 int emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     return emitInstFastCallN(
-        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauRegValue(pc[1]), pcpos, /* instLen */ 2, labelarr);
+        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauRegAddress(pc[1]), pcpos, /* instLen */ 2, labelarr);
 }
 
 int emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     return emitInstFastCallN(
-        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauConstantValue(pc[1]), pcpos, /* instLen */ 2, labelarr);
+        build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauConstantAddress(pc[1]), pcpos, /* instLen */ 2, labelarr);
 }
 
 int emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
@@ -916,16 +1066,16 @@ void emitInstForNPrep(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     Label reverse;
 
     // step <= 0
-    jumpOnNumberCmp(build, noreg, step, zero, Condition::LessEqual, reverse);
+    jumpOnNumberCmp(build, noreg, step, zero, ConditionX64::LessEqual, reverse);
 
     // TODO: target branches can probably be arranged better, but we need tests for NaN behavior preservation
     // false: idx <= limit
-    jumpOnNumberCmp(build, noreg, idx, limit, Condition::LessEqual, exit);
+    jumpOnNumberCmp(build, noreg, idx, limit, ConditionX64::LessEqual, exit);
     build.jmp(loopExit);
 
     // true: limit <= idx
     build.setLabel(reverse);
-    jumpOnNumberCmp(build, noreg, limit, idx, Condition::LessEqual, exit);
+    jumpOnNumberCmp(build, noreg, limit, idx, ConditionX64::LessEqual, exit);
     build.jmp(loopExit);
 
     // TOOD: place at the end of the function
@@ -958,15 +1108,15 @@ void emitInstForNLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     Label reverse, exit;
 
     // step <= 0
-    jumpOnNumberCmp(build, noreg, step, zero, Condition::LessEqual, reverse);
+    jumpOnNumberCmp(build, noreg, step, zero, ConditionX64::LessEqual, reverse);
 
     // false: idx <= limit
-    jumpOnNumberCmp(build, noreg, idx, limit, Condition::LessEqual, loopRepeat);
+    jumpOnNumberCmp(build, noreg, idx, limit, ConditionX64::LessEqual, loopRepeat);
     build.jmp(exit);
 
     // true: limit <= idx
     build.setLabel(reverse);
-    jumpOnNumberCmp(build, noreg, limit, idx, Condition::LessEqual, loopRepeat);
+    jumpOnNumberCmp(build, noreg, limit, idx, ConditionX64::LessEqual, loopRepeat);
 
     build.setLabel(exit);
 }
@@ -1010,13 +1160,13 @@ void emitinstForGLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     // while (unsigned(index) < unsigned(sizearray))
     Label arrayLoop = build.setLabel();
     build.cmp(dwordReg(index), dword[table + offsetof(Table, sizearray)]);
-    build.jcc(Condition::NotBelow, isIpairsIter ? exit : skipArray);
+    build.jcc(ConditionX64::NotBelow, isIpairsIter ? exit : skipArray);
 
     // If element is nil, we increment the index; if it's not, we still need 'index + 1' inside
     build.inc(index);
 
     build.cmp(dword[elemPtr + offsetof(TValue, tt)], LUA_TNIL);
-    build.jcc(Condition::Equal, isIpairsIter ? exit : skipArrayNil);
+    build.jcc(ConditionX64::Equal, isIpairsIter ? exit : skipArrayNil);
 
     // setpvalue(ra + 2, reinterpret_cast<void*>(uintptr_t(index + 1)));
     build.mov(luauRegValue(ra + 2), index);
@@ -1045,10 +1195,10 @@ void emitinstForGLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
         // Call helper to assign next node value or to signal loop exit
         build.mov(rArg1, rState);
         // rArg2 and rArg3 are already set
-        build.lea(rArg4, luauRegValue(ra));
+        build.lea(rArg4, luauRegAddress(ra));
         build.call(qword[rNativeContext + offsetof(NativeContext, forgLoopNodeIter)]);
         build.test(al, al);
-        build.jcc(Condition::NotZero, loopRepeat);
+        build.jcc(ConditionX64::NotZero, loopRepeat);
     }
 }
 
@@ -1062,12 +1212,12 @@ void emitinstForGLoopFallback(AssemblyBuilderX64& build, const Instruction* pc,
     emitSetSavedPc(build, pcpos + 1);
 
     build.mov(rArg1, rState);
-    build.mov(rArg2, ra);
+    build.mov(dwordReg(rArg2), ra);
-    build.mov(rArg3, aux);
+    build.mov(dwordReg(rArg3), aux);
     build.call(qword[rNativeContext + offsetof(NativeContext, forgLoopNonTableFallback)]);
     emitUpdateBase(build);
     build.test(al, al);
-    build.jcc(Condition::NotZero, loopRepeat);
+    build.jcc(ConditionX64::NotZero, loopRepeat);
 }
 
 void emitInstForGPrepNext(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
@@ -1103,7 +1253,7 @@ void emitInstForGPrepInext(AssemblyBuilderX64& build, const Instruction* pc, int
 
     build.vxorpd(xmm0, xmm0, xmm0);
     build.vmovsd(xmm1, luauRegValue(ra + 2));
-    jumpOnNumberCmp(build, noreg, xmm0, xmm1, Condition::NotEqual, fallback);
+    jumpOnNumberCmp(build, noreg, xmm0, xmm1, ConditionX64::NotEqual, fallback);
 
     build.mov(luauRegTag(ra), LUA_TNIL);
 
@@ -1121,8 +1271,8 @@ void emitInstForGPrepXnextFallback(AssemblyBuilderX64& build, const Instruction*
     Label& target = labelarr[pcpos + 1 + LUAU_INSN_D(*pc)];
 
     build.mov(rArg1, rState);
-    build.lea(rArg2, luauRegValue(ra));
+    build.lea(rArg2, luauRegAddress(ra));
-    build.mov(rArg3, pcpos + 1);
+    build.mov(dwordReg(rArg3), pcpos + 1);
     build.call(qword[rNativeContext + offsetof(NativeContext, forgPrepXnextFallback)]);
     build.jmp(target);
 }
@@ -1216,7 +1366,7 @@ void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcp
 
     // unsigned(c) < unsigned(h->sizearray)
     build.cmp(dword[table + offsetof(Table, sizearray)], c);
-    build.jcc(Condition::BelowEqual, fallback);
+    build.jcc(ConditionX64::BelowEqual, fallback);
 
     jumpIfMetatablePresent(build, table, fallback);
 
@@ -1244,7 +1394,7 @@ void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcp
 
     // unsigned(c) < unsigned(h->sizearray)
     build.cmp(dword[table + offsetof(Table, sizearray)], c);
-    build.jcc(Condition::BelowEqual, fallback);
+    build.jcc(ConditionX64::BelowEqual, fallback);
 
     jumpIfMetatablePresent(build, table, fallback);
     jumpIfTableIsReadOnly(build, table, fallback);
@@ -1284,7 +1434,7 @@ void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
     // unsigned(index - 1) < unsigned(h->sizearray)
     build.cmp(dword[table + offsetof(Table, sizearray)], eax);
-    build.jcc(Condition::BelowEqual, fallback);
+    build.jcc(ConditionX64::BelowEqual, fallback);
 
     jumpIfMetatablePresent(build, table, fallback);
 
@@ -1296,7 +1446,7 @@ void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
 void emitInstGetTableFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
 {
-    callGetTable(build, LUAU_INSN_B(*pc), luauRegValue(LUAU_INSN_C(*pc)), LUAU_INSN_A(*pc), pcpos);
+    callGetTable(build, LUAU_INSN_B(*pc), luauRegAddress(LUAU_INSN_C(*pc)), LUAU_INSN_A(*pc), pcpos);
 }
 
 void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
@@ -1319,7 +1469,7 @@ void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
     // unsigned(index - 1) < unsigned(h->sizearray)
     build.cmp(dword[table + offsetof(Table, sizearray)], eax);
-    build.jcc(Condition::BelowEqual, fallback);
+    build.jcc(ConditionX64::BelowEqual, fallback);
 
     jumpIfMetatablePresent(build, table, fallback);
     jumpIfTableIsReadOnly(build, table, fallback);
@@ -1335,7 +1485,7 @@ void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
 
 void emitInstSetTableFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
 {
-    callSetTable(build, LUAU_INSN_B(*pc), luauRegValue(LUAU_INSN_C(*pc)), LUAU_INSN_A(*pc), pcpos);
+    callSetTable(build, LUAU_INSN_B(*pc), luauRegAddress(LUAU_INSN_C(*pc)), LUAU_INSN_A(*pc), pcpos);
 }
 
 void emitInstGetImport(AssemblyBuilderX64& build, const Instruction* pc, Label& fallback)
@@ -1348,7 +1498,7 @@ void emitInstGetImport(AssemblyBuilderX64& build, const Instruction* pc, Label&
     // note: if import failed, k[] is nil; we could check this during codegen, but we instead use runtime fallback
     // this allows us to handle ahead-of-time codegen smoothly when an import fails to resolve at runtime
     build.cmp(luauConstantTag(k), LUA_TNIL);
-    build.jcc(Condition::Equal, fallback);
+    build.jcc(ConditionX64::Equal, fallback);
 
     build.vmovups(xmm0, luauConstant(k));
     build.vmovups(luauReg(ra), xmm0);
@@ -1367,7 +1517,7 @@ void emitInstGetImportFallback(AssemblyBuilderX64& build, const Instruction* pc,
     build.mov(rArg1, rState);
     build.mov(rArg2, qword[rax + offsetof(Closure, env)]);
     build.mov(rArg3, rConstants);
-    build.mov(rArg4, aux);
+    build.mov(dwordReg(rArg4), aux);
 
     if (build.abi == ABIX64::Windows)
         build.mov(sArg5, 0);
@@ -1470,8 +1620,8 @@ void emitInstConcat(AssemblyBuilderX64& build, const Instruction* pc, int pcpos,
 
     // luaV_concat(L, c - b + 1, c)
     build.mov(rArg1, rState);
-    build.mov(rArg2, rc - rb + 1);
+    build.mov(dwordReg(rArg2), rc - rb + 1);
-    build.mov(rArg3, rc);
+    build.mov(dwordReg(rArg3), rc);
     build.call(qword[rNativeContext + offsetof(NativeContext, luaV_concat)]);
 
     emitUpdateBase(build);

CodeGen/src/EmitInstructionX64.h

@@ -14,7 +14,7 @@ namespace CodeGen
 {
 
 class AssemblyBuilderX64;
-enum class Condition;
+enum class ConditionX64 : uint8_t;
 struct Label;
 struct ModuleHelpers;
 
@@ -24,14 +24,15 @@ void emitInstLoadN(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstLoadK(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstLoadKX(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc);
+void emitInstCall(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstReturn(AssemblyBuilderX64& build, ModuleHelpers& helpers, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJump(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpBack(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpIf(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
 void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_, Label& fallback);
 void emitInstJumpIfEqFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
-void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond, Label& fallback);
+void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, ConditionX64 cond, Label& fallback);
-void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond);
+void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, ConditionX64 cond);
 void emitInstJumpX(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);

CodeGen/src/Fallbacks.h

@@ -10,84 +10,15 @@ typedef uint32_t Instruction;
 typedef struct lua_TValue TValue;
 typedef TValue* StkId;
 
