Sync to upstream/release/550 (#723)

* Support `["prop"]` syntax on class definitions in definition files.
(#704)
* Improve type checking performance for complex overloaded functions
* Fix rare cases of incorrect stack traces for out of memory errors at
runtime

Analysis/include/Luau/Clone.h

@@ -1,6 +1,7 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
+#include <Luau/NotNull.h>
 #include "Luau/TypeArena.h"
 #include "Luau/TypeVar.h"
 
@@ -26,5 +27,6 @@ TypeId clone(TypeId tp, TypeArena& dest, CloneState& cloneState);
 TypeFun clone(const TypeFun& typeFun, TypeArena& dest, CloneState& cloneState);
 
 TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool alwaysClone = false);
+TypeId shallowClone(TypeId ty, NotNull<TypeArena> dest);
 
 } // namespace Luau

Analysis/include/Luau/Constraint.h

@@ -2,9 +2,10 @@
 #pragma once
 
 #include "Luau/Ast.h" // Used for some of the enumerations
+#include "Luau/Def.h"
 #include "Luau/NotNull.h"
-#include "Luau/Variant.h"
 #include "Luau/TypeVar.h"
+#include "Luau/Variant.h"
 
 #include <string>
 #include <memory>
@@ -131,9 +132,15 @@ struct HasPropConstraint
     std::string prop;
 };
 
-using ConstraintV =
+struct RefinementConstraint
-    Variant<SubtypeConstraint, PackSubtypeConstraint, GeneralizationConstraint, InstantiationConstraint, UnaryConstraint, BinaryConstraint,
+{
-        IterableConstraint, NameConstraint, TypeAliasExpansionConstraint, FunctionCallConstraint, PrimitiveTypeConstraint, HasPropConstraint>;
+    DefId def;
+    TypeId discriminantType;
+};
+
+using ConstraintV = Variant<SubtypeConstraint, PackSubtypeConstraint, GeneralizationConstraint, InstantiationConstraint, UnaryConstraint,
+    BinaryConstraint, IterableConstraint, NameConstraint, TypeAliasExpansionConstraint, FunctionCallConstraint, PrimitiveTypeConstraint,
+    HasPropConstraint, RefinementConstraint>;
 
 struct Constraint
 {
@@ -143,7 +150,7 @@ struct Constraint
     Constraint& operator=(const Constraint&) = delete;
 
     NotNull<Scope> scope;
-    Location location;
+    Location location; // TODO: Extract this out into only the constraints that needs a location. Not all constraints needs locations.
     ConstraintV c;
 
     std::vector<NotNull<Constraint>> dependencies;

Analysis/include/Luau/ConstraintGraphBuilder.h

@@ -1,13 +1,9 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-
 #pragma once
 
-#include <memory>
-#include <vector>
-#include <unordered_map>
-
 #include "Luau/Ast.h"
 #include "Luau/Constraint.h"
+#include "Luau/DataFlowGraphBuilder.h"
 #include "Luau/Module.h"
 #include "Luau/ModuleResolver.h"
 #include "Luau/NotNull.h"
@@ -15,6 +11,10 @@
 #include "Luau/TypeVar.h"
 #include "Luau/Variant.h"
 
+#include <memory>
+#include <vector>
+#include <unordered_map>
+
 namespace Luau
 {
 
@@ -48,6 +48,7 @@ struct ConstraintGraphBuilder
     DenseHashMap<const AstTypePack*, TypePackId> astResolvedTypePacks{nullptr};
     // Defining scopes for AST nodes.
     DenseHashMap<const AstStatTypeAlias*, ScopePtr> astTypeAliasDefiningScopes{nullptr};
+    NotNull<const DataFlowGraph> dfg;
 
     int recursionCount = 0;
 
@@ -63,7 +64,8 @@ struct ConstraintGraphBuilder
     DcrLogger* logger;
 
     ConstraintGraphBuilder(const ModuleName& moduleName, ModulePtr module, TypeArena* arena, NotNull<ModuleResolver> moduleResolver,
-        NotNull<SingletonTypes> singletonTypes, NotNull<InternalErrorReporter> ice, const ScopePtr& globalScope, DcrLogger* logger);
+        NotNull<SingletonTypes> singletonTypes, NotNull<InternalErrorReporter> ice, const ScopePtr& globalScope, DcrLogger* logger,
+        NotNull<DataFlowGraph> dfg);
 
     /**
      * Fabricates a new free type belonging to a given scope.
@@ -88,15 +90,17 @@ struct ConstraintGraphBuilder
      * Adds a new constraint with no dependencies to a given scope.
      * @param scope the scope to add the constraint to.
      * @param cv the constraint variant to add.
+     * @return the pointer to the inserted constraint
      */
-    void addConstraint(const ScopePtr& scope, const Location& location, ConstraintV cv);
+    NotNull<Constraint> addConstraint(const ScopePtr& scope, const Location& location, ConstraintV cv);
 
     /**
      * Adds a constraint to a given scope.
      * @param scope the scope to add the constraint to. Must not be null.
      * @param c the constraint to add.
+     * @return the pointer to the inserted constraint
      */
-    void addConstraint(const ScopePtr& scope, std::unique_ptr<Constraint> c);
+    NotNull<Constraint> addConstraint(const ScopePtr& scope, std::unique_ptr<Constraint> c);
 
     /**
      * The entry point to the ConstraintGraphBuilder. This will construct a set
@@ -139,13 +143,20 @@ struct ConstraintGraphBuilder
      */
     TypeId check(const ScopePtr& scope, AstExpr* expr, std::optional<TypeId> expectedType = {});
 
-    TypeId check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
+    TypeId check(const ScopePtr& scope, AstExprLocal* local);
+    TypeId check(const ScopePtr& scope, AstExprGlobal* global);
     TypeId check(const ScopePtr& scope, AstExprIndexName* indexName);
     TypeId check(const ScopePtr& scope, AstExprIndexExpr* indexExpr);
     TypeId check(const ScopePtr& scope, AstExprUnary* unary);
-    TypeId check(const ScopePtr& scope, AstExprBinary* binary);
+    TypeId check_(const ScopePtr& scope, AstExprUnary* unary);
+    TypeId check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType);
     TypeId check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType);
     TypeId check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert);
+    TypeId check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType);
+
+    TypePackId checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs);
+
+    TypeId checkLValue(const ScopePtr& scope, AstExpr* expr);
 
     struct FunctionSignature
     {

Analysis/include/Luau/ConstraintSolver.h

@@ -110,6 +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);
 
     // for a, ... in some_table do
     // also handles __iter metamethod
@@ -215,6 +216,8 @@ private:
     TypeId errorRecoveryType() const;
     TypePackId errorRecoveryTypePack() const;
 
+    TypeId unionOfTypes(TypeId a, TypeId b, NotNull<Scope> scope, bool unifyFreeTypes);
+
     ToStringOptions opts;
 };
 

Analysis/include/Luau/DataFlowGraphBuilder.h

@@ -0,0 +1,115 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+// Do not include LValue. It should never be used here.
+#include "Luau/Ast.h"
+#include "Luau/DenseHash.h"
+#include "Luau/Def.h"
+#include "Luau/Symbol.h"
+
+#include <unordered_map>
+
+namespace Luau
+{
+
+struct DataFlowGraph
+{
+    DataFlowGraph(DataFlowGraph&&) = default;
+    DataFlowGraph& operator=(DataFlowGraph&&) = default;
+
+    // TODO: AstExprLocal, AstExprGlobal, and AstLocal* are guaranteed never to return nullopt.
+    // We leave them to return an optional as we build it out, but the end state is for them to return a non-optional DefId.
+    std::optional<DefId> getDef(const AstExpr* expr) const;
+    std::optional<DefId> getDef(const AstLocal* local) const;
+
+    /// Retrieve the Def that corresponds to the given Symbol.
+    ///
+    /// We do not perform dataflow analysis on globals, so this function always
+    /// yields nullopt when passed a global Symbol.
+    std::optional<DefId> getDef(const Symbol& symbol) const;
+
+private:
+    DataFlowGraph() = default;
+
+    DataFlowGraph(const DataFlowGraph&) = delete;
+    DataFlowGraph& operator=(const DataFlowGraph&) = delete;
+
+    DefArena arena;
+    DenseHashMap<const AstExpr*, const Def*> astDefs{nullptr};
+    DenseHashMap<const AstLocal*, const Def*> localDefs{nullptr};
+
+    friend struct DataFlowGraphBuilder;
+};
+
+struct DfgScope
+{
+    DfgScope* parent;
+    DenseHashMap<Symbol, const Def*> bindings{Symbol{}};
+};
+
+struct ExpressionFlowGraph
+{
+    std::optional<DefId> def;
+};
+
+// Currently unsound. We do not presently track the control flow of the program.
+// Additionally, we do not presently track assignments.
+struct DataFlowGraphBuilder
+{
+    static DataFlowGraph build(AstStatBlock* root, NotNull<struct InternalErrorReporter> handle);
+
+private:
+    DataFlowGraphBuilder() = default;
+
+    DataFlowGraphBuilder(const DataFlowGraphBuilder&) = delete;
+    DataFlowGraphBuilder& operator=(const DataFlowGraphBuilder&) = delete;
+
+    DataFlowGraph graph;
+    NotNull<DefArena> arena{&graph.arena};
+    struct InternalErrorReporter* handle;
+    std::vector<std::unique_ptr<DfgScope>> scopes;
+
+    DfgScope* childScope(DfgScope* scope);
+
+    std::optional<DefId> use(DfgScope* scope, Symbol symbol, AstExpr* e);
+
+    void visit(DfgScope* scope, AstStatBlock* b);
+    void visitBlockWithoutChildScope(DfgScope* scope, AstStatBlock* b);
+
+    // TODO: visit type aliases
+    void visit(DfgScope* scope, AstStat* s);
+    void visit(DfgScope* scope, AstStatIf* i);
+    void visit(DfgScope* scope, AstStatWhile* w);
+    void visit(DfgScope* scope, AstStatRepeat* r);
+    void visit(DfgScope* scope, AstStatBreak* b);
+    void visit(DfgScope* scope, AstStatContinue* c);
+    void visit(DfgScope* scope, AstStatReturn* r);
+    void visit(DfgScope* scope, AstStatExpr* e);
+    void visit(DfgScope* scope, AstStatLocal* l);
+    void visit(DfgScope* scope, AstStatFor* f);
+    void visit(DfgScope* scope, AstStatForIn* f);
+    void visit(DfgScope* scope, AstStatAssign* a);
+    void visit(DfgScope* scope, AstStatCompoundAssign* c);
+    void visit(DfgScope* scope, AstStatFunction* f);
+    void visit(DfgScope* scope, AstStatLocalFunction* l);
+
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExpr* e);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprLocal* l);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprGlobal* g);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprCall* c);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprIndexName* i);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprIndexExpr* i);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprFunction* f);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprTable* t);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprUnary* u);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprBinary* b);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprTypeAssertion* t);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprIfElse* i);
+    ExpressionFlowGraph visitExpr(DfgScope* scope, AstExprInterpString* i);
+
+    // TODO: visitLValue
+    // TODO: visitTypes (because of typeof which has access to values namespace, needs unreachable scope)
+    // TODO: visitTypePacks (because of typeof which has access to values namespace, needs unreachable scope)
+};
+
+} // namespace Luau

Analysis/include/Luau/Def.h

@@ -0,0 +1,78 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/NotNull.h"
+#include "Luau/TypedAllocator.h"
+#include "Luau/Variant.h"
+
+namespace Luau
+{
+
+using Def = Variant<struct Undefined, struct Phi>;
+
+/**
+ * We statically approximate a value at runtime using a symbolic value, which we call a Def.
+ *
+ * DataFlowGraphBuilder will allocate these defs as a stand-in for some Luau values, and bind them to places that
+ * can hold a Luau value, and then observes how those defs will commute as it statically evaluate the program.
+ *
+ * It must also be noted that defs are a cyclic graph, so it is not safe to recursively traverse into it expecting it to terminate.
+ */
+using DefId = NotNull<const Def>;
+
+/**
+ * A "single-object" value.
+ *
+ * Leaky implementation note: sometimes "multiple-object" values, but none of which were interesting enough to warrant creating a phi node instead.
+ * That can happen because there's no point in creating a phi node that points to either resultant in `if math.random() > 0.5 then 5 else "hello"`.
+ * This might become of utmost importance if we wanted to do some backward reasoning, e.g. if `5` is taken, then `cond` must be `truthy`.
+ */
+struct Undefined
+{
+};
+
+/**
+ * A phi node is a union of defs.
+ *
+ * We need this because we're statically evaluating a program, and sometimes a place may be assigned with
+ * different defs, and when that happens, we need a special data type that merges in all the defs
+ * that will flow into that specific place. For example, consider this simple program:
+ *
+ * ```
+ * x-1
+ * if cond() then
+ *   x-2 = 5
+ * else
+ *   x-3 = "hello"
+ * end
+ * x-4 : {x-2, x-3}
+ * ```
+ *
+ * At x-4, we know for a fact statically that either `5` or `"hello"` can flow into the variable `x` after the branch, but
+ * we cannot make any definitive decisions about which one, so we just take in both.
+ */
+struct Phi
+{
+    std::vector<DefId> operands;
+};
+
+template<typename T>
+T* getMutable(DefId def)
+{
+    return get_if<T>(def.get());
+}
+
+template<typename T>
+const T* get(DefId def)
+{
+    return getMutable<T>(def);
+}
+
+struct DefArena
+{
+    TypedAllocator<Def> allocator;
+
+    DefId freshDef();
+};
+
+} // namespace Luau

Analysis/include/Luau/LValue.h

@@ -14,6 +14,8 @@ struct TypeVar;
 using TypeId = const TypeVar*;
 
 struct Field;
+
+// Deprecated. Do not use in new work.
 using LValue = Variant<Symbol, Field>;
 
 struct Field

Analysis/include/Luau/Metamethods.h

@@ -0,0 +1,32 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#pragma once
+
+#include "Luau/Ast.h"
+
+#include <unordered_map>
+
+namespace Luau
+{
+
+static const std::unordered_map<AstExprBinary::Op, const char*> kBinaryOpMetamethods{
+    {AstExprBinary::Op::CompareEq, "__eq"},
+    {AstExprBinary::Op::CompareNe, "__eq"},
+    {AstExprBinary::Op::CompareGe, "__lt"},
+    {AstExprBinary::Op::CompareGt, "__le"},
+    {AstExprBinary::Op::CompareLe, "__le"},
+    {AstExprBinary::Op::CompareLt, "__lt"},
+    {AstExprBinary::Op::Add, "__add"},
+    {AstExprBinary::Op::Sub, "__sub"},
+    {AstExprBinary::Op::Mul, "__mul"},
+    {AstExprBinary::Op::Div, "__div"},
+    {AstExprBinary::Op::Pow, "__pow"},
+    {AstExprBinary::Op::Mod, "__mod"},
+    {AstExprBinary::Op::Concat, "__concat"},
+};
+
+static const std::unordered_map<AstExprUnary::Op, const char*> kUnaryOpMetamethods{
+    {AstExprUnary::Op::Minus, "__unm"},
+    {AstExprUnary::Op::Len, "__len"},
+};
+
+} // namespace Luau

Analysis/include/Luau/Normalize.h

@@ -22,15 +22,6 @@ bool isSubtype(
 bool isSubtype(TypePackId subTy, TypePackId superTy, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice,
     bool anyIsTop = true);
 
-std::pair<TypeId, bool> normalize(
-    TypeId ty, NotNull<Scope> scope, TypeArena& arena, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-std::pair<TypeId, bool> normalize(TypeId ty, NotNull<Module> module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-std::pair<TypeId, bool> normalize(TypeId ty, const ModulePtr& module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-std::pair<TypePackId, bool> normalize(
-    TypePackId ty, NotNull<Scope> scope, TypeArena& arena, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-std::pair<TypePackId, bool> normalize(TypePackId ty, NotNull<Module> module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-std::pair<TypePackId, bool> normalize(TypePackId ty, const ModulePtr& module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice);
-
 class TypeIds
 {
 private:

Analysis/include/Luau/Scope.h

@@ -54,7 +54,9 @@ struct Scope
     DenseHashSet<Name> builtinTypeNames{""};
     void addBuiltinTypeBinding(const Name& name, const TypeFun& tyFun);
 
-    std::optional<TypeId> lookup(Symbol sym);
+    std::optional<TypeId> lookup(Symbol sym) const;
+    std::optional<TypeId> lookup(DefId def) const;
+    std::optional<std::pair<TypeId, Scope*>> lookupEx(Symbol sym);
 
     std::optional<TypeFun> lookupType(const Name& name);
     std::optional<TypeFun> lookupImportedType(const Name& moduleAlias, const Name& name);
@@ -66,6 +68,7 @@ struct Scope
     std::optional<Binding> linearSearchForBinding(const std::string& name, bool traverseScopeChain = true) const;
 
     RefinementMap refinements;
+    DenseHashMap<const Def*, TypeId> dcrRefinements{nullptr};
 
     // For mutually recursive type aliases, it's important that
     // they use the same types for the same names.

Analysis/include/Luau/Symbol.h

@@ -6,10 +6,11 @@
 
 #include <string>
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+
 namespace Luau
 {
 
-// TODO Rename this to Name once the old type alias is gone.
 struct Symbol
 {
     Symbol()
@@ -40,9 +41,12 @@ struct Symbol
     {
         if (local)
             return local == rhs.local;
-        if (global.value)
+        else if (global.value)
             return rhs.global.value && global == rhs.global.value; // Subtlety: AstName::operator==(const char*) uses strcmp, not pointer identity.
-        return false;
+        else if (FFlag::DebugLuauDeferredConstraintResolution)
+            return !rhs.local && !rhs.global.value; // Reflexivity: we already know `this` Symbol is empty, so check that rhs is.
+        else
+            return false;
     }
 
     bool operator!=(const Symbol& rhs) const
@@ -58,8 +62,8 @@ struct Symbol
             return global < rhs.global;
         else if (local)
             return true;
-        else
+
-            return false;
+        return false;
     }
 
     AstName astName() const

Analysis/include/Luau/TypeInfer.h

@@ -192,18 +192,12 @@ struct TypeChecker
     ErrorVec canUnify(TypeId subTy, TypeId superTy, const ScopePtr& scope, const Location& location);
     ErrorVec canUnify(TypePackId subTy, TypePackId superTy, const ScopePtr& scope, const Location& location);
 
-    void unifyLowerBound(TypePackId subTy, TypePackId superTy, TypeLevel demotedLevel, const ScopePtr& scope, const Location& location);
-
     std::optional<TypeId> findMetatableEntry(TypeId type, std::string entry, const Location& location, bool addErrors);
     std::optional<TypeId> findTablePropertyRespectingMeta(TypeId lhsType, Name name, const Location& location, bool addErrors);
 
     std::optional<TypeId> getIndexTypeFromType(const ScopePtr& scope, TypeId type, const Name& name, const Location& location, bool addErrors);
     std::optional<TypeId> getIndexTypeFromTypeImpl(const ScopePtr& scope, TypeId type, const Name& name, const Location& location, bool addErrors);
 
-    // Reduces the union to its simplest possible shape.
-    // (A | B) | B | C yields A | B | C
-    std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types);
-
     std::optional<TypeId> tryStripUnionFromNil(TypeId ty);
     TypeId stripFromNilAndReport(TypeId ty, const Location& location);
 

Analysis/include/Luau/TypeUtils.h

@@ -29,4 +29,23 @@ std::pair<size_t, std::optional<size_t>> getParameterExtents(const TxnLog* log,
 // various other things to get there.
 std::vector<TypeId> flatten(TypeArena& arena, NotNull<SingletonTypes> singletonTypes, TypePackId pack, size_t length);
 
+/**
+ * Reduces a union by decomposing to the any/error type if it appears in the
+ * type list, and by merging child unions. Also strips out duplicate (by pointer
+ * identity) types.
+ * @param types the input type list to reduce.
+ * @returns the reduced type list.
+*/
+std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types);
+
+/**
+ * Tries to remove nil from a union type, if there's another option. T | nil
+ * reduces to T, but nil itself does not reduce.
+ * @param singletonTypes the singleton types to use
+ * @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

@@ -2,22 +2,23 @@
 #pragma once
 
 #include "Luau/Ast.h"
+#include "Luau/Common.h"
 #include "Luau/DenseHash.h"
+#include "Luau/Def.h"
+#include "Luau/NotNull.h"
 #include "Luau/Predicate.h"
 #include "Luau/Unifiable.h"
 #include "Luau/Variant.h"
-#include "Luau/Common.h"
-#include "Luau/NotNull.h"
 
-#include <set>
-#include <string>
-#include <map>
-#include <unordered_set>
-#include <unordered_map>
-#include <vector>
 #include <deque>
+#include <map>
 #include <memory>
 #include <optional>
+#include <set>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
 
 LUAU_FASTINT(LuauTableTypeMaximumStringifierLength)
 LUAU_FASTINT(LuauTypeMaximumStringifierLength)
@@ -131,24 +132,6 @@ struct PrimitiveTypeVar
     }
 };
 
-struct ConstrainedTypeVar
-{
-    explicit ConstrainedTypeVar(TypeLevel level)
-        : level(level)
-    {
-    }
-
-    explicit ConstrainedTypeVar(TypeLevel level, const std::vector<TypeId>& parts)
-        : parts(parts)
-        , level(level)
-    {
-    }
-
-    std::vector<TypeId> parts;
-    TypeLevel level;
-    Scope* scope = nullptr;
-};
-
 // Singleton types https://github.com/Roblox/luau/blob/master/rfcs/syntax-singleton-types.md
 // Types for true and false
 struct BooleanSingleton
@@ -496,11 +479,13 @@ struct AnyTypeVar
 {
 };
 
+// T | U
 struct UnionTypeVar
 {
     std::vector<TypeId> options;
 };
 
+// T & U
 struct IntersectionTypeVar
 {
     std::vector<TypeId> parts;
@@ -519,12 +504,27 @@ 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
+struct NegationTypeVar
+{
+    TypeId ty;
+};
+
 using ErrorTypeVar = Unifiable::Error;
 
-using TypeVariant =
+using TypeVariant = Unifiable::Variant<TypeId, PrimitiveTypeVar, BlockedTypeVar, PendingExpansionTypeVar, SingletonTypeVar, FunctionTypeVar,
-    Unifiable::Variant<TypeId, PrimitiveTypeVar, ConstrainedTypeVar, BlockedTypeVar, PendingExpansionTypeVar, SingletonTypeVar, FunctionTypeVar,
+    TableTypeVar, MetatableTypeVar, ClassTypeVar, AnyTypeVar, UnionTypeVar, IntersectionTypeVar, LazyTypeVar, UnknownTypeVar, NeverTypeVar,
-        TableTypeVar, MetatableTypeVar, ClassTypeVar, AnyTypeVar, UnionTypeVar, IntersectionTypeVar, LazyTypeVar, UnknownTypeVar, NeverTypeVar>;
+    UseTypeVar, NegationTypeVar>;
-
 
 struct TypeVar final
 {
@@ -541,7 +541,6 @@ struct TypeVar final
     TypeVar(const TypeVariant& ty, bool persistent)
         : ty(ty)
         , persistent(persistent)
-        , normal(persistent) // We assume that all persistent types are irreducable.
     {
     }
 
@@ -549,7 +548,6 @@ struct TypeVar final
     void reassign(const TypeVar& rhs)
     {
         ty = rhs.ty;
-        normal = rhs.normal;
         documentationSymbol = rhs.documentationSymbol;
     }
 
@@ -560,10 +558,6 @@ struct TypeVar final
     // Persistent TypeVars do not get cloned.
     bool persistent = false;
 
-    // Normalization sets this for types that are fully normalized.
-    // This implies that they are transitively immutable.
-    bool normal = false;
-
     std::optional<std::string> documentationSymbol;
 
     // Pointer to the type arena that allocated this type.
@@ -656,6 +650,8 @@ public:
     const TypeId unknownType;
     const TypeId neverType;
     const TypeId errorType;
+    const TypeId falsyType; // No type binding!
+    const TypeId truthyType; // No type binding!
 
     const TypePackId anyTypePack;
     const TypePackId neverTypePack;
@@ -703,7 +699,6 @@ T* getMutable(TypeId tv)
 
 const std::vector<TypeId>& getTypes(const UnionTypeVar* utv);
 const std::vector<TypeId>& getTypes(const IntersectionTypeVar* itv);
-const std::vector<TypeId>& getTypes(const ConstrainedTypeVar* ctv);
 
 template<typename T>
 struct TypeIterator;
@@ -716,10 +711,6 @@ using IntersectionTypeVarIterator = TypeIterator<IntersectionTypeVar>;
 IntersectionTypeVarIterator begin(const IntersectionTypeVar* itv);
 IntersectionTypeVarIterator end(const IntersectionTypeVar* itv);
 
-using ConstrainedTypeVarIterator = TypeIterator<ConstrainedTypeVar>;
-ConstrainedTypeVarIterator begin(const ConstrainedTypeVar* ctv);
-ConstrainedTypeVarIterator end(const ConstrainedTypeVar* ctv);
-
 /* Traverses the type T yielding each TypeId.
  * If the iterator encounters a nested type T, it will instead yield each TypeId within.
  */
@@ -793,7 +784,6 @@ struct TypeIterator
     // with templates portability in this area, so not worth it. Thanks MSVC.
     friend UnionTypeVarIterator end(const UnionTypeVar*);
     friend IntersectionTypeVarIterator end(const IntersectionTypeVar*);
-    friend ConstrainedTypeVarIterator end(const ConstrainedTypeVar*);
 
 private:
     TypeIterator() = default;

Analysis/include/Luau/Unifier.h

@@ -119,12 +119,7 @@ private:
 
     std::optional<TypeId> findTablePropertyRespectingMeta(TypeId lhsType, Name name);
 
-    void tryUnifyWithConstrainedSubTypeVar(TypeId subTy, TypeId superTy);
-    void tryUnifyWithConstrainedSuperTypeVar(TypeId subTy, TypeId superTy);
-
 public:
-    void unifyLowerBound(TypePackId subTy, TypePackId superTy, TypeLevel demotedLevel);
-
     // Returns true if the type "needle" already occurs within "haystack" and reports an "infinite type error"
     bool occursCheck(TypeId needle, TypeId haystack);
     bool occursCheck(DenseHashSet<TypeId>& seen, TypeId needle, TypeId haystack);

Analysis/include/Luau/Variant.h

@@ -105,7 +105,7 @@ public:
 
         tableDtor[typeId](&storage);
         typeId = tid;
-        new (&storage) TT(std::forward<Args>(args)...);
+        new (&storage) TT{std::forward<Args>(args)...};
 
         return *reinterpret_cast<T*>(&storage);
     }

Analysis/include/Luau/VisitTypeVar.h

@@ -103,10 +103,6 @@ struct GenericTypeVarVisitor
     {
         return visit(ty);
     }
-    virtual bool visit(TypeId ty, const ConstrainedTypeVar& ctv)
-    {
-        return visit(ty);
-    }
     virtual bool visit(TypeId ty, const PrimitiveTypeVar& ptv)
     {
         return visit(ty);
@@ -159,6 +155,14 @@ 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);
+    }
 
     virtual bool visit(TypePackId tp)
     {
@@ -216,14 +220,6 @@ struct GenericTypeVarVisitor
             visit(ty, *gtv);
         else if (auto etv = get<ErrorTypeVar>(ty))
             visit(ty, *etv);
-        else if (auto ctv = get<ConstrainedTypeVar>(ty))
-        {
-            if (visit(ty, *ctv))
-            {
-                for (TypeId part : ctv->parts)
-                    traverse(part);
-            }
-        }
         else if (auto ptv = get<PrimitiveTypeVar>(ty))
             visit(ty, *ptv);
         else if (auto ftv = get<FunctionTypeVar>(ty))
@@ -325,6 +321,10 @@ 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)
             return visit_detail::unsee(seen, ty);
         else

Analysis/src/Anyification.cpp

@@ -37,8 +37,6 @@ bool Anyification::isDirty(TypeId ty)
         return (ttv->state == TableState::Free || ttv->state == TableState::Unsealed);
     else if (log->getMutable<FreeTypeVar>(ty))
         return true;
-    else if (get<ConstrainedTypeVar>(ty))
-        return true;
     else
         return false;
 }
@@ -65,20 +63,8 @@ TypeId Anyification::clean(TypeId ty)
         clone.syntheticName = ttv->syntheticName;
         clone.tags = ttv->tags;
         TypeId res = addType(std::move(clone));
-        asMutable(res)->normal = ty->normal;
         return res;
     }
-    else if (auto ctv = get<ConstrainedTypeVar>(ty))
-    {
-        std::vector<TypeId> copy = ctv->parts;
-        for (TypeId& ty : copy)
-            ty = replace(ty);
-        TypeId res = copy.size() == 1 ? copy[0] : addType(UnionTypeVar{std::move(copy)});
-        auto [t, ok] = normalize(res, scope, *arena, singletonTypes, *iceHandler);
-        if (!ok)
-            normalizationTooComplex = true;
-        return t;
-    }
     else
         return anyType;
 }

Analysis/src/BuiltinDefinitions.cpp

@@ -10,6 +10,7 @@
 #include "Luau/TypeInfer.h"
 #include "Luau/TypePack.h"
 #include "Luau/TypeVar.h"
+#include "Luau/TypeUtils.h"
 
 #include <algorithm>
 
@@ -41,6 +42,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionRequire(
 
 static bool dcrMagicFunctionSelect(MagicFunctionCallContext context);
 static bool dcrMagicFunctionRequire(MagicFunctionCallContext context);
+static bool dcrMagicFunctionPack(MagicFunctionCallContext context);
 
 TypeId makeUnion(TypeArena& arena, std::vector<TypeId>&& types)
 {
@@ -333,6 +335,7 @@ void registerBuiltinGlobals(TypeChecker& typeChecker)
         ttv->props["clone"] = makeProperty(makeFunction(arena, std::nullopt, {tabTy}, {tabTy}), "@luau/global/table.clone");
 
         attachMagicFunction(ttv->props["pack"].type, magicFunctionPack);
+        attachDcrMagicFunction(ttv->props["pack"].type, dcrMagicFunctionPack);
     }
 
     attachMagicFunction(getGlobalBinding(typeChecker, "require"), magicFunctionRequire);
@@ -660,7 +663,7 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionPack(
             options.push_back(vtp->ty);
     }
 
-    options = typechecker.reduceUnion(options);
+    options = reduceUnion(options);
 
     // table.pack()         -> {| n: number, [number]: nil |}
     // table.pack(1)        -> {| n: number, [number]: number |}
@@ -679,6 +682,47 @@ static std::optional<WithPredicate<TypePackId>> magicFunctionPack(
     return WithPredicate<TypePackId>{arena.addTypePack({packedTable})};
 }
 
+static bool dcrMagicFunctionPack(MagicFunctionCallContext context)
+{
+
+    TypeArena* arena = context.solver->arena;
+
+    const auto& [paramTypes, paramTail] = flatten(context.arguments);
+
+    std::vector<TypeId> options;
+    options.reserve(paramTypes.size());
+    for (auto type : paramTypes)
+        options.push_back(type);
+
+    if (paramTail)
+    {
+        if (const VariadicTypePack* vtp = get<VariadicTypePack>(*paramTail))
+            options.push_back(vtp->ty);
+    }
+
+    options = reduceUnion(options);
+
+    // table.pack()         -> {| n: number, [number]: nil |}
+    // table.pack(1)        -> {| n: number, [number]: number |}
+    // table.pack(1, "foo") -> {| n: number, [number]: number | string |}
+    TypeId result = nullptr;
+    if (options.empty())
+        result = context.solver->singletonTypes->nilType;
+    else if (options.size() == 1)
+        result = options[0];
+    else
+        result = arena->addType(UnionTypeVar{std::move(options)});
+
+    TypeId numberType = context.solver->singletonTypes->numberType;
+    TypeId packedTable = arena->addType(
+        TableTypeVar{{{"n", {numberType}}}, TableIndexer(numberType, result), {}, TableState::Sealed});
+
+    TypePackId tableTypePack = arena->addTypePack({packedTable});
+    asMutable(context.result)->ty.emplace<BoundTypePack>(tableTypePack);
+
+    return true;
+}
+
 static bool checkRequirePath(TypeChecker& typechecker, AstExpr* expr)
 {
     // require(foo.parent.bar) will technically work, but it depends on legacy goop that

Analysis/src/Clone.cpp

@@ -1,6 +1,6 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-
 #include "Luau/Clone.h"
+
 #include "Luau/RecursionCounter.h"
 #include "Luau/TxnLog.h"
 #include "Luau/TypePack.h"
@@ -51,7 +51,6 @@ struct TypeCloner
     void operator()(const BlockedTypeVar& t);
     void operator()(const PendingExpansionTypeVar& t);
     void operator()(const PrimitiveTypeVar& t);
-    void operator()(const ConstrainedTypeVar& t);
     void operator()(const SingletonTypeVar& t);
     void operator()(const FunctionTypeVar& t);
     void operator()(const TableTypeVar& t);
@@ -63,6 +62,8 @@ 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);
 };
 
 struct TypePackCloner
@@ -198,21 +199,6 @@ void TypeCloner::operator()(const PrimitiveTypeVar& t)
     defaultClone(t);
 }
 
-void TypeCloner::operator()(const ConstrainedTypeVar& t)
-{
-    TypeId res = dest.addType(ConstrainedTypeVar{t.level});
-    ConstrainedTypeVar* ctv = getMutable<ConstrainedTypeVar>(res);
-    LUAU_ASSERT(ctv);
-
-    seenTypes[typeId] = res;
-
-    std::vector<TypeId> parts;
-    for (TypeId part : t.parts)
-        parts.push_back(clone(part, dest, cloneState));
-
-    ctv->parts = std::move(parts);
-}
-
 void TypeCloner::operator()(const SingletonTypeVar& t)
 {
     defaultClone(t);
@@ -352,6 +338,21 @@ 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{});
+    seenTypes[typeId] = result;
+
+    TypeId ty = clone(t.ty, dest, cloneState);
+    asMutable(result)->ty = NegationTypeVar{ty};
+}
+
 } // anonymous namespace
 
 TypePackId clone(TypePackId tp, TypeArena& dest, CloneState& cloneState)
@@ -390,7 +391,6 @@ TypeId clone(TypeId typeId, TypeArena& dest, CloneState& cloneState)
         if (!res->persistent)
         {
             asMutable(res)->documentationSymbol = typeId->documentationSymbol;
-            asMutable(res)->normal = typeId->normal;
         }
     }
 
@@ -478,11 +478,6 @@ TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool alwaysCl
         clone.parts = itv->parts;
         result = dest.addType(std::move(clone));
     }
-    else if (const ConstrainedTypeVar* ctv = get<ConstrainedTypeVar>(ty))
-    {
-        ConstrainedTypeVar clone{ctv->level, ctv->parts};
-        result = dest.addType(std::move(clone));
-    }
     else if (const PendingExpansionTypeVar* petv = get<PendingExpansionTypeVar>(ty))
     {
         PendingExpansionTypeVar clone{petv->prefix, petv->name, petv->typeArguments, petv->packArguments};
@@ -497,6 +492,10 @@ TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool alwaysCl
     {
         result = dest.addType(*ty);
     }
+    else if (const NegationTypeVar* ntv = get<NegationTypeVar>(ty))
+    {
+        result = dest.addType(NegationTypeVar{ntv->ty});
+    }
     else
         return result;
 
@@ -504,4 +503,9 @@ TypeId shallowClone(TypeId ty, TypeArena& dest, const TxnLog* log, bool alwaysCl
     return result;
 }
 
+TypeId shallowClone(TypeId ty, NotNull<TypeArena> dest)
+{
+    return shallowClone(ty, *dest, TxnLog::empty());
+}
+
 } // namespace Luau

Analysis/src/ConstraintGraphBuilder.cpp

@@ -1,20 +1,21 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-
 #include "Luau/ConstraintGraphBuilder.h"
+
 #include "Luau/Ast.h"
+#include "Luau/Clone.h"
 #include "Luau/Common.h"
 #include "Luau/Constraint.h"
+#include "Luau/DcrLogger.h"
 #include "Luau/ModuleResolver.h"
 #include "Luau/RecursionCounter.h"
+#include "Luau/Scope.h"
 #include "Luau/ToString.h"
-#include "Luau/DcrLogger.h"
+#include "Luau/TypeUtils.h"
 
 LUAU_FASTINT(LuauCheckRecursionLimit);
 LUAU_FASTFLAG(DebugLuauLogSolverToJson);
 LUAU_FASTFLAG(DebugLuauMagicTypes);
 
-#include "Luau/Scope.h"
-
 namespace Luau
 {
 
@@ -53,12 +54,13 @@ static bool matchSetmetatable(const AstExprCall& call)
 
 ConstraintGraphBuilder::ConstraintGraphBuilder(const ModuleName& moduleName, ModulePtr module, TypeArena* arena,
     NotNull<ModuleResolver> moduleResolver, NotNull<SingletonTypes> singletonTypes, NotNull<InternalErrorReporter> ice, const ScopePtr& globalScope,
-    DcrLogger* logger)
+    DcrLogger* logger, NotNull<DataFlowGraph> dfg)
     : moduleName(moduleName)
     , module(module)
     , singletonTypes(singletonTypes)
     , arena(arena)
     , rootScope(nullptr)
+    , dfg(dfg)
     , moduleResolver(moduleResolver)
     , ice(ice)
     , globalScope(globalScope)
@@ -95,14 +97,14 @@ ScopePtr ConstraintGraphBuilder::childScope(AstNode* node, const ScopePtr& paren
     return scope;
 }
 
-void ConstraintGraphBuilder::addConstraint(const ScopePtr& scope, const Location& location, ConstraintV cv)
+NotNull<Constraint> ConstraintGraphBuilder::addConstraint(const ScopePtr& scope, const Location& location, ConstraintV cv)
 {
-    scope->constraints.emplace_back(new Constraint{NotNull{scope.get()}, location, std::move(cv)});
+    return NotNull{scope->constraints.emplace_back(new Constraint{NotNull{scope.get()}, location, std::move(cv)}).get()};
 }
 
-void ConstraintGraphBuilder::addConstraint(const ScopePtr& scope, std::unique_ptr<Constraint> c)
+NotNull<Constraint> ConstraintGraphBuilder::addConstraint(const ScopePtr& scope, std::unique_ptr<Constraint> c)
 {
-    scope->constraints.emplace_back(std::move(c));
+    return NotNull{scope->constraints.emplace_back(std::move(c)).get()};
 }
 
 void ConstraintGraphBuilder::visit(AstStatBlock* block)
@@ -229,22 +231,16 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStat* stat)
 void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
 {
     std::vector<TypeId> varTypes;
+    varTypes.reserve(local->vars.size);
 
     for (AstLocal* local : local->vars)
     {
         TypeId ty = nullptr;
-        Location location = local->location;
 
         if (local->annotation)
-        {
-            location = local->annotation->location;
             ty = resolveType(scope, local->annotation, /* topLevel */ true);
-        }
-        else
-            ty = freshType(scope);
 
         varTypes.push_back(ty);
-        scope->bindings[local] = Binding{ty, location};
     }
 
     for (size_t i = 0; i < local->values.size; ++i)
@@ -257,6 +253,9 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
             // HACK: we leave nil-initialized things floating under the assumption that they will later be populated.
             // 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)
         {
@@ -268,6 +267,20 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
 
             if (i < local->vars.size)
             {
+                std::vector<TypeId> packTypes = flatten(*arena, singletonTypes, exprPack, varTypes.size() - i);
+
+                // fill out missing values in varTypes with values from exprPack
+                for (size_t j = i; j < varTypes.size(); ++j)
+                {
+                    if (!varTypes[j])
+                    {
+                        if (j - i < packTypes.size())
+                            varTypes[j] = packTypes[j - i];
+                        else
+                            varTypes[j] = freshType(scope);
+                    }
+                }
+
                 std::vector<TypeId> tailValues{varTypes.begin() + i, varTypes.end()};
                 TypePackId tailPack = arena->addTypePack(std::move(tailValues));
                 addConstraint(scope, local->location, PackSubtypeConstraint{exprPack, tailPack});
@@ -281,10 +294,31 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatLocal* local)
 
             TypeId exprType = check(scope, value, expectedType);
             if (i < varTypes.size())
-                addConstraint(scope, local->location, SubtypeConstraint{varTypes[i], exprType});
+            {
+                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)
+    {
+        AstLocal* l = local->vars.data[i];
+        Location location = l->location;
+
+        if (!varTypes[i])
+            varTypes[i] = freshType(scope);
+
+        scope->bindings[l] = Binding{varTypes[i], location};
+
+        // HACK: In the greedy solver, we say the type state of a variable is the type annotation itself, but
+        // the actual type state is the corresponding initializer expression (if it exists) or nil otherwise.
+        if (auto def = dfg->getDef(l))
+            scope->dcrRefinements[*def] = varTypes[i];
+    }
+
     if (local->values.size > 0)
     {
         // To correctly handle 'require', we need to import the exported type bindings into the variable 'namespace'.
@@ -510,7 +544,7 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatBlock* block)
 
 void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatAssign* assign)
 {
-    TypePackId varPackId = checkPack(scope, assign->vars);
+    TypePackId varPackId = checkLValues(scope, assign->vars);
     TypePackId valuePack = checkPack(scope, assign->values);
 
     addConstraint(scope, assign->location, PackSubtypeConstraint{valuePack, varPackId});
@@ -532,7 +566,10 @@ void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatCompoundAssign*
 
 void ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatIf* ifStatement)
 {
-    check(scope, ifStatement->condition);
+    // 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);
 
     ScopePtr thenScope = childScope(ifStatement->thenbody, scope);
     visit(thenScope, ifStatement->thenbody);
@@ -893,7 +930,7 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::
     TypeId result = nullptr;
 
     if (auto group = expr->as<AstExprGroup>())
-        result = check(scope, group->expr);
+        result = check(scope, group->expr, expectedType);
     else if (auto stringExpr = expr->as<AstExprConstantString>())
     {
         if (expectedType)
@@ -937,32 +974,14 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::
     }
     else if (expr->is<AstExprConstantNil>())
         result = singletonTypes->nilType;
-    else if (auto a = expr->as<AstExprLocal>())
+    else if (auto local = expr->as<AstExprLocal>())
-    {
+        result = check(scope, local);
-        std::optional<TypeId> ty = scope->lookup(a->local);
+    else if (auto global = expr->as<AstExprGlobal>())
-        if (ty)
+        result = check(scope, global);
-            result = *ty;
-        else
-            result = singletonTypes->errorRecoveryType(); // FIXME?  Record an error at this point?
-    }
-    else if (auto g = expr->as<AstExprGlobal>())
-    {
-        std::optional<TypeId> ty = scope->lookup(g->name);
-        if (ty)
-            result = *ty;
-        else
-        {
-            /* prepopulateGlobalScope() has already added all global functions to the environment by this point, so any
-             * global that is not already in-scope is definitely an unknown symbol.
-             */
-            reportError(g->location, UnknownSymbol{g->name.value});
-            result = singletonTypes->errorRecoveryType(); // FIXME?  Record an error at this point?
-        }
-    }
     else if (expr->is<AstExprVarargs>())
         result = flattenPack(scope, expr->location, checkPack(scope, expr));
     else if (expr->is<AstExprCall>())
-        result = flattenPack(scope, expr->location, checkPack(scope, expr));
+        result = flattenPack(scope, expr->location, checkPack(scope, expr)); // TODO: needs predicates too
     else if (auto a = expr->as<AstExprFunction>())
     {
         FunctionSignature sig = checkFunctionSignature(scope, a);
@@ -978,7 +997,7 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::
     else if (auto unary = expr->as<AstExprUnary>())
         result = check(scope, unary);
     else if (auto binary = expr->as<AstExprBinary>())
-        result = check(scope, binary);
+        result = check(scope, binary, expectedType);
     else if (auto ifElse = expr->as<AstExprIfElse>())
         result = check(scope, ifElse, expectedType);
     else if (auto typeAssert = expr->as<AstExprTypeAssertion>())
@@ -1002,6 +1021,37 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExpr* expr, std::
     return result;
 }
 
+TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprLocal* local)
+{
+    std::optional<TypeId> resultTy;
+
+    if (auto def = dfg->getDef(local))
+        resultTy = scope->lookup(*def);
+
+    if (!resultTy)
+    {
+        if (auto ty = scope->lookup(local->local))
+            resultTy = *ty;
+    }
+
+    if (!resultTy)
+        return singletonTypes->errorRecoveryType(); // TODO: replace with ice, locals should never exist before its definition.
+
+    return *resultTy;
+}
+
+TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprGlobal* global)
+{
+    if (std::optional<TypeId> ty = scope->lookup(global->name))
+        return *ty;
+
+    /* prepopulateGlobalScope() has already added all global functions to the environment by this point, so any
+     * global that is not already in-scope is definitely an unknown symbol.
+     */
+    reportError(global->location, UnknownSymbol{global->name.value});
+    return singletonTypes->errorRecoveryType();
+}
+
 TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexName* indexName)
 {
     TypeId obj = check(scope, indexName->expr);
@@ -1036,54 +1086,32 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIndexExpr* in
 
 TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprUnary* unary)
 {
-    TypeId operandType = check(scope, unary->expr);
+    TypeId operandType = check_(scope, unary);
-
     TypeId resultType = arena->addType(BlockedTypeVar{});
     addConstraint(scope, unary->location, UnaryConstraint{unary->op, operandType, resultType});
     return resultType;
 }
 
-TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprBinary* binary)
+TypeId ConstraintGraphBuilder::check_(const ScopePtr& scope, AstExprUnary* unary)
 {
-    TypeId leftType = check(scope, binary->left);
+    if (unary->op == AstExprUnary::Not)
-    TypeId rightType = check(scope, binary->right);
-    switch (binary->op)
     {
-    case AstExprBinary::And:
+        TypeId ty = check(scope, unary->expr, std::nullopt);
-    case AstExprBinary::Or:
+
-    {
+        return ty;
-        addConstraint(scope, binary->location, SubtypeConstraint{leftType, rightType});
-        return leftType;
-    }
-    case AstExprBinary::Add:
-    case AstExprBinary::Sub:
-    case AstExprBinary::Mul:
-    case AstExprBinary::Div:
-    case AstExprBinary::Mod:
-    case AstExprBinary::Pow:
-    case AstExprBinary::CompareNe:
-    case AstExprBinary::CompareEq:
-    case AstExprBinary::CompareLt:
-    case AstExprBinary::CompareLe:
-    case AstExprBinary::CompareGt:
-    case AstExprBinary::CompareGe:
-    {
-        TypeId resultType = arena->addType(BlockedTypeVar{});
-        addConstraint(scope, binary->location, BinaryConstraint{binary->op, leftType, rightType, resultType});
-        return resultType;
-    }
-    case AstExprBinary::Concat:
-    {
-        addConstraint(scope, binary->left->location, SubtypeConstraint{leftType, singletonTypes->stringType});
-        addConstraint(scope, binary->right->location, SubtypeConstraint{rightType, singletonTypes->stringType});
-        return singletonTypes->stringType;
-    }
-    default:
-        LUAU_ASSERT(0);
     }
 
-    LUAU_ASSERT(0);
+    return check(scope, unary->expr);
-    return nullptr;
+}
+
+TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprBinary* binary, std::optional<TypeId> expectedType)
+{
+    TypeId leftType = check(scope, binary->left, expectedType);
+    TypeId rightType = check(scope, binary->right, expectedType);
+
+    TypeId resultType = arena->addType(BlockedTypeVar{});
+    addConstraint(scope, binary->location, BinaryConstraint{binary->op, leftType, rightType, resultType});
+    return resultType;
 }
 
 TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIfElse* ifElse, std::optional<TypeId> expectedType)
@@ -1106,10 +1134,182 @@ TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprIfElse* ifEls
 
 TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTypeAssertion* typeAssert)
 {
-    check(scope, typeAssert->expr);
+    check(scope, typeAssert->expr, std::nullopt);
     return resolveType(scope, typeAssert->annotation);
 }
 
+TypePackId ConstraintGraphBuilder::checkLValues(const ScopePtr& scope, AstArray<AstExpr*> exprs)
+{
+    std::vector<TypeId> types;
+    types.reserve(exprs.size);
+
+    for (size_t i = 0; i < exprs.size; ++i)
+    {
+        AstExpr* const expr = exprs.data[i];
+        types.push_back(checkLValue(scope, expr));
+    }
+
+    return arena->addTypePack(std::move(types));
+}
+
+static bool isUnsealedTable(TypeId ty)
+{
+    ty = follow(ty);
+    const TableTypeVar* ttv = get<TableTypeVar>(ty);
+    return ttv && ttv->state == TableState::Unsealed;
+};
+
+/**
+ * If the expr is a dotted set of names, and if the root symbol refers to an
+ * unsealed table, return that table type, plus the indeces that follow as a
+ * vector.
+ */
+static std::optional<std::pair<Symbol, std::vector<const char*>>> extractDottedName(AstExpr* expr)
+{
+    std::vector<const char*> names;
+
+    while (expr)
+    {
+        if (auto global = expr->as<AstExprGlobal>())
+        {
+            std::reverse(begin(names), end(names));
+            return std::pair{global->name, std::move(names)};
+        }
+        else if (auto local = expr->as<AstExprLocal>())
+        {
+            std::reverse(begin(names), end(names));
+            return std::pair{local->local, std::move(names)};
+        }
+        else if (auto indexName = expr->as<AstExprIndexName>())
+        {
+            names.push_back(indexName->index.value);
+            expr = indexName->expr;
+        }
+        else
+            return std::nullopt;
+    }
+
+    return std::nullopt;
+}
+
+/**
+ * Create a shallow copy of `ty` and its properties along `path`.  Insert a new
+ * property (the last segment of `path`) into the tail table with the value `t`.
+ *
+ * On success, returns the new outermost table type.  If the root table or any
+ * of its subkeys are not unsealed tables, the function fails and returns
+ * std::nullopt.
+ *
+ * TODO: Prove that we completely give up in the face of indexers and
+ * metatables.
+ */
+static std::optional<TypeId> updateTheTableType(NotNull<TypeArena> arena, TypeId ty, const std::vector<const char*>& path, TypeId replaceTy)
+{
+    if (path.empty())
+        return std::nullopt;
+
+    // First walk the path and ensure that it's unsealed tables all the way
+    // to the end.
+    {
+        TypeId t = ty;
+        for (size_t i = 0; i < path.size() - 1; ++i)
+        {
+            if (!isUnsealedTable(t))
+                return std::nullopt;
+
+            const TableTypeVar* tbl = get<TableTypeVar>(t);
+            auto it = tbl->props.find(path[i]);
+            if (it == tbl->props.end())
+                return std::nullopt;
+
+            t = it->second.type;
+        }
+
+        // The last path segment should not be a property of the table at all.
+        // We are not changing property types.  We are only admitting this one
+        // new property to be appended.
+        if (!isUnsealedTable(t))
+            return std::nullopt;
+        const TableTypeVar* tbl = get<TableTypeVar>(t);
+        auto it = tbl->props.find(path.back());
+        if (it != tbl->props.end())
+            return std::nullopt;
+    }
+
+    const TypeId res = shallowClone(ty, arena);
+    TypeId t = res;
+
+    for (size_t i = 0; i < path.size() - 1; ++i)
+    {
+        const std::string segment = path[i];
+
+        TableTypeVar* ttv = getMutable<TableTypeVar>(t);
+        LUAU_ASSERT(ttv);
+
+        auto propIt = ttv->props.find(segment);
+        if (propIt != ttv->props.end())
+        {
+            LUAU_ASSERT(isUnsealedTable(propIt->second.type));
+            t = shallowClone(follow(propIt->second.type), arena);
+            ttv->props[segment].type = t;
+        }
+        else
+            return std::nullopt;
+    }
+
+    TableTypeVar* ttv = getMutable<TableTypeVar>(t);
+    LUAU_ASSERT(ttv);
+
+    const std::string lastSegment = path.back();
+    LUAU_ASSERT(0 == ttv->props.count(lastSegment));
+    ttv->props[lastSegment] = Property{replaceTy};
+    return res;
+}
+
+/**
+ * This function is mostly about identifying properties that are being inserted into unsealed tables.
+ *
+ * If expr has the form name.a.b.c
+ */
+TypeId ConstraintGraphBuilder::checkLValue(const ScopePtr& scope, AstExpr* expr)
+{
+    if (auto indexExpr = expr->as<AstExprIndexExpr>())
+    {
+        if (auto constantString = indexExpr->index->as<AstExprConstantString>())
+        {
+            AstName syntheticIndex{constantString->value.data};
+            AstExprIndexName synthetic{
+                indexExpr->location, indexExpr->expr, syntheticIndex, constantString->location, indexExpr->expr->location.end, '.'};
+            return checkLValue(scope, &synthetic);
+        }
+    }
+
+    auto dottedPath = extractDottedName(expr);
+    if (!dottedPath)
+        return check(scope, expr);
+    const auto [sym, segments] = std::move(*dottedPath);
+
+    if (!sym.local)
+        return check(scope, expr);
+
+    auto lookupResult = scope->lookupEx(sym);
+    if (!lookupResult)
+        return check(scope, expr);
+    const auto [ty, symbolScope] = std::move(*lookupResult);
+
+    TypeId replaceTy = arena->freshType(scope.get());
+
+    std::optional<TypeId> updatedType = updateTheTableType(arena, ty, segments, replaceTy);
+    if (!updatedType)
+        return check(scope, expr);
+
+    std::optional<DefId> def = dfg->getDef(sym);
+    LUAU_ASSERT(def);
+    symbolScope->bindings[sym].typeId = *updatedType;
+    symbolScope->dcrRefinements[*def] = *updatedType;
+    return replaceTy;
+}
+
 TypeId ConstraintGraphBuilder::check(const ScopePtr& scope, AstExprTable* expr, std::optional<TypeId> expectedType)
 {
     TypeId ty = arena->addType(TableTypeVar{});
@@ -1275,6 +1475,9 @@ ConstraintGraphBuilder::FunctionSignature ConstraintGraphBuilder::checkFunctionS
         argTypes.push_back(t);
         signatureScope->bindings[local] = Binding{t, local->location};
 
+        if (auto def = dfg->getDef(local))
+            signatureScope->dcrRefinements[*def] = t;
+
         if (local->annotation)
         {
             TypeId argAnnotation = resolveType(signatureScope, local->annotation, /* topLevel */ true);

Analysis/src/ConstraintSolver.cpp

@@ -3,14 +3,16 @@
 #include "Luau/Anyification.h"
 #include "Luau/ApplyTypeFunction.h"
 #include "Luau/ConstraintSolver.h"
+#include "Luau/DcrLogger.h"
 #include "Luau/Instantiation.h"
 #include "Luau/Location.h"
+#include "Luau/Metamethods.h"
 #include "Luau/ModuleResolver.h"
 #include "Luau/Quantify.h"
 #include "Luau/ToString.h"
+#include "Luau/TypeUtils.h"
 #include "Luau/TypeVar.h"
 #include "Luau/Unifier.h"
-#include "Luau/DcrLogger.h"
 #include "Luau/VisitTypeVar.h"
 #include "Luau/TypeUtils.h"
 
@@ -438,6 +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))
+        success = tryDispatch(*rc, constraint);
     else
         LUAU_ASSERT(false);
 
@@ -564,44 +568,192 @@ bool ConstraintSolver::tryDispatch(const BinaryConstraint& c, NotNull<const Cons
     TypeId rightType = follow(c.rightType);
     TypeId resultType = follow(c.resultType);
 
-    if (isBlocked(leftType) || isBlocked(rightType))
+    bool isLogical = c.op == AstExprBinary::Op::And || c.op == AstExprBinary::Op::Or;
-    {
-        /* Compound assignments create constraints of the form
-         *
-         *     A <: Binary<op, A, B>
-         *
-         * This constraint is the one that is meant to unblock A, so it doesn't
-         * make any sense to stop and wait for someone else to do it.
-         */
-        if (leftType != resultType && rightType != resultType)
-        {
-            block(c.leftType, constraint);
-            block(c.rightType, constraint);
-            return false;
-        }
-    }
 
-    if (isNumber(leftType))
+    /* Compound assignments create constraints of the form
-    {
+     *
-        unify(leftType, rightType, constraint->scope);
+     *     A <: Binary<op, A, B>
-        asMutable(resultType)->ty.emplace<BoundTypeVar>(leftType);
+     *
-        return true;
+     * This constraint is the one that is meant to unblock A, so it doesn't
-    }
+     * make any sense to stop and wait for someone else to do it.
+     */
+
+    if (isBlocked(leftType) && leftType != resultType)
+        return block(c.leftType, constraint);
+
+    if (isBlocked(rightType) && rightType != resultType)
+        return block(c.rightType, constraint);
 
     if (!force)
     {
-        if (get<FreeTypeVar>(leftType))
+        // Logical expressions may proceed if the LHS is free.
+        if (get<FreeTypeVar>(leftType) && !isLogical)
             return block(leftType, constraint);
     }
 
-    if (isBlocked(leftType))
+    // Logical expressions may proceed if the LHS is free.
+    if (isBlocked(leftType) || (get<FreeTypeVar>(leftType) && !isLogical))
     {
         asMutable(resultType)->ty.emplace<BoundTypeVar>(errorRecoveryType());
-        // reportError(constraint->location, CannotInferBinaryOperation{c.op, std::nullopt, CannotInferBinaryOperation::Operation});
+        unblock(resultType);
         return true;
     }
 
-    // TODO metatables, classes
+    // For or expressions, the LHS will never have nil as a possible output.
+    // Consider:
+    // local foo = nil or 2
+    // `foo` will always be 2.
+    if (c.op == AstExprBinary::Op::Or)
+        leftType = stripNil(singletonTypes, *arena, leftType);
+
+    // Metatables go first, even if there is primitive behavior.
+    if (auto it = kBinaryOpMetamethods.find(c.op); it != kBinaryOpMetamethods.end())
+    {
+        // Metatables are not the same. The metamethod will not be invoked.
+        if ((c.op == AstExprBinary::Op::CompareEq || c.op == AstExprBinary::Op::CompareNe) &&
+            getMetatable(leftType, singletonTypes) != getMetatable(rightType, singletonTypes))
+        {
+            // TODO: Boolean singleton false? The result is _always_ boolean false.
+            asMutable(resultType)->ty.emplace<BoundTypeVar>(singletonTypes->booleanType);
+            unblock(resultType);
+            return true;
+        }
+
+        std::optional<TypeId> mm;
+
+        // The LHS metatable takes priority over the RHS metatable, where
+        // present.
+        if (std::optional<TypeId> leftMm = findMetatableEntry(singletonTypes, errors, leftType, it->second, constraint->location))
+            mm = leftMm;
+        else if (std::optional<TypeId> rightMm = findMetatableEntry(singletonTypes, errors, rightType, it->second, constraint->location))
+            mm = rightMm;
+
+        if (mm)
+        {
+            // TODO: Is a table with __call legal here?
+            // TODO: Overloads
+            if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(follow(*mm)))
+            {
+                TypePackId inferredArgs;
+                // For >= and > we invoke __lt and __le respectively with
+                // swapped argument ordering.
+                if (c.op == AstExprBinary::Op::CompareGe || c.op == AstExprBinary::Op::CompareGt)
+                {
+                    inferredArgs = arena->addTypePack({rightType, leftType});
+                }
+                else
+                {
+                    inferredArgs = arena->addTypePack({leftType, rightType});
+                }
+
+                unify(inferredArgs, ftv->argTypes, constraint->scope);
+
+                TypeId mmResult;
+
+                // Comparison operations always evaluate to a boolean,
+                // regardless of what the metamethod returns.
+                switch (c.op)
+                {
+                case AstExprBinary::Op::CompareEq:
+                case AstExprBinary::Op::CompareNe:
+                case AstExprBinary::Op::CompareGe:
+                case AstExprBinary::Op::CompareGt:
+                case AstExprBinary::Op::CompareLe:
+                case AstExprBinary::Op::CompareLt:
+                    mmResult = singletonTypes->booleanType;
+                    break;
+                default:
+                    mmResult = first(ftv->retTypes).value_or(errorRecoveryType());
+                }
+
+                asMutable(resultType)->ty.emplace<BoundTypeVar>(mmResult);
+                unblock(resultType);
+                return true;
+            }
+        }
+
+        // If there's no metamethod available, fall back to primitive behavior.
+    }
+
+    // If any is present, the expression must evaluate to any as well.
+    bool leftAny = get<AnyTypeVar>(leftType) || get<ErrorTypeVar>(leftType);
+    bool rightAny = get<AnyTypeVar>(rightType) || get<ErrorTypeVar>(rightType);
+    bool anyPresent = leftAny || rightAny;
+
+    switch (c.op)
+    {
+    // For arithmetic operators, if the LHS is a number, the RHS must be a
+    // number as well. The result will also be a number.
+    case AstExprBinary::Op::Add:
+    case AstExprBinary::Op::Sub:
+    case AstExprBinary::Op::Mul:
+    case AstExprBinary::Op::Div:
+    case AstExprBinary::Op::Pow:
+    case AstExprBinary::Op::Mod:
+        if (isNumber(leftType))
+        {
+            unify(leftType, rightType, constraint->scope);
+            asMutable(resultType)->ty.emplace<BoundTypeVar>(anyPresent ? singletonTypes->anyType : leftType);
+            unblock(resultType);
+            return true;
+        }
+
+        break;
+    // For concatenation, if the LHS is a string, the RHS must be a string as
+    // well. The result will also be a string.
+    case AstExprBinary::Op::Concat:
+        if (isString(leftType))
+        {
+            unify(leftType, rightType, constraint->scope);
+            asMutable(resultType)->ty.emplace<BoundTypeVar>(anyPresent ? singletonTypes->anyType : leftType);
+            unblock(resultType);
+            return true;
+        }
+
+        break;
+    // Inexact comparisons require that the types be both numbers or both
+    // strings, and evaluate to a boolean.
+    case AstExprBinary::Op::CompareGe:
+    case AstExprBinary::Op::CompareGt:
+    case AstExprBinary::Op::CompareLe:
+    case AstExprBinary::Op::CompareLt:
+        if ((isNumber(leftType) && isNumber(rightType)) || (isString(leftType) && isString(rightType)))
+        {
+            asMutable(resultType)->ty.emplace<BoundTypeVar>(singletonTypes->booleanType);
+            unblock(resultType);
+            return true;
+        }
+
+        break;
+    // == and ~= always evaluate to a boolean, and impose no other constraints
+    // on their parameters.
+    case AstExprBinary::Op::CompareEq:
+    case AstExprBinary::Op::CompareNe:
+        asMutable(resultType)->ty.emplace<BoundTypeVar>(singletonTypes->booleanType);
+        unblock(resultType);
+        return true;
+    // And evalutes to a boolean if the LHS is falsey, and the RHS type if LHS is
+    // truthy.
+    case AstExprBinary::Op::And:
+        asMutable(resultType)->ty.emplace<BoundTypeVar>(unionOfTypes(rightType, singletonTypes->booleanType, constraint->scope, false));
+        unblock(resultType);
+        return true;
+    // Or evaluates to the LHS type if the LHS is truthy, and the RHS type if
+    // LHS is falsey.
+    case AstExprBinary::Op::Or:
+        asMutable(resultType)->ty.emplace<BoundTypeVar>(unionOfTypes(rightType, leftType, constraint->scope, true));
+        unblock(resultType);
+        return true;
+    default:
+        iceReporter.ice("Unhandled AstExprBinary::Op for binary operation", constraint->location);
+        break;
+    }
+
+    // We failed to either evaluate a metamethod or invoke primitive behavior.
+    unify(leftType, errorRecoveryType(), constraint->scope);
+    unify(rightType, errorRecoveryType(), constraint->scope);
+    asMutable(resultType)->ty.emplace<BoundTypeVar>(errorRecoveryType());
+    unblock(resultType);
 
     return true;
 }
@@ -943,6 +1095,31 @@ bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<cons
         return block(c.fn, constraint);
     }
 
+    // We don't support magic __call metamethods.
+    if (std::optional<TypeId> callMm = findMetatableEntry(singletonTypes, errors, fn, "__call", constraint->location))
+    {
+        std::vector<TypeId> args{fn};
+
+        for (TypeId arg : c.argsPack)
+            args.push_back(arg);
+
+        TypeId instantiatedType = arena->addType(BlockedTypeVar{});
+        TypeId inferredFnType =
+            arena->addType(FunctionTypeVar(TypeLevel{}, constraint->scope.get(), arena->addTypePack(TypePack{args, {}}), c.result));
+
+        // Alter the inner constraints.
+        LUAU_ASSERT(c.innerConstraints.size() == 2);
+
+        asMutable(*c.innerConstraints.at(0)).c = InstantiationConstraint{instantiatedType, *callMm};
+        asMutable(*c.innerConstraints.at(1)).c = SubtypeConstraint{inferredFnType, instantiatedType};
+
+        unsolvedConstraints.insert(end(unsolvedConstraints), begin(c.innerConstraints), end(c.innerConstraints));
+
+        asMutable(c.result)->ty.emplace<FreeTypePack>(constraint->scope);
+        unblock(c.result);
+        return true;
+    }
+
     const FunctionTypeVar* ftv = get<FunctionTypeVar>(fn);
     bool usedMagic = false;
 
@@ -1059,6 +1236,29 @@ bool ConstraintSolver::tryDispatch(const HasPropConstraint& c, NotNull<const Con
     return true;
 }
 
+bool ConstraintSolver::tryDispatch(const RefinementConstraint& c, NotNull<const Constraint> constraint)
+{
+    // TODO: Figure out exact details on when refinements need to be blocked.
+    // It's possible that it never needs to be, since we can just use intersection types with the discriminant type?
+
+    if (!constraint->scope->parent)
+        iceReporter.ice("No parent scope");
+
+    std::optional<TypeId> previousTy = constraint->scope->parent->lookup(c.def);
+    if (!previousTy)
+        iceReporter.ice("No previous type");
+
+    std::optional<TypeId> useTy = constraint->scope->lookup(c.def);
+    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;
+}
+
 bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const IterableConstraint& c, NotNull<const Constraint> constraint, bool force)
 {
     auto block_ = [&](auto&& t) {
@@ -1502,4 +1702,39 @@ TypePackId ConstraintSolver::errorRecoveryTypePack() const
     return singletonTypes->errorRecoveryTypePack();
 }
 
+TypeId ConstraintSolver::unionOfTypes(TypeId a, TypeId b, NotNull<Scope> scope, bool unifyFreeTypes)
+{
+    a = follow(a);
+    b = follow(b);
+
+    if (unifyFreeTypes && (get<FreeTypeVar>(a) || get<FreeTypeVar>(b)))
+    {
+        Unifier u{normalizer, Mode::Strict, scope, Location{}, Covariant};
+        u.useScopes = true;
+        u.tryUnify(b, a);
+
+        if (u.errors.empty())
+        {
+            u.log.commit();
+            return a;
+        }
+        else
+        {
+            return singletonTypes->errorRecoveryType(singletonTypes->anyType);
+        }
+    }
+
+    if (*a == *b)
+        return a;
+
+    std::vector<TypeId> types = reduceUnion({a, b});
+    if (types.empty())
+        return singletonTypes->neverType;
+
+    if (types.size() == 1)
+        return types[0];
+
+    return arena->addType(UnionTypeVar{types});
+}
+
 } // namespace Luau

Analysis/src/DataFlowGraphBuilder.cpp

@@ -0,0 +1,440 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/DataFlowGraphBuilder.h"
+
+#include "Luau/Error.h"
+
+LUAU_FASTFLAG(DebugLuauFreezeArena)
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+
+namespace Luau
+{
+
+std::optional<DefId> DataFlowGraph::getDef(const AstExpr* expr) const
+{
+    if (auto def = astDefs.find(expr))
+        return NotNull{*def};
+    return std::nullopt;
+}
+
+std::optional<DefId> DataFlowGraph::getDef(const AstLocal* local) const
+{
+    if (auto def = localDefs.find(local))
+        return NotNull{*def};
+    return std::nullopt;
+}
+
+std::optional<DefId> DataFlowGraph::getDef(const Symbol& symbol) const
+{
+    if (symbol.local)
+        return getDef(symbol.local);
+    else
+        return std::nullopt;
+}
+
+DataFlowGraph DataFlowGraphBuilder::build(AstStatBlock* block, NotNull<InternalErrorReporter> handle)
+{
+    LUAU_ASSERT(FFlag::DebugLuauDeferredConstraintResolution);
+
+    DataFlowGraphBuilder builder;
+    builder.handle = handle;
+    builder.visit(nullptr, block); // nullptr is the root DFG scope.
+    if (FFlag::DebugLuauFreezeArena)
+        builder.arena->allocator.freeze();
+    return std::move(builder.graph);
+}
+
+DfgScope* DataFlowGraphBuilder::childScope(DfgScope* scope)
+{
+    return scopes.emplace_back(new DfgScope{scope}).get();
+}
+
+std::optional<DefId> DataFlowGraphBuilder::use(DfgScope* scope, Symbol symbol, AstExpr* e)
+{
+    for (DfgScope* current = scope; current; current = current->parent)
+    {
+        if (auto loc = current->bindings.find(symbol))
+        {
+            graph.astDefs[e] = *loc;
+            return NotNull{*loc};
+        }
+    }
+
+    return std::nullopt;
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatBlock* b)
+{
+    DfgScope* child = childScope(scope);
+    return visitBlockWithoutChildScope(child, b);
+}
+
+void DataFlowGraphBuilder::visitBlockWithoutChildScope(DfgScope* scope, AstStatBlock* b)
+{
+    for (AstStat* s : b->body)
+        visit(scope, s);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStat* s)
+{
+    if (auto b = s->as<AstStatBlock>())
+        return visit(scope, b);
+    else if (auto i = s->as<AstStatIf>())
+        return visit(scope, i);
+    else if (auto w = s->as<AstStatWhile>())
+        return visit(scope, w);
+    else if (auto r = s->as<AstStatRepeat>())
+        return visit(scope, r);
+    else if (auto b = s->as<AstStatBreak>())
+        return visit(scope, b);
+    else if (auto c = s->as<AstStatContinue>())
+        return visit(scope, c);
+    else if (auto r = s->as<AstStatReturn>())
+        return visit(scope, r);
+    else if (auto e = s->as<AstStatExpr>())
+        return visit(scope, e);
+    else if (auto l = s->as<AstStatLocal>())
+        return visit(scope, l);
+    else if (auto f = s->as<AstStatFor>())
+        return visit(scope, f);
+    else if (auto f = s->as<AstStatForIn>())
+        return visit(scope, f);
+    else if (auto a = s->as<AstStatAssign>())
+        return visit(scope, a);
+    else if (auto c = s->as<AstStatCompoundAssign>())
+        return visit(scope, c);
+    else if (auto f = s->as<AstStatFunction>())
+        return visit(scope, f);
+    else if (auto l = s->as<AstStatLocalFunction>())
+        return visit(scope, l);
+    else if (auto t = s->as<AstStatTypeAlias>())
+        return; // ok
+    else if (auto d = s->as<AstStatDeclareFunction>())
+        return; // ok
+    else if (auto d = s->as<AstStatDeclareGlobal>())
+        return; // ok
+    else if (auto d = s->as<AstStatDeclareFunction>())
+        return; // ok
+    else if (auto d = s->as<AstStatDeclareClass>())
+        return; // ok
+    else if (auto _ = s->as<AstStatError>())
+        return; // ok
+    else
+        handle->ice("Unknown AstStat in DataFlowGraphBuilder");
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatIf* i)
+{
+    DfgScope* condScope = childScope(scope);
+    visitExpr(condScope, i->condition);
+    visit(condScope, i->thenbody);
+
+    if (i->elsebody)
+        visit(scope, i->elsebody);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatWhile* w)
+{
+    // TODO(controlflow): entry point has a back edge from exit point
+    DfgScope* whileScope = childScope(scope);
+    visitExpr(whileScope, w->condition);
+    visit(whileScope, w->body);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatRepeat* r)
+{
+    // TODO(controlflow): entry point has a back edge from exit point
+    DfgScope* repeatScope = childScope(scope); // TODO: loop scope.
+    visitBlockWithoutChildScope(repeatScope, r->body);
+    visitExpr(repeatScope, r->condition);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatBreak* b)
+{
+    // TODO: Control flow analysis
+    return; // ok
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatContinue* c)
+{
+    // TODO: Control flow analysis
+    return; // ok
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatReturn* r)
+{
+    // TODO: Control flow analysis
+    for (AstExpr* e : r->list)
+        visitExpr(scope, e);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatExpr* e)
+{
+    visitExpr(scope, e->expr);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatLocal* l)
+{
+    // TODO: alias tracking
+    for (AstExpr* e : l->values)
+        visitExpr(scope, e);
+
+    for (AstLocal* local : l->vars)
+    {
+        DefId def = arena->freshDef();
+        graph.localDefs[local] = def;
+        scope->bindings[local] = def;
+    }
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatFor* f)
+{
+    DfgScope* forScope = childScope(scope); // TODO: loop scope.
+    DefId def = arena->freshDef();
+    graph.localDefs[f->var] = def;
+    scope->bindings[f->var] = def;
+
+    // TODO(controlflow): entry point has a back edge from exit point
+    visit(forScope, f->body);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatForIn* f)
+{
+    DfgScope* forScope = childScope(scope); // TODO: loop scope.
+
+    for (AstLocal* local : f->vars)
+    {
+        DefId def = arena->freshDef();
+        graph.localDefs[local] = def;
+        forScope->bindings[local] = def;
+    }
+
+    // TODO(controlflow): entry point has a back edge from exit point
+    for (AstExpr* e : f->values)
+        visitExpr(forScope, e);
+
+    visit(forScope, f->body);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatAssign* a)
+{
+    for (AstExpr* r : a->values)
+        visitExpr(scope, r);
+
+    for (AstExpr* l : a->vars)
+    {
+        AstExpr* root = l;
+
+        bool isUpdatable = true;
+        while (true)
+        {
+            if (root->is<AstExprLocal>() || root->is<AstExprGlobal>())
+                break;
+
+            AstExprIndexName* indexName = root->as<AstExprIndexName>();
+            if (!indexName)
+            {
+                isUpdatable = false;
+                break;
+            }
+
+            root = indexName->expr;
+        }
+
+        if (isUpdatable)
+        {
+            // TODO global?
+            if (auto exprLocal = root->as<AstExprLocal>())
+            {
+                DefId def = arena->freshDef();
+                graph.astDefs[exprLocal] = def;
+
+                // Update the def in the scope that introduced the local.  Not
+                // the current scope.
+                AstLocal* local = exprLocal->local;
+                DfgScope* s = scope;
+                while (s && !s->bindings.find(local))
+                    s = s->parent;
+                LUAU_ASSERT(s && s->bindings.find(local));
+                s->bindings[local] = def;
+            }
+        }
+
+        visitExpr(scope, l); // TODO: they point to a new def!!
+    }
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatCompoundAssign* c)
+{
+    // TODO(typestates): The lhs is being read and written to. This might or might not be annoying.
+    visitExpr(scope, c->value);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatFunction* f)
+{
+    visitExpr(scope, f->name);
+    visitExpr(scope, f->func);
+}
+
+void DataFlowGraphBuilder::visit(DfgScope* scope, AstStatLocalFunction* l)
+{
+    DefId def = arena->freshDef();
+    graph.localDefs[l->name] = def;
+    scope->bindings[l->name] = def;
+
+    visitExpr(scope, l->func);
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExpr* e)
+{
+    if (auto g = e->as<AstExprGroup>())
+        return visitExpr(scope, g->expr);
+    else if (auto c = e->as<AstExprConstantNil>())
+        return {}; // ok
+    else if (auto c = e->as<AstExprConstantBool>())
+        return {}; // ok
+    else if (auto c = e->as<AstExprConstantNumber>())
+        return {}; // ok
+    else if (auto c = e->as<AstExprConstantString>())
+        return {}; // ok
+    else if (auto l = e->as<AstExprLocal>())
+        return visitExpr(scope, l);
+    else if (auto g = e->as<AstExprGlobal>())
+        return visitExpr(scope, g);
+    else if (auto v = e->as<AstExprVarargs>())
+        return {}; // ok
+    else if (auto c = e->as<AstExprCall>())
+        return visitExpr(scope, c);
+    else if (auto i = e->as<AstExprIndexName>())
+        return visitExpr(scope, i);
+    else if (auto i = e->as<AstExprIndexExpr>())
+        return visitExpr(scope, i);
+    else if (auto f = e->as<AstExprFunction>())
+        return visitExpr(scope, f);
+    else if (auto t = e->as<AstExprTable>())
+        return visitExpr(scope, t);
+    else if (auto u = e->as<AstExprUnary>())
+        return visitExpr(scope, u);
+    else if (auto b = e->as<AstExprBinary>())
+        return visitExpr(scope, b);
+    else if (auto t = e->as<AstExprTypeAssertion>())
+        return visitExpr(scope, t);
+    else if (auto i = e->as<AstExprIfElse>())
+        return visitExpr(scope, i);
+    else if (auto i = e->as<AstExprInterpString>())
+        return visitExpr(scope, i);
+    else if (auto _ = e->as<AstExprError>())
+        return {}; // ok
+    else
+        handle->ice("Unknown AstExpr in DataFlowGraphBuilder");
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprLocal* l)
+{
+    return {use(scope, l->local, l)};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprGlobal* g)
+{
+    return {use(scope, g->name, g)};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprCall* c)
+{
+    visitExpr(scope, c->func);
+
+    for (AstExpr* arg : c->args)
+        visitExpr(scope, arg);
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprIndexName* i)
+{
+    std::optional<DefId> def = visitExpr(scope, i->expr).def;
+    if (!def)
+        return {};
+
+    // TODO: properties for the above def.
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprIndexExpr* i)
+{
+    visitExpr(scope, i->expr);
+    visitExpr(scope, i->expr);
+
+    if (i->index->as<AstExprConstantString>())
+    {
+        // TODO: properties for the def
+    }
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprFunction* f)
+{
+    if (AstLocal* self = f->self)
+    {
+        DefId def = arena->freshDef();
+        graph.localDefs[self] = def;
+        scope->bindings[self] = def;
+    }
+
+    for (AstLocal* param : f->args)
+    {
+        DefId def = arena->freshDef();
+        graph.localDefs[param] = def;
+        scope->bindings[param] = def;
+    }
+
+    visit(scope, f->body);
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprTable* t)
+{
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprUnary* u)
+{
+    visitExpr(scope, u->expr);
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprBinary* b)
+{
+    visitExpr(scope, b->left);
+    visitExpr(scope, b->right);
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprTypeAssertion* t)
+{
+    ExpressionFlowGraph result = visitExpr(scope, t->expr);
+    // TODO: visit type
+    return result;
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprIfElse* i)
+{
+    DfgScope* condScope = childScope(scope);
+    visitExpr(condScope, i->condition);
+    visitExpr(condScope, i->trueExpr);
+
+    visitExpr(scope, i->falseExpr);
+
+    return {};
+}
+
+ExpressionFlowGraph DataFlowGraphBuilder::visitExpr(DfgScope* scope, AstExprInterpString* i)
+{
+    for (AstExpr* e : i->expressions)
+        visitExpr(scope, e);
+    return {};
+}
+
+} // namespace Luau

Analysis/src/Def.cpp

@@ -0,0 +1,12 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/Def.h"
+
+namespace Luau
+{
+
+DefId DefArena::freshDef()
+{
+    return NotNull{allocator.allocate<Def>(Undefined{})};
+}
+
+} // namespace Luau

Analysis/src/Error.cpp

@@ -7,8 +7,6 @@
 
 #include <stdexcept>
 
-LUAU_FASTFLAGVARIABLE(LuauTypeMismatchModuleNameResolution, false)
-
 static std::string wrongNumberOfArgsString(
     size_t expectedCount, std::optional<size_t> maximumCount, size_t actualCount, const char* argPrefix = nullptr, bool isVariadic = false)
 {
@@ -70,7 +68,7 @@ struct ErrorConverter
             {
                 if (auto wantedDefinitionModule = getDefinitionModuleName(tm.wantedType))
                 {
-                    if (FFlag::LuauTypeMismatchModuleNameResolution && fileResolver != nullptr)
+                    if (fileResolver != nullptr)
                     {
                         std::string givenModuleName = fileResolver->getHumanReadableModuleName(*givenDefinitionModule);
                         std::string wantedModuleName = fileResolver->getHumanReadableModuleName(*wantedDefinitionModule);
@@ -96,14 +94,7 @@ struct ErrorConverter
             if (!tm.reason.empty())
                 result += tm.reason + " ";
 
-            if (FFlag::LuauTypeMismatchModuleNameResolution)
+            result += Luau::toString(*tm.error, TypeErrorToStringOptions{fileResolver});
-            {
-                result += Luau::toString(*tm.error, TypeErrorToStringOptions{fileResolver});
-            }
-            else
-            {
-                result += Luau::toString(*tm.error);
-            }
         }
         else if (!tm.reason.empty())
         {

Analysis/src/Frontend.cpp

@@ -1,11 +1,13 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/Frontend.h"
 
+#include "Luau/BuiltinDefinitions.h"
 #include "Luau/Clone.h"
 #include "Luau/Common.h"
 #include "Luau/Config.h"
 #include "Luau/ConstraintGraphBuilder.h"
 #include "Luau/ConstraintSolver.h"
+#include "Luau/DataFlowGraphBuilder.h"
 #include "Luau/DcrLogger.h"
 #include "Luau/FileResolver.h"
 #include "Luau/Parser.h"
@@ -15,7 +17,6 @@
 #include "Luau/TypeChecker2.h"
 #include "Luau/TypeInfer.h"
 #include "Luau/Variant.h"
-#include "Luau/BuiltinDefinitions.h"
 
 #include <algorithm>
 #include <chrono>
@@ -26,7 +27,6 @@ LUAU_FASTINT(LuauTarjanChildLimit)
 LUAU_FASTFLAG(LuauInferInNoCheckMode)
 LUAU_FASTFLAG(LuauNoMoreGlobalSingletonTypes)
 LUAU_FASTFLAGVARIABLE(LuauKnowsTheDataModel3, false)
-LUAU_FASTFLAGVARIABLE(LuauAutocompleteDynamicLimits, false)
 LUAU_FASTINTVARIABLE(LuauAutocompleteCheckTimeoutMs, 100)
 LUAU_FASTFLAGVARIABLE(DebugLuauDeferredConstraintResolution, false)
 LUAU_FASTFLAG(DebugLuauLogSolverToJson);
@@ -489,23 +489,19 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
             else
                 typeCheckerForAutocomplete.finishTime = std::nullopt;
 
-            if (FFlag::LuauAutocompleteDynamicLimits)
+            // TODO: This is a dirty ad hoc solution for autocomplete timeouts
-            {
+            // We are trying to dynamically adjust our existing limits to lower total typechecking time under the limit
-                // TODO: This is a dirty ad hoc solution for autocomplete timeouts
+            // so that we'll have type information for the whole file at lower quality instead of a full abort in the middle
-                // We are trying to dynamically adjust our existing limits to lower total typechecking time under the limit
+            if (FInt::LuauTarjanChildLimit > 0)
-                // so that we'll have type information for the whole file at lower quality instead of a full abort in the middle
+                typeCheckerForAutocomplete.instantiationChildLimit = std::max(1, int(FInt::LuauTarjanChildLimit * sourceNode.autocompleteLimitsMult));
-                if (FInt::LuauTarjanChildLimit > 0)
+            else
-                    typeCheckerForAutocomplete.instantiationChildLimit =
+                typeCheckerForAutocomplete.instantiationChildLimit = std::nullopt;
-                        std::max(1, int(FInt::LuauTarjanChildLimit * sourceNode.autocompleteLimitsMult));
-                else
-                    typeCheckerForAutocomplete.instantiationChildLimit = std::nullopt;
 
-                if (FInt::LuauTypeInferIterationLimit > 0)
+            if (FInt::LuauTypeInferIterationLimit > 0)
-                    typeCheckerForAutocomplete.unifierIterationLimit =
+                typeCheckerForAutocomplete.unifierIterationLimit =
-                        std::max(1, int(FInt::LuauTypeInferIterationLimit * sourceNode.autocompleteLimitsMult));
+                    std::max(1, int(FInt::LuauTypeInferIterationLimit * sourceNode.autocompleteLimitsMult));
-                else
+            else
-                    typeCheckerForAutocomplete.unifierIterationLimit = std::nullopt;
+                typeCheckerForAutocomplete.unifierIterationLimit = std::nullopt;
-            }
 
             ModulePtr moduleForAutocomplete = FFlag::DebugLuauDeferredConstraintResolution
                                                   ? check(sourceModule, mode, environmentScope, requireCycles, /*forAutocomplete*/ true)
@@ -519,10 +515,9 @@ CheckResult Frontend::check(const ModuleName& name, std::optional<FrontendOption
             {
                 checkResult.timeoutHits.push_back(moduleName);
 
-                if (FFlag::LuauAutocompleteDynamicLimits)
+                sourceNode.autocompleteLimitsMult = sourceNode.autocompleteLimitsMult / 2.0;
-                    sourceNode.autocompleteLimitsMult = sourceNode.autocompleteLimitsMult / 2.0;
             }
-            else if (FFlag::LuauAutocompleteDynamicLimits && duration < autocompleteTimeLimit / 2.0)
+            else if (duration < autocompleteTimeLimit / 2.0)
             {
                 sourceNode.autocompleteLimitsMult = std::min(sourceNode.autocompleteLimitsMult * 2.0, 1.0);
             }
@@ -871,13 +866,25 @@ ModulePtr Frontend::check(
         }
     }
 
+    DataFlowGraph dfg = DataFlowGraphBuilder::build(sourceModule.root, NotNull{&iceHandler});
+
     const NotNull<ModuleResolver> mr{forAutocomplete ? &moduleResolverForAutocomplete : &moduleResolver};
     const ScopePtr& globalScope{forAutocomplete ? typeCheckerForAutocomplete.globalScope : typeChecker.globalScope};
 
     Normalizer normalizer{&result->internalTypes, singletonTypes, NotNull{&typeChecker.unifierState}};
 
     ConstraintGraphBuilder cgb{
-        sourceModule.name, result, &result->internalTypes, mr, singletonTypes, NotNull(&iceHandler), globalScope, logger.get()};
+        sourceModule.name,
+        result,
+        &result->internalTypes,
+        mr,
+        singletonTypes,
+        NotNull(&iceHandler),
+        globalScope,
+        logger.get(),
+        NotNull{&dfg},
+    };
+
     cgb.visit(sourceModule.root);
     result->errors = std::move(cgb.errors);
 

Analysis/src/Module.cpp

@@ -60,36 +60,6 @@ bool isWithinComment(const SourceModule& sourceModule, Position pos)
     return contains(pos, *iter);
 }
 
-struct ForceNormal : TypeVarOnceVisitor
-{
-    const TypeArena* typeArena = nullptr;
-
-    ForceNormal(const TypeArena* typeArena)
-        : typeArena(typeArena)
-    {
-    }
-
-    bool visit(TypeId ty) override
-    {
-        if (ty->owningArena != typeArena)
-            return false;
-
-        asMutable(ty)->normal = true;
-        return true;
-    }
-
-    bool visit(TypeId ty, const FreeTypeVar& ftv) override
-    {
-        visit(ty);
-        return true;
-    }
-
-    bool visit(TypePackId tp, const FreeTypePack& ftp) override
-    {
-        return true;
-    }
-};
-
 struct ClonePublicInterface : Substitution
 {
     NotNull<SingletonTypes> singletonTypes;
@@ -241,8 +211,6 @@ void Module::clonePublicInterface(NotNull<SingletonTypes> singletonTypes, Intern
         moduleScope->varargPack = varargPack;
     }
 
-    ForceNormal forceNormal{&interfaceTypes};
-
     if (exportedTypeBindings)
     {
         for (auto& [name, tf] : *exportedTypeBindings)
@@ -262,7 +230,6 @@ void Module::clonePublicInterface(NotNull<SingletonTypes> singletonTypes, Intern
             {
                 auto t = asMutable(ty);
                 t->ty = AnyTypeVar{};
-                t->normal = true;
             }
         }
     }

Analysis/src/Normalize.cpp

@@ -16,11 +16,11 @@ LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant, false)
 // This could theoretically be 2000 on amd64, but x86 requires this.
 LUAU_FASTINTVARIABLE(LuauNormalizeIterationLimit, 1200);
 LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
-LUAU_FASTINT(LuauTypeInferRecursionLimit);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeCombineTableFix, false);
 LUAU_FASTFLAGVARIABLE(LuauTypeNormalization2, false);
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+LUAU_FASTFLAG(LuauOverloadedFunctionSubtypingPerf);
 
 namespace Luau
 {
@@ -1269,19 +1269,35 @@ std::optional<TypeId> Normalizer::intersectionOfFunctions(TypeId here, TypeId th
         return std::nullopt;
     if (hftv->genericPacks != tftv->genericPacks)
         return std::nullopt;
-    if (hftv->retTypes != tftv->retTypes)
+
+    TypePackId argTypes;
+    TypePackId retTypes;
+    
+    if (hftv->retTypes == tftv->retTypes)
+    {
+        std::optional<TypePackId> argTypesOpt = unionOfTypePacks(hftv->argTypes, tftv->argTypes);
+        if (!argTypesOpt)
+            return std::nullopt;
+        argTypes = *argTypesOpt;
+        retTypes = hftv->retTypes;
+    }
+    else if (FFlag::LuauOverloadedFunctionSubtypingPerf && hftv->argTypes == tftv->argTypes) 
+    {
+        std::optional<TypePackId> retTypesOpt = intersectionOfTypePacks(hftv->argTypes, tftv->argTypes);
+        if (!retTypesOpt)
+            return std::nullopt;
+        argTypes = hftv->argTypes;
+        retTypes = *retTypesOpt;
+    }
+    else
         return std::nullopt;
 
-    std::optional<TypePackId> argTypes = unionOfTypePacks(hftv->argTypes, tftv->argTypes);
+    if (argTypes == hftv->argTypes && retTypes == hftv->retTypes)
-    if (!argTypes)
-        return std::nullopt;
-
-    if (*argTypes == hftv->argTypes)
         return here;
-    if (*argTypes == tftv->argTypes)
+    if (argTypes == tftv->argTypes && retTypes == tftv->retTypes)
         return there;
 
-    FunctionTypeVar result{*argTypes, hftv->retTypes};
+    FunctionTypeVar result{argTypes, retTypes};
     result.generics = hftv->generics;
     result.genericPacks = hftv->genericPacks;
     return arena->addType(std::move(result));
@@ -1762,610 +1778,4 @@ bool isSubtype(
     return ok;
 }
 
-template<typename T>
-static bool areNormal_(const T& t, const std::unordered_set<void*>& seen, InternalErrorReporter& ice)
-{
-    int count = 0;
-    auto isNormal = [&](TypeId ty) {
-        ++count;
-        if (count >= FInt::LuauNormalizeIterationLimit)
-            ice.ice("Luau::areNormal hit iteration limit");
-
-        return ty->normal;
-    };
-
-    return std::all_of(begin(t), end(t), isNormal);
-}
-
-static bool areNormal(const std::vector<TypeId>& types, const std::unordered_set<void*>& seen, InternalErrorReporter& ice)
-{
-    return areNormal_(types, seen, ice);
-}
-
-static bool areNormal(TypePackId tp, const std::unordered_set<void*>& seen, InternalErrorReporter& ice)
-{
-    tp = follow(tp);
-    if (get<FreeTypePack>(tp))
-        return false;
-
-    auto [head, tail] = flatten(tp);
-
-    if (!areNormal_(head, seen, ice))
-        return false;
-
-    if (!tail)
-        return true;
-
-    if (auto vtp = get<VariadicTypePack>(*tail))
-        return vtp->ty->normal || follow(vtp->ty)->normal || seen.find(asMutable(vtp->ty)) != seen.end();
-
-    return true;
-}
-
-#define CHECK_ITERATION_LIMIT(...) \
-    do \
-    { \
-        if (iterationLimit > FInt::LuauNormalizeIterationLimit) \
-        { \
-            limitExceeded = true; \
-            return __VA_ARGS__; \
-        } \
-        ++iterationLimit; \
-    } while (false)
-
-struct Normalize final : TypeVarVisitor
-{
-    using TypeVarVisitor::Set;
-
-    Normalize(TypeArena& arena, NotNull<Scope> scope, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-        : arena(arena)
-        , scope(scope)
-        , singletonTypes(singletonTypes)
-        , ice(ice)
-    {
-    }
-
-    TypeArena& arena;
-    NotNull<Scope> scope;
-    NotNull<SingletonTypes> singletonTypes;
-    InternalErrorReporter& ice;
-
-    int iterationLimit = 0;
-    bool limitExceeded = false;
-
-    bool visit(TypeId ty, const FreeTypeVar&) override
-    {
-        LUAU_ASSERT(!ty->normal);
-        return false;
-    }
-
-    bool visit(TypeId ty, const BoundTypeVar& btv) override
-    {
-        // A type could be considered normal when it is in the stack, but we will eventually find out it is not normal as normalization progresses.
-        // So we need to avoid eagerly saying that this bound type is normal if the thing it is bound to is in the stack.
-        if (seen.find(asMutable(btv.boundTo)) != seen.end())
-            return false;
-
-        // It should never be the case that this TypeVar is normal, but is bound to a non-normal type, except in nontrivial cases.
-        LUAU_ASSERT(!ty->normal || ty->normal == btv.boundTo->normal);
-
-        if (!ty->normal)
-            asMutable(ty)->normal = btv.boundTo->normal;
-        return !ty->normal;
-    }
-
-    bool visit(TypeId ty, const PrimitiveTypeVar&) override
-    {
-        LUAU_ASSERT(ty->normal);
-        return false;
-    }
-
-    bool visit(TypeId ty, const GenericTypeVar&) override
-    {
-        if (!ty->normal)
-            asMutable(ty)->normal = true;
-        return false;
-    }
-
-    bool visit(TypeId ty, const ErrorTypeVar&) override
-    {
-        if (!ty->normal)
-            asMutable(ty)->normal = true;
-        return false;
-    }
-
-    bool visit(TypeId ty, const UnknownTypeVar&) override
-    {
-        if (!ty->normal)
-            asMutable(ty)->normal = true;
-        return false;
-    }
-
-    bool visit(TypeId ty, const NeverTypeVar&) override
-    {
-        if (!ty->normal)
-            asMutable(ty)->normal = true;
-        return false;
-    }
-
-    bool visit(TypeId ty, const ConstrainedTypeVar& ctvRef) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-        LUAU_ASSERT(!ty->normal);
-
-        ConstrainedTypeVar* ctv = const_cast<ConstrainedTypeVar*>(&ctvRef);
-
-        std::vector<TypeId> parts = std::move(ctv->parts);
-
-        // We might transmute, so it's not safe to rely on the builtin traversal logic of visitTypeVar
-        for (TypeId part : parts)
-            traverse(part);
-
-        std::vector<TypeId> newParts = normalizeUnion(parts);
-        ctv->parts = std::move(newParts);
-
-        return false;
-    }
-
-    bool visit(TypeId ty, const FunctionTypeVar& ftv) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-
-        if (ty->normal)
-            return false;
-
-        traverse(ftv.argTypes);
-        traverse(ftv.retTypes);
-
-        asMutable(ty)->normal = areNormal(ftv.argTypes, seen, ice) && areNormal(ftv.retTypes, seen, ice);
-
-        return false;
-    }
-
-    bool visit(TypeId ty, const TableTypeVar& ttv) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-
-        if (ty->normal)
-            return false;
-
-        bool normal = true;
-
-        auto checkNormal = [&](TypeId t) {
-            // if t is on the stack, it is possible that this type is normal.
-            // If t is not normal and it is not on the stack, this type is definitely not normal.
-            if (!t->normal && seen.find(asMutable(t)) == seen.end())
-                normal = false;
-        };
-
-        if (ttv.boundTo)
-        {
-            traverse(*ttv.boundTo);
-            asMutable(ty)->normal = (*ttv.boundTo)->normal;
-            return false;
-        }
-
-        for (const auto& [_name, prop] : ttv.props)
-        {
-            traverse(prop.type);
-            checkNormal(prop.type);
-        }
-
-        if (ttv.indexer)
-        {
-            traverse(ttv.indexer->indexType);
-            checkNormal(ttv.indexer->indexType);
-            traverse(ttv.indexer->indexResultType);
-            checkNormal(ttv.indexer->indexResultType);
-        }
-
-        // An unsealed table can never be normal, ditto for free tables iff the type it is bound to is also not normal.
-        if (ttv.state == TableState::Generic || ttv.state == TableState::Sealed || (ttv.state == TableState::Free && follow(ty)->normal))
-            asMutable(ty)->normal = normal;
-
-        return false;
-    }
-
-    bool visit(TypeId ty, const MetatableTypeVar& mtv) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-
-        if (ty->normal)
-            return false;
-
-        traverse(mtv.table);
-        traverse(mtv.metatable);
-
-        asMutable(ty)->normal = mtv.table->normal && mtv.metatable->normal;
-
-        return false;
-    }
-
-    bool visit(TypeId ty, const ClassTypeVar& ctv) override
-    {
-        if (!ty->normal)
-            asMutable(ty)->normal = true;
-        return false;
-    }
-
-    bool visit(TypeId ty, const AnyTypeVar&) override
-    {
-        LUAU_ASSERT(ty->normal);
-        return false;
-    }
-
-    bool visit(TypeId ty, const UnionTypeVar& utvRef) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-
-        if (ty->normal)
-            return false;
-
-        UnionTypeVar* utv = &const_cast<UnionTypeVar&>(utvRef);
-
-        // We might transmute, so it's not safe to rely on the builtin traversal logic of visitTypeVar
-        for (TypeId option : utv->options)
-            traverse(option);
-
-        std::vector<TypeId> newOptions = normalizeUnion(utv->options);
-
-        const bool normal = areNormal(newOptions, seen, ice);
-
-        LUAU_ASSERT(!newOptions.empty());
-
-        if (newOptions.size() == 1)
-            *asMutable(ty) = BoundTypeVar{newOptions[0]};
-        else
-            utv->options = std::move(newOptions);
-
-        asMutable(ty)->normal = normal;
-
-        return false;
-    }
-
-    bool visit(TypeId ty, const IntersectionTypeVar& itvRef) override
-    {
-        CHECK_ITERATION_LIMIT(false);
-
-        if (ty->normal)
-            return false;
-
-        IntersectionTypeVar* itv = &const_cast<IntersectionTypeVar&>(itvRef);
-
-        std::vector<TypeId> oldParts = itv->parts;
-        IntersectionTypeVar newIntersection;
-
-        for (TypeId part : oldParts)
-            traverse(part);
-
-        std::vector<TypeId> tables;
-        for (TypeId part : oldParts)
-        {
-            part = follow(part);
-            if (get<TableTypeVar>(part))
-                tables.push_back(part);
-            else
-            {
-                Replacer replacer{&arena, nullptr, nullptr}; // FIXME this is super super WEIRD
-                combineIntoIntersection(replacer, &newIntersection, part);
-            }
-        }
-
-        // Don't allocate a new table if there's just one in the intersection.
-        if (tables.size() == 1)
-            newIntersection.parts.push_back(tables[0]);
-        else if (!tables.empty())
-        {
-            const TableTypeVar* first = get<TableTypeVar>(tables[0]);
-            LUAU_ASSERT(first);
-
-            TypeId newTable = arena.addType(TableTypeVar{first->state, first->level});
-            TableTypeVar* ttv = getMutable<TableTypeVar>(newTable);
-            for (TypeId part : tables)
-            {
-                // Intuition: If combineIntoTable() needs to clone a table, any references to 'part' are cyclic and need
-                // to be rewritten to point at 'newTable' in the clone.
-                Replacer replacer{&arena, part, newTable};
-                combineIntoTable(replacer, ttv, part);
-            }
-
-            newIntersection.parts.push_back(newTable);
-        }
-
-        itv->parts = std::move(newIntersection.parts);
-
-        asMutable(ty)->normal = areNormal(itv->parts, seen, ice);
-
-        if (itv->parts.size() == 1)
-        {
-            TypeId part = itv->parts[0];
-            *asMutable(ty) = BoundTypeVar{part};
-        }
-
-        return false;
-    }
-
-    std::vector<TypeId> normalizeUnion(const std::vector<TypeId>& options)
-    {
-        if (options.size() == 1)
-            return options;
-
-        std::vector<TypeId> result;
-
-        for (TypeId part : options)
-        {
-            // AnyTypeVar always win the battle no matter what we do, so we're done.
-            if (FFlag::LuauUnknownAndNeverType && get<AnyTypeVar>(follow(part)))
-                return {part};
-
-            combineIntoUnion(result, part);
-        }
-
-        return result;
-    }
-
-    void combineIntoUnion(std::vector<TypeId>& result, TypeId ty)
-    {
-        ty = follow(ty);
-        if (auto utv = get<UnionTypeVar>(ty))
-        {
-            for (TypeId t : utv)
-            {
-                // AnyTypeVar always win the battle no matter what we do, so we're done.
-                if (FFlag::LuauUnknownAndNeverType && get<AnyTypeVar>(t))
-                {
-                    result = {t};
-                    return;
-                }
-
-                combineIntoUnion(result, t);
-            }
-
-            return;
-        }
-
-        for (TypeId& part : result)
-        {
-            if (isSubtype(ty, part, scope, singletonTypes, ice))
-                return; // no need to do anything
-            else if (isSubtype(part, ty, scope, singletonTypes, ice))
-            {
-                part = ty; // replace the less general type by the more general one
-                return;
-            }
-        }
-
-        result.push_back(ty);
-    }
-
-    /**
-     * @param replacer knows how to clone a type such that any recursive references point at the new containing type.
-     * @param result is an intersection that is safe for us to mutate in-place.
-     */
-    void combineIntoIntersection(Replacer& replacer, IntersectionTypeVar* result, TypeId ty)
-    {
-        // Note: this check guards against running out of stack space
-        // so if you increase the size of a stack frame, you'll need to decrease the limit.
-        CHECK_ITERATION_LIMIT();
-
-        ty = follow(ty);
-        if (auto itv = get<IntersectionTypeVar>(ty))
-        {
-            for (TypeId part : itv->parts)
-                combineIntoIntersection(replacer, result, part);
-            return;
-        }
-
-        // Let's say that the last part of our result intersection is always a table, if any table is part of this intersection
-        if (get<TableTypeVar>(ty))
-        {
-            if (result->parts.empty())
-                result->parts.push_back(arena.addType(TableTypeVar{TableState::Sealed, TypeLevel{}}));
-
-            TypeId theTable = result->parts.back();
-
-            if (!get<TableTypeVar>(follow(theTable)))
-            {
-                result->parts.push_back(arena.addType(TableTypeVar{TableState::Sealed, TypeLevel{}}));
-                theTable = result->parts.back();
-            }
-
-            TypeId newTable = replacer.smartClone(theTable);
-            result->parts.back() = newTable;
-
-            combineIntoTable(replacer, getMutable<TableTypeVar>(newTable), ty);
-        }
-        else if (auto ftv = get<FunctionTypeVar>(ty))
-        {
-            bool merged = false;
-            for (TypeId& part : result->parts)
-            {
-                if (isSubtype(part, ty, scope, singletonTypes, ice))
-                {
-                    merged = true;
-                    break; // no need to do anything
-                }
-                else if (isSubtype(ty, part, scope, singletonTypes, ice))
-                {
-                    merged = true;
-                    part = ty; // replace the less general type by the more general one
-                    break;
-                }
-            }
-
-            if (!merged)
-                result->parts.push_back(ty);
-        }
-        else
-            result->parts.push_back(ty);
-    }
-
-    TableState combineTableStates(TableState lhs, TableState rhs)
-    {
-        if (lhs == rhs)
-            return lhs;
-
-        if (lhs == TableState::Free || rhs == TableState::Free)
-            return TableState::Free;
-
-        if (lhs == TableState::Unsealed || rhs == TableState::Unsealed)
-            return TableState::Unsealed;
-
-        return lhs;
-    }
-
-    /**
-     * @param replacer gives us a way to clone a type such that recursive references are rewritten to the new
-     * "containing" type.
-     * @param table always points into a table that is safe for us to mutate.
-     */
-    void combineIntoTable(Replacer& replacer, TableTypeVar* table, TypeId ty)
-    {
-        // Note: this check guards against running out of stack space
-        // so if you increase the size of a stack frame, you'll need to decrease the limit.
-        CHECK_ITERATION_LIMIT();
-
-        LUAU_ASSERT(table);
-
-        ty = follow(ty);
-
-        TableTypeVar* tyTable = getMutable<TableTypeVar>(ty);
-        LUAU_ASSERT(tyTable);
-
-        for (const auto& [propName, prop] : tyTable->props)
-        {
-            if (auto it = table->props.find(propName); it != table->props.end())
-            {
-                /**
-                 * If we are going to recursively merge intersections of tables, we need to ensure that we never mutate
-                 * a table that comes from somewhere else in the type graph.
-                 *
-                 * smarClone() does some nice things for us: It will perform a clone that is as shallow as possible
-                 * while still rewriting any cyclic references back to the new 'root' table.
-                 *
-                 * replacer also keeps a mapping of types that have previously been copied, so we have the added
-                 * advantage here of knowing that, whether or not a new copy was actually made, the resulting TypeVar is
-                 * safe for us to mutate in-place.
-                 */
-                TypeId clone = replacer.smartClone(it->second.type);
-                it->second.type = combine(replacer, clone, prop.type);
-            }
-            else
-                table->props.insert({propName, prop});
-        }
-
-        if (tyTable->indexer)
-        {
-            if (table->indexer)
-            {
-                table->indexer->indexType = combine(replacer, replacer.smartClone(tyTable->indexer->indexType), table->indexer->indexType);
-                table->indexer->indexResultType =
-                    combine(replacer, replacer.smartClone(tyTable->indexer->indexResultType), table->indexer->indexResultType);
-            }
-            else
-            {
-                table->indexer =
-                    TableIndexer{replacer.smartClone(tyTable->indexer->indexType), replacer.smartClone(tyTable->indexer->indexResultType)};
-            }
-        }
-
-        table->state = combineTableStates(table->state, tyTable->state);
-        table->level = max(table->level, tyTable->level);
-    }
-
-    /**
-     * @param a is always cloned by the caller.  It is safe to mutate in-place.
-     * @param b will never be mutated.
-     */
-    TypeId combine(Replacer& replacer, TypeId a, TypeId b)
-    {
-        b = follow(b);
-
-        if (FFlag::LuauNormalizeCombineTableFix && a == b)
-            return a;
-
-        if (!get<IntersectionTypeVar>(a) && !get<TableTypeVar>(a))
-        {
-            if (!FFlag::LuauNormalizeCombineTableFix && a == b)
-                return a;
-            else
-                return arena.addType(IntersectionTypeVar{{a, b}});
-        }
-
-        if (auto itv = getMutable<IntersectionTypeVar>(a))
-        {
-            combineIntoIntersection(replacer, itv, b);
-            return a;
-        }
-        else if (auto ttv = getMutable<TableTypeVar>(a))
-        {
-            if (FFlag::LuauNormalizeCombineTableFix && !get<TableTypeVar>(b))
-                return arena.addType(IntersectionTypeVar{{a, b}});
-            combineIntoTable(replacer, ttv, b);
-            return a;
-        }
-
-        LUAU_ASSERT(!"Impossible");
-        LUAU_UNREACHABLE();
-    }
-};
-
-#undef CHECK_ITERATION_LIMIT
-
-/**
- * @returns A tuple of TypeId and a success indicator. (true indicates that the normalization completed successfully)
- */
-std::pair<TypeId, bool> normalize(
-    TypeId ty, NotNull<Scope> scope, TypeArena& arena, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    CloneState state;
-    if (FFlag::DebugLuauCopyBeforeNormalizing)
-        (void)clone(ty, arena, state);
-
-    Normalize n{arena, scope, singletonTypes, ice};
-    n.traverse(ty);
-
-    return {ty, !n.limitExceeded};
-}
-
-// TODO: Think about using a temporary arena and cloning types out of it so that we
-// reclaim memory used by wantonly allocated intermediate types here.
-// The main wrinkle here is that we don't want clone() to copy a type if the source and dest
-// arena are the same.
-std::pair<TypeId, bool> normalize(TypeId ty, NotNull<Module> module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    return normalize(ty, NotNull{module->getModuleScope().get()}, module->internalTypes, singletonTypes, ice);
-}
-
-std::pair<TypeId, bool> normalize(TypeId ty, const ModulePtr& module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    return normalize(ty, NotNull{module.get()}, singletonTypes, ice);
-}
-
-/**
- * @returns A tuple of TypeId and a success indicator. (true indicates that the normalization completed successfully)
- */
-std::pair<TypePackId, bool> normalize(
-    TypePackId tp, NotNull<Scope> scope, TypeArena& arena, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    CloneState state;
-    if (FFlag::DebugLuauCopyBeforeNormalizing)
-        (void)clone(tp, arena, state);
-
-    Normalize n{arena, scope, singletonTypes, ice};
-    n.traverse(tp);
-
-    return {tp, !n.limitExceeded};
-}
-
-std::pair<TypePackId, bool> normalize(TypePackId tp, NotNull<Module> module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    return normalize(tp, NotNull{module->getModuleScope().get()}, module->internalTypes, singletonTypes, ice);
-}
-
-std::pair<TypePackId, bool> normalize(TypePackId tp, const ModulePtr& module, NotNull<SingletonTypes> singletonTypes, InternalErrorReporter& ice)
-{
-    return normalize(tp, NotNull{module.get()}, singletonTypes, ice);
-}
-
 } // namespace Luau

Analysis/src/Quantify.cpp

@@ -57,29 +57,6 @@ struct Quantifier final : TypeVarOnceVisitor
         return false;
     }
 
-    bool visit(TypeId ty, const ConstrainedTypeVar&) override
-    {
-        ConstrainedTypeVar* ctv = getMutable<ConstrainedTypeVar>(ty);
-
-        seenMutableType = true;
-
-        if (!level.subsumes(ctv->level))
-            return false;
-
-        std::vector<TypeId> opts = std::move(ctv->parts);
-
-        // We might transmute, so it's not safe to rely on the builtin traversal logic
-        for (TypeId opt : opts)
-            traverse(opt);
-
-        if (opts.size() == 1)
-            *asMutable(ty) = BoundTypeVar{opts[0]};
-        else
-            *asMutable(ty) = UnionTypeVar{std::move(opts)};
-
-        return false;
-    }
-
     bool visit(TypeId ty, const TableTypeVar&) override
     {
         LUAU_ASSERT(getMutable<TableTypeVar>(ty));

Analysis/src/Scope.cpp

@@ -27,6 +27,44 @@ void Scope::addBuiltinTypeBinding(const Name& name, const TypeFun& tyFun)
     builtinTypeNames.insert(name);
 }
 
+std::optional<TypeId> Scope::lookup(Symbol sym) const
+{
+    auto r = const_cast<Scope*>(this)->lookupEx(sym);
+    if (r)
+        return r->first;
+    else
+        return std::nullopt;
+}
+
+std::optional<std::pair<TypeId, Scope*>> Scope::lookupEx(Symbol sym)
+{
+    Scope* s = this;
+
+    while (true)
+    {
+        auto it = s->bindings.find(sym);
+        if (it != s->bindings.end())
+            return std::pair{it->second.typeId, s};
+
+        if (s->parent)
+            s = s->parent.get();
+        else
+            return std::nullopt;
+    }
+}
+
+// TODO: We might kill Scope::lookup(Symbol) once data flow is fully fleshed out with type states and control flow analysis.
+std::optional<TypeId> Scope::lookup(DefId def) const
+{
+    for (const Scope* current = this; current; current = current->parent.get())
+    {
+        if (auto ty = current->dcrRefinements.find(def))
+            return *ty;
+    }
+
+    return std::nullopt;
+}
+
 std::optional<TypeFun> Scope::lookupType(const Name& name)
 {
     const Scope* scope = this;
@@ -111,23 +149,6 @@ std::optional<Binding> Scope::linearSearchForBinding(const std::string& name, bo
     return std::nullopt;
 }
 
-std::optional<TypeId> Scope::lookup(Symbol sym)
-{
-    Scope* s = this;
-
-    while (true)
-    {
-        auto it = s->bindings.find(sym);
-        if (it != s->bindings.end())
-            return it->second.typeId;
-
-        if (s->parent)
-            s = s->parent.get();
-        else
-            return std::nullopt;
-    }
-}
-
 bool subsumesStrict(Scope* left, Scope* right)
 {
     while (right)

Analysis/src/Substitution.cpp

@@ -73,11 +73,6 @@ void Tarjan::visitChildren(TypeId ty, int index)
         for (TypeId part : itv->parts)
             visitChild(part);
     }
-    else if (const ConstrainedTypeVar* ctv = get<ConstrainedTypeVar>(ty))
-    {
-        for (TypeId part : ctv->parts)
-            visitChild(part);
-    }
     else if (const PendingExpansionTypeVar* petv = get<PendingExpansionTypeVar>(ty))
     {
         for (TypeId a : petv->typeArguments)
@@ -97,6 +92,10 @@ void Tarjan::visitChildren(TypeId ty, int index)
         if (ctv->metatable)
             visitChild(*ctv->metatable);
     }
+    else if (const NegationTypeVar* ntv = get<NegationTypeVar>(ty))
+    {
+        visitChild(ntv->ty);
+    }
 }
 
 void Tarjan::visitChildren(TypePackId tp, int index)
@@ -605,11 +604,6 @@ void Substitution::replaceChildren(TypeId ty)
         for (TypeId& part : itv->parts)
             part = replace(part);
     }
-    else if (ConstrainedTypeVar* ctv = getMutable<ConstrainedTypeVar>(ty))
-    {
-        for (TypeId& part : ctv->parts)
-            part = replace(part);
-    }
     else if (PendingExpansionTypeVar* petv = getMutable<PendingExpansionTypeVar>(ty))
     {
         for (TypeId& a : petv->typeArguments)
@@ -629,6 +623,10 @@ void Substitution::replaceChildren(TypeId ty)
         if (ctv->metatable)
             ctv->metatable = replace(*ctv->metatable);
     }
+    else if (NegationTypeVar* ntv = getMutable<NegationTypeVar>(ty))
+    {
+        ntv->ty = replace(ntv->ty);
+    }
 }
 
 void Substitution::replaceChildren(TypePackId tp)

Analysis/src/ToDot.cpp

@@ -237,15 +237,6 @@ void StateDot::visitChildren(TypeId ty, int index)
         finishNodeLabel(ty);
         finishNode();
     }
-    else if (const ConstrainedTypeVar* ctv = get<ConstrainedTypeVar>(ty))
-    {
-        formatAppend(result, "ConstrainedTypeVar %d", index);
-        finishNodeLabel(ty);
-        finishNode();
-
-        for (TypeId part : ctv->parts)
-            visitChild(part, index);
-    }
     else if (get<ErrorTypeVar>(ty))
     {
         formatAppend(result, "ErrorTypeVar %d", index);

Analysis/src/ToString.cpp

@@ -400,29 +400,6 @@ struct TypeVarStringifier
             state.emit(state.getName(ty));
     }
 
-    void operator()(TypeId, const ConstrainedTypeVar& ctv)
-    {
-        state.result.invalid = true;
-
-        state.emit("[");
-        if (FFlag::DebugLuauVerboseTypeNames)
-            state.emit(ctv.level);
-        state.emit("[");
-
-        bool first = true;
-        for (TypeId ty : ctv.parts)
-        {
-            if (first)
-                first = false;
-            else
-                state.emit("|");
-
-            stringify(ty);
-        }
-
-        state.emit("]]");
-    }
-
     void operator()(TypeId, const BlockedTypeVar& btv)
     {
         state.emit("*blocked-");
@@ -871,6 +848,28 @@ struct TypeVarStringifier
     {
         state.emit("never");
     }
+
+    void operator()(TypeId ty, const UseTypeVar&)
+    {
+        stringify(follow(ty));
+    }
+
+    void operator()(TypeId, const NegationTypeVar& ntv)
+    {
+        state.emit("~");
+
+        // The precedence of `~` should be less than `|` and `&`.
+        TypeId followed = follow(ntv.ty);
+        bool parens = get<UnionTypeVar>(followed) || get<IntersectionTypeVar>(followed);
+
+        if (parens)
+            state.emit("(");
+
+        stringify(ntv.ty);
+
+        if (parens)
+            state.emit(")");
+    }
 };
 
 struct TypePackStringifier
@@ -1442,7 +1441,7 @@ std::string generateName(size_t i)
 
 std::string toString(const Constraint& constraint, ToStringOptions& opts)
 {
-    auto go = [&opts](auto&& c) {
+    auto go = [&opts](auto&& c) -> std::string {
         using T = std::decay_t<decltype(c)>;
 
         // TODO: Inline and delete this function when clipping FFlag::LuauFixNameMaps
@@ -1526,6 +1525,10 @@ 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>)
+        {
+            return "TODO";
+        }
         else
             static_assert(always_false_v<T>, "Non-exhaustive constraint switch");
     };

Analysis/src/TxnLog.cpp

@@ -251,7 +251,7 @@ PendingType* TxnLog::bindTable(TypeId ty, std::optional<TypeId> newBoundTo)
 
 PendingType* TxnLog::changeLevel(TypeId ty, TypeLevel newLevel)
 {
-    LUAU_ASSERT(get<FreeTypeVar>(ty) || get<TableTypeVar>(ty) || get<FunctionTypeVar>(ty) || get<ConstrainedTypeVar>(ty));
+    LUAU_ASSERT(get<FreeTypeVar>(ty) || get<TableTypeVar>(ty) || get<FunctionTypeVar>(ty));
 
     PendingType* newTy = queue(ty);
     if (FreeTypeVar* ftv = Luau::getMutable<FreeTypeVar>(newTy))
@@ -267,11 +267,6 @@ PendingType* TxnLog::changeLevel(TypeId ty, TypeLevel newLevel)
     {
         ftv->level = newLevel;
     }
-    else if (ConstrainedTypeVar* ctv = Luau::getMutable<ConstrainedTypeVar>(newTy))
-    {
-        if (FFlag::LuauUnknownAndNeverType)
-            ctv->level = newLevel;
-    }
 
     return newTy;
 }
@@ -291,7 +286,7 @@ PendingTypePack* TxnLog::changeLevel(TypePackId tp, TypeLevel newLevel)
 
 PendingType* TxnLog::changeScope(TypeId ty, NotNull<Scope> newScope)
 {
-    LUAU_ASSERT(get<FreeTypeVar>(ty) || get<TableTypeVar>(ty) || get<FunctionTypeVar>(ty) || get<ConstrainedTypeVar>(ty));
+    LUAU_ASSERT(get<FreeTypeVar>(ty) || get<TableTypeVar>(ty) || get<FunctionTypeVar>(ty));
 
     PendingType* newTy = queue(ty);
     if (FreeTypeVar* ftv = Luau::getMutable<FreeTypeVar>(newTy))
@@ -307,10 +302,6 @@ PendingType* TxnLog::changeScope(TypeId ty, NotNull<Scope> newScope)
     {
         ftv->scope = newScope;
     }
-    else if (ConstrainedTypeVar* ctv = Luau::getMutable<ConstrainedTypeVar>(newTy))
-    {
-        ctv->scope = newScope;
-    }
 
     return newTy;
 }

Analysis/src/TypeAttach.cpp

@@ -104,16 +104,6 @@ public:
         return allocator->alloc<AstTypeReference>(Location(), std::nullopt, AstName("*pending-expansion*"));
     }
 
-    AstType* operator()(const ConstrainedTypeVar& ctv)
-    {
-        AstArray<AstType*> types;
-        types.size = ctv.parts.size();
-        types.data = static_cast<AstType**>(allocator->allocate(sizeof(AstType*) * ctv.parts.size()));
-        for (size_t i = 0; i < ctv.parts.size(); ++i)
-            types.data[i] = Luau::visit(*this, ctv.parts[i]->ty);
-        return allocator->alloc<AstTypeIntersection>(Location(), types);
-    }
-
     AstType* operator()(const SingletonTypeVar& stv)
     {
         if (const BooleanSingleton* bs = get<BooleanSingleton>(&stv))
@@ -348,6 +338,17 @@ 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
+        throw std::runtime_error("Cannot convert NegationTypeVar into AstNode");
+    }
 
 private:
     Allocator* allocator;

Analysis/src/TypeChecker2.cpp

@@ -5,6 +5,7 @@
 #include "Luau/AstQuery.h"
 #include "Luau/Clone.h"
 #include "Luau/Instantiation.h"
+#include "Luau/Metamethods.h"
 #include "Luau/Normalize.h"
 #include "Luau/ToString.h"
 #include "Luau/TxnLog.h"
@@ -62,6 +63,23 @@ struct StackPusher
     }
 };
 
+static std::optional<std::string> getIdentifierOfBaseVar(AstExpr* node)
+{
+    if (AstExprGlobal* expr = node->as<AstExprGlobal>())
+        return expr->name.value;
+
+    if (AstExprLocal* expr = node->as<AstExprLocal>())
+        return expr->local->name.value;
+
+    if (AstExprIndexExpr* expr = node->as<AstExprIndexExpr>())
+        return getIdentifierOfBaseVar(expr->expr);
+
+    if (AstExprIndexName* expr = node->as<AstExprIndexName>())
+        return getIdentifierOfBaseVar(expr->expr);
+
+    return std::nullopt;
+}
+
 struct TypeChecker2
 {
     NotNull<SingletonTypes> singletonTypes;
@@ -750,7 +768,7 @@ struct TypeChecker2
         TypeId actualType = lookupType(string);
         TypeId stringType = singletonTypes->stringType;
 
-        if (!isSubtype(stringType, actualType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (!isSubtype(actualType, stringType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
         {
             reportError(TypeMismatch{actualType, stringType}, string->location);
         }
@@ -783,26 +801,55 @@ struct TypeChecker2
 
         TypePackId expectedRetType = lookupPack(call);
         TypeId functionType = lookupType(call->func);
-        LUAU_ASSERT(functionType);
+        TypeId testFunctionType = functionType;
+        TypePack args;
 
         if (get<AnyTypeVar>(functionType) || get<ErrorTypeVar>(functionType))
             return;
-
+        else if (std::optional<TypeId> callMm = findMetatableEntry(singletonTypes, module->errors, functionType, "__call", call->func->location))
-        // TODO: Lots of other types are callable: intersections of functions
+        {
-        // and things with the __call metamethod.
+            if (get<FunctionTypeVar>(follow(*callMm)))
-        if (!get<FunctionTypeVar>(functionType))
+            {
+                if (std::optional<TypeId> instantiatedCallMm = instantiation.substitute(*callMm))
+                {
+                    args.head.push_back(functionType);
+                    testFunctionType = follow(*instantiatedCallMm);
+                }
+                else
+                {
+                    reportError(UnificationTooComplex{}, call->func->location);
+                    return;
+                }
+            }
+            else
+            {
+                // TODO: This doesn't flag the __call metamethod as the problem
+                // very clearly.
+                reportError(CannotCallNonFunction{*callMm}, call->func->location);
+                return;
+            }
+        }
+        else if (get<FunctionTypeVar>(functionType))
+        {
+            if (std::optional<TypeId> instantiatedFunctionType = instantiation.substitute(functionType))
+            {
+                testFunctionType = *instantiatedFunctionType;
+            }
+            else
+            {
+                reportError(UnificationTooComplex{}, call->func->location);
+                return;
+            }
+        }
+        else
         {
             reportError(CannotCallNonFunction{functionType}, call->func->location);
             return;
         }
 
-        TypeId instantiatedFunctionType = follow(instantiation.substitute(functionType).value_or(nullptr));
-
-        TypePack args;
         for (AstExpr* arg : call->args)
         {
-            TypeId argTy = module->astTypes[arg];
+            TypeId argTy = lookupType(arg);
-            LUAU_ASSERT(argTy);
             args.head.push_back(argTy);
         }
 
@@ -810,7 +857,7 @@ struct TypeChecker2
         FunctionTypeVar ftv{argsTp, expectedRetType};
         TypeId expectedType = arena.addType(ftv);
 
-        if (!isSubtype(instantiatedFunctionType, expectedType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
+        if (!isSubtype(testFunctionType, expectedType, stack.back(), singletonTypes, ice, /* anyIsTop */ false))
         {
             CloneState cloneState;
             expectedType = clone(expectedType, module->internalTypes, cloneState);
@@ -893,9 +940,204 @@ struct TypeChecker2
 
     void visit(AstExprBinary* expr)
     {
-        // TODO!
         visit(expr->left);
         visit(expr->right);
+
+        NotNull<Scope> scope = stack.back();
+
+        bool isEquality = expr->op == AstExprBinary::Op::CompareEq || expr->op == AstExprBinary::Op::CompareNe;
+        bool isComparison = expr->op >= AstExprBinary::Op::CompareEq && expr->op <= AstExprBinary::Op::CompareGe;
+        bool isLogical = expr->op == AstExprBinary::Op::And || expr->op == AstExprBinary::Op::Or;
+
+        TypeId leftType = lookupType(expr->left);
+        TypeId rightType = lookupType(expr->right);
+
+        if (expr->op == AstExprBinary::Op::Or)
+        {
+            leftType = stripNil(singletonTypes, module->internalTypes, leftType);
+        }
+
+        bool isStringOperation = isString(leftType) && isString(rightType);
+
+        if (get<AnyTypeVar>(leftType) || get<ErrorTypeVar>(leftType) || get<AnyTypeVar>(rightType) || get<ErrorTypeVar>(rightType))
+            return;
+
+        if ((get<BlockedTypeVar>(leftType) || get<FreeTypeVar>(leftType)) && !isEquality && !isLogical)
+        {
+            auto name = getIdentifierOfBaseVar(expr->left);
+            reportError(CannotInferBinaryOperation{expr->op, name,
+                            isComparison ? CannotInferBinaryOperation::OpKind::Comparison : CannotInferBinaryOperation::OpKind::Operation},
+                expr->location);
+            return;
+        }
+
+        if (auto it = kBinaryOpMetamethods.find(expr->op); it != kBinaryOpMetamethods.end())
+        {
+            std::optional<TypeId> leftMt = getMetatable(leftType, singletonTypes);
+            std::optional<TypeId> rightMt = getMetatable(rightType, singletonTypes);
+
+            bool matches = leftMt == rightMt;
+            if (isEquality && !matches)
+            {
+                auto testUnion = [&matches, singletonTypes = this->singletonTypes](const UnionTypeVar* utv, std::optional<TypeId> otherMt) {
+                    for (TypeId option : utv)
+                    {
+                        if (getMetatable(follow(option), singletonTypes) == otherMt)
+                        {
+                            matches = true;
+                            break;
+                        }
+                    }
+                };
+
+                if (const UnionTypeVar* utv = get<UnionTypeVar>(leftType); utv && rightMt)
+                {
+                    testUnion(utv, rightMt);
+                }
+
+                if (const UnionTypeVar* utv = get<UnionTypeVar>(rightType); utv && leftMt && !matches)
+                {
+                    testUnion(utv, leftMt);
+                }
+            }
+
+            if (!matches && isComparison)
+            {
+                reportError(GenericError{format("Types %s and %s cannot be compared with %s because they do not have the same metatable",
+                                toString(leftType).c_str(), toString(rightType).c_str(), toString(expr->op).c_str())},
+                    expr->location);
+
+                return;
+            }
+
+            std::optional<TypeId> mm;
+            if (std::optional<TypeId> leftMm = findMetatableEntry(singletonTypes, module->errors, leftType, it->second, expr->left->location))
+                mm = leftMm;
+            else if (std::optional<TypeId> rightMm = findMetatableEntry(singletonTypes, module->errors, rightType, it->second, expr->right->location))
+                mm = rightMm;
+
+            if (mm)
+            {
+                if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(*mm))
+                {
+                    TypePackId expectedArgs;
+                    // For >= and > we invoke __lt and __le respectively with
+                    // swapped argument ordering.
+                    if (expr->op == AstExprBinary::Op::CompareGe || expr->op == AstExprBinary::Op::CompareGt)
+                    {
+                        expectedArgs = module->internalTypes.addTypePack({rightType, leftType});
+                    }
+                    else
+                    {
+                        expectedArgs = module->internalTypes.addTypePack({leftType, rightType});
+                    }
+
+                    reportErrors(tryUnify(scope, expr->location, ftv->argTypes, expectedArgs));
+
+                    if (expr->op == AstExprBinary::CompareEq || expr->op == AstExprBinary::CompareNe || expr->op == AstExprBinary::CompareGe ||
+                        expr->op == AstExprBinary::CompareGt || expr->op == AstExprBinary::Op::CompareLe || expr->op == AstExprBinary::Op::CompareLt)
+                    {
+                        TypePackId expectedRets = module->internalTypes.addTypePack({singletonTypes->booleanType});
+                        if (!isSubtype(ftv->retTypes, expectedRets, scope, singletonTypes, ice))
+                        {
+                            reportError(GenericError{format("Metamethod '%s' must return type 'boolean'", it->second)}, expr->location);
+                        }
+                    }
+                    else if (!first(ftv->retTypes))
+                    {
+                        reportError(GenericError{format("Metamethod '%s' must return a value", it->second)}, expr->location);
+                    }
+                }
+                else
+                {
+                    reportError(CannotCallNonFunction{*mm}, expr->location);
+                }
+
+                return;
+            }
+            // If this is a string comparison, or a concatenation of strings, we
+            // want to fall through to primitive behavior.
+            else if (!isEquality && !(isStringOperation && (expr->op == AstExprBinary::Op::Concat || isComparison)))
+            {
+                if (leftMt || rightMt)
+                {
+                    if (isComparison)
+                    {
+                        reportError(GenericError{format(
+                                        "Types '%s' and '%s' cannot be compared with %s because neither type's metatable has a '%s' metamethod",
+                                        toString(leftType).c_str(), toString(rightType).c_str(), toString(expr->op).c_str(), it->second)},
+                            expr->location);
+                    }
+                    else
+                    {
+                        reportError(GenericError{format(
+                                        "Operator %s is not applicable for '%s' and '%s' because neither type's metatable has a '%s' metamethod",
+                                        toString(expr->op).c_str(), toString(leftType).c_str(), toString(rightType).c_str(), it->second)},
+                            expr->location);
+                    }
+
+                    return;
+                }
+                else if (!leftMt && !rightMt && (get<TableTypeVar>(leftType) || get<TableTypeVar>(rightType)))
+                {
+                    if (isComparison)
+                    {
+                        reportError(GenericError{format("Types '%s' and '%s' cannot be compared with %s because neither type has a metatable",
+                                        toString(leftType).c_str(), toString(rightType).c_str(), toString(expr->op).c_str())},
+                            expr->location);
+                    }
+                    else
+                    {
+                        reportError(GenericError{format("Operator %s is not applicable for '%s' and '%s' because neither type has a metatable",
+                                        toString(expr->op).c_str(), toString(leftType).c_str(), toString(rightType).c_str())},
+                            expr->location);
+                    }
+
+                    return;
+                }
+            }
+        }
+
+        switch (expr->op)
+        {
+        case AstExprBinary::Op::Add:
+        case AstExprBinary::Op::Sub:
+        case AstExprBinary::Op::Mul:
+        case AstExprBinary::Op::Div:
+        case AstExprBinary::Op::Pow:
+        case AstExprBinary::Op::Mod:
+            reportErrors(tryUnify(scope, expr->left->location, leftType, singletonTypes->numberType));
+            reportErrors(tryUnify(scope, expr->right->location, rightType, singletonTypes->numberType));
+
+            break;
+        case AstExprBinary::Op::Concat:
+            reportErrors(tryUnify(scope, expr->left->location, leftType, singletonTypes->stringType));
+            reportErrors(tryUnify(scope, expr->right->location, rightType, singletonTypes->stringType));
+
+            break;
+        case AstExprBinary::Op::CompareGe:
+        case AstExprBinary::Op::CompareGt:
+        case AstExprBinary::Op::CompareLe:
+        case AstExprBinary::Op::CompareLt:
+            if (isNumber(leftType))
+                reportErrors(tryUnify(scope, expr->right->location, rightType, singletonTypes->numberType));
+            else if (isString(leftType))
+                reportErrors(tryUnify(scope, expr->right->location, rightType, singletonTypes->stringType));
+            else
+                reportError(GenericError{format("Types '%s' and '%s' cannot be compared with relational operator %s", toString(leftType).c_str(),
+                                toString(rightType).c_str(), toString(expr->op).c_str())},
+                    expr->location);
+
+            break;
+        case AstExprBinary::Op::And:
+        case AstExprBinary::Op::Or:
+        case AstExprBinary::Op::CompareEq:
+        case AstExprBinary::Op::CompareNe:
+            break;
+        default:
+            // Unhandled AstExprBinary::Op possibility.
+            LUAU_ASSERT(false);
+        }
     }
 
     void visit(AstExprTypeAssertion* expr)

Analysis/src/TypeInfer.cpp

@@ -31,7 +31,6 @@ LUAU_FASTINTVARIABLE(LuauTypeInferTypePackLoopLimit, 5000)
 LUAU_FASTINTVARIABLE(LuauCheckRecursionLimit, 300)
 LUAU_FASTINTVARIABLE(LuauVisitRecursionLimit, 500)
 LUAU_FASTFLAG(LuauKnowsTheDataModel3)
-LUAU_FASTFLAG(LuauAutocompleteDynamicLimits)
 LUAU_FASTFLAG(LuauTypeNormalization2)
 LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification, false)
 LUAU_FASTFLAGVARIABLE(LuauReturnAnyInsteadOfICE, false) // Eventually removed as false.
@@ -280,11 +279,8 @@ ModulePtr TypeChecker::checkWithoutRecursionCheck(const SourceModule& module, Mo
     iceHandler->moduleName = module.name;
     normalizer.arena = &currentModule->internalTypes;
 
-    if (FFlag::LuauAutocompleteDynamicLimits)
+    unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
-    {
+    unifierState.counters.iterationLimit = unifierIterationLimit ? *unifierIterationLimit : FInt::LuauTypeInferIterationLimit;
-        unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
-        unifierState.counters.iterationLimit = unifierIterationLimit ? *unifierIterationLimit : FInt::LuauTypeInferIterationLimit;
-    }
 
     ScopePtr parentScope = environmentScope.value_or(globalScope);
     ScopePtr moduleScope = std::make_shared<Scope>(parentScope);
@@ -773,16 +769,6 @@ void TypeChecker::check(const ScopePtr& scope, const AstStatRepeat& statement)
     checkExpr(repScope, *statement.condition);
 }
 
-void TypeChecker::unifyLowerBound(TypePackId subTy, TypePackId superTy, TypeLevel demotedLevel, const ScopePtr& scope, const Location& location)
-{
-    Unifier state = mkUnifier(scope, location);
-    state.unifyLowerBound(subTy, superTy, demotedLevel);
-
-    state.log.commit();
-
-    reportErrors(state.errors);
-}
-
 struct Demoter : Substitution
 {
     Demoter(TypeArena* arena)
@@ -2091,39 +2077,6 @@ std::optional<TypeId> TypeChecker::getIndexTypeFromTypeImpl(
     return std::nullopt;
 }
 
-std::vector<TypeId> TypeChecker::reduceUnion(const std::vector<TypeId>& types)
-{
-    std::vector<TypeId> result;
-    for (TypeId t : types)
-    {
-        t = follow(t);
-        if (get<NeverTypeVar>(t))
-            continue;
-
-        if (get<ErrorTypeVar>(t) || get<AnyTypeVar>(t))
-            return {t};
-
-        if (const UnionTypeVar* utv = get<UnionTypeVar>(t))
-        {
-            for (TypeId ty : utv)
-            {
-                ty = follow(ty);
-                if (get<NeverTypeVar>(ty))
-                    continue;
-                if (get<ErrorTypeVar>(ty) || get<AnyTypeVar>(ty))
-                    return {ty};
-
-                if (result.end() == std::find(result.begin(), result.end(), ty))
-                    result.push_back(ty);
-            }
-        }
-        else if (std::find(result.begin(), result.end(), t) == result.end())
-            result.push_back(t);
-    }
-
-    return result;
-}
-
 std::optional<TypeId> TypeChecker::tryStripUnionFromNil(TypeId ty)
 {
     if (const UnionTypeVar* utv = get<UnionTypeVar>(ty))
@@ -4597,7 +4550,7 @@ TypeId TypeChecker::instantiate(const ScopePtr& scope, TypeId ty, Location locat
 
     Instantiation instantiation{log, &currentModule->internalTypes, scope->level, /*scope*/ nullptr};
 
-    if (FFlag::LuauAutocompleteDynamicLimits && instantiationChildLimit)
+    if (instantiationChildLimit)
         instantiation.childLimit = *instantiationChildLimit;
 
     std::optional<TypeId> instantiated = instantiation.substitute(ty);

Analysis/src/TypeUtils.cpp

@@ -6,6 +6,8 @@
 #include "Luau/ToString.h"
 #include "Luau/TypeInfer.h"
 
+#include <algorithm>
+
 namespace Luau
 {
 
@@ -146,18 +148,15 @@ std::optional<TypeId> getIndexTypeFromType(const ScopePtr& scope, ErrorVec& erro
             return std::nullopt;
         }
 
+        goodOptions = reduceUnion(goodOptions);
+
         if (goodOptions.empty())
             return singletonTypes->neverType;
 
         if (goodOptions.size() == 1)
             return goodOptions[0];
 
-        // TODO: inefficient.
+        return arena->addType(UnionTypeVar{std::move(goodOptions)});
-        TypeId result = arena->addType(UnionTypeVar{std::move(goodOptions)});
-        auto [ty, ok] = normalize(result, NotNull{scope.get()}, *arena, singletonTypes, handle);
-        if (!ok && addErrors)
-            errors.push_back(TypeError{location, NormalizationTooComplex{}});
-        return ok ? ty : singletonTypes->anyType;
     }
     else if (const IntersectionTypeVar* itv = get<IntersectionTypeVar>(type))
     {
@@ -264,4 +263,79 @@ std::vector<TypeId> flatten(TypeArena& arena, NotNull<SingletonTypes> singletonT
     return result;
 }
 
+std::vector<TypeId> reduceUnion(const std::vector<TypeId>& types)
+{
+    std::vector<TypeId> result;
+    for (TypeId t : types)
+    {
+        t = follow(t);
+        if (get<NeverTypeVar>(t))
+            continue;
+
+        if (get<ErrorTypeVar>(t) || get<AnyTypeVar>(t))
+            return {t};
+
+        if (const UnionTypeVar* utv = get<UnionTypeVar>(t))
+        {
+            for (TypeId ty : utv)
+            {
+                ty = follow(ty);
+                if (get<NeverTypeVar>(ty))
+                    continue;
+                if (get<ErrorTypeVar>(ty) || get<AnyTypeVar>(ty))
+                    return {ty};
+
+                if (result.end() == std::find(result.begin(), result.end(), ty))
+                    result.push_back(ty);
+            }
+        }
+        else if (std::find(result.begin(), result.end(), t) == result.end())
+            result.push_back(t);
+    }
+
+    return result;
+}
+
+static std::optional<TypeId> tryStripUnionFromNil(TypeArena& arena, TypeId ty)
+{
+    if (const UnionTypeVar* utv = get<UnionTypeVar>(ty))
+    {
+        if (!std::any_of(begin(utv), end(utv), isNil))
+            return ty;
+
+        std::vector<TypeId> result;
+
+        for (TypeId option : utv)
+        {
+            if (!isNil(option))
+                result.push_back(option);
+        }
+
+        if (result.empty())
+            return std::nullopt;
+
+        return result.size() == 1 ? result[0] : arena.addType(UnionTypeVar{std::move(result)});
+    }
+
+    return std::nullopt;
+}
+
+TypeId stripNil(NotNull<SingletonTypes> singletonTypes, TypeArena& arena, TypeId ty)
+{
+    ty = follow(ty);
+
+    if (get<UnionTypeVar>(ty))
+    {
+        std::optional<TypeId> cleaned = tryStripUnionFromNil(arena, ty);
+
+        // If there is no union option without 'nil'
+        if (!cleaned)
+            return singletonTypes->nilType;
+
+        return follow(*cleaned);
+    }
+
+    return follow(ty);
+}
+
 } // namespace Luau

Analysis/src/TypeVar.cpp

@@ -57,6 +57,13 @@ 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)
+                throw std::runtime_error("UseTypeVar must map to another TypeId");
+            return *ty;
+        }
         else
             return std::nullopt;
     };
@@ -760,6 +767,8 @@ SingletonTypes::SingletonTypes()
     , unknownType(arena->addType(TypeVar{UnknownTypeVar{}, /*persistent*/ true}))
     , neverType(arena->addType(TypeVar{NeverTypeVar{}, /*persistent*/ true}))
     , errorType(arena->addType(TypeVar{ErrorTypeVar{}, /*persistent*/ true}))
+    , falsyType(arena->addType(TypeVar{UnionTypeVar{{falseType, nilType}}, /*persistent*/ true}))
+    , truthyType(arena->addType(TypeVar{NegationTypeVar{falsyType}, /*persistent*/ true}))
     , anyTypePack(arena->addTypePack(TypePackVar{VariadicTypePack{anyType}, /*persistent*/ true}))
     , neverTypePack(arena->addTypePack(TypePackVar{VariadicTypePack{neverType}, /*persistent*/ true}))
     , uninhabitableTypePack(arena->addTypePack({neverType}, neverTypePack))
@@ -896,7 +905,6 @@ void persist(TypeId ty)
             continue;
 
         asMutable(t)->persistent = true;
-        asMutable(t)->normal = true; // all persistent types are assumed to be normal
 
         if (auto btv = get<BoundTypeVar>(t))
             queue.push_back(btv->boundTo);
@@ -933,11 +941,6 @@ void persist(TypeId ty)
             for (TypeId opt : itv->parts)
                 queue.push_back(opt);
         }
-        else if (auto ctv = get<ConstrainedTypeVar>(t))
-        {
-            for (TypeId opt : ctv->parts)
-                queue.push_back(opt);
-        }
         else if (auto mtv = get<MetatableTypeVar>(t))
         {
             queue.push_back(mtv->table);
@@ -990,8 +993,6 @@ const TypeLevel* getLevel(TypeId ty)
         return &ttv->level;
     else if (auto ftv = get<FunctionTypeVar>(ty))
         return &ftv->level;
-    else if (auto ctv = get<ConstrainedTypeVar>(ty))
-        return &ctv->level;
     else
         return nullptr;
 }
@@ -1056,11 +1057,6 @@ const std::vector<TypeId>& getTypes(const IntersectionTypeVar* itv)
     return itv->parts;
 }
 
-const std::vector<TypeId>& getTypes(const ConstrainedTypeVar* ctv)
-{
-    return ctv->parts;
-}
-
 UnionTypeVarIterator begin(const UnionTypeVar* utv)
 {
     return UnionTypeVarIterator{utv};
@@ -1081,17 +1077,6 @@ IntersectionTypeVarIterator end(const IntersectionTypeVar* itv)
     return IntersectionTypeVarIterator{};
 }
 
-ConstrainedTypeVarIterator begin(const ConstrainedTypeVar* ctv)
-{
-    return ConstrainedTypeVarIterator{ctv};
-}
-
-ConstrainedTypeVarIterator end(const ConstrainedTypeVar* ctv)
-{
-    return ConstrainedTypeVarIterator{};
-}
-
-
 static std::vector<TypeId> parseFormatString(TypeChecker& typechecker, const char* data, size_t size)
 {
     const char* options = "cdiouxXeEfgGqs*";

Analysis/src/Unifier.cpp

@@ -13,16 +13,13 @@
 
 #include <algorithm>
 
-LUAU_FASTINT(LuauTypeInferRecursionLimit);
 LUAU_FASTINT(LuauTypeInferTypePackLoopLimit);
-LUAU_FASTINT(LuauTypeInferIterationLimit);
-LUAU_FASTFLAG(LuauAutocompleteDynamicLimits)
-LUAU_FASTINTVARIABLE(LuauTypeInferLowerBoundsIterationLimit, 2000);
 LUAU_FASTFLAG(LuauErrorRecoveryType);
 LUAU_FASTFLAG(LuauUnknownAndNeverType)
 LUAU_FASTFLAGVARIABLE(LuauSubtypeNormalizer, false);
 LUAU_FASTFLAGVARIABLE(LuauScalarShapeSubtyping, false)
 LUAU_FASTFLAGVARIABLE(LuauInstantiateInSubtyping, false)
+LUAU_FASTFLAGVARIABLE(LuauOverloadedFunctionSubtypingPerf, false);
 LUAU_FASTFLAG(LuauClassTypeVarsInSubstitution)
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 
@@ -95,15 +92,6 @@ struct PromoteTypeLevels final : TypeVarOnceVisitor
         return true;
     }
 
-    bool visit(TypeId ty, const ConstrainedTypeVar&) override
-    {
-        if (!FFlag::LuauUnknownAndNeverType)
-            return visit(ty);
-
-        promote(ty, log.getMutable<ConstrainedTypeVar>(ty));
-        return true;
-    }
-
     bool visit(TypeId ty, const FunctionTypeVar&) override
     {
         // Type levels of types from other modules are already global, so we don't need to promote anything inside
@@ -368,26 +356,14 @@ void Unifier::tryUnify(TypeId subTy, TypeId superTy, bool isFunctionCall, bool i
 
 void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool isIntersection)
 {
-    RecursionLimiter _ra(&sharedState.counters.recursionCount,
+    RecursionLimiter _ra(&sharedState.counters.recursionCount, sharedState.counters.recursionLimit);
-        FFlag::LuauAutocompleteDynamicLimits ? sharedState.counters.recursionLimit : FInt::LuauTypeInferRecursionLimit);
 
     ++sharedState.counters.iterationCount;
 
-    if (FFlag::LuauAutocompleteDynamicLimits)
+    if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
     {
-        if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
+        reportError(TypeError{location, UnificationTooComplex{}});
-        {
+        return;
-            reportError(TypeError{location, UnificationTooComplex{}});
-            return;
-        }
-    }
-    else
-    {
-        if (FInt::LuauTypeInferIterationLimit > 0 && FInt::LuauTypeInferIterationLimit < sharedState.counters.iterationCount)
-        {
-            reportError(TypeError{location, UnificationTooComplex{}});
-            return;
-        }
     }
 
     superTy = log.follow(superTy);
@@ -396,9 +372,6 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
     if (superTy == subTy)
         return;
 
-    if (log.get<ConstrainedTypeVar>(superTy))
-        return tryUnifyWithConstrainedSuperTypeVar(subTy, superTy);
-
     auto superFree = log.getMutable<FreeTypeVar>(superTy);
     auto subFree = log.getMutable<FreeTypeVar>(subTy);
 
@@ -520,9 +493,7 @@ void Unifier::tryUnify_(TypeId subTy, TypeId superTy, bool isFunctionCall, bool
 
     size_t errorCount = errors.size();
 
-    if (log.get<ConstrainedTypeVar>(subTy))
+    if (const UnionTypeVar* subUnion = log.getMutable<UnionTypeVar>(subTy))
-        tryUnifyWithConstrainedSubTypeVar(subTy, superTy);
-    else if (const UnionTypeVar* subUnion = log.getMutable<UnionTypeVar>(subTy))
     {
         tryUnifyUnionWithType(subTy, subUnion, superTy);
     }
@@ -1011,10 +982,17 @@ TypePackId Unifier::tryApplyOverloadedFunction(TypeId function, const Normalized
                     log.concat(std::move(innerState.log));
                     if (result)
                     {
+                        if (FFlag::LuauOverloadedFunctionSubtypingPerf)
+                        {
+                            innerState.log.clear();
+                            innerState.tryUnify_(*result, ftv->retTypes);
+                        }
+                        if (FFlag::LuauOverloadedFunctionSubtypingPerf && innerState.errors.empty())
+                            log.concat(std::move(innerState.log));
                         // Annoyingly, since we don't support intersection of generic type packs,
                         // the intersection may fail. We rather arbitrarily use the first matching overload
                         // in that case.
-                        if (std::optional<TypePackId> intersect = normalizer->intersectionOfTypePacks(*result, ftv->retTypes))
+                        else if (std::optional<TypePackId> intersect = normalizer->intersectionOfTypePacks(*result, ftv->retTypes))
                             result = intersect;
                     }
                     else
@@ -1214,26 +1192,14 @@ void Unifier::tryUnify(TypePackId subTp, TypePackId superTp, bool isFunctionCall
  */
 void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCall)
 {
-    RecursionLimiter _ra(&sharedState.counters.recursionCount,
+    RecursionLimiter _ra(&sharedState.counters.recursionCount, sharedState.counters.recursionLimit);
-        FFlag::LuauAutocompleteDynamicLimits ? sharedState.counters.recursionLimit : FInt::LuauTypeInferRecursionLimit);
 
     ++sharedState.counters.iterationCount;
 
-    if (FFlag::LuauAutocompleteDynamicLimits)
+    if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
     {
-        if (sharedState.counters.iterationLimit > 0 && sharedState.counters.iterationLimit < sharedState.counters.iterationCount)
+        reportError(TypeError{location, UnificationTooComplex{}});
-        {
+        return;
-            reportError(TypeError{location, UnificationTooComplex{}});
-            return;
-        }
-    }
-    else
-    {
-        if (FInt::LuauTypeInferIterationLimit > 0 && FInt::LuauTypeInferIterationLimit < sharedState.counters.iterationCount)
-        {
-            reportError(TypeError{location, UnificationTooComplex{}});
-            return;
-        }
     }
 
     superTp = log.follow(superTp);
@@ -2314,186 +2280,6 @@ std::optional<TypeId> Unifier::findTablePropertyRespectingMeta(TypeId lhsType, N
     return Luau::findTablePropertyRespectingMeta(singletonTypes, errors, lhsType, name, location);
 }
 
-void Unifier::tryUnifyWithConstrainedSubTypeVar(TypeId subTy, TypeId superTy)
-{
-    const ConstrainedTypeVar* subConstrained = get<ConstrainedTypeVar>(subTy);
-    if (!subConstrained)
-        ice("tryUnifyWithConstrainedSubTypeVar received non-ConstrainedTypeVar subTy!");
-
-    const std::vector<TypeId>& subTyParts = subConstrained->parts;
-
-    // A | B <: T if A <: T and B <: T
-    bool failed = false;
-    std::optional<TypeError> unificationTooComplex;
-
-    const size_t count = subTyParts.size();
-
-    for (size_t i = 0; i < count; ++i)
-    {
-        TypeId type = subTyParts[i];
-        Unifier innerState = makeChildUnifier();
-        innerState.tryUnify_(type, superTy);
-
-        if (i == count - 1)
-            log.concat(std::move(innerState.log));
-
-        ++i;
-
-        if (auto e = hasUnificationTooComplex(innerState.errors))
-            unificationTooComplex = e;
-
-        if (!innerState.errors.empty())
-        {
-            failed = true;
-            break;
-        }
-    }
-
-    if (unificationTooComplex)
-        reportError(*unificationTooComplex);
-    else if (failed)
-        reportError(TypeError{location, TypeMismatch{superTy, subTy}});
-    else
-        log.replace(subTy, BoundTypeVar{superTy});
-}
-
-void Unifier::tryUnifyWithConstrainedSuperTypeVar(TypeId subTy, TypeId superTy)
-{
-    ConstrainedTypeVar* superC = log.getMutable<ConstrainedTypeVar>(superTy);
-    if (!superC)
-        ice("tryUnifyWithConstrainedSuperTypeVar received non-ConstrainedTypeVar superTy!");
-
-    // subTy could be a
-    //  table
-    //  metatable
-    //  class
-    //  function
-    //  primitive
-    //  free
-    //  generic
-    //  intersection
-    //  union
-    // Do we really just tack it on?  I think we might!
-    // We can certainly do some deduplication.
-    // Is there any point to deducing Player|Instance when we could just reduce to Instance?
-    // Is it actually ok to have multiple free types in a single intersection?  What if they are later unified into the same type?
-    // Maybe we do a simplification step during quantification.
-
-    auto it = std::find(superC->parts.begin(), superC->parts.end(), subTy);
-    if (it != superC->parts.end())
-        return;
-
-    superC->parts.push_back(subTy);
-}
-
-void Unifier::unifyLowerBound(TypePackId subTy, TypePackId superTy, TypeLevel demotedLevel)
-{
-    // The duplication between this and regular typepack unification is tragic.
-
-    auto superIter = begin(superTy, &log);
-    auto superEndIter = end(superTy);
-
-    auto subIter = begin(subTy, &log);
-    auto subEndIter = end(subTy);
-
-    int count = FInt::LuauTypeInferLowerBoundsIterationLimit;
-
-    for (; subIter != subEndIter; ++subIter)
-    {
-        if (0 >= --count)
-            ice("Internal recursion counter limit exceeded in Unifier::unifyLowerBound");
-
-        if (superIter != superEndIter)
-        {
-            tryUnify_(*subIter, *superIter);
-            ++superIter;
-            continue;
-        }
-
-        if (auto t = superIter.tail())
-        {
-            TypePackId tailPack = follow(*t);
-
-            if (log.get<FreeTypePack>(tailPack) && occursCheck(tailPack, subTy))
-                return;
-
-            FreeTypePack* freeTailPack = log.getMutable<FreeTypePack>(tailPack);
-            if (!freeTailPack)
-                return;
-
-            TypePack* tp = getMutable<TypePack>(log.replace(tailPack, TypePack{}));
-
-            for (; subIter != subEndIter; ++subIter)
-            {
-                tp->head.push_back(types->addType(ConstrainedTypeVar{demotedLevel, {follow(*subIter)}}));
-            }
-
-            tp->tail = subIter.tail();
-        }
-
-        return;
-    }
-
-    if (superIter != superEndIter)
-    {
-        if (auto subTail = subIter.tail())
-        {
-            TypePackId subTailPack = follow(*subTail);
-            if (get<FreeTypePack>(subTailPack))
-            {
-                TypePack* tp = getMutable<TypePack>(log.replace(subTailPack, TypePack{}));
-
-                for (; superIter != superEndIter; ++superIter)
-                    tp->head.push_back(*superIter);
-            }
-            else if (const VariadicTypePack* subVariadic = log.getMutable<VariadicTypePack>(subTailPack))
-            {
-                while (superIter != superEndIter)
-                {
-                    tryUnify_(subVariadic->ty, *superIter);
-                    ++superIter;
-                }
-            }
-        }
-        else
-        {
-            while (superIter != superEndIter)
-            {
-                if (!isOptional(*superIter))
-                {
-                    errors.push_back(TypeError{location, CountMismatch{size(superTy), std::nullopt, size(subTy), CountMismatch::Return}});
-                    return;
-                }
-                ++superIter;
-            }
-        }
-
-        return;
-    }
-
-    // Both iters are at their respective tails
-    auto subTail = subIter.tail();
-    auto superTail = superIter.tail();
-    if (subTail && superTail)
-        tryUnify(*subTail, *superTail);
-    else if (subTail)
-    {
-        const FreeTypePack* freeSubTail = log.getMutable<FreeTypePack>(*subTail);
-        if (freeSubTail)
-        {
-            log.replace(*subTail, TypePack{});
-        }
-    }
-    else if (superTail)
-    {
-        const FreeTypePack* freeSuperTail = log.getMutable<FreeTypePack>(*superTail);
-        if (freeSuperTail)
-        {
-            log.replace(*superTail, TypePack{});
-        }
-    }
-}
-
 bool Unifier::occursCheck(TypeId needle, TypeId haystack)
 {
     sharedState.tempSeenTy.clear();
@@ -2503,8 +2289,7 @@ bool Unifier::occursCheck(TypeId needle, TypeId haystack)
 
 bool Unifier::occursCheck(DenseHashSet<TypeId>& seen, TypeId needle, TypeId haystack)
 {
-    RecursionLimiter _ra(&sharedState.counters.recursionCount,
+    RecursionLimiter _ra(&sharedState.counters.recursionCount, sharedState.counters.recursionLimit);
-        FFlag::LuauAutocompleteDynamicLimits ? sharedState.counters.recursionLimit : FInt::LuauTypeInferRecursionLimit);
 
     bool occurrence = false;
 
@@ -2547,11 +2332,6 @@ bool Unifier::occursCheck(DenseHashSet<TypeId>& seen, TypeId needle, TypeId hays
         for (TypeId ty : a->parts)
             check(ty);
     }
-    else if (auto a = log.getMutable<ConstrainedTypeVar>(haystack))
-    {
-        for (TypeId ty : a->parts)
-            check(ty);
-    }
 
     return occurrence;
 }
@@ -2579,8 +2359,7 @@ bool Unifier::occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, Typ
     if (!log.getMutable<Unifiable::Free>(needle))
         ice("Expected needle pack to be free");
 
-    RecursionLimiter _ra(&sharedState.counters.recursionCount,
+    RecursionLimiter _ra(&sharedState.counters.recursionCount, sharedState.counters.recursionLimit);
-        FFlag::LuauAutocompleteDynamicLimits ? sharedState.counters.recursionLimit : FInt::LuauTypeInferRecursionLimit);
 
     while (!log.getMutable<ErrorTypeVar>(haystack))
     {

CLI/Analyze.cpp

@@ -14,7 +14,6 @@
 #endif
 
 LUAU_FASTFLAG(DebugLuauTimeTracing)
-LUAU_FASTFLAG(LuauTypeMismatchModuleNameResolution)
 
 enum class ReportFormat
 {
@@ -55,11 +54,9 @@ static void reportError(const Luau::Frontend& frontend, ReportFormat format, con
 
     if (const Luau::SyntaxError* syntaxError = Luau::get_if<Luau::SyntaxError>(&error.data))
         report(format, humanReadableName.c_str(), error.location, "SyntaxError", syntaxError->message.c_str());
-    else if (FFlag::LuauTypeMismatchModuleNameResolution)
+    else
         report(format, humanReadableName.c_str(), error.location, "TypeError",
             Luau::toString(error, Luau::TypeErrorToStringOptions{frontend.fileResolver}).c_str());
-    else
-        report(format, humanReadableName.c_str(), error.location, "TypeError", Luau::toString(error).c_str());
 }
 
 static void reportWarning(ReportFormat format, const char* name, const Luau::LintWarning& warning)

CLI/Repl.cpp

@@ -16,6 +16,7 @@
 
 #include "isocline.h"
 
+#include <algorithm>
 #include <memory>
 
 #ifdef _WIN32
@@ -49,6 +50,8 @@ enum class CompileFormat
     Binary,
     Remarks,
     Codegen,
+    CodegenVerbose,
+    CodegenNull,
     Null
 };
 
@@ -673,21 +676,33 @@ static void reportError(const char* name, const Luau::CompileError& error)
     report(name, error.getLocation(), "CompileError", error.what());
 }
 
-static std::string getCodegenAssembly(const char* name, const std::string& bytecode)
+static std::string getCodegenAssembly(const char* name, const std::string& bytecode, Luau::CodeGen::AssemblyOptions options)
 {
     std::unique_ptr<lua_State, void (*)(lua_State*)> globalState(luaL_newstate(), lua_close);
     lua_State* L = globalState.get();
 
-    setupState(L);
-
     if (luau_load(L, name, bytecode.data(), bytecode.size(), 0) == 0)
-        return Luau::CodeGen::getAssemblyText(L, -1);
+        return Luau::CodeGen::getAssembly(L, -1, options);
 
     fprintf(stderr, "Error loading bytecode %s\n", name);
     return "";
 }
 
-static bool compileFile(const char* name, CompileFormat format)
+static void annotateInstruction(void* context, std::string& text, int fid, int instid)
+{
+    Luau::BytecodeBuilder& bcb = *(Luau::BytecodeBuilder*)context;
+
+    bcb.annotateInstruction(text, fid, instid);
+}
+
+struct CompileStats
+{
+    size_t lines;
+    size_t bytecode;
+    size_t codegen;
+};
+
+static bool compileFile(const char* name, CompileFormat format, CompileStats& stats)
 {
     std::optional<std::string> source = readFile(name);
     if (!source)
@@ -696,9 +711,12 @@ static bool compileFile(const char* name, CompileFormat format)
         return false;
     }
 
+    stats.lines += std::count(source->begin(), source->end(), '\n');
+
     try
     {
         Luau::BytecodeBuilder bcb;
+        Luau::CodeGen::AssemblyOptions options = {format == CompileFormat::CodegenNull, format == CompileFormat::Codegen, annotateInstruction, &bcb};
 
         if (format == CompileFormat::Text)
         {
@@ -711,8 +729,15 @@ static bool compileFile(const char* name, CompileFormat format)
             bcb.setDumpFlags(Luau::BytecodeBuilder::Dump_Source | Luau::BytecodeBuilder::Dump_Remarks);
             bcb.setDumpSource(*source);
         }
+        else if (format == CompileFormat::Codegen || format == CompileFormat::CodegenVerbose)
+        {
+            bcb.setDumpFlags(Luau::BytecodeBuilder::Dump_Code | Luau::BytecodeBuilder::Dump_Source | Luau::BytecodeBuilder::Dump_Locals |
+                             Luau::BytecodeBuilder::Dump_Remarks);
+            bcb.setDumpSource(*source);
+        }
 
         Luau::compileOrThrow(bcb, *source, copts());
+        stats.bytecode += bcb.getBytecode().size();
 
         switch (format)
         {
@@ -726,7 +751,11 @@ static bool compileFile(const char* name, CompileFormat format)
             fwrite(bcb.getBytecode().data(), 1, bcb.getBytecode().size(), stdout);
             break;
         case CompileFormat::Codegen:
-            printf("%s", getCodegenAssembly(name, bcb.getBytecode()).c_str());
+        case CompileFormat::CodegenVerbose:
+            printf("%s", getCodegenAssembly(name, bcb.getBytecode(), options).c_str());
+            break;
+        case CompileFormat::CodegenNull:
+            stats.codegen += getCodegenAssembly(name, bcb.getBytecode(), options).size();
             break;
         case CompileFormat::Null:
             break;
@@ -755,7 +784,7 @@ static void displayHelp(const char* argv0)
     printf("\n");
     printf("Available modes:\n");
     printf("  omitted: compile and run input files one by one\n");
-    printf("  --compile[=format]: compile input files and output resulting formatted bytecode (binary, text, remarks, codegen or null)\n");
+    printf("  --compile[=format]: compile input files and output resulting bytecode/assembly (binary, text, remarks, codegen)\n");
     printf("\n");
     printf("Available options:\n");
     printf("  --coverage: collect code coverage while running the code and output results to coverage.out\n");
@@ -812,6 +841,14 @@ int replMain(int argc, char** argv)
         {
             compileFormat = CompileFormat::Codegen;
         }
+        else if (strcmp(argv[1], "--compile=codegenverbose") == 0)
+        {
+            compileFormat = CompileFormat::CodegenVerbose;
+        }
+        else if (strcmp(argv[1], "--compile=codegennull") == 0)
+        {
+            compileFormat = CompileFormat::CodegenNull;
+        }
         else if (strcmp(argv[1], "--compile=null") == 0)
         {
             compileFormat = CompileFormat::Null;
@@ -923,10 +960,16 @@ int replMain(int argc, char** argv)
             _setmode(_fileno(stdout), _O_BINARY);
 #endif
 
+        CompileStats stats = {};
         int failed = 0;
 
         for (const std::string& path : files)
-            failed += !compileFile(path.c_str(), compileFormat);
+            failed += !compileFile(path.c_str(), compileFormat, stats);
+
+        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));
 
         return failed ? 1 : 0;
     }

CodeGen/include/Luau/AssemblyBuilderX64.h

@@ -23,6 +23,19 @@ enum class RoundingModeX64
     RoundToZero = 0b11,
 };
 
+enum class AlignmentDataX64
+{
+    Nop,
+    Int3,
+    Ud2, // int3 will be used as a fall-back if it doesn't fit
+};
+
+enum class ABIX64
+{
+    Windows,
+    SystemV,
+};
+
 class AssemblyBuilderX64
 {
 public:
@@ -80,6 +93,10 @@ public:
 
     void int3();
 
+    // Code alignment
+    void nop(uint32_t length = 1);
+    void align(uint32_t alignment, AlignmentDataX64 data = AlignmentDataX64::Nop);
+
     // AVX
     void vaddpd(OperandX64 dst, OperandX64 src1, OperandX64 src2);
     void vaddps(OperandX64 dst, OperandX64 src1, OperandX64 src2);
@@ -131,6 +148,8 @@ public:
 
     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;
@@ -140,6 +159,8 @@ public:
 
     const bool logText = false;
 
+    const ABIX64 abi;
+
 private:
     // Instruction archetypes
     void placeBinary(const char* name, OperandX64 lhs, OperandX64 rhs, uint8_t codeimm8, uint8_t codeimm, uint8_t codeimmImm8, uint8_t code8rev,
@@ -177,7 +198,6 @@ private:
 
     void commit();
     LUAU_NOINLINE void extend();
-    uint32_t getCodeSize();
 
     // Data
     size_t allocateData(size_t size, size_t align);
@@ -192,8 +212,8 @@ private:
     LUAU_NOINLINE void log(const char* opcode, Label label);
     void log(OperandX64 op);
 
-    const char* getSizeName(SizeX64 size);
+    const char* getSizeName(SizeX64 size) const;
-    const char* getRegisterName(RegisterX64 reg);
+    const char* getRegisterName(RegisterX64 reg) const;
 
     uint32_t nextLabel = 1;
     std::vector<Label> pendingLabels;

CodeGen/include/Luau/CodeAllocator.h

@@ -11,6 +11,8 @@ namespace Luau
 namespace CodeGen
 {
 
+constexpr uint32_t kCodeAlignment = 32;
+
 struct CodeAllocator
 {
     CodeAllocator(size_t blockSize, size_t maxTotalSize);

CodeGen/include/Luau/CodeGen.h

@@ -17,8 +17,20 @@ void create(lua_State* L);
 // Builds target function and all inner functions
 void compile(lua_State* L, int idx);
 
-// Generates assembly text for target function and all inner functions
+using annotatorFn = void (*)(void* context, std::string& result, int fid, int instid);
-std::string getAssemblyText(lua_State* L, int idx);
+
+struct AssemblyOptions
+{
+    bool outputBinary = false;
+    bool skipOutlinedCode = false;
+
+    // Optional annotator function can be provided to describe each instruction, it takes function id and sequential instruction id
+    annotatorFn annotator = nullptr;
+    void* annotatorContext = nullptr;
+};
+
+// Generates assembly for target function and all inner functions
+std::string getAssembly(lua_State* L, int idx, AssemblyOptions options = {});
 
 } // namespace CodeGen
 } // namespace Luau

CodeGen/include/Luau/OperandX64.h

@@ -94,6 +94,11 @@ constexpr OperandX64 operator+(RegisterX64 reg, int32_t disp)
     return OperandX64(SizeX64::none, noreg, 1, reg, disp);
 }
 
+constexpr OperandX64 operator-(RegisterX64 reg, int32_t disp)
+{
+    return OperandX64(SizeX64::none, noreg, 1, reg, -disp);
+}
+
 constexpr OperandX64 operator+(RegisterX64 base, RegisterX64 index)
 {
     LUAU_ASSERT(index.index != 4 && "sp cannot be used as index");

CodeGen/include/Luau/RegisterX64.h

@@ -113,5 +113,20 @@ constexpr RegisterX64 ymm13{SizeX64::ymmword, 13};
 constexpr RegisterX64 ymm14{SizeX64::ymmword, 14};
 constexpr RegisterX64 ymm15{SizeX64::ymmword, 15};
 
+constexpr RegisterX64 byteReg(RegisterX64 reg)
+{
+    return RegisterX64{SizeX64::byte, reg.index};
+}
+
+constexpr RegisterX64 wordReg(RegisterX64 reg)
+{
+    return RegisterX64{SizeX64::word, reg.index};
+}
+
+constexpr RegisterX64 dwordReg(RegisterX64 reg)
+{
+    return RegisterX64{SizeX64::dword, reg.index};
+}
+
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/AssemblyBuilderX64.cpp

@@ -29,7 +29,7 @@ static_assert(sizeof(textForCondition) / sizeof(textForCondition[0]) == size_t(C
 #define REX_X(reg) (((reg).index & 0x8) >> 2)
 #define REX_B(reg) (((reg).index & 0x8) >> 3)
 
-#define AVX_W(value) (!(value) ? 0x80 : 0x0)
+#define AVX_W(value) ((value) ? 0x80 : 0x0)
 #define AVX_R(reg) ((~(reg).index & 0x8) << 4)
 #define AVX_X(reg) ((~(reg).index & 0x8) << 3)
 #define AVX_B(reg) ((~(reg).index & 0x8) << 2)
@@ -50,12 +50,23 @@ const unsigned AVX_66 = 0b01;
 const unsigned AVX_F3 = 0b10;
 const unsigned AVX_F2 = 0b11;
 
-const unsigned kMaxAlign = 16;
+const unsigned kMaxAlign = 32;
+const unsigned kMaxInstructionLength = 16;
 
 const uint8_t kRoundingPrecisionInexact = 0b1000;
 
+static ABIX64 getCurrentX64ABI()
+{
+#if defined(_WIN32)
+    return ABIX64::Windows;
+#else
+    return ABIX64::SystemV;
+#endif
+}
+
 AssemblyBuilderX64::AssemblyBuilderX64(bool logText)
     : logText(logText)
+    , abi(getCurrentX64ABI())
 {
     data.resize(4096);
     dataPos = data.size(); // data is filled backwards
@@ -416,6 +427,153 @@ void AssemblyBuilderX64::int3()
         log("int3");
 
     place(0xcc);
+    commit();
+}
+
+void AssemblyBuilderX64::nop(uint32_t length)
+{
+    while (length != 0)
+    {
+        uint32_t step = length > 9 ? 9 : length;
+        length -= step;
+
+        switch (step)
+        {
+        case 1:
+            if (logText)
+                logAppend(" nop\n");
+            place(0x90);
+            break;
+        case 2:
+            if (logText)
+                logAppend(" xchg        ax, ax ; %u-byte nop\n", step);
+            place(0x66);
+            place(0x90);
+            break;
+        case 3:
+            if (logText)
+                logAppend(" nop         dword ptr[rax] ; %u-byte nop\n", step);
+            place(0x0f);
+            place(0x1f);
+            place(0x00);
+            break;
+        case 4:
+            if (logText)
+                logAppend(" nop         dword ptr[rax] ; %u-byte nop\n", step);
+            place(0x0f);
+            place(0x1f);
+            place(0x40);
+            place(0x00);
+            break;
+        case 5:
+            if (logText)
+                logAppend(" nop         dword ptr[rax+rax] ; %u-byte nop\n", step);
+            place(0x0f);
+            place(0x1f);
+            place(0x44);
+            place(0x00);
+            place(0x00);
+            break;
+        case 6:
+            if (logText)
+                logAppend(" nop         word ptr[rax+rax] ; %u-byte nop\n", step);
+            place(0x66);
+            place(0x0f);
+            place(0x1f);
+            place(0x44);
+            place(0x00);
+            place(0x00);
+            break;
+        case 7:
+            if (logText)
+                logAppend(" nop         dword ptr[rax] ; %u-byte nop\n", step);
+            place(0x0f);
+            place(0x1f);
+            place(0x80);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            break;
+        case 8:
+            if (logText)
+                logAppend(" nop         dword ptr[rax+rax] ; %u-byte nop\n", step);
+            place(0x0f);
+            place(0x1f);
+            place(0x84);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            break;
+        case 9:
+            if (logText)
+                logAppend(" nop         word ptr[rax+rax] ; %u-byte nop\n", step);
+            place(0x66);
+            place(0x0f);
+            place(0x1f);
+            place(0x84);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            place(0x00);
+            break;
+        }
+
+        commit();
+    }
+}
+
+void AssemblyBuilderX64::align(uint32_t alignment, AlignmentDataX64 data)
+{
+    LUAU_ASSERT((alignment & (alignment - 1)) == 0);
+
+    uint32_t size = getCodeSize();
+    uint32_t pad = ((size + alignment - 1) & ~(alignment - 1)) - size;
+
+    switch (data)
+    {
+    case AlignmentDataX64::Nop:
+        if (logText)
+            logAppend("; align %u\n", alignment);
+
+        nop(pad);
+        break;
+    case AlignmentDataX64::Int3:
+        if (logText)
+            logAppend("; align %u using int3\n", alignment);
+
+        while (codePos + pad > codeEnd)
+            extend();
+
+        for (uint32_t i = 0; i < pad; ++i)
+            place(0xcc);
+
+        commit();
+        break;
+    case AlignmentDataX64::Ud2:
+        if (logText)
+            logAppend("; align %u using ud2\n", alignment);
+
+        while (codePos + pad > codeEnd)
+            extend();
+
+        uint32_t i = 0;
+
+        for (; i + 1 < pad; i += 2)
+        {
+            place(0x0f);
+            place(0x0b);
+        }
+
+        if (i < pad)
+            place(0xcc);
+
+        commit();
+        break;
+    }
 }
 
 void AssemblyBuilderX64::vaddpd(OperandX64 dst, OperandX64 src1, OperandX64 src2)
@@ -465,12 +623,12 @@ void AssemblyBuilderX64::vucomisd(OperandX64 src1, OperandX64 src2)
 
 void AssemblyBuilderX64::vcvttsd2si(OperandX64 dst, OperandX64 src)
 {
-    placeAvx("vcvttsd2si", dst, src, 0x2c, dst.base.size == SizeX64::dword, AVX_0F, AVX_F2);
+    placeAvx("vcvttsd2si", dst, src, 0x2c, dst.base.size == SizeX64::qword, AVX_0F, AVX_F2);
 }
 
 void AssemblyBuilderX64::vcvtsi2sd(OperandX64 dst, OperandX64 src1, OperandX64 src2)
 {
-    placeAvx("vcvtsi2sd", dst, src1, src2, 0x2a, (src2.cat == CategoryX64::reg ? src2.base.size : src2.memSize) == SizeX64::dword, AVX_0F, AVX_F2);
+    placeAvx("vcvtsi2sd", dst, src1, src2, 0x2a, (src2.cat == CategoryX64::reg ? src2.base.size : src2.memSize) == SizeX64::qword, AVX_0F, AVX_F2);
 }
 
 void AssemblyBuilderX64::vroundsd(OperandX64 dst, OperandX64 src1, OperandX64 src2, RoundingModeX64 roundingMode)
@@ -626,6 +784,21 @@ OperandX64 AssemblyBuilderX64::bytes(const void* ptr, size_t size, size_t align)
     return OperandX64(SizeX64::qword, noreg, 1, rip, int32_t(pos - data.size()));
 }
 
+void AssemblyBuilderX64::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 AssemblyBuilderX64::getCodeSize() const
+{
+    return uint32_t(codePos - code.data());
+}
+
 void AssemblyBuilderX64::placeBinary(const char* name, OperandX64 lhs, OperandX64 rhs, uint8_t codeimm8, uint8_t codeimm, uint8_t codeimmImm8,
     uint8_t code8rev, uint8_t coderev, uint8_t code8, uint8_t code, uint8_t opreg)
 {
@@ -1054,7 +1227,7 @@ void AssemblyBuilderX64::commit()
 {
     LUAU_ASSERT(codePos <= codeEnd);
 
-    if (codeEnd - codePos < 16)
+    if (codeEnd - codePos < kMaxInstructionLength)
         extend();
 }
 
@@ -1067,11 +1240,6 @@ void AssemblyBuilderX64::extend()
     codeEnd = code.data() + code.size();
 }
 
-uint32_t AssemblyBuilderX64::getCodeSize()
-{
-    return uint32_t(codePos - code.data());
-}
-
 size_t AssemblyBuilderX64::allocateData(size_t size, size_t align)
 {
     LUAU_ASSERT(align > 0 && align <= kMaxAlign && (align & (align - 1)) == 0);
@@ -1174,8 +1342,10 @@ void AssemblyBuilderX64::log(OperandX64 op)
         {
             if (op.imm >= 0 && op.imm <= 9)
                 logAppend("+%d", op.imm);
-            else
+            else if (op.imm > 0)
                 logAppend("+0%Xh", op.imm);
+            else
+                logAppend("-0%Xh", -op.imm);
         }
 
         text.append("]");
@@ -1191,17 +1361,7 @@ void AssemblyBuilderX64::log(OperandX64 op)
     }
 }
 
-void AssemblyBuilderX64::logAppend(const char* fmt, ...)
+const char* AssemblyBuilderX64::getSizeName(SizeX64 size) const
-{
-    char buf[256];
-    va_list args;
-    va_start(args, fmt);
-    vsnprintf(buf, sizeof(buf), fmt, args);
-    va_end(args);
-    text.append(buf);
-}
-
-const char* AssemblyBuilderX64::getSizeName(SizeX64 size)
 {
     static const char* sizeNames[] = {"none", "byte", "word", "dword", "qword", "xmmword", "ymmword"};
 
@@ -1209,7 +1369,7 @@ const char* AssemblyBuilderX64::getSizeName(SizeX64 size)
     return sizeNames[unsigned(size)];
 }
 
-const char* AssemblyBuilderX64::getRegisterName(RegisterX64 reg)
+const char* AssemblyBuilderX64::getRegisterName(RegisterX64 reg) const
 {
     static const char* names[][16] = {{"rip", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""},
         {"al", "cl", "dl", "bl", "spl", "bpl", "sil", "dil", "r8b", "r9b", "r10b", "r11b", "r12b", "r13b", "r14b", "r15b"},

CodeGen/src/ByteUtils.h

@@ -1,7 +1,9 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#include "Luau/Common.h"
+
+#if defined(LUAU_BIG_ENDIAN)
 #include <endian.h>
 #endif
 
@@ -15,7 +17,7 @@ inline uint8_t* writeu8(uint8_t* target, uint8_t value)
 
 inline uint8_t* writeu32(uint8_t* target, uint32_t value)
 {
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(LUAU_BIG_ENDIAN)
     value = htole32(value);
 #endif
 
@@ -25,7 +27,7 @@ inline uint8_t* writeu32(uint8_t* target, uint32_t value)
 
 inline uint8_t* writeu64(uint8_t* target, uint64_t value)
 {
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(LUAU_BIG_ENDIAN)
     value = htole64(value);
 #endif
 
@@ -51,7 +53,7 @@ inline uint8_t* writeuleb128(uint8_t* target, uint64_t value)
 
 inline uint8_t* writef32(uint8_t* target, float value)
 {
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(LUAU_BIG_ENDIAN)
     static_assert(sizeof(float) == sizeof(uint32_t), "type size must match to reinterpret data");
     uint32_t data;
     memcpy(&data, &value, sizeof(value));
@@ -65,7 +67,7 @@ inline uint8_t* writef32(uint8_t* target, float value)
 
 inline uint8_t* writef64(uint8_t* target, double value)
 {
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(LUAU_BIG_ENDIAN)
     static_assert(sizeof(double) == sizeof(uint64_t), "type size must match to reinterpret data");
     uint64_t data;
     memcpy(&data, &value, sizeof(value));

CodeGen/src/CodeAllocator.cpp

@@ -110,8 +110,8 @@ CodeAllocator::~CodeAllocator()
 bool CodeAllocator::allocate(
     uint8_t* data, size_t dataSize, uint8_t* code, size_t codeSize, uint8_t*& result, size_t& resultSize, uint8_t*& resultCodeStart)
 {
-    // 'Round up' to preserve 16 byte alignment
+    // 'Round up' to preserve code alignment
-    size_t alignedDataSize = (dataSize + 15) & ~15;
+    size_t alignedDataSize = (dataSize + (kCodeAlignment - 1)) & ~(kCodeAlignment - 1);
 
     size_t totalSize = alignedDataSize + codeSize;
 
@@ -187,8 +187,8 @@ bool CodeAllocator::allocateNewBlock(size_t& unwindInfoSize)
     {
         void* unwindInfo = createBlockUnwindInfo(context, block, blockSize, unwindInfoSize);
 
-        // 'Round up' to preserve 16 byte alignment of the following data and code
+        // 'Round up' to preserve alignment of the following data and code
-        unwindInfoSize = (unwindInfoSize + 15) & ~15;
+        unwindInfoSize = (unwindInfoSize + (kCodeAlignment - 1)) & ~(kCodeAlignment - 1);
 
         LUAU_ASSERT(unwindInfoSize <= kMaxReservedDataSize);
 

CodeGen/src/CodeBlockUnwind.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/CodeBlockUnwind.h"
 
+#include "Luau/CodeAllocator.h"
 #include "Luau/UnwindBuilder.h"
 
 #include <string.h>
@@ -58,7 +59,7 @@ void* createBlockUnwindInfo(void* context, uint8_t* block, size_t blockSize, siz
 
     // All unwinding related data is placed together at the start of the block
     size_t unwindSize = sizeof(RUNTIME_FUNCTION) + unwind->getSize();
-    unwindSize = (unwindSize + 15) & ~15; // Align to 16 bytes
+    unwindSize = (unwindSize + (kCodeAlignment - 1)) & ~(kCodeAlignment - 1); // Match code allocator alignment
     LUAU_ASSERT(blockSize >= unwindSize);
 
     RUNTIME_FUNCTION* runtimeFunc = (RUNTIME_FUNCTION*)block;
@@ -82,7 +83,7 @@ void* createBlockUnwindInfo(void* context, uint8_t* block, size_t blockSize, siz
 
     // All unwinding related data is placed together at the start of the block
     size_t unwindSize = unwind->getSize();
-    unwindSize = (unwindSize + 15) & ~15; // Align to 16 bytes
+    unwindSize = (unwindSize + (kCodeAlignment - 1)) & ~(kCodeAlignment - 1); // Match code allocator alignment
     LUAU_ASSERT(blockSize >= unwindSize);
 
     char* unwindData = (char*)block;

CodeGen/src/CodeGen.cpp

@@ -32,7 +32,9 @@ namespace Luau
 namespace CodeGen
 {
 
-static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& data, Proto* proto)
+constexpr uint32_t kFunctionAlignment = 32;
+
+static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& data, Proto* proto, AssemblyOptions options)
 {
     NativeProto* result = new NativeProto();
 
@@ -54,142 +56,177 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
     std::vector<Label> instLabels;
     instLabels.resize(proto->sizecode);
 
+    std::vector<Label> instFallbacks;
+    instFallbacks.resize(proto->sizecode);
+
+    build.align(kFunctionAlignment, AlignmentDataX64::Ud2);
+
     Label start = build.setLabel();
 
-    for (int i = 0; i < proto->sizecode;)
+    for (int i = 0, instid = 0; i < proto->sizecode; ++instid)
     {
         const Instruction* pc = &proto->code[i];
         LuauOpcode op = LuauOpcode(LUAU_INSN_OP(*pc));
 
         build.setLabel(instLabels[i]);
 
-        if (build.logText)
+        if (options.annotator)
-            build.logAppend("; #%d: %s\n", i, data.names[op]);
+            options.annotator(options.annotatorContext, build.text, proto->bytecodeid, instid);
 
         switch (op)
         {
         case LOP_NOP:
             break;
         case LOP_LOADNIL:
-            emitInstLoadNil(build, data, pc);
+            emitInstLoadNil(build, pc);
             break;
         case LOP_LOADB:
-            emitInstLoadB(build, data, pc, i, instLabels.data());
+            emitInstLoadB(build, pc, i, instLabels.data());
             break;
         case LOP_LOADN:
-            emitInstLoadN(build, data, pc);
+            emitInstLoadN(build, pc);
             break;
         case LOP_LOADK:
-            emitInstLoadK(build, data, pc, proto->k);
+            emitInstLoadK(build, pc);
+            break;
+        case LOP_LOADKX:
+            emitInstLoadKX(build, pc);
             break;
         case LOP_MOVE:
-            emitInstMove(build, data, pc);
+            emitInstMove(build, pc);
+            break;
+        case LOP_GETGLOBAL:
+            emitInstGetGlobal(build, pc, i, instFallbacks[i]);
+            break;
+        case LOP_SETGLOBAL:
+            emitInstSetGlobal(build, pc, i, instLabels.data(), instFallbacks[i]);
             break;
         case LOP_GETTABLE:
-            emitInstGetTable(build, pc, i);
+            emitInstGetTable(build, pc, i, instFallbacks[i]);
             break;
         case LOP_SETTABLE:
-            emitInstSetTable(build, pc, i);
+            emitInstSetTable(build, pc, i, instLabels.data(), instFallbacks[i]);
+            break;
+        case LOP_GETTABLEKS:
+            emitInstGetTableKS(build, pc, i, instFallbacks[i]);
+            break;
+        case LOP_SETTABLEKS:
+            emitInstSetTableKS(build, pc, i, instLabels.data(), instFallbacks[i]);
             break;
         case LOP_GETTABLEN:
-            emitInstGetTableN(build, pc, i);
+            emitInstGetTableN(build, pc, i, instFallbacks[i]);
             break;
         case LOP_SETTABLEN:
-            emitInstSetTableN(build, pc, i);
+            emitInstSetTableN(build, pc, i, instLabels.data(), instFallbacks[i]);
             break;
         case LOP_JUMP:
-            emitInstJump(build, data, pc, i, instLabels.data());
+            emitInstJump(build, pc, i, instLabels.data());
             break;
         case LOP_JUMPBACK:
-            emitInstJumpBack(build, data, pc, i, instLabels.data());
+            emitInstJumpBack(build, pc, i, instLabels.data());
             break;
         case LOP_JUMPIF:
-            emitInstJumpIf(build, data, pc, i, instLabels.data(), /* not_ */ false);
+            emitInstJumpIf(build, pc, i, instLabels.data(), /* not_ */ false);
             break;
         case LOP_JUMPIFNOT:
-            emitInstJumpIf(build, data, pc, i, instLabels.data(), /* not_ */ true);
+            emitInstJumpIf(build, pc, i, instLabels.data(), /* not_ */ true);
             break;
         case LOP_JUMPIFEQ:
-            emitInstJumpIfEq(build, data, pc, i, instLabels.data(), /* not_ */ false);
+            emitInstJumpIfEq(build, pc, i, instLabels.data(), /* not_ */ false, instFallbacks[i]);
             break;
         case LOP_JUMPIFLE:
-            emitInstJumpIfCond(build, data, pc, i, instLabels.data(), Condition::LessEqual);
+            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::LessEqual, instFallbacks[i]);
             break;
         case LOP_JUMPIFLT:
-            emitInstJumpIfCond(build, data, pc, i, instLabels.data(), Condition::Less);
+            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::Less, instFallbacks[i]);
             break;
         case LOP_JUMPIFNOTEQ:
-            emitInstJumpIfEq(build, data, pc, i, instLabels.data(), /* not_ */ true);
+            emitInstJumpIfEq(build, pc, i, instLabels.data(), /* not_ */ true, instFallbacks[i]);
             break;
         case LOP_JUMPIFNOTLE:
-            emitInstJumpIfCond(build, data, pc, i, instLabels.data(), Condition::NotLessEqual);
+            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::NotLessEqual, instFallbacks[i]);
             break;
         case LOP_JUMPIFNOTLT:
-            emitInstJumpIfCond(build, data, pc, i, instLabels.data(), Condition::NotLess);
+            emitInstJumpIfCond(build, pc, i, instLabels.data(), Condition::NotLess, instFallbacks[i]);
             break;
         case LOP_JUMPX:
-            emitInstJumpX(build, data, pc, i, instLabels.data());
+            emitInstJumpX(build, pc, i, instLabels.data());
             break;
         case LOP_JUMPXEQKNIL:
-            emitInstJumpxEqNil(build, data, pc, proto->k, i, instLabels.data());
+            emitInstJumpxEqNil(build, pc, i, instLabels.data());
             break;
         case LOP_JUMPXEQKB:
-            emitInstJumpxEqB(build, data, pc, proto->k, i, instLabels.data());
+            emitInstJumpxEqB(build, pc, i, instLabels.data());
             break;
         case LOP_JUMPXEQKN:
-            emitInstJumpxEqN(build, data, pc, proto->k, i, instLabels.data());
+            emitInstJumpxEqN(build, pc, proto->k, i, instLabels.data());
             break;
         case LOP_JUMPXEQKS:
-            emitInstJumpxEqS(build, data, pc, proto->k, i, instLabels.data());
+            emitInstJumpxEqS(build, pc, i, instLabels.data());
             break;
         case LOP_ADD:
-            emitInstAdd(build, pc, i);
+            emitInstBinary(build, pc, i, TM_ADD, instFallbacks[i]);
             break;
         case LOP_SUB:
-            emitInstSub(build, pc, i);
+            emitInstBinary(build, pc, i, TM_SUB, instFallbacks[i]);
             break;
         case LOP_MUL:
-            emitInstMul(build, pc, i);
+            emitInstBinary(build, pc, i, TM_MUL, instFallbacks[i]);
             break;
         case LOP_DIV:
-            emitInstDiv(build, pc, i);
+            emitInstBinary(build, pc, i, TM_DIV, instFallbacks[i]);
             break;
         case LOP_MOD:
-            emitInstMod(build, pc, i);
+            emitInstBinary(build, pc, i, TM_MOD, instFallbacks[i]);
             break;
         case LOP_POW:
-            emitInstPow(build, pc, i);
+            emitInstBinary(build, pc, i, TM_POW, instFallbacks[i]);
             break;
         case LOP_ADDK:
-            emitInstAddK(build, pc, proto->k, i);
+            emitInstBinaryK(build, pc, i, TM_ADD, instFallbacks[i]);
             break;
         case LOP_SUBK:
-            emitInstSubK(build, pc, proto->k, i);
+            emitInstBinaryK(build, pc, i, TM_SUB, instFallbacks[i]);
             break;
         case LOP_MULK:
-            emitInstMulK(build, pc, proto->k, i);
+            emitInstBinaryK(build, pc, i, TM_MUL, instFallbacks[i]);
             break;
         case LOP_DIVK:
-            emitInstDivK(build, pc, proto->k, i);
+            emitInstBinaryK(build, pc, i, TM_DIV, instFallbacks[i]);
             break;
         case LOP_MODK:
-            emitInstModK(build, pc, proto->k, i);
+            emitInstBinaryK(build, pc, i, TM_MOD, instFallbacks[i]);
             break;
         case LOP_POWK:
-            emitInstPowK(build, pc, proto->k, i);
+            emitInstPowK(build, pc, proto->k, i, instFallbacks[i]);
             break;
         case LOP_NOT:
             emitInstNot(build, pc);
             break;
         case LOP_MINUS:
-            emitInstMinus(build, pc, i);
+            emitInstMinus(build, pc, i, instFallbacks[i]);
             break;
         case LOP_LENGTH:
-            emitInstLength(build, pc, i);
+            emitInstLength(build, pc, i, instFallbacks[i]);
+            break;
+        case LOP_NEWTABLE:
+            emitInstNewTable(build, pc, i, instLabels.data());
+            break;
+        case LOP_DUPTABLE:
+            emitInstDupTable(build, pc, i, instLabels.data());
+            break;
+        case LOP_SETLIST:
+            emitInstSetList(build, pc, i, instLabels.data());
             break;
         case LOP_GETUPVAL:
             emitInstGetUpval(build, pc, i);
             break;
+        case LOP_SETUPVAL:
+            emitInstSetUpval(build, pc, i, instLabels.data());
+            break;
+        case LOP_CLOSEUPVALS:
+            emitInstCloseUpvals(build, pc, i, instLabels.data());
+            break;
         case LOP_FASTCALL:
             emitInstFastCall(build, pc, i, instLabels.data());
             break;
@@ -200,7 +237,7 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
             emitInstFastCall2(build, pc, i, instLabels.data());
             break;
         case LOP_FASTCALL2K:
-            emitInstFastCall2K(build, pc, proto->k, i, instLabels.data());
+            emitInstFastCall2K(build, pc, i, instLabels.data());
             break;
         case LOP_FORNPREP:
             emitInstForNPrep(build, pc, i, instLabels.data());
@@ -220,6 +257,12 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
         case LOP_ORK:
             emitInstOrK(build, pc);
             break;
+        case LOP_GETIMPORT:
+            emitInstGetImport(build, pc, instFallbacks[i]);
+            break;
+        case LOP_CONCAT:
+            emitInstConcat(build, pc, i, instLabels.data());
+            break;
         default:
             emitFallback(build, data, op, i);
             break;
@@ -229,6 +272,145 @@ static NativeProto* assembleFunction(AssemblyBuilderX64& build, NativeState& dat
         LUAU_ASSERT(i <= proto->sizecode);
     }
 
+    size_t textSize = build.text.size();
+    uint32_t codeSize = build.getCodeSize();
+
+    if (options.annotator && !options.skipOutlinedCode)
+        build.logAppend("; outlined code\n");
+
+    for (int i = 0, instid = 0; i < proto->sizecode; ++instid)
+    {
+        const Instruction* pc = &proto->code[i];
+        LuauOpcode op = LuauOpcode(LUAU_INSN_OP(*pc));
+
+        int nexti = i + getOpLength(op);
+        LUAU_ASSERT(nexti <= proto->sizecode);
+
+        if (instFallbacks[i].id == 0)
+        {
+            i = nexti;
+            continue;
+        }
+
+        if (options.annotator && !options.skipOutlinedCode)
+            options.annotator(options.annotatorContext, build.text, proto->bytecodeid, instid);
+
+        build.setLabel(instFallbacks[i]);
+
+        switch (op)
+        {
+        case LOP_GETIMPORT:
+            emitInstGetImportFallback(build, pc, i);
+            break;
+        case LOP_GETTABLE:
+            emitInstGetTableFallback(build, pc, i);
+            break;
+        case LOP_SETTABLE:
+            emitInstSetTableFallback(build, pc, i);
+            break;
+        case LOP_GETTABLEN:
+            emitInstGetTableNFallback(build, pc, i);
+            break;
+        case LOP_SETTABLEN:
+            emitInstSetTableNFallback(build, pc, i);
+            break;
+        case LOP_JUMPIFEQ:
+            emitInstJumpIfEqFallback(build, pc, i, instLabels.data(), /* not_ */ false);
+            break;
+        case LOP_JUMPIFLE:
+            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::LessEqual);
+            break;
+        case LOP_JUMPIFLT:
+            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::Less);
+            break;
+        case LOP_JUMPIFNOTEQ:
+            emitInstJumpIfEqFallback(build, pc, i, instLabels.data(), /* not_ */ true);
+            break;
+        case LOP_JUMPIFNOTLE:
+            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::NotLessEqual);
+            break;
+        case LOP_JUMPIFNOTLT:
+            emitInstJumpIfCondFallback(build, pc, i, instLabels.data(), Condition::NotLess);
+            break;
+        case LOP_ADD:
+            emitInstBinaryFallback(build, pc, i, TM_ADD);
+            break;
+        case LOP_SUB:
+            emitInstBinaryFallback(build, pc, i, TM_SUB);
+            break;
+        case LOP_MUL:
+            emitInstBinaryFallback(build, pc, i, TM_MUL);
+            break;
+        case LOP_DIV:
+            emitInstBinaryFallback(build, pc, i, TM_DIV);
+            break;
+        case LOP_MOD:
+            emitInstBinaryFallback(build, pc, i, TM_MOD);
+            break;
+        case LOP_POW:
+            emitInstBinaryFallback(build, pc, i, TM_POW);
+            break;
+        case LOP_ADDK:
+            emitInstBinaryKFallback(build, pc, i, TM_ADD);
+            break;
+        case LOP_SUBK:
+            emitInstBinaryKFallback(build, pc, i, TM_SUB);
+            break;
+        case LOP_MULK:
+            emitInstBinaryKFallback(build, pc, i, TM_MUL);
+            break;
+        case LOP_DIVK:
+            emitInstBinaryKFallback(build, pc, i, TM_DIV);
+            break;
+        case LOP_MODK:
+            emitInstBinaryKFallback(build, pc, i, TM_MOD);
+            break;
+        case LOP_POWK:
+            emitInstBinaryKFallback(build, pc, i, TM_POW);
+            break;
+        case LOP_MINUS:
+            emitInstMinusFallback(build, pc, i);
+            break;
+        case LOP_LENGTH:
+            emitInstLengthFallback(build, pc, i);
+            break;
+        case LOP_GETGLOBAL:
+            // TODO: luaV_gettable + cachedslot update instead of full fallback
+            emitFallback(build, data, op, i);
+            break;
+        case LOP_SETGLOBAL:
+            // TODO: luaV_settable + cachedslot update instead of full fallback
+            emitFallback(build, data, op, i);
+            break;
+        case LOP_GETTABLEKS:
+            // Full fallback required for LOP_GETTABLEKS because 'luaV_gettable' doesn't handle builtin vector field access
+            // It is also required to perform cached slot update
+            // TODO: extra fast-paths could be lowered before the full fallback
+            emitFallback(build, data, op, i);
+            break;
+        case LOP_SETTABLEKS:
+            // TODO: luaV_settable + cachedslot update instead of full fallback
+            emitFallback(build, data, op, i);
+            break;
+        default:
+            LUAU_ASSERT(!"Expected fallback for instruction");
+        }
+
+        // Jump back to the next instruction handler
+        if (nexti < proto->sizecode)
+            build.jmp(instLabels[nexti]);
+
+        i = nexti;
+    }
+
+    // Truncate assembly output if we don't care for outlined code part
+    if (options.skipOutlinedCode)
+    {
+        build.text.resize(textSize);
+
+        build.logAppend("; skipping %u bytes of outlined code\n", build.getCodeSize() - codeSize);
+    }
+
     result->instTargets = new uintptr_t[proto->sizecode];
 
     for (int i = 0; i < proto->sizecode; i++)
@@ -392,7 +574,7 @@ void compile(lua_State* L, int idx)
     // Skip protos that have been compiled during previous invocations of CodeGen::compile
     for (Proto* p : protos)
         if (p && getProtoExecData(p) == nullptr)
-            results.push_back(assembleFunction(build, *data, p));
+            results.push_back(assembleFunction(build, *data, p, {}));
 
     build.finalize();
 
@@ -420,15 +602,15 @@ void compile(lua_State* L, int idx)
         setProtoExecData(result->proto, result);
 }
 
-std::string getAssemblyText(lua_State* L, int idx)
+std::string getAssembly(lua_State* L, int idx, AssemblyOptions options)
 {
     LUAU_ASSERT(lua_isLfunction(L, idx));
     const TValue* func = luaA_toobject(L, idx);
 
-    AssemblyBuilderX64 build(/* logText= */ true);
+    AssemblyBuilderX64 build(/* logText= */ !options.outputBinary);
+
     NativeState data;
     initFallbackTable(data);
-    initInstructionNames(data);
 
     std::vector<Proto*> protos;
     gatherFunctions(protos, clvalue(func)->l.p);
@@ -436,13 +618,16 @@ std::string getAssemblyText(lua_State* L, int idx)
     for (Proto* p : protos)
         if (p)
         {
-            NativeProto* nativeProto = assembleFunction(build, data, p);
+            NativeProto* nativeProto = assembleFunction(build, data, p, options);
             destroyNativeProto(nativeProto);
         }
 
     build.finalize();
 
-    return build.text;
+    if (options.outputBinary)
+        return std::string(build.code.begin(), build.code.end()) + std::string(build.data.begin(), build.data.end());
+    else
+        return build.text;
 }
 
 } // namespace CodeGen

CodeGen/src/CodeGenX64.cpp

@@ -48,7 +48,7 @@ bool initEntryFunction(NativeState& data)
 
     unwind.start();
 
-    if (getCurrentX64ABI() == X64ABI::Windows)
+    if (build.abi == ABIX64::Windows)
     {
         // Place arguments in home space
         build.mov(qword[rsp + 16], rArg2);
@@ -121,7 +121,7 @@ bool initEntryFunction(NativeState& data)
     build.pop(rbp);
     build.pop(rbx);
 
-    if (getCurrentX64ABI() == X64ABI::Windows)
+    if (build.abi == ABIX64::Windows)
     {
         build.pop(rsi);
         build.pop(rdi);

CodeGen/src/CustomExecUtils.h

@@ -126,20 +126,5 @@ inline int getOpLength(LuauOpcode op)
     }
 }
 
-enum class X64ABI
-{
-    Windows,
-    SystemV,
-};
-
-inline X64ABI getCurrentX64ABI()
-{
-#if defined(_WIN32)
-    return X64ABI::Windows;
-#else
-    return X64ABI::SystemV;
-#endif
-}
-
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/EmitCommonX64.cpp

@@ -64,6 +64,7 @@ void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs,
 void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, Condition cond, Label& label, int pcpos)
 {
     emitSetSavedPc(build, pcpos + 1);
+
     build.mov(rArg1, rState);
     build.lea(rArg2, luauRegValue(ra));
     build.lea(rArg3, luauRegValue(rb));
@@ -83,6 +84,27 @@ void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, Condition c
         cond == Condition::NotLessEqual || cond == Condition::NotLess || cond == Condition::NotEqual ? Condition::Zero : Condition::NotZero, label);
 }
 
+RegisterX64 getTableNodeAtCachedSlot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int pcpos)
+{
+    RegisterX64 node = rdx;
+
+    LUAU_ASSERT(tmp != node);
+    LUAU_ASSERT(table != node);
+
+    build.mov(node, qword[table + offsetof(Table, node)]);
+
+    // compute cached slot
+    build.mov(tmp, sCode);
+    build.movzx(dwordReg(tmp), byte[tmp + pcpos * sizeof(Instruction) + kOffsetOfInstructionC]);
+    build.and_(byteReg(tmp), byte[table + offsetof(Table, nodemask8)]);
+
+    // LuaNode* n = &h->node[slot];
+    build.shl(dwordReg(tmp), kLuaNodeSizeLog2);
+    build.add(node, tmp);
+
+    return node;
+}
+
 void convertNumberToIndexOrJump(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 numd, RegisterX64 numi, int ri, Label& label)
 {
     LUAU_ASSERT(numi.size == SizeX64::dword);
@@ -105,7 +127,7 @@ void callArithHelper(AssemblyBuilderX64& build, int ra, int rb, OperandX64 c, in
 {
     emitSetSavedPc(build, pcpos + 1);
 
-    if (getCurrentX64ABI() == X64ABI::Windows)
+    if (build.abi == ABIX64::Windows)
         build.mov(sArg5, tm);
     else
         build.mov(rArg5, tm);
@@ -168,16 +190,17 @@ void callSetTable(AssemblyBuilderX64& build, int rb, OperandX64 c, int ra, int p
     emitUpdateBase(build);
 }
 
-void callBarrierTable(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int ra, Label& skip)
+// works for luaC_barriertable, luaC_barrierf
+static void callBarrierImpl(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 object, int ra, Label& skip, int contextOffset)
 {
-    LUAU_ASSERT(tmp != table);
+    LUAU_ASSERT(tmp != object);
 
     // iscollectable(ra)
     build.cmp(luauRegTag(ra), LUA_TSTRING);
     build.jcc(Condition::Less, skip);
 
-    // isblack(obj2gco(h))
+    // isblack(obj2gco(o))
-    build.test(byte[table + offsetof(GCheader, marked)], bitmask(BLACKBIT));
+    build.test(byte[object + offsetof(GCheader, marked)], bitmask(BLACKBIT));
     build.jcc(Condition::Zero, skip);
 
     // iswhite(gcvalue(ra))
@@ -185,11 +208,52 @@ void callBarrierTable(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 ta
     build.test(byte[tmp + offsetof(GCheader, marked)], bit2mask(WHITE0BIT, WHITE1BIT));
     build.jcc(Condition::Zero, skip);
 
-    LUAU_ASSERT(table != rArg3);
+    LUAU_ASSERT(object != rArg3);
     build.mov(rArg3, tmp);
-    build.mov(rArg2, table);
+    build.mov(rArg2, object);
     build.mov(rArg1, rState);
-    build.call(qword[rNativeContext + offsetof(NativeContext, luaC_barriertable)]);
+    build.call(qword[rNativeContext + contextOffset]);
+}
+
+void callBarrierTable(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int ra, Label& skip)
+{
+    callBarrierImpl(build, tmp, table, ra, skip, offsetof(NativeContext, luaC_barriertable));
+}
+
+void callBarrierObject(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 object, int ra, Label& skip)
+{
+    callBarrierImpl(build, tmp, object, ra, skip, offsetof(NativeContext, luaC_barrierf));
+}
+
+void callBarrierTableFast(AssemblyBuilderX64& build, RegisterX64 table, Label& skip)
+{
+    // isblack(obj2gco(t))
+    build.test(byte[table + offsetof(GCheader, marked)], bitmask(BLACKBIT));
+    build.jcc(Condition::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.mov(rArg1, rState);
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaC_barrierback)]);
+}
+
+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);
+
+    if (savepc)
+        emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rArg1, rState);
+    build.mov(rArg2, 1);
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaC_step)]);
+
+    emitUpdateBase(build);
 }
 
 void emitExit(AssemblyBuilderX64& build, bool continueInVm)
@@ -231,7 +295,7 @@ void emitInterrupt(AssemblyBuilderX64& build, int pcpos)
     // Call interrupt
     // TODO: This code should move to the end of the function, or even be outlined so that it can be shared by multiple interruptible instructions
     build.mov(rArg1, rState);
-    build.mov(rArg2d, -1);
+    build.mov(dwordReg(rArg2), -1); // function accepts 'int' here and using qword reg would've forced 8 byte constant here
     build.call(r8);
 
     // Check if we need to exit

CodeGen/src/EmitCommonX64.h

@@ -35,11 +35,11 @@ constexpr RegisterX64 rConstants = r12;     // TValue* k
 constexpr OperandX64 sClosure = qword[rbp + 0]; // Closure* cl
 constexpr OperandX64 sCode = qword[rbp + 8];    // Instruction* code
 
+// TODO: These should be replaced with a portable call function that checks the ABI at runtime and reorders moves accordingly to avoid conflicts
 #if defined(_WIN32)
 
 constexpr RegisterX64 rArg1 = rcx;
 constexpr RegisterX64 rArg2 = rdx;
-constexpr RegisterX64 rArg2d = edx;
 constexpr RegisterX64 rArg3 = r8;
 constexpr RegisterX64 rArg4 = r9;
 constexpr RegisterX64 rArg5 = noreg;
@@ -51,7 +51,6 @@ constexpr OperandX64 sArg6 = qword[rsp + 40];
 
 constexpr RegisterX64 rArg1 = rdi;
 constexpr RegisterX64 rArg2 = rsi;
-constexpr RegisterX64 rArg2d = esi;
 constexpr RegisterX64 rArg3 = rdx;
 constexpr RegisterX64 rArg4 = rcx;
 constexpr RegisterX64 rArg5 = r8;
@@ -62,6 +61,11 @@ constexpr OperandX64 sArg6 = noreg;
 #endif
 
 constexpr unsigned kTValueSizeLog2 = 4;
+constexpr unsigned kLuaNodeSizeLog2 = 5;
+constexpr unsigned kLuaNodeTagMask = 0xf;
+
+constexpr unsigned kOffsetOfLuaNodeTag = 12; // offsetof cannot be used on a bit field
+constexpr unsigned kOffsetOfInstructionC = 3;
 
 inline OperandX64 luauReg(int ri)
 {
@@ -88,11 +92,26 @@ inline OperandX64 luauConstant(int ki)
     return xmmword[rConstants + ki * sizeof(TValue)];
 }
 
+inline OperandX64 luauConstantTag(int ki)
+{
+    return dword[rConstants + ki * sizeof(TValue) + offsetof(TValue, tt)];
+}
+
 inline OperandX64 luauConstantValue(int ki)
 {
     return qword[rConstants + ki * sizeof(TValue) + offsetof(TValue, value)];
 }
 
+inline OperandX64 luauNodeKeyValue(RegisterX64 node)
+{
+    return qword[node + offsetof(LuaNode, key) + offsetof(TKey, value)];
+}
+
+inline OperandX64 luauNodeValue(RegisterX64 node)
+{
+    return xmmword[node + offsetof(LuaNode, val)];
+}
+
 inline void setLuauReg(AssemblyBuilderX64& build, RegisterX64 tmp, int ri, OperandX64 op)
 {
     LUAU_ASSERT(op.cat == CategoryX64::mem);
@@ -101,6 +120,14 @@ inline void setLuauReg(AssemblyBuilderX64& build, RegisterX64 tmp, int ri, Opera
     build.vmovups(luauReg(ri), tmp);
 }
 
+inline void setNodeValue(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 op, int ri)
+{
+    LUAU_ASSERT(op.cat == CategoryX64::mem);
+
+    build.vmovups(tmp, luauReg(ri));
+    build.vmovups(op, tmp);
+}
+
 inline void jumpIfTagIs(AssemblyBuilderX64& build, int ri, lua_Type tag, Label& label)
 {
     build.cmp(luauRegTag(ri), tag);
@@ -153,9 +180,37 @@ inline void jumpIfTableIsReadOnly(AssemblyBuilderX64& build, RegisterX64 table,
     build.jcc(Condition::NotEqual, label);
 }
 
+inline void jumpIfNodeKeyTagIsNot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 node, lua_Type tag, Label& label)
+{
+    tmp.size = SizeX64::dword;
+
+    build.mov(tmp, dword[node + offsetof(LuaNode, key) + kOffsetOfLuaNodeTag]);
+    build.and_(tmp, kLuaNodeTagMask);
+    build.cmp(tmp, tag);
+    build.jcc(Condition::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);
+}
+
+inline void jumpIfNodeKeyNotInExpectedSlot(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 node, OperandX64 expectedKey, Label& label)
+{
+    jumpIfNodeKeyTagIsNot(build, tmp, node, LUA_TSTRING, label);
+
+    build.mov(tmp, expectedKey);
+    build.cmp(tmp, luauNodeKeyValue(node));
+    build.jcc(Condition::NotEqual, label);
+
+    jumpIfNodeValueTagIs(build, node, LUA_TNIL, label);
+}
+
 void jumpOnNumberCmp(AssemblyBuilderX64& build, RegisterX64 tmp, OperandX64 lhs, OperandX64 rhs, Condition cond, Label& label);
 void jumpOnAnyCmpFallback(AssemblyBuilderX64& build, int ra, int rb, Condition 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);
 
 void callArithHelper(AssemblyBuilderX64& build, int ra, int rb, OperandX64 c, int pcpos, TMS tm);
@@ -164,6 +219,9 @@ void callPrepareForN(AssemblyBuilderX64& build, int limit, int step, int init, i
 void callGetTable(AssemblyBuilderX64& build, int rb, OperandX64 c, int ra, int pcpos);
 void callSetTable(AssemblyBuilderX64& build, int rb, OperandX64 c, int ra, int pcpos);
 void callBarrierTable(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 table, int ra, Label& skip);
+void callBarrierObject(AssemblyBuilderX64& build, RegisterX64 tmp, RegisterX64 object, int ra, Label& skip);
+void callBarrierTableFast(AssemblyBuilderX64& build, RegisterX64 table, Label& skip);
+void callCheckGc(AssemblyBuilderX64& build, int pcpos, bool savepc, Label& skip);
 
 void emitExit(AssemblyBuilderX64& build, bool continueInVm);
 void emitUpdateBase(AssemblyBuilderX64& build);

CodeGen/src/EmitInstructionX64.cpp

@@ -11,19 +11,22 @@
 #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
 {
 
-void emitInstLoadNil(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc)
+void emitInstLoadNil(AssemblyBuilderX64& build, const Instruction* pc)
 {
     int ra = LUAU_INSN_A(*pc);
 
     build.mov(luauRegTag(ra), LUA_TNIL);
 }
 
-void emitInstLoadB(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr)
+void emitInstLoadB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
 
@@ -34,7 +37,7 @@ void emitInstLoadB(AssemblyBuilderX64& build, NativeState& data, const Instructi
         build.jmp(labelarr[pcpos + target + 1]);
 }
 
-void emitInstLoadN(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc)
+void emitInstLoadN(AssemblyBuilderX64& build, const Instruction* pc)
 {
     int ra = LUAU_INSN_A(*pc);
 
@@ -43,7 +46,7 @@ void emitInstLoadN(AssemblyBuilderX64& build, NativeState& data, const Instructi
     build.mov(luauRegTag(ra), LUA_TNUMBER);
 }
 
-void emitInstLoadK(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k)
+void emitInstLoadK(AssemblyBuilderX64& build, const Instruction* pc)
 {
     int ra = LUAU_INSN_A(*pc);
 
@@ -51,7 +54,16 @@ void emitInstLoadK(AssemblyBuilderX64& build, NativeState& data, const Instructi
     build.vmovups(luauReg(ra), xmm0);
 }
 
-void emitInstMove(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc)
+void emitInstLoadKX(AssemblyBuilderX64& build, const Instruction* pc)
+{
+    int ra = LUAU_INSN_A(*pc);
+    uint32_t aux = pc[1];
+
+    build.vmovups(xmm0, luauConstant(aux));
+    build.vmovups(luauReg(ra), xmm0);
+}
+
+void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
@@ -60,19 +72,19 @@ void emitInstMove(AssemblyBuilderX64& build, NativeState& data, const Instructio
     build.vmovups(luauReg(ra), xmm0);
 }
 
-void emitInstJump(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr)
+void emitInstJump(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     build.jmp(labelarr[pcpos + LUAU_INSN_D(*pc) + 1]);
 }
 
-void emitInstJumpBack(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr)
+void emitInstJumpBack(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     emitInterrupt(build, pcpos);
 
     build.jmp(labelarr[pcpos + LUAU_INSN_D(*pc) + 1]);
 }
 
-void emitInstJumpIf(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
+void emitInstJumpIf(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
 {
     int ra = LUAU_INSN_A(*pc);
 
@@ -85,14 +97,13 @@ void emitInstJumpIf(AssemblyBuilderX64& build, NativeState& data, const Instruct
         jumpIfTruthy(build, ra, target, exit);
 }
 
-void emitInstJumpIfEq(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
+void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = pc[1];
 
     Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
     Label& exit = labelarr[pcpos + 2];
-    Label any;
 
     build.mov(eax, luauRegTag(ra));
     build.cmp(eax, luauRegTag(rb));
@@ -100,47 +111,50 @@ void emitInstJumpIfEq(AssemblyBuilderX64& build, NativeState& data, const Instru
 
     // fast-path: number
     build.cmp(eax, LUA_TNUMBER);
-    build.jcc(Condition::NotEqual, any);
+    build.jcc(Condition::NotEqual, fallback);
 
     jumpOnNumberCmp(build, xmm0, luauRegValue(ra), luauRegValue(rb), Condition::NotEqual, not_ ? target : exit);
-    build.jmp(not_ ? exit : target);
 
-    // slow-path
+    if (!not_)
-    // TODO: move to the end of the function
+        build.jmp(target);
-    build.setLabel(any);
-    jumpOnAnyCmpFallback(build, ra, rb, not_ ? Condition::NotEqual : Condition::Equal, target, pcpos);
 }
 
-void emitInstJumpIfCond(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, Condition cond)
+void emitInstJumpIfEqFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_)
+{
+    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+
+    jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], not_ ? Condition::NotEqual : Condition::Equal, target, pcpos);
+}
+
+void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = pc[1];
 
     Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
-    Label& exit = labelarr[pcpos + 2];
-    Label any;
 
     // fast-path: number
-    jumpIfTagIsNot(build, ra, LUA_TNUMBER, any);
+    jumpIfTagIsNot(build, ra, LUA_TNUMBER, fallback);
-    jumpIfTagIsNot(build, rb, LUA_TNUMBER, any);
+    jumpIfTagIsNot(build, rb, LUA_TNUMBER, fallback);
 
     jumpOnNumberCmp(build, xmm0, luauRegValue(ra), luauRegValue(rb), cond, target);
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(any);
-    jumpOnAnyCmpFallback(build, ra, rb, cond, target, pcpos);
 }
 
-void emitInstJumpX(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr)
+void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond)
+{
+    Label& target = labelarr[pcpos + LUAU_INSN_D(*pc) + 1];
+
+    jumpOnAnyCmpFallback(build, LUAU_INSN_A(*pc), pc[1], cond, target, pcpos);
+}
+
+void emitInstJumpX(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     emitInterrupt(build, pcpos);
 
     build.jmp(labelarr[pcpos + LUAU_INSN_E(*pc) + 1]);
 }
 
-void emitInstJumpxEqNil(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
+void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
     bool not_ = (pc[1] & 0x80000000) != 0;
@@ -151,7 +165,7 @@ void emitInstJumpxEqNil(AssemblyBuilderX64& build, NativeState& data, const Inst
     build.jcc(not_ ? Condition::NotEqual : Condition::Equal, target);
 }
 
-void emitInstJumpxEqB(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
+void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
     uint32_t aux = pc[1];
@@ -166,7 +180,7 @@ void emitInstJumpxEqB(AssemblyBuilderX64& build, NativeState& data, const Instru
     build.jcc((aux & 0x1) ^ not_ ? Condition::NotZero : Condition::Zero, target);
 }
 
-void emitInstJumpxEqN(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
+void emitInstJumpxEqN(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
     uint32_t aux = pc[1];
@@ -192,7 +206,7 @@ void emitInstJumpxEqN(AssemblyBuilderX64& build, NativeState& data, const Instru
     }
 }
 
-void emitInstJumpxEqS(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
+void emitInstJumpxEqS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     int ra = LUAU_INSN_A(*pc);
     uint32_t aux = pc[1];
@@ -208,14 +222,12 @@ void emitInstJumpxEqS(AssemblyBuilderX64& build, NativeState& data, const Instru
     build.jcc(not_ ? Condition::NotEqual : Condition::Equal, target);
 }
 
-static void emitInstBinaryNumeric(AssemblyBuilderX64& build, int ra, int rb, int rc, OperandX64 opc, int pcpos, TMS tm)
+static void emitInstBinaryNumeric(AssemblyBuilderX64& build, int ra, int rb, int rc, OperandX64 opc, int pcpos, TMS tm, Label& fallback)
 {
-    Label common, exit;
+    jumpIfTagIsNot(build, rb, LUA_TNUMBER, fallback);
-
-    jumpIfTagIsNot(build, rb, LUA_TNUMBER, common);
 
     if (rc != -1 && rc != rb)
-        jumpIfTagIsNot(build, rc, LUA_TNUMBER, common);
+        jumpIfTagIsNot(build, rc, LUA_TNUMBER, fallback);
 
     // fast-path: number
     build.vmovsd(xmm0, luauRegValue(rb));
@@ -254,81 +266,35 @@ static void emitInstBinaryNumeric(AssemblyBuilderX64& build, int ra, int rb, int
 
     if (ra != rb && ra != rc)
         build.mov(luauRegTag(ra), LUA_TNUMBER);
-
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(common);
-    callArithHelper(build, ra, rb, opc, pcpos, tm);
-
-    build.setLabel(exit);
 }
 
-void emitInstAdd(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstBinary(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm, Label& fallback)
 {
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_ADD);
+    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, tm, fallback);
 }
 
-void emitInstSub(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstBinaryFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm)
 {
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_SUB);
+    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, tm);
 }
 
-void emitInstMul(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstBinaryK(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm, Label& fallback)
 {
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_MUL);
+    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, tm, fallback);
 }
 
