Sync to upstream/release/527 (#481)

Analysis/include/Luau/TypeVar.h

@@ -329,7 +329,7 @@ struct TableTypeVar
     // We need to know which is which when we stringify types.
     std::optional<std::string> syntheticName;
 
-    std::map<Name, Location> methodDefinitionLocations;
+    std::map<Name, Location> methodDefinitionLocations; // TODO: Remove with FFlag::LuauNoMethodLocations
     std::vector<TypeId> instantiatedTypeParams;
     std::vector<TypePackId> instantiatedTypePackParams;
     ModuleName definitionModuleName;

Analysis/src/Clone.cpp

@@ -11,6 +11,7 @@ LUAU_FASTFLAG(DebugLuauCopyBeforeNormalizing)
 LUAU_FASTINTVARIABLE(LuauTypeCloneRecursionLimit, 300)
 LUAU_FASTFLAG(LuauTypecheckOptPass)
 LUAU_FASTFLAGVARIABLE(LuauLosslessClone, false)
+LUAU_FASTFLAG(LuauNoMethodLocations)
 
 namespace Luau
 {
@@ -277,6 +278,7 @@ void TypeCloner::operator()(const TableTypeVar& t)
     }
 
     ttv->definitionModuleName = t.definitionModuleName;
+    if (!FFlag::LuauNoMethodLocations)
         ttv->methodDefinitionLocations = t.methodDefinitionLocations;
     ttv->tags = t.tags;
 }

Analysis/src/Normalize.cpp

@@ -14,7 +14,6 @@ LUAU_FASTFLAGVARIABLE(DebugLuauCopyBeforeNormalizing, false)
 // This could theoretically be 2000 on amd64, but x86 requires this.
 LUAU_FASTINTVARIABLE(LuauNormalizeIterationLimit, 1200);
 LUAU_FASTFLAGVARIABLE(LuauNormalizeCombineTableFix, false);
-LUAU_FASTFLAGVARIABLE(LuauNormalizeCombineIntersectionFix, false);
 
 namespace Luau
 {
@@ -863,7 +862,7 @@ struct Normalize final : TypeVarVisitor
 
             TypeId theTable = result->parts.back();
 
-            if (!get<TableTypeVar>(FFlag::LuauNormalizeCombineIntersectionFix ? follow(theTable) : theTable))
+            if (!get<TableTypeVar>(follow(theTable)))
             {
                 result->parts.push_back(arena.addType(TableTypeVar{TableState::Sealed, TypeLevel{}}));
                 theTable = result->parts.back();

Analysis/src/Substitution.cpp

@@ -12,6 +12,7 @@ LUAU_FASTINTVARIABLE(LuauTarjanChildLimit, 10000)
 LUAU_FASTFLAG(LuauTypecheckOptPass)
 LUAU_FASTFLAGVARIABLE(LuauSubstituteFollowNewTypes, false)
 LUAU_FASTFLAGVARIABLE(LuauSubstituteFollowPossibleMutations, false)
+LUAU_FASTFLAG(LuauNoMethodLocations)
 
 namespace Luau
 {
@@ -408,6 +409,7 @@ TypeId Substitution::clone(TypeId ty)
     {
         LUAU_ASSERT(!ttv->boundTo);
         TableTypeVar clone = TableTypeVar{ttv->props, ttv->indexer, ttv->level, ttv->state};
+        if (!FFlag::LuauNoMethodLocations)
             clone.methodDefinitionLocations = ttv->methodDefinitionLocations;
         clone.definitionModuleName = ttv->definitionModuleName;
         clone.name = ttv->name;

Analysis/src/ToString.cpp

@@ -248,6 +248,13 @@ struct StringifierState
         result.name += s;
     }
 
+    void emit(TypeLevel level)
+    {
+        emit(std::to_string(level.level));
+        emit("-");
+        emit(std::to_string(level.subLevel));
+    }
+
     void emit(const char* s)
     {
         if (opts.maxTypeLength > 0 && result.name.length() > opts.maxTypeLength)
@@ -379,7 +386,7 @@ struct TypeVarStringifier
         if (FFlag::DebugLuauVerboseTypeNames)
         {
             state.emit("-");
-            state.emit(std::to_string(ftv.level.level));
+            state.emit(ftv.level);
         }
     }
 
@@ -403,7 +410,10 @@ struct TypeVarStringifier
     {
         state.result.invalid = true;
 
-        state.emit("[[");
+        state.emit("[");
+        if (FFlag::DebugLuauVerboseTypeNames)
+            state.emit(ctv.level);
+        state.emit("[");
 
         bool first = true;
         for (TypeId ty : ctv.parts)
@@ -947,7 +957,7 @@ struct TypePackStringifier
         if (FFlag::DebugLuauVerboseTypeNames)
         {
             state.emit("-");
-            state.emit(std::to_string(pack.level.level));
+            state.emit(pack.level);
         }
 
         state.emit("...");

Analysis/src/TypeInfer.cpp

@@ -36,13 +36,11 @@ LUAU_FASTFLAGVARIABLE(LuauEqConstraint, false)
 LUAU_FASTFLAGVARIABLE(LuauWeakEqConstraint, false) // Eventually removed as false.
 LUAU_FASTFLAGVARIABLE(LuauLowerBoundsCalculation, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification, false)
-LUAU_FASTFLAGVARIABLE(LuauInferStatFunction, false)
 LUAU_FASTFLAGVARIABLE(LuauInstantiateFollows, false)
 LUAU_FASTFLAGVARIABLE(LuauSelfCallAutocompleteFix, false)
 LUAU_FASTFLAGVARIABLE(LuauDiscriminableUnions2, false)
 LUAU_FASTFLAGVARIABLE(LuauReduceUnionRecursion, false)
 LUAU_FASTFLAGVARIABLE(LuauOnlyMutateInstantiatedTables, false)
-LUAU_FASTFLAGVARIABLE(LuauStatFunctionSimplify4, false)
 LUAU_FASTFLAGVARIABLE(LuauTypecheckOptPass, false)
 LUAU_FASTFLAGVARIABLE(LuauUnsealedTableLiteral, false)
 LUAU_FASTFLAGVARIABLE(LuauTwoPassAliasDefinitionFix, false)
@@ -53,12 +51,13 @@ LUAU_FASTFLAGVARIABLE(LuauDoNotTryToReduce, false)
 LUAU_FASTFLAGVARIABLE(LuauDoNotAccidentallyDependOnPointerOrdering, false)
 LUAU_FASTFLAGVARIABLE(LuauCheckImplicitNumbericKeys, false)
 LUAU_FASTFLAG(LuauAnyInIsOptionalIsOptional)
-LUAU_FASTFLAGVARIABLE(LuauDecoupleOperatorInferenceFromUnifiedTypeInference, false)
 LUAU_FASTFLAGVARIABLE(LuauTableUseCounterInstead, false)
 LUAU_FASTFLAGVARIABLE(LuauReturnTypeInferenceInNonstrict, false)
 LUAU_FASTFLAGVARIABLE(LuauRecursionLimitException, false);
 LUAU_FASTFLAG(LuauLosslessClone)
 LUAU_FASTFLAGVARIABLE(LuauTypecheckIter, false);
+LUAU_FASTFLAGVARIABLE(LuauSuccessTypingForEqualityOperations, false)
+LUAU_FASTFLAGVARIABLE(LuauNoMethodLocations, false);
 
 namespace Luau
 {
@@ -587,7 +586,7 @@ void TypeChecker::checkBlockWithoutRecursionCheck(const ScopePtr& scope, const A
         {
             std::optional<TypeId> expectedType;
 
-            if (FFlag::LuauInferStatFunction && !fun->func->self)
+            if (!fun->func->self)
             {
                 if (auto name = fun->name->as<AstExprIndexName>())
                 {
@@ -1307,7 +1306,7 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
         scope->bindings[name->local] = {anyIfNonstrict(quantify(funScope, ty, name->local->location)), name->local->location};
         return;
     }
-    else if (auto name = function.name->as<AstExprIndexName>(); name && FFlag::LuauStatFunctionSimplify4)
+    else if (auto name = function.name->as<AstExprIndexName>())
     {
         TypeId exprTy = checkExpr(scope, *name->expr).type;
         TableTypeVar* ttv = getMutableTableType(exprTy);
@@ -1341,7 +1340,7 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
         if (ttv && ttv->state != TableState::Sealed)
             ttv->props[name->index.value] = {follow(quantify(funScope, ty, name->indexLocation)), /* deprecated */ false, {}, name->indexLocation};
     }
-    else if (FFlag::LuauStatFunctionSimplify4)
+    else
     {
         LUAU_ASSERT(function.name->is<AstExprError>());
 
@@ -1349,71 +1348,6 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
 
         checkFunctionBody(funScope, ty, *function.func);
     }
-    else if (function.func->self)
-    {
-        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify4);
-
-        AstExprIndexName* indexName = function.name->as<AstExprIndexName>();
-        if (!indexName)
-            ice("member function declaration has malformed name expression");
-
-        TypeId selfTy = checkExpr(scope, *indexName->expr).type;
-        TableTypeVar* tableSelf = getMutableTableType(selfTy);
-        if (!tableSelf)
-        {
-            if (isTableIntersection(selfTy))
-                reportError(TypeError{function.location, CannotExtendTable{selfTy, CannotExtendTable::Property, indexName->index.value}});
-            else if (!get<ErrorTypeVar>(selfTy) && !get<AnyTypeVar>(selfTy))
-                reportError(TypeError{function.location, OnlyTablesCanHaveMethods{selfTy}});
-        }
-        else if (tableSelf->state == TableState::Sealed)
-            reportError(TypeError{function.location, CannotExtendTable{selfTy, CannotExtendTable::Property, indexName->index.value}});
-
-        const bool tableIsExtendable = tableSelf && tableSelf->state != TableState::Sealed;
-
-        ty = follow(ty);
-
-        if (tableIsExtendable)
-            tableSelf->props[indexName->index.value] = {ty, /* deprecated */ false, {}, indexName->indexLocation};
-
-        const FunctionTypeVar* funTy = get<FunctionTypeVar>(ty);
-        if (!funTy)
-            ice("Methods should be functions");
-
-        std::optional<TypeId> arg0 = first(funTy->argTypes);
-        if (!arg0)
-            ice("Methods should always have at least 1 argument (self)");
-
-        checkFunctionBody(funScope, ty, *function.func);
-
-        if (tableIsExtendable)
-            tableSelf->props[indexName->index.value] = {
-                follow(quantify(funScope, ty, indexName->indexLocation)), /* deprecated */ false, {}, indexName->indexLocation};
-    }
-    else
-    {
-        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify4);
-
-        TypeId leftType = checkLValueBinding(scope, *function.name);
-
-        checkFunctionBody(funScope, ty, *function.func);
-
-        unify(ty, leftType, function.location);
-
-        LUAU_ASSERT(function.name->is<AstExprIndexName>() || function.name->is<AstExprError>());
-
-        if (auto exprIndexName = function.name->as<AstExprIndexName>())
-        {
-            if (auto typeIt = currentModule->astTypes.find(exprIndexName->expr))
-            {
-                if (auto ttv = getMutableTableType(*typeIt))
-                {
-                    if (auto it = ttv->props.find(exprIndexName->index.value); it != ttv->props.end())
-                        it->second.type = follow(quantify(funScope, leftType, function.name->location));
-                }
-            }
-        }
-    }
 }
 
 void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funScope, const AstStatLocalFunction& function)
@@ -1523,6 +1457,7 @@ void TypeChecker::check(const ScopePtr& scope, const AstStatTypeAlias& typealias
                     // This is a shallow clone, original recursive links to self are not updated
                     TableTypeVar clone = TableTypeVar{ttv->props, ttv->indexer, ttv->level, ttv->state};
 
+                    if (!FFlag::LuauNoMethodLocations)
                         clone.methodDefinitionLocations = ttv->methodDefinitionLocations;
                     clone.definitionModuleName = ttv->definitionModuleName;
                     clone.name = name;
@@ -2652,14 +2587,59 @@ TypeId TypeChecker::checkRelationalOperation(
         std::optional<TypeId> leftMetatable = isString(lhsType) ? std::nullopt : getMetatable(follow(lhsType));
         std::optional<TypeId> rightMetatable = isString(rhsType) ? std::nullopt : getMetatable(follow(rhsType));
 
-        // TODO: this check seems odd, the second part is redundant
+        if (FFlag::LuauSuccessTypingForEqualityOperations)
-        // is it meant to be if (leftMetatable && rightMetatable && leftMetatable != rightMetatable)
+        {
+            if (leftMetatable != rightMetatable)
+            {
+                bool matches = false;
+                if (isEquality)
+                {
+                    if (const UnionTypeVar* utv = get<UnionTypeVar>(leftType); utv && rightMetatable)
+                    {
+                        for (TypeId leftOption : utv)
+                        {
+                            if (getMetatable(follow(leftOption)) == rightMetatable)
+                            {
+                                matches = true;
+                                break;
+                            }
+                        }
+                    }
+
+                    if (!matches)
+                    {
+                        if (const UnionTypeVar* utv = get<UnionTypeVar>(rhsType); utv && leftMetatable)
+                        {
+                            for (TypeId rightOption : utv)
+                            {
+                                if (getMetatable(follow(rightOption)) == leftMetatable)
+                                {
+                                    matches = true;
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                }
+
+
+                if (!matches)
+                {
+                    reportError(expr.location, GenericError{format("Types %s and %s cannot be compared with %s because they do not have the same metatable",
+                                            toString(lhsType).c_str(), toString(rhsType).c_str(), toString(expr.op).c_str())});
+                    return errorRecoveryType(booleanType);
+                }
+            }
+        }
+        else
+        {
             if (bool(leftMetatable) != bool(rightMetatable) && leftMetatable != rightMetatable)
             {
                 reportError(expr.location, GenericError{format("Types %s and %s cannot be compared with %s because they do not have the same metatable",
                                             toString(lhsType).c_str(), toString(rhsType).c_str(), toString(expr.op).c_str())});
                 return errorRecoveryType(booleanType);
             }
+        }
 
         if (leftMetatable)
         {
@@ -2754,23 +2734,12 @@ TypeId TypeChecker::checkBinaryOperation(
     lhsType = follow(lhsType);
     rhsType = follow(rhsType);
 
-    if (FFlag::LuauDecoupleOperatorInferenceFromUnifiedTypeInference)
-    {
     if (!isNonstrictMode() && get<FreeTypeVar>(lhsType))
     {
         auto name = getIdentifierOfBaseVar(expr.left);
         reportError(expr.location, CannotInferBinaryOperation{expr.op, name, CannotInferBinaryOperation::Operation});
         // We will fall-through to the `return anyType` check below.
     }
-    }
-    else
-    {
-        if (!isNonstrictMode() && get<FreeTypeVar>(lhsType))
-        {
-            auto name = getIdentifierOfBaseVar(expr.left);
-            reportError(expr.location, CannotInferBinaryOperation{expr.op, name, CannotInferBinaryOperation::Operation});
-        }
-    }
 
