Sync to upstream/release/656 (#1612)

# General

All code has been re-formatted by `clang-format`; this is not
mechanically enforced, so Luau may go out-of-sync over the course of the
year.

# New Solver

* Track free types interior to a block of code on `Scope`, which should
reduce the number of free types that remain un-generalized after type
checking is complete (e.g.: less errors like `'a <: number is
incompatible with number`).

# Autocomplete

* Fragment autocomplete now does *not* provide suggestions within
comments (matching non-fragment autocomplete behavior).
* Autocomplete now respects iteration and recursion limits (some hangs
will now early exit with a "unification too complex error," some crashes
will now become internal complier exceptions).

# Runtime

* Add a limit to how many Luau codegen slot nodes addresses can be in
use at the same time (fixes #1605, fixes #1558).
* Added constant folding for vector arithmetic (fixes #1553).
* Added support for `buffer.readbits` and `buffer.writebits` (see:
luau-lang/rfcs#18).

---

Co-authored-by: Aaron Weiss <[email protected]>
Co-authored-by: David Cope <[email protected]>
Co-authored-by: Hunter Goldstein <[email protected]>
Co-authored-by: Vighnesh Vijay <[email protected]>
Co-authored-by: Vyacheslav Egorov <[email protected]>

Analysis/include/Luau/FragmentAutocomplete.h

@@ -15,6 +15,12 @@ namespace Luau
 {
 struct FrontendOptions;
 
+enum class FragmentTypeCheckStatus
+{
+    Success,
+    SkipAutocomplete,
+};
+
 struct FragmentAutocompleteAncestryResult
 {
     DenseHashMap<AstName, AstLocal*> localMap{AstName()};
@@ -29,6 +35,7 @@ struct FragmentParseResult
     AstStatBlock* root = nullptr;
     std::vector<AstNode*> ancestry;
     AstStat* nearestStatement = nullptr;
+    std::vector<Comment> commentLocations;
     std::unique_ptr<Allocator> alloc = std::make_unique<Allocator>();
 };
 
@@ -56,7 +63,7 @@ FragmentParseResult parseFragment(
     std::optional<Position> fragmentEndPosition
 );
 
-FragmentTypeCheckResult typecheckFragment(
+std::pair<FragmentTypeCheckStatus, FragmentTypeCheckResult> typecheckFragment(
     Frontend& frontend,
     const ModuleName& moduleName,
     const Position& cursorPos,

Analysis/include/Luau/Module.h

@@ -16,6 +16,8 @@
 #include <unordered_map>
 #include <optional>
 
+LUAU_FASTFLAG(LuauIncrementalAutocompleteCommentDetection)
+
 namespace Luau
 {
 
@@ -55,6 +57,7 @@ struct SourceModule
     }
 };
 
+bool isWithinComment(const std::vector<Comment>& commentLocations, Position pos);
 bool isWithinComment(const SourceModule& sourceModule, Position pos);
 bool isWithinComment(const ParseResult& result, Position pos);
 

Analysis/include/Luau/Scope.h

@@ -95,6 +95,8 @@ struct Scope
     // we need that the generic type `T` in both cases is the same, so we use a cache.
     std::unordered_map<Name, TypeId> typeAliasTypeParameters;
     std::unordered_map<Name, TypePackId> typeAliasTypePackParameters;
+
+    std::optional<std::vector<TypeId>> interiorFreeTypes;
 };
 
 // Returns true iff the left scope encloses the right scope.  A Scope* equal to

Analysis/include/Luau/Type.h

@@ -626,7 +626,7 @@ struct TypeFunctionInstanceType
     std::vector<TypeId> typeArguments;
     std::vector<TypePackId> packArguments;
 
-    std::optional<AstName> userFuncName;          // Name of the user-defined type function; only available for UDTFs
+    std::optional<AstName> userFuncName; // Name of the user-defined type function; only available for UDTFs
     UserDefinedFunctionData userFuncData;
 
     TypeFunctionInstanceType(

Analysis/include/Luau/TypeFunction.h

@@ -71,7 +71,7 @@ struct TypeFunctionContext
     // The constraint being reduced in this run of the reduction
     const Constraint* constraint;
 
-    std::optional<AstName> userFuncName;          // Name of the user-defined type function; only available for UDTFs
+    std::optional<AstName> userFuncName; // Name of the user-defined type function; only available for UDTFs
 
     TypeFunctionContext(NotNull<ConstraintSolver> cs, NotNull<Scope> scope, NotNull<const Constraint> constraint);
 

