Sync to upstream/release/671 (#1787)

# General

* Internally rename `ClassType` to `ExternType`. In definition files,
the syntax to define these types has changed to `declare extern type Foo
with prop: type end`
* Add `luarequire_registermodule` to Luau.Require
* Support yieldable Luau C functions calling other functions
* Store return types as `AstTypePack*` on Ast nodes

## New Solver

* Improve the logic that determines constraint dispatch ordering
* Fix a crash in the type solver that arose when using multi-return
functions with `string.format`
* Fix #1736
* Initial steps toward rethinking function generalization:
* Instead of generalizing every type in a function all at once, we will
instead generalize individual type variables once their bounds have been
fully resolved. This will make it possible to properly interleave type
function reduction and generalization.
* Magic functions are no longer considered magical in cases where they
are not explicitly called by the code.
* The most prominent example of this is in `for..in` loops where the
function call is part of the desugaring process.
* Almost all magic functions work by directly inspecting the AST, so
they can't work without an AST fragment anyway.
* Further, none of the magic functions we have are usefully used in this
way.

Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Author: 8 people

Analysis/include/Luau/AutocompleteTypes.h

@@ -57,7 +57,7 @@ struct AutocompleteEntry
     // Set if this suggestion matches the type expected in the context
     TypeCorrectKind typeCorrect = TypeCorrectKind::None;
 
-    std::optional<const ClassType*> containingClass = std::nullopt;
+    std::optional<const ExternType*> containingExternType = std::nullopt;
     std::optional<const Property*> prop = std::nullopt;
     std::optional<std::string> documentationSymbol = std::nullopt;
     Tags tags;
@@ -85,7 +85,7 @@ struct AutocompleteResult
 };
 
 using StringCompletionCallback =
-    std::function<std::optional<AutocompleteEntryMap>(std::string tag, std::optional<const ClassType*> ctx, std::optional<std::string> contents)>;
+    std::function<std::optional<AutocompleteEntryMap>(std::string tag, std::optional<const ExternType*> ctx, std::optional<std::string> contents)>;
 
 constexpr char kGeneratedAnonymousFunctionEntryName[] = "function (anonymous autofilled)";
 

Analysis/include/Luau/ConstraintGenerator.h

@@ -3,6 +3,7 @@
 
 #include "Luau/Ast.h"
 #include "Luau/Constraint.h"
+#include "Luau/ConstraintSet.h"
 #include "Luau/ControlFlow.h"
 #include "Luau/DataFlowGraph.h"
 #include "Luau/EqSatSimplification.h"
@@ -91,9 +92,8 @@ struct ConstraintGenerator
     // Constraints that go straight to the solver.
     std::vector<ConstraintPtr> constraints;
 
-    // Constraints that do not go to the solver right away.  Other constraints
-    // will enqueue them during solving.
-    std::vector<ConstraintPtr> unqueuedConstraints;
+    // The set of all free types introduced during constraint generation.
+    DenseHashSet<TypeId> freeTypes{nullptr};
 
     // Map a function's signature scope back to its signature type.
     DenseHashMap<Scope*, TypeId> scopeToFunction{nullptr};
@@ -151,6 +151,9 @@ struct ConstraintGenerator
         std::vector<RequireCycle> requireCycles
     );
 
+    ConstraintSet run(AstStatBlock* block);
+    ConstraintSet runOnFragment(const ScopePtr& resumeScope, AstStatBlock* block);
+
     /**
      * The entry point to the ConstraintGenerator. This will construct a set
      * of scopes, constraints, and free types that can be solved later.
@@ -269,7 +272,7 @@ struct ConstraintGenerator
     ControlFlow visit(const ScopePtr& scope, AstStatTypeAlias* alias);
     ControlFlow visit(const ScopePtr& scope, AstStatTypeFunction* function);
     ControlFlow visit(const ScopePtr& scope, AstStatDeclareGlobal* declareGlobal);
-    ControlFlow visit(const ScopePtr& scope, AstStatDeclareClass* declareClass);
+    ControlFlow visit(const ScopePtr& scope, AstStatDeclareExternType* declareExternType);
     ControlFlow visit(const ScopePtr& scope, AstStatDeclareFunction* declareFunction);
     ControlFlow visit(const ScopePtr& scope, AstStatError* error);
 
@@ -481,9 +484,4 @@ struct ConstraintGenerator
     TypeId simplifyUnion(const ScopePtr& scope, Location location, TypeId left, TypeId right);
 };
 
-/** Borrow a vector of pointers from a vector of owning pointers to constraints.
- */
-std::vector<NotNull<Constraint>> borrowConstraints(const std::vector<ConstraintPtr>& constraints);
-
-
 } // namespace Luau

Analysis/include/Luau/ConstraintSet.h

@@ -0,0 +1,32 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+
+#pragma once
+
+#include "Luau/Constraint.h"
+#include "Luau/DenseHash.h"
+#include "Luau/Error.h"
+
+#include <vector>
+
+namespace Luau
+{
+
+struct ConstraintSet
+{
+    NotNull<Scope> rootScope;
+
+    std::vector<ConstraintPtr> constraints;
+
+    // The set of all free types created during constraint generation
+    DenseHashSet<TypeId> freeTypes{nullptr};
+
+    // Map a function's signature scope back to its signature type.   Once we've
+    // dispatched all of the constraints pertaining to a particular free type,
+    // we use this mapping to generalize that free type.
+    DenseHashMap<Scope*, TypeId> scopeToFunction{nullptr};
+
+    // It is pretty uncommon for constraint generation to itself produce errors, but it can happen.
+    std::vector<TypeError> errors;
+};
+
+}

Analysis/include/Luau/ConstraintSolver.h

@@ -3,6 +3,7 @@
 #pragma once
 
 #include "Luau/Constraint.h"
+#include "Luau/ConstraintSet.h"
 #include "Luau/DataFlowGraph.h"
 #include "Luau/DenseHash.h"
 #include "Luau/EqSatSimplification.h"
@@ -87,6 +88,7 @@ struct ConstraintSolver
     NotNull<Simplifier> simplifier;
     NotNull<TypeFunctionRuntime> typeFunctionRuntime;
     // The entire set of constraints that the solver is trying to resolve.
+    ConstraintSet constraintSet;
     std::vector<NotNull<Constraint>> constraints;
     NotNull<DenseHashMap<Scope*, TypeId>> scopeToFunction;
     NotNull<Scope> rootScope;
@@ -140,6 +142,19 @@ struct ConstraintSolver
 
     DenseHashMap<TypeId, const Constraint*> typeFunctionsToFinalize{nullptr};
 
+    explicit ConstraintSolver(
+        NotNull<Normalizer> normalizer,
+        NotNull<Simplifier> simplifier,
+        NotNull<TypeFunctionRuntime> typeFunctionRuntime,
+        ModuleName moduleName,
+        NotNull<ModuleResolver> moduleResolver,
+        std::vector<RequireCycle> requireCycles,
+        DcrLogger* logger,
+        NotNull<const DataFlowGraph> dfg,
+        TypeCheckLimits limits,
+        ConstraintSet constraintSet
+    );
+
     explicit ConstraintSolver(
         NotNull<Normalizer> normalizer,
         NotNull<Simplifier> simplifier,
@@ -174,6 +189,9 @@ struct ConstraintSolver
     bool isDone() const;
 
 private:
+    /// A helper that does most of the setup work that is shared between the two constructors.
+    void initFreeTypeTracking();
+
     void generalizeOneType(TypeId ty);
 
     /**
@@ -432,6 +450,10 @@ struct ConstraintSolver
     void fillInDiscriminantTypes(NotNull<const Constraint> constraint, const std::vector<std::optional<TypeId>>& discriminantTypes);
 };
 
+/** Borrow a vector of pointers from a vector of owning pointers to constraints.
+ */
+std::vector<NotNull<Constraint>> borrowConstraints(const std::vector<ConstraintPtr>& constraints);
+
 void dump(NotNull<Scope> rootScope, struct ToStringOptions& opts);
 
 } // namespace Luau

Analysis/include/Luau/DataFlowGraph.h

@@ -173,7 +173,7 @@ struct DataFlowGraphBuilder
     ControlFlow visit(AstStatTypeFunction* f);
     ControlFlow visit(AstStatDeclareGlobal* d);
     ControlFlow visit(AstStatDeclareFunction* d);
-    ControlFlow visit(AstStatDeclareClass* d);
+    ControlFlow visit(AstStatDeclareExternType* d);
     ControlFlow visit(AstStatError* error);
 
     DataFlowResult visitExpr(AstExpr* e);

Analysis/include/Luau/Error.h

@@ -332,11 +332,11 @@ struct TypePackMismatch
     bool operator==(const TypePackMismatch& rhs) const;
 };
 
-struct DynamicPropertyLookupOnClassesUnsafe
+struct DynamicPropertyLookupOnExternTypesUnsafe
 {
     TypeId ty;
 