     // If we know nothing at all about the lhs type, we can usually say nothing about the result.
     // The notable exception to this is the equality and inequality operators, which always produce a boolean.
@@ -3231,14 +3200,8 @@ TypeId TypeChecker::checkFunctionName(const ScopePtr& scope, AstExpr& funName, T
     else if (auto indexName = funName.as<AstExprIndexName>())
     {
         TypeId lhsType = checkExpr(scope, *indexName->expr).type;
-
-        if (!FFlag::LuauStatFunctionSimplify4 && (get<ErrorTypeVar>(lhsType) || get<AnyTypeVar>(lhsType)))
-            return lhsType;
-
         TableTypeVar* ttv = getMutableTableType(lhsType);
 
-        if (FFlag::LuauStatFunctionSimplify4)
-        {
         if (!ttv || ttv->state == TableState::Sealed)
         {
             if (auto ty = getIndexTypeFromType(scope, lhsType, indexName->index.value, indexName->indexLocation, false))
@@ -3246,27 +3209,17 @@ TypeId TypeChecker::checkFunctionName(const ScopePtr& scope, AstExpr& funName, T
 
             return errorRecoveryType(scope);
         }
-        }
-        else
-        {
-            if (!ttv || lhsType->persistent || ttv->state == TableState::Sealed)
-                return errorRecoveryType(scope);
-        }
 
         Name name = indexName->index.value;
 
         if (ttv->props.count(name))
-        {
-            if (FFlag::LuauStatFunctionSimplify4)
             return ttv->props[name].type;
-            else
-                return errorRecoveryType(scope);
-        }
 
         Property& property = ttv->props[name];
 
         property.type = freshTy();
         property.location = indexName->indexLocation;
+        if (!FFlag::LuauNoMethodLocations)
             ttv->methodDefinitionLocations[name] = funName.location;
         return property.type;
     }
@@ -4669,6 +4622,7 @@ TypeId ReplaceGenerics::clean(TypeId ty)
     if (const TableTypeVar* ttv = log->getMutable<TableTypeVar>(ty))
     {
         TableTypeVar clone = TableTypeVar{ttv->props, ttv->indexer, level, TableState::Free};
+        if (!FFlag::LuauNoMethodLocations)
             clone.methodDefinitionLocations = ttv->methodDefinitionLocations;
         clone.definitionModuleName = ttv->definitionModuleName;
         return addType(std::move(clone));
@@ -4715,6 +4669,7 @@ TypeId Anyification::clean(TypeId ty)
     if (const TableTypeVar* ttv = log->getMutable<TableTypeVar>(ty))
     {
         TableTypeVar clone = TableTypeVar{ttv->props, ttv->indexer, ttv->level, TableState::Sealed};
+        if (!FFlag::LuauNoMethodLocations)
             clone.methodDefinitionLocations = ttv->methodDefinitionLocations;
         clone.definitionModuleName = ttv->definitionModuleName;
         clone.name = ttv->name;

Ast/src/Parser.cpp

@@ -10,7 +10,6 @@
 // See docs/SyntaxChanges.md for an explanation.
 LUAU_FASTINTVARIABLE(LuauRecursionLimit, 1000)
 LUAU_FASTINTVARIABLE(LuauParseErrorLimit, 100)
-LUAU_FASTFLAGVARIABLE(LuauParseLocationIgnoreCommentSkipInCapture, false)
 
 namespace Luau
 {
@@ -2821,7 +2820,7 @@ void Parser::nextLexeme()
                 hotcomments.push_back({hotcommentHeader, lexeme.location, std::string(text + 1, text + end)});
             }
 
-            type = lexer.next(/* skipComments= */ false, !FFlag::LuauParseLocationIgnoreCommentSkipInCapture).type;
+            type = lexer.next(/* skipComments= */ false, /* updatePrevLocation= */ false).type;
         }
     }
     else

CMakeLists.txt

@@ -110,6 +110,12 @@ if (MSVC AND MSVC_VERSION GREATER_EQUAL 1924)
     set_source_files_properties(VM/src/lvmexecute.cpp PROPERTIES COMPILE_FLAGS /d2ssa-pre-)
 endif()
 
+if(MSVC AND LUAU_BUILD_CLI)
+    # the default stack size that MSVC linker uses is 1 MB; we need more stack space in Debug because stack frames are larger
+    set_target_properties(Luau.Analyze.CLI PROPERTIES LINK_FLAGS_DEBUG /STACK:2097152)
+    set_target_properties(Luau.Repl.CLI PROPERTIES LINK_FLAGS_DEBUG /STACK:2097152)
+endif()
+
 # embed .natvis inside the library debug information
 if(MSVC)
     target_link_options(Luau.Ast INTERFACE /NATVIS:${CMAKE_CURRENT_SOURCE_DIR}/tools/natvis/Ast.natvis)

Compiler/src/Compiler.cpp

@@ -628,8 +628,13 @@ struct Compiler
                 return;
 
             if (fi && !fi->canInline)
+            {
+                if (func->vararg)
+                    bytecode.addDebugRemark("inlining failed: function is variadic");
+                else
                     bytecode.addDebugRemark("inlining failed: complex constructs in function body");
             }
+        }
 
         RegScope rs(this);
 
@@ -2342,17 +2347,28 @@ struct Compiler
         RegScope rs(this);
 
         uint8_t temp = 0;
+        bool consecutive = false;
         bool multRet = false;
 
-        // Optimization: return local value directly instead of copying it into a temporary
+        // Optimization: return locals directly instead of copying them into a temporary
-        if (stat->list.size == 1 && isExprLocalReg(stat->list.data[0]))
+        // this is very important for a single return value and occasionally effective for multiple values
+        if (stat->list.size > 0 && isExprLocalReg(stat->list.data[0]))
         {
-            AstExprLocal* le = stat->list.data[0]->as<AstExprLocal>();
+            temp = getLocal(stat->list.data[0]->as<AstExprLocal>()->local);
-            LUAU_ASSERT(le);
+            consecutive = true;
 
-            temp = getLocal(le->local);
+            for (size_t i = 1; i < stat->list.size; ++i)
+            {
+                AstExpr* v = stat->list.data[i];
+                if (!isExprLocalReg(v) || getLocal(v->as<AstExprLocal>()->local) != temp + i)
+                {
+                    consecutive = false;
+                    break;
                 }
-        else if (stat->list.size > 0)
+            }
+        }
+
+        if (!consecutive && stat->list.size > 0)
         {
             temp = allocReg(stat, unsigned(stat->list.size));
 

Compiler/src/ConstantFolding.cpp

@@ -195,12 +195,16 @@ struct ConstantVisitor : AstVisitor
     DenseHashMap<AstLocal*, Variable>& variables;
     DenseHashMap<AstLocal*, Constant>& locals;
 
+    bool wasEmpty = false;
+
     ConstantVisitor(
         DenseHashMap<AstExpr*, Constant>& constants, DenseHashMap<AstLocal*, Variable>& variables, DenseHashMap<AstLocal*, Constant>& locals)
         : constants(constants)
         , variables(variables)
         , locals(locals)
     {
+        // since we do a single pass over the tree, if the initial state was empty we don't need to clear out old entries
+        wasEmpty = constants.empty() && locals.empty();
     }
 
     Constant analyze(AstExpr* node)
@@ -326,7 +330,7 @@ struct ConstantVisitor : AstVisitor
     {
         if (value.type != Constant::Type_Unknown)
             map[key] = value;
-        else if (!FFlag::LuauCompileSupportInlining)
+        else if (!FFlag::LuauCompileSupportInlining || wasEmpty)
             ;
         else if (Constant* old = map.find(key))
             old->type = Constant::Type_Unknown;

Compiler/src/CostModel.cpp

@@ -187,7 +187,7 @@ struct CostVisitor : AstVisitor
         if (node->is<AstStatIf>())
             result += 2;
         else if (node->is<AstStatWhile>() || node->is<AstStatRepeat>() || node->is<AstStatFor>() || node->is<AstStatForIn>())
-            result += 2;
+            result += 5;
         else if (node->is<AstStatBreak>() || node->is<AstStatContinue>())
             result += 1;
 

extern/isocline/src/bbcode.c

@@ -575,6 +575,7 @@ ic_private const char* parse_tag_value( tag_t* tag, char* idbuf, const char* s,
   }  
   // limit name and attr to 128 bytes
   char valbuf[128];
+  valbuf[0] = 0; // fixes gcc uninitialized warning
   ic_strncpy( idbuf, 128, id, idend - id);
   ic_strncpy( valbuf, 128, val, valend - val);
   ic_str_tolower(idbuf);

tests/AstQuery.test.cpp

@@ -7,7 +7,7 @@
 
 using namespace Luau;
 
-struct DocumentationSymbolFixture : Fixture
+struct DocumentationSymbolFixture : BuiltinsFixture
 {
     std::optional<DocumentationSymbol> getDocSymbol(const std::string& source, Position position)
     {

tests/Autocomplete.test.cpp

@@ -27,7 +27,7 @@ template<class BaseType>
 struct ACFixtureImpl : BaseType
 {
     ACFixtureImpl()
-        : Fixture(true, true)
+        : BaseType(true, true)
     {
     }
 
@@ -111,6 +111,18 @@ struct ACFixtureImpl : BaseType
 };
 
 struct ACFixture : ACFixtureImpl<Fixture>
+{
+    ACFixture()
+        : ACFixtureImpl<Fixture>()
+    {
+        addGlobalBinding(frontend.typeChecker, "table", Binding{typeChecker.anyType});
+        addGlobalBinding(frontend.typeChecker, "math", Binding{typeChecker.anyType});
+        addGlobalBinding(frontend.typeCheckerForAutocomplete, "table", Binding{typeChecker.anyType});
+        addGlobalBinding(frontend.typeCheckerForAutocomplete, "math", Binding{typeChecker.anyType});
+    }
+};
+
+struct ACBuiltinsFixture : ACFixtureImpl<BuiltinsFixture>
 {
 };
 
@@ -277,7 +289,7 @@ TEST_CASE_FIXTURE(ACFixture, "function_parameters")
     CHECK(ac.entryMap.count("test"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "get_member_completions")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "get_member_completions")
 {
     check(R"(
         local a = table.@1
@@ -376,7 +388,7 @@ TEST_CASE_FIXTURE(ACFixture, "table_intersection")
     CHECK(ac.entryMap.count("c3"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "get_string_completions")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "get_string_completions")
 {
     check(R"(
         local a = ("foo"):@1
@@ -427,7 +439,7 @@ TEST_CASE_FIXTURE(ACFixture, "method_call_inside_function_body")
     CHECK(!ac.entryMap.count("math"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "method_call_inside_if_conditional")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "method_call_inside_if_conditional")
 {
     check(R"(
         if table:  @1
@@ -1884,7 +1896,7 @@ ex.b(function(x:
     CHECK(!ac.entryMap.count("(done) -> number"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "suggest_external_module_type")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "suggest_external_module_type")
 {
     fileResolver.source["Module/A"] = R"(
 export type done = { x: number, y: number }
@@ -2235,7 +2247,7 @@ local a: aaa.do
     CHECK(ac.entryMap.count("other"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "autocompleteSource")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "autocompleteSource")
 {
     std::string_view source = R"(
         local a = table. -- Line 1
@@ -2269,7 +2281,7 @@ TEST_CASE_FIXTURE(ACFixture, "autocompleteSource_comments")
     CHECK_EQ(0, ac.entryMap.size());
 }
 
-TEST_CASE_FIXTURE(ACFixture, "autocompleteProp_index_function_metamethod_is_variadic")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "autocompleteProp_index_function_metamethod_is_variadic")
 {
     std::string_view source = R"(
         type Foo = {x: number}
@@ -2720,7 +2732,7 @@ type A<T... = ...@1> = () -> T
     CHECK(ac.entryMap.count("string"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "autocomplete_oop_implicit_self")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "autocomplete_oop_implicit_self")
 {
     check(R"(
 --!strict
@@ -2745,7 +2757,7 @@ end
     CHECK(ac.entryMap.count("getx"));
 }
 
-TEST_CASE_FIXTURE(ACFixture, "autocomplete_on_string_singletons")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "autocomplete_on_string_singletons")
 {
     check(R"(
         --!strict
@@ -2989,7 +3001,7 @@ s.@1
     CHECK(ac.entryMap["sub"].wrongIndexType == true);
 }
 
-TEST_CASE_FIXTURE(ACFixture, "string_library_non_self_calls_are_fine")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "string_library_non_self_calls_are_fine")
 {
     ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
 
@@ -3007,7 +3019,7 @@ string.@1
     CHECK(ac.entryMap["sub"].wrongIndexType == false);
 }
 
-TEST_CASE_FIXTURE(ACFixture, "string_library_self_calls_are_invalid")
+TEST_CASE_FIXTURE(ACBuiltinsFixture, "string_library_self_calls_are_invalid")
 {
     ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
 

tests/BuiltinDefinitions.test.cpp

@@ -10,8 +10,10 @@ using namespace Luau;
 
 TEST_SUITE_BEGIN("BuiltinDefinitionsTest");
 
-TEST_CASE_FIXTURE(Fixture, "lib_documentation_symbols")
+TEST_CASE_FIXTURE(BuiltinsFixture, "lib_documentation_symbols")
 {
+    CHECK(!typeChecker.globalScope->bindings.empty());
+
     for (const auto& [name, binding] : typeChecker.globalScope->bindings)
     {
         std::string nameString(name.c_str());

tests/Compiler.test.cpp

@@ -4713,7 +4713,6 @@ local function foo()
 end
 
 local a, b = foo()
-
 return a, b
 )",
                         1, 2),
@@ -4721,9 +4720,7 @@ return a, b
 DUPCLOSURE R0 K0
 LOADNIL R1
 LOADNIL R2
-MOVE R3 R1
+RETURN R1 2
-MOVE R4 R2
-RETURN R3 2
 )");
 
     // this happens even if the function returns conditionally
@@ -4733,7 +4730,6 @@ local function foo(a)
 end
 
 local a, b = foo(false)
-
 return a, b
 )",
                         1, 2),
@@ -4741,9 +4737,7 @@ return a, b
 DUPCLOSURE R0 K0
 LOADNIL R1
 LOADNIL R2
-MOVE R3 R1
+RETURN R1 2
-MOVE R4 R2
-RETURN R3 2
 )");
 
     // note though that we can't inline a function like this in multret context
@@ -4880,11 +4874,7 @@ LOADN R5 1
 ADD R4 R5 R1
 LOADN R5 3
 ADD R6 R1 R2
-MOVE R7 R3
+RETURN R3 4
-MOVE R8 R4
-MOVE R9 R5
-MOVE R10 R6
-RETURN R7 4
 )");
 }
 
@@ -5151,4 +5141,59 @@ RETURN R0 0
 )");
 }
 
+TEST_CASE("ReturnConsecutive")
+{
+    // we can return a single local directly
+    CHECK_EQ("\n" + compileFunction0(R"(
+local x = ...
+return x
+)"),
+        R"(
+GETVARARGS R0 1
+RETURN R0 1
+)");
+
+    // or multiple, when they are allocated in consecutive registers
+    CHECK_EQ("\n" + compileFunction0(R"(
+local x, y = ...
+return x, y
+)"),
+        R"(
+GETVARARGS R0 2
+RETURN R0 2
+)");
+
+    // but not if it's an expression
+    CHECK_EQ("\n" + compileFunction0(R"(
+local x, y = ...
+return x, y + 1
+)"),
+        R"(
+GETVARARGS R0 2
+MOVE R2 R0
+ADDK R3 R1 K0
+RETURN R2 2
+)");
+
+    // or a local with wrong register number
+    CHECK_EQ("\n" + compileFunction0(R"(
+local x, y = ...
+return y, x
+)"),
+        R"(
+GETVARARGS R0 2
+MOVE R2 R1
+MOVE R3 R0
+RETURN R2 2
+)");
+
+    // also double check the optimization doesn't trip on no-argument return (these are rare)
+    CHECK_EQ("\n" + compileFunction0(R"(
+return
+)"),
+        R"(
+RETURN R0 0
+)");
+}
+
 TEST_SUITE_END();

tests/CostModel.test.cpp

@@ -76,9 +76,9 @@ end
     const bool args1[] = {false};
     const bool args2[] = {true};
 