-const Instruction* execute_LOP_NOP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LOADNIL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LOADB(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LOADN(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LOADK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MOVE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_GETGLOBAL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_SETGLOBAL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_GETUPVAL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SETUPVAL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_CLOSEUPVALS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_GETIMPORT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_GETTABLEKS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_SETTABLEKS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_GETTABLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SETTABLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_GETTABLEN(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SETTABLEN(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_NEWCLOSURE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_NAMECALL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_CALL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_RETURN(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIF(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFNOT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFEQ(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFNOTEQ(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFNOTLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFLT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPIFNOTLT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_ADD(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SUB(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MUL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DIV(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MOD(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_POW(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_ADDK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SUBK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MULK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DIVK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MODK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_POWK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_AND(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_OR(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_ANDK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_ORK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_CONCAT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_NOT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_MINUS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LENGTH(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_NEWTABLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DUPTABLE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_SETLIST(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FORNPREP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FORNLOOP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_FORGPREP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FORGLOOP(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FORGPREP_INEXT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DEP_FORGLOOP_INEXT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FORGPREP_NEXT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DEP_FORGLOOP_NEXT(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_GETVARARGS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_DUPCLOSURE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_PREPVARARGS(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPBACK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_LOADKX(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPX(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FASTCALL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_COVERAGE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_CAPTURE(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DEP_JUMPIFEQK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_DEP_JUMPIFNOTEQK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FASTCALL1(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FASTCALL2(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_FASTCALL2K(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 const Instruction* execute_LOP_BREAK(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPXEQKNIL(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPXEQKB(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPXEQKN(lua_State* L, const Instruction* pc, StkId base, TValue* k);
-const Instruction* execute_LOP_JUMPXEQKS(lua_State* L, const Instruction* pc, StkId base, TValue* k);

CodeGen/src/NativeState.cpp

@@ -35,10 +35,9 @@ NativeState::~NativeState() = default;
 
 void initFallbackTable(NativeState& data)
 {
-    // TODO: lvmexecute_split.py could be taught to generate a subset of instructions we actually need
+    // When fallback is completely removed, remove it from includeInsts list in lvmexecute_split.py
     CODEGEN_SET_FALLBACK(LOP_NEWCLOSURE, 0);
     CODEGEN_SET_FALLBACK(LOP_NAMECALL, 0);
-    CODEGEN_SET_FALLBACK(LOP_CALL, kFallbackUpdateCi | kFallbackCheckInterrupt);
     CODEGEN_SET_FALLBACK(LOP_FORGPREP, kFallbackUpdatePc);
     CODEGEN_SET_FALLBACK(LOP_GETVARARGS, 0);
     CODEGEN_SET_FALLBACK(LOP_DUPCLOSURE, 0);
@@ -86,6 +85,8 @@ void initHelperFunctions(NativeState& data)
     data.context.forgLoopNodeIter = forgLoopNodeIter;
     data.context.forgLoopNonTableFallback = forgLoopNonTableFallback;
     data.context.forgPrepXnextFallback = forgPrepXnextFallback;
+    data.context.callProlog = callProlog;
+    data.context.callEpilogC = callEpilogC;
 }
 
 } // namespace CodeGen

CodeGen/src/NativeState.h

@@ -26,8 +26,6 @@ class UnwindBuilder;
 using FallbackFn = const Instruction*(lua_State* L, const Instruction* pc, StkId base, TValue* k);
 
 constexpr uint8_t kFallbackUpdatePc = 1 << 0;
-constexpr uint8_t kFallbackUpdateCi = 1 << 1;
-constexpr uint8_t kFallbackCheckInterrupt = 1 << 2;
 
 struct NativeFallback
 {
@@ -37,7 +35,8 @@ struct NativeFallback
 
 struct NativeProto
 {
-    uintptr_t* instTargets = nullptr;
+    uintptr_t entryTarget = 0;
+    uintptr_t* instTargets = nullptr; // TODO: NativeProto should be variable-size with all target embedded
 
     Proto* proto = nullptr;
     uint32_t location = 0;
@@ -85,6 +84,8 @@ struct NativeContext
     bool (*forgLoopNodeIter)(lua_State* L, Table* h, int index, TValue* ra) = nullptr;
     bool (*forgLoopNonTableFallback)(lua_State* L, int insnA, int aux) = nullptr;
     void (*forgPrepXnextFallback)(lua_State* L, TValue* ra, int pc) = nullptr;
+    Closure* (*callProlog)(lua_State* L, TValue* ra, StkId argtop, int nresults) = nullptr;
+    void (*callEpilogC)(lua_State* L, int nresults, int n) = nullptr;
 };
 
 struct NativeState

Sources.cmake

@@ -55,18 +55,23 @@ target_sources(Luau.Compiler PRIVATE
 
 # Luau.CodeGen Sources
 target_sources(Luau.CodeGen PRIVATE
+    CodeGen/include/Luau/AddressA64.h
+    CodeGen/include/Luau/AssemblyBuilderA64.h
     CodeGen/include/Luau/AssemblyBuilderX64.h
     CodeGen/include/Luau/CodeAllocator.h
     CodeGen/include/Luau/CodeBlockUnwind.h
     CodeGen/include/Luau/CodeGen.h
-    CodeGen/include/Luau/Condition.h
+    CodeGen/include/Luau/ConditionA64.h
+    CodeGen/include/Luau/ConditionX64.h
     CodeGen/include/Luau/Label.h
     CodeGen/include/Luau/OperandX64.h
+    CodeGen/include/Luau/RegisterA64.h
     CodeGen/include/Luau/RegisterX64.h
     CodeGen/include/Luau/UnwindBuilder.h
     CodeGen/include/Luau/UnwindBuilderDwarf2.h
     CodeGen/include/Luau/UnwindBuilderWin.h
 
+    CodeGen/src/AssemblyBuilderA64.cpp
     CodeGen/src/AssemblyBuilderX64.cpp
     CodeGen/src/CodeAllocator.cpp
     CodeGen/src/CodeBlockUnwind.cpp
@@ -103,6 +108,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/include/Luau/BuiltinDefinitions.h
     Analysis/include/Luau/Clone.h
     Analysis/include/Luau/Config.h
+    Analysis/include/Luau/Connective.h
     Analysis/include/Luau/Constraint.h
     Analysis/include/Luau/ConstraintGraphBuilder.h
     Analysis/include/Luau/ConstraintSolver.h
@@ -156,6 +162,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/src/BuiltinDefinitions.cpp
     Analysis/src/Clone.cpp
     Analysis/src/Config.cpp
+    Analysis/src/Connective.cpp
     Analysis/src/Constraint.cpp
     Analysis/src/ConstraintGraphBuilder.cpp
     Analysis/src/ConstraintSolver.cpp
@@ -299,6 +306,7 @@ if(TARGET Luau.UnitTest)
         tests/AstQueryDsl.cpp
         tests/ConstraintGraphBuilderFixture.cpp
         tests/Fixture.cpp
+        tests/AssemblyBuilderA64.test.cpp
         tests/AssemblyBuilderX64.test.cpp
         tests/AstJsonEncoder.test.cpp
         tests/AstQuery.test.cpp

VM/include/luaconf.h

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

VM/src/lbuiltins.cpp

@@ -96,7 +96,6 @@ static int luauF_atan(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
-LUAU_DISPATCH_SSE41
 static int luauF_ceil(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -160,7 +159,6 @@ static int luauF_exp(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
-LUAU_DISPATCH_SSE41
 static int luauF_floor(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -938,7 +936,6 @@ static int luauF_sign(lua_State* L, StkId res, TValue* arg0, int nresults, StkId
 }
 
 LUAU_FASTMATH_BEGIN
-LUAU_DISPATCH_SSE41
 static int luauF_round(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
     if (nparams >= 1 && nresults <= 1 && ttisnumber(arg0))
@@ -1326,9 +1323,9 @@ const luau_FastFunction luauF_table[256] = {
     luauF_getmetatable,
     luauF_setmetatable,
 
-    // When adding builtins, add them above this line; what follows is 64 "dummy" entries with luauF_missing fallback.
+// When adding builtins, add them above this line; what follows is 64 "dummy" entries with luauF_missing fallback.
-    // This is important so that older versions of the runtime that don't support newer builtins automatically fall back via luauF_missing.
+// This is important so that older versions of the runtime that don't support newer builtins automatically fall back via luauF_missing.
-    // Given the builtin addition velocity this should always provide a larger compatibility window than bytecode versions suggest.
+// Given the builtin addition velocity this should always provide a larger compatibility window than bytecode versions suggest.
 #define MISSING8 luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing, luauF_missing
 
     MISSING8,

VM/src/lnumutils.h

@@ -34,7 +34,6 @@ inline bool luai_vecisnan(const float* a)
 }
 
 LUAU_FASTMATH_BEGIN
-// TODO: LUAU_DISPATCH_SSE41 would be nice here, but clang-14 doesn't support it correctly on inline functions...
 inline double luai_nummod(double a, double b)
 {
     return a - floor(a / b) * b;

