Merge branch 'upstream' into merge

Analysis/include/Luau/Error.h

@@ -107,6 +107,7 @@ struct FunctionDoesNotTakeSelf
 
 struct FunctionRequiresSelf
 {
+    // TODO: Delete with LuauAnyInIsOptionalIsOptional
     int requiredExtraNils = 0;
 
     bool operator==(const FunctionRequiresSelf& rhs) const;

Analysis/include/Luau/Unifier.h

@@ -86,6 +86,8 @@ private:
     void tryUnifyIndexer(const TableIndexer& subIndexer, const TableIndexer& superIndexer);
 
     TypeId widen(TypeId ty);
+    TypePackId widen(TypePackId tp);
+
     TypeId deeplyOptional(TypeId ty, std::unordered_map<TypeId, TypeId> seen = {});
 
     void cacheResult(TypeId subTy, TypeId superTy);

Analysis/src/Autocomplete.cpp

@@ -14,6 +14,7 @@
 #include <utility>
 
 LUAU_FASTFLAGVARIABLE(LuauIfElseExprFixCompletionIssue, false);
+LUAU_FASTFLAG(LuauSelfCallAutocompleteFix)
 
 static const std::unordered_set<std::string> kStatementStartingKeywords = {
     "while", "if", "local", "repeat", "function", "do", "for", "return", "break", "continue", "type", "export"};
@@ -228,11 +229,22 @@ static std::optional<TypeId> findExpectedTypeAt(const Module& module, AstNode* n
     return *it;
 }
 
+static bool checkTypeMatch(TypeArena* typeArena, TypeId subTy, TypeId superTy)
+{
+    InternalErrorReporter iceReporter;
+    UnifierSharedState unifierState(&iceReporter);
+    Unifier unifier(typeArena, Mode::Strict, Location(), Variance::Covariant, unifierState);
+
+    return unifier.canUnify(subTy, superTy).empty();
+}
+
 static TypeCorrectKind checkTypeCorrectKind(const Module& module, TypeArena* typeArena, AstNode* node, Position position, TypeId ty)
 {
     ty = follow(ty);
 
     auto canUnify = [&typeArena](TypeId subTy, TypeId superTy) {
+        LUAU_ASSERT(!FFlag::LuauSelfCallAutocompleteFix);
+
         InternalErrorReporter iceReporter;
         UnifierSharedState unifierState(&iceReporter);
         Unifier unifier(typeArena, Mode::Strict, Location(), Variance::Covariant, unifierState);
@@ -249,20 +261,30 @@ static TypeCorrectKind checkTypeCorrectKind(const Module& module, TypeArena* typ
 
     TypeId expectedType = follow(*typeAtPosition);
 
-    auto checkFunctionType = [&canUnify, &expectedType](const FunctionTypeVar* ftv) {
-        auto [retHead, retTail] = flatten(ftv->retType);
-
-        if (!retHead.empty() && canUnify(retHead.front(), expectedType))
-            return true;
-
-        // We might only have a variadic tail pack, check if the element is compatible
-        if (retTail)
+    auto checkFunctionType = [typeArena, &canUnify, &expectedType](const FunctionTypeVar* ftv) {
+        if (FFlag::LuauSelfCallAutocompleteFix)
         {
-            if (const VariadicTypePack* vtp = get<VariadicTypePack>(follow(*retTail)); vtp && canUnify(vtp->ty, expectedType))
-                return true;
-        }
+            if (std::optional<TypeId> firstRetTy = first(ftv->retType))
+                return checkTypeMatch(typeArena, *firstRetTy, expectedType);
 
-        return false;
+            return false;
+        }
+        else
+        {
+            auto [retHead, retTail] = flatten(ftv->retType);
+
+            if (!retHead.empty() && canUnify(retHead.front(), expectedType))
+                return true;
+
+            // We might only have a variadic tail pack, check if the element is compatible
+            if (retTail)
+            {
+                if (const VariadicTypePack* vtp = get<VariadicTypePack>(follow(*retTail)); vtp && canUnify(vtp->ty, expectedType))
+                    return true;
+            }
+
+            return false;
+        }
     };
 
     // We also want to suggest functions that return compatible result
@@ -281,7 +303,10 @@ static TypeCorrectKind checkTypeCorrectKind(const Module& module, TypeArena* typ
         }
     }
 
-    return canUnify(ty, expectedType) ? TypeCorrectKind::Correct : TypeCorrectKind::None;
+    if (FFlag::LuauSelfCallAutocompleteFix)
+        return checkTypeMatch(typeArena, ty, expectedType) ? TypeCorrectKind::Correct : TypeCorrectKind::None;
+    else
+        return canUnify(ty, expectedType) ? TypeCorrectKind::Correct : TypeCorrectKind::None;
 }
 
 enum class PropIndexType
@@ -291,16 +316,22 @@ enum class PropIndexType
     Key,
 };
 
-static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId ty, PropIndexType indexType, const std::vector<AstNode*>& nodes,
-    AutocompleteEntryMap& result, std::unordered_set<TypeId>& seen, std::optional<const ClassTypeVar*> containingClass = std::nullopt)
+static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId rootTy, TypeId ty, PropIndexType indexType,
+    const std::vector<AstNode*>& nodes, AutocompleteEntryMap& result, std::unordered_set<TypeId>& seen,
+    std::optional<const ClassTypeVar*> containingClass = std::nullopt)
 {
+    if (FFlag::LuauSelfCallAutocompleteFix)
+        rootTy = follow(rootTy);
+
     ty = follow(ty);
 
     if (seen.count(ty))
         return;
     seen.insert(ty);
 
-    auto isWrongIndexer = [indexType, useStrictFunctionIndexers = !!get<ClassTypeVar>(ty)](Luau::TypeId type) {
+    auto isWrongIndexer_DEPRECATED = [indexType, useStrictFunctionIndexers = !!get<ClassTypeVar>(ty)](Luau::TypeId type) {
+        LUAU_ASSERT(!FFlag::LuauSelfCallAutocompleteFix);
+
         if (indexType == PropIndexType::Key)
             return false;
 
@@ -331,6 +362,48 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
             return colonIndex;
         }
     };
+    auto isWrongIndexer = [typeArena, rootTy, indexType](Luau::TypeId type) {
+        LUAU_ASSERT(FFlag::LuauSelfCallAutocompleteFix);
+
+        if (indexType == PropIndexType::Key)
+            return false;
+
+        bool calledWithSelf = indexType == PropIndexType::Colon;
+
+        auto isCompatibleCall = [typeArena, rootTy, calledWithSelf](const FunctionTypeVar* ftv) {
+            if (get<ClassTypeVar>(rootTy))
+            {
+                // Calls on classes require strict match between how function is declared and how it's called
+                return calledWithSelf == ftv->hasSelf;
+            }
+
+            if (std::optional<TypeId> firstArgTy = first(ftv->argTypes))
+            {
+                if (checkTypeMatch(typeArena, rootTy, *firstArgTy))
+                    return calledWithSelf;
+            }
+
+            return !calledWithSelf;
+        };
+
+        if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(type))
+            return !isCompatibleCall(ftv);
+
+        // For intersections, any part that is successful makes the whole call successful
+        if (const IntersectionTypeVar* itv = get<IntersectionTypeVar>(type))
+        {
+            for (auto subType : itv->parts)
+            {
+                if (const FunctionTypeVar* ftv = get<FunctionTypeVar>(Luau::follow(subType)))
+                {
+                    if (isCompatibleCall(ftv))
+                        return false;
+                }
+            }
+        }
+
+        return calledWithSelf;
+    };
 
     auto fillProps = [&](const ClassTypeVar::Props& props) {
         for (const auto& [name, prop] : props)
@@ -349,7 +422,7 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
                     AutocompleteEntryKind::Property,
                     type,
                     prop.deprecated,
-                    isWrongIndexer(type),
+                    FFlag::LuauSelfCallAutocompleteFix ? isWrongIndexer(type) : isWrongIndexer_DEPRECATED(type),
                     typeCorrect,
                     containingClass,
                     &prop,
@@ -361,34 +434,60 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
         }
     };
 
-    if (auto cls = get<ClassTypeVar>(ty))
-    {
-        containingClass = containingClass.value_or(cls);
-        fillProps(cls->props);
-        if (cls->parent)
-            autocompleteProps(module, typeArena, *cls->parent, indexType, nodes, result, seen, cls);
-    }
-    else if (auto tbl = get<TableTypeVar>(ty))
-        fillProps(tbl->props);
-    else if (auto mt = get<MetatableTypeVar>(ty))
-    {
-        autocompleteProps(module, typeArena, mt->table, indexType, nodes, result, seen);
-
-        auto mtable = get<TableTypeVar>(mt->metatable);
-        if (!mtable)
-            return;
-
+    auto fillMetatableProps = [&](const TableTypeVar* mtable) {
         auto indexIt = mtable->props.find("__index");
         if (indexIt != mtable->props.end())
         {
             TypeId followed = follow(indexIt->second.type);
             if (get<TableTypeVar>(followed) || get<MetatableTypeVar>(followed))
-                autocompleteProps(module, typeArena, followed, indexType, nodes, result, seen);
+            {
+                autocompleteProps(module, typeArena, rootTy, followed, indexType, nodes, result, seen);
+            }
             else if (auto indexFunction = get<FunctionTypeVar>(followed))
             {
                 std::optional<TypeId> indexFunctionResult = first(indexFunction->retType);
                 if (indexFunctionResult)
-                    autocompleteProps(module, typeArena, *indexFunctionResult, indexType, nodes, result, seen);
+                    autocompleteProps(module, typeArena, rootTy, *indexFunctionResult, indexType, nodes, result, seen);
+            }
+        }
+    };
+
+    if (auto cls = get<ClassTypeVar>(ty))
+    {
+        containingClass = containingClass.value_or(cls);
+        fillProps(cls->props);
+        if (cls->parent)
+            autocompleteProps(module, typeArena, rootTy, *cls->parent, indexType, nodes, result, seen, cls);
+    }
+    else if (auto tbl = get<TableTypeVar>(ty))
+        fillProps(tbl->props);
+    else if (auto mt = get<MetatableTypeVar>(ty))
+    {
+        autocompleteProps(module, typeArena, rootTy, mt->table, indexType, nodes, result, seen);
+
+        if (FFlag::LuauSelfCallAutocompleteFix)
+        {
+            if (auto mtable = get<TableTypeVar>(mt->metatable))
+                fillMetatableProps(mtable);
+        }
+        else
+        {
+            auto mtable = get<TableTypeVar>(mt->metatable);
+            if (!mtable)
+                return;
+
+            auto indexIt = mtable->props.find("__index");
+            if (indexIt != mtable->props.end())
+            {
+                TypeId followed = follow(indexIt->second.type);
+                if (get<TableTypeVar>(followed) || get<MetatableTypeVar>(followed))
+                    autocompleteProps(module, typeArena, rootTy, followed, indexType, nodes, result, seen);
+                else if (auto indexFunction = get<FunctionTypeVar>(followed))
+                {
+                    std::optional<TypeId> indexFunctionResult = first(indexFunction->retType);
+                    if (indexFunctionResult)
+                        autocompleteProps(module, typeArena, rootTy, *indexFunctionResult, indexType, nodes, result, seen);
+                }
             }
         }
     }
@@ -400,7 +499,7 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
             AutocompleteEntryMap inner;
             std::unordered_set<TypeId> innerSeen = seen;
 
-            autocompleteProps(module, typeArena, ty, indexType, nodes, inner, innerSeen);
+            autocompleteProps(module, typeArena, rootTy, ty, indexType, nodes, inner, innerSeen);
 
             for (auto& pair : inner)
                 result.insert(pair);
@@ -423,14 +522,17 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
         if (iter == endIter)
             return;
 
-        autocompleteProps(module, typeArena, *iter, indexType, nodes, result, seen);
+        autocompleteProps(module, typeArena, rootTy, *iter, indexType, nodes, result, seen);
 
         ++iter;
 
         while (iter != endIter)
         {
             AutocompleteEntryMap inner;
-            std::unordered_set<TypeId> innerSeen = seen;
+            std::unordered_set<TypeId> innerSeen;
+
+            if (!FFlag::LuauSelfCallAutocompleteFix)
+                innerSeen = seen;
 
             if (isNil(*iter))
             {
@@ -438,7 +540,7 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
                 continue;
             }
 
-            autocompleteProps(module, typeArena, *iter, indexType, nodes, inner, innerSeen);
+            autocompleteProps(module, typeArena, rootTy, *iter, indexType, nodes, inner, innerSeen);
 
             std::unordered_set<std::string> toRemove;
 
@@ -455,6 +557,18 @@ static void autocompleteProps(const Module& module, TypeArena* typeArena, TypeId
             ++iter;
         }
     }
+    else if (auto pt = get<PrimitiveTypeVar>(ty); pt && FFlag::LuauSelfCallAutocompleteFix)
+    {
+        if (pt->metatable)
+        {
+            if (auto mtable = get<TableTypeVar>(*pt->metatable))
+                fillMetatableProps(mtable);
+        }
+    }
+    else if (FFlag::LuauSelfCallAutocompleteFix && get<StringSingleton>(get<SingletonTypeVar>(ty)))
+    {
+        autocompleteProps(module, typeArena, rootTy, getSingletonTypes().stringType, indexType, nodes, result, seen);
+    }
 }
 
 static void autocompleteKeywords(
@@ -482,7 +596,7 @@ static void autocompleteProps(
     const Module& module, TypeArena* typeArena, TypeId ty, PropIndexType indexType, const std::vector<AstNode*>& nodes, AutocompleteEntryMap& result)
 {
     std::unordered_set<TypeId> seen;
-    autocompleteProps(module, typeArena, ty, indexType, nodes, result, seen);
+    autocompleteProps(module, typeArena, ty, ty, indexType, nodes, result, seen);
 }
 
 AutocompleteEntryMap autocompleteProps(
@@ -1352,7 +1466,7 @@ static AutocompleteResult autocomplete(const SourceModule& sourceModule, const M
         TypeId ty = follow(*it);
         PropIndexType indexType = indexName->op == ':' ? PropIndexType::Colon : PropIndexType::Point;
 
-        if (isString(ty))
+        if (!FFlag::LuauSelfCallAutocompleteFix && isString(ty))
             return {autocompleteProps(*module, typeArena, typeChecker.globalScope->bindings[AstName{"string"}].typeId, indexType, finder.ancestry),
                 finder.ancestry};
         else

Analysis/src/EmbeddedBuiltinDefinitions.cpp

@@ -95,104 +95,104 @@ declare os: {
 
 declare function require(target: any): any
 
-declare function getfenv(target: any?): { [string]: any }
+declare function getfenv(target: any): { [string]: any }
 
 declare _G: any
 declare _VERSION: string
 
 declare function gcinfo(): number
 
-            declare function print<T...>(...: T...)
+declare function print<T...>(...: T...)
 
-            declare function type<T>(value: T): string
-            declare function typeof<T>(value: T): string
+declare function type<T>(value: T): string
+declare function typeof<T>(value: T): string
 
-            -- `assert` has a magic function attached that will give more detailed type information
-            declare function assert<T>(value: T, errorMessage: string?): T
+-- `assert` has a magic function attached that will give more detailed type information
+declare function assert<T>(value: T, errorMessage: string?): T
 
-            declare function error<T>(message: T, level: number?)
+declare function error<T>(message: T, level: number?)
 
-            declare function tostring<T>(value: T): string
-            declare function tonumber<T>(value: T, radix: number?): number?
+declare function tostring<T>(value: T): string
+declare function tonumber<T>(value: T, radix: number?): number?
 
-            declare function rawequal<T1, T2>(a: T1, b: T2): boolean
-            declare function rawget<K, V>(tab: {[K]: V}, k: K): V
-            declare function rawset<K, V>(tab: {[K]: V}, k: K, v: V): {[K]: V}
+declare function rawequal<T1, T2>(a: T1, b: T2): boolean
+declare function rawget<K, V>(tab: {[K]: V}, k: K): V
+declare function rawset<K, V>(tab: {[K]: V}, k: K, v: V): {[K]: V}
 
-            declare function setfenv<T..., R...>(target: number | (T...) -> R..., env: {[string]: any}): ((T...) -> R...)?
+declare function setfenv<T..., R...>(target: number | (T...) -> R..., env: {[string]: any}): ((T...) -> R...)?
 
-            declare function ipairs<V>(tab: {V}): (({V}, number) -> (number, V), {V}, number)
+declare function ipairs<V>(tab: {V}): (({V}, number) -> (number, V), {V}, number)
 
-            declare function pcall<A..., R...>(f: (A...) -> R..., ...: A...): (boolean, R...)
+declare function pcall<A..., R...>(f: (A...) -> R..., ...: A...): (boolean, R...)
 
-            -- FIXME: The actual type of `xpcall` is:
-            -- <E, A..., R1..., R2...>(f: (A...) -> R1..., err: (E) -> R2..., A...) -> (true, R1...) | (false, R2...)
-            -- Since we can't represent the return value, we use (boolean, R1...).
-            declare function xpcall<E, A..., R1..., R2...>(f: (A...) -> R1..., err: (E) -> R2..., ...: A...): (boolean, R1...)
+-- FIXME: The actual type of `xpcall` is:
+-- <E, A..., R1..., R2...>(f: (A...) -> R1..., err: (E) -> R2..., A...) -> (true, R1...) | (false, R2...)
+-- Since we can't represent the return value, we use (boolean, R1...).
+declare function xpcall<E, A..., R1..., R2...>(f: (A...) -> R1..., err: (E) -> R2..., ...: A...): (boolean, R1...)
 
-            -- `select` has a magic function attached to provide more detailed type information
-            declare function select<A...>(i: string | number, ...: A...): ...any
+-- `select` has a magic function attached to provide more detailed type information
+declare function select<A...>(i: string | number, ...: A...): ...any
 
-            -- FIXME: This type is not entirely correct - `loadstring` returns a function or
-            -- (nil, string).
-            declare function loadstring<A...>(src: string, chunkname: string?): (((A...) -> any)?, string?)
+-- FIXME: This type is not entirely correct - `loadstring` returns a function or
+-- (nil, string).
+declare function loadstring<A...>(src: string, chunkname: string?): (((A...) -> any)?, string?)
 