Analysis/include/Luau/TypeUtils.h

@@ -269,8 +269,8 @@ bool isLiteral(const AstExpr* expr);
 std::vector<TypeId> findBlockedTypesIn(AstExprTable* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes);
 
 /**
- * Given a function call and a mapping from expression to type, determine 
- * whether the type of any argument in said call in depends on a blocked types. 
+ * Given a function call and a mapping from expression to type, determine
+ * whether the type of any argument in said call in depends on a blocked types.
  * This is used as a precondition for bidirectional inference: be warned that
  * the behavior of this algorithm is tightly coupled to that of bidirectional
  * inference.
@@ -280,4 +280,13 @@ std::vector<TypeId> findBlockedTypesIn(AstExprTable* expr, NotNull<DenseHashMap<
  */
 std::vector<TypeId> findBlockedArgTypesIn(AstExprCall* expr, NotNull<DenseHashMap<const AstExpr*, TypeId>> astTypes);
 
+/**
+ * Given a scope and a free type, find the closest parent that has a present
+ * `interiorFreeTypes` and append the given type to said list. This list will
+ * be generalized when the requiste `GeneralizationConstraint` is resolved.
+ * @param scope Initial scope this free type was attached to
+ * @param ty Free type to track.
+ */
+void trackInteriorFreeType(Scope* scope, TypeId ty);
+
 } // namespace Luau

Analysis/src/AnyTypeSummary.cpp

@@ -177,7 +177,6 @@ void AnyTypeSummary::visit(const Scope* scope, AstStatReturn* ret, const Module*
             }
         }
     }
-
 }
 
 void AnyTypeSummary::visit(const Scope* scope, AstStatLocal* local, const Module* module, NotNull<BuiltinTypes> builtinTypes)

Analysis/src/AutocompleteCore.cpp

@@ -25,6 +25,7 @@ LUAU_FASTINT(LuauTypeInferIterationLimit)
 LUAU_FASTINT(LuauTypeInferRecursionLimit)
 
 LUAU_FASTFLAGVARIABLE(LuauAutocompleteRefactorsForIncrementalAutocomplete)
+LUAU_FASTFLAGVARIABLE(LuauAutocompleteUseLimits)
 
 static const std::unordered_set<std::string> kStatementStartingKeywords =
     {"while", "if", "local", "repeat", "function", "do", "for", "return", "break", "continue", "type", "export"};
@@ -177,6 +178,12 @@ static bool checkTypeMatch(TypeId subTy, TypeId superTy, NotNull<Scope> scope, T
         unifier.normalize = false;
         unifier.checkInhabited = false;
 
+        if (FFlag::LuauAutocompleteUseLimits)
+        {
+            unifierState.counters.recursionLimit = FInt::LuauTypeInferRecursionLimit;
+            unifierState.counters.iterationLimit = FInt::LuauTypeInferIterationLimit;
+        }
+
         return unifier.canUnify(subTy, superTy).empty();
     }
 }

Analysis/src/BuiltinDefinitions.cpp

@@ -611,7 +611,9 @@ static void dcrMagicFunctionTypeCheckFormat(MagicFunctionTypeCheckContext contex
     if (!fmt)
     {
         if (FFlag::LuauStringFormatArityFix)
-            context.typechecker->reportError(CountMismatch{1, std::nullopt, 0, CountMismatch::Arg, true, "string.format"}, context.callSite->location);
+            context.typechecker->reportError(
+                CountMismatch{1, std::nullopt, 0, CountMismatch::Arg, true, "string.format"}, context.callSite->location
+            );
         return;
     }
 

Analysis/src/Constraint.cpp

@@ -62,7 +62,6 @@ struct ReferenceCountInitializer : TypeOnceVisitor
         // of this type, hence:
         return !FFlag::LuauDontRefCountTypesInTypeFunctions;
     }
-
 };
 
 bool isReferenceCountedType(const TypeId typ)

Analysis/src/ConstraintGenerator.cpp

@@ -31,15 +31,15 @@
 LUAU_FASTINT(LuauCheckRecursionLimit)
 LUAU_FASTFLAG(DebugLuauLogSolverToJson)
 LUAU_FASTFLAG(DebugLuauMagicTypes)
-LUAU_FASTFLAG(DebugLuauEqSatSimplification)
 LUAU_FASTFLAG(LuauTypestateBuiltins2)
 LUAU_FASTFLAG(LuauUserTypeFunUpdateAllEnvs)
 