tests/AssemblyBuilderA64.test.cpp

@@ -0,0 +1,221 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/AssemblyBuilderA64.h"
+#include "Luau/StringUtils.h"
+
+#include "doctest.h"
+
+#include <string.h>
+
+using namespace Luau::CodeGen;
+
+static std::string bytecodeAsArray(const std::vector<uint8_t>& bytecode)
+{
+    std::string result = "{";
+
+    for (size_t i = 0; i < bytecode.size(); i++)
+        Luau::formatAppend(result, "%s0x%02x", i == 0 ? "" : ", ", bytecode[i]);
+
+    return result.append("}");
+}
+
+static std::string bytecodeAsArray(const std::vector<uint32_t>& code)
+{
+    std::string result = "{";
+
+    for (size_t i = 0; i < code.size(); i++)
+        Luau::formatAppend(result, "%s0x%08x", i == 0 ? "" : ", ", code[i]);
+
+    return result.append("}");
+}
+
+class AssemblyBuilderA64Fixture
+{
+public:
+    bool check(void (*f)(AssemblyBuilderA64& build), std::vector<uint32_t> code, std::vector<uint8_t> data = {})
+    {
+        AssemblyBuilderA64 build(/* logText= */ false);
+
+        f(build);
+
+        build.finalize();
+
+        if (build.code != code)
+        {
+            printf("Expected code: %s\nReceived code: %s\n", bytecodeAsArray(code).c_str(), bytecodeAsArray(build.code).c_str());
+            return false;
+        }
+
+        if (build.data != data)
+        {
+            printf("Expected data: %s\nReceived data: %s\n", bytecodeAsArray(data).c_str(), bytecodeAsArray(build.data).c_str());
+            return false;
+        }
+
+        return true;
+    }
+};
+
+// armconverter.com can be used to validate instruction sequences
+TEST_SUITE_BEGIN("A64Assembly");
+
+#define SINGLE_COMPARE(inst, ...) \
+    CHECK(check( \
+        [](AssemblyBuilderA64& build) { \
+            build.inst; \
+        }, \
+        {__VA_ARGS__}))
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "Unary")
+{
+    SINGLE_COMPARE(neg(x0, x1), 0xCB0103E0);
+    SINGLE_COMPARE(neg(w0, w1), 0x4B0103E0);
+
+    SINGLE_COMPARE(clz(x0, x1), 0xDAC01020);
+    SINGLE_COMPARE(clz(w0, w1), 0x5AC01020);
+    SINGLE_COMPARE(rbit(x0, x1), 0xDAC00020);
+    SINGLE_COMPARE(rbit(w0, w1), 0x5AC00020);
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "Binary")
+{
+    // reg, reg
+    SINGLE_COMPARE(add(x0, x1, x2), 0x8B020020);
+    SINGLE_COMPARE(add(w0, w1, w2), 0x0B020020);
+    SINGLE_COMPARE(add(x0, x1, x2, 7), 0x8B021C20);
+    SINGLE_COMPARE(sub(x0, x1, x2), 0xCB020020);
+    SINGLE_COMPARE(and_(x0, x1, x2), 0x8A020020);
+    SINGLE_COMPARE(orr(x0, x1, x2), 0xAA020020);
+    SINGLE_COMPARE(eor(x0, x1, x2), 0xCA020020);
+    SINGLE_COMPARE(lsl(x0, x1, x2), 0x9AC22020);
+    SINGLE_COMPARE(lsl(w0, w1, w2), 0x1AC22020);
+    SINGLE_COMPARE(lsr(x0, x1, x2), 0x9AC22420);
+    SINGLE_COMPARE(asr(x0, x1, x2), 0x9AC22820);
+    SINGLE_COMPARE(ror(x0, x1, x2), 0x9AC22C20);
+
+    // reg, imm
+    SINGLE_COMPARE(add(x3, x7, 78), 0x910138E3);
+    SINGLE_COMPARE(add(w3, w7, 78), 0x110138E3);
+    SINGLE_COMPARE(sub(w3, w7, 78), 0x510138E3);
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "Loads")
+{
+    // address forms
+    SINGLE_COMPARE(ldr(x0, x1), 0xF9400020);
+    SINGLE_COMPARE(ldr(x0, AddressA64(x1, 8)), 0xF9400420);
+    SINGLE_COMPARE(ldr(x0, AddressA64(x1, x7)), 0xF8676820);
+
+    // load sizes
+    SINGLE_COMPARE(ldr(x0, x1), 0xF9400020);
+    SINGLE_COMPARE(ldr(w0, x1), 0xB9400020);
+    SINGLE_COMPARE(ldrb(w0, x1), 0x39400020);
+    SINGLE_COMPARE(ldrh(w0, x1), 0x79400020);
+    SINGLE_COMPARE(ldrsb(x0, x1), 0x39800020);
+    SINGLE_COMPARE(ldrsb(w0, x1), 0x39C00020);
+    SINGLE_COMPARE(ldrsh(x0, x1), 0x79800020);
+    SINGLE_COMPARE(ldrsh(w0, x1), 0x79C00020);
+    SINGLE_COMPARE(ldrsw(x0, x1), 0xB9800020);
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "Stores")
+{
+    // address forms
+    SINGLE_COMPARE(str(x0, x1), 0xF9000020);
+    SINGLE_COMPARE(str(x0, AddressA64(x1, 8)), 0xF9000420);
+    SINGLE_COMPARE(str(x0, AddressA64(x1, x7)), 0xF8276820);
+
+    // store sizes
+    SINGLE_COMPARE(str(x0, x1), 0xF9000020);
+    SINGLE_COMPARE(str(w0, x1), 0xB9000020);
+    SINGLE_COMPARE(strb(w0, x1), 0x39000020);
+    SINGLE_COMPARE(strh(w0, x1), 0x79000020);
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "Moves")
+{
+    SINGLE_COMPARE(mov(x0, x1), 0xAA0103E0);
+    SINGLE_COMPARE(mov(w0, w1), 0x2A0103E0);
+    SINGLE_COMPARE(mov(x0, 42), 0xD2800540);
+    SINGLE_COMPARE(mov(w0, 42), 0x52800540);
+    SINGLE_COMPARE(movk(x0, 42, 16), 0xF2A00540);
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderA64Fixture, "ControlFlow")
+{
+    // Jump back
+    CHECK(check(
+        [](AssemblyBuilderA64& build) {
+            Label start = build.setLabel();
+            build.mov(x0, x1);
+            build.b(ConditionA64::Equal, start);
+        },
+        {0xAA0103E0, 0x54FFFFE0}));
+
+    // Jump forward
+    CHECK(check(
+        [](AssemblyBuilderA64& build) {
+            Label skip;
+            build.b(ConditionA64::Equal, skip);
+            build.mov(x0, x1);
+            build.setLabel(skip);
+        },
+        {0x54000040, 0xAA0103E0}));
+
+    // Jumps
+    CHECK(check(
+        [](AssemblyBuilderA64& build) {
+            Label skip;
+            build.b(ConditionA64::Equal, skip);
+            build.cbz(x0, skip);
+            build.cbnz(x0, skip);
+            build.setLabel(skip);
+        },
+        {0x54000060, 0xB4000040, 0xB5000020}));
+
+    // Basic control flow
+    SINGLE_COMPARE(ret(), 0xD65F03C0);
+}
+
+TEST_CASE("LogTest")
+{
+    AssemblyBuilderA64 build(/* logText= */ true);
+
+    build.add(w0, w1, w2);
+    build.add(x0, x1, x2, 2);
+    build.add(w7, w8, 5);
+    build.add(x7, x8, 5);
+    build.ldr(x7, x8);
+    build.ldr(x7, AddressA64(x8, 8));
+    build.ldr(x7, AddressA64(x8, x9));
+    build.mov(x1, x2);
+    build.movk(x1, 42, 16);
+
+    Label l;
+    build.b(ConditionA64::Plus, l);
+    build.cbz(x7, l);
+
+    build.setLabel(l);
+    build.ret();
+
+    build.finalize();
+
+    std::string expected = R"(
+ add         w0,w1,w2
+ add         x0,x1,x2 LSL #2
+ add         w7,w8,#5
+ add         x7,x8,#5
+ ldr         x7,[x8]
+ ldr         x7,[x8,#8]
+ ldr         x7,[x8,x9]
+ mov         x1,x2
+ movk        x1,#42 LSL #16
+ b.pl        .L1
+ cbz         x7,.L1
+.L1:
+ ret
+)";
+
+    CHECK("\n" + build.text == expected);
+}
+
+TEST_SUITE_END();

tests/AssemblyBuilderX64.test.cpp

@@ -8,7 +8,7 @@
 
 using namespace Luau::CodeGen;
 
-std::string bytecodeAsArray(const std::vector<uint8_t>& bytecode)
+static std::string bytecodeAsArray(const std::vector<uint8_t>& bytecode)
 {
     std::string result = "{";
 
@@ -21,7 +21,7 @@ std::string bytecodeAsArray(const std::vector<uint8_t>& bytecode)
 class AssemblyBuilderX64Fixture
 {
 public:
-    void check(void (*f)(AssemblyBuilderX64& build), std::vector<uint8_t> code, std::vector<uint8_t> data = {})
+    bool check(void (*f)(AssemblyBuilderX64& build), std::vector<uint8_t> code, std::vector<uint8_t> data = {})
     {
         AssemblyBuilderX64 build(/* logText= */ false);
 
@@ -32,25 +32,27 @@ public:
         if (build.code != code)
         {
             printf("Expected code: %s\nReceived code: %s\n", bytecodeAsArray(code).c_str(), bytecodeAsArray(build.code).c_str());
-            CHECK(false);
+            return false;
         }
 
         if (build.data != data)
         {
             printf("Expected data: %s\nReceived data: %s\n", bytecodeAsArray(data).c_str(), bytecodeAsArray(build.data).c_str());
-            CHECK(false);
+            return false;
         }
+
+        return true;
     }
 };
 
 TEST_SUITE_BEGIN("x64Assembly");
 
 #define SINGLE_COMPARE(inst, ...) \
-    check( \
+    CHECK(check( \
         [](AssemblyBuilderX64& build) { \
             build.inst; \
         }, \
-        {__VA_ARGS__})
+        {__VA_ARGS__}))
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "BaseBinaryInstructionForms")
 {
@@ -236,9 +238,9 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "FormsOfShift")
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "FormsOfLea")
 {
-    SINGLE_COMPARE(lea(rax, qword[rdx + rcx]), 0x48, 0x8d, 0x04, 0x0a);
+    SINGLE_COMPARE(lea(rax, addr[rdx + rcx]), 0x48, 0x8d, 0x04, 0x0a);
-    SINGLE_COMPARE(lea(rax, qword[rdx + rax * 4]), 0x48, 0x8d, 0x04, 0x82);
+    SINGLE_COMPARE(lea(rax, addr[rdx + rax * 4]), 0x48, 0x8d, 0x04, 0x82);
-    SINGLE_COMPARE(lea(rax, qword[r13 + r12 * 4 + 4]), 0x4b, 0x8d, 0x44, 0xa5, 0x04);
+    SINGLE_COMPARE(lea(rax, addr[r13 + r12 * 4 + 4]), 0x4b, 0x8d, 0x44, 0xa5, 0x04);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "FormsOfAbsoluteJumps")
@@ -280,34 +282,34 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "NopForms")
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AlignmentForms")
 {
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             build.ret();
             build.align(8, AlignmentDataX64::Nop);
         },
-        {0xc3, 0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00});
+        {0xc3, 0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00}));
 
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             build.ret();
             build.align(32, AlignmentDataX64::Nop);
         },
         {0xc3, 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00, 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00, 0x66, 0x0f, 0x1f, 0x84,
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x0f, 0x1f, 0x40, 0x00});
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x0f, 0x1f, 0x40, 0x00}));
 
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             build.ret();
             build.align(8, AlignmentDataX64::Int3);
         },
-        {0xc3, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc});
+        {0xc3, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc}));
 
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             build.ret();
             build.align(8, AlignmentDataX64::Ud2);
         },
-        {0xc3, 0x0f, 0x0b, 0x0f, 0x0b, 0x0f, 0x0b, 0xcc});
+        {0xc3, 0x0f, 0x0b, 0x0f, 0x0b, 0x0f, 0x0b, 0xcc}));
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AlignmentOverflow")
@@ -349,40 +351,40 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AlignmentOverflow")
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "ControlFlow")
 {
     // Jump back
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             Label start = build.setLabel();
             build.add(rsi, 1);
             build.cmp(rsi, rdi);
-            build.jcc(Condition::Equal, start);
+            build.jcc(ConditionX64::Equal, start);
         },
-        {0x48, 0x83, 0xc6, 0x01, 0x48, 0x3b, 0xf7, 0x0f, 0x84, 0xf3, 0xff, 0xff, 0xff});
+        {0x48, 0x83, 0xc6, 0x01, 0x48, 0x3b, 0xf7, 0x0f, 0x84, 0xf3, 0xff, 0xff, 0xff}));
 
     // Jump back, but the label is set before use
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             Label start;
             build.add(rsi, 1);
             build.setLabel(start);
             build.cmp(rsi, rdi);
-            build.jcc(Condition::Equal, start);
+            build.jcc(ConditionX64::Equal, start);
         },
-        {0x48, 0x83, 0xc6, 0x01, 0x48, 0x3b, 0xf7, 0x0f, 0x84, 0xf7, 0xff, 0xff, 0xff});
+        {0x48, 0x83, 0xc6, 0x01, 0x48, 0x3b, 0xf7, 0x0f, 0x84, 0xf7, 0xff, 0xff, 0xff}));
 
     // Jump forward
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             Label skip;
 
             build.cmp(rsi, rdi);
-            build.jcc(Condition::Greater, skip);
+            build.jcc(ConditionX64::Greater, skip);
             build.or_(rdi, 0x3e);
             build.setLabel(skip);
         },
-        {0x48, 0x3b, 0xf7, 0x0f, 0x8f, 0x04, 0x00, 0x00, 0x00, 0x48, 0x83, 0xcf, 0x3e});
+        {0x48, 0x3b, 0xf7, 0x0f, 0x8f, 0x04, 0x00, 0x00, 0x00, 0x48, 0x83, 0xcf, 0x3e}));
 
     // Regular jump
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             Label skip;
 
@@ -390,12 +392,12 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "ControlFlow")
             build.and_(rdi, 0x3e);
             build.setLabel(skip);
         },
-        {0xe9, 0x04, 0x00, 0x00, 0x00, 0x48, 0x83, 0xe7, 0x3e});
+        {0xe9, 0x04, 0x00, 0x00, 0x00, 0x48, 0x83, 0xe7, 0x3e}));
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "LabelCall")
 {
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             Label fnB;
 
@@ -404,10 +406,10 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "LabelCall")
             build.ret();
 
             build.setLabel(fnB);
-            build.lea(rax, qword[rcx + 0x1f]);
+            build.lea(rax, addr[rcx + 0x1f]);
             build.ret();
         },
-        {0x48, 0x83, 0xe1, 0x3e, 0xe8, 0x01, 0x00, 0x00, 0x00, 0xc3, 0x48, 0x8d, 0x41, 0x1f, 0xc3});
+        {0x48, 0x83, 0xe1, 0x3e, 0xe8, 0x01, 0x00, 0x00, 0x00, 0xc3, 0x48, 0x8d, 0x41, 0x1f, 0xc3}));
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXBinaryInstructionForms")
@@ -518,7 +520,7 @@ TEST_CASE("LogTest")
 
     Label start = build.setLabel();
     build.cmp(rsi, rdi);
-    build.jcc(Condition::Equal, start);
+    build.jcc(ConditionX64::Equal, start);
 
     build.jmp(qword[rdx]);
     build.vaddps(ymm9, ymm12, ymmword[rbp + 0xc]);
@@ -548,7 +550,7 @@ TEST_CASE("LogTest")
 
     build.finalize();
 