-            declare function newproxy(mt: boolean?): any
+declare function newproxy(mt: boolean?): any
 
-            declare coroutine: {
-                create: <A..., R...>((A...) -> R...) -> thread,
-                resume: <A..., R...>(thread, A...) -> (boolean, R...),
-                running: () -> thread,
-                status: (thread) -> string,
-                -- FIXME: This technically returns a function, but we can't represent this yet.
-                wrap: <A..., R...>((A...) -> R...) -> any,
-                yield: <A..., R...>(A...) -> R...,
-                isyieldable: () -> boolean,
-                close: (thread) -> (boolean, any?)
-            }
+declare coroutine: {
+    create: <A..., R...>((A...) -> R...) -> thread,
+    resume: <A..., R...>(thread, A...) -> (boolean, R...),
+    running: () -> thread,
+    status: (thread) -> string,
+    -- FIXME: This technically returns a function, but we can't represent this yet.
+    wrap: <A..., R...>((A...) -> R...) -> any,
+    yield: <A..., R...>(A...) -> R...,
+    isyieldable: () -> boolean,
+    close: (thread) -> (boolean, any)
+}
 
-            declare table: {
-                concat: <V>({V}, string?, number?, number?) -> string,
-                insert: (<V>({V}, V) -> ()) & (<V>({V}, number, V) -> ()),
-                maxn: <V>({V}) -> number,
-                remove: <V>({V}, number?) -> V?,
-                sort: <V>({V}, ((V, V) -> boolean)?) -> (),
-                create: <V>(number, V?) -> {V},
-                find: <V>({V}, V, number?) -> number?,
+declare table: {
+    concat: <V>({V}, string?, number?, number?) -> string,
+    insert: (<V>({V}, V) -> ()) & (<V>({V}, number, V) -> ()),
+    maxn: <V>({V}) -> number,
+    remove: <V>({V}, number?) -> V?,
+    sort: <V>({V}, ((V, V) -> boolean)?) -> (),
+    create: <V>(number, V?) -> {V},
+    find: <V>({V}, V, number?) -> number?,
 
-                unpack: <V>({V}, number?, number?) -> ...V,
-                pack: <V>(...V) -> { n: number, [number]: V },
+    unpack: <V>({V}, number?, number?) -> ...V,
+    pack: <V>(...V) -> { n: number, [number]: V },
 
-                getn: <V>({V}) -> number,
-                foreach: <K, V>({[K]: V}, (K, V) -> ()) -> (),
-                foreachi: <V>({V}, (number, V) -> ()) -> (),
+    getn: <V>({V}) -> number,
+    foreach: <K, V>({[K]: V}, (K, V) -> ()) -> (),
+    foreachi: <V>({V}, (number, V) -> ()) -> (),
 
-                move: <V>({V}, number, number, number, {V}?) -> {V},
-                clear: <K, V>({[K]: V}) -> (),
+    move: <V>({V}, number, number, number, {V}?) -> {V},
+    clear: <K, V>({[K]: V}) -> (),
 
-                isfrozen: <K, V>({[K]: V}) -> boolean,
-            }
+    isfrozen: <K, V>({[K]: V}) -> boolean,
+}
 
-            declare debug: {
-                info: (<R...>(thread, number, string) -> R...) & (<R...>(number, string) -> R...) & (<A..., R1..., R2...>((A...) -> R1..., string) -> R2...),
-                traceback: ((string?, number?) -> string) & ((thread, string?, number?) -> string),
-            }
+declare debug: {
+    info: (<R...>(thread, number, string) -> R...) & (<R...>(number, string) -> R...) & (<A..., R1..., R2...>((A...) -> R1..., string) -> R2...),
+    traceback: ((string?, number?) -> string) & ((thread, string?, number?) -> string),
+}
 
-            declare utf8: {
-                char: (number, ...number) -> string,
-                charpattern: string,
-                codes: (string) -> ((string, number) -> (number, number), string, number),
-                -- FIXME
-                codepoint: (string, number?, number?) -> (number, ...number),
-                len: (string, number?, number?) -> (number?, number?),
-                offset: (string, number?, number?) -> number,
-                nfdnormalize: (string) -> string,
-                nfcnormalize: (string) -> string,
-                graphemes: (string, number?, number?) -> (() -> (number, number)),
-            }
+declare utf8: {
+    char: (number, ...number) -> string,
+    charpattern: string,
+    codes: (string) -> ((string, number) -> (number, number), string, number),
+    -- FIXME
+    codepoint: (string, number?, number?) -> (number, ...number),
+    len: (string, number?, number?) -> (number?, number?),
+    offset: (string, number?, number?) -> number,
+    nfdnormalize: (string) -> string,
+    nfcnormalize: (string) -> string,
+    graphemes: (string, number?, number?) -> (() -> (number, number)),
+}
 
-            -- Cannot use `typeof` here because it will produce a polytype when we expect a monotype.
-            declare function unpack<V>(tab: {V}, i: number?, j: number?): ...V
+-- Cannot use `typeof` here because it will produce a polytype when we expect a monotype.
+declare function unpack<V>(tab: {V}, i: number?, j: number?): ...V
 
 )BUILTIN_SRC";
 

Analysis/src/Error.cpp

@@ -7,6 +7,8 @@
 
 #include <stdexcept>
 
+LUAU_FASTFLAGVARIABLE(BetterDiagnosticCodesInStudio, false);
+
 static std::string wrongNumberOfArgsString(size_t expectedCount, size_t actualCount, const char* argPrefix = nullptr, bool isVariadic = false)
 {
     std::string s = "expects ";
@@ -223,7 +225,14 @@ struct ErrorConverter
 
     std::string operator()(const Luau::SyntaxError& e) const
     {
-        return "Syntax error: " + e.message;
+        if (FFlag::BetterDiagnosticCodesInStudio)
+        {
+            return e.message;
+        }
+        else
+        {
+            return "Syntax error: " + e.message;
+        }
     }
 
     std::string operator()(const Luau::CodeTooComplex&) const

Analysis/src/Module.cpp

@@ -14,6 +14,7 @@
 LUAU_FASTFLAGVARIABLE(DebugLuauFreezeArena, false)
 LUAU_FASTFLAGVARIABLE(DebugLuauTrackOwningArena, false) // Remove with FFlagLuauImmutableTypes
 LUAU_FASTINTVARIABLE(LuauTypeCloneRecursionLimit, 300)
+LUAU_FASTFLAGVARIABLE(LuauCloneDeclaredGlobals, false)
 LUAU_FASTFLAG(LuauImmutableTypes)
 
 namespace Luau
@@ -536,6 +537,12 @@ bool Module::clonePublicInterface()
         if (get<GenericTypeVar>(follow(ty)))
             *asMutable(ty) = AnyTypeVar{};
 
+    if (FFlag::LuauCloneDeclaredGlobals)
+    {
+        for (auto& [name, ty] : declaredGlobals)
+            ty = clone(ty, interfaceTypes, seenTypes, seenTypePacks, cloneState);
+    }
+
     freeze(internalTypes);
     freeze(interfaceTypes);
 

Analysis/src/TypeInfer.cpp

@@ -29,22 +29,24 @@ LUAU_FASTFLAGVARIABLE(LuauRecursiveTypeParameterRestriction, false)
 LUAU_FASTFLAGVARIABLE(LuauGenericFunctionsDontCacheTypeParams, false)
 LUAU_FASTFLAGVARIABLE(LuauImmutableTypes, false)
 LUAU_FASTFLAGVARIABLE(LuauSealExports, false)
+LUAU_FASTFLAGVARIABLE(LuauSelfCallAutocompleteFix, false)
 LUAU_FASTFLAGVARIABLE(LuauSingletonTypes, false)
 LUAU_FASTFLAGVARIABLE(LuauDiscriminableUnions2, false)
 LUAU_FASTFLAGVARIABLE(LuauExpectedTypesOfProperties, false)
 LUAU_FASTFLAGVARIABLE(LuauErrorRecoveryType, false)
 LUAU_FASTFLAGVARIABLE(LuauOnlyMutateInstantiatedTables, false)
 LUAU_FASTFLAGVARIABLE(LuauPropertiesGetExpectedType, false)
-LUAU_FASTFLAGVARIABLE(LuauStatFunctionSimplify, false)
+LUAU_FASTFLAGVARIABLE(LuauStatFunctionSimplify2, false)
 LUAU_FASTFLAGVARIABLE(LuauUnsealedTableLiteral, false)
 LUAU_FASTFLAGVARIABLE(LuauTwoPassAliasDefinitionFix, false)
 LUAU_FASTFLAGVARIABLE(LuauAssertStripsFalsyTypes, false)
 LUAU_FASTFLAGVARIABLE(LuauReturnAnyInsteadOfICE, false) // Eventually removed as false.
-LUAU_FASTFLAG(LuauWidenIfSupertypeIsFree)
+LUAU_FASTFLAG(LuauWidenIfSupertypeIsFree2)
 LUAU_FASTFLAGVARIABLE(LuauDoNotTryToReduce, false)
 LUAU_FASTFLAGVARIABLE(LuauDoNotAccidentallyDependOnPointerOrdering, false)
 LUAU_FASTFLAGVARIABLE(LuauFixArgumentCountMismatchAmountWithGenericTypes, false)
 LUAU_FASTFLAGVARIABLE(LuauFixIncorrectLineNumberDuplicateType, false)
+LUAU_FASTFLAG(LuauAnyInIsOptionalIsOptional)
 
 namespace Luau
 {
@@ -1099,7 +1101,7 @@ 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::LuauStatFunctionSimplify)
+    else if (auto name = function.name->as<AstExprIndexName>(); name && FFlag::LuauStatFunctionSimplify2)
     {
         TypeId exprTy = checkExpr(scope, *name->expr).type;
         TableTypeVar* ttv = getMutableTableType(exprTy);
@@ -1111,7 +1113,10 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
                 reportError(TypeError{function.location, OnlyTablesCanHaveMethods{exprTy}});
         }
         else if (ttv->state == TableState::Sealed)
-            reportError(TypeError{function.location, CannotExtendTable{exprTy, CannotExtendTable::Property, name->index.value}});
+        {
+            if (!ttv->indexer || !isPrim(ttv->indexer->indexType, PrimitiveTypeVar::String))
+                reportError(TypeError{function.location, CannotExtendTable{exprTy, CannotExtendTable::Property, name->index.value}});
+        }
 
         ty = follow(ty);
 
@@ -1134,7 +1139,7 @@ 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::LuauStatFunctionSimplify)
+    else if (FFlag::LuauStatFunctionSimplify2)
     {
         LUAU_ASSERT(function.name->is<AstExprError>());
 
@@ -1144,7 +1149,7 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
     }
     else if (function.func->self)
     {
-        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify);
+        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify2);
 
         AstExprIndexName* indexName = function.name->as<AstExprIndexName>();
         if (!indexName)
@@ -1183,7 +1188,7 @@ void TypeChecker::check(const ScopePtr& scope, TypeId ty, const ScopePtr& funSco
     }
     else
     {
-        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify);
+        LUAU_ASSERT(!FFlag::LuauStatFunctionSimplify2);
 
         TypeId leftType = checkLValueBinding(scope, *function.name);
 
@@ -1410,6 +1415,9 @@ void TypeChecker::check(const ScopePtr& scope, const AstStatDeclareClass& declar
             {
                 ftv->argNames.insert(ftv->argNames.begin(), FunctionArgument{"self", {}});
                 ftv->argTypes = addTypePack(TypePack{{classTy}, ftv->argTypes});
+
+                if (FFlag::LuauSelfCallAutocompleteFix)
+                    ftv->hasSelf = true;
             }
         }
 
@@ -1883,19 +1891,27 @@ std::optional<TypeId> TypeChecker::tryStripUnionFromNil(TypeId ty)
 {
     if (const UnionTypeVar* utv = get<UnionTypeVar>(ty))
     {
-        bool hasNil = false;
-
-        for (TypeId option : utv)
+        if (FFlag::LuauAnyInIsOptionalIsOptional)
         {
-            if (isNil(option))
-            {
-                hasNil = true;
-                break;
-            }
+            if (!std::any_of(begin(utv), end(utv), isNil))
+                return ty;
         }
+        else
+        {
+            bool hasNil = false;
 
-        if (!hasNil)
-            return ty;
+            for (TypeId option : utv)
+            {
+                if (isNil(option))
+                {
+                    hasNil = true;
+                    break;
+                }
+            }
+
+            if (!hasNil)
+                return ty;
+        }
 
         std::vector<TypeId> result;
 
@@ -1916,14 +1932,34 @@ std::optional<TypeId> TypeChecker::tryStripUnionFromNil(TypeId ty)
 
 TypeId TypeChecker::stripFromNilAndReport(TypeId ty, const Location& location)
 {
-    if (isOptional(ty))
+    if (FFlag::LuauAnyInIsOptionalIsOptional)
     {
-        if (std::optional<TypeId> strippedUnion = tryStripUnionFromNil(follow(ty)))
+        ty = follow(ty);
+
+        if (auto utv = get<UnionTypeVar>(ty))
+        {
+            if (!std::any_of(begin(utv), end(utv), isNil))
+                return ty;
+
+        }
+
+        if (std::optional<TypeId> strippedUnion = tryStripUnionFromNil(ty))
         {
             reportError(location, OptionalValueAccess{ty});
             return follow(*strippedUnion);
         }
     }
+    else
+    {
+        if (isOptional(ty))
+        {
+            if (std::optional<TypeId> strippedUnion = tryStripUnionFromNil(follow(ty)))
+            {
+                reportError(location, OptionalValueAccess{ty});
+                return follow(*strippedUnion);
+            }
+        }
+    }
 
     return ty;
 }
@@ -2935,9 +2971,25 @@ TypeId TypeChecker::checkFunctionName(const ScopePtr& scope, AstExpr& funName, T
             return errorRecoveryType(scope);
         }
 
-        // Cannot extend sealed table, but we dont report an error here because it will be reported during AstStatFunction check
-        if (lhsType->persistent || ttv->state == TableState::Sealed)
-            return errorRecoveryType(scope);
+        if (FFlag::LuauStatFunctionSimplify2)
+        {
+            if (lhsType->persistent)
+                return errorRecoveryType(scope);
+
+            // Cannot extend sealed table, but we dont report an error here because it will be reported during AstStatFunction check
+            if (ttv->state == TableState::Sealed)
+            {
+                if (ttv->indexer && isPrim(ttv->indexer->indexType, PrimitiveTypeVar::String))
+                    return ttv->indexer->indexResultType;
+                else
+                    return errorRecoveryType(scope);
+            }
+        }
+        else
+        {
+            if (lhsType->persistent || ttv->state == TableState::Sealed)
+                return errorRecoveryType(scope);
+        }
 
         Name name = indexName->index.value;
 
@@ -3393,7 +3445,7 @@ void TypeChecker::checkArgumentList(
                 else if (state.log.getMutable<ErrorTypeVar>(t))
                 {
                 } // ok
-                else if (isNonstrictMode() && state.log.getMutable<AnyTypeVar>(t))
+                else if (!FFlag::LuauAnyInIsOptionalIsOptional && isNonstrictMode() && state.log.getMutable<AnyTypeVar>(t))
                 {
                 } // ok
                 else
@@ -3467,7 +3519,11 @@ void TypeChecker::checkArgumentList(
                 }
 
                 TypePackId varPack = addTypePack(TypePackVar{TypePack{rest, argIter.tail()}});
-                state.tryUnify(varPack, tail);
+                if (FFlag::LuauWidenIfSupertypeIsFree2)
+                    state.tryUnify(varPack, tail);
+                else
+                    state.tryUnify(tail, varPack);
+
                 return;
             }
             else if (state.log.getMutable<FreeTypePack>(tail))
@@ -3542,6 +3598,23 @@ ExprResult<TypePackId> TypeChecker::checkExprPack(const ScopePtr& scope, const A
 
     actualFunctionType = follow(actualFunctionType);
 
+    TypePackId retPack;
+    if (!FFlag::LuauWidenIfSupertypeIsFree2)
+    {
+        retPack = freshTypePack(scope->level);
+    }
+    else
+    {
+        if (auto free = get<FreeTypeVar>(actualFunctionType))
+        {
+            retPack = freshTypePack(free->level);
+            TypePackId freshArgPack = freshTypePack(free->level);
+            *asMutable(actualFunctionType) = FunctionTypeVar(free->level, freshArgPack, retPack);
+        }
+        else
+            retPack = freshTypePack(scope->level);
+    }
+
     // checkExpr will log the pre-instantiated type of the function.
     // That's not nearly as interesting as the instantiated type, which will include details about how
     // generic functions are being instantiated for this particular callsite.
@@ -3550,8 +3623,6 @@ ExprResult<TypePackId> TypeChecker::checkExprPack(const ScopePtr& scope, const A
 
     std::vector<TypeId> overloads = flattenIntersection(actualFunctionType);
 
-    TypePackId retPack = freshTypePack(scope->level);
-
     std::vector<std::optional<TypeId>> expectedTypes = getExpectedTypesForCall(overloads, expr.args.size, expr.self);
 
     ExprResult<TypePackId> argListResult = checkExprList(scope, expr.location, expr.args, false, {}, expectedTypes);
@@ -3682,7 +3753,7 @@ std::optional<ExprResult<TypePackId>> TypeChecker::checkCallOverload(const Scope
         // has been instantiated, so is a monotype. We can therefore
         // unify it with a monomorphic function.
         TypeId r = addType(FunctionTypeVar(scope->level, argPack, retPack));
-        if (FFlag::LuauWidenIfSupertypeIsFree)
+        if (FFlag::LuauWidenIfSupertypeIsFree2)
         {
             UnifierOptions options;
             options.isFunctionCall = true;
@@ -3772,7 +3843,7 @@ std::optional<ExprResult<TypePackId>> TypeChecker::checkCallOverload(const Scope
     {
         state.log.commit();
 
-        if (isNonstrictMode() && !expr.self && expr.func->is<AstExprIndexName>() && ftv->hasSelf)
+        if (!FFlag::LuauAnyInIsOptionalIsOptional && isNonstrictMode() && !expr.self && expr.func->is<AstExprIndexName>() && ftv->hasSelf)
         {
             // If we are running in nonstrict mode, passing fewer arguments than the function is declared to take AND
             // the function is declared with colon notation AND we use dot notation, warn.

Analysis/src/TypeVar.cpp

@@ -26,6 +26,7 @@ LUAU_FASTINT(LuauTypeInferRecursionLimit)
 LUAU_FASTFLAG(LuauErrorRecoveryType)
 LUAU_FASTFLAG(LuauSubtypingAddOptPropsToUnsealedTables)
 LUAU_FASTFLAG(LuauDiscriminableUnions2)
+LUAU_FASTFLAGVARIABLE(LuauAnyInIsOptionalIsOptional, false)
 
 namespace Luau
 {
@@ -201,11 +202,16 @@ bool isOptional(TypeId ty)
     if (isNil(ty))
         return true;
 
-    auto utv = get<UnionTypeVar>(follow(ty));
+    ty = follow(ty);
+
+    if (FFlag::LuauAnyInIsOptionalIsOptional && get<AnyTypeVar>(ty))
+        return true;
+
+    auto utv = get<UnionTypeVar>(ty);
     if (!utv)
         return false;
 
-    return std::any_of(begin(utv), end(utv), isNil);
+    return std::any_of(begin(utv), end(utv), FFlag::LuauAnyInIsOptionalIsOptional ? isOptional : isNil);
 }
 
 bool isTableIntersection(TypeId ty)

Analysis/src/Unifier.cpp

@@ -20,11 +20,13 @@ LUAU_FASTFLAGVARIABLE(LuauTableSubtypingVariance2, false);
 LUAU_FASTFLAG(LuauSingletonTypes)
 LUAU_FASTFLAG(LuauErrorRecoveryType);
 LUAU_FASTFLAGVARIABLE(LuauSubtypingAddOptPropsToUnsealedTables, false)
-LUAU_FASTFLAGVARIABLE(LuauWidenIfSupertypeIsFree, false)
+LUAU_FASTFLAGVARIABLE(LuauWidenIfSupertypeIsFree2, false)
 LUAU_FASTFLAGVARIABLE(LuauDifferentOrderOfUnificationDoesntMatter, false)
 LUAU_FASTFLAGVARIABLE(LuauTxnLogSeesTypePacks2, false)
 LUAU_FASTFLAGVARIABLE(LuauTxnLogCheckForInvalidation, false)
+LUAU_FASTFLAGVARIABLE(LuauTxnLogRefreshFunctionPointers, false)
 LUAU_FASTFLAGVARIABLE(LuauTxnLogDontRetryForIndexers, false)
+LUAU_FASTFLAG(LuauAnyInIsOptionalIsOptional)
 
 namespace Luau
 {
@@ -272,12 +274,6 @@ TypePackId Widen::clean(TypePackId)
 
 bool Widen::ignoreChildren(TypeId ty)
 {
-    // Sometimes we unify ("hi") -> free1 with (free2) -> free3, so don't ignore functions.
-    // TODO: should we be doing this? we would need to rework how checkCallOverload does the unification.
-    if (log->is<FunctionTypeVar>(ty))
-        return false;
-
-    // We only care about unions.
     return !log->is<UnionTypeVar>(ty);
 }
 
@@ -990,7 +986,7 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
 
         if (!log.getMutable<ErrorTypeVar>(superTp))
         {
-            log.replace(superTp, Unifiable::Bound<TypePackId>(subTp));
+            log.replace(superTp, Unifiable::Bound<TypePackId>(widen(subTp)));
         }
     }
     else if (log.getMutable<Unifiable::Free>(subTp))
@@ -1107,7 +1103,7 @@ void Unifier::tryUnify_(TypePackId subTp, TypePackId superTp, bool isFunctionCal
                 }
 
                 // In nonstrict mode, any also marks an optional argument.
-                else if (superIter.good() && isNonstrictMode() && log.getMutable<AnyTypeVar>(log.follow(*superIter)))
+                else if (!FFlag::LuauAnyInIsOptionalIsOptional && superIter.good() && isNonstrictMode() && log.getMutable<AnyTypeVar>(log.follow(*superIter)))
                 {
                     superIter.advance();
                     continue;
@@ -1280,6 +1276,13 @@ void Unifier::tryUnifyFunctions(TypeId subTy, TypeId superTy, bool isFunctionCal
         tryUnify_(subFunction->retType, superFunction->retType);
     }
 
+    if (FFlag::LuauTxnLogRefreshFunctionPointers)
+    {
+        // Updating the log may have invalidated the function pointers
+        superFunction = log.getMutable<FunctionTypeVar>(superTy);
+        subFunction = log.getMutable<FunctionTypeVar>(subTy);
+    }
+
     if (!FFlag::LuauImmutableTypes)
     {
         if (superFunction->definition && !subFunction->definition && !subTy->persistent)
@@ -1357,10 +1360,18 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         {
             auto subIter = subTable->props.find(propName);
 
-            bool isAny = log.getMutable<AnyTypeVar>(log.follow(superProp.type));
+            if (FFlag::LuauAnyInIsOptionalIsOptional)
+            {
+                if (subIter == subTable->props.end() && (!FFlag::LuauSubtypingAddOptPropsToUnsealedTables || subTable->state == TableState::Unsealed) && !isOptional(superProp.type))
+                    missingProperties.push_back(propName);
+            }
+            else
+            {
+                bool isAny = log.getMutable<AnyTypeVar>(log.follow(superProp.type));
 
-            if (subIter == subTable->props.end() && (!FFlag::LuauSubtypingAddOptPropsToUnsealedTables || subTable->state == TableState::Unsealed) && !isOptional(superProp.type) && !isAny)
-                missingProperties.push_back(propName);
+                if (subIter == subTable->props.end() && (!FFlag::LuauSubtypingAddOptPropsToUnsealedTables || subTable->state == TableState::Unsealed) && !isOptional(superProp.type) && !isAny)
+                    missingProperties.push_back(propName);
+            }
         }
 
         if (!missingProperties.empty())
@@ -1378,9 +1389,17 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         {
             auto superIter = superTable->props.find(propName);
 