 LUAU_FASTFLAGVARIABLE(LuauNewSolverVisitErrorExprLvalues)
-LUAU_FASTFLAGVARIABLE(LuauNewSolverPrePopulateClasses)
 LUAU_FASTFLAGVARIABLE(LuauUserTypeFunExportedAndLocal)
+LUAU_FASTFLAGVARIABLE(LuauNewSolverPrePopulateClasses)
 LUAU_FASTFLAGVARIABLE(LuauNewSolverPopulateTableLocations)
 LUAU_FASTFLAGVARIABLE(LuauUserTypeFunNoExtraConstraint)
+LUAU_FASTFLAGVARIABLE(LuauTrackInteriorFreeTypesOnScope)
 
 LUAU_FASTFLAGVARIABLE(InferGlobalTypes)
 
@@ -233,8 +233,17 @@ void ConstraintGenerator::visitModuleRoot(AstStatBlock* block)
     Checkpoint end = checkpoint(this);
 
     TypeId result = arena->addType(BlockedType{});
-    NotNull<Constraint> genConstraint =
-        addConstraint(scope, block->location, GeneralizationConstraint{result, moduleFnTy, std::move(interiorTypes.back())});
+    NotNull<Constraint> genConstraint = addConstraint(
+        scope,
+        block->location,
+        GeneralizationConstraint{
+            result, moduleFnTy, FFlag::LuauTrackInteriorFreeTypesOnScope ? std::vector<TypeId>{} : std::move(interiorTypes.back())
+        }
+    );
+
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+        scope->interiorFreeTypes = std::move(interiorTypes.back());
+
     getMutable<BlockedType>(result)->setOwner(genConstraint);
     forEachConstraint(
         start,
@@ -303,9 +312,19 @@ void ConstraintGenerator::visitFragmentRoot(const ScopePtr& resumeScope, AstStat
     }
 }
 
+
 TypeId ConstraintGenerator::freshType(const ScopePtr& scope)
 {
-    return Luau::freshType(arena, builtinTypes, scope.get());
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+    {
+        auto ft = Luau::freshType(arena, builtinTypes, scope.get());
+        interiorTypes.back().push_back(ft);
+        return ft;
+    }
+    else
+    {
+        return Luau::freshType(arena, builtinTypes, scope.get());
+    }
 }
 
 TypePackId ConstraintGenerator::freshTypePack(const ScopePtr& scope)
@@ -2408,8 +2427,17 @@ Inference ConstraintGenerator::check(const ScopePtr& scope, AstExprFunction* fun
     Checkpoint endCheckpoint = checkpoint(this);
 
     TypeId generalizedTy = arena->addType(BlockedType{});
-    NotNull<Constraint> gc =
-        addConstraint(sig.signatureScope, func->location, GeneralizationConstraint{generalizedTy, sig.signature, std::move(interiorTypes.back())});
+    NotNull<Constraint> gc = addConstraint(
+        sig.signatureScope,
+        func->location,
+        GeneralizationConstraint{
+            generalizedTy, sig.signature, FFlag::LuauTrackInteriorFreeTypesOnScope ? std::vector<TypeId>{} : std::move(interiorTypes.back())
+        }
+    );
+
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+        sig.signatureScope->interiorFreeTypes = std::move(interiorTypes.back());
+
     getMutable<BlockedType>(generalizedTy)->setOwner(gc);
     interiorTypes.pop_back();
 
@@ -2975,11 +3003,11 @@ Inference ConstraintGenerator::check(const ScopePtr& scope, AstExprTable* expr,
                 ty,
                 expr,
                 toBlock
-                );
-                // The visitor we ran prior should ensure that there are no
-                // blocked types that we would encounter while matching on
-                // this expression.
-                LUAU_ASSERT(toBlock.empty());
+            );
+            // The visitor we ran prior should ensure that there are no
+            // blocked types that we would encounter while matching on
+            // this expression.
+            LUAU_ASSERT(toBlock.empty());
         }
     }
 
@@ -3941,20 +3969,7 @@ TypeId ConstraintGenerator::createTypeFunctionInstance(
 
 TypeId ConstraintGenerator::simplifyUnion(const ScopePtr& scope, Location location, TypeId left, TypeId right)
 {
-    if (FFlag::DebugLuauEqSatSimplification)
-    {
-        TypeId ty = arena->addType(UnionType{{left, right}});
-        std::optional<EqSatSimplificationResult> res = eqSatSimplify(simplifier, ty);
-        if (!res)
-            return ty;
-
-        for (TypeId tyFun : res->newTypeFunctions)
-            addConstraint(scope, location, ReduceConstraint{tyFun});
-
-        return res->result;
-    }
-    else
-        return ::Luau::simplifyUnion(builtinTypes, arena, left, right).result;
+    return ::Luau::simplifyUnion(builtinTypes, arena, left, right).result;
 }
 
 std::vector<NotNull<Constraint>> borrowConstraints(const std::vector<ConstraintPtr>& constraints)