-    // loop baseline cost is 2
+    // loop baseline cost is 5
-    CHECK_EQ(3, Luau::Compile::computeCost(model, args1, 1));
+    CHECK_EQ(6, Luau::Compile::computeCost(model, args1, 1));
-    CHECK_EQ(3, Luau::Compile::computeCost(model, args2, 1));
+    CHECK_EQ(6, Luau::Compile::computeCost(model, args2, 1));
 }
 
 TEST_CASE("MutableVariable")
@@ -154,8 +154,8 @@ end
     const bool args1[] = {false};
     const bool args2[] = {true};
 
-    CHECK_EQ(38, Luau::Compile::computeCost(model, args1, 1));
+    CHECK_EQ(50, Luau::Compile::computeCost(model, args1, 1));
-    CHECK_EQ(37, Luau::Compile::computeCost(model, args2, 1));
+    CHECK_EQ(49, Luau::Compile::computeCost(model, args2, 1));
 }
 
 TEST_CASE("Conditional")
@@ -219,8 +219,8 @@ end
     const bool args1[] = {false};
     const bool args2[] = {true};
 
-    CHECK_EQ(4, Luau::Compile::computeCost(model, args1, 1));
+    CHECK_EQ(7, Luau::Compile::computeCost(model, args1, 1));
-    CHECK_EQ(3, Luau::Compile::computeCost(model, args2, 1));
+    CHECK_EQ(6, Luau::Compile::computeCost(model, args2, 1));
 }
 
 TEST_SUITE_END();

tests/Fixture.cpp

@@ -92,10 +92,6 @@ Fixture::Fixture(bool freeze, bool prepareAutocomplete)
     configResolver.defaultConfig.enabledLint.warningMask = ~0ull;
     configResolver.defaultConfig.parseOptions.captureComments = true;
 
-    registerBuiltinTypes(frontend.typeChecker);
-    if (prepareAutocomplete)
-        registerBuiltinTypes(frontend.typeCheckerForAutocomplete);
-    registerTestTypes();
     Luau::freeze(frontend.typeChecker.globalTypes);
     Luau::freeze(frontend.typeCheckerForAutocomplete.globalTypes);
 
@@ -410,6 +406,21 @@ LoadDefinitionFileResult Fixture::loadDefinition(const std::string& source)
     return result;
 }
 
+BuiltinsFixture::BuiltinsFixture(bool freeze, bool prepareAutocomplete)
+    : Fixture(freeze, prepareAutocomplete)
+{
+    Luau::unfreeze(frontend.typeChecker.globalTypes);
+    Luau::unfreeze(frontend.typeCheckerForAutocomplete.globalTypes);
+
+    registerBuiltinTypes(frontend.typeChecker);
+    if (prepareAutocomplete)
+        registerBuiltinTypes(frontend.typeCheckerForAutocomplete);
+    registerTestTypes();
+
+    Luau::freeze(frontend.typeChecker.globalTypes);
+    Luau::freeze(frontend.typeCheckerForAutocomplete.globalTypes);
+}
+
 ModuleName fromString(std::string_view name)
 {
     return ModuleName(name);

tests/Fixture.h

@@ -151,6 +151,11 @@ struct Fixture
     LoadDefinitionFileResult loadDefinition(const std::string& source);
 };
 
+struct BuiltinsFixture : Fixture
+{
+    BuiltinsFixture(bool freeze = true, bool prepareAutocomplete = false);
+};
+
 ModuleName fromString(std::string_view name);
 
 template<typename T>

tests/Frontend.test.cpp

@@ -77,7 +77,7 @@ struct NaiveFileResolver : NullFileResolver
 
 } // namespace
 
-struct FrontendFixture : Fixture
+struct FrontendFixture : BuiltinsFixture
 {
     FrontendFixture()
     {

tests/Linter.test.cpp

@@ -75,7 +75,7 @@ _ = 6
     CHECK_EQ(result.warnings.size(), 0);
 }
 
-TEST_CASE_FIXTURE(Fixture, "BuiltinGlobalWrite")
+TEST_CASE_FIXTURE(BuiltinsFixture, "BuiltinGlobalWrite")
 {
     LintResult result = lint(R"(
 math = {}
@@ -309,7 +309,7 @@ print(arg)
     CHECK_EQ(result.warnings[0].text, "Variable 'arg' shadows previous declaration at line 2");
 }
 
-TEST_CASE_FIXTURE(Fixture, "LocalShadowGlobal")
+TEST_CASE_FIXTURE(BuiltinsFixture, "LocalShadowGlobal")
 {
     LintResult result = lint(R"(
 local math = math
@@ -1470,7 +1470,7 @@ end
     CHECK_EQ(result.warnings[2].text, "Member 'Instance.DataCost' is deprecated");
 }
 
-TEST_CASE_FIXTURE(Fixture, "TableOperations")
+TEST_CASE_FIXTURE(BuiltinsFixture, "TableOperations")
 {
     LintResult result = lintTyped(R"(
 local t = {}

tests/Module.test.cpp

@@ -113,7 +113,7 @@ TEST_CASE_FIXTURE(Fixture, "deepClone_cyclic_table")
     CHECK_EQ(2, dest.typeVars.size());      // One table and one function
 }
 
-TEST_CASE_FIXTURE(Fixture, "builtin_types_point_into_globalTypes_arena")
+TEST_CASE_FIXTURE(BuiltinsFixture, "builtin_types_point_into_globalTypes_arena")
 {
     CheckResult result = check(R"(
         return {sign=math.sign}
@@ -250,7 +250,7 @@ TEST_CASE_FIXTURE(Fixture, "clone_constrained_intersection")
     CHECK_EQ(getSingletonTypes().stringType, ctv->parts[1]);
 }
 
-TEST_CASE_FIXTURE(Fixture, "clone_self_property")
+TEST_CASE_FIXTURE(BuiltinsFixture, "clone_self_property")
 {
     ScopedFastFlag sff{"LuauAnyInIsOptionalIsOptional", true};
 

tests/NonstrictMode.test.cpp

@@ -13,7 +13,7 @@ using namespace Luau;
 
 TEST_SUITE_BEGIN("NonstrictModeTests");
 
-TEST_CASE_FIXTURE(Fixture, "function_returns_number_or_string")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_returns_number_or_string")
 {
     ScopedFastFlag sff[]{
         {"LuauReturnTypeInferenceInNonstrict", true},
@@ -224,7 +224,7 @@ TEST_CASE_FIXTURE(Fixture, "inline_table_props_are_also_any")
     CHECK_MESSAGE(get<FunctionTypeVar>(ttv->props["three"].type), "Should be a function: " << *ttv->props["three"].type);
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_iterator_variables_are_any")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_iterator_variables_are_any")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -243,7 +243,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_iterator_variables_are_any")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_dot_insert_and_recursive_calls")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_dot_insert_and_recursive_calls")
 {
     CheckResult result = check(R"(
         --!nonstrict

tests/Normalize.test.cpp

@@ -739,7 +739,7 @@ TEST_CASE_FIXTURE(Fixture, "cyclic_table_normalizes_sensibly")
     CHECK_EQ("t1 where t1 = { get: () -> t1 }", toString(ty, {true}));
 }
 
-TEST_CASE_FIXTURE(Fixture, "union_of_distinct_free_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "union_of_distinct_free_types")
 {
     ScopedFastFlag flags[] = {
         {"LuauLowerBoundsCalculation", true},
@@ -760,7 +760,7 @@ TEST_CASE_FIXTURE(Fixture, "union_of_distinct_free_types")
     CHECK("<a, b>(a, b) -> a | b" == toString(requireType("fussy")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "constrained_intersection_of_intersections")
+TEST_CASE_FIXTURE(BuiltinsFixture, "constrained_intersection_of_intersections")
 {
     ScopedFastFlag flags[] = {
         {"LuauLowerBoundsCalculation", true},
@@ -951,7 +951,7 @@ TEST_CASE_FIXTURE(Fixture, "nested_table_normalization_with_non_table__no_ice")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "visiting_a_type_twice_is_not_considered_normal")
+TEST_CASE_FIXTURE(BuiltinsFixture, "visiting_a_type_twice_is_not_considered_normal")
 {
     ScopedFastFlag sff{"LuauLowerBoundsCalculation", true};
 
@@ -976,7 +976,6 @@ TEST_CASE_FIXTURE(Fixture, "fuzz_failure_instersection_combine_must_follow")
 {
     ScopedFastFlag flags[] = {
         {"LuauLowerBoundsCalculation", true},
-        {"LuauNormalizeCombineIntersectionFix", true},
     };
 
     CheckResult result = check(R"(

tests/Parser.test.cpp

@@ -1618,8 +1618,6 @@ TEST_CASE_FIXTURE(Fixture, "end_extent_doesnt_consume_comments")
 
 TEST_CASE_FIXTURE(Fixture, "end_extent_doesnt_consume_comments_even_with_capture")
 {
-    ScopedFastFlag luauParseLocationIgnoreCommentSkipInCapture{"LuauParseLocationIgnoreCommentSkipInCapture", true};
-
     // Same should hold when comments are captured
     ParseOptions opts;
     opts.captureComments = true;

tests/RuntimeLimits.test.cpp

@@ -17,7 +17,7 @@ using namespace Luau;
 
 LUAU_FASTFLAG(LuauLowerBoundsCalculation);
 
-struct LimitFixture : Fixture
+struct LimitFixture : BuiltinsFixture
 {
 #if defined(_NOOPT) || defined(_DEBUG)
     ScopedFastInt LuauTypeInferRecursionLimit{"LuauTypeInferRecursionLimit", 100};

tests/ToDot.test.cpp

@@ -224,7 +224,7 @@ n1 -> n4 [label="typePackParam"];
     (void)toDot(requireType("a"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "metatable")
 {
     CheckResult result = check(R"(
 local a: typeof(setmetatable({}, {}))

tests/ToString.test.cpp

@@ -60,7 +60,7 @@ TEST_CASE_FIXTURE(Fixture, "named_table")
     CHECK_EQ("TheTable", toString(&table));
 }
 
-TEST_CASE_FIXTURE(Fixture, "exhaustive_toString_of_cyclic_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "exhaustive_toString_of_cyclic_table")
 {
     CheckResult result = check(R"(
         --!strict
@@ -338,7 +338,7 @@ TEST_CASE_FIXTURE(Fixture, "toStringDetailed")
     REQUIRE_EQ("c", toString(params[2], opts));
 }
 
-TEST_CASE_FIXTURE(Fixture, "toStringDetailed2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "toStringDetailed2")
 {
     ScopedFastFlag sff{"LuauUnsealedTableLiteral", true};
 

tests/TypeInfer.aliases.test.cpp

@@ -279,7 +279,7 @@ TEST_CASE_FIXTURE(Fixture, "stringify_optional_parameterized_alias")
     CHECK_EQ("Node<T>", toString(e->wantedType));
 }
 
-TEST_CASE_FIXTURE(Fixture, "general_require_multi_assign")
+TEST_CASE_FIXTURE(BuiltinsFixture, "general_require_multi_assign")
 {
     fileResolver.source["workspace/A"] = R"(
         export type myvec2 = {x: number, y: number}
@@ -317,7 +317,7 @@ TEST_CASE_FIXTURE(Fixture, "general_require_multi_assign")
     REQUIRE(bType->props.size() == 3);
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_alias_import_mutation")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_alias_import_mutation")
 {
     CheckResult result = check("type t10<x> = typeof(table)");
     LUAU_REQUIRE_NO_ERRORS(result);
@@ -385,7 +385,7 @@ type Cool = typeof(c)
     CHECK_EQ(ttv->name, "Cool");
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_alias_of_an_imported_recursive_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_alias_of_an_imported_recursive_type")
 {
     fileResolver.source["game/A"] = R"(
 export type X = { a: number, b: X? }
@@ -410,7 +410,7 @@ type X = Import.X
     CHECK_EQ(follow(*ty1), follow(*ty2));
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_alias_of_an_imported_recursive_generic_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_alias_of_an_imported_recursive_generic_type")
 {
     fileResolver.source["game/A"] = R"(
 export type X<T, U> = { a: T, b: U, C: X<T, U>? }
@@ -564,7 +564,7 @@ TEST_CASE_FIXTURE(Fixture, "non_recursive_aliases_that_reuse_a_generic_name")
  *
  * We solved this by ascribing a unique subLevel to each prototyped alias.
  */
-TEST_CASE_FIXTURE(Fixture, "do_not_quantify_unresolved_aliases")
+TEST_CASE_FIXTURE(BuiltinsFixture, "do_not_quantify_unresolved_aliases")
 {
     CheckResult result = check(R"(
         --!strict

tests/TypeInfer.annotations.test.cpp

@@ -528,7 +528,7 @@ TEST_CASE_FIXTURE(Fixture, "cloned_interface_maintains_pointers_between_definiti
     CHECK_EQ(recordType, bType);
 }
 
-TEST_CASE_FIXTURE(Fixture, "use_type_required_from_another_file")
+TEST_CASE_FIXTURE(BuiltinsFixture, "use_type_required_from_another_file")
 {
     addGlobalBinding(frontend.typeChecker, "script", frontend.typeChecker.anyType, "@test");
 
@@ -554,7 +554,7 @@ TEST_CASE_FIXTURE(Fixture, "use_type_required_from_another_file")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "cannot_use_nonexported_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "cannot_use_nonexported_type")
 {
     addGlobalBinding(frontend.typeChecker, "script", frontend.typeChecker.anyType, "@test");
 
@@ -580,7 +580,7 @@ TEST_CASE_FIXTURE(Fixture, "cannot_use_nonexported_type")
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "builtin_types_are_not_exported")
+TEST_CASE_FIXTURE(BuiltinsFixture, "builtin_types_are_not_exported")
 {
     addGlobalBinding(frontend.typeChecker, "script", frontend.typeChecker.anyType, "@test");
 
@@ -676,7 +676,7 @@ TEST_CASE_FIXTURE(Fixture, "luau_ice_is_not_special_without_the_flag")
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "luau_print_is_magic_if_the_flag_is_set")
+TEST_CASE_FIXTURE(BuiltinsFixture, "luau_print_is_magic_if_the_flag_is_set")
 {
     // Luau::resetPrintLine();
     ScopedFastFlag sffs{"DebugLuauMagicTypes", true};

tests/TypeInfer.anyerror.test.cpp

@@ -237,7 +237,7 @@ TEST_CASE_FIXTURE(Fixture, "chain_calling_error_type_yields_error")
     CHECK_EQ("*unknown*", toString(requireType("a")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "replace_every_free_type_when_unifying_a_complex_function_with_any")
+TEST_CASE_FIXTURE(BuiltinsFixture, "replace_every_free_type_when_unifying_a_complex_function_with_any")
 {
     CheckResult result = check(R"(
         local a: any
@@ -285,7 +285,7 @@ end
     LUAU_REQUIRE_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "metatable_of_any_can_be_a_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "metatable_of_any_can_be_a_table")
 {
     CheckResult result = check(R"(
 --!strict

tests/TypeInfer.builtins.test.cpp

@@ -12,7 +12,7 @@ LUAU_FASTFLAG(LuauLowerBoundsCalculation);
 
 TEST_SUITE_BEGIN("BuiltinTests");
 
-TEST_CASE_FIXTURE(Fixture, "math_things_are_defined")
+TEST_CASE_FIXTURE(BuiltinsFixture, "math_things_are_defined")
 {
     CheckResult result = check(R"(
         local a00 = math.frexp
@@ -50,7 +50,7 @@ TEST_CASE_FIXTURE(Fixture, "math_things_are_defined")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "next_iterator_should_infer_types_and_type_check")
+TEST_CASE_FIXTURE(BuiltinsFixture, "next_iterator_should_infer_types_and_type_check")
 {
     CheckResult result = check(R"(
         local a: string, b: number = next({ 1 })
@@ -63,7 +63,7 @@ TEST_CASE_FIXTURE(Fixture, "next_iterator_should_infer_types_and_type_check")
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "pairs_iterator_should_infer_types_and_type_check")
+TEST_CASE_FIXTURE(BuiltinsFixture, "pairs_iterator_should_infer_types_and_type_check")
 {
     CheckResult result = check(R"(
         type Map<K, V> = { [K]: V }
@@ -75,7 +75,7 @@ TEST_CASE_FIXTURE(Fixture, "pairs_iterator_should_infer_types_and_type_check")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "ipairs_iterator_should_infer_types_and_type_check")
+TEST_CASE_FIXTURE(BuiltinsFixture, "ipairs_iterator_should_infer_types_and_type_check")
 {
     CheckResult result = check(R"(
         type Map<K, V> = { [K]: V }
@@ -87,7 +87,7 @@ TEST_CASE_FIXTURE(Fixture, "ipairs_iterator_should_infer_types_and_type_check")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_dot_remove_optionally_returns_generic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_dot_remove_optionally_returns_generic")
 {
     CheckResult result = check(R"(
         local t = { 1 }
@@ -98,7 +98,7 @@ TEST_CASE_FIXTURE(Fixture, "table_dot_remove_optionally_returns_generic")
     CHECK_EQ(toString(requireType("n")), "number?");
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_concat_returns_string")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_concat_returns_string")
 {
     CheckResult result = check(R"(
         local r = table.concat({1,2,3,4}, ",", 2);
@@ -108,7 +108,7 @@ TEST_CASE_FIXTURE(Fixture, "table_concat_returns_string")
     CHECK_EQ(*typeChecker.stringType, *requireType("r"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "sort")
+TEST_CASE_FIXTURE(BuiltinsFixture, "sort")
 {
     CheckResult result = check(R"(
         local t = {1, 2, 3};
@@ -118,7 +118,7 @@ TEST_CASE_FIXTURE(Fixture, "sort")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "sort_with_predicate")
+TEST_CASE_FIXTURE(BuiltinsFixture, "sort_with_predicate")
 {
     CheckResult result = check(R"(
         --!strict
@@ -130,7 +130,7 @@ TEST_CASE_FIXTURE(Fixture, "sort_with_predicate")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "sort_with_bad_predicate")
+TEST_CASE_FIXTURE(BuiltinsFixture, "sort_with_bad_predicate")
 {
     CheckResult result = check(R"(
         --!strict
@@ -140,6 +140,12 @@ TEST_CASE_FIXTURE(Fixture, "sort_with_bad_predicate")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(R"(Type '(number, number) -> boolean' could not be converted into '((a, a) -> boolean)?'
+caused by:
+  None of the union options are compatible. For example: Type '(number, number) -> boolean' could not be converted into '(a, a) -> boolean'
+caused by:
+  Argument #1 type is not compatible. Type 'string' could not be converted into 'number')",
+        toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "strings_have_methods")
@@ -152,7 +158,7 @@ TEST_CASE_FIXTURE(Fixture, "strings_have_methods")
     CHECK_EQ(*typeChecker.stringType, *requireType("s"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "math_max_variatic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "math_max_variatic")
 {
     CheckResult result = check(R"(
         local n = math.max(1,2,3,4,5,6,7,8,9,0)
@@ -162,16 +168,17 @@ TEST_CASE_FIXTURE(Fixture, "math_max_variatic")
     CHECK_EQ(*typeChecker.numberType, *requireType("n"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "math_max_checks_for_numbers")
+TEST_CASE_FIXTURE(BuiltinsFixture, "math_max_checks_for_numbers")
 {
     CheckResult result = check(R"(
         local n = math.max(1,2,"3")
     )");
 
     CHECK(!result.errors.empty());
+    CHECK_EQ("Type 'string' could not be converted into 'number'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "builtin_tables_sealed")
+TEST_CASE_FIXTURE(BuiltinsFixture, "builtin_tables_sealed")
 {
     CheckResult result = check(R"LUA(
         local b = bit32
@@ -183,7 +190,7 @@ TEST_CASE_FIXTURE(Fixture, "builtin_tables_sealed")
     CHECK_EQ(bit32t->state, TableState::Sealed);
 }
 
-TEST_CASE_FIXTURE(Fixture, "lua_51_exported_globals_all_exist")
+TEST_CASE_FIXTURE(BuiltinsFixture, "lua_51_exported_globals_all_exist")
 {
     // Extracted from lua5.1
     CheckResult result = check(R"(
@@ -340,7 +347,7 @@ TEST_CASE_FIXTURE(Fixture, "lua_51_exported_globals_all_exist")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "setmetatable_unpacks_arg_types_correctly")
+TEST_CASE_FIXTURE(BuiltinsFixture, "setmetatable_unpacks_arg_types_correctly")
 {
     CheckResult result = check(R"(
         setmetatable({}, setmetatable({}, {}))
@@ -348,7 +355,7 @@ TEST_CASE_FIXTURE(Fixture, "setmetatable_unpacks_arg_types_correctly")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_insert_correctly_infers_type_of_array_2_args_overload")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_correctly_infers_type_of_array_2_args_overload")
 {
     CheckResult result = check(R"(
         local t = {}
@@ -360,7 +367,7 @@ TEST_CASE_FIXTURE(Fixture, "table_insert_correctly_infers_type_of_array_2_args_o
     CHECK_EQ(typeChecker.stringType, requireType("s"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_insert_correctly_infers_type_of_array_3_args_overload")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_correctly_infers_type_of_array_3_args_overload")
 {
     CheckResult result = check(R"(
         local t = {}
@@ -372,7 +379,7 @@ TEST_CASE_FIXTURE(Fixture, "table_insert_correctly_infers_type_of_array_3_args_o
     CHECK_EQ("string", toString(requireType("s")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_pack")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_pack")
 {
     CheckResult result = check(R"(
         local t = table.pack(1, "foo", true)
@@ -382,7 +389,7 @@ TEST_CASE_FIXTURE(Fixture, "table_pack")
     CHECK_EQ("{| [number]: boolean | number | string, n: number |}", toString(requireType("t")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_pack_variadic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_pack_variadic")
 {
     CheckResult result = check(R"(
 --!strict
@@ -397,7 +404,7 @@ local t = table.pack(f())
     CHECK_EQ("{| [number]: number | string, n: number |}", toString(requireType("t")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_pack_reduce")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_pack_reduce")
 {
     CheckResult result = check(R"(
         local t = table.pack(1, 2, true)
@@ -414,7 +421,7 @@ TEST_CASE_FIXTURE(Fixture, "table_pack_reduce")
     CHECK_EQ("{| [number]: string, n: number |}", toString(requireType("t")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "gcinfo")
+TEST_CASE_FIXTURE(BuiltinsFixture, "gcinfo")
 {
     CheckResult result = check(R"(
         local n = gcinfo()
@@ -424,12 +431,12 @@ TEST_CASE_FIXTURE(Fixture, "gcinfo")
     CHECK_EQ(*typeChecker.numberType, *requireType("n"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "getfenv")
+TEST_CASE_FIXTURE(BuiltinsFixture, "getfenv")
 {
     LUAU_REQUIRE_NO_ERRORS(check("getfenv(1)"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "os_time_takes_optional_date_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "os_time_takes_optional_date_table")
 {
     CheckResult result = check(R"(
         local n1 = os.time()
@@ -443,7 +450,7 @@ TEST_CASE_FIXTURE(Fixture, "os_time_takes_optional_date_table")
     CHECK_EQ(*typeChecker.numberType, *requireType("n3"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "thread_is_a_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "thread_is_a_type")
 {
     CheckResult result = check(R"(
         local co = coroutine.create(function() end)
@@ -453,7 +460,7 @@ TEST_CASE_FIXTURE(Fixture, "thread_is_a_type")
     CHECK_EQ(*typeChecker.threadType, *requireType("co"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "coroutine_resume_anything_goes")
+TEST_CASE_FIXTURE(BuiltinsFixture, "coroutine_resume_anything_goes")
 {
     CheckResult result = check(R"(
         local function nifty(x, y)
@@ -471,7 +478,7 @@ TEST_CASE_FIXTURE(Fixture, "coroutine_resume_anything_goes")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "coroutine_wrap_anything_goes")
+TEST_CASE_FIXTURE(BuiltinsFixture, "coroutine_wrap_anything_goes")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -490,7 +497,7 @@ TEST_CASE_FIXTURE(Fixture, "coroutine_wrap_anything_goes")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "setmetatable_should_not_mutate_persisted_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "setmetatable_should_not_mutate_persisted_types")
 {
     CheckResult result = check(R"(
         local string = string
@@ -505,7 +512,7 @@ TEST_CASE_FIXTURE(Fixture, "setmetatable_should_not_mutate_persisted_types")
     REQUIRE(ttv);
 }
 
-TEST_CASE_FIXTURE(Fixture, "string_format_arg_types_inference")
+TEST_CASE_FIXTURE(BuiltinsFixture, "string_format_arg_types_inference")
 {
     CheckResult result = check(R"(
         --!strict
@@ -518,7 +525,7 @@ TEST_CASE_FIXTURE(Fixture, "string_format_arg_types_inference")
     CHECK_EQ("(number, number, string) -> string", toString(requireType("f")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "string_format_arg_count_mismatch")
+TEST_CASE_FIXTURE(BuiltinsFixture, "string_format_arg_count_mismatch")
 {
     CheckResult result = check(R"(
         --!strict
@@ -534,7 +541,7 @@ TEST_CASE_FIXTURE(Fixture, "string_format_arg_count_mismatch")
     CHECK_EQ(result.errors[2].location.begin.line, 4);
 }
 
-TEST_CASE_FIXTURE(Fixture, "string_format_correctly_ordered_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "string_format_correctly_ordered_types")
 {
     CheckResult result = check(R"(
         --!strict
@@ -548,7 +555,7 @@ TEST_CASE_FIXTURE(Fixture, "string_format_correctly_ordered_types")
     CHECK_EQ(tm->givenType, typeChecker.numberType);
 }
 
-TEST_CASE_FIXTURE(Fixture, "xpcall")
+TEST_CASE_FIXTURE(BuiltinsFixture, "xpcall")
 {
     CheckResult result = check(R"(
         --!strict
@@ -564,7 +571,7 @@ TEST_CASE_FIXTURE(Fixture, "xpcall")
     CHECK_EQ("boolean", toString(requireType("c")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "see_thru_select")
+TEST_CASE_FIXTURE(BuiltinsFixture, "see_thru_select")
 {
     CheckResult result = check(R"(
         local a:number, b:boolean = select(2,"hi", 10, true)
@@ -573,7 +580,7 @@ TEST_CASE_FIXTURE(Fixture, "see_thru_select")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "see_thru_select_count")
+TEST_CASE_FIXTURE(BuiltinsFixture, "see_thru_select_count")
 {
     CheckResult result = check(R"(
         local a = select("#","hi", 10, true)
@@ -583,7 +590,7 @@ TEST_CASE_FIXTURE(Fixture, "see_thru_select_count")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_with_decimal_argument_is_rounded_down")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_with_decimal_argument_is_rounded_down")
 {
     CheckResult result = check(R"(
         local a: number, b: boolean = select(2.9, "foo", 1, true)
@@ -608,7 +615,7 @@ TEST_CASE_FIXTURE(Fixture, "bad_select_should_not_crash")
     CHECK_LE(0, result.errors.size());
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_way_out_of_range")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_way_out_of_range")
 {
     CheckResult result = check(R"(
         select(5432598430953240958)
@@ -619,7 +626,7 @@ TEST_CASE_FIXTURE(Fixture, "select_way_out_of_range")
     CHECK_EQ("bad argument #1 to select (index out of range)", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_slightly_out_of_range")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_slightly_out_of_range")
 {
     CheckResult result = check(R"(
         select(3, "a", 1)
@@ -630,7 +637,7 @@ TEST_CASE_FIXTURE(Fixture, "select_slightly_out_of_range")
     CHECK_EQ("bad argument #1 to select (index out of range)", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_with_variadic_typepack_tail")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_with_variadic_typepack_tail")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -649,7 +656,7 @@ TEST_CASE_FIXTURE(Fixture, "select_with_variadic_typepack_tail")
     CHECK_EQ("any", toString(requireType("quux")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_with_variadic_typepack_tail_and_string_head")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_with_variadic_typepack_tail_and_string_head")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -703,7 +710,7 @@ TEST_CASE_FIXTURE(Fixture, "string_format_use_correct_argument2")
     CHECK_EQ("Type 'number' could not be converted into 'string'", toString(result.errors[1]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "debug_traceback_is_crazy")
+TEST_CASE_FIXTURE(BuiltinsFixture, "debug_traceback_is_crazy")
 {
     CheckResult result = check(R"(
 local co: thread = ...
@@ -720,7 +727,7 @@ debug.traceback(co, "msg", 1)
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "debug_info_is_crazy")
+TEST_CASE_FIXTURE(BuiltinsFixture, "debug_info_is_crazy")
 {
     CheckResult result = check(R"(
 local co: thread, f: ()->() = ...
@@ -734,7 +741,7 @@ debug.info(f, "n")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "aliased_string_format")
+TEST_CASE_FIXTURE(BuiltinsFixture, "aliased_string_format")
 {
     CheckResult result = check(R"(
         local fmt = string.format
@@ -745,7 +752,7 @@ TEST_CASE_FIXTURE(Fixture, "aliased_string_format")
     CHECK_EQ("Type 'string' could not be converted into 'number'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "string_lib_self_noself")
+TEST_CASE_FIXTURE(BuiltinsFixture, "string_lib_self_noself")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -764,7 +771,7 @@ TEST_CASE_FIXTURE(Fixture, "string_lib_self_noself")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "gmatch_definition")
+TEST_CASE_FIXTURE(BuiltinsFixture, "gmatch_definition")
 {
     CheckResult result = check(R"_(
 local a, b, c = ("hey"):gmatch("(.)(.)(.)")()
@@ -777,7 +784,7 @@ end
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "select_on_variadic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "select_on_variadic")
 {
     CheckResult result = check(R"(
         local function f(): (number, ...(boolean | number))
@@ -793,7 +800,7 @@ TEST_CASE_FIXTURE(Fixture, "select_on_variadic")
     CHECK_EQ("any", toString(requireType("c")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "string_format_report_all_type_errors_at_correct_positions")
+TEST_CASE_FIXTURE(BuiltinsFixture, "string_format_report_all_type_errors_at_correct_positions")
 {
     CheckResult result = check(R"(
         ("%s%d%s"):format(1, "hello", true)
@@ -825,7 +832,7 @@ TEST_CASE_FIXTURE(Fixture, "string_format_report_all_type_errors_at_correct_posi
     CHECK_EQ(TypeErrorData(TypeMismatch{stringType, booleanType}), result.errors[5].data);
 }
 
-TEST_CASE_FIXTURE(Fixture, "tonumber_returns_optional_number_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "tonumber_returns_optional_number_type")
 {
     CheckResult result = check(R"(
         --!strict
@@ -836,7 +843,7 @@ TEST_CASE_FIXTURE(Fixture, "tonumber_returns_optional_number_type")
     CHECK_EQ("Type 'number?' could not be converted into 'number'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "tonumber_returns_optional_number_type2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "tonumber_returns_optional_number_type2")
 {
     CheckResult result = check(R"(
         --!strict
@@ -846,7 +853,7 @@ TEST_CASE_FIXTURE(Fixture, "tonumber_returns_optional_number_type2")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "dont_add_definitions_to_persistent_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "dont_add_definitions_to_persistent_types")
 {
     CheckResult result = check(R"(
         local f = math.sin
@@ -868,7 +875,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_add_definitions_to_persistent_types")
     REQUIRE(gtv->definition);
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_removes_falsy_types")
 {
     ScopedFastFlag sff[]{
         {"LuauAssertStripsFalsyTypes", true},
@@ -889,7 +896,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types")
         CHECK_EQ("((boolean | number)?) -> boolean | number", toString(requireType("f")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_removes_falsy_types2")
 {
     ScopedFastFlag sff[]{
         {"LuauAssertStripsFalsyTypes", true},
@@ -907,7 +914,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types2")
     CHECK_EQ("((boolean | number)?) -> number | true", toString(requireType("f")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types_even_from_type_pack_tail_but_only_for_the_first_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_removes_falsy_types_even_from_type_pack_tail_but_only_for_the_first_type")
 {
     ScopedFastFlag sff[]{
         {"LuauAssertStripsFalsyTypes", true},
@@ -924,7 +931,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types_even_from_type_pack_tail_
     CHECK_EQ("(...number?) -> (number, ...number?)", toString(requireType("f")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_returns_false_and_string_iff_it_knows_the_first_argument_cannot_be_truthy")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_returns_false_and_string_iff_it_knows_the_first_argument_cannot_be_truthy")
 {
     ScopedFastFlag sff[]{
         {"LuauAssertStripsFalsyTypes", true},
@@ -941,7 +948,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_returns_false_and_string_iff_it_knows_the_fir
     CHECK_EQ("(nil) -> nil", toString(requireType("f")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_freeze_is_generic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_freeze_is_generic")
 {
     CheckResult result = check(R"(
         local t1: {a: number} = {a = 42}
@@ -968,7 +975,7 @@ TEST_CASE_FIXTURE(Fixture, "table_freeze_is_generic")
     CHECK_EQ("*unknown*", toString(requireType("d")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "set_metatable_needs_arguments")
+TEST_CASE_FIXTURE(BuiltinsFixture, "set_metatable_needs_arguments")
 {
     ScopedFastFlag sff{"LuauSetMetaTableArgsCheck", true};
     CheckResult result = check(R"(
@@ -991,7 +998,7 @@ local function f(a: typeof(f)) end
     CHECK_EQ("Unknown global 'f'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "no_persistent_typelevel_change")
+TEST_CASE_FIXTURE(BuiltinsFixture, "no_persistent_typelevel_change")
 {
     TypeId mathTy = requireType(typeChecker.globalScope, "math");
     REQUIRE(mathTy);
@@ -1008,7 +1015,7 @@ TEST_CASE_FIXTURE(Fixture, "no_persistent_typelevel_change")
     CHECK(ftv->level.subLevel == original.subLevel);
 }
 
-TEST_CASE_FIXTURE(Fixture, "global_singleton_types_are_sealed")
+TEST_CASE_FIXTURE(BuiltinsFixture, "global_singleton_types_are_sealed")
 {
     CheckResult result = check(R"(
 local function f(x: string)

tests/TypeInfer.classes.test.cpp

@@ -10,7 +10,7 @@
 using namespace Luau;
 using std::nullopt;
 
-struct ClassFixture : Fixture
+struct ClassFixture : BuiltinsFixture
 {
     ClassFixture()
     {

tests/TypeInfer.functions.test.cpp

@@ -85,7 +85,7 @@ TEST_CASE_FIXTURE(Fixture, "vararg_functions_should_allow_calls_of_any_types_and
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "vararg_function_is_quantified")
+TEST_CASE_FIXTURE(BuiltinsFixture, "vararg_function_is_quantified")
 {
     CheckResult result = check(R"(
         local T = {}
@@ -555,7 +555,7 @@ TEST_CASE_FIXTURE(Fixture, "higher_order_function_3")
     CHECK(bool(argType->indexer));
 }
 
-TEST_CASE_FIXTURE(Fixture, "higher_order_function_4")
+TEST_CASE_FIXTURE(BuiltinsFixture, "higher_order_function_4")
 {
     CheckResult result = check(R"(
         function bottomupmerge(comp, a, b, left, mid, right)
@@ -620,7 +620,7 @@ TEST_CASE_FIXTURE(Fixture, "higher_order_function_4")
     CHECK_EQ(*arg0->indexer->indexResultType, *arg1Args[1]);
 }
 
-TEST_CASE_FIXTURE(Fixture, "mutual_recursion")
+TEST_CASE_FIXTURE(BuiltinsFixture, "mutual_recursion")
 {
     CheckResult result = check(R"(
         --!strict
@@ -639,7 +639,7 @@ TEST_CASE_FIXTURE(Fixture, "mutual_recursion")
     dumpErrors(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "toposort_doesnt_break_mutual_recursion")
+TEST_CASE_FIXTURE(BuiltinsFixture, "toposort_doesnt_break_mutual_recursion")
 {
     CheckResult result = check(R"(
         --!strict
@@ -676,7 +676,7 @@ TEST_CASE_FIXTURE(Fixture, "check_function_before_lambda_that_uses_it")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "it_is_ok_to_oversaturate_a_higher_order_function_argument")
+TEST_CASE_FIXTURE(BuiltinsFixture, "it_is_ok_to_oversaturate_a_higher_order_function_argument")
 {
     CheckResult result = check(R"(
         function onerror() end
@@ -794,7 +794,7 @@ TEST_CASE_FIXTURE(Fixture, "calling_function_with_incorrect_argument_type_yields
                                                                                       }}));
 }
 
-TEST_CASE_FIXTURE(Fixture, "calling_function_with_anytypepack_doesnt_leak_free_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "calling_function_with_anytypepack_doesnt_leak_free_types")
 {
     ScopedFastFlag sff[]{
         {"LuauReturnTypeInferenceInNonstrict", true},
@@ -966,7 +966,7 @@ TEST_CASE_FIXTURE(Fixture, "return_type_by_overload")
     CHECK_EQ("string", toString(requireType("z")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "infer_anonymous_function_arguments")
+TEST_CASE_FIXTURE(BuiltinsFixture, "infer_anonymous_function_arguments")
 {
     // Simple direct arg to arg propagation
     CheckResult result = check(R"(
@@ -1068,7 +1068,7 @@ f(function(x) return x * 2 end)
     }
 }
 
-TEST_CASE_FIXTURE(Fixture, "infer_anonymous_function_arguments")
+TEST_CASE_FIXTURE(BuiltinsFixture, "infer_anonymous_function_arguments")
 {
     // Simple direct arg to arg propagation
     CheckResult result = check(R"(
@@ -1287,10 +1287,8 @@ caused by:
   Return #2 type is not compatible. Type 'string' could not be converted into 'boolean')");
 }
 
-TEST_CASE_FIXTURE(Fixture, "function_decl_quantify_right_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_quantify_right_type")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     fileResolver.source["game/isAMagicMock"] = R"(
 --!nonstrict
 return function(value)
@@ -1311,10 +1309,8 @@ end
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_sealed_overwrite")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_non_self_sealed_overwrite")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     CheckResult result = check(R"(
 function string.len(): number
     return 1
@@ -1333,11 +1329,8 @@ print(string.len('hello'))
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_sealed_overwrite_2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_non_self_sealed_overwrite_2")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-    ScopedFastFlag inferStatFunction{"LuauInferStatFunction", true};
-
     CheckResult result = check(R"(
 local t: { f: ((x: number) -> number)? } = {}
 
@@ -1477,11 +1470,8 @@ TEST_CASE_FIXTURE(Fixture, "inferred_higher_order_functions_are_quantified_at_th
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_unsealed_overwrite")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_decl_non_self_unsealed_overwrite")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-    ScopedFastFlag inferStatFunction{"LuauInferStatFunction", true};
-
     CheckResult result = check(R"(
 local t = { f = nil :: ((x: number) -> number)? }
 
@@ -1518,8 +1508,6 @@ TEST_CASE_FIXTURE(Fixture, "strict_mode_ok_with_missing_arguments")
 
 TEST_CASE_FIXTURE(Fixture, "function_statement_sealed_table_assignment_through_indexer")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     CheckResult result = check(R"(
 local t: {[string]: () -> number} = {}
 
@@ -1580,7 +1568,7 @@ wrapper(test)
     CHECK(acm->isVariadic);
 }
 
-TEST_CASE_FIXTURE(Fixture, "too_few_arguments_variadic_generic2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "too_few_arguments_variadic_generic2")
 {
     CheckResult result = check(R"(
 function test(a: number, b: string, ...)

tests/TypeInfer.generics.test.cpp

@@ -67,7 +67,7 @@ TEST_CASE_FIXTURE(Fixture, "local_vars_can_be_polytypes")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "inferred_local_vars_can_be_polytypes")
+TEST_CASE_FIXTURE(BuiltinsFixture, "inferred_local_vars_can_be_polytypes")
 {
     CheckResult result = check(R"(
         local function id(x) return x end
@@ -79,7 +79,7 @@ TEST_CASE_FIXTURE(Fixture, "inferred_local_vars_can_be_polytypes")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "local_vars_can_be_instantiated_polytypes")
+TEST_CASE_FIXTURE(BuiltinsFixture, "local_vars_can_be_instantiated_polytypes")
 {
     CheckResult result = check(R"(
         local function id(x) return x end
@@ -609,7 +609,7 @@ TEST_CASE_FIXTURE(Fixture, "typefuns_sharing_types")
     CHECK(requireType("y1") == requireType("y2"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "bound_tables_do_not_clone_original_fields")
+TEST_CASE_FIXTURE(BuiltinsFixture, "bound_tables_do_not_clone_original_fields")
 {
     CheckResult result = check(R"(
 local exports = {}
@@ -675,7 +675,7 @@ local d: D = c
         R"(Type '() -> ()' could not be converted into '<T...>() -> ()'; different number of generic type pack parameters)");
 }
 
-TEST_CASE_FIXTURE(Fixture, "generic_functions_dont_cache_type_parameters")
+TEST_CASE_FIXTURE(BuiltinsFixture, "generic_functions_dont_cache_type_parameters")
 {
     CheckResult result = check(R"(
 -- See https://github.com/Roblox/luau/issues/332
@@ -1013,7 +1013,7 @@ TEST_CASE_FIXTURE(Fixture, "no_stack_overflow_from_quantifying")
     CHECK(it != result.errors.end());
 }
 
-TEST_CASE_FIXTURE(Fixture, "infer_generic_function_function_argument")
+TEST_CASE_FIXTURE(BuiltinsFixture, "infer_generic_function_function_argument")
 {
     ScopedFastFlag sff{"LuauUnsealedTableLiteral", true};
 
@@ -1078,7 +1078,7 @@ TEST_CASE_FIXTURE(Fixture, "infer_generic_function_function_argument_overloaded"
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "infer_generic_lib_function_function_argument")
+TEST_CASE_FIXTURE(BuiltinsFixture, "infer_generic_lib_function_function_argument")
 {
     CheckResult result = check(R"(
 local a = {{x=4}, {x=7}, {x=1}}

tests/TypeInfer.intersectionTypes.test.cpp

@@ -316,8 +316,6 @@ TEST_CASE_FIXTURE(Fixture, "table_intersection_write_sealed")
 
 TEST_CASE_FIXTURE(Fixture, "table_intersection_write_sealed_indirect")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     CheckResult result = check(R"(
         type X = { x: (number) -> number }
         type Y = { y: (string) -> string }
@@ -351,8 +349,6 @@ caused by:
 
 TEST_CASE_FIXTURE(Fixture, "table_write_sealed_indirect")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     // After normalization, previous 'table_intersection_write_sealed_indirect' is identical to this one
     CheckResult result = check(R"(
     type XY = { x: (number) -> number, y: (string) -> string }
@@ -375,7 +371,7 @@ caused by:
     CHECK_EQ(toString(result.errors[3]), "Cannot add property 'w' to table 'XY'");
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_intersection_setmetatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_intersection_setmetatable")
 {
     CheckResult result = check(R"(
         local t: {} & {}

tests/TypeInfer.loops.test.cpp

@@ -29,7 +29,7 @@ TEST_CASE_FIXTURE(Fixture, "for_loop")
     CHECK_EQ(*typeChecker.numberType, *requireType("q"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_loop")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_loop")
 {
     CheckResult result = check(R"(
         local n
@@ -46,7 +46,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop")
     CHECK_EQ(*typeChecker.stringType, *requireType("s"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_loop_with_next")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_loop_with_next")
 {
     CheckResult result = check(R"(
         local n
@@ -90,7 +90,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_should_fail_with_non_function_iterator")
     CHECK_EQ("Cannot call non-function string", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_with_just_one_iterator_is_ok")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_with_just_one_iterator_is_ok")
 {
     CheckResult result = check(R"(
         local function keys(dictionary)
@@ -109,7 +109,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_with_just_one_iterator_is_ok")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_with_a_custom_iterator_should_type_check")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_with_a_custom_iterator_should_type_check")
 {
     CheckResult result = check(R"(
         local function range(l, h): () -> number
@@ -161,7 +161,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_on_non_function")
     REQUIRE(get<CannotCallNonFunction>(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_loop_error_on_factory_not_returning_the_right_amount_of_values")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_loop_error_on_factory_not_returning_the_right_amount_of_values")
 {
     CheckResult result = check(R"(
         local function hasDivisors(value: number, table)
@@ -210,7 +210,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_error_on_factory_not_returning_the_right
     CHECK_EQ(typeChecker.stringType, tm->givenType);
 }
 