-            bool isAny = log.is<AnyTypeVar>(log.follow(subProp.type));
-            if (superIter == superTable->props.end() && (FFlag::LuauSubtypingAddOptPropsToUnsealedTables || (!isOptional(subProp.type) && !isAny)))
-                extraProperties.push_back(propName);
+            if (FFlag::LuauAnyInIsOptionalIsOptional)
+            {
+                if (superIter == superTable->props.end() && (FFlag::LuauSubtypingAddOptPropsToUnsealedTables || !isOptional(subProp.type)))
+                    extraProperties.push_back(propName);
+            }
+            else
+            {
+                bool isAny = log.is<AnyTypeVar>(log.follow(subProp.type));
+                if (superIter == superTable->props.end() && (FFlag::LuauSubtypingAddOptPropsToUnsealedTables || (!isOptional(subProp.type) && !isAny)))
+                    extraProperties.push_back(propName);
+            }
         }
 
         if (!extraProperties.empty())
@@ -1424,6 +1443,12 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
             if (innerState.errors.empty())
                 log.concat(std::move(innerState.log));
         }
+        else if (FFlag::LuauAnyInIsOptionalIsOptional && (!FFlag::LuauSubtypingAddOptPropsToUnsealedTables || subTable->state == TableState::Unsealed) && isOptional(prop.type))
+        // This is sound because unsealed table types are precise, so `{ p : T } <: { p : T, q : U? }`
+        // since if `t : { p : T }` then we are guaranteed that `t.q` is `nil`.
+        // TODO: if the supertype is written to, the subtype may no longer be precise (alias analysis?)
+        {
+        }
         else if ((!FFlag::LuauSubtypingAddOptPropsToUnsealedTables || subTable->state == TableState::Unsealed) && (isOptional(prop.type) || get<AnyTypeVar>(follow(prop.type))))
         // This is sound because unsealed table types are precise, so `{ p : T } <: { p : T, q : U? }`
         // since if `t : { p : T }` then we are guaranteed that `t.q` is `nil`.
@@ -1497,6 +1522,9 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
         else if (variance == Covariant)
         {
         }
+        else if (FFlag::LuauAnyInIsOptionalIsOptional && !FFlag::LuauSubtypingAddOptPropsToUnsealedTables && isOptional(prop.type))
+        {
+        }
         else if (!FFlag::LuauSubtypingAddOptPropsToUnsealedTables && (isOptional(prop.type) || get<AnyTypeVar>(follow(prop.type))))
         {
         }
@@ -1618,7 +1646,7 @@ void Unifier::tryUnifyTables(TypeId subTy, TypeId superTy, bool isIntersection)
 
 TypeId Unifier::widen(TypeId ty)
 {
-    if (!FFlag::LuauWidenIfSupertypeIsFree)
+    if (!FFlag::LuauWidenIfSupertypeIsFree2)
         return ty;
 
     Widen widen{types};
@@ -1627,10 +1655,21 @@ TypeId Unifier::widen(TypeId ty)
     return result.value_or(ty);
 }
 
+TypePackId Unifier::widen(TypePackId tp)
+{
+    if (!FFlag::LuauWidenIfSupertypeIsFree2)
+        return tp;
+
+    Widen widen{types};
+    std::optional<TypePackId> result = widen.substitute(tp);
+    // TODO: what does it mean for substitution to fail to widen?
+    return result.value_or(tp);
+}
+
 TypeId Unifier::deeplyOptional(TypeId ty, std::unordered_map<TypeId, TypeId> seen)
 {
     ty = follow(ty);
-    if (get<AnyTypeVar>(ty))
+    if (!FFlag::LuauAnyInIsOptionalIsOptional && get<AnyTypeVar>(ty))
         return ty;
     else if (isOptional(ty))
         return ty;
@@ -1744,7 +1783,10 @@ void Unifier::tryUnifyFreeTable(TypeId subTy, TypeId superTy)
     {
         if (auto subProp = findTablePropertyRespectingMeta(subTy, freeName))
         {
-            tryUnify_(freeProp.type, *subProp);
+            if (FFlag::LuauWidenIfSupertypeIsFree2)
+                tryUnify_(*subProp, freeProp.type);
+            else
+                tryUnify_(freeProp.type, *subProp);
 
             /*
              * TypeVars are commonly cyclic, so it is entirely possible

Ast/src/Parser.cpp

@@ -11,18 +11,11 @@
 LUAU_FASTINTVARIABLE(LuauRecursionLimit, 1000)
 LUAU_FASTINTVARIABLE(LuauParseErrorLimit, 100)
 LUAU_FASTFLAGVARIABLE(LuauParseSingletonTypes, false)
-LUAU_FASTFLAGVARIABLE(LuauParseAllHotComments, false)
 LUAU_FASTFLAGVARIABLE(LuauTableFieldFunctionDebugname, false)
 
 namespace Luau
 {
 
-static bool isComment(const Lexeme& lexeme)
-{
-    LUAU_ASSERT(!FFlag::LuauParseAllHotComments);
-    return lexeme.type == Lexeme::Comment || lexeme.type == Lexeme::BlockComment;
-}
-
 ParseError::ParseError(const Location& location, const std::string& message)
     : location(location)
     , message(message)
@@ -146,54 +139,13 @@ ParseResult Parser::parse(const char* buffer, size_t bufferSize, AstNameTable& n
 {
     LUAU_TIMETRACE_SCOPE("Parser::parse", "Parser");
 
-    Parser p(buffer, bufferSize, names, allocator, FFlag::LuauParseAllHotComments ? options : ParseOptions());
+    Parser p(buffer, bufferSize, names, allocator, options);
 
     try
     {
-        if (FFlag::LuauParseAllHotComments)
-        {
-            AstStatBlock* root = p.parseChunk();
+        AstStatBlock* root = p.parseChunk();
 
-            return ParseResult{root, std::move(p.hotcomments), std::move(p.parseErrors), std::move(p.commentLocations)};
-        }
-        else
-        {
-            std::vector<HotComment> hotcomments;
-
-            while (isComment(p.lexer.current()) || p.lexer.current().type == Lexeme::BrokenComment)
-            {
-                const char* text = p.lexer.current().data;
-                unsigned int length = p.lexer.current().length;
-
-                if (length && text[0] == '!')
-                {
-                    unsigned int end = length;
-                    while (end > 0 && isSpace(text[end - 1]))
-                        --end;
-
-                    hotcomments.push_back({true, p.lexer.current().location, std::string(text + 1, text + end)});
-                }
-
-                const Lexeme::Type type = p.lexer.current().type;
-                const Location loc = p.lexer.current().location;
-
-                if (options.captureComments)
-                    p.commentLocations.push_back(Comment{type, loc});
-
-                if (type == Lexeme::BrokenComment)
-                    break;
-
-                p.lexer.next();
-            }
-
-            p.lexer.setSkipComments(true);
-
-            p.options = options;
-
-            AstStatBlock* root = p.parseChunk();
-
-            return ParseResult{root, hotcomments, p.parseErrors, std::move(p.commentLocations)};
-        }
+        return ParseResult{root, std::move(p.hotcomments), std::move(p.parseErrors), std::move(p.commentLocations)};
     }
     catch (ParseError& err)
     {
@@ -225,10 +177,11 @@ Parser::Parser(const char* buffer, size_t bufferSize, AstNameTable& names, Alloc
     matchRecoveryStopOnToken.assign(Lexeme::Type::Reserved_END, 0);
     matchRecoveryStopOnToken[Lexeme::Type::Eof] = 1;
 
-    if (FFlag::LuauParseAllHotComments)
-        lexer.setSkipComments(true);
+    // required for lookahead() to work across a comment boundary and for nextLexeme() to work when captureComments is false
+    lexer.setSkipComments(true);
 
-    // read first lexeme
+    // read first lexeme (any hot comments get .header = true)
+    LUAU_ASSERT(hotcommentHeader);
     nextLexeme();
 
     // all hot comments parsed after the first non-comment lexeme are special in that they don't affect type checking / linting mode
@@ -2831,49 +2784,31 @@ void Parser::nextLexeme()
 {
     if (options.captureComments)
     {
-        if (FFlag::LuauParseAllHotComments)
+        Lexeme::Type type = lexer.next(/* skipComments= */ false).type;
+
+        while (type == Lexeme::BrokenComment || type == Lexeme::Comment || type == Lexeme::BlockComment)
         {
-            Lexeme::Type type = lexer.next(/* skipComments= */ false).type;
+            const Lexeme& lexeme = lexer.current();
+            commentLocations.push_back(Comment{lexeme.type, lexeme.location});
 
-            while (type == Lexeme::BrokenComment || type == Lexeme::Comment || type == Lexeme::BlockComment)
+            // Subtlety: Broken comments are weird because we record them as comments AND pass them to the parser as a lexeme.
+            // The parser will turn this into a proper syntax error.
+            if (lexeme.type == Lexeme::BrokenComment)
+                return;
+
+            // Comments starting with ! are called "hot comments" and contain directives for type checking / linting
+            if (lexeme.type == Lexeme::Comment && lexeme.length && lexeme.data[0] == '!')
             {
-                const Lexeme& lexeme = lexer.current();
-                commentLocations.push_back(Comment{lexeme.type, lexeme.location});
+                const char* text = lexeme.data;
 
-                // Subtlety: Broken comments are weird because we record them as comments AND pass them to the parser as a lexeme.
-                // The parser will turn this into a proper syntax error.
-                if (lexeme.type == Lexeme::BrokenComment)
-                    return;
+                unsigned int end = lexeme.length;
+                while (end > 0 && isSpace(text[end - 1]))
+                    --end;
 
-                // Comments starting with ! are called "hot comments" and contain directives for type checking / linting
-                if (lexeme.type == Lexeme::Comment && lexeme.length && lexeme.data[0] == '!')
-                {
-                    const char* text = lexeme.data;
-
-                    unsigned int end = lexeme.length;
-                    while (end > 0 && isSpace(text[end - 1]))
-                        --end;
-
-                    hotcomments.push_back({hotcommentHeader, lexeme.location, std::string(text + 1, text + end)});
-                }
-
-                type = lexer.next(/* skipComments= */ false).type;
-            }
-        }
-        else
-        {
-            while (true)
-            {
-                const Lexeme& lexeme = lexer.next(/*skipComments*/ false);
-                // Subtlety: Broken comments are weird because we record them as comments AND pass them to the parser as a lexeme.
-                // The parser will turn this into a proper syntax error.
-                if (lexeme.type == Lexeme::BrokenComment)
-                    commentLocations.push_back(Comment{lexeme.type, lexeme.location});
-                if (isComment(lexeme))
-                    commentLocations.push_back(Comment{lexeme.type, lexeme.location});
-                else
-                    return;
+                hotcomments.push_back({hotcommentHeader, lexeme.location, std::string(text + 1, text + end)});
             }
+
+            type = lexer.next(/* skipComments= */ false).type;
         }
     }
     else

Compiler/src/Builtins.cpp

@@ -4,8 +4,6 @@
 #include "Luau/Bytecode.h"
 #include "Luau/Compiler.h"
 
-LUAU_FASTFLAGVARIABLE(LuauCompileSelectBuiltin2, false)
-
 namespace Luau
 {
 namespace Compile
@@ -64,7 +62,7 @@ int getBuiltinFunctionId(const Builtin& builtin, const CompileOptions& options)
     if (builtin.isGlobal("unpack"))
         return LBF_TABLE_UNPACK;
 
-    if (FFlag::LuauCompileSelectBuiltin2 && builtin.isGlobal("select"))
+    if (builtin.isGlobal("select"))
         return LBF_SELECT_VARARG;
 
     if (builtin.object == "math")

Compiler/src/Compiler.cpp

@@ -15,8 +15,6 @@
 #include <bitset>
 #include <math.h>
 
-LUAU_FASTFLAG(LuauCompileSelectBuiltin2)
-
 namespace Luau
 {
 
@@ -265,7 +263,6 @@ struct Compiler
 
     void compileExprSelectVararg(AstExprCall* expr, uint8_t target, uint8_t targetCount, bool targetTop, bool multRet, uint8_t regs)
     {
-        LUAU_ASSERT(FFlag::LuauCompileSelectBuiltin2);
         LUAU_ASSERT(targetCount == 1);
         LUAU_ASSERT(!expr->self);
         LUAU_ASSERT(expr->args.size == 2 && expr->args.data[1]->is<AstExprVarargs>());
@@ -407,7 +404,6 @@ struct Compiler
 
         if (bfid == LBF_SELECT_VARARG)
         {
-            LUAU_ASSERT(FFlag::LuauCompileSelectBuiltin2);
             // Optimization: compile select(_, ...) as FASTCALL1; the builtin will read variadic arguments directly
             // note: for now we restrict this to single-return expressions since our runtime code doesn't deal with general cases
             if (multRet == false && targetCount == 1 && expr->args.size == 2 && expr->args.data[1]->is<AstExprVarargs>())

Sources.cmake

@@ -232,11 +232,18 @@ if(TARGET Luau.UnitTest)
         tests/Transpiler.test.cpp
         tests/TypeInfer.aliases.test.cpp
         tests/TypeInfer.annotations.test.cpp
+        tests/TypeInfer.anyerror.test.cpp
         tests/TypeInfer.builtins.test.cpp
         tests/TypeInfer.classes.test.cpp
         tests/TypeInfer.definitions.test.cpp
+        tests/TypeInfer.functions.test.cpp
         tests/TypeInfer.generics.test.cpp
         tests/TypeInfer.intersectionTypes.test.cpp
+        tests/TypeInfer.loops.test.cpp
+        tests/TypeInfer.modules.test.cpp
+        tests/TypeInfer.oop.test.cpp
+        tests/TypeInfer.operators.test.cpp
+        tests/TypeInfer.primitives.test.cpp
         tests/TypeInfer.provisional.test.cpp
         tests/TypeInfer.refinements.test.cpp
         tests/TypeInfer.singletons.test.cpp

VM/include/lua.h

@@ -172,9 +172,12 @@ LUA_API const char* lua_pushvfstring(lua_State* L, const char* fmt, va_list argp
 LUA_API LUA_PRINTF_ATTR(2, 3) const char* lua_pushfstringL(lua_State* L, const char* fmt, ...);
 LUA_API void lua_pushcclosurek(lua_State* L, lua_CFunction fn, const char* debugname, int nup, lua_Continuation cont);
 LUA_API void lua_pushboolean(lua_State* L, int b);
-LUA_API void lua_pushlightuserdata(lua_State* L, void* p);
 LUA_API int lua_pushthread(lua_State* L);
 
+LUA_API void lua_pushlightuserdata(lua_State* L, void* p);
+LUA_API void* lua_newuserdatatagged(lua_State* L, size_t sz, int tag);
+LUA_API void* lua_newuserdatadtor(lua_State* L, size_t sz, void (*dtor)(void*));
+
 /*
 ** get functions (Lua -> stack)
 */
@@ -189,8 +192,6 @@ LUA_API void lua_setreadonly(lua_State* L, int idx, int enabled);
 LUA_API int lua_getreadonly(lua_State* L, int idx);
 LUA_API void lua_setsafeenv(lua_State* L, int idx, int enabled);
 
-LUA_API void* lua_newuserdatatagged(lua_State* L, size_t sz, int tag);
-LUA_API void* lua_newuserdatadtor(lua_State* L, size_t sz, void (*dtor)(void*));
 LUA_API int lua_getmetatable(lua_State* L, int objindex);
 LUA_API void lua_getfenv(lua_State* L, int idx);
 
@@ -276,6 +277,14 @@ enum lua_GCOp
 
 LUA_API int lua_gc(lua_State* L, int what, int data);
 
+/*
+** memory statistics
+** all allocated bytes are attributed to the memory category of the running thread (0..LUA_MEMORY_CATEGORIES-1)
+*/
+
+LUA_API void lua_setmemcat(lua_State* L, int category);
+LUA_API size_t lua_totalbytes(lua_State* L, int category);
+
 /*
 ** miscellaneous functions
 */

VM/src/lapi.cpp

@@ -35,8 +35,8 @@ const char* luau_ident = "$Luau: Copyright (C) 2019-2022 Roblox Corporation $\n"
 
 static Table* getcurrenv(lua_State* L)
 {
-    if (L->ci == L->base_ci)  /* no enclosing function? */
-        return L->gt;         /* use global table as environment */
+    if (L->ci == L->base_ci) /* no enclosing function? */
+        return L->gt;        /* use global table as environment */
     else
         return curr_func(L)->env;
 }
@@ -1188,7 +1188,7 @@ void lua_concat(lua_State* L, int n)
 
 void* lua_newuserdatatagged(lua_State* L, size_t sz, int tag)
 {
-    api_check(L, unsigned(tag) < LUA_UTAG_LIMIT);
+    api_check(L, unsigned(tag) < LUA_UTAG_LIMIT || tag == UTAG_PROXY);
     luaC_checkGC(L);
     luaC_checkthreadsleep(L);
     Udata* u = luaU_newudata(L, sz, tag);
@@ -1317,7 +1317,7 @@ void lua_setuserdatadtor(lua_State* L, int tag, void (*dtor)(void*))
     L->global->udatagc[tag] = dtor;
 }
 
-LUA_API void lua_clonefunction(lua_State* L, int idx)
+void lua_clonefunction(lua_State* L, int idx)
 {
     StkId p = index2addr(L, idx);
     api_check(L, isLfunction(p));
@@ -1333,3 +1333,15 @@ lua_Callbacks* lua_callbacks(lua_State* L)
 {
     return &L->global->cb;
 }
+
+void lua_setmemcat(lua_State* L, int category)
+{
+    api_check(L, unsigned(category) < LUA_MEMORY_CATEGORIES);
+    L->activememcat = uint8_t(category);
+}
+
+size_t lua_totalbytes(lua_State* L, int category)
+{
+    api_check(L, category < LUA_MEMORY_CATEGORIES);
+    return category < 0 ? L->global->totalbytes : L->global->memcatbytes[category];
+}

VM/src/lbaselib.cpp

@@ -5,6 +5,7 @@
 #include "lstate.h"
 #include "lapi.h"
 #include "ldo.h"
+#include "ludata.h"
 
 #include <ctype.h>
 #include <stdio.h>
@@ -190,6 +191,7 @@ static int luaB_type(lua_State* L)
     luaL_checkany(L, 1);
     if (DFFlag::LuauMorePreciseLuaLTypeName)
     {
+        /* resulting name doesn't differentiate between userdata types */
         lua_pushstring(L, lua_typename(L, lua_type(L, 1)));
     }
     else
@@ -202,8 +204,16 @@ static int luaB_type(lua_State* L)
 static int luaB_typeof(lua_State* L)
 {
     luaL_checkany(L, 1);
-    const TValue* obj = luaA_toobject(L, 1);
-    lua_pushstring(L, luaT_objtypename(L, obj));
+    if (DFFlag::LuauMorePreciseLuaLTypeName)
+    {
+        /* resulting name returns __type if specified unless the input is a newproxy-created userdata */
+        lua_pushstring(L, luaL_typename(L, 1));
+    }
+    else
+    {
+        const TValue* obj = luaA_toobject(L, 1);
+        lua_pushstring(L, luaT_objtypename(L, obj));
+    }
     return 1;
 }
 
@@ -412,7 +422,7 @@ static int luaB_newproxy(lua_State* L)
 
     bool needsmt = lua_toboolean(L, 1);
 
-    lua_newuserdata(L, 0);
+    lua_newuserdatatagged(L, 0, UTAG_PROXY);
 
     if (needsmt)
     {

VM/src/lgc.h

@@ -9,9 +9,9 @@
 /*
 ** Default settings for GC tunables (settable via lua_gc)
 */
-#define LUAI_GCGOAL 200 /* 200% (allow heap to double compared to live heap size) */
+#define LUAI_GCGOAL 200    /* 200% (allow heap to double compared to live heap size) */
 #define LUAI_GCSTEPMUL 200 /* GC runs 'twice the speed' of memory allocation */
-#define LUAI_GCSTEPSIZE 1 /* GC runs every KB of memory allocation */
+#define LUAI_GCSTEPSIZE 1  /* GC runs every KB of memory allocation */
 
 /*
 ** Possible states of the Garbage Collector

VM/src/lmem.cpp

@@ -98,7 +98,7 @@
  */
 #if defined(__APPLE__)
 #define ABISWITCH(x64, ms32, gcc32) (sizeof(void*) == 8 ? x64 : gcc32)
-#elif defined(__i386__)
+#elif defined(__i386__) && !defined(_MSC_VER)
 #define ABISWITCH(x64, ms32, gcc32) (gcc32)
 #else
 // Android somehow uses a similar ABI to MSVC, *not* to iOS...