-void emitInstDiv(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstBinaryKFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm)
 {
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_DIV);
+    callArithHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauConstantValue(LUAU_INSN_C(*pc)), pcpos, tm);
 }
 
-void emitInstMod(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label& fallback)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_MOD);
-}
-
-void emitInstPow(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), LUAU_INSN_C(*pc), luauRegValue(LUAU_INSN_C(*pc)), pcpos, TM_POW);
-}
-
-void emitInstAddK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_ADD);
-}
-
-void emitInstSubK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_SUB);
-}
-
-void emitInstMulK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_MUL);
-}
-
-void emitInstDivK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_DIV);
-}
-
-void emitInstModK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
-{
-    emitInstBinaryNumeric(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), -1, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_MOD);
-}
-
-void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
     double kv = nvalue(&k[LUAU_INSN_C(*pc)]);
 
-    Label common, exit;
+    jumpIfTagIsNot(build, rb, LUA_TNUMBER, fallback);
-
-    jumpIfTagIsNot(build, rb, LUA_TNUMBER, common);
 
     // fast-path: number
     build.vmovsd(xmm0, luauRegValue(rb));
@@ -357,15 +323,6 @@ void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue
 
     if (ra != rb)
         build.mov(luauRegTag(ra), LUA_TNUMBER);
-
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(common);
-    callArithHelper(build, ra, rb, luauConstantValue(LUAU_INSN_C(*pc)), pcpos, TM_POW);
-
-    build.setLabel(exit);
 }
 
 void emitInstNot(AssemblyBuilderX64& build, const Instruction* pc)
@@ -388,14 +345,12 @@ void emitInstNot(AssemblyBuilderX64& build, const Instruction* pc)
     build.mov(luauRegTag(ra), LUA_TBOOLEAN);
 }
 
-void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
 
-    Label any, exit;
+    jumpIfTagIsNot(build, rb, LUA_TNUMBER, fallback);
-
-    jumpIfTagIsNot(build, rb, LUA_TNUMBER, any);
 
     // fast-path: number
     build.vxorpd(xmm0, xmm0, xmm0);
@@ -404,29 +359,23 @@ void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
 
     if (ra != rb)
         build.mov(luauRegTag(ra), LUA_TNUMBER);
-
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(any);
-    callArithHelper(build, ra, rb, luauRegValue(rb), pcpos, TM_UNM);
-
-    build.setLabel(exit);
 }
 
-void emitInstLength(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);
+}
+
+void emitInstLength(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
 
-    Label any, exit;
+    jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
-
-    jumpIfTagIsNot(build, rb, LUA_TTABLE, any);
 
     // fast-path: table without __len
     build.mov(rArg1, luauRegValue(rb));
-    jumpIfMetatablePresent(build, rArg1, any);
+    jumpIfMetatablePresent(build, rArg1, fallback);
 
     // First argument (Table*) is already in rArg1
     build.call(qword[rNativeContext + offsetof(NativeContext, luaH_getn)]);
@@ -434,14 +383,154 @@ void emitInstLength(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
     build.vcvtsi2sd(xmm0, xmm0, eax);
     build.vmovsd(luauRegValue(ra), xmm0);
     build.mov(luauRegTag(ra), LUA_TNUMBER);
-    build.jmp(exit);
+}
 
-    // slow-path
+void emitInstLengthFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
-    // TODO: move to the end of the function
+{
-    build.setLabel(any);
+    callLengthHelper(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), pcpos);
-    callLengthHelper(build, ra, rb, pcpos);
+}
 
-    build.setLabel(exit);
+void emitInstNewTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int b = LUAU_INSN_B(*pc);
+    uint32_t aux = pc[1];
+
+    Label& exit = labelarr[pcpos + 2];
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rArg1, rState);
+    build.mov(rArg2, aux);
+    build.mov(rArg3, b == 0 ? 0 : 1 << (b - 1));
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaH_new)]);
+    build.mov(luauRegValue(ra), rax);
+    build.mov(luauRegTag(ra), LUA_TTABLE);
+
+    callCheckGc(build, pcpos, /* savepc = */ false, exit);
+}
+
+void emitInstDupTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+
+    Label& exit = labelarr[pcpos + 1];
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rArg1, rState);
+    build.mov(rArg2, luauConstantValue(LUAU_INSN_D(*pc)));
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaH_clone)]);
+    build.mov(luauRegValue(ra), rax);
+    build.mov(luauRegTag(ra), LUA_TTABLE);
+
+    callCheckGc(build, pcpos, /* savepc= */ false, exit);
+}
+
+void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int rb = LUAU_INSN_B(*pc);
+    int c = LUAU_INSN_C(*pc) - 1;
+    uint32_t index = pc[1];
+
+    Label& exit = labelarr[pcpos + 2];
+
+    OperandX64 last = index + c - 1;
+
+    // Using non-volatile 'rbx' for dynamic 'c' value (for LUA_MULTRET) to skip later recomputation
+    // We also keep 'c' scaled by sizeof(TValue) here as it helps in the loop below
+    RegisterX64 cscaled = rbx;
+
+    if (c == LUA_MULTRET)
+    {
+        RegisterX64 tmp = rax;
+
+        // c = L->top - rb
+        build.mov(cscaled, qword[rState + offsetof(lua_State, top)]);
+        build.lea(tmp, luauRegValue(rb));
+        build.sub(cscaled, tmp); // Using byte difference
+
+        // L->top = L->ci->top
+        build.mov(tmp, qword[rState + offsetof(lua_State, ci)]);
+        build.mov(tmp, qword[tmp + offsetof(CallInfo, top)]);
+        build.mov(qword[rState + offsetof(lua_State, top)], tmp);
+
+        // last = index + c - 1;
+        last = edx;
+        build.mov(last, dwordReg(cscaled));
+        build.shr(last, kTValueSizeLog2);
+        build.add(last, index - 1);
+    }
+
+    Label skipResize;
+
+    RegisterX64 table = rax;
+
+    build.mov(table, luauRegValue(ra));
+
+    // Resize if h->sizearray < last
+    build.cmp(dword[table + offsetof(Table, sizearray)], last);
+    build.jcc(Condition::NotBelow, skipResize);
+
+    // Argument setup reordered to avoid conflicts
+    LUAU_ASSERT(rArg3 != table);
+    build.mov(dwordReg(rArg3), last);
+    build.mov(rArg2, table);
+    build.mov(rArg1, rState);
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaH_resizearray)]);
+    build.mov(table, luauRegValue(ra)); // Reload cloberred register value
+
+    build.setLabel(skipResize);
+
+    RegisterX64 arrayDst = rdx;
+    RegisterX64 offset = rcx;
+
+    build.mov(arrayDst, qword[table + offsetof(Table, array)]);
+
+    const int kUnrollSetListLimit = 4;
+
+    if (c != LUA_MULTRET && c <= kUnrollSetListLimit)
+    {
+        for (int i = 0; i < c; ++i)
+        {
+            // setobj2t(L, &array[index + i - 1], rb + i);
+            build.vmovups(xmm0, luauRegValue(rb + i));
+            build.vmovups(xmmword[arrayDst + (index + i - 1) * sizeof(TValue)], xmm0);
+        }
+    }
+    else
+    {
+        LUAU_ASSERT(c != 0);
+
+        build.xor_(offset, offset);
+        if (index != 1)
+            build.add(arrayDst, (index - 1) * sizeof(TValue));
+
+        Label repeatLoop, endLoop;
+        OperandX64 limit = c == LUA_MULTRET ? cscaled : OperandX64(c * sizeof(TValue));
+
+        // If c is static, we will always do at least one iteration
+        if (c == LUA_MULTRET)
+        {
+            build.cmp(offset, limit);
+            build.jcc(Condition::NotBelow, endLoop);
+        }
+
+        build.setLabel(repeatLoop);
+
+        // setobj2t(L, &array[index + i - 1], rb + i);
+        build.vmovups(xmm0, xmmword[offset + rBase + rb * sizeof(TValue)]); // luauReg(rb) unwrapped to add offset
+        build.vmovups(xmmword[offset + arrayDst], xmm0);
+
+        build.add(offset, sizeof(TValue));
+        build.cmp(offset, limit);
+        build.jcc(Condition::Below, repeatLoop);
+
+        build.setLabel(endLoop);
+    }
+
+    callBarrierTableFast(build, table, exit);
 }
 
 void emitInstGetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
@@ -468,6 +557,45 @@ void emitInstGetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     build.vmovups(luauReg(ra), xmm0);
 }
 
+void emitInstSetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int up = LUAU_INSN_B(*pc);
+
+    RegisterX64 upval = rax;
+    RegisterX64 tmp = rcx;
+
+    build.mov(tmp, sClosure);
+    build.mov(upval, qword[tmp + offsetof(Closure, l.uprefs) + sizeof(TValue) * up + offsetof(TValue, value.gc)]);
+
+    build.mov(tmp, qword[upval + offsetof(UpVal, v)]);
+    build.vmovups(xmm0, luauReg(ra));
+    build.vmovups(xmmword[tmp], xmm0);
+
+    callBarrierObject(build, tmp, upval, ra, labelarr[pcpos + 1]);
+}
+
+void emitInstCloseUpvals(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+
+    Label& skip = labelarr[pcpos + 1];
+
+    // L->openupval != 0
+    build.mov(rax, qword[rState + offsetof(lua_State, openupval)]);
+    build.test(rax, rax);
+    build.jcc(Condition::Zero, skip);
+
+    // ra <= L->openuval->v
+    build.lea(rcx, qword[rBase + ra * sizeof(TValue)]);
+    build.cmp(rcx, qword[rax + offsetof(UpVal, v)]);
+    build.jcc(Condition::Above, skip);
+
+    build.mov(rArg2, rcx);
+    build.mov(rArg1, rState);
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaF_close)]);
+}
+
 static void emitInstFastCallN(
     AssemblyBuilderX64& build, const Instruction* pc, bool customParams, int customParamCount, OperandX64 customArgs, int pcpos, Label* labelarr)
 {
@@ -512,14 +640,14 @@ static void emitInstFastCallN(
     }
 
     // TODO: we can skip saving pc for some well-behaved builtins which we didn't inline
-    emitSetSavedPc(build, pcpos); // uses rax/rdx
+    emitSetSavedPc(build, pcpos + 1); // uses rax/rdx
 
     build.mov(rax, qword[rNativeContext + offsetof(NativeContext, luauF_table) + bfid * sizeof(luau_FastFunction)]);
 
     // 5th parameter (args) is left unset for LOP_FASTCALL1
     if (args.cat == CategoryX64::mem)
     {
-        if (getCurrentX64ABI() == X64ABI::Windows)
+        if (build.abi == ABIX64::Windows)
         {
             build.lea(rcx, args);
             build.mov(sArg5, rcx);
@@ -539,14 +667,14 @@ static void emitInstFastCallN(
         build.sub(rcx, rdx);
         build.shr(rcx, kTValueSizeLog2);
 
-        if (getCurrentX64ABI() == X64ABI::Windows)
+        if (build.abi == ABIX64::Windows)
             build.mov(sArg6, rcx);
         else
             build.mov(rArg6, rcx);
     }
     else
     {
-        if (getCurrentX64ABI() == X64ABI::Windows)
+        if (build.abi == ABIX64::Windows)
             build.mov(sArg6, nparams);
         else
             build.mov(rArg6, nparams);
@@ -594,7 +722,7 @@ void emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcp
     emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauRegValue(pc[1]), pcpos, labelarr);
 }
 
-void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr)
+void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
 {
     emitInstFastCallN(build, pc, /* customParams */ true, /* customParamCount */ 2, /* customArgs */ luauConstantValue(pc[1]), pcpos, labelarr);
 }
@@ -762,14 +890,12 @@ void emitInstOrK(AssemblyBuilderX64& build, const Instruction* pc)
     emitInstOrX(build, LUAU_INSN_A(*pc), LUAU_INSN_B(*pc), luauConstant(LUAU_INSN_C(*pc)));
 }
 
-void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
     int c = LUAU_INSN_C(*pc);
 
-    Label fallback, exit;
-
     jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
 
     RegisterX64 table = rcx;
@@ -783,27 +909,21 @@ void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcp
 
     build.mov(rax, qword[table + offsetof(Table, array)]);
     setLuauReg(build, xmm0, ra, xmmword[rax + c * sizeof(TValue)]);
-
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(fallback);
-    TValue n;
-    setnvalue(&n, c + 1);
-    callGetTable(build, rb, build.bytes(&n, sizeof(n)), ra, pcpos);
-
-    build.setLabel(exit);
 }
 
-void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstGetTableNFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+{
+    TValue n;
+    setnvalue(&n, LUAU_INSN_C(*pc) + 1);
+    callGetTable(build, LUAU_INSN_B(*pc), build.bytes(&n, sizeof(n)), LUAU_INSN_A(*pc), pcpos);
+}
+
+void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
     int c = LUAU_INSN_C(*pc);
 
-    Label fallback, exit;
-
     jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
 
     RegisterX64 table = rcx;
@@ -821,27 +941,22 @@ void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcp
     build.vmovups(xmm0, luauReg(ra));
     build.vmovups(xmmword[rax + c * sizeof(TValue)], xmm0);
 
-    callBarrierTable(build, rax, table, ra, exit);
+    callBarrierTable(build, rax, table, ra, labelarr[pcpos + 1]);
-    build.jmp(exit);
-
-    // slow-path
-    // TODO: move to the end of the function
-    build.setLabel(fallback);
-    TValue n;
-    setnvalue(&n, c + 1);
-    callSetTable(build, rb, build.bytes(&n, sizeof(n)), ra, pcpos);
-
-    build.setLabel(exit);
 }
 
-void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+void emitInstSetTableNFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+{
+    TValue n;
+    setnvalue(&n, LUAU_INSN_C(*pc) + 1);
+    callSetTable(build, LUAU_INSN_B(*pc), build.bytes(&n, sizeof(n)), LUAU_INSN_A(*pc), pcpos);
+}
+
+void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
     int rc = LUAU_INSN_C(*pc);
 
-    Label fallback, exit;
-
     jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
     jumpIfTagIsNot(build, rc, LUA_TNUMBER, fallback);
 
@@ -864,26 +979,19 @@ void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     build.mov(rdx, qword[table + offsetof(Table, array)]);
     build.shl(eax, kTValueSizeLog2);
     setLuauReg(build, xmm0, ra, xmmword[rdx + rax]);
-
-    build.jmp(exit);
-
-    build.setLabel(fallback);
-
-    // slow-path
-    // TODO: move to the end of the function
-    callGetTable(build, rb, luauRegValue(rc), ra, pcpos);
-
-    build.setLabel(exit);
 }
 
-void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+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);
+}
+
+void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
 {
     int ra = LUAU_INSN_A(*pc);
     int rb = LUAU_INSN_B(*pc);
     int rc = LUAU_INSN_C(*pc);
 
-    Label fallback, exit;
-
     jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
     jumpIfTagIsNot(build, rc, LUA_TNUMBER, fallback);
 
@@ -909,16 +1017,157 @@ void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpo
     build.vmovups(xmm0, luauReg(ra));
     build.vmovups(xmmword[rdx + rax], xmm0);
 
-    callBarrierTable(build, rdx, table, ra, exit);
+    callBarrierTable(build, rdx, table, ra, labelarr[pcpos + 1]);
-    build.jmp(exit);
+}
 
-    build.setLabel(fallback);
+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);
+}
 
-    // slow-path
+void emitInstGetImport(AssemblyBuilderX64& build, const Instruction* pc, Label& fallback)
-    // TODO: move to the end of the function
+{
-    callSetTable(build, rb, luauRegValue(rc), ra, pcpos);
+    int ra = LUAU_INSN_A(*pc);
+    int k = LUAU_INSN_D(*pc);
 
-    build.setLabel(exit);
+    jumpIfUnsafeEnv(build, rax, fallback);
+
+    // 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.vmovups(xmm0, luauConstant(k));
+    build.vmovups(luauReg(ra), xmm0);
+}
+
+void emitInstGetImportFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos)
+{
+    int ra = LUAU_INSN_A(*pc);
+    uint32_t aux = pc[1];
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    build.mov(rax, sClosure);
+
+    // luaV_getimport(L, cl->env, k, aux, /* propagatenil= */ false)
+    build.mov(rArg1, rState);
+    build.mov(rArg2, qword[rax + offsetof(Closure, env)]);
+    build.mov(rArg3, rConstants);
+    build.mov(rArg4, aux);
+
+    if (build.abi == ABIX64::Windows)
+        build.mov(sArg5, 0);
+    else
+        build.xor_(rArg5, rArg5);
+
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaV_getimport)]);
+
+    emitUpdateBase(build);
+
+    // setobj2s(L, ra, L->top - 1)
+    build.mov(rax, qword[rState + offsetof(lua_State, top)]);
+    build.sub(rax, sizeof(TValue));
+    build.vmovups(xmm0, xmmword[rax]);
+    build.vmovups(luauReg(ra), xmm0);
+
+    // L->top--
+    build.mov(qword[rState + offsetof(lua_State, top)], rax);
+}
+
+void emitInstGetTableKS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int rb = LUAU_INSN_B(*pc);
+    uint32_t aux = pc[1];
+
+    jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
+
+    RegisterX64 table = rcx;
+    build.mov(table, luauRegValue(rb));
+    RegisterX64 node = getTableNodeAtCachedSlot(build, rax, table, pcpos);
+
+    jumpIfNodeKeyNotInExpectedSlot(build, rax, node, luauConstantValue(aux), fallback);
+
+    setLuauReg(build, xmm0, ra, luauNodeValue(node));
+}
+
+void emitInstSetTableKS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int rb = LUAU_INSN_B(*pc);
+    uint32_t aux = pc[1];
+
+    jumpIfTagIsNot(build, rb, LUA_TTABLE, fallback);
+
+    RegisterX64 table = rcx;
+    build.mov(table, luauRegValue(rb));
+
+    // fast-path: set value at the expected slot
+    RegisterX64 node = getTableNodeAtCachedSlot(build, rax, table, pcpos);
+
+    jumpIfNodeKeyNotInExpectedSlot(build, rax, node, luauConstantValue(aux), fallback);
+    jumpIfTableIsReadOnly(build, table, fallback);
+
+    setNodeValue(build, xmm0, luauNodeValue(node), ra);
+
+    callBarrierTable(build, rax, table, ra, labelarr[pcpos + 2]);
+}
+
+void emitInstGetGlobal(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+    uint32_t aux = pc[1];
+
+    RegisterX64 table = rcx;
+    build.mov(rax, sClosure);
+    build.mov(table, qword[rax + offsetof(Closure, env)]);
+    RegisterX64 node = getTableNodeAtCachedSlot(build, rax, table, pcpos);
+
+    jumpIfNodeKeyNotInExpectedSlot(build, rax, node, luauConstantValue(aux), fallback);
+
+    setLuauReg(build, xmm0, ra, luauNodeValue(node));
+}
+
+void emitInstSetGlobal(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback)
+{
+    int ra = LUAU_INSN_A(*pc);
+    uint32_t aux = pc[1];
+
+    RegisterX64 table = rcx;
+    build.mov(rax, sClosure);
+    build.mov(table, qword[rax + offsetof(Closure, env)]);
+    RegisterX64 node = getTableNodeAtCachedSlot(build, rax, table, pcpos);
+
+    jumpIfNodeKeyNotInExpectedSlot(build, rax, node, luauConstantValue(aux), fallback);
+    jumpIfTableIsReadOnly(build, table, fallback);
+
+    setNodeValue(build, xmm0, luauNodeValue(node), ra);
+
+    callBarrierTable(build, rax, table, ra, labelarr[pcpos + 2]);
+}
+
+void emitInstConcat(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr)
+{
+    int ra = LUAU_INSN_A(*pc);
+    int rb = LUAU_INSN_B(*pc);
+    int rc = LUAU_INSN_C(*pc);
+
+    emitSetSavedPc(build, pcpos + 1);
+
+    // luaV_concat(L, c - b + 1, c)
+    build.mov(rArg1, rState);
+    build.mov(rArg2, rc - rb + 1);
+    build.mov(rArg3, rc);
+    build.call(qword[rNativeContext + offsetof(NativeContext, luaV_concat)]);
+
+    emitUpdateBase(build);
+
+    // setobj2s(L, ra, base + b)
+    build.vmovups(xmm0, luauReg(rb));
+    build.vmovups(luauReg(ra), xmm0);
+
+    callCheckGc(build, pcpos, /* savepc= */ false, labelarr[pcpos + 1]);
 }
 
 } // namespace CodeGen

CodeGen/src/EmitInstructionX64.h

@@ -3,6 +3,8 @@
 
 #include <stdint.h>
 
+#include "ltm.h"
+
 typedef uint32_t Instruction;
 typedef struct lua_TValue TValue;
 
@@ -16,40 +18,43 @@ enum class Condition;
 struct Label;
 struct NativeState;
 
-void emitInstLoadNil(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc);
+void emitInstLoadNil(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstLoadB(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstLoadB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstLoadN(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc);
+void emitInstLoadN(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstLoadK(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k);
+void emitInstLoadK(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstMove(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc);
+void emitInstLoadKX(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstJump(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstMove(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstJumpBack(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstJump(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstJumpIf(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
+void emitInstJumpBack(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstJumpIfEq(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
+void emitInstJumpIf(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
-void emitInstJumpIfCond(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr, Condition cond);
+void emitInstJumpIfEq(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_, Label& fallback);
-void emitInstJumpX(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstJumpIfEqFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, bool not_);
-void emitInstJumpxEqNil(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
+void emitInstJumpIfCond(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond, Label& fallback);
-void emitInstJumpxEqB(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
+void emitInstJumpIfCondFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Condition cond);
-void emitInstJumpxEqN(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
+void emitInstJumpX(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstJumpxEqS(AssemblyBuilderX64& build, NativeState& data, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
+void emitInstJumpxEqNil(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstAdd(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstJumpxEqB(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstSub(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstJumpxEqN(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
-void emitInstMul(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstJumpxEqS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstDiv(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstBinary(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm, Label& fallback);
-void emitInstMod(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstBinaryFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm);
-void emitInstPow(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstBinaryK(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm, Label& fallback);
-void emitInstAddK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
+void emitInstBinaryKFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, TMS tm);
-void emitInstSubK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
+void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label& fallback);
-void emitInstMulK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
-void emitInstDivK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
-void emitInstModK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
-void emitInstPowK(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos);
 void emitInstNot(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstMinus(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
-void emitInstLength(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstMinusFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstLength(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
+void emitInstLengthFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstNewTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstDupTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstSetList(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstGetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstSetUpval(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
+void emitInstCloseUpvals(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstFastCall1(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstFastCall2(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
-void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, const TValue* k, int pcpos, Label* labelarr);
+void emitInstFastCall2K(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstFastCall(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstForNPrep(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 void emitInstForNLoop(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
@@ -57,10 +62,21 @@ void emitInstAnd(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstAndK(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstOr(AssemblyBuilderX64& build, const Instruction* pc);
 void emitInstOrK(AssemblyBuilderX64& build, const Instruction* pc);
-void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstGetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
-void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstGetTableNFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
-void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstSetTableN(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
-void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstSetTableNFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstGetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
+void emitInstGetTableFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstSetTable(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitInstSetTableFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstGetImport(AssemblyBuilderX64& build, const Instruction* pc, Label& fallback);
+void emitInstGetImportFallback(AssemblyBuilderX64& build, const Instruction* pc, int pcpos);
+void emitInstGetTableKS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
+void emitInstSetTableKS(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitInstGetGlobal(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label& fallback);
+void emitInstSetGlobal(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr, Label& fallback);
+void emitInstConcat(AssemblyBuilderX64& build, const Instruction* pc, int pcpos, Label* labelarr);
 
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/NativeState.cpp

@@ -9,35 +9,12 @@
 #include "lbuiltins.h"
 #include "lgc.h"
 #include "ltable.h"
+#include "lfunc.h"
 #include "lvm.h"
 
 #include <math.h>
 
 #define CODEGEN_SET_FALLBACK(op, flags) data.context.fallback[op] = {execute_##op, flags}
-#define CODEGEN_SET_NAME(op) data.names[op] = #op
-
-// Similar to a dispatch table in lvmexecute.cpp
-#define CODEGEN_SET_NAMES() \
-    CODEGEN_SET_NAME(LOP_NOP), CODEGEN_SET_NAME(LOP_BREAK), CODEGEN_SET_NAME(LOP_LOADNIL), CODEGEN_SET_NAME(LOP_LOADB), CODEGEN_SET_NAME(LOP_LOADN), \
-        CODEGEN_SET_NAME(LOP_LOADK), CODEGEN_SET_NAME(LOP_MOVE), CODEGEN_SET_NAME(LOP_GETGLOBAL), CODEGEN_SET_NAME(LOP_SETGLOBAL), \
-        CODEGEN_SET_NAME(LOP_GETUPVAL), CODEGEN_SET_NAME(LOP_SETUPVAL), CODEGEN_SET_NAME(LOP_CLOSEUPVALS), CODEGEN_SET_NAME(LOP_GETIMPORT), \
-        CODEGEN_SET_NAME(LOP_GETTABLE), CODEGEN_SET_NAME(LOP_SETTABLE), CODEGEN_SET_NAME(LOP_GETTABLEKS), CODEGEN_SET_NAME(LOP_SETTABLEKS), \
-        CODEGEN_SET_NAME(LOP_GETTABLEN), CODEGEN_SET_NAME(LOP_SETTABLEN), CODEGEN_SET_NAME(LOP_NEWCLOSURE), CODEGEN_SET_NAME(LOP_NAMECALL), \
-        CODEGEN_SET_NAME(LOP_CALL), CODEGEN_SET_NAME(LOP_RETURN), CODEGEN_SET_NAME(LOP_JUMP), CODEGEN_SET_NAME(LOP_JUMPBACK), \
-        CODEGEN_SET_NAME(LOP_JUMPIF), CODEGEN_SET_NAME(LOP_JUMPIFNOT), CODEGEN_SET_NAME(LOP_JUMPIFEQ), CODEGEN_SET_NAME(LOP_JUMPIFLE), \
-        CODEGEN_SET_NAME(LOP_JUMPIFLT), CODEGEN_SET_NAME(LOP_JUMPIFNOTEQ), CODEGEN_SET_NAME(LOP_JUMPIFNOTLE), CODEGEN_SET_NAME(LOP_JUMPIFNOTLT), \
-        CODEGEN_SET_NAME(LOP_ADD), CODEGEN_SET_NAME(LOP_SUB), CODEGEN_SET_NAME(LOP_MUL), CODEGEN_SET_NAME(LOP_DIV), CODEGEN_SET_NAME(LOP_MOD), \
-        CODEGEN_SET_NAME(LOP_POW), CODEGEN_SET_NAME(LOP_ADDK), CODEGEN_SET_NAME(LOP_SUBK), CODEGEN_SET_NAME(LOP_MULK), CODEGEN_SET_NAME(LOP_DIVK), \
-        CODEGEN_SET_NAME(LOP_MODK), CODEGEN_SET_NAME(LOP_POWK), CODEGEN_SET_NAME(LOP_AND), CODEGEN_SET_NAME(LOP_OR), CODEGEN_SET_NAME(LOP_ANDK), \
-        CODEGEN_SET_NAME(LOP_ORK), CODEGEN_SET_NAME(LOP_CONCAT), CODEGEN_SET_NAME(LOP_NOT), CODEGEN_SET_NAME(LOP_MINUS), \
-        CODEGEN_SET_NAME(LOP_LENGTH), CODEGEN_SET_NAME(LOP_NEWTABLE), CODEGEN_SET_NAME(LOP_DUPTABLE), CODEGEN_SET_NAME(LOP_SETLIST), \
-        CODEGEN_SET_NAME(LOP_FORNPREP), CODEGEN_SET_NAME(LOP_FORNLOOP), CODEGEN_SET_NAME(LOP_FORGLOOP), CODEGEN_SET_NAME(LOP_FORGPREP_INEXT), \
-        CODEGEN_SET_NAME(LOP_DEP_FORGLOOP_INEXT), CODEGEN_SET_NAME(LOP_FORGPREP_NEXT), CODEGEN_SET_NAME(LOP_DEP_FORGLOOP_NEXT), \
-        CODEGEN_SET_NAME(LOP_GETVARARGS), CODEGEN_SET_NAME(LOP_DUPCLOSURE), CODEGEN_SET_NAME(LOP_PREPVARARGS), CODEGEN_SET_NAME(LOP_LOADKX), \
-        CODEGEN_SET_NAME(LOP_JUMPX), CODEGEN_SET_NAME(LOP_FASTCALL), CODEGEN_SET_NAME(LOP_COVERAGE), CODEGEN_SET_NAME(LOP_CAPTURE), \
-        CODEGEN_SET_NAME(LOP_DEP_JUMPIFEQK), CODEGEN_SET_NAME(LOP_DEP_JUMPIFNOTEQK), CODEGEN_SET_NAME(LOP_FASTCALL1), \
-        CODEGEN_SET_NAME(LOP_FASTCALL2), CODEGEN_SET_NAME(LOP_FASTCALL2K), CODEGEN_SET_NAME(LOP_FORGPREP), CODEGEN_SET_NAME(LOP_JUMPXEQKNIL), \
-        CODEGEN_SET_NAME(LOP_JUMPXEQKB), CODEGEN_SET_NAME(LOP_JUMPXEQKN), CODEGEN_SET_NAME(LOP_JUMPXEQKS)
 
 static int luauF_missing(lua_State* L, StkId res, TValue* arg0, int nresults, StkId args, int nparams)
 {
@@ -61,21 +38,11 @@ NativeState::~NativeState() = default;
 
 void initFallbackTable(NativeState& data)
 {
-    CODEGEN_SET_FALLBACK(LOP_GETGLOBAL, 0);
+    // TODO: lvmexecute_split.py could be taught to generate a subset of instructions we actually need
-    CODEGEN_SET_FALLBACK(LOP_SETGLOBAL, 0);
+    CODEGEN_SET_FALLBACK(LOP_NEWCLOSURE, 0);
-    CODEGEN_SET_FALLBACK(LOP_SETUPVAL, 0);
-    CODEGEN_SET_FALLBACK(LOP_CLOSEUPVALS, 0);
-    CODEGEN_SET_FALLBACK(LOP_GETIMPORT, 0);
-    CODEGEN_SET_FALLBACK(LOP_GETTABLEKS, 0);
-    CODEGEN_SET_FALLBACK(LOP_SETTABLEKS, 0);
-    CODEGEN_SET_FALLBACK(LOP_NEWCLOSURE, kFallbackUpdatePc);
     CODEGEN_SET_FALLBACK(LOP_NAMECALL, 0);
     CODEGEN_SET_FALLBACK(LOP_CALL, kFallbackUpdateCi | kFallbackCheckInterrupt);
     CODEGEN_SET_FALLBACK(LOP_RETURN, kFallbackUpdateCi | kFallbackCheckInterrupt);
-    CODEGEN_SET_FALLBACK(LOP_CONCAT, 0);
-    CODEGEN_SET_FALLBACK(LOP_NEWTABLE, 0);
-    CODEGEN_SET_FALLBACK(LOP_DUPTABLE, 0);
-    CODEGEN_SET_FALLBACK(LOP_SETLIST, kFallbackCheckInterrupt);
     CODEGEN_SET_FALLBACK(LOP_FORGPREP, kFallbackUpdatePc);
     CODEGEN_SET_FALLBACK(LOP_FORGLOOP, kFallbackUpdatePc | kFallbackCheckInterrupt);
     CODEGEN_SET_FALLBACK(LOP_FORGPREP_INEXT, kFallbackUpdatePc);
@@ -83,9 +50,14 @@ void initFallbackTable(NativeState& data)
     CODEGEN_SET_FALLBACK(LOP_GETVARARGS, 0);
     CODEGEN_SET_FALLBACK(LOP_DUPCLOSURE, 0);
     CODEGEN_SET_FALLBACK(LOP_PREPVARARGS, 0);
-    CODEGEN_SET_FALLBACK(LOP_LOADKX, 0);
     CODEGEN_SET_FALLBACK(LOP_COVERAGE, 0);
     CODEGEN_SET_FALLBACK(LOP_BREAK, 0);
+
+    // Fallbacks that are called from partial implementation of an instruction
+    CODEGEN_SET_FALLBACK(LOP_GETGLOBAL, 0);
+    CODEGEN_SET_FALLBACK(LOP_SETGLOBAL, 0);
+    CODEGEN_SET_FALLBACK(LOP_GETTABLEKS, 0);
+    CODEGEN_SET_FALLBACK(LOP_SETTABLEKS, 0);
 }
 
 void initHelperFunctions(NativeState& data)
@@ -105,18 +77,23 @@ void initHelperFunctions(NativeState& data)
     data.context.luaV_prepareFORN = luaV_prepareFORN;
     data.context.luaV_gettable = luaV_gettable;
     data.context.luaV_settable = luaV_settable;
+    data.context.luaV_getimport = luaV_getimport;
+    data.context.luaV_concat = luaV_concat;
 
     data.context.luaH_getn = luaH_getn;
+    data.context.luaH_new = luaH_new;
+    data.context.luaH_clone = luaH_clone;
+    data.context.luaH_resizearray = luaH_resizearray;
 
     data.context.luaC_barriertable = luaC_barriertable;
+    data.context.luaC_barrierf = luaC_barrierf;
+    data.context.luaC_barrierback = luaC_barrierback;
+    data.context.luaC_step = luaC_step;
+
+    data.context.luaF_close = luaF_close;
 
     data.context.libm_pow = pow;
 }
 
-void initInstructionNames(NativeState& data)
-{
-    CODEGEN_SET_NAMES();
-}
-
 } // namespace CodeGen
 } // namespace Luau

CodeGen/src/NativeState.h

@@ -61,10 +61,20 @@ struct NativeContext
     void (*luaV_prepareFORN)(lua_State* L, StkId plimit, StkId pstep, StkId pinit) = nullptr;
     void (*luaV_gettable)(lua_State* L, const TValue* t, TValue* key, StkId val) = nullptr;
     void (*luaV_settable)(lua_State* L, const TValue* t, TValue* key, StkId val) = nullptr;
+    void (*luaV_getimport)(lua_State* L, Table* env, TValue* k, uint32_t id, bool propagatenil) = nullptr;
+    void (*luaV_concat)(lua_State* L, int total, int last) = nullptr;
 
     int (*luaH_getn)(Table* t) = nullptr;
+    Table* (*luaH_new)(lua_State* L, int narray, int lnhash) = nullptr;
+    Table* (*luaH_clone)(lua_State* L, Table* tt) = nullptr;
+    void (*luaH_resizearray)(lua_State* L, Table* t, int nasize) = nullptr;
 
     void (*luaC_barriertable)(lua_State* L, Table* t, GCObject* v) = nullptr;
+    void (*luaC_barrierf)(lua_State* L, GCObject* o, GCObject* v) = nullptr;
+    void (*luaC_barrierback)(lua_State* L, GCObject* o, GCObject** gclist) = nullptr;
+    size_t (*luaC_step)(lua_State* L, bool assist) = nullptr;
+
+    void (*luaF_close)(lua_State* L, StkId level) = nullptr;
 
     double (*libm_pow)(double, double) = nullptr;
 };
@@ -77,9 +87,6 @@ struct NativeState
     CodeAllocator codeAllocator;
     std::unique_ptr<UnwindBuilder> unwindBuilder;
 
-    // For annotations in assembly text generation
-    const char* names[LOP__COUNT] = {};
-
     uint8_t* gateData = nullptr;
     size_t gateDataSize = 0;
 
@@ -88,7 +95,6 @@ struct NativeState
 
 void initFallbackTable(NativeState& data);
 void initHelperFunctions(NativeState& data);
-void initInstructionNames(NativeState& data);
 
 } // namespace CodeGen
 } // namespace Luau

Common/include/Luau/Common.h

@@ -20,6 +20,10 @@
 #define LUAU_DEBUGBREAK() __builtin_trap()
 #endif
 
+#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define LUAU_BIG_ENDIAN
+#endif
+
 namespace Luau
 {
 

Compiler/include/Luau/BytecodeBuilder.h

@@ -117,6 +117,8 @@ public:
     std::string dumpEverything() const;
     std::string dumpSourceRemarks() const;
 
+    void annotateInstruction(std::string& result, uint32_t fid, uint32_t instid) const;
+
     static uint32_t getImportId(int32_t id0);
     static uint32_t getImportId(int32_t id0, int32_t id1);
     static uint32_t getImportId(int32_t id0, int32_t id1, int32_t id2);
@@ -179,6 +181,7 @@ private:
 
         std::string dump;
         std::string dumpname;
+        std::vector<int> dumpinstoffs;
     };
 
     struct DebugLocal
@@ -251,11 +254,13 @@ private:
     std::vector<std::string> dumpSource;
     std::vector<std::pair<int, std::string>> dumpRemarks;
 
-    std::string (BytecodeBuilder::*dumpFunctionPtr)() const = nullptr;
+    std::string (BytecodeBuilder::*dumpFunctionPtr)(std::vector<int>&) const = nullptr;
 
     void validate() const;
+    void validateInstructions() const;
+    void validateVariadic() const;
 
-    std::string dumpCurrentFunction() const;
+    std::string dumpCurrentFunction(std::vector<int>& dumpinstoffs) const;
     void dumpInstruction(const uint32_t* opcode, std::string& output, int targetLabel) const;
 
     void writeFunction(std::string& ss, uint32_t id) const;

Compiler/src/Builtins.cpp

@@ -4,8 +4,6 @@
 #include "Luau/Bytecode.h"
 #include "Luau/Compiler.h"
 
-LUAU_FASTFLAGVARIABLE(LuauCompileBuiltinMT, false)
-
 namespace Luau
 {
 namespace Compile
@@ -66,13 +64,10 @@ static int getBuiltinFunctionId(const Builtin& builtin, const CompileOptions& op
     if (builtin.isGlobal("select"))
         return LBF_SELECT_VARARG;
 
-    if (FFlag::LuauCompileBuiltinMT)
+    if (builtin.isGlobal("getmetatable"))
-    {
+        return LBF_GETMETATABLE;
-        if (builtin.isGlobal("getmetatable"))
+    if (builtin.isGlobal("setmetatable"))
-            return LBF_GETMETATABLE;
+        return LBF_SETMETATABLE;
-        if (builtin.isGlobal("setmetatable"))
-            return LBF_SETMETATABLE;
-    }
 
     if (builtin.object == "math")
     {

Compiler/src/BytecodeBuilder.cpp

@@ -269,7 +269,7 @@ void BytecodeBuilder::endFunction(uint8_t maxstacksize, uint8_t numupvalues)
 
     // this call is indirect to make sure we only gain link time dependency on dumpCurrentFunction when needed
     if (dumpFunctionPtr)
-        func.dump = (this->*dumpFunctionPtr)();
+        func.dump = (this->*dumpFunctionPtr)(func.dumpinstoffs);
 
     insns.clear();
     lines.clear();
@@ -1078,6 +1078,12 @@ uint8_t BytecodeBuilder::getVersion()
 
 #ifdef LUAU_ASSERTENABLED
 void BytecodeBuilder::validate() const
+{
+    validateInstructions();
+    validateVariadic();
+}
+
+void BytecodeBuilder::validateInstructions() const
 {
 #define VREG(v) LUAU_ASSERT(unsigned(v) < func.maxstacksize)
 #define VREGRANGE(v, count) LUAU_ASSERT(unsigned(v + (count < 0 ? 0 : count)) <= func.maxstacksize)
@@ -1090,26 +1096,27 @@ void BytecodeBuilder::validate() const
 
     const Function& func = functions[currentFunction];
 
-    // first pass: tag instruction offsets so that we can validate jumps
+    // tag instruction offsets so that we can validate jumps
-    std::vector<uint8_t> insnvalid(insns.size(), false);
+    std::vector<uint8_t> insnvalid(insns.size(), 0);
 
     for (size_t i = 0; i < insns.size();)
     {
-        uint8_t op = LUAU_INSN_OP(insns[i]);
+        uint32_t insn = insns[i];
+        LuauOpcode op = LuauOpcode(LUAU_INSN_OP(insn));
 
         insnvalid[i] = true;
 
-        i += getOpLength(LuauOpcode(op));
+        i += getOpLength(op);
         LUAU_ASSERT(i <= insns.size());
     }
 
     std::vector<uint8_t> openCaptures;
 
-    // second pass: validate the rest of the bytecode
+    // validate individual instructions
     for (size_t i = 0; i < insns.size();)
     {
         uint32_t insn = insns[i];
-        uint8_t op = LUAU_INSN_OP(insn);
+        LuauOpcode op = LuauOpcode(LUAU_INSN_OP(insn));
 
         switch (op)
         {
@@ -1452,7 +1459,7 @@ void BytecodeBuilder::validate() const
             LUAU_ASSERT(!"Unsupported opcode");
         }
 
-        i += getOpLength(LuauOpcode(op));
+        i += getOpLength(op);
         LUAU_ASSERT(i <= insns.size());
     }
 
@@ -1469,6 +1476,126 @@ void BytecodeBuilder::validate() const
 #undef VCONSTANY
 #undef VJUMP
 }
+
+void BytecodeBuilder::validateVariadic() const
+{
+    // validate MULTRET sequences: instructions that produce a variadic sequence and consume one must come in pairs
+    // we classify instructions into four groups: producers, consumers, neutral and others
+    // any producer (an instruction that produces more than one value) must be followed by 0 or more neutral instructions
+    // and a consumer (that consumes more than one value); these form a variadic sequence.
+    // except for producer, no instruction in the variadic sequence may be a jump target.
+    // from the execution perspective, producer adjusts L->top to point to one past the last result, neutral instructions
+    // leave L->top unmodified, and consumer adjusts L->top back to the stack frame end.
+    // consumers invalidate all values after L->top after they execute (which we currently don't validate)
+    bool variadicSeq = false;
+
+    std::vector<uint8_t> insntargets(insns.size(), 0);
+
+    for (size_t i = 0; i < insns.size();)
+    {
+        uint32_t insn = insns[i];
+        LuauOpcode op = LuauOpcode(LUAU_INSN_OP(insn));
+
+        int target = getJumpTarget(insn, uint32_t(i));
+
+        if (target >= 0 && !isFastCall(op))
+        {
+            LUAU_ASSERT(unsigned(target) < insns.size());
+
+            insntargets[target] = true;
+        }
+
+        i += getOpLength(op);
+        LUAU_ASSERT(i <= insns.size());
+    }
+
+    for (size_t i = 0; i < insns.size();)
+    {
+        uint32_t insn = insns[i];
+        LuauOpcode op = LuauOpcode(LUAU_INSN_OP(insn));
+
+        if (variadicSeq)
+        {
+            // no instruction inside the sequence, including the consumer, may be a jump target
+            // this guarantees uninterrupted L->top adjustment flow
+            LUAU_ASSERT(!insntargets[i]);
+        }
+
+        if (op == LOP_CALL)
+        {
+            // note: calls may end one variadic sequence and start a new one
+
+            if (LUAU_INSN_B(insn) == 0)
+            {
+                // consumer instruction ens a variadic sequence
+                LUAU_ASSERT(variadicSeq);
+                variadicSeq = false;
+            }
+            else
+            {
+                // CALL is not a neutral instruction so it can't be present in a variadic sequence unless it's a consumer
+                LUAU_ASSERT(!variadicSeq);
+            }
+
+            if (LUAU_INSN_C(insn) == 0)
+            {
+                // producer instruction starts a variadic sequence
+                LUAU_ASSERT(!variadicSeq);
+                variadicSeq = true;
+            }
+        }
+        else if (op == LOP_GETVARARGS && LUAU_INSN_B(insn) == 0)
+        {
+            // producer instruction starts a variadic sequence
+            LUAU_ASSERT(!variadicSeq);
+            variadicSeq = true;
+        }
+        else if ((op == LOP_RETURN && LUAU_INSN_B(insn) == 0) || (op == LOP_SETLIST && LUAU_INSN_C(insn) == 0))
+        {
+            // consumer instruction ends a variadic sequence
+            LUAU_ASSERT(variadicSeq);
+            variadicSeq = false;
+        }
+        else if (op == LOP_FASTCALL)
+        {
+            int callTarget = int(i + LUAU_INSN_C(insn) + 1);
+            LUAU_ASSERT(unsigned(callTarget) < insns.size() && LUAU_INSN_OP(insns[callTarget]) == LOP_CALL);
+
+            if (LUAU_INSN_B(insns[callTarget]) == 0)
+            {
+                // consumer instruction ends a variadic sequence; however, we can't terminate it yet because future analysis of CALL will do it
+                // during FASTCALL fallback, the instructions between this and CALL consumer are going to be executed before L->top so they must
+                // be neutral; as such, we will defer termination of variadic sequence until CALL analysis
+                LUAU_ASSERT(variadicSeq);
+            }
+            else
+            {
+                // FASTCALL is not a neutral instruction so it can't be present in a variadic sequence unless it's linked to CALL consumer
+                LUAU_ASSERT(!variadicSeq);
+            }
+
+            // note: if FASTCALL is linked to a CALL producer, the instructions between FASTCALL and CALL are technically not part of an executed
+            // variadic sequence since they are never executed if FASTCALL does anything, so it's okay to skip their validation until CALL
+            // (we can't simply start a variadic sequence here because that would trigger assertions during linked CALL validation)
+        }
+        else if (op == LOP_CLOSEUPVALS || op == LOP_NAMECALL || op == LOP_GETIMPORT || op == LOP_MOVE || op == LOP_GETUPVAL || op == LOP_GETGLOBAL ||
+                 op == LOP_GETTABLEKS || op == LOP_COVERAGE)
+        {
+            // instructions inside a variadic sequence must be neutral (can't change L->top)
+            // while there are many neutral instructions like this, here we check that the instruction is one of the few
+            // that we'd expect to exist in FASTCALL fallback sequences or between consecutive CALLs for encoding reasons
+        }
+        else
+        {
+            LUAU_ASSERT(!variadicSeq);
+        }
+
+        i += getOpLength(op);
+        LUAU_ASSERT(i <= insns.size());
+    }
+
+    LUAU_ASSERT(!variadicSeq);
+}
 #endif
 
 void BytecodeBuilder::dumpInstruction(const uint32_t* code, std::string& result, int targetLabel) const
@@ -1800,7 +1927,7 @@ void BytecodeBuilder::dumpInstruction(const uint32_t* code, std::string& result,
     }
 }
 