-    bool same = "\n" + build.text == R"(
+    std::string expected = R"(
  push        r12
 ; align 8
  nop         word ptr[rax+rax] ; 6-byte nop
@@ -588,13 +590,14 @@ TEST_CASE("LogTest")
  nop         dword ptr[rax+rax] ; 8-byte nop
  nop         word ptr[rax+rax] ; 9-byte nop
 )";
-    CHECK(same);
+
+    CHECK("\n" + build.text == expected);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "Constants")
 {
     // clang-format off
-    check(
+    CHECK(check(
         [](AssemblyBuilderX64& build) {
             build.xor_(rax, rax);
             build.add(rax, build.i64(0x1234567887654321));
@@ -625,7 +628,7 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "Constants")
             0x00, 0x00, 0x00, 0x00, // padding to align f64
             0x00, 0x00, 0x80, 0x3f,
             0x21, 0x43, 0x65, 0x87, 0x78, 0x56, 0x34, 0x12,
-        });
+        }));
     // clang-format on
 }
 

tests/CodeAllocator.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/AssemblyBuilderX64.h"
+#include "Luau/AssemblyBuilderA64.h"
 #include "Luau/CodeAllocator.h"
 #include "Luau/CodeBlockUnwind.h"
 #include "Luau/UnwindBuilder.h"
@@ -207,7 +208,7 @@ constexpr RegisterX64 rArg3 = rdx;
 constexpr RegisterX64 rNonVol1 = r12;
 constexpr RegisterX64 rNonVol2 = rbx;
 
-TEST_CASE("GeneratedCodeExecution")
+TEST_CASE("GeneratedCodeExecutionX64")
 {
     AssemblyBuilderX64 build(/* logText= */ false);
 
@@ -241,7 +242,7 @@ void throwing(int64_t arg)
     throw std::runtime_error("testing");
 }
 
-TEST_CASE("GeneratedCodeExecutionWithThrow")
+TEST_CASE("GeneratedCodeExecutionWithThrowX64")
 {
     AssemblyBuilderX64 build(/* logText= */ false);
 
@@ -267,7 +268,7 @@ TEST_CASE("GeneratedCodeExecutionWithThrow")
     build.sub(rsp, stackSize + localsSize);
     unwind->allocStack(stackSize + localsSize);
 
-    build.lea(rbp, qword[rsp + stackSize]);
+    build.lea(rbp, addr[rsp + stackSize]);
     unwind->setupFrameReg(rbp, stackSize);
 
     unwind->finish();
@@ -281,7 +282,7 @@ TEST_CASE("GeneratedCodeExecutionWithThrow")
     build.call(rNonVol2);
 
     // Epilogue
-    build.lea(rsp, qword[rbp + localsSize]);
+    build.lea(rsp, addr[rbp + localsSize]);
     build.pop(rbp);
     build.pop(rNonVol2);
     build.pop(rNonVol1);
@@ -317,7 +318,7 @@ TEST_CASE("GeneratedCodeExecutionWithThrow")
     }
 }
 
-TEST_CASE("GeneratedCodeExecutionWithThrowOutsideTheGate")
+TEST_CASE("GeneratedCodeExecutionWithThrowOutsideTheGateX64")
 {
     AssemblyBuilderX64 build(/* logText= */ false);
 
@@ -351,7 +352,7 @@ TEST_CASE("GeneratedCodeExecutionWithThrowOutsideTheGate")
     build.sub(rsp, stackSize + localsSize);
     unwind->allocStack(stackSize + localsSize);
 
-    build.lea(rbp, qword[rsp + stackSize]);
+    build.lea(rbp, addr[rsp + stackSize]);
     unwind->setupFrameReg(rbp, stackSize);
 
     unwind->finish();
@@ -366,7 +367,7 @@ TEST_CASE("GeneratedCodeExecutionWithThrowOutsideTheGate")
     Label returnOffset = build.setLabel();
 
     // Epilogue
-    build.lea(rsp, qword[rbp + localsSize]);
+    build.lea(rsp, addr[rbp + localsSize]);
     build.pop(rbp);
     build.pop(r15);
     build.pop(r14);
@@ -432,4 +433,43 @@ TEST_CASE("GeneratedCodeExecutionWithThrowOutsideTheGate")
 
 #endif
 
+#if defined(__aarch64__)
+
+TEST_CASE("GeneratedCodeExecutionA64")
+{
+    AssemblyBuilderA64 build(/* logText= */ false);
+
+    Label skip;
+    build.cbz(x1, skip);
+    build.ldrsw(x1, x1);
+    build.cbnz(x1, skip);
+    build.mov(x1, 0); // doesn't execute due to cbnz above
+    build.setLabel(skip);
+
+    build.add(x1, x1, 1);
+    build.add(x0, x0, x1, /* LSL */ 1);
+    build.ret();
+
+    build.finalize();
+
+    size_t blockSize = 1024 * 1024;
+    size_t maxTotalSize = 1024 * 1024;
+    CodeAllocator allocator(blockSize, maxTotalSize);
+
+    uint8_t* nativeData;
+    size_t sizeNativeData;
+    uint8_t* nativeEntry;
+    REQUIRE(allocator.allocate(build.data.data(), build.data.size(), reinterpret_cast<uint8_t*>(build.code.data()), build.code.size() * 4, nativeData,
+        sizeNativeData, nativeEntry));
+    REQUIRE(nativeEntry);
+
+    using FunctionType = int64_t(int64_t, int*);
+    FunctionType* f = (FunctionType*)nativeEntry;
+    int input = 10;
+    int64_t result = f(20, &input);
+    CHECK(result == 42);
+}
+
+#endif
+
 TEST_SUITE_END();

tests/Conformance.test.cpp

@@ -539,8 +539,14 @@ TEST_CASE("Debugger")
     static bool singlestep = false;
     static int stephits = 0;
 
-    SUBCASE("") { singlestep = false; }
+    SUBCASE("")
-    SUBCASE("SingleStep") { singlestep = true; }
+    {
+        singlestep = false;
+    }
+    SUBCASE("SingleStep")
+    {
+        singlestep = true;
+    }
 
     breakhits = 0;
     interruptedthread = nullptr;

tests/Fixture.cpp

@@ -506,13 +506,14 @@ std::optional<TypeId> linearSearchForBinding(Scope* scope, const char* name)
     return std::nullopt;
 }
 
-void registerNotType(Fixture& fixture, TypeArena& arena)
+void registerHiddenTypes(Fixture& fixture, TypeArena& arena)
 {
     TypeId t = arena.addType(GenericTypeVar{"T"});
     GenericTypeDefinition genericT{t};
 
     ScopePtr moduleScope = fixture.frontend.getGlobalScope();
     moduleScope->exportedTypeBindings["Not"] = TypeFun{{genericT}, arena.addType(NegationTypeVar{t})};
+    moduleScope->exportedTypeBindings["fun"] = TypeFun{{}, fixture.singletonTypes->functionType};
 }
 
 void dump(const std::vector<Constraint>& constraints)

tests/Fixture.h

@@ -186,7 +186,7 @@ std::optional<TypeId> lookupName(ScopePtr scope, const std::string& name); // Wa
 
 std::optional<TypeId> linearSearchForBinding(Scope* scope, const char* name);
 
-void registerNotType(Fixture& fixture, TypeArena& arena);
+void registerHiddenTypes(Fixture& fixture, TypeArena& arena);
 
 } // namespace Luau
 

tests/Normalize.test.cpp

@@ -3,6 +3,7 @@
 #include "Fixture.h"
 
 #include "Luau/Common.h"
+#include "Luau/TypeVar.h"
 #include "doctest.h"
 
 #include "Luau/Normalize.h"
@@ -19,7 +20,7 @@ struct IsSubtypeFixture : Fixture
         return ::Luau::isSubtype(a, b, NotNull{getMainModule()->getModuleScope().get()}, singletonTypes, ice);
     }
 };
-}
+} // namespace
 
 void createSomeClasses(Frontend& frontend)
 {
@@ -109,12 +110,10 @@ TEST_CASE_FIXTURE(IsSubtypeFixture, "functions_and_any")
     TypeId a = requireType("a");
     TypeId b = requireType("b");
 
-    // Intuition:
+    // any makes things work even when it makes no sense.
-    //    We cannot use b where a is required because we cannot rely on b to return a string.
-    //    We cannot use a where b is required because we cannot rely on a to accept non-number arguments.
 
-    CHECK(!isSubtype(b, a));
+    CHECK(isSubtype(b, a));
-    CHECK(!isSubtype(a, b));
+    CHECK(isSubtype(a, b));
 }
 
 TEST_CASE_FIXTURE(IsSubtypeFixture, "variadic_functions_with_no_head")
@@ -199,7 +198,7 @@ TEST_CASE_FIXTURE(IsSubtypeFixture, "table_with_any_prop")
     TypeId b = requireType("b");
 
     CHECK(isSubtype(a, b));
-    CHECK(!isSubtype(b, a));
+    CHECK(isSubtype(b, a));
 }
 
 TEST_CASE_FIXTURE(IsSubtypeFixture, "intersection")
@@ -261,7 +260,7 @@ TEST_CASE_FIXTURE(IsSubtypeFixture, "tables")
     TypeId d = requireType("d");
 
     CHECK(isSubtype(a, b));
-    CHECK(!isSubtype(b, a));
+    CHECK(isSubtype(b, a));
 
     CHECK(!isSubtype(c, a));
     CHECK(!isSubtype(a, c));
@@ -394,7 +393,8 @@ TEST_SUITE_END();
 
 struct NormalizeFixture : Fixture
 {
-    ScopedFastFlag sff{"LuauNegatedStringSingletons", true};
+    ScopedFastFlag sff0{"LuauNegatedStringSingletons", true};
+    ScopedFastFlag sff1{"LuauNegatedFunctionTypes", true};
 
     TypeArena arena;
     InternalErrorReporter iceHandler;
@@ -403,16 +403,21 @@ struct NormalizeFixture : Fixture
 
     NormalizeFixture()
     {
-        registerNotType(*this, arena);
+        registerHiddenTypes(*this, arena);
     }
 
-    TypeId normal(const std::string& annotation)
+    const NormalizedType* toNormalizedType(const std::string& annotation)
     {
         CheckResult result = check("type _Res = " + annotation);
         LUAU_REQUIRE_NO_ERRORS(result);
         std::optional<TypeId> ty = lookupType("_Res");
         REQUIRE(ty);
-        const NormalizedType* norm = normalizer.normalize(*ty);
+        return normalizer.normalize(*ty);
+    }
+
+    TypeId normal(const std::string& annotation)
+    {
+        const NormalizedType* norm = toNormalizedType(annotation);
         REQUIRE(norm);
         return normalizer.typeFromNormal(*norm);
     }
@@ -476,6 +481,13 @@ TEST_CASE_FIXTURE(NormalizeFixture, "union_of_negations")
     )")));
 }
 
+TEST_CASE_FIXTURE(NormalizeFixture, "disjoint_negations_normalize_to_string")
+{
+    CHECK(R"(string)" == toString(normal(R"(
+        (string & Not<"hello"> & Not<"world">) | (string & Not<"goodbye">)
+    )")));
+}
+
 TEST_CASE_FIXTURE(NormalizeFixture, "negate_boolean")
 {
     CHECK("true" == toString(normal(R"(
@@ -490,10 +502,43 @@ TEST_CASE_FIXTURE(NormalizeFixture, "negate_boolean_2")
     )")));
 }
 
-TEST_CASE_FIXTURE(NormalizeFixture, "bare_negation")
+TEST_CASE_FIXTURE(NormalizeFixture, "intersect_function_and_top_function")
+{
+    CHECK("() -> ()" == toString(normal(R"(
+        fun & (() -> ())
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "intersect_function_and_top_function_reverse")
+{
+    CHECK("() -> ()" == toString(normal(R"(
+        (() -> ()) & fun
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "union_function_and_top_function")
+{
+    CHECK("function" == toString(normal(R"(
+        fun | (() -> ())
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "negated_function_is_anything_except_a_function")
+{
+    CHECK("(boolean | number | string | thread)?" == toString(normal(R"(
+        Not<fun>
+    )")));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "specific_functions_cannot_be_negated")
+{
+    CHECK(nullptr == toNormalizedType("Not<(boolean) -> boolean>"));
+}
+
+TEST_CASE_FIXTURE(NormalizeFixture, "bare_negated_boolean")
 {
     // TODO: We don't yet have a way to say number | string | thread | nil | Class | Table | Function
-    CHECK("(number | string | thread)?" == toString(normal(R"(
+    CHECK("(function | number | string | thread)?" == toString(normal(R"(
         Not<boolean>
     )")));
 }

tests/Parser.test.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/Parser.h"
 