VM/src/lstring.cpp

@@ -53,7 +53,7 @@ void luaS_resize(lua_State* L, int newsize)
     {
         TString* p = tb->hash[i];
         while (p)
-        { /* for each node in the list */
+        {                            /* for each node in the list */
             TString* next = p->next; /* save next */
             unsigned int h = p->hash;
             int h1 = lmod(h, newsize); /* new position */

VM/src/ltable.cpp

@@ -24,6 +24,8 @@
 
 #include <string.h>
 
+LUAU_FASTFLAGVARIABLE(LuauTableRehashRework, false)
+
 // max size of both array and hash part is 2^MAXBITS
 #define MAXBITS 26
 #define MAXSIZE (1 << MAXBITS)
@@ -351,6 +353,22 @@ static void setnodevector(lua_State* L, Table* t, int size)
     t->lastfree = size; /* all positions are free */
 }
 
+static TValue* newkey(lua_State* L, Table* t, const TValue* key);
+
+static TValue* arrayornewkey(lua_State* L, Table* t, const TValue* key)
+{
+    if (ttisnumber(key))
+    {
+        int k;
+        double n = nvalue(key);
+        luai_num2int(k, n);
+        if (luai_numeq(cast_num(k), n) && cast_to(unsigned int, k - 1) < cast_to(unsigned int, t->sizearray))
+            return &t->array[k - 1];
+    }
+
+    return newkey(L, t, key);
+}
+
 static void resize(lua_State* L, Table* t, int nasize, int nhsize)
 {
     if (nasize > MAXSIZE || nhsize > MAXSIZE)
@@ -369,22 +387,50 @@ static void resize(lua_State* L, Table* t, int nasize, int nhsize)
         for (int i = nasize; i < oldasize; i++)
         {
             if (!ttisnil(&t->array[i]))
-                setobjt2t(L, luaH_setnum(L, t, i + 1), &t->array[i]);
+            {
+                if (FFlag::LuauTableRehashRework)
+                {
+                    TValue ok;
+                    setnvalue(&ok, cast_num(i + 1));
+                    setobjt2t(L, newkey(L, t, &ok), &t->array[i]);
+                }
+                else
+                {
+                    setobjt2t(L, luaH_setnum(L, t, i + 1), &t->array[i]);
+                }
+            }
         }
         /* shrink array */
         luaM_reallocarray(L, t->array, oldasize, nasize, TValue, t->memcat);
     }
     /* re-insert elements from hash part */
-    for (int i = twoto(oldhsize) - 1; i >= 0; i--)
+    if (FFlag::LuauTableRehashRework)
     {
-        LuaNode* old = nold + i;
-        if (!ttisnil(gval(old)))
+        for (int i = twoto(oldhsize) - 1; i >= 0; i--)
         {
-            TValue ok;
-            getnodekey(L, &ok, old);
-            setobjt2t(L, luaH_set(L, t, &ok), gval(old));
+            LuaNode* old = nold + i;
+            if (!ttisnil(gval(old)))
+            {
+                TValue ok;
+                getnodekey(L, &ok, old);
+                setobjt2t(L, arrayornewkey(L, t, &ok), gval(old));
+            }
         }
     }
+    else
+    {
+        for (int i = twoto(oldhsize) - 1; i >= 0; i--)
+        {
+            LuaNode* old = nold + i;
+            if (!ttisnil(gval(old)))
+            {
+                TValue ok;
+                getnodekey(L, &ok, old);
+                setobjt2t(L, luaH_set(L, t, &ok), gval(old));
+            }
+        }
+    }
+
     if (nold != dummynode)
         luaM_freearray(L, nold, twoto(oldhsize), LuaNode, t->memcat); /* free old array */
 }
@@ -482,7 +528,16 @@ static TValue* newkey(lua_State* L, Table* t, const TValue* key)
         if (n == NULL)
         {                               /* cannot find a free place? */
             rehash(L, t, key);          /* grow table */
-            return luaH_set(L, t, key); /* re-insert key into grown table */
+
+            if (!FFlag::LuauTableRehashRework)
+            {
+                return luaH_set(L, t, key); /* re-insert key into grown table */
+            }
+            else
+            {
+                // after rehash, numeric keys might be located in the new array part, but won't be found in the node part
+                return arrayornewkey(L, t, key);
+            }
         }
         LUAU_ASSERT(n != dummynode);
         TValue mk;

VM/src/ltm.cpp

@@ -4,6 +4,7 @@
 
 #include "lstate.h"
 #include "lstring.h"
+#include "ludata.h"
 #include "ltable.h"
 #include "lgc.h"
 
@@ -116,7 +117,7 @@ const TValue* luaT_gettmbyobj(lua_State* L, const TValue* o, TMS event)
 
 const TString* luaT_objtypenamestr(lua_State* L, const TValue* o)
 {
-    if (ttisuserdata(o) && uvalue(o)->tag && uvalue(o)->metatable)
+    if (ttisuserdata(o) && uvalue(o)->tag != UTAG_PROXY && uvalue(o)->metatable)
     {
         const TValue* type = luaH_getstr(uvalue(o)->metatable, L->global->tmname[TM_TYPE]);
 

VM/src/ludata.cpp

@@ -22,13 +22,11 @@ Udata* luaU_newudata(lua_State* L, size_t s, int tag)
 
 void luaU_freeudata(lua_State* L, Udata* u, lua_Page* page)
 {
-    LUAU_ASSERT(u->tag < LUA_UTAG_LIMIT || u->tag == UTAG_IDTOR);
-
     void (*dtor)(void*) = nullptr;
-    if (u->tag == UTAG_IDTOR)
-        memcpy(&dtor, &u->data + u->len - sizeof(dtor), sizeof(dtor));
-    else if (u->tag)
+    if (u->tag < LUA_UTAG_LIMIT)
         dtor = L->global->udatagc[u->tag];
+    else if (u->tag == UTAG_IDTOR)
+        memcpy(&dtor, &u->data + u->len - sizeof(dtor), sizeof(dtor));
 
     if (dtor)
         dtor(u->data);

VM/src/ludata.h

@@ -7,6 +7,9 @@
 /* special tag value is used for user data with inline dtors */
 #define UTAG_IDTOR LUA_UTAG_LIMIT
 
+/* special tag value is used for newproxy-created user data (all other user data objects are host-exposed) */
+#define UTAG_PROXY (LUA_UTAG_LIMIT + 1)
+
 #define sizeudata(len) (offsetof(Udata, data) + len)
 
 LUAI_FUNC Udata* luaU_newudata(lua_State* L, size_t s, int tag);

VM/src/lvmexecute.cpp

@@ -77,7 +77,7 @@
         if (LUAU_UNLIKELY(!!interrupt)) \
         { /* the interrupt hook is called right before we advance pc */ \
             VM_PROTECT(L->ci->savedpc++; interrupt(L, -1)); \
-	    if (L->status != 0) \
+            if (L->status != 0) \
             { \
                 L->ci->savedpc--; \
                 goto exit; \

tests/Autocomplete.test.cpp

@@ -2755,4 +2755,166 @@ local abc = b@1
     CHECK(ac.entryMap["bar"].parens == ParenthesesRecommendation::CursorInside);
 }
 
+TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls_on_class")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    loadDefinition(R"(
+declare class Foo
+    function one(self): number
+    two: () -> number
+end
+    )");
+
+    {
+        check(R"(
+local t: Foo
+t:@1
+        )");
+
+        auto ac = autocomplete('1');
+
+        REQUIRE(ac.entryMap.count("one"));
+        REQUIRE(ac.entryMap.count("two"));
+        CHECK(!ac.entryMap["one"].wrongIndexType);
+        CHECK(ac.entryMap["two"].wrongIndexType);
+    }
+
+    {
+        check(R"(
+local t: Foo
+t.@1
+        )");
+
+        auto ac = autocomplete('1');
+
+        REQUIRE(ac.entryMap.count("one"));
+        REQUIRE(ac.entryMap.count("two"));
+        CHECK(ac.entryMap["one"].wrongIndexType);
+        CHECK(!ac.entryMap["two"].wrongIndexType);
+    }
+}
+
+TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+local t = {}
+function t.m() end
+t:@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("m"));
+    CHECK(ac.entryMap["m"].wrongIndexType);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls_2")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+local f: (() -> number) & ((number) -> number) = function(x: number?) return 2 end
+local t = {}
+t.f = f
+t:@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("f"));
+    CHECK(ac.entryMap["f"].wrongIndexType);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "no_incompatible_self_calls_provisional")
+{
+    check(R"(
+local t = {}
+function t.m(x: typeof(t)) end
+t:@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("m"));
+    // We can make changes to mark this as a wrong way to call even though it's compatible
+    CHECK(!ac.entryMap["m"].wrongIndexType);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "string_prim_self_calls_are_fine")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+local s = "hello"
+s:@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("byte"));
+    CHECK(ac.entryMap["byte"].wrongIndexType == false);
+    REQUIRE(ac.entryMap.count("char"));
+    CHECK(ac.entryMap["char"].wrongIndexType == true);
+    REQUIRE(ac.entryMap.count("sub"));
+    CHECK(ac.entryMap["sub"].wrongIndexType == false);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "string_prim_non_self_calls_are_avoided")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+local s = "hello"
+s.@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("byte"));
+    CHECK(ac.entryMap["byte"].wrongIndexType == true);
+    REQUIRE(ac.entryMap.count("char"));
+    CHECK(ac.entryMap["char"].wrongIndexType == false);
+    REQUIRE(ac.entryMap.count("sub"));
+    CHECK(ac.entryMap["sub"].wrongIndexType == true);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "string_library_non_self_calls_are_fine")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+string.@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("byte"));
+    CHECK(ac.entryMap["byte"].wrongIndexType == false);
+    REQUIRE(ac.entryMap.count("char"));
+    CHECK(ac.entryMap["char"].wrongIndexType == false);
+    REQUIRE(ac.entryMap.count("sub"));
+    CHECK(ac.entryMap["sub"].wrongIndexType == false);
+}
+
+TEST_CASE_FIXTURE(ACFixture, "string_library_self_calls_are_invalid")
+{
+    ScopedFastFlag selfCallAutocompleteFix{"LuauSelfCallAutocompleteFix", true};
+
+    check(R"(
+string:@1
+    )");
+
+    auto ac = autocomplete('1');
+
+    REQUIRE(ac.entryMap.count("byte"));
+    CHECK(ac.entryMap["byte"].wrongIndexType == true);
+    REQUIRE(ac.entryMap.count("char"));
+    CHECK(ac.entryMap["char"].wrongIndexType == true);
+    REQUIRE(ac.entryMap.count("sub"));
+    CHECK(ac.entryMap["sub"].wrongIndexType == true);
+}
+
 TEST_SUITE_END();

tests/Compiler.test.cpp

@@ -2819,8 +2819,6 @@ RETURN R1 -1
 
 TEST_CASE("FastcallSelect")
 {
-    ScopedFastFlag sff("LuauCompileSelectBuiltin2", true);
-
     // select(_, ...) compiles to a builtin call
     CHECK_EQ("\n" + compileFunction0("return (select('#', ...))"), R"(
 LOADK R1 K0

tests/Conformance.test.cpp

@@ -569,6 +569,11 @@ TEST_CASE("Debugger")
                 CHECK(lua_tointeger(L, -1) == 50);
                 lua_pop(L, 1);
 
+                int v = lua_getargument(L, 0, 2);
+                REQUIRE(v);
+                CHECK(lua_tointeger(L, -1) == 42);
+                lua_pop(L, 1);
+
                 // test lua_getlocal
                 const char* l = lua_getlocal(L, 0, 1);
                 REQUIRE(l);
@@ -652,31 +657,6 @@ TEST_CASE("SameHash")
     CHECK(luaS_hash(buf + 1, 120) == luaS_hash(buf + 2, 120));
 }
 
-TEST_CASE("InlineDtor")
-{
-    static int dtorhits = 0;
-
-    dtorhits = 0;
-
-    {
-        StateRef globalState(luaL_newstate(), lua_close);
-        lua_State* L = globalState.get();
-
-        void* u1 = lua_newuserdatadtor(L, 4, [](void* data) {
-            dtorhits += *(int*)data;
-        });
-
-        void* u2 = lua_newuserdatadtor(L, 1, [](void* data) {
-            dtorhits += *(char*)data;
-        });
-
-        *(int*)u1 = 39;
-        *(char*)u2 = 3;
-    }
-
-    CHECK(dtorhits == 42);
-}
-
 TEST_CASE("Reference")
 {
     static int dtorhits = 0;
@@ -969,7 +949,7 @@ TEST_CASE("StringConversion")
 TEST_CASE("GCDump")
 {
     // internal function, declared in lgc.h - not exposed via lua.h
-    extern void luaC_dump(lua_State* L, void* file, const char* (*categoryName)(lua_State* L, uint8_t memcat));
+    extern void luaC_dump(lua_State * L, void* file, const char* (*categoryName)(lua_State * L, uint8_t memcat));
 
     StateRef globalState(luaL_newstate(), lua_close);
     lua_State* L = globalState.get();
@@ -1015,4 +995,114 @@ TEST_CASE("GCDump")
     fclose(f);
 }
 
+TEST_CASE("Interrupt")
+{
+    static const int expectedhits[] = {
+        2,
+        9,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        5,
+        6,
+        11,
+    };
+    static int index;
+
+    index = 0;
+
+    runConformance(
+        "interrupt.lua",
+        [](lua_State* L) {
+            auto* cb = lua_callbacks(L);
+
+            // note: for simplicity here we setup the interrupt callback once
+            // however, this carries a noticeable performance cost. in a real application,
+            // it's advised to set interrupt callback on a timer from a different thread,
+            // and set it back to nullptr once the interrupt triggered.
+            cb->interrupt = [](lua_State* L, int gc) {
+                if (gc >= 0)
+                    return;
+
+                CHECK(index < int(std::size(expectedhits)));
+
+                lua_Debug ar = {};
+                lua_getinfo(L, 0, "l", &ar);
+
+                CHECK(ar.currentline == expectedhits[index]);
+
+                index++;
+
+                // check that we can yield inside an interrupt
+                if (index == 5)
+                    lua_yield(L, 0);
+            };
+        },
+        [](lua_State* L) {
+            CHECK(index == 5); // a single yield point
+        });
+
+    CHECK(index == int(std::size(expectedhits)));
+}
+
+TEST_CASE("UserdataApi")
+{
+    static int dtorhits = 0;
+
+    dtorhits = 0;
+
+    StateRef globalState(luaL_newstate(), lua_close);
+    lua_State* L = globalState.get();
+
+    // setup dtor for tag 42 (created later)
+    lua_setuserdatadtor(L, 42, [](void* data) {
+        dtorhits += *(int*)data;
+    });
+
+    // light user data
+    int lud;
+    lua_pushlightuserdata(L, &lud);
+
+    CHECK(lua_touserdata(L, -1) == &lud);
+    CHECK(lua_topointer(L, -1) == &lud);
+
+    // regular user data
+    int* ud1 = (int*)lua_newuserdata(L, 4);
+    *ud1 = 42;
+
+    CHECK(lua_touserdata(L, -1) == ud1);
+    CHECK(lua_topointer(L, -1) == ud1);
+
+    // tagged user data
+    int* ud2 = (int*)lua_newuserdatatagged(L, 4, 42);
+    *ud2 = -4;
+
+    CHECK(lua_touserdatatagged(L, -1, 42) == ud2);
+    CHECK(lua_touserdatatagged(L, -1, 41) == nullptr);
+    CHECK(lua_userdatatag(L, -1) == 42);
+
+    // user data with inline dtor
+    void* ud3 = lua_newuserdatadtor(L, 4, [](void* data) {
+        dtorhits += *(int*)data;
+    });
+
+    void* ud4 = lua_newuserdatadtor(L, 1, [](void* data) {
+        dtorhits += *(char*)data;
+    });
+
+    *(int*)ud3 = 43;
+    *(char*)ud4 = 3;
+
+    globalState.reset();
+
+    CHECK(dtorhits == 42);
+}
+
 TEST_SUITE_END();

tests/Linter.test.cpp

@@ -1667,8 +1667,6 @@ _ = (math.random() < 0.5 and false) or 42 -- currently ignored
 
 TEST_CASE_FIXTURE(Fixture, "WrongComment")
 {
-    ScopedFastFlag sff("LuauParseAllHotComments", true);
-
     LintResult result = lint(R"(
 --!strict
 --!struct

tests/Module.test.cpp

@@ -248,10 +248,12 @@ TEST_CASE_FIXTURE(Fixture, "clone_seal_free_tables")
 
 TEST_CASE_FIXTURE(Fixture, "clone_self_property")
 {
+    ScopedFastFlag sff{"LuauAnyInIsOptionalIsOptional", true};
+
     fileResolver.source["Module/A"] = R"(
         --!nonstrict
         local a = {}
-        function a:foo(x)
+        function a:foo(x: number)
             return -x;
         end
         return a;
@@ -267,10 +269,10 @@ TEST_CASE_FIXTURE(Fixture, "clone_self_property")
     )";
 
     result = frontend.check("Module/B");
-    LUAU_REQUIRE_ERRORS(result);
 
-    CHECK_EQ(toString(result.errors[0]), "This function was declared to accept self, but you did not pass enough arguments. Use a colon instead of a "
-                                         "dot or pass 1 extra nil to suppress this warning");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("This function must be called with self. Did you mean to use a colon instead of a dot?", toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "clone_recursion_limit")

tests/NonstrictMode.test.cpp

@@ -126,6 +126,8 @@ TEST_CASE_FIXTURE(Fixture, "parameters_having_type_any_are_optional")
 
 TEST_CASE_FIXTURE(Fixture, "local_tables_are_not_any")
 {
+    ScopedFastFlag sff{"LuauAnyInIsOptionalIsOptional", true};
+
     CheckResult result = check(R"(
         --!nonstrict
         local T = {}
@@ -136,31 +138,25 @@ TEST_CASE_FIXTURE(Fixture, "local_tables_are_not_any")
         T:staticmethod()
     )");
 
-    LUAU_REQUIRE_ERROR_COUNT(2, result);
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
 
-    CHECK(std::any_of(result.errors.begin(), result.errors.end(), [](const TypeError& e) {
-        return get<FunctionDoesNotTakeSelf>(e);
-    }));
-    CHECK(std::any_of(result.errors.begin(), result.errors.end(), [](const TypeError& e) {
-        return get<FunctionRequiresSelf>(e);
-    }));
+    CHECK_EQ("This function does not take self. Did you mean to use a dot instead of a colon?", toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "offer_a_hint_if_you_use_a_dot_instead_of_a_colon")
 {
+    ScopedFastFlag sff{"LuauAnyInIsOptionalIsOptional", true};
+
     CheckResult result = check(R"(
         --!nonstrict
         local T = {}
-        function T:method() end
-        T.method()
+        function T:method(x: number) end
+        T.method(5)
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
 
-    auto e = get<FunctionRequiresSelf>(result.errors[0]);
-    REQUIRE(e != nullptr);
-
-    REQUIRE_EQ(1, e->requiredExtraNils);
+    CHECK_EQ("This function must be called with self. Did you mean to use a colon instead of a dot?", toString(result.errors[0]));
 }
 
 TEST_CASE_FIXTURE(Fixture, "table_props_are_any")

tests/TypeInfer.aliases.test.cpp

@@ -676,4 +676,25 @@ TEST_CASE_FIXTURE(Fixture, "forward_declared_alias_is_not_clobbered_by_prior_uni
     LUAU_REQUIRE_NO_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "recursive_types_restriction_ok")
+{
+    CheckResult result = check(R"(
+        type Tree<T> = { data: T, children: {Tree<T>} }
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "recursive_types_restriction_not_ok")
+{
+    ScopedFastFlag sff{"LuauRecursiveTypeParameterRestriction", true};
+
+    CheckResult result = check(R"(
+        -- this would be an infinite type if we allowed it
+        type Tree<T> = { data: T, children: {Tree<{T}>} }
+    )");
+
+    LUAU_REQUIRE_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.anyerror.test.cpp