-std::string BytecodeBuilder::dumpCurrentFunction() const
+std::string BytecodeBuilder::dumpCurrentFunction(std::vector<int>& dumpinstoffs) const
 {
     if ((dumpFlags & Dump_Code) == 0)
         return std::string();
@@ -1850,11 +1977,15 @@ std::string BytecodeBuilder::dumpCurrentFunction() const
         if (labels[i] == 0)
             labels[i] = nextLabel++;
 
+    dumpinstoffs.reserve(insns.size());
+
     for (size_t i = 0; i < insns.size();)
     {
         const uint32_t* code = &insns[i];
         uint8_t op = LUAU_INSN_OP(*code);
 
+        dumpinstoffs.push_back(int(result.size()));
+
         if (op == LOP_PREPVARARGS)
         {
             // Don't emit function header in bytecode - it's used for call dispatching and doesn't contain "interesting" information
@@ -1897,6 +2028,8 @@ std::string BytecodeBuilder::dumpCurrentFunction() const
         LUAU_ASSERT(i <= insns.size());
     }
 
+    dumpinstoffs.push_back(int(result.size()));
+
     return result;
 }
 
@@ -1986,4 +2119,20 @@ std::string BytecodeBuilder::dumpSourceRemarks() const
     return result;
 }
 
+void BytecodeBuilder::annotateInstruction(std::string& result, uint32_t fid, uint32_t instid) const
+{
+    if ((dumpFlags & Dump_Code) == 0)
+        return;
+
+    LUAU_ASSERT(fid < functions.size());
+
+    const Function& function = functions[fid];
+    const std::string& dump = function.dump;
+    const std::vector<int>& dumpinstoffs = function.dumpinstoffs;
+
+    LUAU_ASSERT(instid + 1 < dumpinstoffs.size());
+
+    formatAppend(result, "%.*s", dumpinstoffs[instid + 1] - dumpinstoffs[instid], dump.data() + dumpinstoffs[instid]);
+}
+
 } // namespace Luau

Sources.cmake

@@ -104,7 +104,9 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/include/Luau/Constraint.h
     Analysis/include/Luau/ConstraintGraphBuilder.h
     Analysis/include/Luau/ConstraintSolver.h
+    Analysis/include/Luau/DataFlowGraphBuilder.h
     Analysis/include/Luau/DcrLogger.h
+    Analysis/include/Luau/Def.h
     Analysis/include/Luau/Documentation.h
     Analysis/include/Luau/Error.h
     Analysis/include/Luau/FileResolver.h
@@ -114,6 +116,7 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/include/Luau/JsonEmitter.h
     Analysis/include/Luau/Linter.h
     Analysis/include/Luau/LValue.h
+    Analysis/include/Luau/Metamethods.h
     Analysis/include/Luau/Module.h
     Analysis/include/Luau/ModuleResolver.h
     Analysis/include/Luau/Normalize.h
@@ -154,7 +157,9 @@ target_sources(Luau.Analysis PRIVATE
     Analysis/src/Constraint.cpp
     Analysis/src/ConstraintGraphBuilder.cpp
     Analysis/src/ConstraintSolver.cpp
+    Analysis/src/DataFlowGraphBuilder.cpp
     Analysis/src/DcrLogger.cpp
+    Analysis/src/Def.cpp
     Analysis/src/EmbeddedBuiltinDefinitions.cpp
     Analysis/src/Error.cpp
     Analysis/src/Frontend.cpp
@@ -301,9 +306,9 @@ if(TARGET Luau.UnitTest)
         tests/CodeAllocator.test.cpp
         tests/Compiler.test.cpp
         tests/Config.test.cpp
-        tests/ConstraintGraphBuilder.test.cpp
         tests/ConstraintSolver.test.cpp
         tests/CostModel.test.cpp
+        tests/DataFlowGraphBuilder.test.cpp
         tests/Error.test.cpp
         tests/Frontend.test.cpp
         tests/JsonEmitter.test.cpp
@@ -372,7 +377,7 @@ if(TARGET Luau.CLI.Test)
         CLI/Profiler.h
         CLI/Profiler.cpp
         CLI/Repl.cpp
-    
+
         tests/Repl.test.cpp
         tests/main.cpp)
 endif()

VM/src/ldebug.cpp

@@ -12,8 +12,6 @@
 #include <string.h>
 #include <stdio.h>
 
-LUAU_FASTFLAGVARIABLE(LuauFasterGetInfo, false)
-
 static const char* getfuncname(Closure* f);
 
 static int currentpc(lua_State* L, CallInfo* ci)
@@ -105,8 +103,7 @@ static Closure* auxgetinfo(lua_State* L, const char* what, lua_Debug* ar, Closur
                 ar->source = "=[C]";
                 ar->what = "C";
                 ar->linedefined = -1;
-                if (FFlag::LuauFasterGetInfo)
+                ar->short_src = "[C]";
-                    ar->short_src = "[C]";
             }
             else
             {
@@ -114,13 +111,7 @@ static Closure* auxgetinfo(lua_State* L, const char* what, lua_Debug* ar, Closur
                 ar->source = getstr(source);
                 ar->what = "Lua";
                 ar->linedefined = f->l.p->linedefined;
-                if (FFlag::LuauFasterGetInfo)
+                ar->short_src = luaO_chunkid(ar->ssbuf, sizeof(ar->ssbuf), getstr(source), source->len);
-                    ar->short_src = luaO_chunkid(ar->ssbuf, sizeof(ar->ssbuf), getstr(source), source->len);
-            }
-            if (!FFlag::LuauFasterGetInfo)
-            {
-                luaO_chunkid(ar->ssbuf, LUA_IDSIZE, ar->source, 0);
-                ar->short_src = ar->ssbuf;
             }
             break;
         }
@@ -195,25 +186,12 @@ int lua_getinfo(lua_State* L, int level, const char* what, lua_Debug* ar)
     }
     if (f)
     {
-        if (FFlag::LuauFasterGetInfo)
+        // auxgetinfo fills ar and optionally requests to put closure on stack
+        if (Closure* fcl = auxgetinfo(L, what, ar, f, ci))
         {
-            // auxgetinfo fills ar and optionally requests to put closure on stack
+            luaC_threadbarrier(L);
-            if (Closure* fcl = auxgetinfo(L, what, ar, f, ci))
+            setclvalue(L, L->top, fcl);
-            {
+            incr_top(L);
-                luaC_threadbarrier(L);
-                setclvalue(L, L->top, fcl);
-                incr_top(L);
-            }
-        }
-        else
-        {
-            auxgetinfo(L, what, ar, f, ci);
-            if (strchr(what, 'f'))
-            {
-                luaC_threadbarrier(L);
-                setclvalue(L, L->top, f);
-                incr_top(L);
-            }
         }
     }
     return f ? 1 : 0;

VM/src/lobject.cpp

@@ -13,8 +13,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-LUAU_FASTFLAG(LuauFasterGetInfo)
-
 const TValue luaO_nilobject_ = {{NULL}, {0}, LUA_TNIL};
 
 int luaO_log2(unsigned int x)
@@ -121,48 +119,20 @@ const char* luaO_chunkid(char* buf, size_t buflen, const char* source, size_t sr
 {
     if (*source == '=')
     {
-        if (FFlag::LuauFasterGetInfo)
+        if (srclen <= buflen)
-        {
+            return source + 1;
-            if (srclen <= buflen)
+        // truncate the part after =
-                return source + 1;
+        memcpy(buf, source + 1, buflen - 1);
-            // truncate the part after =
+        buf[buflen - 1] = '\0';
-            memcpy(buf, source + 1, buflen - 1);
-            buf[buflen - 1] = '\0';
-        }
-        else
-        {
-            source++; // skip the `='
-            size_t len = strlen(source);
-            size_t dstlen = len < buflen ? len : buflen - 1;
-            memcpy(buf, source, dstlen);
-            buf[dstlen] = '\0';
-        }
     }
     else if (*source == '@')
     {
-        if (FFlag::LuauFasterGetInfo)
+        if (srclen <= buflen)
-        {
+            return source + 1;
-            if (srclen <= buflen)
+        // truncate the part after @
-                return source + 1;
+        memcpy(buf, "...", 3);
-            // truncate the part after @
+        memcpy(buf + 3, source + srclen - (buflen - 4), buflen - 4);
-            memcpy(buf, "...", 3);
+        buf[buflen - 1] = '\0';
-            memcpy(buf + 3, source + srclen - (buflen - 4), buflen - 4);
-            buf[buflen - 1] = '\0';
-        }
-        else
-        {
-            size_t l;
-            source++; // skip the `@'
-            buflen -= sizeof("...");
-            l = strlen(source);
-            strcpy(buf, "");
-            if (l > buflen)
-            {
-                source += (l - buflen); // get last part of file name
-                strcat(buf, "...");
-            }
-            strcat(buf, source);
-        }
     }
     else
     {                                         // buf = [string "string"]

VM/src/lvmexecute.cpp

@@ -758,6 +758,8 @@ reentry:
                 Proto* pv = cl->l.p->p[LUAU_INSN_D(insn)];
                 LUAU_ASSERT(unsigned(LUAU_INSN_D(insn)) < unsigned(cl->l.p->sizep));
 
+                VM_PROTECT_PC(); // luaF_newLclosure may fail due to OOM
+
                 // note: we save closure to stack early in case the code below wants to capture it by value
                 Closure* ncl = luaF_newLclosure(L, pv->nups, cl->env, pv);
                 setclvalue(L, ra, ncl);
@@ -2056,6 +2058,8 @@ reentry:
                 int b = LUAU_INSN_B(insn);
                 uint32_t aux = *pc++;
 
+                VM_PROTECT_PC(); // luaH_new may fail due to OOM
+
                 sethvalue(L, ra, luaH_new(L, aux, b == 0 ? 0 : (1 << (b - 1))));
                 VM_PROTECT(luaC_checkGC(L));
                 VM_NEXT();
@@ -2067,6 +2071,8 @@ reentry:
                 StkId ra = VM_REG(LUAU_INSN_A(insn));
                 TValue* kv = VM_KV(LUAU_INSN_D(insn));
 
+                VM_PROTECT_PC(); // luaH_clone may fail due to OOM
+
                 sethvalue(L, ra, luaH_clone(L, hvalue(kv)));
                 VM_PROTECT(luaC_checkGC(L));
                 VM_NEXT();
@@ -2185,7 +2191,8 @@ reentry:
                         // protect against __iter returning nil, since nil is used as a marker for builtin iteration in FORGLOOP
                         if (ttisnil(ra))
                         {
-                            VM_PROTECT(luaG_typeerror(L, ra, "call"));
+                            VM_PROTECT_PC(); // next call always errors
+                            luaG_typeerror(L, ra, "call");
                         }
                     }
                     else if (fasttm(L, mt, TM_CALL))
@@ -2202,7 +2209,8 @@ reentry:
                     }
                     else
                     {
-                        VM_PROTECT(luaG_typeerror(L, ra, "iterate over"));
+                        VM_PROTECT_PC(); // next call always errors
+                        luaG_typeerror(L, ra, "iterate over");
                     }
                 }
 
@@ -2325,7 +2333,8 @@ reentry:
                 }
                 else if (!ttisfunction(ra))
                 {
-                    VM_PROTECT(luaG_typeerror(L, ra, "iterate over"));
+                    VM_PROTECT_PC(); // next call always errors
+                    luaG_typeerror(L, ra, "iterate over");
                 }
 
                 pc += LUAU_INSN_D(insn);
@@ -2353,7 +2362,8 @@ reentry:
                 }
                 else if (!ttisfunction(ra))
                 {
-                    VM_PROTECT(luaG_typeerror(L, ra, "iterate over"));
+                    VM_PROTECT_PC(); // next call always errors
+                    luaG_typeerror(L, ra, "iterate over");
                 }
 
                 pc += LUAU_INSN_D(insn);
@@ -2404,6 +2414,8 @@ reentry:
 
                 Closure* kcl = clvalue(kv);
 
+                VM_PROTECT_PC(); // luaF_newLclosure may fail due to OOM
+
                 // clone closure if the environment is not shared
                 // note: we save closure to stack early in case the code below wants to capture it by value
                 Closure* ncl = (kcl->env == cl->env) ? kcl : luaF_newLclosure(L, kcl->nupvalues, cl->env, kcl->l.p);
@@ -2533,7 +2545,7 @@ reentry:
 
                 if (cl->env->safeenv && f)
                 {
-                    VM_PROTECT_PC();
+                    VM_PROTECT_PC(); // f may fail due to OOM
 
                     int n = f(L, ra, ra + 1, nresults, ra + 2, nparams);
 
@@ -2611,7 +2623,7 @@ reentry:
 
                 if (cl->env->safeenv && f)
                 {
-                    VM_PROTECT_PC();
+                    VM_PROTECT_PC(); // f may fail due to OOM
 
                     int n = f(L, ra, arg, nresults, NULL, nparams);
 
@@ -2667,7 +2679,7 @@ reentry:
 
                 if (cl->env->safeenv && f)
                 {
-                    VM_PROTECT_PC();
+                    VM_PROTECT_PC(); // f may fail due to OOM
 
                     int n = f(L, ra, arg1, nresults, arg2, nparams);
 
@@ -2723,7 +2735,7 @@ reentry:
 
                 if (cl->env->safeenv && f)
                 {
-                    VM_PROTECT_PC();
+                    VM_PROTECT_PC(); // f may fail due to OOM
 
                     int n = f(L, ra, arg1, nresults, arg2, nparams);
 

bench/gc/test_GC_Boehm_Trees.lua

@@ -1,4 +1,4 @@
---!non-strict
+--!nonstrict
 local bench = script and require(script.Parent.bench_support) or require("bench_support")
 
 local stretchTreeDepth = 18 -- about 16Mb

tests/AssemblyBuilderX64.test.cpp

@@ -264,6 +264,88 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "FormsOfImul")
     SINGLE_COMPARE(imul(r12, rax, -13), 0x4c, 0x6b, 0xe0, 0xf3);
 }
 
+TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "NopForms")
+{
+    SINGLE_COMPARE(nop(), 0x90);
+    SINGLE_COMPARE(nop(2), 0x66, 0x90);
+    SINGLE_COMPARE(nop(3), 0x0f, 0x1f, 0x00);
+    SINGLE_COMPARE(nop(4), 0x0f, 0x1f, 0x40, 0x00);
+    SINGLE_COMPARE(nop(5), 0x0f, 0x1f, 0x44, 0x00, 0x00);
+    SINGLE_COMPARE(nop(6), 0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00);
+    SINGLE_COMPARE(nop(7), 0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00);
+    SINGLE_COMPARE(nop(8), 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00);
+    SINGLE_COMPARE(nop(9), 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00);
+    SINGLE_COMPARE(nop(15), 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00, 0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00); // 9+6
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AlignmentForms")
+{
+    check(
+        [](AssemblyBuilderX64& build) {
+            build.ret();
+            build.align(8, AlignmentDataX64::Nop);
+        },
+        {0xc3, 0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00});
+
+    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});
+
+    check(
+        [](AssemblyBuilderX64& build) {
+            build.ret();
+            build.align(8, AlignmentDataX64::Int3);
+        },
+        {0xc3, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc});
+
+    check(
+        [](AssemblyBuilderX64& build) {
+            build.ret();
+            build.align(8, AlignmentDataX64::Ud2);
+        },
+        {0xc3, 0x0f, 0x0b, 0x0f, 0x0b, 0x0f, 0x0b, 0xcc});
+}
+
+TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AlignmentOverflow")
+{
+    // Test that alignment correctly resizes the code buffer
+    {
+        AssemblyBuilderX64 build(/* logText */ false);
+
+        build.ret();
+        build.align(8192, AlignmentDataX64::Nop);
+        build.finalize();
+    }
+
+    {
+        AssemblyBuilderX64 build(/* logText */ false);
+
+        build.ret();
+        build.align(8192, AlignmentDataX64::Int3);
+        build.finalize();
+    }
+
+    {
+        AssemblyBuilderX64 build(/* logText */ false);
+
+        for (int i = 0; i < 8192; i++)
+            build.int3();
+        build.finalize();
+    }
+
+    {
+        AssemblyBuilderX64 build(/* logText */ false);
+
+        build.ret();
+        build.align(8192, AlignmentDataX64::Ud2);
+        build.finalize();
+    }
+}
+
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "ControlFlow")
 {
     // Jump back
@@ -330,67 +412,67 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "LabelCall")
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXBinaryInstructionForms")
 {
-    SINGLE_COMPARE(vaddpd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xa9, 0x58, 0xc6);
+    SINGLE_COMPARE(vaddpd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x29, 0x58, 0xc6);
-    SINGLE_COMPARE(vaddpd(xmm8, xmm10, xmmword[r9]), 0xc4, 0x41, 0xa9, 0x58, 0x01);
+    SINGLE_COMPARE(vaddpd(xmm8, xmm10, xmmword[r9]), 0xc4, 0x41, 0x29, 0x58, 0x01);
-    SINGLE_COMPARE(vaddpd(ymm8, ymm10, ymm14), 0xc4, 0x41, 0xad, 0x58, 0xc6);
+    SINGLE_COMPARE(vaddpd(ymm8, ymm10, ymm14), 0xc4, 0x41, 0x2d, 0x58, 0xc6);
-    SINGLE_COMPARE(vaddpd(ymm8, ymm10, ymmword[r9]), 0xc4, 0x41, 0xad, 0x58, 0x01);
+    SINGLE_COMPARE(vaddpd(ymm8, ymm10, ymmword[r9]), 0xc4, 0x41, 0x2d, 0x58, 0x01);
-    SINGLE_COMPARE(vaddps(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xa8, 0x58, 0xc6);
+    SINGLE_COMPARE(vaddps(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x28, 0x58, 0xc6);
-    SINGLE_COMPARE(vaddps(xmm8, xmm10, xmmword[r9]), 0xc4, 0x41, 0xa8, 0x58, 0x01);
+    SINGLE_COMPARE(vaddps(xmm8, xmm10, xmmword[r9]), 0xc4, 0x41, 0x28, 0x58, 0x01);
-    SINGLE_COMPARE(vaddsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x58, 0xc6);
+    SINGLE_COMPARE(vaddsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x58, 0xc6);
-    SINGLE_COMPARE(vaddsd(xmm8, xmm10, qword[r9]), 0xc4, 0x41, 0xab, 0x58, 0x01);
+    SINGLE_COMPARE(vaddsd(xmm8, xmm10, qword[r9]), 0xc4, 0x41, 0x2b, 0x58, 0x01);
-    SINGLE_COMPARE(vaddss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xaa, 0x58, 0xc6);
+    SINGLE_COMPARE(vaddss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2a, 0x58, 0xc6);
-    SINGLE_COMPARE(vaddss(xmm8, xmm10, dword[r9]), 0xc4, 0x41, 0xaa, 0x58, 0x01);
+    SINGLE_COMPARE(vaddss(xmm8, xmm10, dword[r9]), 0xc4, 0x41, 0x2a, 0x58, 0x01);
 
-    SINGLE_COMPARE(vaddps(xmm1, xmm2, xmm3), 0xc4, 0xe1, 0xe8, 0x58, 0xcb);
+    SINGLE_COMPARE(vaddps(xmm1, xmm2, xmm3), 0xc4, 0xe1, 0x68, 0x58, 0xcb);
-    SINGLE_COMPARE(vaddps(xmm9, xmm12, xmmword[r9 + r14 * 2 + 0x1c]), 0xc4, 0x01, 0x98, 0x58, 0x4c, 0x71, 0x1c);
+    SINGLE_COMPARE(vaddps(xmm9, xmm12, xmmword[r9 + r14 * 2 + 0x1c]), 0xc4, 0x01, 0x18, 0x58, 0x4c, 0x71, 0x1c);
-    SINGLE_COMPARE(vaddps(ymm1, ymm2, ymm3), 0xc4, 0xe1, 0xec, 0x58, 0xcb);
+    SINGLE_COMPARE(vaddps(ymm1, ymm2, ymm3), 0xc4, 0xe1, 0x6c, 0x58, 0xcb);
-    SINGLE_COMPARE(vaddps(ymm9, ymm12, ymmword[r9 + r14 * 2 + 0x1c]), 0xc4, 0x01, 0x9c, 0x58, 0x4c, 0x71, 0x1c);
+    SINGLE_COMPARE(vaddps(ymm9, ymm12, ymmword[r9 + r14 * 2 + 0x1c]), 0xc4, 0x01, 0x1c, 0x58, 0x4c, 0x71, 0x1c);
 
     // Coverage for other instructions that follow the same pattern
-    SINGLE_COMPARE(vsubsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x5c, 0xc6);
+    SINGLE_COMPARE(vsubsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x5c, 0xc6);
-    SINGLE_COMPARE(vmulsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x59, 0xc6);
+    SINGLE_COMPARE(vmulsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x59, 0xc6);
-    SINGLE_COMPARE(vdivsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x5e, 0xc6);
+    SINGLE_COMPARE(vdivsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x5e, 0xc6);
 
-    SINGLE_COMPARE(vxorpd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xa9, 0x57, 0xc6);
+    SINGLE_COMPARE(vxorpd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x29, 0x57, 0xc6);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXUnaryMergeInstructionForms")
 {
-    SINGLE_COMPARE(vsqrtpd(xmm8, xmm10), 0xc4, 0x41, 0xf9, 0x51, 0xc2);
+    SINGLE_COMPARE(vsqrtpd(xmm8, xmm10), 0xc4, 0x41, 0x79, 0x51, 0xc2);
-    SINGLE_COMPARE(vsqrtpd(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf9, 0x51, 0x01);
+    SINGLE_COMPARE(vsqrtpd(xmm8, xmmword[r9]), 0xc4, 0x41, 0x79, 0x51, 0x01);
-    SINGLE_COMPARE(vsqrtpd(ymm8, ymm10), 0xc4, 0x41, 0xfd, 0x51, 0xc2);
+    SINGLE_COMPARE(vsqrtpd(ymm8, ymm10), 0xc4, 0x41, 0x7d, 0x51, 0xc2);
-    SINGLE_COMPARE(vsqrtpd(ymm8, ymmword[r9]), 0xc4, 0x41, 0xfd, 0x51, 0x01);
+    SINGLE_COMPARE(vsqrtpd(ymm8, ymmword[r9]), 0xc4, 0x41, 0x7d, 0x51, 0x01);
-    SINGLE_COMPARE(vsqrtps(xmm8, xmm10), 0xc4, 0x41, 0xf8, 0x51, 0xc2);
+    SINGLE_COMPARE(vsqrtps(xmm8, xmm10), 0xc4, 0x41, 0x78, 0x51, 0xc2);
-    SINGLE_COMPARE(vsqrtps(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf8, 0x51, 0x01);
+    SINGLE_COMPARE(vsqrtps(xmm8, xmmword[r9]), 0xc4, 0x41, 0x78, 0x51, 0x01);
-    SINGLE_COMPARE(vsqrtsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x51, 0xc6);
+    SINGLE_COMPARE(vsqrtsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x51, 0xc6);
-    SINGLE_COMPARE(vsqrtsd(xmm8, xmm10, qword[r9]), 0xc4, 0x41, 0xab, 0x51, 0x01);
+    SINGLE_COMPARE(vsqrtsd(xmm8, xmm10, qword[r9]), 0xc4, 0x41, 0x2b, 0x51, 0x01);
-    SINGLE_COMPARE(vsqrtss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xaa, 0x51, 0xc6);
+    SINGLE_COMPARE(vsqrtss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2a, 0x51, 0xc6);
-    SINGLE_COMPARE(vsqrtss(xmm8, xmm10, dword[r9]), 0xc4, 0x41, 0xaa, 0x51, 0x01);
+    SINGLE_COMPARE(vsqrtss(xmm8, xmm10, dword[r9]), 0xc4, 0x41, 0x2a, 0x51, 0x01);
 
     // Coverage for other instructions that follow the same pattern
-    SINGLE_COMPARE(vucomisd(xmm1, xmm4), 0xc4, 0xe1, 0xf9, 0x2e, 0xcc);
+    SINGLE_COMPARE(vucomisd(xmm1, xmm4), 0xc4, 0xe1, 0x79, 0x2e, 0xcc);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXMoveInstructionForms")
 {
-    SINGLE_COMPARE(vmovsd(qword[r9], xmm10), 0xc4, 0x41, 0xfb, 0x11, 0x11);
+    SINGLE_COMPARE(vmovsd(qword[r9], xmm10), 0xc4, 0x41, 0x7b, 0x11, 0x11);
-    SINGLE_COMPARE(vmovsd(xmm8, qword[r9]), 0xc4, 0x41, 0xfb, 0x10, 0x01);
+    SINGLE_COMPARE(vmovsd(xmm8, qword[r9]), 0xc4, 0x41, 0x7b, 0x10, 0x01);
-    SINGLE_COMPARE(vmovsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xab, 0x10, 0xc6);
+    SINGLE_COMPARE(vmovsd(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2b, 0x10, 0xc6);
-    SINGLE_COMPARE(vmovss(dword[r9], xmm10), 0xc4, 0x41, 0xfa, 0x11, 0x11);
+    SINGLE_COMPARE(vmovss(dword[r9], xmm10), 0xc4, 0x41, 0x7a, 0x11, 0x11);
-    SINGLE_COMPARE(vmovss(xmm8, dword[r9]), 0xc4, 0x41, 0xfa, 0x10, 0x01);
+    SINGLE_COMPARE(vmovss(xmm8, dword[r9]), 0xc4, 0x41, 0x7a, 0x10, 0x01);
-    SINGLE_COMPARE(vmovss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0xaa, 0x10, 0xc6);
+    SINGLE_COMPARE(vmovss(xmm8, xmm10, xmm14), 0xc4, 0x41, 0x2a, 0x10, 0xc6);
-    SINGLE_COMPARE(vmovapd(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf9, 0x28, 0x01);
+    SINGLE_COMPARE(vmovapd(xmm8, xmmword[r9]), 0xc4, 0x41, 0x79, 0x28, 0x01);
-    SINGLE_COMPARE(vmovapd(xmmword[r9], xmm10), 0xc4, 0x41, 0xf9, 0x29, 0x11);
+    SINGLE_COMPARE(vmovapd(xmmword[r9], xmm10), 0xc4, 0x41, 0x79, 0x29, 0x11);
-    SINGLE_COMPARE(vmovapd(ymm8, ymmword[r9]), 0xc4, 0x41, 0xfd, 0x28, 0x01);
+    SINGLE_COMPARE(vmovapd(ymm8, ymmword[r9]), 0xc4, 0x41, 0x7d, 0x28, 0x01);
-    SINGLE_COMPARE(vmovaps(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf8, 0x28, 0x01);
+    SINGLE_COMPARE(vmovaps(xmm8, xmmword[r9]), 0xc4, 0x41, 0x78, 0x28, 0x01);
-    SINGLE_COMPARE(vmovaps(xmmword[r9], xmm10), 0xc4, 0x41, 0xf8, 0x29, 0x11);
+    SINGLE_COMPARE(vmovaps(xmmword[r9], xmm10), 0xc4, 0x41, 0x78, 0x29, 0x11);
-    SINGLE_COMPARE(vmovaps(ymm8, ymmword[r9]), 0xc4, 0x41, 0xfc, 0x28, 0x01);
+    SINGLE_COMPARE(vmovaps(ymm8, ymmword[r9]), 0xc4, 0x41, 0x7c, 0x28, 0x01);
-    SINGLE_COMPARE(vmovupd(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf9, 0x10, 0x01);
+    SINGLE_COMPARE(vmovupd(xmm8, xmmword[r9]), 0xc4, 0x41, 0x79, 0x10, 0x01);
-    SINGLE_COMPARE(vmovupd(xmmword[r9], xmm10), 0xc4, 0x41, 0xf9, 0x11, 0x11);
+    SINGLE_COMPARE(vmovupd(xmmword[r9], xmm10), 0xc4, 0x41, 0x79, 0x11, 0x11);
-    SINGLE_COMPARE(vmovupd(ymm8, ymmword[r9]), 0xc4, 0x41, 0xfd, 0x10, 0x01);
+    SINGLE_COMPARE(vmovupd(ymm8, ymmword[r9]), 0xc4, 0x41, 0x7d, 0x10, 0x01);
-    SINGLE_COMPARE(vmovups(xmm8, xmmword[r9]), 0xc4, 0x41, 0xf8, 0x10, 0x01);
+    SINGLE_COMPARE(vmovups(xmm8, xmmword[r9]), 0xc4, 0x41, 0x78, 0x10, 0x01);
-    SINGLE_COMPARE(vmovups(xmmword[r9], xmm10), 0xc4, 0x41, 0xf8, 0x11, 0x11);
+    SINGLE_COMPARE(vmovups(xmmword[r9], xmm10), 0xc4, 0x41, 0x78, 0x11, 0x11);
-    SINGLE_COMPARE(vmovups(ymm8, ymmword[r9]), 0xc4, 0x41, 0xfc, 0x10, 0x01);
+    SINGLE_COMPARE(vmovups(ymm8, ymmword[r9]), 0xc4, 0x41, 0x7c, 0x10, 0x01);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXConversionInstructionForms")
@@ -407,10 +489,10 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXConversionInstructionForms")
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "AVXTernaryInstructionForms")
 {
-    SINGLE_COMPARE(vroundsd(xmm7, xmm12, xmm3, RoundingModeX64::RoundToNegativeInfinity), 0xc4, 0xe3, 0x99, 0x0b, 0xfb, 0x09);
+    SINGLE_COMPARE(vroundsd(xmm7, xmm12, xmm3, RoundingModeX64::RoundToNegativeInfinity), 0xc4, 0xe3, 0x19, 0x0b, 0xfb, 0x09);
     SINGLE_COMPARE(
-        vroundsd(xmm8, xmm13, xmmword[r13 + rdx], RoundingModeX64::RoundToPositiveInfinity), 0xc4, 0x43, 0x91, 0x0b, 0x44, 0x15, 0x00, 0x0a);
+        vroundsd(xmm8, xmm13, xmmword[r13 + rdx], RoundingModeX64::RoundToPositiveInfinity), 0xc4, 0x43, 0x11, 0x0b, 0x44, 0x15, 0x00, 0x0a);
-    SINGLE_COMPARE(vroundsd(xmm9, xmm14, xmmword[rcx + r10], RoundingModeX64::RoundToZero), 0xc4, 0x23, 0x89, 0x0b, 0x0c, 0x11, 0x0b);
+    SINGLE_COMPARE(vroundsd(xmm9, xmm14, xmmword[rcx + r10], RoundingModeX64::RoundToZero), 0xc4, 0x23, 0x09, 0x0b, 0x0c, 0x11, 0x0b);
 }
 
 TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "MiscInstructions")
@@ -423,6 +505,10 @@ TEST_CASE("LogTest")
     AssemblyBuilderX64 build(/* logText= */ true);
 
     build.push(r12);
+    build.align(8);
+    build.align(8, AlignmentDataX64::Int3);
+    build.align(8, AlignmentDataX64::Ud2);
+
     build.add(rax, rdi);
     build.add(rcx, 8);
     build.sub(dword[rax], 0x1fdc);
@@ -445,14 +531,29 @@ TEST_CASE("LogTest")
     build.imul(rcx, rdx);
     build.imul(rcx, rdx, 8);
     build.vroundsd(xmm1, xmm2, xmm3, RoundingModeX64::RoundToNearestEven);
+    build.add(rdx, qword[rcx - 12]);
     build.pop(r12);
     build.ret();
     build.int3();
 
+    build.nop();
+    build.nop(2);
+    build.nop(3);
+    build.nop(4);
+    build.nop(5);
+    build.nop(6);
+    build.nop(7);
+    build.nop(8);
+    build.nop(9);
+
     build.finalize();
 
     bool same = "\n" + build.text == R"(
  push        r12
+; align 8
+ nop         word ptr[rax+rax] ; 6-byte nop
+; align 8 using int3
+; align 8 using ud2
  add         rax,rdi
  add         rcx,8
  sub         dword ptr [rax],1FDCh
@@ -473,9 +574,19 @@ TEST_CASE("LogTest")
  imul        rcx,rdx
  imul        rcx,rdx,8
  vroundsd    xmm1,xmm2,xmm3,8
+ add         rdx,qword ptr [rcx-0Ch]
  pop         r12
  ret
  int3
+ nop
+ xchg        ax, ax ; 2-byte nop
+ nop         dword ptr[rax] ; 3-byte nop
+ nop         dword ptr[rax] ; 4-byte nop
+ nop         dword ptr[rax+rax] ; 5-byte nop
+ nop         word ptr[rax+rax] ; 6-byte nop
+ nop         dword ptr[rax] ; 7-byte nop
+ nop         dword ptr[rax+rax] ; 8-byte nop
+ nop         word ptr[rax+rax] ; 9-byte nop
 )";
     CHECK(same);
 }
@@ -497,10 +608,10 @@ TEST_CASE_FIXTURE(AssemblyBuilderX64Fixture, "Constants")
         {
             0x48, 0x33, 0xc0,
             0x48, 0x03, 0x05, 0xee, 0xff, 0xff, 0xff,
-            0xc4, 0xe1, 0xfa, 0x10, 0x15, 0xe1, 0xff, 0xff, 0xff,
+            0xc4, 0xe1, 0x7a, 0x10, 0x15, 0xe1, 0xff, 0xff, 0xff,
-            0xc4, 0xe1, 0xfb, 0x10, 0x1d, 0xcc, 0xff, 0xff, 0xff,
+            0xc4, 0xe1, 0x7b, 0x10, 0x1d, 0xcc, 0xff, 0xff, 0xff,
-            0xc4, 0xe1, 0xf8, 0x28, 0x25, 0xab, 0xff, 0xff, 0xff,
+            0xc4, 0xe1, 0x78, 0x28, 0x25, 0xab, 0xff, 0xff, 0xff,
-            0xc4, 0xe1, 0xf9, 0x10, 0x2d, 0x92, 0xff, 0xff, 0xff,
+            0xc4, 0xe1, 0x79, 0x10, 0x2d, 0x92, 0xff, 0xff, 0xff,
             0xc3
         },
         {

tests/CodeAllocator.test.cpp

@@ -41,9 +41,9 @@ TEST_CASE("CodeAllocation")
 
     REQUIRE(allocator.allocate(data.data(), data.size(), code.data(), code.size(), nativeData, sizeNativeData, nativeEntry));
     CHECK(nativeData != nullptr);
-    CHECK(sizeNativeData == 16 + 128);
+    CHECK(sizeNativeData == kCodeAlignment + 128);
     CHECK(nativeEntry != nullptr);
-    CHECK(nativeEntry == nativeData + 16);
+    CHECK(nativeEntry == nativeData + kCodeAlignment);
 }
 
 TEST_CASE("CodeAllocationFailure")
@@ -118,15 +118,16 @@ TEST_CASE("CodeAllocationWithUnwindCallbacks")
 
         REQUIRE(allocator.allocate(data.data(), data.size(), code.data(), code.size(), nativeData, sizeNativeData, nativeEntry));
         CHECK(nativeData != nullptr);
-        CHECK(sizeNativeData == 16 + 128);
+        CHECK(sizeNativeData == kCodeAlignment + 128);
         CHECK(nativeEntry != nullptr);
-        CHECK(nativeEntry == nativeData + 16);
+        CHECK(nativeEntry == nativeData + kCodeAlignment);
-        CHECK(nativeData == info.block + 16);
+        CHECK(nativeData == info.block + kCodeAlignment);
     }
 
     CHECK(info.destroyCalled);
 }
 
+#if !defined(LUAU_BIG_ENDIAN)
 TEST_CASE("WindowsUnwindCodesX64")
 {
     UnwindBuilderWin unwind;
@@ -156,6 +157,7 @@ TEST_CASE("WindowsUnwindCodesX64")
     REQUIRE(data.size() == expected.size());
     CHECK(memcmp(data.data(), expected.data(), expected.size()) == 0);
 }
+#endif
 
 TEST_CASE("Dwarf2UnwindCodesX64")
 {

tests/Compiler.test.cpp

@@ -798,8 +798,6 @@ RETURN R0 1
 
 TEST_CASE("TableSizePredictionSetMetatable")
 {
-    ScopedFastFlag sff("LuauCompileBuiltinMT", true);
-
     CHECK_EQ("\n" + compileFunction0(R"(
 local t = setmetatable({}, nil)
 t.field1 = 1

tests/Conformance.test.cpp

@@ -536,9 +536,15 @@ TEST_CASE("Debugger")
 {
     static int breakhits = 0;
     static lua_State* interruptedthread = nullptr;
+    static bool singlestep = false;
+    static int stephits = 0;
+
+    SUBCASE("") { singlestep = false; }
+    SUBCASE("SingleStep") { singlestep = true; }
 
     breakhits = 0;
     interruptedthread = nullptr;
+    stephits = 0;
 
     lua_CompileOptions copts = defaultOptions();
     copts.debugLevel = 2;
@@ -548,6 +554,13 @@ TEST_CASE("Debugger")
         [](lua_State* L) {
             lua_Callbacks* cb = lua_callbacks(L);
 
+            lua_singlestep(L, singlestep);
+
+            // this will only be called in single-step mode
+            cb->debugstep = [](lua_State* L, lua_Debug* ar) {
+                stephits++;
+            };
+
             // for breakpoints to work we should make sure debugbreak is installed
             cb->debugbreak = [](lua_State* L, lua_Debug* ar) {
                 breakhits++;
@@ -667,6 +680,9 @@ TEST_CASE("Debugger")
         nullptr, &copts, /* skipCodegen */ true); // Native code doesn't support debugging yet
 
     CHECK(breakhits == 12); // 2 hits per breakpoint
+
+    if (singlestep)
+        CHECK(stephits > 100); // note; this will depend on number of instructions which can vary, so we just make sure the callback gets hit often
 }
 
 TEST_CASE("SameHash")
@@ -1528,4 +1544,51 @@ TEST_CASE("SafeEnv")
     runConformance("safeenv.lua");
 }
 
+TEST_CASE("HugeFunction")
+{
+    std::string source;
+
+    // add non-executed block that requires JUMPKX and generates a lot of constants that take available short (15-bit) constant space
+    source += "if ... then\n";
+    source += "local _ = {\n";
+
+    for (int i = 0; i < 40000; ++i)
+    {
+        source += "0.";
+        source += std::to_string(i);
+        source += ",";
+    }
+
+    source += "}\n";
+    source += "end\n";
+
+    // use failed fast-calls with imports and constants to exercise all of the more complex fallback sequences
+    source += "return bit32.lshift('84', -1)";
+
+    StateRef globalState(luaL_newstate(), lua_close);
+    lua_State* L = globalState.get();
+
+    if (codegen && Luau::CodeGen::isSupported())
+        Luau::CodeGen::create(L);
+
+    luaL_openlibs(L);
+    luaL_sandbox(L);
+    luaL_sandboxthread(L);
+
+    size_t bytecodeSize = 0;
+    char* bytecode = luau_compile(source.data(), source.size(), nullptr, &bytecodeSize);
+    int result = luau_load(L, "=HugeFunction", bytecode, bytecodeSize, 0);
+    free(bytecode);
+
+    REQUIRE(result == 0);
+
+    if (codegen && Luau::CodeGen::isSupported())
+        Luau::CodeGen::compile(L, -1);
+
+    int status = lua_resume(L, nullptr, 0);
+    REQUIRE(status == 0);
+
+    CHECK(lua_tonumber(L, -1) == 42);
+}
+
 TEST_SUITE_END();

tests/ConstraintGraphBuilder.test.cpp

@@ -1,126 +0,0 @@
-// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
-
-#include "Luau/ConstraintGraphBuilder.h"
-#include "Luau/NotNull.h"
-#include "Luau/ToString.h"
-
-#include "ConstraintGraphBuilderFixture.h"
-#include "Fixture.h"
-#include "doctest.h"
-
-using namespace Luau;
-
-TEST_SUITE_BEGIN("ConstraintGraphBuilder");
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "hello_world")
-{
-    AstStatBlock* block = parse(R"(
-        local a = "hello"
-        local b = a
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    REQUIRE(2 == constraints.size());
-
-    ToStringOptions opts;
-    CHECK("string <: a" == toString(*constraints[0], opts));
-    CHECK("a <: b" == toString(*constraints[1], opts));
-}
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "primitives")
-{
-    AstStatBlock* block = parse(R"(
-        local s = "hello"
-        local n = 555
-        local b = true
-        local n2 = nil
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    REQUIRE(3 == constraints.size());
-
-    ToStringOptions opts;
-    CHECK("string <: a" == toString(*constraints[0], opts));
-    CHECK("number <: b" == toString(*constraints[1], opts));
-    CHECK("boolean <: c" == toString(*constraints[2], opts));
-}
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "nil_primitive")
-{
-    AstStatBlock* block = parse(R"(
-        local function a() return nil end
-        local b = a()
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    ToStringOptions opts;
-    REQUIRE(4 <= constraints.size());
-
-    CHECK("*blocked-1* ~ gen () -> (a...)" == toString(*constraints[0], opts));
-    CHECK("call *blocked-1* with { result = *blocked-tp-1* }" == toString(*constraints[1], opts));
-    CHECK("*blocked-tp-1* <: b" == toString(*constraints[2], opts));
-    CHECK("nil <: a..." == toString(*constraints[3], opts));
-}
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "function_application")
-{
-    AstStatBlock* block = parse(R"(
-        local a = "hello"
-        local b = a("world")
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    REQUIRE(3 == constraints.size());
-
-    ToStringOptions opts;
-    CHECK("string <: a" == toString(*constraints[0], opts));
-    CHECK("call a with { result = *blocked-tp-1* }" == toString(*constraints[1], opts));
-    CHECK("*blocked-tp-1* <: b" == toString(*constraints[2], opts));
-}
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "local_function_definition")
-{
-    AstStatBlock* block = parse(R"(
-        local function f(a)
-            return a
-        end
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    REQUIRE(2 == constraints.size());
-
-    ToStringOptions opts;
-    CHECK("*blocked-1* ~ gen (a) -> (b...)" == toString(*constraints[0], opts));
-    CHECK("a <: b..." == toString(*constraints[1], opts));
-}
-
-TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "recursive_function")
-{
-    AstStatBlock* block = parse(R"(
-        local function f(a)
-            return f(a)
-        end
-    )");
-
-    cgb.visit(block);
-    auto constraints = collectConstraints(NotNull(cgb.rootScope));
-
-    REQUIRE(3 == constraints.size());
-
-    ToStringOptions opts;
-    CHECK("*blocked-1* ~ gen (a) -> (b...)" == toString(*constraints[0], opts));
-    CHECK("call (a) -> (b...) with { result = *blocked-tp-1* }" == toString(*constraints[1], opts));
-    CHECK("*blocked-tp-1* <: b..." == toString(*constraints[2], opts));
-}
-
-TEST_SUITE_END();

tests/ConstraintGraphBuilderFixture.cpp

@@ -7,11 +7,28 @@ namespace Luau
 ConstraintGraphBuilderFixture::ConstraintGraphBuilderFixture()
     : Fixture()
     , mainModule(new Module)
-    , cgb("MainModule", mainModule, &arena, NotNull(&moduleResolver), singletonTypes, NotNull(&ice), frontend.getGlobalScope(), &logger)
     , forceTheFlag{"DebugLuauDeferredConstraintResolution", true}
 {
     BlockedTypeVar::nextIndex = 0;
     BlockedTypePack::nextIndex = 0;
 }
 
+void ConstraintGraphBuilderFixture::generateConstraints(const std::string& code)
+{
+    AstStatBlock* root = parse(code);
+    dfg = std::make_unique<DataFlowGraph>(DataFlowGraphBuilder::build(root, NotNull{&ice}));
+    cgb = std::make_unique<ConstraintGraphBuilder>("MainModule", mainModule, &arena, NotNull(&moduleResolver), singletonTypes, NotNull(&ice),
+        frontend.getGlobalScope(), &logger, NotNull{dfg.get()});
+    cgb->visit(root);
+    rootScope = cgb->rootScope;
+    constraints = Luau::collectConstraints(NotNull{cgb->rootScope});
+}
+
+void ConstraintGraphBuilderFixture::solve(const std::string& code)
+{
+    generateConstraints(code);
+    ConstraintSolver cs{NotNull{&normalizer}, NotNull{rootScope}, "MainModule", NotNull(&moduleResolver), {}, &logger};
+    cs.run();
+}
+
 } // namespace Luau

tests/ConstraintGraphBuilderFixture.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "Luau/ConstraintGraphBuilder.h"
+#include "Luau/ConstraintSolver.h"
 #include "Luau/DcrLogger.h"
 #include "Luau/TypeArena.h"
 #include "Luau/Module.h"
@@ -16,12 +17,22 @@ struct ConstraintGraphBuilderFixture : Fixture
 {
     TypeArena arena;
     ModulePtr mainModule;
-    ConstraintGraphBuilder cgb;
     DcrLogger logger;
+    UnifierSharedState sharedState{&ice};
+    Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
+
+    std::unique_ptr<DataFlowGraph> dfg;
+    std::unique_ptr<ConstraintGraphBuilder> cgb;
+    Scope* rootScope = nullptr;
+
+    std::vector<NotNull<Constraint>> constraints;
 
     ScopedFastFlag forceTheFlag;
 
     ConstraintGraphBuilderFixture();
+
+    void generateConstraints(const std::string& code);
+    void solve(const std::string& code);
 };
 
 } // namespace Luau

tests/ConstraintSolver.test.cpp

@@ -1,15 +1,12 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 
-#include "Luau/ConstraintGraphBuilder.h"
-#include "Luau/ConstraintSolver.h"
-
 #include "ConstraintGraphBuilderFixture.h"
 #include "Fixture.h"
 #include "doctest.h"
 
 using namespace Luau;
 
-static TypeId requireBinding(NotNull<Scope> scope, const char* name)
+static TypeId requireBinding(Scope* scope, const char* name)
 {
     auto b = linearSearchForBinding(scope, name);
     LUAU_ASSERT(b.has_value());
@@ -20,22 +17,11 @@ TEST_SUITE_BEGIN("ConstraintSolver");
 
 TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "hello")
 {
-    AstStatBlock* block = parse(R"(
+    solve(R"(
         local a = 55
         local b = a
     )");
 
-    cgb.visit(block);
-    NotNull<Scope> rootScope{cgb.rootScope};
-
-    InternalErrorReporter iceHandler;
-    UnifierSharedState sharedState{&iceHandler};
-    Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
-    NullModuleResolver resolver;
-    ConstraintSolver cs{NotNull{&normalizer}, rootScope, "MainModule", NotNull(&resolver), {}, &logger};
-
-    cs.run();
-
     TypeId bType = requireBinding(rootScope, "b");
 
     CHECK("number" == toString(bType));
@@ -43,22 +29,12 @@ TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "hello")
 
 TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "generic_function")
 {
-    AstStatBlock* block = parse(R"(
+    solve(R"(
         local function id(a)
             return a
         end
     )");
 
-    cgb.visit(block);
-    NotNull<Scope> rootScope{cgb.rootScope};
-
-    InternalErrorReporter iceHandler;
-    UnifierSharedState sharedState{&iceHandler};
-    Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
-    NullModuleResolver resolver;
-    ConstraintSolver cs{NotNull{&normalizer}, rootScope, "MainModule", NotNull(&resolver), {}, &logger};
-    cs.run();
-
     TypeId idType = requireBinding(rootScope, "id");
 
     CHECK("<a>(a) -> a" == toString(idType));
@@ -66,7 +42,7 @@ TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "generic_function")
 
 TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "proper_let_generalization")
 {
-    AstStatBlock* block = parse(R"(
+    solve(R"(
         local function a(c)
             local function d(e)
                 return c
@@ -78,21 +54,9 @@ TEST_CASE_FIXTURE(ConstraintGraphBuilderFixture, "proper_let_generalization")
         local b = a(5)
     )");
 
-    cgb.visit(block);
-    NotNull<Scope> rootScope{cgb.rootScope};
-
-    ToStringOptions opts;
-
-    NullModuleResolver resolver;
-    InternalErrorReporter iceHandler;
-    UnifierSharedState sharedState{&iceHandler};
-    Normalizer normalizer{&arena, singletonTypes, NotNull{&sharedState}};
-    ConstraintSolver cs{NotNull{&normalizer}, rootScope, "MainModule", NotNull(&resolver), {}, &logger};
-
-    cs.run();
-
     TypeId idType = requireBinding(rootScope, "b");
 
+    ToStringOptions opts;
     CHECK("<a>(a) -> number" == toString(idType, opts));
 }
 

tests/DataFlowGraphBuilder.test.cpp

@@ -0,0 +1,104 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include "Luau/DataFlowGraphBuilder.h"
+#include "Luau/Error.h"
+#include "Luau/Parser.h"
+
+#include "AstQueryDsl.h"
+#include "ScopedFlags.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+class DataFlowGraphFixture
+{
+    // Only needed to fix the operator== reflexivity of an empty Symbol.
+    ScopedFastFlag dcr{"DebugLuauDeferredConstraintResolution", true};
+
+    InternalErrorReporter handle;
+
+    Allocator allocator;
+    AstNameTable names{allocator};
+    AstStatBlock* module;
+
+    std::optional<DataFlowGraph> graph;
+
+public:
+    void dfg(const std::string& code)
+    {
+        ParseResult parseResult = Parser::parse(code.c_str(), code.size(), names, allocator);
+        if (!parseResult.errors.empty())
+            throw ParseErrors(std::move(parseResult.errors));
+        module = parseResult.root;
+        graph = DataFlowGraphBuilder::build(module, NotNull{&handle});
+    }
+
+    template<typename T, int N>
+    std::optional<DefId> getDef(const std::vector<Nth>& nths = {nth<T>(N)})
+    {
+        T* node = query<T, N>(module, nths);
+        REQUIRE(node);
+        return graph->getDef(node);
+    }
+
+    template<typename T, int N>
+    DefId requireDef(const std::vector<Nth>& nths = {nth<T>(N)})
+    {
+        auto loc = getDef<T, N>(nths);
+        REQUIRE(loc);
+        return NotNull{*loc};
+    }
+};
+
+TEST_SUITE_BEGIN("DataFlowGraphBuilder");
+
+TEST_CASE_FIXTURE(DataFlowGraphFixture, "define_locals_in_local_stat")
+{
+    dfg(R"(
+        local x = 5
+        local y = x
+    )");
+
+    REQUIRE(getDef<AstExprLocal, 1>());
+}
+
+TEST_CASE_FIXTURE(DataFlowGraphFixture, "define_parameters_in_functions")
+{
+    dfg(R"(
+        local function f(x)
+            local y = x
+        end
+    )");
+
+    REQUIRE(getDef<AstExprLocal, 1>());
+}
+
+TEST_CASE_FIXTURE(DataFlowGraphFixture, "find_aliases")
+{
+    dfg(R"(
+        local x = 5
+        local y = x
+        local z = y
+    )");
+
+    DefId x = requireDef<AstExprLocal, 1>();
+    DefId y = requireDef<AstExprLocal, 2>();
+    REQUIRE(x != y); // TODO: they should be equal but it's not just locals that can alias, so we'll support this later.
+}
+
+TEST_CASE_FIXTURE(DataFlowGraphFixture, "independent_locals")
+{
+    dfg(R"(
+        local x = 5
+        local y = 5
+
+        local a = x
+        local b = y
+    )");
+
+    DefId x = requireDef<AstExprLocal, 1>();
+    DefId y = requireDef<AstExprLocal, 2>();
+    REQUIRE(x != y);
+}
+
+TEST_SUITE_END();

tests/Module.test.cpp

@@ -226,24 +226,6 @@ TEST_CASE_FIXTURE(Fixture, "clone_free_tables")
     CHECK_EQ(clonedTtv->state, TableState::Free);
 }
 
-TEST_CASE_FIXTURE(Fixture, "clone_constrained_intersection")
-{
-    TypeArena src;
-
-    TypeId constrained = src.addType(ConstrainedTypeVar{TypeLevel{}, {singletonTypes->numberType, singletonTypes->stringType}});
-
-    TypeArena dest;
-    CloneState cloneState;
-
-    TypeId cloned = clone(constrained, dest, cloneState);
-    CHECK_NE(constrained, cloned);
-
-    const ConstrainedTypeVar* ctv = get<ConstrainedTypeVar>(cloned);
-    REQUIRE_EQ(2, ctv->parts.size());
-    CHECK_EQ(singletonTypes->numberType, ctv->parts[0]);
-    CHECK_EQ(singletonTypes->stringType, ctv->parts[1]);
-}
-
 TEST_CASE_FIXTURE(BuiltinsFixture, "clone_self_property")
 {
     fileResolver.source["Module/A"] = R"(

tests/Normalize.test.cpp

@@ -391,26 +391,6 @@ TEST_SUITE_END();
 
 TEST_SUITE_BEGIN("Normalize");
 
-TEST_CASE_FIXTURE(NormalizeFixture, "union_with_overlapping_field_that_has_a_subtype_relationship")
-{
-    check(R"(
-        local t: {x: number} | {x: number?}
-    )");
-
-    ModulePtr tempModule{new Module};
-    tempModule->scopes.emplace_back(Location(), std::make_shared<Scope>(singletonTypes->anyTypePack));
-
-    // HACK: Normalization is an in-place operation.  We need to cheat a little here and unfreeze
-    // the arena that the type lives in.
-    ModulePtr mainModule = getMainModule();
-    unfreeze(mainModule->internalTypes);
-
-    TypeId tType = requireType("t");
-    normalize(tType, tempModule, singletonTypes, *typeChecker.iceHandler);
-
-    CHECK_EQ("{| x: number? |}", toString(tType, {true}));
-}
-
 TEST_CASE_FIXTURE(Fixture, "higher_order_function")
 {
     check(R"(

tests/Symbol.test.cpp

@@ -10,7 +10,7 @@ using namespace Luau;
 
 TEST_SUITE_BEGIN("SymbolTests");
 
-TEST_CASE("hashing_globals")
+TEST_CASE("equality_and_hashing_of_globals")
 {
     std::string s1 = "name";
     std::string s2 = "name";
@@ -37,7 +37,7 @@ TEST_CASE("hashing_globals")
     REQUIRE_EQ(1, theMap.size());
 }
 
-TEST_CASE("hashing_locals")
+TEST_CASE("equality_and_hashing_of_locals")
 {
     std::string s1 = "name";
     std::string s2 = "name";
@@ -64,4 +64,24 @@ TEST_CASE("hashing_locals")
     REQUIRE_EQ(2, theMap.size());
 }
 
+TEST_CASE("equality_of_empty_symbols")
+{
+    ScopedFastFlag sff{"DebugLuauDeferredConstraintResolution", true};
+
+    std::string s1 = "name";
+    std::string s2 = "name";
+
+    AstName one{s1.data()};
+    AstLocal two{AstName{s2.data()}, Location(), nullptr, 0, 0, nullptr};
+
+    Symbol global{one};
+    Symbol local{&two};
+    Symbol empty1{};
+    Symbol empty2{};
+
+    CHECK(empty1 != global);
+    CHECK(empty1 != local);
+    CHECK(empty1 == empty2);
+}
+
 TEST_SUITE_END();

tests/ToDot.test.cpp

@@ -79,8 +79,8 @@ n1 [label="AnyTypeVar 1"];
 TEST_CASE_FIXTURE(Fixture, "bound")
 {
     CheckResult result = check(R"(
-local a = 444
+function a(): number return 444 end
-local b = a
+local b = a()
 )");
     LUAU_REQUIRE_NO_ERRORS(result);
 
@@ -367,27 +367,6 @@ n3 [label="number"];
         toDot(*ty, opts));
 }
 
-TEST_CASE_FIXTURE(Fixture, "constrained")
-{
-    // ConstrainedTypeVars never appear in the final type graph, so we have to create one directly
-    // to dotify it.
-    TypeVar t{ConstrainedTypeVar{TypeLevel{}, {typeChecker.numberType, typeChecker.stringType, typeChecker.nilType}}};
-
-    ToDotOptions opts;
-    opts.showPointers = false;
-
-    CHECK_EQ(R"(digraph graphname {
-n1 [label="ConstrainedTypeVar 1"];
-n1 -> n2;
-n2 [label="number"];
-n1 -> n3;
-n3 [label="string"];
-n1 -> n4;
-n4 [label="nil"];
-})",
-        toDot(&t, opts));
-}
-
 TEST_CASE_FIXTURE(Fixture, "singletontypes")
 {
     CheckResult result = check(R"(

tests/TypeInfer.aliases.test.cpp

@@ -846,8 +846,16 @@ TEST_CASE_FIXTURE(Fixture, "forward_declared_alias_is_not_clobbered_by_prior_uni
         type FutureIntersection = A & B
     )");
 
-    // TODO: shared self causes this test to break in bizarre ways.
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    LUAU_REQUIRE_ERRORS(result);
+    {
+        // To be quite honest, I don't know exactly why DCR fixes this.
+        LUAU_REQUIRE_NO_ERRORS(result);
+    }
+    else
+    {
+        // TODO: shared self causes this test to break in bizarre ways.
+        LUAU_REQUIRE_ERRORS(result);
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "recursive_types_restriction_ok")

tests/TypeInfer.functions.test.cpp

@@ -1692,4 +1692,47 @@ foo(string.find("hello", "e"))
     CHECK_EQ(toString(result.errors[0]), "Argument count mismatch. Function 'foo' expects 0 to 2 arguments, but 3 are specified");
 }
 
+TEST_CASE_FIXTURE(Fixture, "luau_subtyping_is_np_hard")
+{
+    ScopedFastFlag sffs[]{
+        {"LuauSubtypeNormalizer", true},
+        {"LuauTypeNormalization2", true},
+        {"LuauOverloadedFunctionSubtypingPerf", true},
+    };
+
+    CheckResult result = check(R"(
+--!strict
+
+-- An example of coding up graph coloring in the Luau type system.
+-- This codes a three-node, two color problem.
+-- A three-node triangle is uncolorable,
+-- but a three-node line is colorable.
+
+type Red = "red"
+type Blue = "blue"
+type Color = Red | Blue
+type Coloring = (Color) -> (Color) -> (Color) -> boolean
+type Uncolorable = (Color) -> (Color) -> (Color) -> false
+
+type Line = Coloring
+  & ((Red) -> (Red) -> (Color) -> false)
+  & ((Blue) -> (Blue) -> (Color) -> false)
+  & ((Color) -> (Red) -> (Red) -> false)
+  & ((Color) -> (Blue) -> (Blue) -> false)
+
+type Triangle = Line
+  & ((Red) -> (Color) -> (Red) -> false)
+  & ((Blue) -> (Color) -> (Blue) -> false)
+
+local x : Triangle
+local y : Line
+local z : Uncolorable
+z = x -- OK, so the triangle is uncolorable
+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");
+}
+
 TEST_SUITE_END();

tests/TypeInfer.intersectionTypes.test.cpp

@@ -781,7 +781,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "intersect_metatables")
     CheckResult result = check(R"(
         local a : string? = nil
         local b : number? = nil
-    
+
         local x = setmetatable({}, { p = 5, q = a });
         local y = setmetatable({}, { q = b, r = "hi" });
         local z = setmetatable({}, { p = 5, q = nil, r = "hi" });

tests/TypeInfer.operators.test.cpp

@@ -13,6 +13,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
+
 TEST_SUITE_BEGIN("TypeInferOperators");
 
 TEST_CASE_FIXTURE(Fixture, "or_joins_types")
@@ -33,7 +35,7 @@ TEST_CASE_FIXTURE(Fixture, "or_joins_types_with_no_extras")
         local x:number|string = s
         local y = x or "s"
     )");
-    CHECK_EQ(0, result.errors.size());
+    LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ(toString(*requireType("s")), "number | string");
     CHECK_EQ(toString(*requireType("y")), "number | string");
 }
@@ -44,7 +46,7 @@ TEST_CASE_FIXTURE(Fixture, "or_joins_types_with_no_superfluous_union")
         local s = "a" or "b"
         local x:string = s
     )");
-    CHECK_EQ(0, result.errors.size());
+    LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ(*requireType("s"), *typeChecker.stringType);
 }
 
@@ -54,7 +56,7 @@ TEST_CASE_FIXTURE(Fixture, "and_adds_boolean")
         local s = "a" and 10
         local x:boolean|number = s
     )");
-    CHECK_EQ(0, result.errors.size());
+    LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ(toString(*requireType("s")), "boolean | number");
 }
 
@@ -64,7 +66,7 @@ TEST_CASE_FIXTURE(Fixture, "and_adds_boolean_no_superfluous_union")
         local s = "a" and true
         local x:boolean = s
     )");
-    CHECK_EQ(0, result.errors.size());
+    LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ(*requireType("x"), *typeChecker.booleanType);
 }
 
@@ -73,7 +75,7 @@ TEST_CASE_FIXTURE(Fixture, "and_or_ternary")
     CheckResult result = check(R"(
         local s = (1/2) > 0.5 and "a" or 10
     )");
-    CHECK_EQ(0, result.errors.size());
+    LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ(toString(*requireType("s")), "number | string");
 }
 
@@ -81,7 +83,7 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "primitive_arith_no_metatable")
 {
     CheckResult result = check(R"(
         function add(a: number, b: string)
-            return a + (tonumber(b) :: number), a .. b
+            return a + (tonumber(b) :: number), tostring(a) .. b
         end
         local n, s = add(2,"3")
     )");
@@ -558,15 +560,21 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "disallow_string_and_types_without_metatables
     LUAU_REQUIRE_ERROR_COUNT(3, result);
 
     TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
-    REQUIRE_EQ(*tm->wantedType, *typeChecker.numberType);
+    REQUIRE(tm);
-    REQUIRE_EQ(*tm->givenType, *typeChecker.stringType);
+    CHECK_EQ(*tm->wantedType, *typeChecker.numberType);
+    CHECK_EQ(*tm->givenType, *typeChecker.stringType);
+
+    GenericError* gen1 = get<GenericError>(result.errors[1]);
+    REQUIRE(gen1);
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+        CHECK_EQ(gen1->message, "Operator + is not applicable for '{ value: number }' and 'number' because neither type has a metatable");
+    else
+        CHECK_EQ(gen1->message, "Binary operator '+' not supported by types 'foo' and 'number'");
 
     TypeMismatch* tm2 = get<TypeMismatch>(result.errors[2]);
+    REQUIRE(tm2);
     CHECK_EQ(*tm2->wantedType, *typeChecker.numberType);
     CHECK_EQ(*tm2->givenType, *requireType("foo"));
-
-    GenericError* gen2 = get<GenericError>(result.errors[1]);
-    REQUIRE_EQ(gen2->message, "Binary operator '+' not supported by types 'foo' and 'number'");
 }
 
 // CLI-29033
@@ -611,12 +619,10 @@ TEST_CASE_FIXTURE(Fixture, "strict_binary_op_where_lhs_unknown")
 {
     std::vector<std::string> ops = {"+", "-", "*", "/", "%", "^", ".."};
 
-    std::string src = R"(
+    std::string src = "function foo(a, b)\n";
-        function foo(a, b)
-    )";
 
     for (const auto& op : ops)
-        src += "local _ = a " + op + "b\n";
+        src += "local _ = a " + op + " b\n";
 
     src += "end";
 
@@ -651,7 +657,11 @@ TEST_CASE_FIXTURE(Fixture, "error_on_invalid_operand_types_to_relational_operato
 
     GenericError* ge = get<GenericError>(result.errors[0]);
     REQUIRE(ge);
-    CHECK_EQ("Type 'boolean' cannot be compared with relational operator <", ge->message);
+
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+        CHECK_EQ("Types 'boolean' and 'boolean' cannot be compared with relational operator <", ge->message);
+    else
+        CHECK_EQ("Type 'boolean' cannot be compared with relational operator <", ge->message);
 }
 
 TEST_CASE_FIXTURE(Fixture, "error_on_invalid_operand_types_to_relational_operators2")
@@ -666,7 +676,10 @@ TEST_CASE_FIXTURE(Fixture, "error_on_invalid_operand_types_to_relational_operato
 
     GenericError* ge = get<GenericError>(result.errors[0]);
     REQUIRE(ge);
-    CHECK_EQ("Type 'number | string' cannot be compared with relational operator <", ge->message);
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+        CHECK_EQ("Types 'number | string' and 'number | string' cannot be compared with relational operator <", ge->message);
+    else
+        CHECK_EQ("Type 'number | string' cannot be compared with relational operator <", ge->message);
 }
 
 TEST_CASE_FIXTURE(Fixture, "cli_38355_recursive_union")
@@ -891,4 +904,63 @@ TEST_CASE_FIXTURE(BuiltinsFixture, "expected_types_through_binary_or")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "mm_ops_must_return_a_value")
+{
+    if (!FFlag::DebugLuauDeferredConstraintResolution)
+        return;
+
+    CheckResult result = check(R"(
+        local mm = {
+            __add = function(self, other)
+                return
+            end,
+        }
+
+        local x = setmetatable({}, mm)
+        local y = x + 123
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK(requireType("y") == singletonTypes->errorRecoveryType());
+
+    const GenericError* ge = get<GenericError>(result.errors[0]);
+    REQUIRE(ge);
+    CHECK(ge->message == "Metamethod '__add' must return a value");
+}
+
+TEST_CASE_FIXTURE(BuiltinsFixture, "mm_comparisons_must_return_a_boolean")
+{
+    if (!FFlag::DebugLuauDeferredConstraintResolution)
+        return;
+
+    CheckResult result = check(R"(
+        local mm1 = {
+            __lt = function(self, other)
+                return 123
+            end,
+        }
+
+        local mm2 = {
+            __lt = function(self, other)
+                return
+            end,
+        }
+
+        local o1 = setmetatable({}, mm1)
+        local v1 = o1 < o1
+
+        local o2 = setmetatable({}, mm2)
+        local v2 = o2 < o2
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+
+    CHECK(requireType("v1") == singletonTypes->booleanType);
+    CHECK(requireType("v2") == singletonTypes->booleanType);
+
+    CHECK(toString(result.errors[0]) == "Metamethod '__lt' must return type 'boolean'");
+    CHECK(toString(result.errors[1]) == "Metamethod '__lt' must return type 'boolean'");
+}
+
 TEST_SUITE_END();

tests/TypeInfer.refinements.test.cpp

@@ -8,6 +8,7 @@
 #include "doctest.h"
 
 LUAU_FASTFLAG(LuauSpecialTypesAsterisked)
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution)
 
 using namespace Luau;
 
@@ -49,7 +50,6 @@ struct RefinementClassFixture : Fixture
             {"Y", Property{typeChecker.numberType}},
             {"Z", Property{typeChecker.numberType}},
         };
-        normalize(vec3, scope, arena, singletonTypes, *typeChecker.iceHandler);
 
         TypeId inst = arena.addType(ClassTypeVar{"Instance", {}, std::nullopt, std::nullopt, {}, nullptr, "Test"});
 
@@ -57,21 +57,17 @@ struct RefinementClassFixture : Fixture
         TypePackId isARets = arena.addTypePack({typeChecker.booleanType});
         TypeId isA = arena.addType(FunctionTypeVar{isAParams, isARets});
         getMutable<FunctionTypeVar>(isA)->magicFunction = magicFunctionInstanceIsA;
-        normalize(isA, scope, arena, singletonTypes, *typeChecker.iceHandler);
 
         getMutable<ClassTypeVar>(inst)->props = {
             {"Name", Property{typeChecker.stringType}},
             {"IsA", Property{isA}},
         };
-        normalize(inst, scope, arena, singletonTypes, *typeChecker.iceHandler);
 
         TypeId folder = typeChecker.globalTypes.addType(ClassTypeVar{"Folder", {}, inst, std::nullopt, {}, nullptr, "Test"});
-        normalize(folder, scope, arena, singletonTypes, *typeChecker.iceHandler);
         TypeId part = typeChecker.globalTypes.addType(ClassTypeVar{"Part", {}, inst, std::nullopt, {}, nullptr, "Test"});
         getMutable<ClassTypeVar>(part)->props = {
             {"Position", Property{vec3}},
         };
-        normalize(part, scope, arena, singletonTypes, *typeChecker.iceHandler);
 
         typeChecker.globalScope->exportedTypeBindings["Vector3"] = TypeFun{{}, vec3};
         typeChecker.globalScope->exportedTypeBindings["Instance"] = TypeFun{{}, inst};
@@ -102,8 +98,16 @@ TEST_CASE_FIXTURE(Fixture, "is_truthy_constraint")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("string", toString(requireTypeAtPosition({3, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("nil", toString(requireTypeAtPosition({5, 26})));
+    {
+        CHECK_EQ("(string?) & ~(false?)", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({5, 26})));
+    }
+    else
+    {
+        CHECK_EQ("string", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("nil", toString(requireTypeAtPosition({5, 26})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "invert_is_truthy_constraint")
@@ -120,8 +124,16 @@ TEST_CASE_FIXTURE(Fixture, "invert_is_truthy_constraint")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("nil", toString(requireTypeAtPosition({3, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("string", toString(requireTypeAtPosition({5, 26})));
+    {
+        CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("(string?) & ~~~(false?)", toString(requireTypeAtPosition({5, 26})));
+    }
+    else
+    {
+        CHECK_EQ("nil", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("string", toString(requireTypeAtPosition({5, 26})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "parenthesized_expressions_are_followed_through")
@@ -138,8 +150,16 @@ TEST_CASE_FIXTURE(Fixture, "parenthesized_expressions_are_followed_through")
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ("nil", toString(requireTypeAtPosition({3, 26})));
+    if (FFlag::DebugLuauDeferredConstraintResolution)
-    CHECK_EQ("string", toString(requireTypeAtPosition({5, 26})));
+    {
+        CHECK_EQ("(string?) & ~~(false?)", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("(string?) & ~~~(false?)", toString(requireTypeAtPosition({5, 26})));
+    }
+    else
+    {
+        CHECK_EQ("nil", toString(requireTypeAtPosition({3, 26})));
+        CHECK_EQ("string", toString(requireTypeAtPosition({5, 26})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "and_constraint")
@@ -963,19 +983,27 @@ TEST_CASE_FIXTURE(Fixture, "and_or_peephole_refinement")
 TEST_CASE_FIXTURE(Fixture, "narrow_boolean_to_true_or_false")
 {
     CheckResult result = check(R"(
-        local function is_true(b: true) end
-        local function is_false(b: false) end
-
         local function f(x: boolean)
             if x then
-                is_true(x)
+                local foo = x
             else
-                is_false(x)
+                local foo = x
             end
         end
     )");
 
     LUAU_REQUIRE_NO_ERRORS(result);
+
+    if (FFlag::DebugLuauDeferredConstraintResolution)
+    {
+        CHECK_EQ("boolean & ~(false?)", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("boolean & ~~(false?)", toString(requireTypeAtPosition({5, 28})));
+    }
+    else
+    {
+        CHECK_EQ("true", toString(requireTypeAtPosition({3, 28})));
+        CHECK_EQ("false", toString(requireTypeAtPosition({5, 28})));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "discriminate_on_properties_of_disjoint_tables_where_that_property_is_true_or_false")

tests/TypeInfer.tables.test.cpp

@@ -11,6 +11,8 @@
 
 using namespace Luau;
 
+LUAU_FASTFLAG(LuauLowerBoundsCalculation);
+LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 LUAU_FASTFLAG(LuauInstantiateInSubtyping)
 
 TEST_SUITE_BEGIN("TableTests");
@@ -44,7 +46,7 @@ TEST_CASE_FIXTURE(Fixture, "augment_table")
     const TableTypeVar* tType = get<TableTypeVar>(requireType("t"));
     REQUIRE(tType != nullptr);
 
-    CHECK(tType->props.find("foo") != tType->props.end());
+    CHECK(1 == tType->props.count("foo"));
 }
 
 TEST_CASE_FIXTURE(Fixture, "augment_nested_table")
@@ -101,7 +103,11 @@ TEST_CASE_FIXTURE(Fixture, "updating_sealed_table_prop_is_ok")
 
 TEST_CASE_FIXTURE(Fixture, "cannot_change_type_of_unsealed_table_prop")
 {
-    CheckResult result = check("local t = {}    t.prop = 999    t.prop = 'hello'");
+    CheckResult result = check(R"(
+        local t = {}
+        t.prop = 999
+        t.prop = 'hello'
+    )");
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
@@ -858,11 +864,12 @@ TEST_CASE_FIXTURE(Fixture, "assigning_to_an_unsealed_table_with_string_literal_s
 
     LUAU_REQUIRE_NO_ERRORS(result);
 
-    CHECK_EQ(*typeChecker.stringType, *requireType("a"));
+    CHECK("string" == toString(*typeChecker.stringType));
 
     TableTypeVar* tableType = getMutable<TableTypeVar>(requireType("t"));
     REQUIRE(tableType != nullptr);
     REQUIRE(tableType->indexer == std::nullopt);
+    REQUIRE(0 != tableType->props.count("a"));
 
     TypeId propertyA = tableType->props["a"].type;
     REQUIRE(propertyA != nullptr);
@@ -2390,9 +2397,12 @@ TEST_CASE_FIXTURE(Fixture, "wrong_assign_does_hit_indexer")
 
 TEST_CASE_FIXTURE(Fixture, "nil_assign_doesnt_hit_no_indexer")
 {
-    CheckResult result = check("local a = {a=1, b=2} a['a'] = nil");
+    CheckResult result = check(R"(
+        local a = {a=1, b=2}
+        a['a'] = nil
+    )");
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ(result.errors[0], (TypeError{Location{Position{0, 30}, Position{0, 33}}, TypeMismatch{
+    CHECK_EQ(result.errors[0], (TypeError{Location{Position{2, 17}, Position{2, 20}}, TypeMismatch{
                                                                                           typeChecker.numberType,
                                                                                           typeChecker.nilType,
                                                                                       }}));
@@ -2701,6 +2711,62 @@ local baz = foo[bar]
     CHECK_EQ(result.errors[0].location, Location{Position{3, 16}, Position{3, 19}});
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_call_metamethod_basic")
+{
+    if (!FFlag::DebugLuauDeferredConstraintResolution)
+        return;
+
+    CheckResult result = check(R"(
+        local a = setmetatable({
+            a = 1,
+        }, {
+            __call = function(self, b: number)
+                return self.a * b
+            end,
+        })
+
+        local foo = a(12)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK(requireType("foo") == singletonTypes->numberType);
+}
+
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_call_metamethod_must_be_callable")
+{
+    CheckResult result = check(R"(
+        local a = setmetatable({}, {
+            __call = 123,
+        })
+
+        local foo = a()
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK(result.errors[0] == TypeError{
+                                  Location{{5, 20}, {5, 21}},
+                                  CannotCallNonFunction{singletonTypes->numberType},
+                              });
+}
+
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_call_metamethod_generic")
+{
+    CheckResult result = check(R"(
+        local a = setmetatable({}, {
+            __call = function<T>(self, b: T)
+                return b
+            end,
+        })
+
+        local foo = a(12)
+        local bar = a("bar")
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK(requireType("foo") == singletonTypes->numberType);
+    CHECK(requireType("bar") == singletonTypes->stringType);
+}
+
 TEST_CASE_FIXTURE(BuiltinsFixture, "table_simple_call")
 {
     CheckResult result = check(R"(

tests/TypeInfer.test.cpp

@@ -1046,7 +1046,6 @@ TEST_CASE_FIXTURE(Fixture, "type_infer_recursion_limit_normalizer")
     ScopedFastFlag sffs[]{
         {"LuauSubtypeNormalizer", true},
         {"LuauTypeNormalization2", true},
-        {"LuauAutocompleteDynamicLimits", true},
     };
 
     CheckResult result = check(R"(

tests/TypeInfer.typePacks.cpp

@@ -467,6 +467,8 @@ type I<S..., R...> = W<number, (string, S...), R...>
 
 TEST_CASE_FIXTURE(Fixture, "type_alias_type_pack_explicit")
 {
+    ScopedFastFlag sff("LuauFunctionReturnStringificationFixup", true);
+
     CheckResult result = check(R"(
 type X<T...> = (T...) -> (T...)
 
@@ -490,6 +492,8 @@ type F = X<(string, ...number)>
 
 TEST_CASE_FIXTURE(Fixture, "type_alias_type_pack_explicit_multi")
 {
+    ScopedFastFlag sff("LuauFunctionReturnStringificationFixup", true);
+
     CheckResult result = check(R"(
 type Y<T..., U...> = (T...) -> (U...)
 

tests/TypeVar.test.cpp

@@ -436,7 +436,6 @@ TEST_CASE("proof_that_isBoolean_uses_all_of")
 TEST_CASE("content_reassignment")
 {
     TypeVar myAny{AnyTypeVar{}, /*presistent*/ true};
-    myAny.normal = true;
     myAny.documentationSymbol = "@global/any";
 
     TypeArena arena;
@@ -446,7 +445,6 @@ TEST_CASE("content_reassignment")
 
     CHECK(get<AnyTypeVar>(futureAny) != nullptr);
     CHECK(!futureAny->persistent);
-    CHECK(futureAny->normal);
     CHECK(futureAny->documentationSymbol == "@global/any");
     CHECK(futureAny->owningArena == &arena);
 }

tests/conformance/basic.lua

@@ -93,7 +93,10 @@ assert((function() local a = 1 a = a * 2 return a end)() == 2)
 assert((function() local a = 1 a = a / 2 return a end)() == 0.5)
 assert((function() local a = 5 a = a % 2 return a end)() == 1)
 assert((function() local a = 3 a = a ^ 2 return a end)() == 9)
+assert((function() local a = 3 a = a ^ 3 return a end)() == 27)
 assert((function() local a = 9 a = a ^ 0.5 return a end)() == 3)
+assert((function() local a = -2 a = a ^ 2 return a end)() == 4)
+assert((function() local a = -2 a = a ^ 0.5 return tostring(a) end)() == "nan")
 
 assert((function() local a = '1' a = a .. '2' return a end)() == "12")
 assert((function() local a = '1' a = a .. '2' .. '3' return a end)() == "123")
@@ -706,7 +709,11 @@ end
 assert(chainTest(100) == "v0,v100")
 
 -- this validates import fallbacks
+assert(idontexist == nil)
+assert(math.idontexist == nil)
 assert(pcall(function() return idontexist.a end) == false)
+assert(pcall(function() return math.pow.a end) == false)
+assert(pcall(function() return math.a.b end) == false)
 
 -- make sure that NaN is preserved by the bytecode compiler
 local realnan = tostring(math.abs(0)/math.abs(0))

tests/conformance/calls.lua

@@ -226,4 +226,14 @@ assert((function () return nil end)(4) == nil)
 assert((function () local a; return a end)(4) == nil)
 assert((function (a) return a end)() == nil)
 
+-- C-stack overflow while handling C-stack overflow
+if not limitedstack then
+  local function loop ()
+    assert(pcall(loop))
+  end
+
+  local err, msg = xpcall(loop, loop)
+  assert(not err and string.find(msg, "error"))
+end
+
 return('OK')

tests/conformance/datetime.lua

@@ -16,6 +16,7 @@ D = os.date("*t", t)
 assert(os.date(string.rep("%d", 1000), t) ==
        string.rep(os.date("%d", t), 1000))
 assert(os.date(string.rep("%", 200)) == string.rep("%", 100))
+assert(os.date("", -1) == nil)
 
 local function checkDateTable (t)
   local D = os.date("!*t", t)

tests/conformance/errors.lua

@@ -405,5 +405,7 @@ assert(ecall(function() (""):foo() end) == "attempt to call missing method 'foo'
 assert(ecall(function() (42):foo() end) == "attempt to index number with 'foo'")
 assert(ecall(function() ({foo=42}):foo() end) == "attempt to call a number value")
 assert(ecall(function() local ud = newproxy(true) getmetatable(ud).__index = {} ud:foo() end) == "attempt to call missing method 'foo' of userdata")
+assert(ecall(function() local ud = newproxy(true) getmetatable(ud).__index = function() end ud:foo() end) == "attempt to call missing method 'foo' of userdata")
+assert(ecall(function() local ud = newproxy(true) getmetatable(ud).__index = function() error("nope") end ud:foo() end) == "nope")
 
 return('OK')

tests/conformance/events.lua

@@ -13,6 +13,11 @@ assert(getmetatable(a) == "xuxu")
 ud=newproxy(true); getmetatable(ud).__metatable = "xuxu"
 assert(getmetatable(ud) == "xuxu")
 
+assert(pcall(getmetatable) == false)
+assert(pcall(function() return getmetatable() end) == false)
+assert(select(2, pcall(getmetatable, {})) == nil)
+assert(select(2, pcall(getmetatable, ud)) == "xuxu")
+
 local res,err = pcall(tostring, a)
 assert(not res and err == "'__tostring' must return a string")
 -- cannot change a protected metatable
@@ -475,6 +480,9 @@ function testfenv()
 
   assert(_G.X == 20)
   assert(_G == getfenv(0))
+
+  assert(pcall(getfenv, 10) == false)
+  assert(pcall(setfenv, setfenv, {}) == false)
 end
 
 testfenv() -- DONT MOVE THIS LINE

tests/conformance/iter.lua

@@ -193,4 +193,24 @@ do
   assert(x == 15)
 end
 
+-- pairs/ipairs/next may be substituted through getfenv
+-- however, they *must* be substituted with functions - we don't support them falling back to generalized iteration
+function testgetfenv()
+  local env = getfenv(1)
+  env.pairs = function() return "nope" end
+  env.ipairs = function() return "nope" end
+  env.next = {1, 2, 3}
+
+  local ok, err = pcall(function() for k, v in pairs({}) do end end)
+  assert(not ok and err:match("attempt to iterate over a string value"))
+
+  local ok, err = pcall(function() for k, v in ipairs({}) do end end)
+  assert(not ok and err:match("attempt to iterate over a string value"))
+
+  local ok, err = pcall(function() for k, v in next, {} do end end)
+  assert(not ok and err:match("attempt to iterate over a table value"))
+end
+
+testgetfenv() -- DONT MOVE THIS LINE
+
 return"OK"

tests/conformance/math.lua

@@ -283,6 +283,13 @@ assert(math.fmod(-3, 2) == -1)
 assert(math.fmod(3, -2) == 1)
 assert(math.fmod(-3, -2) == -1)
 
+-- pow
+assert(math.pow(2, 0) == 1)
+assert(math.pow(2, 2) == 4)
+assert(math.pow(4, 0.5) == 2)
+assert(math.pow(-2, 2) == 4)
+assert(tostring(math.pow(-2, 0.5)) == "nan")
+
 -- most of the tests above go through fastcall path
 -- to make sure the basic implementations are also correct we test these functions with string->number coercions
 assert(math.abs("-4") == 4)

tests/conformance/move.lua

@@ -74,4 +74,6 @@ checkerror("wrap around", table.move, {}, 1, maxI, 2)
 checkerror("wrap around", table.move, {}, 1, 2, maxI)
 checkerror("wrap around", table.move, {}, minI, -2, 2)
 
+checkerror("readonly", table.move, table.freeze({}), 1, 1, 1)
+
 return"OK"

tests/conformance/strings.lua

@@ -48,6 +48,7 @@ assert(string.find("", "") == 1)
 assert(string.find('', 'aaa', 1) == nil)
 assert(('alo(.)alo'):find('(.)', 1, 1) == 4)
 assert(string.find('', '1', 2) == nil)
+assert(string.find('123', '2', 0) == 2)
 print('+')
 
 assert(string.len("") == 0)
@@ -88,6 +89,8 @@ assert(string.lower("\0ABCc%$") == "\0abcc%$")
 assert(string.rep('teste', 0) == '')
 assert(string.rep('tés\00tê', 2) == 'tés\0têtés\000tê')
 assert(string.rep('', 10) == '')
+assert(string.rep('', 1e9) == '')
+assert(pcall(string.rep, 'x', 2e9) == false)
 
 assert(string.reverse"" == "")
 assert(string.reverse"\0\1\2\3" == "\3\2\1\0")
@@ -126,6 +129,13 @@ assert(string.format("-%.20s.20s", string.rep("%", 2000)) == "-"..string.rep("%"
 assert(string.format('"-%20s.20s"', string.rep("%", 2000)) ==
        string.format("%q", "-"..string.rep("%", 2000)..".20s"))
 
+assert(string.format("%o %u %x %X", -1, -1, -1, -1) == "1777777777777777777777 18446744073709551615 ffffffffffffffff FFFFFFFFFFFFFFFF")
+
+assert(string.format("%e %E", 1.5, -1.5) == "1.500000e+00 -1.500000E+00")
+
+assert(pcall(string.format, "%##################d", 1) == false)
+assert(pcall(string.format, "%.123d", 1) == false)
+assert(pcall(string.format, "%?", 1) == false)
 
 -- longest number that can be formated
 assert(string.len(string.format('%99.99f', -1e308)) >= 100)
@@ -179,6 +189,26 @@ assert(table.concat(a, ",", 2) == "b,c")
 assert(table.concat(a, ",", 3) == "c")
 assert(table.concat(a, ",", 4) == "")
 
+-- string.split
+do
+  local function eq(a, b)
+    if #a ~= #b then
+      return false
+    end
+    for i=1,#a do
+      if a[i] ~= b[i] then
+        return false
+      end
+    end
+    return true
+  end
+
+  assert(eq(string.split("abc", ""), {'a', 'b', 'c'}))
+  assert(eq(string.split("abc", "b"), {'a', 'c'}))
+  assert(eq(string.split("abc", "d"), {'abc'}))
+  assert(eq(string.split("abc", "c"), {'ab', ''}))
+end
+
 --[[
 local locales = { "ptb", "ISO-8859-1", "pt_BR" }
 local function trylocale (w)