-TEST_CASE_FIXTURE(Fixture, "for_in_loop_error_on_iterator_requiring_args_but_none_given")
+TEST_CASE_FIXTURE(BuiltinsFixture, "for_in_loop_error_on_iterator_requiring_args_but_none_given")
 {
     CheckResult result = check(R"(
         function prime_iter(state, index)
@@ -288,7 +288,7 @@ TEST_CASE_FIXTURE(Fixture, "repeat_loop_condition_binds_to_its_block")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "symbols_in_repeat_block_should_not_be_visible_beyond_until_condition")
+TEST_CASE_FIXTURE(BuiltinsFixture, "symbols_in_repeat_block_should_not_be_visible_beyond_until_condition")
 {
     CheckResult result = check(R"(
         repeat
@@ -301,7 +301,7 @@ TEST_CASE_FIXTURE(Fixture, "symbols_in_repeat_block_should_not_be_visible_beyond
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "varlist_declared_by_for_in_loop_should_be_free")
+TEST_CASE_FIXTURE(BuiltinsFixture, "varlist_declared_by_for_in_loop_should_be_free")
 {
     CheckResult result = check(R"(
         local T = {}
@@ -316,7 +316,7 @@ TEST_CASE_FIXTURE(Fixture, "varlist_declared_by_for_in_loop_should_be_free")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "properly_infer_iteratee_is_a_free_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "properly_infer_iteratee_is_a_free_table")
 {
     // In this case, we cannot know the element type of the table {}.  It could be anything.
     // We therefore must initially ascribe a free typevar to iter.
@@ -329,7 +329,7 @@ TEST_CASE_FIXTURE(Fixture, "properly_infer_iteratee_is_a_free_table")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "correctly_scope_locals_while")
+TEST_CASE_FIXTURE(BuiltinsFixture, "correctly_scope_locals_while")
 {
     CheckResult result = check(R"(
         while true do
@@ -346,7 +346,7 @@ TEST_CASE_FIXTURE(Fixture, "correctly_scope_locals_while")
     CHECK_EQ(us->name, "a");
 }
 
-TEST_CASE_FIXTURE(Fixture, "ipairs_produces_integral_indices")
+TEST_CASE_FIXTURE(BuiltinsFixture, "ipairs_produces_integral_indices")
 {
     CheckResult result = check(R"(
         local key
@@ -378,7 +378,7 @@ TEST_CASE_FIXTURE(Fixture, "for_in_loop_where_iteratee_is_free")
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "unreachable_code_after_infinite_loop")
+TEST_CASE_FIXTURE(BuiltinsFixture, "unreachable_code_after_infinite_loop")
 {
     {
         CheckResult result = check(R"(
@@ -460,7 +460,7 @@ TEST_CASE_FIXTURE(Fixture, "unreachable_code_after_infinite_loop")
     }
 }
 
-TEST_CASE_FIXTURE(Fixture, "loop_typecheck_crash_on_empty_optional")
+TEST_CASE_FIXTURE(BuiltinsFixture, "loop_typecheck_crash_on_empty_optional")
 {
     CheckResult result = check(R"(
         local t = {}
@@ -541,7 +541,7 @@ TEST_CASE_FIXTURE(Fixture, "loop_iter_no_indexer")
     CHECK_EQ("Cannot iterate over a table without indexer", ge->message);
 }
 
-TEST_CASE_FIXTURE(Fixture, "loop_iter_iter_metamethod")
+TEST_CASE_FIXTURE(BuiltinsFixture, "loop_iter_iter_metamethod")
 {
     ScopedFastFlag sff{"LuauTypecheckIter", true};
 

tests/TypeInfer.modules.test.cpp

@@ -16,7 +16,7 @@ LUAU_FASTFLAG(LuauTableSubtypingVariance2)
 
 TEST_SUITE_BEGIN("TypeInferModules");
 
-TEST_CASE_FIXTURE(Fixture, "require")
+TEST_CASE_FIXTURE(BuiltinsFixture, "require")
 {
     fileResolver.source["game/A"] = R"(
         local function hooty(x: number): string
@@ -54,7 +54,7 @@ TEST_CASE_FIXTURE(Fixture, "require")
     REQUIRE_EQ("number", toString(*hType));
 }
 
-TEST_CASE_FIXTURE(Fixture, "require_types")
+TEST_CASE_FIXTURE(BuiltinsFixture, "require_types")
 {
     fileResolver.source["workspace/A"] = R"(
         export type Point = {x: number, y: number}
@@ -69,7 +69,7 @@ TEST_CASE_FIXTURE(Fixture, "require_types")
     )";
 
     CheckResult bResult = frontend.check("workspace/B");
-    dumpErrors(bResult);
+    LUAU_REQUIRE_NO_ERRORS(bResult);
 
     ModulePtr b = frontend.moduleResolver.modules["workspace/B"];
     REQUIRE(b != nullptr);
@@ -78,7 +78,7 @@ TEST_CASE_FIXTURE(Fixture, "require_types")
     REQUIRE_MESSAGE(bool(get<TableTypeVar>(hType)), "Expected table but got " << toString(hType));
 }
 
-TEST_CASE_FIXTURE(Fixture, "require_a_variadic_function")
+TEST_CASE_FIXTURE(BuiltinsFixture, "require_a_variadic_function")
 {
     fileResolver.source["game/A"] = R"(
         local T = {}
@@ -121,7 +121,7 @@ TEST_CASE_FIXTURE(Fixture, "type_error_of_unknown_qualified_type")
     REQUIRE_EQ(result.errors[0], (TypeError{Location{{1, 17}, {1, 40}}, UnknownSymbol{"SomeModule.DoesNotExist"}}));
 }
 
-TEST_CASE_FIXTURE(Fixture, "require_module_that_does_not_export")
+TEST_CASE_FIXTURE(BuiltinsFixture, "require_module_that_does_not_export")
 {
     const std::string sourceA = R"(
     )";
@@ -148,7 +148,7 @@ TEST_CASE_FIXTURE(Fixture, "require_module_that_does_not_export")
     CHECK_EQ("*unknown*", toString(hootyType));
 }
 
-TEST_CASE_FIXTURE(Fixture, "warn_if_you_try_to_require_a_non_modulescript")
+TEST_CASE_FIXTURE(BuiltinsFixture, "warn_if_you_try_to_require_a_non_modulescript")
 {
     fileResolver.source["Modules/A"] = "";
     fileResolver.sourceTypes["Modules/A"] = SourceCode::Local;
@@ -164,7 +164,7 @@ TEST_CASE_FIXTURE(Fixture, "warn_if_you_try_to_require_a_non_modulescript")
     CHECK(get<IllegalRequire>(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "general_require_call_expression")
+TEST_CASE_FIXTURE(BuiltinsFixture, "general_require_call_expression")
 {
     fileResolver.source["game/A"] = R"(
 --!strict
@@ -183,7 +183,7 @@ a = tbl.abc.def
     CHECK_EQ("Type 'number' could not be converted into 'string'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "general_require_type_mismatch")
+TEST_CASE_FIXTURE(BuiltinsFixture, "general_require_type_mismatch")
 {
     fileResolver.source["game/A"] = R"(
 return { def = 4 }
@@ -219,7 +219,7 @@ return m
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "custom_require_global")
+TEST_CASE_FIXTURE(BuiltinsFixture, "custom_require_global")
 {
     CheckResult result = check(R"(
 --!nonstrict
@@ -231,7 +231,7 @@ local crash = require(game.A)
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "require_failed_module")
+TEST_CASE_FIXTURE(BuiltinsFixture, "require_failed_module")
 {
     fileResolver.source["game/A"] = R"(
 return unfortunately()
@@ -267,7 +267,7 @@ function x:Destroy(): () end
     LUAU_REQUIRE_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "do_not_modify_imported_types_2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "do_not_modify_imported_types_2")
 {
     fileResolver.source["game/A"] = R"(
 export type Type = { x: { a: number } }
@@ -285,7 +285,7 @@ type Rename = typeof(x.x)
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "do_not_modify_imported_types_3")
+TEST_CASE_FIXTURE(BuiltinsFixture, "do_not_modify_imported_types_3")
 {
     fileResolver.source["game/A"] = R"(
 local y = setmetatable({}, {})
@@ -304,7 +304,7 @@ type Rename = typeof(x.x)
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "module_type_conflict")
+TEST_CASE_FIXTURE(BuiltinsFixture, "module_type_conflict")
 {
     fileResolver.source["game/A"] = R"(
 export type T = { x: number }
@@ -338,7 +338,7 @@ caused by:
     }
 }
 
-TEST_CASE_FIXTURE(Fixture, "module_type_conflict_instantiated")
+TEST_CASE_FIXTURE(BuiltinsFixture, "module_type_conflict_instantiated")
 {
     fileResolver.source["game/A"] = R"(
 export type Wrap<T> = { x: T }

tests/TypeInfer.oop.test.cpp

@@ -142,7 +142,7 @@ TEST_CASE_FIXTURE(Fixture, "inferring_hundreds_of_self_calls_should_not_suffocat
     CHECK_GE(50, module->internalTypes.typeVars.size());
 }
 
-TEST_CASE_FIXTURE(Fixture, "object_constructor_can_refer_to_method_of_self")
+TEST_CASE_FIXTURE(BuiltinsFixture, "object_constructor_can_refer_to_method_of_self")
 {
     // CLI-30902
     CheckResult result = check(R"(
@@ -243,7 +243,7 @@ TEST_CASE_FIXTURE(Fixture, "inferred_methods_of_free_tables_have_the_same_level_
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_oop")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_oop")
 {
     CheckResult result = check(R"(
    --!strict

tests/TypeInfer.operators.test.cpp

@@ -77,7 +77,7 @@ TEST_CASE_FIXTURE(Fixture, "and_or_ternary")
     CHECK_EQ(toString(*requireType("s")), "number | string");
 }
 
-TEST_CASE_FIXTURE(Fixture, "primitive_arith_no_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "primitive_arith_no_metatable")
 {
     CheckResult result = check(R"(
         function add(a: number, b: string)
@@ -140,7 +140,7 @@ TEST_CASE_FIXTURE(Fixture, "some_primitive_binary_ops")
     CHECK_EQ("number", toString(requireType("c")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "typecheck_overloaded_multiply_that_is_an_intersection")
+TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_overloaded_multiply_that_is_an_intersection")
 {
     CheckResult result = check(R"(
         --!strict
@@ -174,7 +174,7 @@ TEST_CASE_FIXTURE(Fixture, "typecheck_overloaded_multiply_that_is_an_intersectio
     CHECK_EQ("Vec3", toString(requireType("e")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "typecheck_overloaded_multiply_that_is_an_intersection_on_rhs")
+TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_overloaded_multiply_that_is_an_intersection_on_rhs")
 {
     CheckResult result = check(R"(
         --!strict
@@ -245,7 +245,7 @@ TEST_CASE_FIXTURE(Fixture, "cannot_indirectly_compare_types_that_do_not_have_a_m
     REQUIRE_EQ(gen->message, "Type a cannot be compared with < because it has no metatable");
 }
 
-TEST_CASE_FIXTURE(Fixture, "cannot_indirectly_compare_types_that_do_not_offer_overloaded_ordering_operators")
+TEST_CASE_FIXTURE(BuiltinsFixture, "cannot_indirectly_compare_types_that_do_not_offer_overloaded_ordering_operators")
 {
     CheckResult result = check(R"(
         local M = {}
@@ -266,7 +266,7 @@ TEST_CASE_FIXTURE(Fixture, "cannot_indirectly_compare_types_that_do_not_offer_ov
     REQUIRE_EQ(gen->message, "Table M does not offer metamethod __lt");
 }
 
-TEST_CASE_FIXTURE(Fixture, "cannot_compare_tables_that_do_not_have_the_same_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "cannot_compare_tables_that_do_not_have_the_same_metatable")
 {
     CheckResult result = check(R"(
         --!strict
@@ -289,7 +289,7 @@ TEST_CASE_FIXTURE(Fixture, "cannot_compare_tables_that_do_not_have_the_same_meta
     REQUIRE_EQ((Location{{11, 18}, {11, 23}}), result.errors[1].location);
 }
 
-TEST_CASE_FIXTURE(Fixture, "produce_the_correct_error_message_when_comparing_a_table_with_a_metatable_with_one_that_does_not")
+TEST_CASE_FIXTURE(BuiltinsFixture, "produce_the_correct_error_message_when_comparing_a_table_with_a_metatable_with_one_that_does_not")
 {
     CheckResult result = check(R"(
         --!strict
@@ -361,7 +361,7 @@ TEST_CASE_FIXTURE(Fixture, "compound_assign_mismatch_result")
     CHECK_EQ(result.errors[1], (TypeError{Location{{2, 8}, {2, 15}}, TypeMismatch{typeChecker.stringType, typeChecker.numberType}}));
 }
 
-TEST_CASE_FIXTURE(Fixture, "compound_assign_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "compound_assign_metatable")
 {
     CheckResult result = check(R"(
         --!strict
@@ -381,7 +381,7 @@ TEST_CASE_FIXTURE(Fixture, "compound_assign_metatable")
     CHECK_EQ(0, result.errors.size());
 }
 
-TEST_CASE_FIXTURE(Fixture, "compound_assign_mismatch_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "compound_assign_mismatch_metatable")
 {
     CheckResult result = check(R"(
         --!strict
@@ -428,7 +428,7 @@ local x = false
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "typecheck_unary_minus")
+TEST_CASE_FIXTURE(BuiltinsFixture, "typecheck_unary_minus")
 {
     CheckResult result = check(R"(
         --!strict
@@ -461,7 +461,7 @@ TEST_CASE_FIXTURE(Fixture, "typecheck_unary_minus")
     REQUIRE_EQ(gen->message, "Unary operator '-' not supported by type 'bar'");
 }
 
-TEST_CASE_FIXTURE(Fixture, "unary_not_is_boolean")
+TEST_CASE_FIXTURE(BuiltinsFixture, "unary_not_is_boolean")
 {
     CheckResult result = check(R"(
         local b = not "string"
@@ -473,7 +473,7 @@ TEST_CASE_FIXTURE(Fixture, "unary_not_is_boolean")
     REQUIRE_EQ("boolean", toString(requireType("c")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "disallow_string_and_types_without_metatables_from_arithmetic_binary_ops")
+TEST_CASE_FIXTURE(BuiltinsFixture, "disallow_string_and_types_without_metatables_from_arithmetic_binary_ops")
 {
     CheckResult result = check(R"(
         --!strict
@@ -573,7 +573,7 @@ TEST_CASE_FIXTURE(Fixture, "strict_binary_op_where_lhs_unknown")
     CHECK_EQ("Unknown type used in + operation; consider adding a type annotation to 'a'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "and_binexps_dont_unify")
+TEST_CASE_FIXTURE(BuiltinsFixture, "and_binexps_dont_unify")
 {
     CheckResult result = check(R"(
     --!strict
@@ -628,7 +628,7 @@ TEST_CASE_FIXTURE(Fixture, "cli_38355_recursive_union")
     CHECK_EQ("Type contains a self-recursive construct that cannot be resolved", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "UnknownGlobalCompoundAssign")
+TEST_CASE_FIXTURE(BuiltinsFixture, "UnknownGlobalCompoundAssign")
 {
     // In non-strict mode, global definition is still allowed
     {
@@ -755,8 +755,6 @@ TEST_CASE_FIXTURE(Fixture, "refine_and_or")
 