@@ -0,0 +1,335 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferAnyError");
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_returns_any")
+{
+    CheckResult result = check(R"(
+        function bar(): any
+            return true
+        end
+
+        local a
+        for b in bar do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(typeChecker.anyType, requireType("a"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_returns_any2")
+{
+    CheckResult result = check(R"(
+        function bar(): any
+            return true
+        end
+
+        local a
+        for b in bar() do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("any", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_any")
+{
+    CheckResult result = check(R"(
+        local bar: any
+
+        local a
+        for b in bar do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("any", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_any2")
+{
+    CheckResult result = check(R"(
+        local bar: any
+
+        local a
+        for b in bar() do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("any", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_error")
+{
+    CheckResult result = check(R"(
+        local a
+        for b in bar do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("*unknown*", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_iterator_is_error2")
+{
+    CheckResult result = check(R"(
+        function bar(c) return c end
+
+        local a
+        for b in bar() do
+            a = b
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("*unknown*", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "length_of_error_type_does_not_produce_an_error")
+{
+    CheckResult result = check(R"(
+        local l = #this_is_not_defined
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "indexing_error_type_does_not_produce_an_error")
+{
+    CheckResult result = check(R"(
+        local originalReward = unknown.Parent.Reward:GetChildren()[1]
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "dot_on_error_type_does_not_produce_an_error")
+{
+    CheckResult result = check(R"(
+        local foo = (true).x
+        foo.x = foo.y
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "any_type_propagates")
+{
+    CheckResult result = check(R"(
+        local foo: any
+        local bar = foo:method("argument")
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("any", toString(requireType("bar")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "can_subscript_any")
+{
+    CheckResult result = check(R"(
+        local foo: any
+        local bar = foo[5]
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("any", toString(requireType("bar")));
+}
+
+// Not strictly correct: metatables permit overriding this
+TEST_CASE_FIXTURE(Fixture, "can_get_length_of_any")
+{
+    CheckResult result = check(R"(
+        local foo: any = {}
+        local bar = #foo
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(PrimitiveTypeVar::Number, getPrimitiveType(requireType("bar")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "assign_prop_to_table_by_calling_any_yields_any")
+{
+    CheckResult result = check(R"(
+        local f: any
+        local T = {}
+
+        T.prop = f()
+
+        return T
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    TableTypeVar* ttv = getMutable<TableTypeVar>(requireType("T"));
+    REQUIRE(ttv);
+    REQUIRE(ttv->props.count("prop"));
+
+    REQUIRE_EQ("any", toString(ttv->props["prop"].type));
+}
+
+TEST_CASE_FIXTURE(Fixture, "quantify_any_does_not_bind_to_itself")
+{
+    CheckResult result = check(R"(
+        local A : any
+        function A.B() end
+        A:C()
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    TypeId aType = requireType("A");
+    CHECK_EQ(aType, typeChecker.anyType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "calling_error_type_yields_error")
+{
+    CheckResult result = check(R"(
+        local a = unknown.Parent.Reward.GetChildren()
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    UnknownSymbol* err = get<UnknownSymbol>(result.errors[0]);
+    REQUIRE(err != nullptr);
+
+    CHECK_EQ("unknown", err->name);
+
+    CHECK_EQ("*unknown*", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "chain_calling_error_type_yields_error")
+{
+    CheckResult result = check(R"(
+        local a = Utility.Create "Foo" {}
+    )");
+
+    CHECK_EQ("*unknown*", toString(requireType("a")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "replace_every_free_type_when_unifying_a_complex_function_with_any")
+{
+    CheckResult result = check(R"(
+        local a: any
+        local b
+        for _, i in pairs(a) do
+            b = i
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ("any", toString(requireType("b")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "call_to_any_yields_any")
+{
+    CheckResult result = check(R"(
+        local a: any
+        local b = a()
+    )");
+
+    REQUIRE_EQ("any", toString(requireType("b")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "CheckMethodsOfAny")
+{
+    CheckResult result = check(R"(
+local x: any = {}
+function x:y(z: number)
+    local s: string = z
+end
+)");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "CheckMethodsOfError")
+{
+    CheckResult result = check(R"(
+local x = (true).foo
+function x:y(z: number)
+    local s: string = z
+end
+)");
+
+    LUAU_REQUIRE_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "metatable_of_any_can_be_a_table")
+{
+    CheckResult result = check(R"(
+--!strict
+local T: any
+T = {}
+T.__index = T
+function T.new(...)
+    local self = {}
+    setmetatable(self, T)
+    self:construct(...)
+    return self
+end
+function T:construct(index)
+end
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "type_error_addition")
+{
+    CheckResult result = check(R"(
+--!strict
+local foo = makesandwich()
+local bar = foo.nutrition + 100
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    // We should definitely get this error
+    CHECK_EQ("Unknown global 'makesandwich'", toString(result.errors[0]));
+    // We get this error if makesandwich() returns a free type
+    // CHECK_EQ("Unknown type used in + operation; consider adding a type annotation to 'foo'", toString(result.errors[1]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "prop_access_on_any_with_other_options")
+{
+    CheckResult result = check(R"(
+        local function f(thing: any | string)
+            local foo = thing.SomeRandomKey
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.builtins.test.cpp

@@ -871,6 +871,7 @@ TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types")
     ScopedFastFlag sff[]{
         {"LuauAssertStripsFalsyTypes", true},
         {"LuauDiscriminableUnions2", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
     };
 
     CheckResult result = check(R"(
@@ -879,6 +880,26 @@ TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types")
         end
     )");
 
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ("((boolean | number)?) -> boolean | number", toString(requireType("f")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "assert_removes_falsy_types2")
+{
+    ScopedFastFlag sff[]{
+        {"LuauParseSingletonTypes", true},
+        {"LuauSingletonTypes", true},
+        {"LuauAssertStripsFalsyTypes", true},
+        {"LuauDiscriminableUnions2", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
+    };
+
+    CheckResult result = check(R"(
+        local function f(x: (number | boolean)?): number | true
+            return assert(x)
+        end
+    )");
+
     LUAU_REQUIRE_NO_ERRORS(result);
     CHECK_EQ("((boolean | number)?) -> number | true", toString(requireType("f")));
 }
@@ -958,4 +979,43 @@ a:b({})
     CHECK_EQ(result.errors[1], (TypeError{Location{{3, 0}, {3, 5}}, CountMismatch{2, 1}}));
 }
 
+TEST_CASE_FIXTURE(Fixture, "typeof_unresolved_function")
+{
+    CheckResult result = check(R"(
+local function f(a: typeof(f)) end
+)");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Unknown global 'f'", toString(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "no_persistent_typelevel_change")
+{
+    TypeId mathTy = requireType(typeChecker.globalScope, "math");
+    REQUIRE(mathTy);
+    TableTypeVar* ttv = getMutable<TableTypeVar>(mathTy);
+    REQUIRE(ttv);
+    const FunctionTypeVar* ftv = get<FunctionTypeVar>(ttv->props["frexp"].type);
+    REQUIRE(ftv);
+    auto original = ftv->level;
+
+    CheckResult result = check("local a = math.frexp");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK(ftv->level.level == original.level);
+    CHECK(ftv->level.subLevel == original.subLevel);
+}
+
+TEST_CASE_FIXTURE(Fixture, "global_singleton_types_are_sealed")
+{
+    CheckResult result = check(R"(
+local function f(x: string)
+    local p = x:split('a')
+    p = table.pack(table.unpack(p, 1, #p - 1))
+    return p
+end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.definitions.test.cpp

@@ -293,4 +293,22 @@ TEST_CASE_FIXTURE(Fixture, "documentation_symbols_dont_attach_to_persistent_type
     CHECK_EQ(ty->type->documentationSymbol, std::nullopt);
 }
 
+TEST_CASE_FIXTURE(Fixture, "single_class_type_identity_in_global_types")
+{
+    ScopedFastFlag luauCloneDeclaredGlobals{"LuauCloneDeclaredGlobals", true};
+
+    loadDefinition(R"(
+declare class Cls
+end
+
+declare GetCls: () -> (Cls)
+    )");
+
+    CheckResult result = check(R"(
+local s : Cls = GetCls()
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.generics.test.cpp

@@ -1,6 +1,9 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #include "Luau/TypeInfer.h"
 #include "Luau/TypeVar.h"
+#include "Luau/Scope.h"
+
+#include <algorithm>
 
 #include "Fixture.h"
 
@@ -830,5 +833,303 @@ wrapper(test2, 1, "", 3)
         CHECK_EQ(toString(result.errors[0]), R"(Argument count mismatch. Function expects 1 argument, but 4 are specified)");
 }
 
+TEST_CASE_FIXTURE(Fixture, "generic_function")
+{
+    CheckResult result = check(R"(
+        function id(x) return x end
+        local a = id(55)
+        local b = id(nil)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.numberType, *requireType("a"));
+    CHECK_EQ(*typeChecker.nilType, *requireType("b"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "generic_table_method")
+{
+    CheckResult result = check(R"(
+        local T = {}
+
+        function T:bar(i)
+            return i
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    TypeId tType = requireType("T");
+    TableTypeVar* tTable = getMutable<TableTypeVar>(tType);
+    REQUIRE(tTable != nullptr);
+
+    TypeId barType = tTable->props["bar"].type;
+    REQUIRE(barType != nullptr);
+
+    const FunctionTypeVar* ftv = get<FunctionTypeVar>(follow(barType));
+    REQUIRE_MESSAGE(ftv != nullptr, "Should be a function: " << *barType);
+
+    std::vector<TypeId> args = flatten(ftv->argTypes).first;
+    TypeId argType = args.at(1);
+
+    CHECK_MESSAGE(get<Unifiable::Generic>(argType), "Should be generic: " << *barType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "correctly_instantiate_polymorphic_member_functions")
+{
+    CheckResult result = check(R"(
+        local T = {}
+
+        function T:foo()
+            return T:bar(5)
+        end
+
+        function T:bar(i)
+            return i
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    dumpErrors(result);
+
+    const TableTypeVar* t = get<TableTypeVar>(requireType("T"));
+    REQUIRE(t != nullptr);
+
+    std::optional<Property> fooProp = get(t->props, "foo");
+    REQUIRE(bool(fooProp));
+
+    const FunctionTypeVar* foo = get<FunctionTypeVar>(follow(fooProp->type));
+    REQUIRE(bool(foo));
+
+    std::optional<TypeId> ret_ = first(foo->retType);
+    REQUIRE(bool(ret_));
+    TypeId ret = follow(*ret_);
+
+    REQUIRE_EQ(getPrimitiveType(ret), PrimitiveTypeVar::Number);
+}
+
+/*
+ * We had a bug in instantiation where the argument types of 'f' and 'g' would be inferred as
+ * f {+ method: function(<CYCLE>): (t2, T3...) +}
+ * g {+ method: function({+ method: function(<CYCLE>): (t2, T3...) +}): (t5, T6...) +}
+ *
+ * The type of 'g' is totally wrong as t2 and t5 should be unified, as should T3 with T6.
+ *
+ * The correct unification of the argument to 'g' is
+ *
+ * {+ method: function(<CYCLE>): (t5, T6...) +}
+ */
+TEST_CASE_FIXTURE(Fixture, "instantiate_cyclic_generic_function")
+{
+    auto result = check(R"(
+        function f(o)
+            o:method()
+        end
+
+        function g(o)
+            f(o)
+        end
+    )");
+
+    TypeId g = requireType("g");
+    const FunctionTypeVar* gFun = get<FunctionTypeVar>(g);
+    REQUIRE(gFun != nullptr);
+
+    auto optionArg = first(gFun->argTypes);
+    REQUIRE(bool(optionArg));
+
+    TypeId arg = follow(*optionArg);
+    const TableTypeVar* argTable = get<TableTypeVar>(arg);
+    REQUIRE(argTable != nullptr);
+
+    std::optional<Property> methodProp = get(argTable->props, "method");
+    REQUIRE(bool(methodProp));
+
+    const FunctionTypeVar* methodFunction = get<FunctionTypeVar>(methodProp->type);
+    REQUIRE(methodFunction != nullptr);
+
+    std::optional<TypeId> methodArg = first(methodFunction->argTypes);
+    REQUIRE(bool(methodArg));
+
+    REQUIRE_EQ(follow(*methodArg), follow(arg));
+}
+
+TEST_CASE_FIXTURE(Fixture, "instantiate_generic_function_in_assignments")
+{
+    CheckResult result = check(R"(
+        function foo(a, b)
+            return a(b)
+        end
+
+        function bar()
+            local c: ((number)->number, number)->number = foo -- no error
+            c = foo -- no error
+            local d: ((number)->number, string)->number = foo -- error from arg 2 (string) not being convertable to number from the call a(b)
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    REQUIRE(tm);
+    CHECK_EQ("((number) -> number, string) -> number", toString(tm->wantedType));
+    CHECK_EQ("((number) -> number, number) -> number", toString(tm->givenType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "instantiate_generic_function_in_assignments2")
+{
+    CheckResult result = check(R"(
+        function foo(a, b)
+            return a(b)
+        end
+
+        function bar()
+            local _: (string, string)->number = foo -- string cannot be converted to (string)->number
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    REQUIRE(tm);
+    CHECK_EQ("(string, string) -> number", toString(tm->wantedType));
+    CHECK_EQ("((string) -> number, string) -> number", toString(*tm->givenType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "self_recursive_instantiated_param")
+{
+    ScopedFastFlag sff{"LuauOnlyMutateInstantiatedTables", true};
+
+    // Mutability in type function application right now can create strange recursive types
+    CheckResult result = check(R"(
+type Table = { a: number }
+type Self<T> = T
+local a: Self<Table>
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ(toString(requireType("a")), "Table");
+}
+
+TEST_CASE_FIXTURE(Fixture, "no_stack_overflow_from_quantifying")
+{
+    CheckResult result = check(R"(
+        function _(l0:t0): (any, ()->())
+        end
+
+        type t0 = t0 | {}
+    )");
+
+    CHECK_LE(0, result.errors.size());
+
+    std::optional<TypeFun> t0 = getMainModule()->getModuleScope()->lookupType("t0");
+    REQUIRE(t0);
+    CHECK_EQ("*unknown*", toString(t0->type));
+
+    auto it = std::find_if(result.errors.begin(), result.errors.end(), [](TypeError& err) {
+        return get<OccursCheckFailed>(err);
+    });
+    CHECK(it != result.errors.end());
+}
+
+TEST_CASE_FIXTURE(Fixture, "infer_generic_function_function_argument")
+{
+    ScopedFastFlag sff{"LuauUnsealedTableLiteral", true};
+
+    CheckResult result = check(R"(
+local function sum<a>(x: a, y: a, f: (a, a) -> a) return f(x, y) end
+return sum(2, 3, function(a, b) return a + b end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    result = check(R"(
+local function map<a, b>(arr: {a}, f: (a) -> b) local r = {} for i,v in ipairs(arr) do table.insert(r, f(v)) end return r end
+local a = {1, 2, 3}
+local r = map(a, function(a) return a + a > 100 end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    REQUIRE_EQ("{boolean}", toString(requireType("r")));
+
+    check(R"(
+local function foldl<a, b>(arr: {a}, init: b, f: (b, a) -> b) local r = init for i,v in ipairs(arr) do r = f(r, v) end return r end
+local a = {1, 2, 3}
+local r = foldl(a, {s=0,c=0}, function(a, b) return {s = a.s + b, c = a.c + 1} end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    REQUIRE_EQ("{ c: number, s: number }", toString(requireType("r")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "infer_generic_function_function_argument_overloaded")
+{
+    CheckResult result = check(R"(
+local function g1<T>(a: T, f: (T) -> T) return f(a) end
+local function g2<T>(a: T, b: T, f: (T, T) -> T) return f(a, b) end
+
+local g12: typeof(g1) & typeof(g2)
+
+g12(1, function(x) return x + x end)
+g12(1, 2, function(x, y) return x + y end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    result = check(R"(
+local function g1<T>(a: T, f: (T) -> T) return f(a) end
+local function g2<T>(a: T, b: T, f: (T, T) -> T) return f(a, b) end
+
+local g12: typeof(g1) & typeof(g2)
+
+g12({x=1}, function(x) return {x=-x.x} end)
+g12({x=1}, {x=2}, function(x, y) return {x=x.x + y.x} end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "infer_generic_lib_function_function_argument")
+{
+    CheckResult result = check(R"(
+local a = {{x=4}, {x=7}, {x=1}}
+table.sort(a, function(x, y) return x.x < y.x end)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "do_not_infer_generic_functions")
+{
+    CheckResult result = check(R"(
+local function sum<a>(x: a, y: a, f: (a, a) -> a) return f(x, y) end
+
+local function sumrec(f: typeof(sum))
+    return sum(2, 3, function(a, b) return a + b end)
+end
+
+local b = sumrec(sum) -- ok
+local c = sumrec(function(x, y, f) return f(x, y) end) -- type binders are not inferred
+    )");
+
+    LUAU_REQUIRE_ERRORS(result);
+    CHECK_EQ("Type '(a, b, (a, b) -> (c...)) -> (c...)' could not be converted into '<a>(a, a, (a, a) -> a) -> a'; different number of generic type "
+             "parameters",
+        toString(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "substitution_with_bound_table")
+{
+    CheckResult result = check(R"(
+type A = { x: number }
+local a: A = { x = 1 }
+local b = a
+type B = typeof(b)
+type X<T> = T
+local c: X<B>
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
 
 TEST_SUITE_END();

tests/TypeInfer.intersectionTypes.test.cpp

@@ -377,4 +377,32 @@ local b: number = a
     CHECK_EQ(toString(result.errors[0]), R"(Type 'X & Y & Z' could not be converted into 'number'; none of the intersection parts are compatible)");
 }
 
+TEST_CASE_FIXTURE(Fixture, "overload_is_not_a_function")
+{
+    check(R"(
+--!nonstrict
+function _(...):((typeof(not _))&(typeof(not _)))&((typeof(not _))&(typeof(not _)))
+_(...)(setfenv,_,not _,"")[_] = nil
+end
+do end
+_(...)(...,setfenv,_):_G()
+)");
+}
+
+TEST_CASE_FIXTURE(Fixture, "no_stack_overflow_from_flattenintersection")
+{
+    CheckResult result = check(R"(
+        local l0,l0
+        repeat
+        type t0 = ((any)|((any)&((any)|((any)&((any)|(any))))))&(t0)
+        function _(l0):(t0)&(t0)
+        while nil do
+        end
+        end
+        until _(_)(_)._
+    )");
+
+    CHECK_LE(0, result.errors.size());
+}
+
 TEST_SUITE_END();