-    bool operator==(const DynamicPropertyLookupOnClassesUnsafe& rhs) const;
+    bool operator==(const DynamicPropertyLookupOnExternTypesUnsafe& rhs) const;
 };
 
 struct UninhabitedTypeFunction
@@ -499,7 +499,7 @@ using TypeErrorData = Variant<
     TypesAreUnrelated,
     NormalizationTooComplex,
     TypePackMismatch,
-    DynamicPropertyLookupOnClassesUnsafe,
+    DynamicPropertyLookupOnExternTypesUnsafe,
     UninhabitedTypeFunction,
     UninhabitedTypePackFunction,
     WhereClauseNeeded,

Analysis/include/Luau/FileResolver.h

@@ -117,8 +117,7 @@ struct FileResolver
         return std::nullopt;
     }
 
-    // Make non-virtual when removing FFlagLuauImproveRequireByStringAutocomplete.
-    virtual std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const;
+    std::optional<RequireSuggestions> getRequireSuggestions(const ModuleName& requirer, const std::optional<std::string>& pathString) const;
 
     std::shared_ptr<RequireSuggester> requireSuggester;
 };

Analysis/include/Luau/Instantiation.h

@@ -133,9 +133,9 @@ struct GenericTypeFinder : TypeOnceVisitor
         return false;
     }
 
-    bool visit(TypeId ty, const Luau::ClassType&) override
+    bool visit(TypeId ty, const Luau::ExternType&) override
     {
-        // During function instantiation, classes are not traversed even if they have generics
+        // During function instantiation, extern types are not traversed even if they have generics
         return false;
     }
 };

Analysis/include/Luau/Normalize.h

@@ -181,7 +181,7 @@ struct NormalizedStringType
 
 bool isSubtype(const NormalizedStringType& subStr, const NormalizedStringType& superStr);
 
-struct NormalizedClassType
+struct NormalizedExternType
 {
     /** Has the following structure:
      *
@@ -192,7 +192,7 @@ struct NormalizedClassType
      *
      * Each TypeId is a class type.
      */
-    std::unordered_map<TypeId, TypeIds> classes;
+    std::unordered_map<TypeId, TypeIds> externTypes;
 
     /**
      * In order to maintain a consistent insertion order, we use this vector to
@@ -245,7 +245,7 @@ enum class NormalizationResult
 };
 
 // A normalized type is either any, unknown, or one of the form P | T | F | G where
-// * P is a union of primitive types (including singletons, classes and the error type)
+// * P is a union of primitive types (including singletons, extern types and the error type)
 // * T is a union of table types
 // * F is a union of an intersection of function types
 // * G is a union of generic/free/blocked types, intersected with a normalized type
@@ -260,7 +260,7 @@ struct NormalizedType
     // This type is either never, boolean type, or a boolean singleton.
     TypeId booleans;
 
-    NormalizedClassType classes;
+    NormalizedExternType externTypes;
 
     // The error part of the type.
     // This type is either never or the error type.
@@ -333,7 +333,7 @@ struct NormalizedType
     // Helpers that improve readability of the above (they just say if the component is present)
     bool hasTops() const;
     bool hasBooleans() const;
-    bool hasClasses() const;
+    bool hasExternTypes() const;
     bool hasErrors() const;
     bool hasNils() const;
     bool hasNumbers() const;
@@ -391,10 +391,10 @@ class Normalizer
     void unionTysWithTy(TypeIds& here, TypeId there);
     TypeId unionOfTops(TypeId here, TypeId there);
     TypeId unionOfBools(TypeId here, TypeId there);
-    void unionClassesWithClass(TypeIds& heres, TypeId there);
-    void unionClasses(TypeIds& heres, const TypeIds& theres);
-    void unionClassesWithClass(NormalizedClassType& heres, TypeId there);
-    void unionClasses(NormalizedClassType& heres, const NormalizedClassType& theres);
+    void unionExternTypesWithExternType(TypeIds& heres, TypeId there);
+    void unionExternTypes(TypeIds& heres, const TypeIds& theres);
+    void unionExternTypesWithExternType(NormalizedExternType& heres, TypeId there);
+    void unionExternTypes(NormalizedExternType& heres, const NormalizedExternType& theres);
     void unionStrings(NormalizedStringType& here, const NormalizedStringType& there);
     std::optional<TypePackId> unionOfTypePacks(TypePackId here, TypePackId there);
     std::optional<TypeId> unionOfFunctions(TypeId here, TypeId there);
@@ -423,8 +423,8 @@ class Normalizer
     // ------- Normalizing intersections
     TypeId intersectionOfTops(TypeId here, TypeId there);
     TypeId intersectionOfBools(TypeId here, TypeId there);
-    void intersectClasses(NormalizedClassType& heres, const NormalizedClassType& theres);
-    void intersectClassesWithClass(NormalizedClassType& heres, TypeId there);
+    void intersectExternTypes(NormalizedExternType& heres, const NormalizedExternType& theres);
+    void intersectExternTypesWithExternType(NormalizedExternType& heres, TypeId there);
     void intersectStrings(NormalizedStringType& here, const NormalizedStringType& there);
     std::optional<TypePackId> intersectionOfTypePacks(TypePackId here, TypePackId there);
     std::optional<TypeId> intersectionOfTables(TypeId here, TypeId there, SeenTablePropPairs& seenTablePropPairs, Set<TypeId>& seenSet);