 TEST_CASE_FIXTURE(Fixture, "infer_any_in_all_modes_when_lhs_is_unknown")
 {
-    ScopedFastFlag sff{"LuauDecoupleOperatorInferenceFromUnifiedTypeInference", true};
-
     CheckResult result = check(Mode::Strict, R"(
         local function f(x, y)
             return x + y
@@ -779,4 +777,47 @@ TEST_CASE_FIXTURE(Fixture, "infer_any_in_all_modes_when_lhs_is_unknown")
     // the case right now, though.
 }
 
+TEST_CASE_FIXTURE(BuiltinsFixture, "equality_operations_succeed_if_any_union_branch_succeeds")
+{
+    ScopedFastFlag sff("LuauSuccessTypingForEqualityOperations", true);
+
+    CheckResult result = check(R"(
+        local mm = {}
+        type Foo = typeof(setmetatable({}, mm))
+        local x: Foo
+        local y: Foo?
+
+        local v1 = x == y
+        local v2 = y == x
+        local v3 = x ~= y
+        local v4 = y ~= x
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CheckResult result2 = check(R"(
+        local mm1 = {
+            x = "foo",
+        }
+
+        local mm2 = {
+            y = "bar",
+        }
+
+        type Foo = typeof(setmetatable({}, mm1))
+        type Bar = typeof(setmetatable({}, mm2))
+
+        local x1: Foo
+        local x2: Foo?
+        local y1: Bar
+        local y2: Bar?
+
+        local v1 = x1 == y1
+        local v2 = x2 == y2
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result2);
+    CHECK(toString(result2.errors[0]) == "Types Foo and Bar cannot be compared with == because they do not have the same metatable");
+}
+
 TEST_SUITE_END();

tests/TypeInfer.provisional.test.cpp

@@ -53,7 +53,7 @@ TEST_CASE_FIXTURE(Fixture, "typeguard_inference_incomplete")
     CHECK_EQ(expected, decorateWithTypes(code));
 }
 
-TEST_CASE_FIXTURE(Fixture, "xpcall_returns_what_f_returns")
+TEST_CASE_FIXTURE(BuiltinsFixture, "xpcall_returns_what_f_returns")
 {
     const std::string code = R"(
         local a, b, c = xpcall(function() return 1, "foo" end, function() return "foo", 1 end)
@@ -105,7 +105,7 @@ TEST_CASE_FIXTURE(Fixture, "it_should_be_agnostic_of_actual_size")
 
 // Ideally setmetatable's second argument would be an optional free table.
 // For now, infer it as just a free table.
-TEST_CASE_FIXTURE(Fixture, "setmetatable_constrains_free_type_into_free_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "setmetatable_constrains_free_type_into_free_table")
 {
     CheckResult result = check(R"(
         local a = {}
@@ -146,7 +146,7 @@ TEST_CASE_FIXTURE(Fixture, "while_body_are_also_refined")
 // Originally from TypeInfer.test.cpp.
 // I dont think type checking the metamethod at every site of == is the correct thing to do.
 // We should be type checking the metamethod at the call site of setmetatable.
-TEST_CASE_FIXTURE(Fixture, "error_on_eq_metamethod_returning_a_type_other_than_boolean")
+TEST_CASE_FIXTURE(BuiltinsFixture, "error_on_eq_metamethod_returning_a_type_other_than_boolean")
 {
     CheckResult result = check(R"(
         local tab = {a = 1}
@@ -428,7 +428,7 @@ TEST_CASE_FIXTURE(Fixture, "pcall_returns_at_least_two_value_but_function_return
 }
 
 // Belongs in TypeInfer.builtins.test.cpp.
-TEST_CASE_FIXTURE(Fixture, "choose_the_right_overload_for_pcall")
+TEST_CASE_FIXTURE(BuiltinsFixture, "choose_the_right_overload_for_pcall")
 {
     CheckResult result = check(R"(
         local function f(): number
@@ -449,7 +449,7 @@ TEST_CASE_FIXTURE(Fixture, "choose_the_right_overload_for_pcall")
 }
 
 // Belongs in TypeInfer.builtins.test.cpp.
-TEST_CASE_FIXTURE(Fixture, "function_returns_many_things_but_first_of_it_is_forgotten")
+TEST_CASE_FIXTURE(BuiltinsFixture, "function_returns_many_things_but_first_of_it_is_forgotten")
 {
     CheckResult result = check(R"(
         local function f(): (number, string, boolean)

tests/TypeInfer.refinements.test.cpp

@@ -240,7 +240,7 @@ TEST_CASE_FIXTURE(Fixture, "typeguard_in_if_condition_position")
     CHECK_EQ("number", toString(requireTypeAtPosition({3, 26})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "typeguard_in_assert_position")
+TEST_CASE_FIXTURE(BuiltinsFixture, "typeguard_in_assert_position")
 {
     CheckResult result = check(R"(
         local a
@@ -300,7 +300,7 @@ TEST_CASE_FIXTURE(Fixture, "call_a_more_specific_function_using_typeguard")
     CHECK_EQ("Type 'string' could not be converted into 'number'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "impossible_type_narrow_is_not_an_error")
+TEST_CASE_FIXTURE(BuiltinsFixture, "impossible_type_narrow_is_not_an_error")
 {
     // This unit test serves as a reminder to not implement this warning until Luau is intelligent enough.
     // For instance, getting a value out of the indexer and checking whether the value exists is not an error.
@@ -333,7 +333,7 @@ TEST_CASE_FIXTURE(Fixture, "truthy_constraint_on_properties")
     CHECK_EQ("number?", toString(requireType("bar")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "index_on_a_refined_property")
+TEST_CASE_FIXTURE(BuiltinsFixture, "index_on_a_refined_property")
 {
     CheckResult result = check(R"(
         local t: {x: {y: string}?} = {x = {y = "hello!"}}
@@ -346,7 +346,7 @@ TEST_CASE_FIXTURE(Fixture, "index_on_a_refined_property")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_non_binary_expressions_actually_resolve_constraints")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_non_binary_expressions_actually_resolve_constraints")
 {
     CheckResult result = check(R"(
         local foo: string? = "hello"
@@ -730,7 +730,7 @@ TEST_CASE_FIXTURE(Fixture, "type_guard_can_filter_for_overloaded_function")
     CHECK_EQ("nil", toString(requireTypeAtPosition({6, 28})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_guard_warns_on_no_overlapping_types_only_when_sense_is_true")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_guard_warns_on_no_overlapping_types_only_when_sense_is_true")
 {
     CheckResult result = check(R"(
         local function f(t: {x: number})
@@ -846,7 +846,7 @@ TEST_CASE_FIXTURE(Fixture, "not_t_or_some_prop_of_t")
     CHECK_EQ("{| x: boolean |}?", toString(requireTypeAtPosition({3, 28})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "assert_a_to_be_truthy_then_assert_a_to_be_number")
+TEST_CASE_FIXTURE(BuiltinsFixture, "assert_a_to_be_truthy_then_assert_a_to_be_number")
 {
     CheckResult result = check(R"(
         local a: (number | string)?
@@ -862,7 +862,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_a_to_be_truthy_then_assert_a_to_be_number")
     CHECK_EQ("number", toString(requireTypeAtPosition({5, 18})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "merge_should_be_fully_agnostic_of_hashmap_ordering")
+TEST_CASE_FIXTURE(BuiltinsFixture, "merge_should_be_fully_agnostic_of_hashmap_ordering")
 {
     // This bug came up because there was a mistake in Luau::merge where zipping on two maps would produce the wrong merged result.
     CheckResult result = check(R"(
@@ -899,7 +899,7 @@ TEST_CASE_FIXTURE(Fixture, "refine_the_correct_types_opposite_of_when_a_is_not_n
     CHECK_EQ("number | string", toString(requireTypeAtPosition({5, 28})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "is_truthy_constraint_ifelse_expression")
+TEST_CASE_FIXTURE(BuiltinsFixture, "is_truthy_constraint_ifelse_expression")
 {
     CheckResult result = check(R"(
         function f(v:string?)
@@ -913,7 +913,7 @@ TEST_CASE_FIXTURE(Fixture, "is_truthy_constraint_ifelse_expression")
     CHECK_EQ("nil", toString(requireTypeAtPosition({2, 45})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "invert_is_truthy_constraint_ifelse_expression")
+TEST_CASE_FIXTURE(BuiltinsFixture, "invert_is_truthy_constraint_ifelse_expression")
 {
     CheckResult result = check(R"(
         function f(v:string?)
@@ -945,7 +945,7 @@ TEST_CASE_FIXTURE(Fixture, "type_comparison_ifelse_expression")
     CHECK_EQ("any", toString(requireTypeAtPosition({6, 66})));
 }
 
-TEST_CASE_FIXTURE(Fixture, "correctly_lookup_a_shadowed_local_that_which_was_previously_refined")
+TEST_CASE_FIXTURE(BuiltinsFixture, "correctly_lookup_a_shadowed_local_that_which_was_previously_refined")
 {
     CheckResult result = check(R"(
         local foo: string? = "hi"

tests/TypeInfer.singletons.test.cpp

@@ -415,7 +415,7 @@ TEST_CASE_FIXTURE(Fixture, "widening_happens_almost_everywhere_except_for_tables
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_insert_with_a_singleton_argument")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_with_a_singleton_argument")
 {
     ScopedFastFlag sff[]{
         {"LuauWidenIfSupertypeIsFree2", true},

tests/TypeInfer.tables.test.cpp

@@ -201,7 +201,7 @@ TEST_CASE_FIXTURE(Fixture, "used_dot_instead_of_colon")
     REQUIRE(it != result.errors.end());
 }
 
-TEST_CASE_FIXTURE(Fixture, "used_colon_correctly")
+TEST_CASE_FIXTURE(BuiltinsFixture, "used_colon_correctly")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -883,7 +883,7 @@ TEST_CASE_FIXTURE(Fixture, "assigning_to_an_unsealed_table_with_string_literal_s
     CHECK_EQ(*typeChecker.stringType, *propertyA);
 }
 
-TEST_CASE_FIXTURE(Fixture, "oop_indexer_works")
+TEST_CASE_FIXTURE(BuiltinsFixture, "oop_indexer_works")
 {
     CheckResult result = check(R"(
         local clazz = {}
@@ -906,7 +906,7 @@ TEST_CASE_FIXTURE(Fixture, "oop_indexer_works")
     CHECK_EQ(*typeChecker.stringType, *requireType("words"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "indexer_table")
+TEST_CASE_FIXTURE(BuiltinsFixture, "indexer_table")
 {
     CheckResult result = check(R"(
         local clazz = {a="hello"}
@@ -919,7 +919,7 @@ TEST_CASE_FIXTURE(Fixture, "indexer_table")
     CHECK_EQ(*typeChecker.stringType, *requireType("b"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "indexer_fn")
+TEST_CASE_FIXTURE(BuiltinsFixture, "indexer_fn")
 {
     CheckResult result = check(R"(
         local instanace = setmetatable({}, {__index=function() return 10 end})
@@ -930,7 +930,7 @@ TEST_CASE_FIXTURE(Fixture, "indexer_fn")
     CHECK_EQ(*typeChecker.numberType, *requireType("b"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "meta_add")
+TEST_CASE_FIXTURE(BuiltinsFixture, "meta_add")
 {
     // Note: meta_add_inferred and this unit test are currently the same exact thing.
     // We'll want to change this one in particular when we add real syntax for metatables.
@@ -947,7 +947,7 @@ TEST_CASE_FIXTURE(Fixture, "meta_add")
     CHECK_EQ(follow(requireType("a")), follow(requireType("c")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "meta_add_inferred")
+TEST_CASE_FIXTURE(BuiltinsFixture, "meta_add_inferred")
 {
     CheckResult result = check(R"(
         local a = {}
@@ -960,7 +960,7 @@ TEST_CASE_FIXTURE(Fixture, "meta_add_inferred")
     CHECK_EQ(*requireType("a"), *requireType("c"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "meta_add_both_ways")
+TEST_CASE_FIXTURE(BuiltinsFixture, "meta_add_both_ways")
 {
     CheckResult result = check(R"(
         type VectorMt = { __add: (Vector, number) -> Vector }
@@ -980,7 +980,7 @@ TEST_CASE_FIXTURE(Fixture, "meta_add_both_ways")
 
 // This test exposed a bug where we let go of the "seen" stack while unifying table types
 // As a result, type inference crashed with a stack overflow.
-TEST_CASE_FIXTURE(Fixture, "unification_of_unions_in_a_self_referential_type")
+TEST_CASE_FIXTURE(BuiltinsFixture, "unification_of_unions_in_a_self_referential_type")
 {
     CheckResult result = check(R"(
         type A = {}
@@ -1009,7 +1009,7 @@ TEST_CASE_FIXTURE(Fixture, "unification_of_unions_in_a_self_referential_type")
     CHECK_EQ(bmtv->metatable, requireType("bmt"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "oop_polymorphic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "oop_polymorphic")
 {
     CheckResult result = check(R"(
         local animal = {}
@@ -1060,7 +1060,7 @@ TEST_CASE_FIXTURE(Fixture, "user_defined_table_types_are_named")
     CHECK_EQ("Vector3", toString(requireType("v")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "result_is_always_any_if_lhs_is_any")
+TEST_CASE_FIXTURE(BuiltinsFixture, "result_is_always_any_if_lhs_is_any")
 {
     CheckResult result = check(R"(
         type Vector3MT = {
@@ -1133,7 +1133,7 @@ TEST_CASE_FIXTURE(Fixture, "nice_error_when_trying_to_fetch_property_of_boolean"
     CHECK_EQ("Type 'boolean' does not have key 'some_prop'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "defining_a_method_for_a_builtin_sealed_table_must_fail")
+TEST_CASE_FIXTURE(BuiltinsFixture, "defining_a_method_for_a_builtin_sealed_table_must_fail")
 {
     CheckResult result = check(R"(
         function string.m() end
@@ -1142,7 +1142,7 @@ TEST_CASE_FIXTURE(Fixture, "defining_a_method_for_a_builtin_sealed_table_must_fa
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "defining_a_self_method_for_a_builtin_sealed_table_must_fail")
+TEST_CASE_FIXTURE(BuiltinsFixture, "defining_a_self_method_for_a_builtin_sealed_table_must_fail")
 {
     CheckResult result = check(R"(
         function string:m() end
@@ -1261,7 +1261,7 @@ TEST_CASE_FIXTURE(Fixture, "found_like_key_in_table_function_call")
     CHECK_EQ(toString(te), "Key 'fOo' not found in table 't'.  Did you mean 'Foo'?");
 }
 
-TEST_CASE_FIXTURE(Fixture, "found_like_key_in_table_property_access")
+TEST_CASE_FIXTURE(BuiltinsFixture, "found_like_key_in_table_property_access")
 {
     CheckResult result = check(R"(
         local t = {X = 1}
@@ -1286,7 +1286,7 @@ TEST_CASE_FIXTURE(Fixture, "found_like_key_in_table_property_access")
     CHECK_EQ(toString(te), "Key 'x' not found in table 't'.  Did you mean 'X'?");
 }
 