tests/TypeInfer.loops.test.cpp

@@ -0,0 +1,473 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferLoops");
+
+TEST_CASE_FIXTURE(Fixture, "for_loop")
+{
+    CheckResult result = check(R"(
+        local q
+        for i=0, 50, 2 do
+            q = i
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.numberType, *requireType("q"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop")
+{
+    CheckResult result = check(R"(
+        local n
+        local s
+        for i, v in pairs({ "foo" }) do
+            n = i
+            s = v
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.numberType, *requireType("n"));
+    CHECK_EQ(*typeChecker.stringType, *requireType("s"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_with_next")
+{
+    CheckResult result = check(R"(
+        local n
+        local s
+        for i, v in next, { "foo", "bar" } do
+            n = i
+            s = v
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.numberType, *requireType("n"));
+    CHECK_EQ(*typeChecker.stringType, *requireType("s"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_with_an_iterator_of_type_any")
+{
+    CheckResult result = check(R"(
+        local it: any
+        local a, b
+        for i, v in it do
+            a, b = i, v
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_should_fail_with_non_function_iterator")
+{
+    CheckResult result = check(R"(
+        local foo = "bar"
+        for i, v in foo do
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_with_just_one_iterator_is_ok")
+{
+    CheckResult result = check(R"(
+        local function keys(dictionary)
+            local new = {}
+            local index = 1
+
+            for key in pairs(dictionary) do
+                new[index] = key
+                index = index + 1
+            end
+
+            return new
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_with_a_custom_iterator_should_type_check")
+{
+    CheckResult result = check(R"(
+        local function range(l, h): () -> number
+            return function()
+                return l
+            end
+        end
+
+        for n: string in range(1, 10) do
+            print(n)
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_on_error")
+{
+    CheckResult result = check(R"(
+        function f(x)
+            gobble.prop = x.otherprop
+        end
+
+        local p
+        for _, part in i_am_not_defined do
+            p = part
+            f(part)
+            part.thirdprop = false
+        end
+    )");
+
+    CHECK_EQ(2, result.errors.size());
+
+    TypeId p = requireType("p");
+    CHECK_EQ("*unknown*", toString(p));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_on_non_function")
+{
+    CheckResult result = check(R"(
+        local bad_iter = 5
+
+        for a in bad_iter() do
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    REQUIRE(get<CannotCallNonFunction>(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_error_on_factory_not_returning_the_right_amount_of_values")
+{
+    CheckResult result = check(R"(
+        local function hasDivisors(value: number, table)
+            return false
+        end
+
+        function prime_iter(state, index)
+            while hasDivisors(index, state) do
+                index += 1
+            end
+
+            state[index] = true
+            return index
+        end
+
+        function primes1()
+            return prime_iter, {}
+        end
+
+        function primes2()
+            return prime_iter, {}, ""
+        end
+
+        function primes3()
+            return prime_iter, {}, 2
+        end
+
+        for p in primes1() do print(p) end -- mismatch in argument count
+
+        for p in primes2() do print(p) end -- mismatch in argument types, prime_iter takes {}, number, we are given {}, string
+
+        for p in primes3() do print(p) end -- no error
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+
+    CountMismatch* acm = get<CountMismatch>(result.errors[0]);
+    REQUIRE(acm);
+    CHECK_EQ(acm->context, CountMismatch::Arg);
+    CHECK_EQ(2, acm->expected);
+    CHECK_EQ(1, acm->actual);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[1]);
+    REQUIRE(tm);
+    CHECK_EQ(typeChecker.numberType, tm->wantedType);
+    CHECK_EQ(typeChecker.stringType, tm->givenType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_error_on_iterator_requiring_args_but_none_given")
+{
+    CheckResult result = check(R"(
+        function prime_iter(state, index)
+            return 1
+        end
+
+        for p in prime_iter do print(p) end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CountMismatch* acm = get<CountMismatch>(result.errors[0]);
+    REQUIRE(acm);
+    CHECK_EQ(acm->context, CountMismatch::Arg);
+    CHECK_EQ(2, acm->expected);
+    CHECK_EQ(0, acm->actual);
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_with_custom_iterator")
+{
+    CheckResult result = check(R"(
+        function primes()
+            return function (state: number) end,  2
+        end
+
+        for p, q in primes do
+            q = ""
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    REQUIRE(tm);
+    CHECK_EQ(typeChecker.numberType, tm->wantedType);
+    CHECK_EQ(typeChecker.stringType, tm->givenType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "while_loop")
+{
+    CheckResult result = check(R"(
+        local i
+        while true do
+            i = 8
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.numberType, *requireType("i"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "repeat_loop")
+{
+    CheckResult result = check(R"(
+        local i
+        repeat
+            i = 'hi'
+        until true
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(*typeChecker.stringType, *requireType("i"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "repeat_loop_condition_binds_to_its_block")
+{
+    CheckResult result = check(R"(
+        repeat
+            local x = true
+        until x
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "symbols_in_repeat_block_should_not_be_visible_beyond_until_condition")
+{
+    CheckResult result = check(R"(
+        repeat
+            local x = true
+        until x
+
+        print(x)
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "varlist_declared_by_for_in_loop_should_be_free")
+{
+    CheckResult result = check(R"(
+        local T = {}
+
+        function T.f(p)
+            for i, v in pairs(p) do
+                T.f(v)
+            end
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "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.
+    CheckResult result = check(R"(
+        for iter in pairs({}) do
+            iter:g().p = true
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "correctly_scope_locals_while")
+{
+    CheckResult result = check(R"(
+        while true do
+            local a = 1
+        end
+
+        print(a) -- oops!
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    UnknownSymbol* us = get<UnknownSymbol>(result.errors[0]);
+    REQUIRE(us);
+    CHECK_EQ(us->name, "a");
+}
+
+TEST_CASE_FIXTURE(Fixture, "ipairs_produces_integral_indices")
+{
+    CheckResult result = check(R"(
+        local key
+        for i, e in ipairs({}) do key = i end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    REQUIRE_EQ("number", toString(requireType("key")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "for_in_loop_where_iteratee_is_free")
+{
+    // This code doesn't pass typechecking.  We just care that it doesn't crash.
+    (void)check(R"(
+        --!nonstrict
+        function _:_(...)
+        end
+
+        repeat
+            if _ then
+            else
+                _ = ...
+            end
+        until _
+
+        for _ in _() do
+        end
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "unreachable_code_after_infinite_loop")
+{
+    {
+        CheckResult result = check(R"(
+            function unreachablecodepath(a): number
+                while true do
+                    if a then return 10 end
+                end
+                -- unreachable
+            end
+            unreachablecodepath(4)
+        )");
+
+        LUAU_REQUIRE_ERROR_COUNT(0, result);
+    }
+
+    {
+        CheckResult result = check(R"(
+            function reachablecodepath(a): number
+                while true do
+                    if a then break end
+                    return 10
+                end
+
+                print("x") -- correct error
+            end
+            reachablecodepath(4)
+        )");
+
+        LUAU_REQUIRE_ERRORS(result);
+        CHECK(get<FunctionExitsWithoutReturning>(result.errors[0]));
+    }
+
+    {
+        CheckResult result = check(R"(
+            function unreachablecodepath(a): number
+                repeat
+                    if a then return 10 end
+                until false
+
+                -- unreachable
+            end
+            unreachablecodepath(4)
+        )");
+
+        LUAU_REQUIRE_ERROR_COUNT(0, result);
+    }
+
+    {
+        CheckResult result = check(R"(
+            function reachablecodepath(a, b): number
+                repeat
+                    if a then break end
+
+                    if b then return 10 end
+                until false
+
+                print("x") -- correct error
+            end
+            reachablecodepath(4)
+        )");
+
+        LUAU_REQUIRE_ERRORS(result);
+        CHECK(get<FunctionExitsWithoutReturning>(result.errors[0]));
+    }
+
+    {
+        CheckResult result = check(R"(
+            function unreachablecodepath(a: number?): number
+                repeat
+                    return 10
+                until a ~= nil
+
+                -- unreachable
+            end
+            unreachablecodepath(4)
+        )");
+
+        LUAU_REQUIRE_ERROR_COUNT(0, result);
+    }
+}
+
+TEST_CASE_FIXTURE(Fixture, "loop_typecheck_crash_on_empty_optional")
+{
+    CheckResult result = check(R"(
+        local t = {}
+        for _ in t do
+            for _ in assert(missing()) do
+            end
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.modules.test.cpp

@@ -0,0 +1,310 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferModules");
+
+TEST_CASE_FIXTURE(Fixture, "require")
+{
+    fileResolver.source["game/A"] = R"(
+        local function hooty(x: number): string
+            return "Hi there!"
+        end
+
+        return {hooty=hooty}
+    )";
+
+    fileResolver.source["game/B"] = R"(
+        local Hooty = require(game.A)
+
+        local h -- free!
+        local i = Hooty.hooty(h)
+    )";
+
+    CheckResult aResult = frontend.check("game/A");
+    dumpErrors(aResult);
+    LUAU_REQUIRE_NO_ERRORS(aResult);
+
+    CheckResult bResult = frontend.check("game/B");
+    dumpErrors(bResult);
+    LUAU_REQUIRE_NO_ERRORS(bResult);
+
+    ModulePtr b = frontend.moduleResolver.modules["game/B"];
+
+    REQUIRE(b != nullptr);
+
+    dumpErrors(bResult);
+
+    std::optional<TypeId> iType = requireType(b, "i");
+    REQUIRE_EQ("string", toString(*iType));
+
+    std::optional<TypeId> hType = requireType(b, "h");
+    REQUIRE_EQ("number", toString(*hType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "require_types")
+{
+    fileResolver.source["workspace/A"] = R"(
+        export type Point = {x: number, y: number}
+
+        return {}
+    )";
+
+    fileResolver.source["workspace/B"] = R"(
+        local Hooty = require(workspace.A)
+
+        local h: Hooty.Point
+    )";
+
+    CheckResult bResult = frontend.check("workspace/B");
+    dumpErrors(bResult);
+
+    ModulePtr b = frontend.moduleResolver.modules["workspace/B"];
+    REQUIRE(b != nullptr);
+
+    TypeId hType = requireType(b, "h");
+    REQUIRE_MESSAGE(bool(get<TableTypeVar>(hType)), "Expected table but got " << toString(hType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "require_a_variadic_function")
+{
+    fileResolver.source["game/A"] = R"(
+        local T = {}
+        function T.f(...) end
+        return T
+    )";
+
+    fileResolver.source["game/B"] = R"(
+        local A = require(game.A)
+        local f = A.f
+    )";
+
+    CheckResult result = frontend.check("game/B");
+
+    ModulePtr bModule = frontend.moduleResolver.getModule("game/B");
+    REQUIRE(bModule != nullptr);
+
+    TypeId f = follow(requireType(bModule, "f"));
+
+    const FunctionTypeVar* ftv = get<FunctionTypeVar>(f);
+    REQUIRE(ftv);
+
+    auto iter = begin(ftv->argTypes);
+    auto endIter = end(ftv->argTypes);
+
+    REQUIRE(iter == endIter);
+    REQUIRE(iter.tail());
+
+    CHECK(get<VariadicTypePack>(*iter.tail()));
+}
+
+TEST_CASE_FIXTURE(Fixture, "type_error_of_unknown_qualified_type")
+{
+    CheckResult result = check(R"(
+        local p: SomeModule.DoesNotExist
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    REQUIRE_EQ(result.errors[0], (TypeError{Location{{1, 17}, {1, 40}}, UnknownSymbol{"SomeModule.DoesNotExist"}}));
+}
+
+TEST_CASE_FIXTURE(Fixture, "require_module_that_does_not_export")
+{
+    const std::string sourceA = R"(
+    )";
+
+    const std::string sourceB = R"(
+        local Hooty = require(script.Parent.A)
+    )";
+
+    fileResolver.source["game/Workspace/A"] = sourceA;
+    fileResolver.source["game/Workspace/B"] = sourceB;
+
+    frontend.check("game/Workspace/A");
+    frontend.check("game/Workspace/B");
+
+    ModulePtr aModule = frontend.moduleResolver.modules["game/Workspace/A"];
+    ModulePtr bModule = frontend.moduleResolver.modules["game/Workspace/B"];
+
+    CHECK(aModule->errors.empty());
+    REQUIRE_EQ(1, bModule->errors.size());
+    CHECK_MESSAGE(get<IllegalRequire>(bModule->errors[0]), "Should be IllegalRequire: " << toString(bModule->errors[0]));
+
+    auto hootyType = requireType(bModule, "Hooty");
+
+    CHECK_EQ("*unknown*", toString(hootyType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "warn_if_you_try_to_require_a_non_modulescript")
+{
+    fileResolver.source["Modules/A"] = "";
+    fileResolver.sourceTypes["Modules/A"] = SourceCode::Local;
+
+    fileResolver.source["Modules/B"] = R"(
+        local M = require(script.Parent.A)
+    )";
+
+    CheckResult result = frontend.check("Modules/B");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK(get<IllegalRequire>(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "general_require_call_expression")
+{
+    fileResolver.source["game/A"] = R"(
+--!strict
+return { def = 4 }
+    )";
+
+    fileResolver.source["game/B"] = R"(
+--!strict
+local tbl = { abc = require(game.A) }
+local a : string = ""
+a = tbl.abc.def
+    )";
+
+    CheckResult result = frontend.check("game/B");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Type 'number' could not be converted into 'string'", toString(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "general_require_type_mismatch")
+{
+    fileResolver.source["game/A"] = R"(
+return { def = 4 }
+    )";
+
+    fileResolver.source["game/B"] = R"(
+local tbl: string = require(game.A)
+    )";
+
+    CheckResult result = frontend.check("game/B");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Type '{| def: number |}' could not be converted into 'string'", toString(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "bound_free_table_export_is_ok")
+{
+    CheckResult result = check(R"(
+local n = {}
+function n:Clone() end
+
+local m = {}
+
+function m.a(x)
+    x:Clone()
+end
+
+function m.b()
+    m.a(n)
+end
+
+return m
+)");
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "custom_require_global")
+{
+    CheckResult result = check(R"(
+--!nonstrict
+require = function(a) end
+
+local crash = require(game.A)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "require_failed_module")
+{
+    fileResolver.source["game/A"] = R"(
+return unfortunately()
+    )";
+
+    CheckResult aResult = frontend.check("game/A");
+    LUAU_REQUIRE_ERRORS(aResult);
+
+    CheckResult result = check(R"(
+local ModuleA = require(game.A)
+    )");
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    std::optional<TypeId> oty = requireType("ModuleA");
+    CHECK_EQ("*unknown*", toString(*oty));
+}
+
+TEST_CASE_FIXTURE(Fixture, "do_not_modify_imported_types")
+{
+    fileResolver.source["game/A"] = R"(
+export type Type = { unrelated: boolean }
+return {}
+    )";
+
+    fileResolver.source["game/B"] = R"(
+local types = require(game.A)
+type Type = types.Type
+local x: Type = {}
+function x:Destroy(): () end
+    )";
+
+    CheckResult result = frontend.check("game/B");
+    LUAU_REQUIRE_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "do_not_modify_imported_types_2")
+{
+    ScopedFastFlag immutableTypes{"LuauImmutableTypes", true};
+
+    fileResolver.source["game/A"] = R"(
+export type Type = { x: { a: number } }
+return {}
+    )";
+
+    fileResolver.source["game/B"] = R"(
+local types = require(game.A)
+type Type = types.Type
+local x: Type = { x = { a = 2 } }
+type Rename = typeof(x.x)
+    )";
+
+    CheckResult result = frontend.check("game/B");
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "do_not_modify_imported_types_3")
+{
+    ScopedFastFlag immutableTypes{"LuauImmutableTypes", true};
+
+    fileResolver.source["game/A"] = R"(
+local y = setmetatable({}, {})
+export type Type = { x: typeof(y) }
+return { x = y }
+    )";
+
+    fileResolver.source["game/B"] = R"(
+local types = require(game.A)
+type Type = types.Type
+local x: Type = types
+type Rename = typeof(x.x)
+    )";
+
+    CheckResult result = frontend.check("game/B");
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.oop.test.cpp

@@ -0,0 +1,275 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferOOP");
+
+TEST_CASE_FIXTURE(Fixture, "dont_suggest_using_colon_rather_than_dot_if_not_defined_with_colon")
+{
+    CheckResult result = check(R"(
+        local someTable = {}
+
+        someTable.Function1 = function(Arg1)
+        end
+
+        someTable.Function1() -- Argument count mismatch
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    REQUIRE(get<CountMismatch>(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "dont_suggest_using_colon_rather_than_dot_if_it_wont_help_2")
+{
+    CheckResult result = check(R"(
+        local someTable = {}
+
+        someTable.Function2 = function(Arg1, Arg2)
+        end
+
+        someTable.Function2() -- Argument count mismatch
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    REQUIRE(get<CountMismatch>(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "dont_suggest_using_colon_rather_than_dot_if_another_overload_works")
+{
+    CheckResult result = check(R"(
+        type T = {method: ((T, number) -> number) & ((number) -> number)}
+        local T: T
+
+        T.method(4)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "method_depends_on_table")
+{
+    CheckResult result = check(R"(
+        -- This catches a bug where x:m didn't count as a use of x
+        -- so toposort would happily reorder a definition of
+        -- function x:m before the definition of x.
+        function g() f() end
+        local x = {}
+        function x:m() end
+        function f() x:m() end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "methods_are_topologically_sorted")
+{
+    CheckResult result = check(R"(
+        local T = {}
+
+        function T:foo()
+            return T:bar(999), T:bar("hi")
+        end
+
+        function T:bar(i)
+            return i
+        end
+
+        local a, b = T:foo()
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    dumpErrors(result);
+
+    CHECK_EQ(PrimitiveTypeVar::Number, getPrimitiveType(requireType("a")));
+    CHECK_EQ(PrimitiveTypeVar::String, getPrimitiveType(requireType("b")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "quantify_methods_defined_using_dot_syntax_and_explicit_self_parameter")
+{
+    check(R"(
+        local T = {}
+
+        function T.method(self)
+            self:method()
+        end
+
+        function T.method2(self)
+            self:method()
+        end
+
+        T:method2()
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "inferring_hundreds_of_self_calls_should_not_suffocate_memory")
+{
+    CheckResult result = check(R"(
+        ("foo")
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+            :lower()
+    )");
+
+    ModulePtr module = getMainModule();
+    CHECK_GE(50, module->internalTypes.typeVars.size());
+}
+
+TEST_CASE_FIXTURE(Fixture, "object_constructor_can_refer_to_method_of_self")
+{
+    // CLI-30902
+    CheckResult result = check(R"(
+        --!strict
+
+        type Foo = {
+            fooConn: () -> () | nil
+        }
+
+        local Foo = {}
+        Foo.__index = Foo
+
+        function Foo.new()
+            local self: Foo = {
+                fooConn = nil,
+            }
+            setmetatable(self, Foo)
+
+            self.fooConn = function()
+                self:method() -- Key 'method' not found in table self
+            end
+
+            return self
+        end
+
+        function Foo:method()
+            print("foo")
+        end
+
+        local foo = Foo.new()
+
+        -- TODO This is the best our current refinement support can offer :(
+        local bar = foo.fooConn
+        if bar then bar() end
+
+        -- foo.fooConn()
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "CheckMethodsOfSealed")
+{
+    CheckResult result = check(R"(
+local x: {prop: number} = {prop=9999}
+function x:y(z: number)
+    local s: string = z
+end
+)");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "nonstrict_self_mismatch_tail")
+{
+    CheckResult result = check(R"(
+--!nonstrict
+local f = {}
+function f:foo(a: number, b: number) end
+
+function bar(...)
+    f.foo(f, 1, ...)
+end
+
+bar(2)
+)");
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "inferred_methods_of_free_tables_have_the_same_level_as_the_enclosing_table")
+{
+    check(R"(
+        function Base64FileReader(data)
+            local reader = {}
+            local index: number
+
+            function reader:PeekByte()
+                return data:byte(index)
+            end
+
+            function reader:Byte()
+                return data:byte(index - 1)
+            end
+
+            return reader
+        end
+
+        Base64FileReader()
+
+        function ReadMidiEvents(data)
+
+            local reader = Base64FileReader(data)
+
+            while reader:HasMore() do
+                (reader:Byte() % 128)
+            end
+        end
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_oop")
+{
+    CheckResult result = check(R"(
+   --!strict
+local Class = {}
+Class.__index = Class
+
+type Class = typeof(setmetatable({} :: { x: number }, Class))
+
+function Class.new(x: number): Class
+    return setmetatable({x = x}, Class)
+end
+
+function Class.getx(self: Class)
+    return self.x
+end
+
+function test()
+    local c = Class.new(42)
+    local n = c:getx()
+    local nn = c.x
+
+    print(string.format("%d %d", n, nn))
+end
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.operators.test.cpp