+#include "AstQueryDsl.h"
 #include "Fixture.h"
 #include "ScopedFlags.h"
 
@@ -2775,4 +2776,51 @@ TEST_CASE_FIXTURE(Fixture, "get_a_nice_error_when_there_is_an_extra_comma_at_the
     CHECK(2 == f->generics.size);
 }
 
+TEST_CASE_FIXTURE(Fixture, "get_a_nice_error_when_there_is_no_comma_between_table_members")
+{
+    ScopedFastFlag luauTableConstructorRecovery{"LuauTableConstructorRecovery", true};
+
+    ParseResult result = tryParse(R"(
+        local t = {
+            first = 1
+            second = 2,
+            third = 3,
+            fouth = 4,
+        }
+    )");
+
+    REQUIRE(1 == result.errors.size());
+
+    CHECK(Location({3, 12}, {3, 18}) == result.errors[0].getLocation());
+    CHECK("Expected ',' after table constructor element" == result.errors[0].getMessage());
+
+    REQUIRE(1 == result.root->body.size);
+
+    AstExprTable* table = Luau::query<AstExprTable>(result.root);
+    REQUIRE(table);
+    CHECK(table->items.size == 4);
+}
+
+TEST_CASE_FIXTURE(Fixture, "get_a_nice_error_when_there_is_no_comma_after_last_table_member")
+{
+    ParseResult result = tryParse(R"(
+        local t = {
+            first = 1
+
+        local ok = true
+        local good = ok == true
+    )");
+
+    REQUIRE(1 == result.errors.size());
+
+    CHECK(Location({4, 8}, {4, 13}) == result.errors[0].getLocation());
+    CHECK("Expected '}' (to close '{' at line 2), got 'local'" == result.errors[0].getMessage());
+
+    REQUIRE(3 == result.root->body.size);
+
+    AstExprTable* table = Luau::query<AstExprTable>(result.root);
+    REQUIRE(table);
+    CHECK(table->items.size == 1);
+}
+
 TEST_SUITE_END();

tests/ToString.test.cpp

@@ -10,7 +10,6 @@
 using namespace Luau;
 
 LUAU_FASTFLAG(LuauRecursiveTypeParameterRestriction);
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked);
 LUAU_FASTFLAG(LuauFixNameMaps);
 LUAU_FASTFLAG(LuauFunctionReturnStringificationFixup);
 
@@ -270,16 +269,8 @@ TEST_CASE_FIXTURE(Fixture, "quit_stringifying_type_when_length_is_exceeded")
     o.maxTypeLength = 40;
     CHECK_EQ(toString(requireType("f0"), o), "() -> ()");
     CHECK_EQ(toString(requireType("f1"), o), "(() -> ()) -> () -> ()");
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-    {
+    CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-        CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-        CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-    }
-    else
-    {
-        CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... <TRUNCATED>");
-        CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... <TRUNCATED>");
-    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "stringifying_type_is_still_capped_when_exhaustive")
@@ -297,16 +288,8 @@ TEST_CASE_FIXTURE(Fixture, "stringifying_type_is_still_capped_when_exhaustive")
     o.maxTypeLength = 40;
     CHECK_EQ(toString(requireType("f0"), o), "() -> ()");
     CHECK_EQ(toString(requireType("f1"), o), "(() -> ()) -> () -> ()");
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-    {
+    CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-        CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-        CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... *TRUNCATED*");
-    }
-    else
-    {
-        CHECK_EQ(toString(requireType("f2"), o), "((() -> ()) -> () -> ()) -> (() -> ()) -> ... <TRUNCATED>");
-        CHECK_EQ(toString(requireType("f3"), o), "(((() -> ()) -> () -> ()) -> (() -> ()) -> ... <TRUNCATED>");
-    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "stringifying_table_type_correctly_use_matching_table_state_braces")
@@ -535,10 +518,7 @@ local function target(callback: nil) return callback(4, "hello") end
     )");
 
     LUAU_REQUIRE_ERRORS(result);
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("(nil) -> (*error-type*)", toString(requireType("target")));
-        CHECK_EQ("(nil) -> (*error-type*)", toString(requireType("target")));
-    else
-        CHECK_EQ("(nil) -> (<error-type>)", toString(requireType("target")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "toStringGenericPack")

tests/TypeInfer.anyerror.test.cpp

@@ -13,8 +13,6 @@
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
-
 TEST_SUITE_BEGIN("TypeInferAnyError");
 
 TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_returns_any")
@@ -96,10 +94,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_error")
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("a")));
-        CHECK_EQ("*error-type*", toString(requireType("a")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("a")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_error2")
@@ -115,10 +110,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_error2")
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("a")));
-        CHECK_EQ("*error-type*", toString(requireType("a")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("a")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "length_of_error_type_does_not_produce_an_error")
@@ -233,10 +225,7 @@ TEST_CASE_FIXTURE(Fixture, "calling_error_type_yields_error")
 
     CHECK_EQ("unknown", err->name);
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("a")));
-        CHECK_EQ("*error-type*", toString(requireType("a")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("a")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "chain_calling_error_type_yields_error")
@@ -245,10 +234,7 @@ TEST_CASE_FIXTURE(Fixture, "chain_calling_error_type_yields_error")
         local a = Utility.Create "Foo" {}
     )");
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("a")));
-        CHECK_EQ("*error-type*", toString(requireType("a")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("a")));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "replace_every_free_type_when_unifying_a_complex_function_with_any")

tests/TypeInfer.builtins.test.cpp

@@ -8,7 +8,6 @@
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked);
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 
 TEST_SUITE_BEGIN("BuiltinTests");
@@ -685,7 +684,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "select_with_variadic_typepack_tail")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    if (FFlag::DebugLuauDeferredConstraintResolution && FFlag::LuauSpecialTypesAsterisked)
+    if (FFlag::DebugLuauDeferredConstraintResolution)
     {
         CHECK_EQ("string", toString(requireType("foo")));
         CHECK_EQ("*error-type*", toString(requireType("bar")));
@@ -714,7 +713,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "select_with_variadic_typepack_tail_and_strin
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    if (FFlag::DebugLuauDeferredConstraintResolution && FFlag::LuauSpecialTypesAsterisked)
+    if (FFlag::DebugLuauDeferredConstraintResolution)
     {
         CHECK_EQ("string", toString(requireType("foo")));
         CHECK_EQ("string", toString(requireType("bar")));
@@ -1016,10 +1015,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "table_freeze_is_generic")
     CHECK_EQ("number", toString(requireType("a")));
     CHECK_EQ("string", toString(requireType("b")));
     CHECK_EQ("boolean", toString(requireType("c")));
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("d")));
-        CHECK_EQ("*error-type*", toString(requireType("d")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("d")));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "set_metatable_needs_arguments")

tests/TypeInfer.functions.test.cpp

@@ -15,7 +15,6 @@
 using namespace Luau;
 
 LUAU_FASTFLAG(LuauInstantiateInSubtyping);
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked);
 
 TEST_SUITE_BEGIN("TypeInferFunctions");
 
@@ -980,19 +979,13 @@ TEST_CASE_FIXTURE(Fixture, "function_cast_error_uses_correct_language")
     REQUIRE(tm1);
 
     CHECK_EQ("(string) -> number", toString(tm1->wantedType));
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("(string, *error-type*) -> number", toString(tm1->givenType));
-        CHECK_EQ("(string, *error-type*) -> number", toString(tm1->givenType));
-    else
-        CHECK_EQ("(string, <error-type>) -> number", toString(tm1->givenType));
 
     auto tm2 = get<TypeMismatch>(result.errors[1]);
     REQUIRE(tm2);
 
     CHECK_EQ("(number, number) -> (number, number)", toString(tm2->wantedType));
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("(string, *error-type*) -> number", toString(tm2->givenType));
-        CHECK_EQ("(string, *error-type*) -> number", toString(tm2->givenType));
-    else
-        CHECK_EQ("(string, <error-type>) -> number", toString(tm2->givenType));
 }
 
 TEST_CASE_FIXTURE(Fixture, "no_lossy_function_type")
@@ -1538,20 +1531,10 @@ function t:b() return 2 end -- not OK
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    if (FFlag::LuauSpecialTypesAsterisked)
+    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]));
+        toString(result.errors[0]));
-    }
-    else
-    {
-        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]));
-    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "too_few_arguments_variadic")
@@ -1779,7 +1762,72 @@ z = y -- Not OK, so the line is colorable
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(toString(result.errors[0]), "Type '((\"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)' could not be converted into '(\"blue\" | \"red\") -> (\"blue\" | \"red\") -> (\"blue\" | \"red\") -> false'; none of the intersection parts are compatible");
+    CHECK_EQ(toString(result.errors[0]),
+        "Type '((\"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)' could not be converted into '(\"blue\" | \"red\") -> (\"blue\" | \"red\") -> "
+        "(\"blue\" | \"red\") -> false'; none of the intersection parts are compatible");
+}
+
+TEST_CASE_FIXTURE(Fixture, "function_is_supertype_of_concrete_functions")
+{
+    ScopedFastFlag sff{"LuauNegatedFunctionTypes", true};
+    registerHiddenTypes(*this, frontend.globalTypes);
+
+    CheckResult result = check(R"(
+        function foo(f: fun) end
+
+        function a() end
+        function id(x) return x end
+
+        foo(a)
+        foo(id)
+        foo(foo)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "concrete_functions_are_not_supertypes_of_function")
+{
+    ScopedFastFlag sff{"LuauNegatedFunctionTypes", true};
+    registerHiddenTypes(*this, frontend.globalTypes);
+
+    CheckResult result = check(R"(
+        local a: fun = function() end
+
+        function one(arg: () -> ()) end
+        function two(arg: <T>(T) -> T) end
+
+        one(a)
+        two(a)
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+
+    CHECK(6 == result.errors[0].location.begin.line);
+    CHECK(7 == result.errors[1].location.begin.line);
+}
+
+TEST_CASE_FIXTURE(Fixture, "other_things_are_not_related_to_function")
+{
+    ScopedFastFlag sff{"LuauNegatedFunctionTypes", true};
+    registerHiddenTypes(*this, frontend.globalTypes);
+
+    CheckResult result = check(R"(
+        local a: fun = function() end
+        local b: {} = a
+        local c: boolean = a
+        local d: fun = true
+        local e: fun = {}
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(4, result);
+
+    CHECK(2 == result.errors[0].location.begin.line);
+    CHECK(3 == result.errors[1].location.begin.line);
+    CHECK(4 == result.errors[2].location.begin.line);
+    CHECK(5 == result.errors[3].location.begin.line);
 }
 
 TEST_SUITE_END();

tests/TypeInfer.generics.test.cpp

@@ -10,7 +10,6 @@
 #include "doctest.h"
 
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
 
 using namespace Luau;
 
@@ -1011,10 +1010,7 @@ TEST_CASE_FIXTURE(Fixture, "no_stack_overflow_from_quantifying")
 
     std::optional<TypeFun> t0 = getMainModule()->getModuleScope()->lookupType("t0");
     REQUIRE(t0);
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(t0->type));
-        CHECK_EQ("*error-type*", toString(t0->type));
-    else
-        CHECK_EQ("<error-type>", toString(t0->type));
 
     auto it = std::find_if(result.errors.begin(), result.errors.end(), [](TypeError& err) {
         return get<OccursCheckFailed>(err);

tests/TypeInfer.loops.test.cpp

@@ -13,7 +13,6 @@
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 
 TEST_SUITE_BEGIN("TypeInferLoops");
@@ -157,10 +156,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_on_error")
     LUAU_REQUIRE_ERROR_COUNT(2, result);
 