Analysis/src/ConstraintSolver.cpp

@@ -36,6 +36,7 @@ LUAU_FASTFLAGVARIABLE(DebugLuauEqSatSimplification)
 LUAU_FASTFLAG(LuauNewSolverPopulateTableLocations)
 LUAU_FASTFLAGVARIABLE(LuauAllowNilAssignmentToIndexer)
 LUAU_FASTFLAG(LuauUserTypeFunNoExtraConstraint)
+LUAU_FASTFLAG(LuauTrackInteriorFreeTypesOnScope)
 
 namespace Luau
 {
@@ -724,8 +725,20 @@ bool ConstraintSolver::tryDispatch(const GeneralizationConstraint& c, NotNull<co
         bind(constraint, c.generalizedType, builtinTypes->errorRecoveryType());
     }
 
-    for (TypeId ty : c.interiorTypes)
-        generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty, /* avoidSealingTables */ false);
+    if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+    {
+        // We check if this member is initialized and then access it, but
+        // clang-tidy doesn't understand this is safe.
+        if (constraint->scope->interiorFreeTypes)
+            for (TypeId ty : *constraint->scope->interiorFreeTypes) // NOLINT(bugprone-unchecked-optional-access)
+                generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty, /* avoidSealingTables */ false);
+    }
+    else
+    {
+        for (TypeId ty : c.interiorTypes)
+            generalize(NotNull{arena}, builtinTypes, constraint->scope, generalizedTypes, ty, /* avoidSealingTables */ false);
+    }
+
 
     return true;
 }
@@ -801,6 +814,11 @@ bool ConstraintSolver::tryDispatch(const IterableConstraint& c, NotNull<const Co
     {
         TypeId keyTy = freshType(arena, builtinTypes, constraint->scope);
         TypeId valueTy = freshType(arena, builtinTypes, constraint->scope);
+        if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+        {
+            trackInteriorFreeType(constraint->scope, keyTy);
+            trackInteriorFreeType(constraint->scope, valueTy);
+        }
         TypeId tableTy =
             arena->addType(TableType{TableType::Props{}, TableIndexer{keyTy, valueTy}, TypeLevel{}, constraint->scope, TableState::Free});
 
@@ -2062,6 +2080,8 @@ bool ConstraintSolver::tryDispatch(const UnpackConstraint& c, NotNull<const Cons
                 // constitute any meaningful constraint, so we replace it
                 // with a free type.
                 TypeId f = freshType(arena, builtinTypes, constraint->scope);
+                if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+                    trackInteriorFreeType(constraint->scope, f);
                 shiftReferences(resultTy, f);
                 emplaceType<BoundType>(asMutable(resultTy), f);
             }
@@ -2197,6 +2217,11 @@ bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const Iterabl
     {
         TypeId keyTy = freshType(arena, builtinTypes, constraint->scope);
         TypeId valueTy = freshType(arena, builtinTypes, constraint->scope);
+        if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+        {
+            trackInteriorFreeType(constraint->scope, keyTy);
+            trackInteriorFreeType(constraint->scope, valueTy);
+        }
         TypeId tableTy = arena->addType(TableType{TableState::Sealed, {}, constraint->scope});
         getMutable<TableType>(tableTy)->indexer = TableIndexer{keyTy, valueTy};
 
@@ -2453,6 +2478,8 @@ TablePropLookupResult ConstraintSolver::lookupTableProp(
         if (ttv->state == TableState::Free)
         {
             TypeId result = freshType(arena, builtinTypes, ttv->scope);
+            if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+                trackInteriorFreeType(ttv->scope, result);
             switch (context)
             {
             case ValueContext::RValue:
@@ -2562,6 +2589,9 @@ TablePropLookupResult ConstraintSolver::lookupTableProp(
         LUAU_ASSERT(tt);
         TypeId propType = freshType(arena, builtinTypes, scope);
 
+        if (FFlag::LuauTrackInteriorFreeTypesOnScope)
+            trackInteriorFreeType(scope, propType);
+
         switch (context)
         {
         case ValueContext::RValue: