Sync to upstream/release/647 (#1469)

# General Updates
Fix an old solver crash that occurs in the presence of cyclic
`requires()`

## New Solver
- Improvements to Luau user-defined type function library
- Avoid asserting on unexpected metatable types
- Properties in user defined type functions should have a consistent
iteration order - in this case it is insertion ordering

# Runtime
- Track VM allocations for telemetry

---
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: James McNellis <jmcnellis@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

---------

Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Junseo Yoo <jyoo@roblox.com>

Analysis/include/Luau/TypeFunctionRuntime.h

@@ -6,7 +6,7 @@
 
 #include <optional>
 #include <string>
-#include <unordered_map>
+#include <map>
 #include <vector>
 
 using lua_State = struct lua_State;
@@ -182,7 +182,7 @@ struct TypeFunctionProperty
 struct TypeFunctionTableType
 {
     using Name = std::string;
-    using Props = std::unordered_map<Name, TypeFunctionProperty>;
+    using Props = std::map<Name, TypeFunctionProperty>;
 
     Props props;
 
@@ -195,7 +195,7 @@ struct TypeFunctionTableType
 struct TypeFunctionClassType
 {
     using Name = std::string;
-    using Props = std::unordered_map<Name, TypeFunctionProperty>;
+    using Props = std::map<Name, TypeFunctionProperty>;
 
     Props props;
 
@@ -260,6 +260,7 @@ bool isTypeUserData(lua_State* L, int idx);
 TypeFunctionTypeId getTypeUserData(lua_State* L, int idx);
 std::optional<TypeFunctionTypeId> optionalTypeUserData(lua_State* L, int idx);
 
+void registerTypesLibrary(lua_State* L);
 void registerTypeUserData(lua_State* L);
 
 void setTypeFunctionEnvironment(lua_State* L);

Analysis/src/BuiltinDefinitions.cpp

@@ -26,7 +26,6 @@
  */
 
 LUAU_FASTFLAG(LuauSolverV2);
-LUAU_FASTFLAGVARIABLE(LuauDCRMagicFunctionTypeChecker, false);
 
 namespace Luau
 {
@@ -931,8 +930,7 @@ TypeId makeStringMetatable(NotNull<BuiltinTypes> builtinTypes)
     formatFTV.isCheckedFunction = true;
     const TypeId formatFn = arena->addType(formatFTV);
     attachDcrMagicFunction(formatFn, dcrMagicFunctionFormat);
-    if (FFlag::LuauDCRMagicFunctionTypeChecker)
-        attachDcrMagicFunctionTypeCheck(formatFn, dcrMagicFunctionTypeCheckFormat);
+    attachDcrMagicFunctionTypeCheck(formatFn, dcrMagicFunctionTypeCheckFormat);
 
 
     const TypeId stringToStringType = makeFunction(*arena, std::nullopt, {}, {}, {stringType}, {}, {stringType}, /* checked */ true);

Analysis/src/ConstraintSolver.cpp

@@ -31,10 +31,7 @@ LUAU_FASTFLAGVARIABLE(DebugLuauLogSolver, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverIncludeDependencies, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauLogBindings, false)
 LUAU_FASTINTVARIABLE(LuauSolverRecursionLimit, 500)
-
-// The default value here is 643 because the first release in which this was implemented is 644,
-// and actively we want new changes to be off by default until they're enabled consciously.
-LUAU_DYNAMIC_FASTINTVARIABLE(LuauTypeSolverRelease, 643)
+LUAU_DYNAMIC_FASTINT(LuauTypeSolverRelease)
 
 namespace Luau
 {

Analysis/src/Differ.cpp

@@ -13,6 +13,7 @@
 
 namespace Luau
 {
+
 std::string DiffPathNode::toString() const
 {
     switch (kind)
@@ -944,12 +945,14 @@ std::vector<std::pair<TypeId, TypeId>>::const_reverse_iterator DifferEnvironment
     return visitingStack.crend();
 }
 
+
 DifferResult diff(TypeId ty1, TypeId ty2)
 {
     DifferEnvironment differEnv{ty1, ty2, std::nullopt, std::nullopt};
     return diffUsingEnv(differEnv, ty1, ty2);
 }
 