Analysis/include/Luau/Quantify.h

@@ -16,7 +16,7 @@ struct Scope;
 
 void quantify(TypeId ty, TypeLevel level);
 
-// TODO: This is eerily similar to the pattern that NormalizedClassType
+// TODO: This is eerily similar to the pattern that NormalizedExternType
 // implements. We could, and perhaps should, merge them together.
 template<typename K, typename V>
 struct OrderedMap

Analysis/include/Luau/Subtyping.h

@@ -22,7 +22,7 @@ struct InternalErrorReporter;
 
 class TypeIds;
 class Normalizer;
-struct NormalizedClassType;
+struct NormalizedExternType;
 struct NormalizedFunctionType;
 struct NormalizedStringType;
 struct NormalizedType;
@@ -121,7 +121,7 @@ struct SubtypingEnvironment
     DenseHashMap<TypePackId, TypePackId> mappedGenericPacks{nullptr};
 
     /*
-     * See the test cyclic_tables_are_assumed_to_be_compatible_with_classes for
+     * See the test cyclic_tables_are_assumed_to_be_compatible_with_extern_types for
      * details.
      *
      * An empty value is equivalent to a nonexistent key.
@@ -229,9 +229,8 @@ struct Subtyping
     SubtypingResult isCovariantWith(SubtypingEnvironment& env, const TableType* subTable, const TableType* superTable, NotNull<Scope> scope);
     SubtypingResult isCovariantWith(SubtypingEnvironment& env, const MetatableType* subMt, const MetatableType* superMt, NotNull<Scope> scope);
     SubtypingResult isCovariantWith(SubtypingEnvironment& env, const MetatableType* subMt, const TableType* superTable, NotNull<Scope> scope);
-    SubtypingResult isCovariantWith(SubtypingEnvironment& env, const ClassType* subClass, const ClassType* superClass, NotNull<Scope> scope);
-    SubtypingResult
-    isCovariantWith(SubtypingEnvironment& env, TypeId subTy, const ClassType* subClass, TypeId superTy, const TableType* superTable, NotNull<Scope>);
+    SubtypingResult isCovariantWith(SubtypingEnvironment& env, const ExternType* subExternType, const ExternType* superExternType, NotNull<Scope> scope);
+    SubtypingResult isCovariantWith(SubtypingEnvironment& env, TypeId subTy, const ExternType* subExternType, TypeId superTy, const TableType* superTable, NotNull<Scope>);
     SubtypingResult isCovariantWith(
         SubtypingEnvironment& env,
         const FunctionType* subFunction,
@@ -259,11 +258,11 @@ struct Subtyping
     );
     SubtypingResult isCovariantWith(
         SubtypingEnvironment& env,
-        const NormalizedClassType& subClass,
-        const NormalizedClassType& superClass,
+        const NormalizedExternType& subExternType,
+        const NormalizedExternType& superExternType,
         NotNull<Scope> scope
     );
-    SubtypingResult isCovariantWith(SubtypingEnvironment& env, const NormalizedClassType& subClass, const TypeIds& superTables, NotNull<Scope> scope);
+    SubtypingResult isCovariantWith(SubtypingEnvironment& env, const NormalizedExternType& subExternType, const TypeIds& superTables, NotNull<Scope> scope);
     SubtypingResult isCovariantWith(
         SubtypingEnvironment& env,
         const NormalizedStringType& subString,

Analysis/include/Luau/ToString.h

@@ -44,6 +44,7 @@ struct ToStringOptions
     bool hideTableKind = false;                   // If true, all tables will be surrounded with plain '{}'
     bool hideNamedFunctionTypeParameters = false; // If true, type parameters of functions will be hidden at top-level.
     bool hideFunctionSelfArgument = false;        // If true, `self: X` will be omitted from the function signature if the function has self
+    bool hideTableAliasExpansions = false;        // If true, all table aliases will not be expanded
     bool useQuestionMarks = true;                 // If true, use a postfix ? for options, else write them out as unions that include nil.
     size_t maxTableLength = size_t(FInt::LuauTableTypeMaximumStringifierLength); // Only applied to TableTypes
     size_t maxTypeLength = size_t(FInt::LuauTypeMaximumStringifierLength);