@@ -0,0 +1,759 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferOperators");
+
+TEST_CASE_FIXTURE(Fixture, "or_joins_types")
+{
+    CheckResult result = check(R"(
+        local s = "a" or 10
+        local x:string|number = s
+    )");
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ(toString(*requireType("s")), "number | string");
+    CHECK_EQ(toString(*requireType("x")), "number | string");
+}
+
+TEST_CASE_FIXTURE(Fixture, "or_joins_types_with_no_extras")
+{
+    CheckResult result = check(R"(
+        local s = "a" or 10
+        local x:number|string = s
+        local y = x or "s"
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(toString(*requireType("s")), "number | string");
+    CHECK_EQ(toString(*requireType("y")), "number | string");
+}
+
+TEST_CASE_FIXTURE(Fixture, "or_joins_types_with_no_superfluous_union")
+{
+    CheckResult result = check(R"(
+        local s = "a" or "b"
+        local x:string = s
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(*requireType("s"), *typeChecker.stringType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "and_adds_boolean")
+{
+    CheckResult result = check(R"(
+        local s = "a" and 10
+        local x:boolean|number = s
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(toString(*requireType("s")), "boolean | number");
+}
+
+TEST_CASE_FIXTURE(Fixture, "and_adds_boolean_no_superfluous_union")
+{
+    CheckResult result = check(R"(
+        local s = "a" and true
+        local x:boolean = s
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(*requireType("x"), *typeChecker.booleanType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "and_or_ternary")
+{
+    CheckResult result = check(R"(
+        local s = (1/2) > 0.5 and "a" or 10
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(toString(*requireType("s")), "number | string");
+}
+
+TEST_CASE_FIXTURE(Fixture, "primitive_arith_no_metatable")
+{
+    CheckResult result = check(R"(
+        function add(a: number, b: string)
+            return a + (tonumber(b) :: number), a .. b
+        end
+        local n, s = add(2,"3")
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    const FunctionTypeVar* functionType = get<FunctionTypeVar>(requireType("add"));
+
+    std::optional<TypeId> retType = first(functionType->retType);
+    CHECK_EQ(std::optional<TypeId>(typeChecker.numberType), retType);
+    CHECK_EQ(requireType("n"), typeChecker.numberType);
+    CHECK_EQ(requireType("s"), typeChecker.stringType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "primitive_arith_no_metatable_with_follows")
+{
+    CheckResult result = check(R"(
+        local PI=3.1415926535897931
+        local SOLAR_MASS=4*PI * PI
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ(requireType("SOLAR_MASS"), typeChecker.numberType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "primitive_arith_possible_metatable")
+{
+    CheckResult result = check(R"(
+        function add(a: number, b: any)
+            return a + b
+        end
+        local t = add(1,2)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ("any", toString(requireType("t")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "some_primitive_binary_ops")
+{
+    CheckResult result = check(R"(
+        local a = 4 + 8
+        local b = a + 9
+        local s = 'hotdogs'
+        local t = s .. s
+        local c = b - a
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("number", toString(requireType("a")));
+    CHECK_EQ("number", toString(requireType("b")));
+    CHECK_EQ("string", toString(requireType("s")));
+    CHECK_EQ("string", toString(requireType("t")));
+    CHECK_EQ("number", toString(requireType("c")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "typecheck_overloaded_multiply_that_is_an_intersection")
+{
+    ScopedFastFlag sff{"LuauErrorRecoveryType", true};
+
+    CheckResult result = check(R"(
+        --!strict
+        local Vec3 = {}
+        Vec3.__index = Vec3
+        function Vec3.new()
+            return setmetatable({x=0, y=0, z=0}, Vec3)
+        end
+
+        export type Vec3 = typeof(Vec3.new())
+
+        local thefun: any = function(self, o) return self end
+
+        local multiply: ((Vec3, Vec3) -> Vec3) & ((Vec3, number) -> Vec3) = thefun
+
+        Vec3.__mul = multiply
+
+        local a = Vec3.new()
+        local b = Vec3.new()
+        local c = a * b
+        local d = a * 2
+        local e = a * 'cabbage'
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("Vec3", toString(requireType("a")));
+    CHECK_EQ("Vec3", toString(requireType("b")));
+    CHECK_EQ("Vec3", toString(requireType("c")));
+    CHECK_EQ("Vec3", toString(requireType("d")));
+    CHECK_EQ("Vec3", toString(requireType("e")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "typecheck_overloaded_multiply_that_is_an_intersection_on_rhs")
+{
+    ScopedFastFlag sff{"LuauErrorRecoveryType", true};
+
+    CheckResult result = check(R"(
+        --!strict
+        local Vec3 = {}
+        Vec3.__index = Vec3
+        function Vec3.new()
+            return setmetatable({x=0, y=0, z=0}, Vec3)
+        end
+
+        export type Vec3 = typeof(Vec3.new())
+
+        local thefun: any = function(self, o) return self end
+
+        local multiply: ((Vec3, Vec3) -> Vec3) & ((Vec3, number) -> Vec3) = thefun
+
+        Vec3.__mul = multiply
+
+        local a = Vec3.new()
+        local b = Vec3.new()
+        local c = b * a
+        local d = 2 * a
+        local e = 'cabbage' * a
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("Vec3", toString(requireType("a")));
+    CHECK_EQ("Vec3", toString(requireType("b")));
+    CHECK_EQ("Vec3", toString(requireType("c")));
+    CHECK_EQ("Vec3", toString(requireType("d")));
+    CHECK_EQ("Vec3", toString(requireType("e")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "compare_numbers")
+{
+    CheckResult result = check(R"(
+        local a = 441
+        local b = 0
+        local c = a < b
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "compare_strings")
+{
+    CheckResult result = check(R"(
+        local a = '441'
+        local b = '0'
+        local c = a < b
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "cannot_indirectly_compare_types_that_do_not_have_a_metatable")
+{
+    CheckResult result = check(R"(
+        local a = {}
+        local b = {}
+        local c = a < b
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    GenericError* gen = get<GenericError>(result.errors[0]);
+
+    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")
+{
+    CheckResult result = check(R"(
+        local M = {}
+        function M.new()
+            return setmetatable({}, M)
+        end
+        type M = typeof(M.new())
+
+        local a = M.new()
+        local b = M.new()
+        local c = a < b
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    GenericError* gen = get<GenericError>(result.errors[0]);
+    REQUIRE(gen != nullptr);
+    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")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local M = {}
+        function M.new()
+            return setmetatable({}, M)
+        end
+        function M.__lt(left, right) return true end
+
+        local a = M.new()
+        local b = {}
+        local c = a < b -- line 10
+        local d = b < a -- line 11
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+
+    REQUIRE_EQ((Location{{10, 18}, {10, 23}}), result.errors[0].location);
+
+    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")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local M = {}
+        function M.new()
+            return setmetatable({}, M)
+        end
+        function M.__lt(left, right) return true end
+        type M = typeof(M.new())
+
+        local a = M.new()
+        local b = {}
+        local c = a < b -- line 10
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    auto err = get<GenericError>(result.errors[0]);
+    REQUIRE(err != nullptr);
+
+    // Frail. :|
+    REQUIRE_EQ("Types M and b cannot be compared with < because they do not have the same metatable", err->message);
+}
+
+TEST_CASE_FIXTURE(Fixture, "in_nonstrict_mode_strip_nil_from_intersections_when_considering_relational_operators")
+{
+    CheckResult result = check(R"(
+        --!nonstrict
+
+        function maybe_a_number(): number?
+            return 50
+        end
+
+        local a = maybe_a_number() < maybe_a_number()
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "compound_assign_basic")
+{
+    CheckResult result = check(R"(
+        local s = 10
+        s += 20
+    )");
+    CHECK_EQ(0, result.errors.size());
+    CHECK_EQ(toString(*requireType("s")), "number");
+}
+
+TEST_CASE_FIXTURE(Fixture, "compound_assign_mismatch_op")
+{
+    CheckResult result = check(R"(
+        local s = 10
+        s += true
+    )");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(result.errors[0], (TypeError{Location{{2, 13}, {2, 17}}, TypeMismatch{typeChecker.numberType, typeChecker.booleanType}}));
+}
+
+TEST_CASE_FIXTURE(Fixture, "compound_assign_mismatch_result")
+{
+    CheckResult result = check(R"(
+        local s = 'hello'
+        s += 10
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+    CHECK_EQ(result.errors[0], (TypeError{Location{{2, 8}, {2, 9}}, TypeMismatch{typeChecker.numberType, typeChecker.stringType}}));
+    CHECK_EQ(result.errors[1], (TypeError{Location{{2, 8}, {2, 15}}, TypeMismatch{typeChecker.stringType, typeChecker.numberType}}));
+}
+
+TEST_CASE_FIXTURE(Fixture, "compound_assign_metatable")
+{
+    CheckResult result = check(R"(
+        --!strict
+        type V2B = { x: number, y: number }
+        local v2b: V2B = { x = 0, y = 0 }
+        local VMT = {}
+        type V2 = typeof(setmetatable(v2b, VMT))
+
+        function VMT.__add(a: V2, b: V2): V2
+            return setmetatable({ x = a.x + b.x, y = a.y + b.y }, VMT)
+        end
+
+        local v1: V2 = setmetatable({ x = 1, y = 2 }, VMT)
+        local v2: V2 = setmetatable({ x = 3, y = 4 }, VMT)
+        v1 += v2
+    )");
+    CHECK_EQ(0, result.errors.size());
+}
+
+TEST_CASE_FIXTURE(Fixture, "compound_assign_mismatch_metatable")
+{
+    CheckResult result = check(R"(
+        --!strict
+        type V2B = { x: number, y: number }
+        local v2b: V2B = { x = 0, y = 0 }
+        local VMT = {}
+        type V2 = typeof(setmetatable(v2b, VMT))
+
+        function VMT.__mod(a: V2, b: V2): number
+            return a.x * b.x + a.y * b.y
+        end
+
+        local v1: V2 = setmetatable({ x = 1, y = 2 }, VMT)
+        local v2: V2 = setmetatable({ x = 3, y = 4 }, VMT)
+        v1 %= v2
+    )");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    CHECK_EQ(*tm->wantedType, *requireType("v2"));
+    CHECK_EQ(*tm->givenType, *typeChecker.numberType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "CallOrOfFunctions")
+{
+    CheckResult result = check(R"(
+function f() return 1; end
+function g() return 2; end
+(f or g)()
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "CallAndOrOfFunctions")
+{
+    CheckResult result = check(R"(
+function f() return 1; end
+function g() return 2; end
+local x = false
+(x and f or g)()
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "typecheck_unary_minus")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local foo = {
+            value = 10
+        }
+        local mt = {}
+        setmetatable(foo, mt)
+
+        mt.__unm = function(val: typeof(foo)): string
+            return val.value .. "test"
+        end
+
+        local a = -foo
+
+        local b = 1+-1
+
+        local bar = {
+            value = 10
+        }
+        local c = -bar -- disallowed
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ("string", toString(requireType("a")));
+    CHECK_EQ("number", toString(requireType("b")));
+
+    GenericError* gen = get<GenericError>(result.errors[0]);
+    REQUIRE_EQ(gen->message, "Unary operator '-' not supported by type 'bar'");
+}
+
+TEST_CASE_FIXTURE(Fixture, "unary_not_is_boolean")
+{
+    CheckResult result = check(R"(
+        local b = not "string"
+        local c = not (math.random() > 0.5 and "string" or 7)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    REQUIRE_EQ("boolean", toString(requireType("b")));
+    REQUIRE_EQ("boolean", toString(requireType("c")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "disallow_string_and_types_without_metatables_from_arithmetic_binary_ops")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local a = "1.24" + 123 -- not allowed
+
+        local foo = {
+            value = 10
+        }
+
+        local b = foo + 1 -- not allowed
+
+        local bar = {
+            value = 1
+        }
+
+        local mt = {}
+
+        setmetatable(bar, mt)
+
+        mt.__add = function(a: typeof(bar), b: number): number
+            return a.value + b
+        end
+
+        local c = bar + 1 -- allowed
+
+        local d = bar + foo -- not allowed
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(3, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    REQUIRE_EQ(*tm->wantedType, *typeChecker.numberType);
+    REQUIRE_EQ(*tm->givenType, *typeChecker.stringType);
+
+    TypeMismatch* tm2 = get<TypeMismatch>(result.errors[2]);
+    CHECK_EQ(*tm2->wantedType, *typeChecker.numberType);
+    CHECK_EQ(*tm2->givenType, *requireType("foo"));
+
+    GenericError* gen2 = get<GenericError>(result.errors[1]);
+    REQUIRE_EQ(gen2->message, "Binary operator '+' not supported by types 'foo' and 'number'");
+}
+
+// CLI-29033
+TEST_CASE_FIXTURE(Fixture, "unknown_type_in_comparison")
+{
+    CheckResult result = check(R"(
+        function merge(lower, greater)
+            if lower.y == greater.y then
+            end
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "concat_op_on_free_lhs_and_string_rhs")
+{
+    CheckResult result = check(R"(
+        local function f(x)
+            return x .. "y"
+        end
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    REQUIRE(get<CannotInferBinaryOperation>(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "concat_op_on_string_lhs_and_free_rhs")
+{
+    CheckResult result = check(R"(
+        local function f(x)
+            return "foo" .. x
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("(string) -> string", toString(requireType("f")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "strict_binary_op_where_lhs_unknown")
+{
+    std::vector<std::string> ops = {"+", "-", "*", "/", "%", "^", ".."};
+
+    std::string src = R"(
+        function foo(a, b)
+    )";
+
+    for (const auto& op : ops)
+        src += "local _ = a " + op + "b\n";
+
+    src += "end";
+
+    CheckResult result = check(src);
+    LUAU_REQUIRE_ERROR_COUNT(ops.size(), result);
+
+    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")
+{
+    CheckResult result = check(R"(
+    --!strict
+    local t = {}
+    while true and t[1] do
+        print(t[1].test)
+    end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "error_on_invalid_operand_types_to_relational_operators")
+{
+    CheckResult result = check(R"(
+        local a: boolean = true
+        local b: boolean = false
+        local foo = a < b
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    GenericError* ge = get<GenericError>(result.errors[0]);
+    REQUIRE(ge);
+    CHECK_EQ("Type 'boolean' cannot be compared with relational operator <", ge->message);
+}
+
+TEST_CASE_FIXTURE(Fixture, "error_on_invalid_operand_types_to_relational_operators2")
+{
+    CheckResult result = check(R"(
+        local a: number | string = ""
+        local b: number | string = 1
+        local foo = a < b
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    GenericError* ge = get<GenericError>(result.errors[0]);
+    REQUIRE(ge);
+    CHECK_EQ("Type 'number | string' cannot be compared with relational operator <", ge->message);
+}
+
+TEST_CASE_FIXTURE(Fixture, "cli_38355_recursive_union")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local _
+        _ += _ and _ or _ and _ or _ and _
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Type contains a self-recursive construct that cannot be resolved", toString(result.errors[0]));
+}
+
+TEST_CASE_FIXTURE(Fixture, "UnknownGlobalCompoundAssign")
+{
+    // In non-strict mode, global definition is still allowed
+    {
+        CheckResult result = check(R"(
+            --!nonstrict
+            a = a + 1
+            print(a)
+        )");
+
+        LUAU_REQUIRE_ERROR_COUNT(1, result);
+        CHECK_EQ(toString(result.errors[0]), "Unknown global 'a'");
+    }
+
+    // In strict mode we no longer generate two errors from lhs
+    {
+        CheckResult result = check(R"(
+            --!strict
+            a += 1
+            print(a)
+        )");
+
+        LUAU_REQUIRE_ERRORS(result);
+        CHECK_EQ(toString(result.errors[0]), "Unknown global 'a'");
+    }
+
+    // In non-strict mode, compound assignment is not a definition, it's a modification
+    {
+        CheckResult result = check(R"(
+            --!nonstrict
+            a += 1
+            print(a)
+        )");
+
+        LUAU_REQUIRE_ERROR_COUNT(2, result);
+        CHECK_EQ(toString(result.errors[0]), "Unknown global 'a'");
+    }
+}
+
+TEST_CASE_FIXTURE(Fixture, "strip_nil_from_lhs_or_operator")
+{
+    CheckResult result = check(R"(
+--!strict
+local a: number? = nil
+local b: number = a or 1
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "strip_nil_from_lhs_or_operator2")
+{
+    CheckResult result = check(R"(
+--!nonstrict
+local a: number? = nil
+local b: number = a or 1
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "dont_strip_nil_from_rhs_or_operator")
+{
+    CheckResult result = check(R"(
+--!strict
+local a: number? = nil
+local b: number = 1 or a
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
+    REQUIRE(tm);
+    CHECK_EQ(typeChecker.numberType, tm->wantedType);
+    CHECK_EQ("number?", toString(tm->givenType));
+}
+
+TEST_CASE_FIXTURE(Fixture, "operator_eq_verifies_types_do_intersect")
+{
+    CheckResult result = check(R"(
+        type Array<T> = { [number]: T }
+        type Fiber = { id: number }
+        type null = {}
+
+        local fiberStack: Array<Fiber | null> = {}
+        local index = 0
+
+        local function f(fiber: Fiber)
+            local a = fiber ~= fiberStack[index]
+            local b = fiberStack[index] ~= fiber
+        end
+
+        return f
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "operator_eq_operands_are_not_subtypes_of_each_other_but_has_overlap")
+{
+    ScopedFastFlag sff1{"LuauEqConstraint", true};
+
+    CheckResult result = check(R"(
+        local function f(a: string | number, b: boolean | number)
+            return a == b
+        end
+    )");
+
+    // This doesn't produce any errors but for the wrong reasons.
+    // This unit test serves as a reminder to not try and unify the operands on `==`/`~=`.
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "refine_and_or")
+{
+    CheckResult result = check(R"(
+        local t: {x: number?}? = {x = nil}
+        local u = t and t.x or 5
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("number", toString(requireType("u")));
+}
+
+TEST_SUITE_END();

tests/TypeInfer.primitives.test.cpp

@@ -0,0 +1,100 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#include "Luau/AstQuery.h"
+#include "Luau/BuiltinDefinitions.h"
+#include "Luau/Scope.h"
+#include "Luau/TypeInfer.h"
+#include "Luau/TypeVar.h"
+#include "Luau/VisitTypeVar.h"
+
+#include "Fixture.h"
+
+#include "doctest.h"
+
+using namespace Luau;
+
+TEST_SUITE_BEGIN("TypeInferPrimitives");
+
+TEST_CASE_FIXTURE(Fixture, "cannot_call_primitives")
+{
+    CheckResult result = check("local foo = 5    foo()");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    REQUIRE(get<CannotCallNonFunction>(result.errors[0]) != nullptr);
+}
+
+TEST_CASE_FIXTURE(Fixture, "string_length")
+{
+    CheckResult result = check(R"(
+        local s = "Hello, World!"
+        local t = #s
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    CHECK_EQ("number", toString(requireType("t")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "string_index")
+{
+    CheckResult result = check(R"(
+        local s = "Hello, World!"
+        local t = s[4]
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    NotATable* nat = get<NotATable>(result.errors[0]);
+    REQUIRE(nat);
+    CHECK_EQ("string", toString(nat->ty));
+
+    CHECK_EQ("*unknown*", toString(requireType("t")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "string_method")
+{
+    CheckResult result = check(R"(
+        local p = ("tacos"):len()
+    )");
+    CHECK_EQ(0, result.errors.size());
+
+    CHECK_EQ(*requireType("p"), *typeChecker.numberType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "string_function_indirect")
+{
+    CheckResult result = check(R"(
+        local s:string
+        local l = s.lower
+        local p = l(s)
+    )");
+    CHECK_EQ(0, result.errors.size());
+
+    CHECK_EQ(*requireType("p"), *typeChecker.stringType);
+}
+
+TEST_CASE_FIXTURE(Fixture, "string_function_other")
+{
+    CheckResult result = check(R"(
+        local s:string
+        local p = s:match("foo")
+    )");
+    CHECK_EQ(0, result.errors.size());
+
+    CHECK_EQ(toString(requireType("p")), "string?");
+}
+
+TEST_CASE_FIXTURE(Fixture, "CheckMethodsOfNumber")
+{
+    ScopedFastFlag sff{"LuauErrorRecoveryType", true};
+
+    CheckResult result = check(R"(
+local x: number = 9999
+function x:y(z: number)
+    local s: string = z
+end
+)");
+
+    LUAU_REQUIRE_ERROR_COUNT(2, result);
+}
+
+TEST_SUITE_END();

tests/TypeInfer.refinements.test.cpp

@@ -1298,4 +1298,22 @@ TEST_CASE_FIXTURE(RefinementClassFixture, "x_is_not_instance_or_else_not_part")
     CHECK_EQ("Part", toString(requireTypeAtPosition({5, 28})));
 }
 
+TEST_CASE_FIXTURE(Fixture, "typeguard_doesnt_leak_to_elseif")
+{
+    const std::string code = R"(
+        function f(a)
+           if type(a) == "boolean" then
+                local a1 = a
+            elseif a.fn() then
+                local a2 = a
+            else
+                local a3 = a
+            end
+        end
+    )";
+    CheckResult result = check(code);
+    LUAU_REQUIRE_NO_ERRORS(result);
+    dumpErrors(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.singletons.test.cpp

@@ -5,6 +5,8 @@
 #include "doctest.h"
 #include "Luau/BuiltinDefinitions.h"
 
+LUAU_FASTFLAG(BetterDiagnosticCodesInStudio)
+
 using namespace Luau;
 
 TEST_SUITE_BEGIN("TypeSingletons");
@@ -353,7 +355,14 @@ TEST_CASE_FIXTURE(Fixture, "table_properties_alias_or_parens_is_indexer")
     )");
 
     LUAU_REQUIRE_ERROR_COUNT(1, result);
-    CHECK_EQ("Syntax error: Cannot have more than one table indexer", toString(result.errors[0]));
+    if (FFlag::BetterDiagnosticCodesInStudio)
+    {
+        CHECK_EQ("Cannot have more than one table indexer", toString(result.errors[0]));
+    }
+    else
+    {
+        CHECK_EQ("Syntax error: Cannot have more than one table indexer", toString(result.errors[0]));
+    }
 }
 
 TEST_CASE_FIXTURE(Fixture, "table_properties_type_error_escapes")
@@ -445,7 +454,7 @@ TEST_CASE_FIXTURE(Fixture, "widen_the_supertype_if_it_is_free_and_subtype_has_si
         {"LuauSingletonTypes", true},
         {"LuauEqConstraint", true},
         {"LuauDiscriminableUnions2", true},
-        {"LuauWidenIfSupertypeIsFree", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
         {"LuauWeakEqConstraint", false},
     };
 
@@ -472,9 +481,9 @@ TEST_CASE_FIXTURE(Fixture, "return_type_of_f_is_not_widened")
         {"LuauSingletonTypes", true},
         {"LuauDiscriminableUnions2", true},
         {"LuauEqConstraint", true},
-        {"LuauWidenIfSupertypeIsFree", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
         {"LuauWeakEqConstraint", false},
-        {"LuauDoNotAccidentallyDependOnPointerOrdering", true}
+        {"LuauDoNotAccidentallyDependOnPointerOrdering", true},
     };
 
     CheckResult result = check(R"(
@@ -497,7 +506,7 @@ TEST_CASE_FIXTURE(Fixture, "widening_happens_almost_everywhere")
     ScopedFastFlag sff[]{
         {"LuauParseSingletonTypes", true},
         {"LuauSingletonTypes", true},
-        {"LuauWidenIfSupertypeIsFree", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
     };
 
     CheckResult result = check(R"(
@@ -515,7 +524,7 @@ TEST_CASE_FIXTURE(Fixture, "widening_happens_almost_everywhere_except_for_tables
         {"LuauParseSingletonTypes", true},
         {"LuauSingletonTypes", true},
         {"LuauDiscriminableUnions2", true},
-        {"LuauWidenIfSupertypeIsFree", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
     };
 
     CheckResult result = check(R"(
@@ -544,7 +553,7 @@ TEST_CASE_FIXTURE(Fixture, "table_insert_with_a_singleton_argument")
     ScopedFastFlag sff[]{
         {"LuauParseSingletonTypes", true},
         {"LuauSingletonTypes", true},
-        {"LuauWidenIfSupertypeIsFree", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
     };
 
     CheckResult result = check(R"(
@@ -565,4 +574,97 @@ TEST_CASE_FIXTURE(Fixture, "table_insert_with_a_singleton_argument")
     CHECK_EQ("{string}", toString(requireType("t")));
 }
 
+TEST_CASE_FIXTURE(Fixture, "functions_are_not_to_be_widened")
+{
+    ScopedFastFlag sff[]{
+        {"LuauParseSingletonTypes", true},
+        {"LuauSingletonTypes", true},
+        {"LuauWidenIfSupertypeIsFree2", true},
+    };
+
+    CheckResult result = check(R"(
+        local function foo(my_enum: "A" | "B") end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(R"(("A" | "B") -> ())", toString(requireType("foo")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "indexing_on_string_singletons")
+{
+    ScopedFastFlag sff[]{
+        {"LuauDiscriminableUnions2", true},
+        {"LuauSingletonTypes", true},
+    };
+
+    CheckResult result = check(R"(
+        local a: string = "hi"
+        if a == "hi" then
+            local x = a:byte()
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 22})));
+}
+
+TEST_CASE_FIXTURE(Fixture, "indexing_on_union_of_string_singletons")
+{
+    ScopedFastFlag sff[]{
+        {"LuauDiscriminableUnions2", true},
+        {"LuauSingletonTypes", true},
+    };
+
+    CheckResult result = check(R"(
+        local a: string = "hi"
+        if a == "hi" or a == "bye" then
+            local x = a:byte()
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(R"("bye" | "hi")", toString(requireTypeAtPosition({3, 22})));
+}
+
+TEST_CASE_FIXTURE(Fixture, "taking_the_length_of_string_singleton")
+{
+    ScopedFastFlag sff[]{
+        {"LuauDiscriminableUnions2", true},
+        {"LuauSingletonTypes", true},
+    };
+
+    CheckResult result = check(R"(
+        local a: string = "hi"
+        if a == "hi" then
+            local x = #a
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 23})));
+}
+
+TEST_CASE_FIXTURE(Fixture, "taking_the_length_of_union_of_string_singleton")
+{
+    ScopedFastFlag sff[]{
+        {"LuauDiscriminableUnions2", true},
+        {"LuauSingletonTypes", true},
+    };
+
+    CheckResult result = check(R"(
+        local a: string = "hi"
+        if a == "hi" or a == "bye" then
+            local x = #a
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ(R"("bye" | "hi")", toString(requireTypeAtPosition({3, 23})));
+}
+
 TEST_SUITE_END();

tests/TypeInfer.tables.test.cpp

@@ -2384,4 +2384,504 @@ _ = (_.cos)
     LUAU_REQUIRE_ERRORS(result);
 }
 
+TEST_CASE_FIXTURE(Fixture, "cannot_call_tables")
+{
+    CheckResult result = check("local foo = {}    foo()");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK(get<CannotCallNonFunction>(result.errors[0]) != nullptr);
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_length")
+{
+    CheckResult result = check(R"(
+        local t = {}
+        local s = #t
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK(nullptr != get<TableTypeVar>(requireType("t")));
+    CHECK_EQ(*typeChecker.numberType, *requireType("s"));
+}
+
+TEST_CASE_FIXTURE(Fixture, "nil_assign_doesnt_hit_indexer")
+{
+    CheckResult result = check("local a = {} a[0] = 7  a[0] = nil");
+    LUAU_REQUIRE_ERROR_COUNT(0, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "wrong_assign_does_hit_indexer")
+{
+    CheckResult result = check("local a = {} a[0] = 7  a[0] = 't'");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(result.errors[0], (TypeError{Location{Position{0, 30}, Position{0, 33}}, TypeMismatch{
+                                                                                          typeChecker.numberType,
+                                                                                          typeChecker.stringType,
+                                                                                      }}));
+}
+
+TEST_CASE_FIXTURE(Fixture, "nil_assign_doesnt_hit_no_indexer")
+{
+    CheckResult result = check("local a = {a=1, b=2} a['a'] = nil");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ(result.errors[0], (TypeError{Location{Position{0, 30}, Position{0, 33}}, TypeMismatch{
+                                                                                          typeChecker.numberType,
+                                                                                          typeChecker.nilType,
+                                                                                      }}));
+}
+
+TEST_CASE_FIXTURE(Fixture, "free_rhs_table_can_also_be_bound")
+{
+    check(R"(
+        local o
+        local v = o:i()
+
+        function g(u)
+            v = u
+        end
+
+        o:f(g)
+        o:h()
+        o:h()
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_unifies_into_map")
+{
+    CheckResult result = check(R"(
+        local Instance: any
+        local UDim2: any
+
+        function Create(instanceType)
+            return function(data)
+                local obj = Instance.new(instanceType)
+                for k, v in pairs(data) do
+                    if type(k) == 'number' then
+                        --v.Parent = obj
+                    else
+                        obj[k] = v
+                    end
+                end
+                return obj
+            end
+        end
+
+        local topbarShadow = Create'ImageLabel'{
+            Name = "TopBarShadow";
+            Size = UDim2.new(1, 0, 0, 3);
+            Position = UDim2.new(0, 0, 1, 0);
+            Image = "rbxasset://textures/ui/TopBar/dropshadow.png";
+            BackgroundTransparency = 1;
+            Active = false;
+            Visible = false;
+        };
+
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "tables_get_names_from_their_locals")
+{
+    CheckResult result = check(R"(
+        local T = {}
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    CHECK_EQ("T", toString(requireType("T")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "generalize_table_argument")
+{
+    CheckResult result = check(R"(
+        function foo(arr)
+            local work = {}
+            for i = 1, #arr do
+                work[i] = arr[i]
+            end
+
+            return arr
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+    dumpErrors(result);
+
+    const FunctionTypeVar* fooType = get<FunctionTypeVar>(requireType("foo"));
+    REQUIRE(fooType);
+
+    std::optional<TypeId> fooArg1 = first(fooType->argTypes);
+    REQUIRE(fooArg1);
+
+    const TableTypeVar* fooArg1Table = get<TableTypeVar>(*fooArg1);
+    REQUIRE(fooArg1Table);
+
+    CHECK_EQ(fooArg1Table->state, TableState::Generic);
+}
+
+/*
+ * This test case exposed an oversight in the treatment of free tables.
+ * Free tables, like free TypeVars, need to record the scope depth where they were created so that
+ * we do not erroneously let-generalize them when they are used in a nested lambda.
+ *
+ * For more information about let-generalization, see <http://okmij.org/ftp/ML/generalization.html>
+ *
+ * The important idea here is that the return type of Counter.new is a table with some metatable.
+ * That metatable *must* be the same TypeVar as the type of Counter.  If it is a copy (produced by
+ * 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")
+{
+    CheckResult result = check(R"(
+        local Counter = {}
+        Counter.__index = Counter
+
+        function Counter.new()
+            local self = setmetatable({count=0}, Counter)
+            return self
+        end
+
+        function Counter:incr()
+            self.count = 1
+            return self.count
+        end
+
+        local self = Counter.new()
+        print(self:incr())
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    TableTypeVar* counterType = getMutable<TableTypeVar>(requireType("Counter"));
+    REQUIRE(counterType);
+
+    const FunctionTypeVar* newType = get<FunctionTypeVar>(follow(counterType->props["new"].type));
+    REQUIRE(newType);
+
+    std::optional<TypeId> newRetType = *first(newType->retType);
+    REQUIRE(newRetType);
+
+    const MetatableTypeVar* newRet = get<MetatableTypeVar>(follow(*newRetType));
+    REQUIRE(newRet);
+
+    const TableTypeVar* newRetMeta = get<TableTypeVar>(newRet->metatable);
+    REQUIRE(newRetMeta);
+
+    CHECK(newRetMeta->props.count("incr"));
+    CHECK_EQ(follow(newRet->metatable), follow(requireType("Counter")));
+}
+
+// TODO: CLI-39624
+TEST_CASE_FIXTURE(Fixture, "instantiate_tables_at_scope_level")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local Option = {}
+        Option.__index = Option
+        function Option.Is(obj)
+                return (type(obj) == "table" and getmetatable(obj) == Option)
+        end
+        return Option
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "inferring_crazy_table_should_also_be_quick")
+{
+    CheckResult result = check(R"(
+        --!strict
+        function f(U)
+            U(w:s(an):c()():c():U(s):c():c():U(s):c():U(s):cU()):c():U(s):c():U(s):c():c():U(s):c():U(s):cU()
+        end
+    )");
+
+    ModulePtr module = getMainModule();
+    CHECK_GE(100, module->internalTypes.typeVars.size());
+}
+
+TEST_CASE_FIXTURE(Fixture, "MixedPropertiesAndIndexers")
+{
+    CheckResult result = check(R"(
+local x = {}
+x.a = "a"
+x[0] = true
+x.b = 37
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "setmetatable_cant_be_used_to_mutate_global_types")
+{
+    {
+        Fixture fix;
+
+        // inherit env from parent fixture checker
+        fix.typeChecker.globalScope = typeChecker.globalScope;
+
+        fix.check(R"(
+--!nonstrict
+type MT = typeof(setmetatable)
+function wtf(arg: {MT}): typeof(table)
+    arg = wtf(arg)
+end
+)");
+    }
+
+    // validate sharedEnv post-typecheck; valuable for debugging some typeck crashes but slows fuzzing down
+    // note: it's important for typeck to be destroyed at this point!
+    {
+        for (auto& p : typeChecker.globalScope->bindings)
+        {
+            toString(p.second.typeId); // toString walks the entire type, making sure ASAN catches access to destroyed type arenas
+        }
+    }
+}
+
+TEST_CASE_FIXTURE(Fixture, "evil_table_unification")
+{
+    // this code re-infers the type of _ while processing fields of _, which can cause use-after-free
+    check(R"(
+--!nonstrict
+_ = ...
+_:table(_,string)[_:gsub(_,...,n0)],_,_:gsub(_,string)[""],_:split(_,...,table)._,n0 = nil
+do end
+)");
+}
+
+TEST_CASE_FIXTURE(Fixture, "dont_crash_when_setmetatable_does_not_produce_a_metatabletypevar")
+{
+    CheckResult result = check("local x = setmetatable({})");
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+}
+
+TEST_CASE_FIXTURE(Fixture, "instantiate_table_cloning")
+{
+    CheckResult result = check(R"(
+--!nonstrict
+local l0:any,l61:t0<t32> = _,math
+while _ do
+_()
+end
+function _():t0<t0>
+end
+type t0<t32> = any
+)");
+
+    std::optional<TypeId> ty = requireType("math");
+    REQUIRE(ty);
+
+    const TableTypeVar* ttv = get<TableTypeVar>(*ty);
+    REQUIRE(ttv);
+    CHECK(ttv->instantiatedTypeParams.empty());
+}
+
+TEST_CASE_FIXTURE(Fixture, "instantiate_table_cloning_2")
+{
+    ScopedFastFlag sff{"LuauOnlyMutateInstantiatedTables", true};
+
+    CheckResult result = check(R"(
+type X<T> = T
+type K = X<typeof(math)>
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    std::optional<TypeId> ty = requireType("math");
+    REQUIRE(ty);
+
+    const TableTypeVar* ttv = get<TableTypeVar>(*ty);
+    REQUIRE(ttv);
+    CHECK(ttv->instantiatedTypeParams.empty());
+}
+
+TEST_CASE_FIXTURE(Fixture, "instantiate_table_cloning_3")
+{
+    ScopedFastFlag sff{"LuauOnlyMutateInstantiatedTables", true};
+
+    CheckResult result = check(R"(
+type X<T> = T
+local a = {}
+a.x = 4
+local b: X<typeof(a)>
+a.y = 5
+local c: X<typeof(a)>
+c = b
+)");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    std::optional<TypeId> ty = requireType("a");
+    REQUIRE(ty);
+
+    const TableTypeVar* ttv = get<TableTypeVar>(*ty);
+    REQUIRE(ttv);
+    CHECK(ttv->instantiatedTypeParams.empty());
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_indexing_error_location")
+{
+    CheckResult result = check(R"(
+local foo = {42}
+local bar: number?
+local baz = foo[bar]
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+
+    CHECK_EQ(result.errors[0].location, Location{Position{3, 16}, Position{3, 19}});
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_simple_call")
+{
+    CheckResult result = check(R"(
+local a = setmetatable({ x = 2 }, {
+    __call = function(self)
+        return (self.x :: number) * 2 -- should work without annotation in the future
+    end
+})
+local b = a()
+local c = a(2) -- too many arguments
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    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")
+{
+    CheckResult result = check(R"(
+        type Foo = {x: string}
+        local t = {}
+        setmetatable(t, {
+            __index = function(x: string): ...Foo
+                return {x = x}
+            end
+        })
+
+        local foo = t.bar
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    ToStringOptions o;
+    o.exhaustive = true;
+    CHECK_EQ("{| x: string |}", toString(requireType("foo"), o));
+}
+
+TEST_CASE_FIXTURE(Fixture, "dont_invalidate_the_properties_iterator_of_free_table_when_rolled_back")
+{
+    fileResolver.source["Module/Backend/Types"] = R"(
+        export type Fiber = {
+            return_: Fiber?
+        }
+        return {}
+    )";
+
+    fileResolver.source["Module/Backend"] = R"(
+        local Types = require(script.Types)
+        type Fiber = Types.Fiber
+        type ReactRenderer = { findFiberByHostInstance: () -> Fiber? }
+
+        local function attach(renderer): ()
+            local function getPrimaryFiber(fiber)
+                local alternate = fiber.alternate
+                return fiber
+            end
+
+            local function getFiberIDForNative()
+                local fiber = renderer.findFiberByHostInstance()
+                fiber = fiber.return_
+                return getPrimaryFiber(fiber)
+            end
+        end
+
+        function culprit(renderer: ReactRenderer): ()
+            attach(renderer)
+        end
+
+        return culprit
+    )";
+
+    CheckResult result = frontend.check("Module/Backend");
+}
+
+TEST_CASE_FIXTURE(Fixture, "checked_prop_too_early")
+{
+    CheckResult result = check(R"(
+        local t: {x: number?}? = {x = nil}
+        local u = t.x and t or 5
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Value of type '{| x: number? |}?' could be nil", toString(result.errors[0]));
+    CHECK_EQ("number | {| x: number? |}", toString(requireType("u")));
+}
+
+TEST_CASE_FIXTURE(Fixture, "accidentally_checked_prop_in_opposite_branch")
+{
+    CheckResult result = check(R"(
+        local t: {x: number?}? = {x = nil}
+        local u = t and t.x == 5 or t.x == 31337
+    )");
+
+    LUAU_REQUIRE_ERROR_COUNT(1, result);
+    CHECK_EQ("Value of type '{| x: number? |}?' could be nil", toString(result.errors[0]));
+    CHECK_EQ("boolean", toString(requireType("u")));
+}
+
+/*
+ * We had an issue where part of the type of pairs() was an unsealed table.
+ * This test depends on FFlagDebugLuauFreezeArena to trigger it.
+ */
+TEST_CASE_FIXTURE(Fixture, "pairs_parameters_are_not_unsealed_tables")
+{
+    check(R"(
+        function _(l0:{n0:any})
+            _ = pairs
+        end
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "table_function_check_use_after_free")
+{
+    CheckResult result = check(R"(
+local t = {}
+
+function t.x(value)
+    for k,v in pairs(t) do end
+end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
+/*
+ * When we add new properties to an unsealed table, we should do a level check and promote the property type to be at
+ * the level of the table.
+ */
+TEST_CASE_FIXTURE(Fixture, "inferred_properties_of_a_table_should_start_with_the_same_TypeLevel_of_that_table")
+{
+    CheckResult result = check(R"(
+        --!strict
+        local T = {}
+
+        local function f(prop)
+            T[1] = {
+                prop = prop,
+            }
+        end
+
+        local function g()
+            local l = T[1].prop
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/TypeInfer.typePacks.cpp

@@ -895,4 +895,87 @@ caused by:
   Type 'boolean' could not be converted into 'string')");
 }
 
+// TODO: File a Jira about this
+/*
+TEST_CASE_FIXTURE(Fixture, "unifying_vararg_pack_with_fixed_length_pack_produces_fixed_length_pack")
+{
+    CheckResult result = check(R"(
+        function a(x) return 1 end
+        a(...)
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    REQUIRE(bool(getMainModule()->getModuleScope()->varargPack));
+
+    TypePackId varargPack = *getMainModule()->getModuleScope()->varargPack;
+
+    auto iter = begin(varargPack);
+    auto endIter = end(varargPack);
+
+    CHECK(iter != endIter);
+    ++iter;
+    CHECK(iter == endIter);
+
+    CHECK(!iter.tail());
+}
+*/
+
+TEST_CASE_FIXTURE(Fixture, "dont_ice_if_a_TypePack_is_an_error")
+{
+    CheckResult result = check(R"(
+        --!strict
+        function f(s)
+            print(s)
+            return f
+        end
+
+        f("foo")("bar")
+    )");
+}
+
+TEST_CASE_FIXTURE(Fixture, "cyclic_type_packs")
+{
+    // this has a risk of creating cyclic type packs, causing infinite loops / OOMs
+    check(R"(
+--!nonstrict
+_ += _(_,...)
+repeat
+_ += _(...)
+until ... + _
+)");
+
+    check(R"(
+--!nonstrict
+_ += _(_(...,...),_(...))
+repeat
+until _
+)");
+}
+
+TEST_CASE_FIXTURE(Fixture, "detect_cyclic_typepacks")
+{
+    CheckResult result = check(R"(
+        type ( ... ) ( ) ;
+        ( ... ) ( - - ... ) ( - ... )
+        type = ( ... ) ;
+        ( ... ) (  ) ( ... ) ;
+        ( ... ) ""
+    )");
+
+    CHECK_LE(0, result.errors.size());
+}
+
+TEST_CASE_FIXTURE(Fixture, "detect_cyclic_typepacks2")
+{
+    CheckResult result = check(R"(
+        function _(l0:((typeof((pcall)))|((((t0)->())|(typeof(-67108864)))|(any)))|(any),...):(((typeof(0))|(any))|(any),typeof(-67108864),any)
+            xpcall(_,_,_)
+            _(_,_,_)
+        end
+    )");
+
+    CHECK_LE(0, result.errors.size());
+}
+
 TEST_SUITE_END();

tests/TypeInfer.unionTypes.test.cpp

@@ -496,4 +496,20 @@ caused by:
   None of the union options are compatible. For example: Table type 'a' not compatible with type 'X' because the former is missing field 'x')");
 }
 
+// We had a bug where a cyclic union caused a stack overflow.
+// ex type U = number | U
+TEST_CASE_FIXTURE(Fixture, "dont_allow_cyclic_unions_to_be_inferred")
+{
+    CheckResult result = check(R"(
+        --!strict
+
+        function f(a, b)
+            a:g(b or {})
+            a:g(b)
+        end
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+}
+
 TEST_SUITE_END();

tests/conformance/basic.lua

@@ -833,6 +833,17 @@ assert((function()
     return sum
 end)() == 105)
 
+-- shrinking array part
+assert((function()
+    local t = table.create(100, 42)
+    for i=1,90 do t[i] = nil end
+    t[101] = 42
+    local sum = 0
+    for _,v in ipairs(t) do sum += v end
+    for _,v in pairs(t) do sum += v end
+    return sum
+end)() == 462)
+
 -- upvalues: recursive capture
 assert((function() local function fact(n) return n < 1 and 1 or n * fact(n-1) end return fact(5) end)() == 120)
 
@@ -881,6 +892,14 @@ end)() == "6,8,10")
 -- typeof == type in absence of custom userdata
 assert(concat(typeof(5), typeof(nil), typeof({}), typeof(newproxy())) == "number,nil,table,userdata")
 
+-- type/typeof/newproxy interaction with metatables: __type doesn't work intentionally to avoid spoofing
+assert((function()
+    local ud = newproxy(true)
+    getmetatable(ud).__type = "number"
+
+    return concat(type(ud),typeof(ud))
+end)() == "userdata,userdata")
+
 testgetfenv() -- DONT MOVE THIS LINE
 
 return 'OK'

tests/conformance/debugger.lua

@@ -3,14 +3,14 @@ print "testing debugger" -- note, this file can't run in isolation from C tests
 
 local a = 5
 
-function foo(b)
+function foo(b, ...)
 	print("in foo", b)
 	a = 6
 end
 
 breakpoint(8)
 
-foo(50)
+foo(50, 42)
 
 breakpoint(16) -- next line
 print("here")

tests/conformance/errors.lua

@@ -305,4 +305,6 @@ assert(ecall(function() return "a" + "b" end) == "attempt to perform arithmetic
 assert(ecall(function() return 1 > nil end) == "attempt to compare nil < number") -- note reversed order (by design)
 assert(ecall(function() return "a" <= 5 end) == "attempt to compare string <= number")
 
+assert(ecall(function() local t = {} setmetatable(t, { __newindex = function(t,i,v) end }) t[nil] = 2 end) == "table index is nil")
+
 return('OK')

tests/conformance/interrupt.lua

@@ -0,0 +1,11 @@
+-- This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+print("testing interrupts")
+
+function foo()
+    for i=1,10 do end
+    return
+end
+
+foo()
+
+return "OK"

tools/lldb-formatters.lldb

@@ -1,2 +0,0 @@
-type synthetic add -x "^Luau::Variant<.+>$" -l LuauVisualize.LuauVariantSyntheticChildrenProvider
-type summary add -x "^Luau::Variant<.+>$" -l LuauVisualize.luau_variant_summary

tools/lldb_formatters.lldb

@@ -0,0 +1,2 @@
+type synthetic add -x "^Luau::Variant<.+>$" -l lldb_formatters.LuauVariantSyntheticChildrenProvider
+type summary add -x "^Luau::Variant<.+>$" -l lldb_formatters.luau_variant_summary