+
 DifferResult diffWithSymbols(TypeId ty1, TypeId ty2, std::optional<std::string> symbol1, std::optional<std::string> symbol2)
 {
     DifferEnvironment differEnv{ty1, ty2, symbol1, symbol2};

Analysis/src/Frontend.cpp

@@ -44,9 +44,9 @@ LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJsonFile, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauForbidInternalTypes, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauForceStrictMode, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauForceNonStrictMode, false)
-LUAU_FASTFLAGVARIABLE(LuauSourceModuleUpdatedWithSelectedMode, false)
 LUAU_FASTFLAGVARIABLE(LuauUserDefinedTypeFunctionNoEvaluation, false)
 LUAU_DYNAMIC_FASTFLAGVARIABLE(LuauRunCustomModuleChecks, false)
+LUAU_FASTFLAGVARIABLE(LuauMoreThoroughCycleDetection, false)
 
 LUAU_FASTFLAG(StudioReportLuauAny2)
 
@@ -883,14 +883,18 @@ void Frontend::addBuildQueueItems(
         data.environmentScope = getModuleEnvironment(*sourceModule, data.config, frontendOptions.forAutocomplete);
         data.recordJsonLog = FFlag::DebugLuauLogSolverToJson;
 
-        Mode mode = sourceModule->mode.value_or(data.config.mode);
+        const Mode mode = sourceModule->mode.value_or(data.config.mode);
 
-        // in NoCheck mode we only need to compute the value of .cyclic for typeck
         // in the future we could replace toposort with an algorithm that can flag cyclic nodes by itself
         // however, for now getRequireCycles isn't expensive in practice on the cases we care about, and long term
         // all correct programs must be acyclic so this code triggers rarely
         if (cycleDetected)
-            data.requireCycles = getRequireCycles(fileResolver, sourceNodes, sourceNode.get(), mode == Mode::NoCheck);
+        {
+            if (FFlag::LuauMoreThoroughCycleDetection)
+                data.requireCycles = getRequireCycles(fileResolver, sourceNodes, sourceNode.get(), false);
+            else
+                data.requireCycles = getRequireCycles(fileResolver, sourceNodes, sourceNode.get(), mode == Mode::NoCheck);
+        }
 
         data.options = frontendOptions;
 
@@ -922,8 +926,7 @@ void Frontend::checkBuildQueueItem(BuildQueueItem& item)
     else
         mode = sourceModule.mode.value_or(config.mode);
 
-    if (FFlag::LuauSourceModuleUpdatedWithSelectedMode)
-        item.sourceModule->mode = {mode};
+    item.sourceModule->mode = {mode};
     ScopePtr environmentScope = item.environmentScope;
     double timestamp = getTimestamp();
     const std::vector<RequireCycle>& requireCycles = item.requireCycles;

Analysis/src/Normalize.cpp

@@ -16,25 +16,13 @@
 #include "Luau/Unifier.h"
 
 LUAU_FASTFLAGVARIABLE(DebugLuauCheckNormalizeInvariant, false)
-LUAU_FASTFLAGVARIABLE(LuauFixReduceStackPressure, false);
-LUAU_FASTFLAGVARIABLE(LuauFixCyclicTablesBlowingStack, false);
 
 LUAU_FASTINTVARIABLE(LuauNormalizeCacheLimit, 100000);
 LUAU_FASTFLAG(LuauSolverV2);
 
 LUAU_FASTFLAGVARIABLE(LuauUseNormalizeIntersectionLimit, false)
 LUAU_FASTINTVARIABLE(LuauNormalizeIntersectionLimit, 200)
 
-static bool fixReduceStackPressure()
-{
-    return FFlag::LuauFixReduceStackPressure || FFlag::LuauSolverV2;
-}
-
-static bool fixCyclicTablesBlowingStack()
-{
-    return FFlag::LuauFixCyclicTablesBlowingStack || FFlag::LuauSolverV2;
-}
-
 namespace Luau
 {
 