-TEST_CASE_FIXTURE(Fixture, "found_multiple_like_keys")
+TEST_CASE_FIXTURE(BuiltinsFixture, "found_multiple_like_keys")
 {
     CheckResult result = check(R"(
         local t = {Foo = 1, foO = 2}
@@ -1312,7 +1312,7 @@ TEST_CASE_FIXTURE(Fixture, "found_multiple_like_keys")
     CHECK_EQ(toString(te), "Key 'foo' not found in table 't'.  Did you mean one of 'Foo', 'foO'?");
 }
 
-TEST_CASE_FIXTURE(Fixture, "dont_suggest_exact_match_keys")
+TEST_CASE_FIXTURE(BuiltinsFixture, "dont_suggest_exact_match_keys")
 {
     CheckResult result = check(R"(
         local t = {}
@@ -1339,7 +1339,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_suggest_exact_match_keys")
     CHECK_EQ(toString(te), "Key 'Foo' not found in table 't'.  Did you mean 'foO'?");
 }
 
-TEST_CASE_FIXTURE(Fixture, "getmetatable_returns_pointer_to_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "getmetatable_returns_pointer_to_metatable")
 {
     CheckResult result = check(R"(
         local t = {x = 1}
@@ -1352,7 +1352,7 @@ TEST_CASE_FIXTURE(Fixture, "getmetatable_returns_pointer_to_metatable")
     CHECK_EQ(*requireType("mt"), *requireType("returnedMT"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "metatable_mismatch_should_fail")
+TEST_CASE_FIXTURE(BuiltinsFixture, "metatable_mismatch_should_fail")
 {
     CheckResult result = check(R"(
         local t1 = {x = 1}
@@ -1374,7 +1374,7 @@ TEST_CASE_FIXTURE(Fixture, "metatable_mismatch_should_fail")
     CHECK_EQ(*tm->givenType, *requireType("t2"));
 }
 
-TEST_CASE_FIXTURE(Fixture, "property_lookup_through_tabletypevar_metatable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "property_lookup_through_tabletypevar_metatable")
 {
     CheckResult result = check(R"(
         local t = {x = 1}
@@ -1393,7 +1393,7 @@ TEST_CASE_FIXTURE(Fixture, "property_lookup_through_tabletypevar_metatable")
     CHECK_EQ(up->key, "z");
 }
 
-TEST_CASE_FIXTURE(Fixture, "missing_metatable_for_sealed_tables_do_not_get_inferred")
+TEST_CASE_FIXTURE(BuiltinsFixture, "missing_metatable_for_sealed_tables_do_not_get_inferred")
 {
     CheckResult result = check(R"(
         local t = {x = 1}
@@ -1742,7 +1742,7 @@ TEST_CASE_FIXTURE(Fixture, "hide_table_error_properties")
     CHECK_EQ("Cannot add property 'b' to table '{| x: number |}'", toString(result.errors[1]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "builtin_table_names")
+TEST_CASE_FIXTURE(BuiltinsFixture, "builtin_table_names")
 {
     CheckResult result = check(R"(
         os.h = 2
@@ -1755,7 +1755,7 @@ TEST_CASE_FIXTURE(Fixture, "builtin_table_names")
     CHECK_EQ("Cannot add property 'k' to table 'string'", toString(result.errors[1]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "persistent_sealed_table_is_immutable")
+TEST_CASE_FIXTURE(BuiltinsFixture, "persistent_sealed_table_is_immutable")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -1858,7 +1858,7 @@ local foos: {Foo} = {
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "quantifying_a_bound_var_works")
+TEST_CASE_FIXTURE(BuiltinsFixture, "quantifying_a_bound_var_works")
 {
     CheckResult result = check(R"(
         local clazz = {}
@@ -1983,7 +1983,7 @@ TEST_CASE_FIXTURE(Fixture, "invariant_table_properties_means_instantiating_table
     LUAU_REQUIRE_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_insert_should_cope_with_optional_properties_in_nonstrict")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_should_cope_with_optional_properties_in_nonstrict")
 {
     CheckResult result = check(R"(
         --!nonstrict
@@ -1996,7 +1996,7 @@ TEST_CASE_FIXTURE(Fixture, "table_insert_should_cope_with_optional_properties_in
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_insert_should_cope_with_optional_properties_in_strict")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_insert_should_cope_with_optional_properties_in_strict")
 {
     ScopedFastFlag sff{"LuauTableSubtypingVariance2", true};
 
@@ -2052,7 +2052,7 @@ caused by:
   Property 'y' is not compatible. Type 'number' could not be converted into 'string')");
 }
 
-TEST_CASE_FIXTURE(Fixture, "error_detailed_metatable_prop")
+TEST_CASE_FIXTURE(BuiltinsFixture, "error_detailed_metatable_prop")
 {
     ScopedFastFlag sff[]{
         {"LuauTableSubtypingVariance2", true},
@@ -2183,7 +2183,7 @@ a.p = { x = 9 }
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "recursive_metatable_type_call")
+TEST_CASE_FIXTURE(BuiltinsFixture, "recursive_metatable_type_call")
 {
     ScopedFastFlag sff[]{
         {"LuauUnsealedTableLiteral", true},
@@ -2277,7 +2277,7 @@ local y = #x
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "dont_hang_when_trying_to_look_up_in_cyclic_metatable_index")
+TEST_CASE_FIXTURE(BuiltinsFixture, "dont_hang_when_trying_to_look_up_in_cyclic_metatable_index")
 {
     ScopedFastFlag sff{"LuauTerminateCyclicMetatableIndexLookup", true};
 
@@ -2296,7 +2296,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_hang_when_trying_to_look_up_in_cyclic_metatable
     CHECK_EQ("Type 't' does not have key 'p'", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "give_up_after_one_metatable_index_look_up")
+TEST_CASE_FIXTURE(BuiltinsFixture, "give_up_after_one_metatable_index_look_up")
 {
     CheckResult result = check(R"(
         local data = { x = 5 }
@@ -2478,7 +2478,7 @@ TEST_CASE_FIXTURE(Fixture, "free_rhs_table_can_also_be_bound")
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_unifies_into_map")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_unifies_into_map")
 {
     CheckResult result = check(R"(
         local Instance: any
@@ -2564,7 +2564,7 @@ TEST_CASE_FIXTURE(Fixture, "generalize_table_argument")
  * the generalization process), then it loses the knowledge that its metatable will have an :incr()
  * method.
  */
-TEST_CASE_FIXTURE(Fixture, "dont_quantify_table_that_belongs_to_outer_scope")
+TEST_CASE_FIXTURE(BuiltinsFixture, "dont_quantify_table_that_belongs_to_outer_scope")
 {
     CheckResult result = check(R"(
         local Counter = {}
@@ -2606,7 +2606,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_quantify_table_that_belongs_to_outer_scope")
 }
 
 // TODO: CLI-39624
-TEST_CASE_FIXTURE(Fixture, "instantiate_tables_at_scope_level")
+TEST_CASE_FIXTURE(BuiltinsFixture, "instantiate_tables_at_scope_level")
 {
     CheckResult result = check(R"(
         --!strict
@@ -2690,7 +2690,7 @@ TEST_CASE_FIXTURE(Fixture, "dont_crash_when_setmetatable_does_not_produce_a_meta
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "instantiate_table_cloning")
+TEST_CASE_FIXTURE(BuiltinsFixture, "instantiate_table_cloning")
 {
     CheckResult result = check(R"(
 --!nonstrict
@@ -2711,7 +2711,7 @@ type t0<t32> = any
     CHECK(ttv->instantiatedTypeParams.empty());
 }
 
-TEST_CASE_FIXTURE(Fixture, "instantiate_table_cloning_2")
+TEST_CASE_FIXTURE(BuiltinsFixture, "instantiate_table_cloning_2")
 {
     ScopedFastFlag sff{"LuauOnlyMutateInstantiatedTables", true};
 
@@ -2767,7 +2767,7 @@ local baz = foo[bar]
     CHECK_EQ(result.errors[0].location, Location{Position{3, 16}, Position{3, 19}});
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_simple_call")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_simple_call")
 {
     CheckResult result = check(R"(
 local a = setmetatable({ x = 2 }, {
@@ -2783,7 +2783,7 @@ local c = a(2) -- too many arguments
     CHECK_EQ("Argument count mismatch. Function expects 1 argument, but 2 are specified", toString(result.errors[0]));
 }
 
-TEST_CASE_FIXTURE(Fixture, "access_index_metamethod_that_returns_variadic")
+TEST_CASE_FIXTURE(BuiltinsFixture, "access_index_metamethod_that_returns_variadic")
 {
     CheckResult result = check(R"(
         type Foo = {x: string}
@@ -2878,7 +2878,7 @@ TEST_CASE_FIXTURE(Fixture, "pairs_parameters_are_not_unsealed_tables")
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_function_check_use_after_free")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_function_check_use_after_free")
 {
     CheckResult result = check(R"(
 local t = {}
@@ -2916,7 +2916,7 @@ TEST_CASE_FIXTURE(Fixture, "inferred_properties_of_a_table_should_start_with_the
 }
 
 // The real bug here was that we weren't always uncondionally typechecking a trailing return statement last.
-TEST_CASE_FIXTURE(Fixture, "dont_leak_free_table_props")
+TEST_CASE_FIXTURE(BuiltinsFixture, "dont_leak_free_table_props")
 {
     CheckResult result = check(R"(
         local function a(state)

tests/TypeInfer.test.cpp

@@ -161,7 +161,7 @@ TEST_CASE_FIXTURE(Fixture, "unify_nearly_identical_recursive_types")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "warn_on_lowercase_parent_property")
+TEST_CASE_FIXTURE(BuiltinsFixture, "warn_on_lowercase_parent_property")
 {
     CheckResult result = check(R"(
         local M = require(script.parent.DoesNotMatter)
@@ -175,7 +175,7 @@ TEST_CASE_FIXTURE(Fixture, "warn_on_lowercase_parent_property")
     REQUIRE_EQ("parent", ed->symbol);
 }
 
-TEST_CASE_FIXTURE(Fixture, "weird_case")
+TEST_CASE_FIXTURE(BuiltinsFixture, "weird_case")
 {
     CheckResult result = check(R"(
         local function f() return 4 end
@@ -419,7 +419,7 @@ TEST_CASE_FIXTURE(Fixture, "globals_everywhere")
     CHECK_EQ("any", toString(requireType("bar")));
 }
 
-TEST_CASE_FIXTURE(Fixture, "correctly_scope_locals_do")
+TEST_CASE_FIXTURE(BuiltinsFixture, "correctly_scope_locals_do")
 {
     CheckResult result = check(R"(
         do
@@ -534,7 +534,7 @@ TEST_CASE_FIXTURE(Fixture, "tc_after_error_recovery_no_assert")
     LUAU_REQUIRE_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "tc_after_error_recovery_no_replacement_name_in_error")
+TEST_CASE_FIXTURE(BuiltinsFixture, "tc_after_error_recovery_no_replacement_name_in_error")
 {
     {
         CheckResult result = check(R"(
@@ -587,7 +587,7 @@ TEST_CASE_FIXTURE(Fixture, "tc_after_error_recovery_no_replacement_name_in_error
     }
 }
 
-TEST_CASE_FIXTURE(Fixture, "index_expr_should_be_checked")
+TEST_CASE_FIXTURE(BuiltinsFixture, "index_expr_should_be_checked")
 {
     CheckResult result = check(R"(
         local foo: any
@@ -768,7 +768,7 @@ b, c = {2, "s"}, {"b", 4}
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "infer_assignment_value_types_mutable_lval")
+TEST_CASE_FIXTURE(BuiltinsFixture, "infer_assignment_value_types_mutable_lval")
 {
     CheckResult result = check(R"(
 local a = {}
@@ -836,7 +836,7 @@ local a: number? = if true then 1 else nil
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "tc_if_else_expressions_expected_type_3")
+TEST_CASE_FIXTURE(BuiltinsFixture, "tc_if_else_expressions_expected_type_3")
 {
     CheckResult result = check(R"(
 local function times<T>(n: any, f: () -> T)
@@ -907,7 +907,7 @@ TEST_CASE_FIXTURE(Fixture, "fuzzer_found_this")
     )");
 }
 
-TEST_CASE_FIXTURE(Fixture, "recursive_metatable_crash")
+TEST_CASE_FIXTURE(BuiltinsFixture, "recursive_metatable_crash")
 {
     CheckResult result = check(R"(
 local function getIt()
@@ -1041,7 +1041,6 @@ TEST_CASE_FIXTURE(Fixture, "follow_on_new_types_in_substitution")
 TEST_CASE_FIXTURE(Fixture, "do_not_bind_a_free_table_to_a_union_containing_that_table")
 {
     ScopedFastFlag flag[] = {
-        {"LuauStatFunctionSimplify4", true},
         {"LuauLowerBoundsCalculation", true},
         {"LuauDifferentOrderOfUnificationDoesntMatter2", true},
     };

tests/TypeInfer.tryUnify.test.cpp

@@ -196,7 +196,7 @@ TEST_CASE_FIXTURE(TryUnifyFixture, "variadics_should_use_reversed_properly")
     CHECK_EQ(toString(tm->wantedType), "string");
 }
 
-TEST_CASE_FIXTURE(TryUnifyFixture, "cli_41095_concat_log_in_sealed_table_unification")
+TEST_CASE_FIXTURE(BuiltinsFixture, "cli_41095_concat_log_in_sealed_table_unification")
 {
     CheckResult result = check(R"(
         --!strict

tests/TypeInfer.typePacks.cpp

@@ -339,7 +339,7 @@ local c: Packed<string, number, boolean>
     CHECK_EQ(toString(ttvC->instantiatedTypePackParams[0], {true}), "number, boolean");
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_alias_type_packs_import")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_alias_type_packs_import")
 {
     fileResolver.source["game/A"] = R"(
 export type Packed<T, U...> = { a: T, b: (U...) -> () }
@@ -369,7 +369,7 @@ local d: { a: typeof(c) }
     CHECK_EQ(toString(requireType("d")), "{| a: Packed<string, number, boolean> |}");
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_pack_type_parameters")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_pack_type_parameters")
 {
     fileResolver.source["game/A"] = R"(
 export type Packed<T, U...> = { a: T, b: (U...) -> () }
@@ -784,7 +784,7 @@ local a: Y<...number>
     LUAU_REQUIRE_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "type_alias_default_export")
+TEST_CASE_FIXTURE(BuiltinsFixture, "type_alias_default_export")
 {
     fileResolver.source["Module/Types"] = R"(
 export type A<T, U = string> = { a: T, b: U }

tests/TypeInfer.unionTypes.test.cpp

@@ -104,7 +104,7 @@ TEST_CASE_FIXTURE(Fixture, "optional_arguments_table2")
     REQUIRE(!result.errors.empty());
 }
 
-TEST_CASE_FIXTURE(Fixture, "error_takes_optional_arguments")
+TEST_CASE_FIXTURE(BuiltinsFixture, "error_takes_optional_arguments")
 {
     CheckResult result = check(R"(
         error("message")
@@ -517,10 +517,8 @@ TEST_CASE_FIXTURE(Fixture, "dont_allow_cyclic_unions_to_be_inferred")
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
-TEST_CASE_FIXTURE(Fixture, "table_union_write_indirect")
+TEST_CASE_FIXTURE(BuiltinsFixture, "table_union_write_indirect")
 {
-    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
-
     CheckResult result = check(R"(
         type A = { x: number, y: (number) -> string } | { z: number, y: (number) -> string }