     TypeId p = requireType("p");
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(p));
-        CHECK_EQ("*error-type*", toString(p));
-    else
-        CHECK_EQ("<error-type>", toString(p));
 }
 
 TEST_CASE_FIXTURE(Fixture, "for_in_loop_on_non_function")

tests/TypeInfer.modules.test.cpp

@@ -14,8 +14,6 @@ LUAU_FASTFLAG(LuauInstantiateInSubtyping)
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
-
 TEST_SUITE_BEGIN("TypeInferModules");
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "dcr_require_basic")
@@ -176,10 +174,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "require_module_that_does_not_export")
 
     auto hootyType = requireType(bModule, "Hooty");
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(hootyType));
-        CHECK_EQ("*error-type*", toString(hootyType));
-    else
-        CHECK_EQ("<error-type>", toString(hootyType));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "warn_if_you_try_to_require_a_non_modulescript")
@@ -282,10 +277,7 @@ local ModuleA = require(game.A)
 
     std::optional<TypeId> oty = requireType("ModuleA");
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(*oty));
-        CHECK_EQ("*error-type*", toString(*oty));
-    else
-        CHECK_EQ("<error-type>", toString(*oty));
 }
 
 TEST_CASE_FIXTURE(BuiltinsFixture, "do_not_modify_imported_types")

tests/TypeInfer.negations.test.cpp

@@ -13,17 +13,17 @@ namespace
 struct NegationFixture : Fixture
 {
     TypeArena arena;
-    ScopedFastFlag sff[2] {
+    ScopedFastFlag sff[2]{
         {"LuauNegatedStringSingletons", true},
         {"LuauSubtypeNormalizer", true},
     };
 
     NegationFixture()
     {
-        registerNotType(*this, arena);
+        registerHiddenTypes(*this, arena);
     }
 };
-}
+} // namespace
 
 TEST_SUITE_BEGIN("Negations");
 

tests/TypeInfer.primitives.test.cpp

@@ -11,8 +11,6 @@
 
 #include "doctest.h"
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
-
 using namespace Luau;
 
 TEST_SUITE_BEGIN("TypeInferPrimitives");
@@ -49,10 +47,7 @@ TEST_CASE_FIXTURE(Fixture, "string_index")
     REQUIRE(nat);
     CHECK_EQ("string", toString(nat->ty));
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("t")));
-        CHECK_EQ("*error-type*", toString(requireType("t")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("t")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "string_method")

tests/TypeInfer.provisional.test.cpp

@@ -633,7 +633,7 @@ struct IsSubtypeFixture : Fixture
         return ::Luau::isSubtype(a, b, NotNull{getMainModule()->getModuleScope().get()}, singletonTypes, ice);
     }
 };
-}
+} // namespace
 
 TEST_CASE_FIXTURE(IsSubtypeFixture, "intersection_of_functions_of_different_arities")
 {

tests/TypeInfer.refinements.test.cpp

@@ -7,7 +7,6 @@
 
 #include "doctest.h"
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 
 using namespace Luau;
@@ -127,7 +126,7 @@ TEST_CASE_FIXTURE(Fixture, "invert_is_truthy_constraint")
     if (FFlag::DebugLuauDeferredConstraintResolution)
     {
         CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({3, 26})));
-        CHECK_EQ("(string?) & ~~~(false?)", toString(requireTypeAtPosition({5, 26})));
+        CHECK_EQ("(string?) & ~(false?)", toString(requireTypeAtPosition({5, 26})));
     }
     else
     {
@@ -153,7 +152,7 @@ TEST_CASE_FIXTURE(Fixture, "parenthesized_expressions_are_followed_through")
     if (FFlag::DebugLuauDeferredConstraintResolution)
     {
         CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({3, 26})));
-        CHECK_EQ("(string?) & ~~~(false?)", toString(requireTypeAtPosition({5, 26})));
+        CHECK_EQ("(string?) & ~(false?)", toString(requireTypeAtPosition({5, 26})));
     }
     else
     {
@@ -178,8 +177,16 @@ TEST_CASE_FIXTURE(Fixture, "and_constraint")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("string", toString(requireTypeAtPosition({3, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("number", toString(requireTypeAtPosition({4, 26})));
+    {
+        CHECK_EQ("(string?) & ~(false?)", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("(number?) & ~(false?)", toString(requireTypeAtPosition({4, 26})));
+    }
+    else
+    {
+        CHECK_EQ("string", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("number", toString(requireTypeAtPosition({4, 26})));
+    }
 
     CHECK_EQ("string?", toString(requireTypeAtPosition({6, 26})));
     CHECK_EQ("number?", toString(requireTypeAtPosition({7, 26})));
@@ -204,8 +211,16 @@ TEST_CASE_FIXTURE(Fixture, "not_and_constraint")
     CHECK_EQ("string?", toString(requireTypeAtPosition({3, 26})));
     CHECK_EQ("number?", toString(requireTypeAtPosition({4, 26})));
 
-    CHECK_EQ("string", toString(requireTypeAtPosition({6, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("number", toString(requireTypeAtPosition({7, 26})));
+    {
+        CHECK_EQ("(string?) & ~(false?)", toString(requireTypeAtPosition({6, 26})));
+        CHECK_EQ("(number?) & ~(false?)", toString(requireTypeAtPosition({7, 26})));
+    }
+    else
+    {
+        CHECK_EQ("string", toString(requireTypeAtPosition({6, 26})));
+        CHECK_EQ("number", toString(requireTypeAtPosition({7, 26})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "or_predicate_with_truthy_predicates")
@@ -227,8 +242,56 @@ TEST_CASE_FIXTURE(Fixture, "or_predicate_with_truthy_predicates")
     CHECK_EQ("string?", toString(requireTypeAtPosition({3, 26})));
     CHECK_EQ("number?", toString(requireTypeAtPosition({4, 26})));
 
-    CHECK_EQ("nil", toString(requireTypeAtPosition({6, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("nil", toString(requireTypeAtPosition({7, 26})));
+    {
+        CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({6, 26})));
+        CHECK_EQ("(number?) & ~~(false?)", toString(requireTypeAtPosition({7, 26})));
+    }
+    else
+    {
+        CHECK_EQ("nil", toString(requireTypeAtPosition({6, 26})));
+        CHECK_EQ("nil", toString(requireTypeAtPosition({7, 26})));
+    }
+}
+
+TEST_CASE_FIXTURE(Fixture, "a_and_b_or_a_and_c")
+{
+    CheckResult result = check(R"(
+        function f(a: string?, b: number?, c: boolean)
+            if (a and b) or (a and c) then
+                local foo = a
+                local bar = b
+                local baz = c
+            else
+                local foo = a
+                local bar = b
+                local baz = c
+            end
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+    {
+        CHECK_EQ("(string?) & (~(false?) | ~(false?))", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("number?", toString(requireTypeAtPosition({4, 28})));
+        CHECK_EQ("boolean", toString(requireTypeAtPosition({5, 28})));
+
+        CHECK_EQ("string?", toString(requireTypeAtPosition({7, 28})));
+        CHECK_EQ("number?", toString(requireTypeAtPosition({8, 28})));
+        CHECK_EQ("boolean", toString(requireTypeAtPosition({9, 28})));
+    }
+    else
+    {
+        CHECK_EQ("string", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("number?", toString(requireTypeAtPosition({4, 28})));
+        CHECK_EQ("true", toString(requireTypeAtPosition({5, 28}))); // oh no! :(
+
+        CHECK_EQ("string?", toString(requireTypeAtPosition({7, 28})));
+        CHECK_EQ("number?", toString(requireTypeAtPosition({8, 28})));
+        CHECK_EQ("boolean", toString(requireTypeAtPosition({9, 28})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "type_assertion_expr_carry_its_constraints")
@@ -244,8 +307,17 @@ TEST_CASE_FIXTURE(Fixture, "type_assertion_expr_carry_its_constraints")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("number", toString(requireTypeAtPosition({3, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("string", toString(requireTypeAtPosition({4, 26})));
+    {
+        CHECK_EQ("number?", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("string?", toString(requireTypeAtPosition({4, 26})));
+    }
+    else
+    {
+        // We're going to drop support for type refinements through type assertions.
+        CHECK_EQ("number", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("string", toString(requireTypeAtPosition({4, 26})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "typeguard_in_if_condition_position")
@@ -381,11 +453,22 @@ TEST_CASE_FIXTURE(Fixture, "lvalue_is_equal_to_another_lvalue")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "(number | string)?"); // a == b
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "boolean?");           // a == b
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "((number | string)?) & (boolean?)"); // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "((number | string)?) & (boolean?)"); // a == b
 
-    CHECK_EQ(toString(requireTypeAtPosition({5, 33})), "(number | string)?"); // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({5, 33})), "((number | string)?) & unknown"); // a ~= b
-    CHECK_EQ(toString(requireTypeAtPosition({5, 36})), "boolean?");           // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({5, 36})), "(boolean?) & unknown");           // a ~= b
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "(number | string)?"); // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "boolean?");           // a == b
+
+        CHECK_EQ(toString(requireTypeAtPosition({5, 33})), "(number | string)?"); // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({5, 36})), "boolean?");           // a ~= b
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "lvalue_is_equal_to_a_term")
@@ -402,8 +485,16 @@ TEST_CASE_FIXTURE(Fixture, "lvalue_is_equal_to_a_term")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "(number | string)?"); // a == 1
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "(number | string)?"); // a ~= 1
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "((number | string)?) & number");  // a == 1
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "((number | string)?) & unknown"); // a ~= 1
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "(number | string)?"); // a == 1;
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "(number | string)?"); // a ~= 1
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "term_is_equal_to_an_lvalue")
@@ -420,8 +511,16 @@ TEST_CASE_FIXTURE(Fixture, "term_is_equal_to_an_lvalue")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 28})), R"("hello")");         // a == "hello"
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "(number | string)?"); // a ~= "hello"
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), R"("hello" & ((number | string)?))");  // a == "hello"
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), R"(((number | string)?) & ~"hello")"); // a ~= "hello"
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), R"("hello")");            // a == "hello"
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), R"((number | string)?)"); // a ~= "hello"
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "lvalue_is_not_nil")
@@ -438,8 +537,16 @@ TEST_CASE_FIXTURE(Fixture, "lvalue_is_not_nil")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "number | string");    // a ~= nil
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "(number | string)?"); // a == nil
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "((number | string)?) & ~nil"); // a ~= nil
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "((number | string)?) & nil");  // a == nil
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 28})), "number | string");    // a ~= nil
+        CHECK_EQ(toString(requireTypeAtPosition({5, 28})), "(number | string)?"); // a == nil
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "free_type_is_equal_to_an_lvalue")
@@ -454,8 +561,17 @@ TEST_CASE_FIXTURE(Fixture, "free_type_is_equal_to_an_lvalue")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "a");       // a == b
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "string?"); // a == b
+    {
+        ToStringOptions opts;
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33}), opts), "(string?) & a"); // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36}), opts), "(string?) & a"); // a == b
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "a");       // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "string?"); // a == b
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "unknown_lvalue_is_not_synonymous_with_other_on_not_equal")
@@ -470,8 +586,16 @@ TEST_CASE_FIXTURE(Fixture, "unknown_lvalue_is_not_synonymous_with_other_on_not_e
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "any");              // a ~= b
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "{| x: number |}?"); // a ~= b
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "any & unknown");                // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "({| x: number |}?) & unknown"); // a ~= b
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({3, 33})), "any");              // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({3, 36})), "{| x: number |}?"); // a ~= b
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "string_not_equal_to_string_or_nil")
@@ -490,11 +614,22 @@ TEST_CASE_FIXTURE(Fixture, "string_not_equal_to_string_or_nil")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(toString(requireTypeAtPosition({6, 29})), "string");  // a ~= b
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ(toString(requireTypeAtPosition({6, 32})), "string?"); // a ~= b
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({6, 29})), "string & unknown");    // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({6, 32})), "(string?) & unknown"); // a ~= b
 
-    CHECK_EQ(toString(requireTypeAtPosition({8, 29})), "string");  // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({8, 29})), "(string?) & string"); // a == b
-    CHECK_EQ(toString(requireTypeAtPosition({8, 32})), "string?"); // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({8, 32})), "(string?) & string"); // a == b
+    }
+    else
+    {
+        CHECK_EQ(toString(requireTypeAtPosition({6, 29})), "string");  // a ~= b
+        CHECK_EQ(toString(requireTypeAtPosition({6, 32})), "string?"); // a ~= b
+
+        CHECK_EQ(toString(requireTypeAtPosition({8, 29})), "string");  // a == b
+        CHECK_EQ(toString(requireTypeAtPosition({8, 32})), "string?"); // a == b
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "narrow_property_of_a_bounded_variable")
@@ -525,10 +660,7 @@ TEST_CASE_FIXTURE(Fixture, "type_narrow_to_vector")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireTypeAtPosition({3, 28})));
-        CHECK_EQ("*error-type*", toString(requireTypeAtPosition({3, 28})));
-    else
-        CHECK_EQ("<error-type>", toString(requireTypeAtPosition({3, 28})));
 }
 
 TEST_CASE_FIXTURE(Fixture, "nonoptional_type_can_narrow_to_nil_if_sense_is_true")
@@ -715,8 +847,16 @@ TEST_CASE_FIXTURE(Fixture, "not_a_and_not_b")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("nil", toString(requireTypeAtPosition({3, 28})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("nil", toString(requireTypeAtPosition({4, 28})));
+    {
+        CHECK_EQ("(number?) & ~~(false?)", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("(number?) & ~~(false?)", toString(requireTypeAtPosition({4, 28})));
+    }
+    else
+    {
+        CHECK_EQ("nil", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("nil", toString(requireTypeAtPosition({4, 28})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "not_a_and_not_b2")
@@ -732,8 +872,16 @@ TEST_CASE_FIXTURE(Fixture, "not_a_and_not_b2")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("nil", toString(requireTypeAtPosition({3, 28})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("nil", toString(requireTypeAtPosition({4, 28})));
+    {
+        CHECK_EQ("(number?) & ~~(false?)", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("(number?) & ~~(false?)", toString(requireTypeAtPosition({4, 28})));
+    }
+    else
+    {
+        CHECK_EQ("nil", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("nil", toString(requireTypeAtPosition({4, 28})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "either_number_or_string")

tests/TypeInfer.singletons.test.cpp

@@ -79,6 +79,16 @@ TEST_CASE_FIXTURE(Fixture, "string_singleton_subtype")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "string_singleton_subtype_multi_assignment")
+{
+    CheckResult result = check(R"(
+        local a: "foo" = "foo"
+        local b: string, c: number = a, 10
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_CASE_FIXTURE(Fixture, "function_call_with_singletons")
 {
     CheckResult result = check(R"(

tests/TypeInfer.tables.test.cpp

@@ -17,7 +17,6 @@ using namespace Luau;
 LUAU_FASTFLAG(LuauLowerBoundsCalculation);
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
 
 TEST_SUITE_BEGIN("TableTests");
 
@@ -3272,11 +3271,12 @@ TEST_CASE_FIXTURE(Fixture, "invariant_table_properties_means_instantiating_table
 
     LUAU_REQUIRE_NO_ERRORS(result);
     // TODO: test behavior is wrong until we can re-enable the covariant requirement for instantiation in subtyping
-//     LUAU_REQUIRE_ERRORS(result);
+    //     LUAU_REQUIRE_ERRORS(result);
-//     CHECK_EQ(toString(result.errors[0]), R"(Type 't' could not be converted into '{| m: (number) -> number |}'
+    //     CHECK_EQ(toString(result.errors[0]), R"(Type 't' could not be converted into '{| m: (number) -> number |}'
-// caused by:
+    // caused by:
-//   Property 'm' is not compatible. Type '<a>(a) -> a' could not be converted into '(number) -> number'; different number of generic type parameters)");
+    //   Property 'm' is not compatible. Type '<a>(a) -> a' could not be converted into '(number) -> number'; different number of generic type
-//     // this error message is not great since the underlying issue is that the context is invariant,
+    //   parameters)");
+    //     // this error message is not great since the underlying issue is that the context is invariant,
     // and `(number) -> number` cannot be a subtype of `<a>(a) -> a`.
 }
 
@@ -3335,10 +3335,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "tables_should_be_fully_populated")
 
     ToStringOptions opts;
     opts.exhaustive = true;
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("{ x: *error-type*, y: number }", toString(requireType("t"), opts));
-        CHECK_EQ("{ x: *error-type*, y: number }", toString(requireType("t"), opts));
-    else
-        CHECK_EQ("{ x: <error-type>, y: number }", toString(requireType("t"), opts));
 }
 
 TEST_SUITE_END();

tests/TypeInfer.test.cpp

@@ -17,7 +17,6 @@
 LUAU_FASTFLAG(LuauFixLocationSpanTableIndexExpr);
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 LUAU_FASTFLAG(LuauInstantiateInSubtyping);
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked);
 
 using namespace Luau;
 
@@ -238,20 +237,10 @@ TEST_CASE_FIXTURE(Fixture, "type_errors_infer_types")
     // TODO: Should we assert anything about these tests when DCR is being used?
     if (!FFlag::DebugLuauDeferredConstraintResolution)
     {
-        if (FFlag::LuauSpecialTypesAsterisked)
+        CHECK_EQ("*error-type*", toString(requireType("c")));
-        {
+        CHECK_EQ("*error-type*", toString(requireType("d")));
-            CHECK_EQ("*error-type*", toString(requireType("c")));
+        CHECK_EQ("*error-type*", toString(requireType("e")));
-            CHECK_EQ("*error-type*", toString(requireType("d")));
+        CHECK_EQ("*error-type*", toString(requireType("f")));
-            CHECK_EQ("*error-type*", toString(requireType("e")));
-            CHECK_EQ("*error-type*", toString(requireType("f")));
-        }
-        else
-        {
-            CHECK_EQ("<error-type>", toString(requireType("c")));
-            CHECK_EQ("<error-type>", toString(requireType("d")));
-            CHECK_EQ("<error-type>", toString(requireType("e")));
-            CHECK_EQ("<error-type>", toString(requireType("f")));
-        }
     }
 }
 
@@ -662,10 +651,7 @@ TEST_CASE_FIXTURE(Fixture, "no_stack_overflow_from_isoptional")
     std::optional<TypeFun> t0 = getMainModule()->getModuleScope()->lookupType("t0");
     REQUIRE(t0);
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(t0->type));
-        CHECK_EQ("*error-type*", toString(t0->type));
-    else
-        CHECK_EQ("<error-type>", toString(t0->type));
 
     auto it = std::find_if(result.errors.begin(), result.errors.end(), [](TypeError& err) {
         return get<OccursCheckFailed>(err);

tests/TypeInfer.tryUnify.test.cpp

@@ -9,8 +9,6 @@
 
 using namespace Luau;
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
-
 struct TryUnifyFixture : Fixture
 {
     TypeArena arena;
@@ -124,10 +122,7 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "members_of_failed_typepack_unification_are_u
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
     CHECK_EQ("a", toString(requireType("a")));
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("b")));
-        CHECK_EQ("*error-type*", toString(requireType("b")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("b")));
 }
 
 TEST_CASE_FIXTURE(TryUnifyFixture, "result_of_failed_typepack_unification_is_constrained")
@@ -142,10 +137,7 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "result_of_failed_typepack_unification_is_con
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
     CHECK_EQ("a", toString(requireType("a")));
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("b")));
-        CHECK_EQ("*error-type*", toString(requireType("b")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("b")));
     CHECK_EQ("number", toString(requireType("c")));
 }
 

tests/TypeInfer.unionTypes.test.cpp

@@ -6,8 +6,6 @@
 
 #include "doctest.h"
 
-LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
-
 using namespace Luau;
 
 TEST_SUITE_BEGIN("UnionTypes");
@@ -199,10 +197,7 @@ TEST_CASE_FIXTURE(Fixture, "index_on_a_union_type_with_missing_property")
     CHECK_EQ(mup->missing[0], *bTy);
     CHECK_EQ(mup->key, "x");
 
-    if (FFlag::LuauSpecialTypesAsterisked)
+    CHECK_EQ("*error-type*", toString(requireType("r")));
-        CHECK_EQ("*error-type*", toString(requireType("r")));
-    else
-        CHECK_EQ("<error-type>", toString(requireType("r")));
 }
 
 TEST_CASE_FIXTURE(Fixture, "index_on_a_union_type_with_one_property_of_type_any")

tests/Variant.test.cpp

@@ -217,4 +217,35 @@ TEST_CASE("Visit")
     CHECK(r3 == "1231147");
 }
 
+struct MoveOnly
+{
+    MoveOnly() = default;
+
+    MoveOnly(const MoveOnly&) = delete;
+    MoveOnly& operator=(const MoveOnly&) = delete;
+
+    MoveOnly(MoveOnly&&) = default;
+    MoveOnly& operator=(MoveOnly&&) = default;
+};
+
+TEST_CASE("Move")
+{
+    Variant<MoveOnly> v1 = MoveOnly{};
+    Variant<MoveOnly> v2 = std::move(v1);
+}
+
+TEST_CASE("MoveWithCopyableAlternative")
+{
+    Variant<std::string, MoveOnly> v1 = std::string{"Hello, world! I am longer than a normal hello world string to avoid SSO."};
+    Variant<std::string, MoveOnly> v2 = std::move(v1);
+
+    std::string* s1 = get_if<std::string>(&v1);
+    REQUIRE(s1);
+    CHECK(*s1 == "");
+
+    std::string* s2 = get_if<std::string>(&v2);
+    REQUIRE(s2);
+    CHECK(*s2 == "Hello, world! I am longer than a normal hello world string to avoid SSO.");
+}
+
 TEST_SUITE_END();

tools/faillist.txt

@@ -10,7 +10,9 @@ AnnotationTests.too_many_type_params
 AnnotationTests.two_type_params
 AnnotationTests.unknown_type_reference_generates_error
 AstQuery.last_argument_function_call_type
+AstQuery::getDocumentationSymbolAtPosition.overloaded_class_method
 AstQuery::getDocumentationSymbolAtPosition.overloaded_fn
+AstQuery::getDocumentationSymbolAtPosition.table_overloaded_function_prop
 AutocompleteTest.autocomplete_first_function_arg_expected_type
 AutocompleteTest.autocomplete_interpolated_string
 AutocompleteTest.autocomplete_oop_implicit_self
@@ -106,17 +108,14 @@ GenericsTests.correctly_instantiate_polymorphic_member_functions
 GenericsTests.do_not_infer_generic_functions
 GenericsTests.duplicate_generic_type_packs
 GenericsTests.duplicate_generic_types
-GenericsTests.factories_of_generics
 GenericsTests.generic_argument_count_too_few
 GenericsTests.generic_argument_count_too_many
 GenericsTests.generic_factories
-GenericsTests.generic_functions_in_types
 GenericsTests.generic_functions_should_be_memory_safe
 GenericsTests.generic_table_method
 GenericsTests.generic_type_pack_parentheses
 GenericsTests.generic_type_pack_unification1
 GenericsTests.generic_type_pack_unification2
-GenericsTests.generic_type_pack_unification3
 GenericsTests.higher_rank_polymorphism_should_not_accept_instantiated_arguments
 GenericsTests.infer_generic_function_function_argument
 GenericsTests.infer_generic_function_function_argument_overloaded
@@ -172,7 +171,6 @@ ProvisionalTests.table_insert_with_a_singleton_argument
 ProvisionalTests.typeguard_inference_incomplete
 ProvisionalTests.weirditer_should_not_loop_forever
 ProvisionalTests.while_body_are_also_refined
-RefinementTest.and_constraint
 RefinementTest.apply_refinements_on_astexprindexexpr_whose_subscript_expr_is_constant_string
 RefinementTest.assert_a_to_be_truthy_then_assert_a_to_be_number
 RefinementTest.assert_non_binary_expressions_actually_resolve_constraints
@@ -187,28 +185,17 @@ RefinementTest.either_number_or_string
 RefinementTest.eliminate_subclasses_of_instance
 RefinementTest.falsiness_of_TruthyPredicate_narrows_into_nil
 RefinementTest.index_on_a_refined_property
-RefinementTest.invert_is_truthy_constraint
 RefinementTest.invert_is_truthy_constraint_ifelse_expression
-RefinementTest.is_truthy_constraint
 RefinementTest.is_truthy_constraint_ifelse_expression
-RefinementTest.lvalue_is_not_nil
 RefinementTest.merge_should_be_fully_agnostic_of_hashmap_ordering
-RefinementTest.narrow_boolean_to_true_or_false
 RefinementTest.narrow_property_of_a_bounded_variable
 RefinementTest.narrow_this_large_union
 RefinementTest.nonoptional_type_can_narrow_to_nil_if_sense_is_true
-RefinementTest.not_a_and_not_b
-RefinementTest.not_a_and_not_b2
-RefinementTest.not_and_constraint
 RefinementTest.not_t_or_some_prop_of_t
-RefinementTest.or_predicate_with_truthy_predicates
-RefinementTest.parenthesized_expressions_are_followed_through
 RefinementTest.refine_a_property_not_to_be_nil_through_an_intersection_table
 RefinementTest.refine_the_correct_types_opposite_of_when_a_is_not_number_or_string
 RefinementTest.refine_unknowns
-RefinementTest.term_is_equal_to_an_lvalue
 RefinementTest.truthy_constraint_on_properties
-RefinementTest.type_assertion_expr_carry_its_constraints
 RefinementTest.type_comparison_ifelse_expression
 RefinementTest.type_guard_can_filter_for_intersection_of_tables
 RefinementTest.type_guard_can_filter_for_overloaded_function
@@ -271,6 +258,7 @@ TableTests.infer_indexer_from_value_property_in_literal
 TableTests.inferred_return_type_of_free_table
 TableTests.inferring_crazy_table_should_also_be_quick
 TableTests.instantiate_table_cloning_3
+TableTests.invariant_table_properties_means_instantiating_tables_in_assignment_is_unsound
 TableTests.invariant_table_properties_means_instantiating_tables_in_call_is_unsound
 TableTests.leaking_bad_metatable_errors
 TableTests.less_exponential_blowup_please
@@ -315,7 +303,6 @@ TableTests.table_subtyping_with_missing_props_dont_report_multiple_errors
 TableTests.tables_get_names_from_their_locals
 TableTests.tc_member_function
 TableTests.tc_member_function_2
-TableTests.top_table_type
 TableTests.type_mismatch_on_massive_table_is_cut_short
 TableTests.unification_of_unions_in_a_self_referential_type
 TableTests.unifying_tables_shouldnt_uaf2
@@ -417,12 +404,12 @@ TypeInferFunctions.too_few_arguments_variadic
 TypeInferFunctions.too_few_arguments_variadic_generic
 TypeInferFunctions.too_few_arguments_variadic_generic2
 TypeInferFunctions.too_many_arguments
+TypeInferFunctions.too_many_arguments_error_location
 TypeInferFunctions.too_many_return_values
 TypeInferFunctions.too_many_return_values_in_parentheses
 TypeInferFunctions.too_many_return_values_no_function
 TypeInferFunctions.vararg_function_is_quantified
 TypeInferLoops.for_in_loop_error_on_factory_not_returning_the_right_amount_of_values
-TypeInferLoops.for_in_loop_with_custom_iterator
 TypeInferLoops.for_in_loop_with_next
 TypeInferLoops.for_in_with_generic_next
 TypeInferLoops.for_in_with_just_one_iterator_is_ok
@@ -430,7 +417,6 @@ TypeInferLoops.loop_iter_no_indexer_nonstrict
 TypeInferLoops.loop_iter_trailing_nil
 TypeInferLoops.unreachable_code_after_infinite_loop
 TypeInferLoops.varlist_declared_by_for_in_loop_should_be_free
-TypeInferModules.bound_free_table_export_is_ok
 TypeInferModules.custom_require_global
 TypeInferModules.do_not_modify_imported_types
 TypeInferModules.module_type_conflict
@@ -443,6 +429,7 @@ TypeInferOOP.dont_suggest_using_colon_rather_than_dot_if_it_wont_help_2
 TypeInferOOP.dont_suggest_using_colon_rather_than_dot_if_not_defined_with_colon
 TypeInferOOP.inferring_hundreds_of_self_calls_should_not_suffocate_memory
 TypeInferOOP.methods_are_topologically_sorted
+TypeInferOOP.object_constructor_can_refer_to_method_of_self
 TypeInferOperators.and_or_ternary
 TypeInferOperators.CallAndOrOfFunctions
 TypeInferOperators.cannot_compare_tables_that_do_not_have_the_same_metatable

tools/lvmexecute_split.py

@@ -32,6 +32,9 @@ source = """// This file is part of the Luau programming language and is license
 """
 
 function = ""
+signature = ""
+
+includeInsts = ["LOP_NEWCLOSURE", "LOP_NAMECALL", "LOP_FORGPREP", "LOP_GETVARARGS", "LOP_DUPCLOSURE", "LOP_PREPVARARGS", "LOP_COVERAGE", "LOP_BREAK", "LOP_GETGLOBAL", "LOP_SETGLOBAL", "LOP_GETTABLEKS", "LOP_SETTABLEKS"]
 
 state = 0
 
@@ -44,7 +47,6 @@ for line in input:
         if match:
             inst = match[1]
             signature = "const Instruction* execute_" + inst + "(lua_State* L, const Instruction* pc, StkId base, TValue* k)"
-            header += signature + ";\n"
             function = signature + "\n"
             function += "{\n"
             function += "    [[maybe_unused]] Closure* cl = clvalue(L->ci->func);\n"
@@ -84,7 +86,10 @@ for line in input:
                 function = function[:-len(finalline)]
                 function += "    return pc;\n}\n"
 
-            source += function + "\n"
+            if inst in includeInsts:
+                header += signature + ";\n"
+                source += function + "\n"
+
             state = 0
 
     # skip LUA_CUSTOM_EXECUTION code blocks

tools/stack-usage-reporter.py

@@ -0,0 +1,173 @@
+#!/usr/bin/python
+# This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+# The purpose of this script is to analyze disassembly generated by objdump or
+# dumpbin to print (or to compare) the stack usage of functions/methods.
+# This is a quickly written script, so it is quite possible it may not handle
+# all code properly.
+#
+# The script expects the user to create a text assembly dump to be passed to
+# the script.
+#
+# objdump Example
+#   objdump --demangle --disassemble objfile.o > objfile.s
+#
+# dumpbin Example
+#   dumpbin /disasm objfile.obj > objfile.s
+#
+# If the script is passed a single file, then all stack size information that
+# is found it printed.  If two files are passed, then the script compares the
+# stack usage of the two files (useful for A/B comparisons).
+# Currently more than two input files are not supported. (But adding support shouldn't
+# be very difficult.)
+#
+# Note: The script only handles x64 disassembly.  Supporting x86 is likely
+# trivial, but ARM support could be difficult.
+# Thus far the script has been tested with MSVC on Win64 and clang on OSX.
+
+import argparse
+import re
+
+blank_re = re.compile('\s*')
+
+class LineReader:
+    def __init__(self, lines):
+        self.lines = list(reversed(lines))
+    def get_line(self):
+        return self.lines.pop(-1)
+    def peek_line(self):
+        return self.lines[-1]
+    def consume_blank_lines(self):
+        while blank_re.fullmatch(self.peek_line()):
+            self.get_line()
+    def is_empty(self):
+        return len(self.lines) == 0
+
+def parse_objdump_assembly(in_file):
+    results = {}
+    text_section_re = re.compile('Disassembly of section __TEXT,__text:\s*')
+    symbol_re = re.compile('[^<]*<(.*)>:\s*')
+    stack_alloc = re.compile('.*subq\s*\$(\d*), %rsp\s*')
+
+    lr = LineReader(in_file.readlines())
+
+    def find_stack_alloc_size():
+        while True:
+            if lr.is_empty():
+                return None
+            if blank_re.fullmatch(lr.peek_line()):
+                return None
+
+            line = lr.get_line()
+            mo = stack_alloc.fullmatch(line)
+            if mo:
+                lr.consume_blank_lines()
+                return int(mo.group(1))
+
+    # Find beginning of disassembly
+    while not text_section_re.fullmatch(lr.get_line()):
+        pass
+
+    # Scan for symbols
+    while not lr.is_empty():
+        lr.consume_blank_lines()
+        if lr.is_empty():
+            break
+        line = lr.get_line()
+        mo = symbol_re.fullmatch(line)
+        # Found a symbol
+        if mo:
+            symbol = mo.group(1)
+            stack_size = find_stack_alloc_size()
+            if stack_size != None:
+                results[symbol] = stack_size
+
+    return results
+
+def parse_dumpbin_assembly(in_file):
+    results = {}
+
+    file_type_re = re.compile('File Type: COFF OBJECT\s*')
+    symbol_re = re.compile('[^(]*\((.*)\):\s*')
+    summary_re = re.compile('\s*Summary\s*')
+    stack_alloc = re.compile('.*sub\s*rsp,([A-Z0-9]*)h\s*')
+
+    lr = LineReader(in_file.readlines())
+
+    def find_stack_alloc_size():
+        while True:
+            if lr.is_empty():
+                return None
+            if blank_re.fullmatch(lr.peek_line()):
+                return None
+
+            line = lr.get_line()
+            mo = stack_alloc.fullmatch(line)
+            if mo:
+                lr.consume_blank_lines()
+                return int(mo.group(1), 16) # return value in decimal
+
+    # Find beginning of disassembly
+    while not file_type_re.fullmatch(lr.get_line()):
+        pass
+
+    # Scan for symbols
+    while not lr.is_empty():
+        lr.consume_blank_lines()
+        if lr.is_empty():
+            break
+        line = lr.get_line()
+        if summary_re.fullmatch(line):
+            break
+        mo = symbol_re.fullmatch(line)
+        # Found a symbol
+        if mo:
+            symbol = mo.group(1)
+            stack_size = find_stack_alloc_size()
+            if stack_size != None:
+                results[symbol] = stack_size
+    return results
+
+def main():
+    parser = argparse.ArgumentParser(description='Tool used for reporting or comparing the stack usage of functions/methods')
+    parser.add_argument('--format', choices=['dumpbin', 'objdump'], required=True, help='Specifies the program used to generate the input files')
+    parser.add_argument('--input', action='append', required=True, help='Input assembly file.  This option may be specified multiple times.')
+    parser.add_argument('--md-output', action='store_true', help='Show table output in markdown format')
+    parser.add_argument('--only-diffs', action='store_true', help='Only show stack info when it differs between the input files')
+    args = parser.parse_args()
+
+    parsers = {'dumpbin': parse_dumpbin_assembly, 'objdump' : parse_objdump_assembly}
+    parse_func = parsers[args.format]
+
+    input_results = []
+    for input_name in args.input:
+        with open(input_name) as in_file:
+            results = parse_func(in_file)
+            input_results.append(results)
+
+    if len(input_results) == 1:
+        # Print out the results sorted by size
+        size_sorted = sorted([(size, symbol) for symbol, size in results.items()], reverse=True)
+        print(input_name)
+        for size, symbol in size_sorted:
+            print(f'{size:10}\t{symbol}')
+        print()
+    elif len(input_results) == 2:
+        common_symbols = set(input_results[0].keys()).intersection(set(input_results[1].keys()))
+        print(f'Found {len(common_symbols)} common symbols')
+        stack_sizes = sorted([(input_results[0][sym], input_results[1][sym], sym) for sym in common_symbols], reverse=True)
+        if args.md_output:
+            print('Before | After | Symbol')
+            print('-- | -- | --')
+        for size0, size1, symbol in stack_sizes:
+            if args.only_diffs and size0 == size1:
+                continue
+            if args.md_output:
+                print(f'{size0} | {size1} | {symbol}')
+            else:
+                print(f'{size0:10}\t{size1:10}\t{symbol}')
+    else:
+        print("TODO support more than 2 inputs")
+
+if __name__ == '__main__':
+    main()