@@ -2583,43 +2571,29 @@ std::optional<TypeId> Normalizer::intersectionOfTables(TypeId here, TypeId there
                     if (tprop.readTy.has_value())
                     {
                         // if the intersection of the read types of a property is uninhabited, the whole table is `never`.
-                        if (fixReduceStackPressure())
+                        // We've seen these table prop elements before and we're about to ask if their intersection
+                        // is inhabited
+                        if (seenSet.contains(*hprop.readTy) && seenSet.contains(*tprop.readTy))
                         {
-                            // We've seen these table prop elements before and we're about to ask if their intersection
-                            // is inhabited
-                            if (fixCyclicTablesBlowingStack())
-                            {
-                                if (seenSet.contains(*hprop.readTy) && seenSet.contains(*tprop.readTy))
-                                {
-                                    seenSet.erase(*hprop.readTy);
-                                    seenSet.erase(*tprop.readTy);
-                                    return {builtinTypes->neverType};
-                                }
-                                else
-                                {
-                                    seenSet.insert(*hprop.readTy);
-                                    seenSet.insert(*tprop.readTy);
-                                }
-                            }
-
-                            NormalizationResult res = isIntersectionInhabited(*hprop.readTy, *tprop.readTy);
-
-                            // Cleanup
-                            if (fixCyclicTablesBlowingStack())
-                            {
-                                seenSet.erase(*hprop.readTy);
-                                seenSet.erase(*tprop.readTy);
-                            }
-
-                            if (NormalizationResult::True != res)
-                                return {builtinTypes->neverType};
+                            seenSet.erase(*hprop.readTy);
+                            seenSet.erase(*tprop.readTy);
+                            return {builtinTypes->neverType};
                         }
                         else
                         {
-                            if (NormalizationResult::False == isIntersectionInhabited(*hprop.readTy, *tprop.readTy))
-                                return {builtinTypes->neverType};
+                            seenSet.insert(*hprop.readTy);
+                            seenSet.insert(*tprop.readTy);
                         }
 
+                        NormalizationResult res = isIntersectionInhabited(*hprop.readTy, *tprop.readTy);
+
+                        // Cleanup
+                        seenSet.erase(*hprop.readTy);
+                        seenSet.erase(*tprop.readTy);
+
+                        if (NormalizationResult::True != res)
+                            return {builtinTypes->neverType};
+
                         TypeId ty = simplifyIntersection(builtinTypes, NotNull{arena}, *hprop.readTy, *tprop.readTy).result;
                         prop.readTy = ty;
                         hereSubThere &= (ty == hprop.readTy);

Analysis/src/TypeChecker2.cpp

@@ -1625,8 +1625,11 @@ void TypeChecker2::indexExprMetatableHelper(AstExprIndexExpr* indexExpr, const M
         indexExprMetatableHelper(indexExpr, mtmt, exprType, indexType);
     else
     {
-        LUAU_ASSERT(tt || get<PrimitiveType>(follow(metaTable->table)));
-
+        if (!(DFInt::LuauTypeSolverRelease >= 647))
+        {
+            LUAU_ASSERT(tt || get<PrimitiveType>(follow(metaTable->table)));
+        }
+        // CLI-122161: We're not handling unions correctly (probably).
         reportError(CannotExtendTable{exprType, CannotExtendTable::Indexer, "indexer??"}, indexExpr->location);
     }
 }

Analysis/src/TypeFunction.cpp

@@ -48,6 +48,7 @@ LUAU_DYNAMIC_FASTINTVARIABLE(LuauTypeFamilyUseGuesserDepth, -1);
 LUAU_FASTFLAGVARIABLE(DebugLuauLogTypeFamilies, false)
 LUAU_FASTFLAGVARIABLE(LuauUserDefinedTypeFunctions2, false)
 LUAU_FASTFLAG(LuauUserDefinedTypeFunctionNoEvaluation)
+LUAU_FASTFLAG(LuauUserTypeFunFixRegister)
 
 LUAU_DYNAMIC_FASTINT(LuauTypeSolverRelease)
 
@@ -1018,9 +1019,11 @@ void TypeFunctionRuntime::prepareState()
 
     setTypeFunctionEnvironment(L);
 
-    // Register type userdata
     registerTypeUserData(L);
 
+    if (FFlag::LuauUserTypeFunFixRegister)
+        registerTypesLibrary(L);
+
     luaL_sandbox(L);
     luaL_sandboxthread(L);
 }