[AST] Plumb reduced shape types through local requirements into pack archetypes.

Author: hborla

include/swift/AST/GenericSignature.h

@@ -179,6 +179,8 @@ class GenericSignature {
 
     RequiredProtocols protos;
     LayoutConstraint layout;
+
+    Type packShape;
   };
 
 private:

include/swift/AST/Types.h

@@ -6009,11 +6009,17 @@ BEGIN_CAN_TYPE_WRAPPER(OpenedArchetypeType, ArchetypeType)
   }
 END_CAN_TYPE_WRAPPER(OpenedArchetypeType, ArchetypeType)
 
+/// A wrapper around a shape type to use in ArchetypeTrailingObjects
+/// for PackArchetypeType.
+struct PackShape {
+  Type shapeType;
+};
+
 /// An archetype that represents an opaque element of a type
 /// parameter pack in context.
 class PackArchetypeType final
     : public ArchetypeType,
-      private ArchetypeTrailingObjects<PackArchetypeType> {
+      private ArchetypeTrailingObjects<PackArchetypeType, PackShape> {
   friend TrailingObjects;
   friend ArchetypeType;
 
@@ -6024,18 +6030,23 @@ class PackArchetypeType final
   /// by this routine.
   static CanTypeWrapper<PackArchetypeType>
   get(const ASTContext &Ctx, GenericEnvironment *GenericEnv,
-      Type InterfaceType,
+      Type InterfaceType, Type ShapeType,
       SmallVectorImpl<ProtocolDecl *> &ConformsTo, Type Superclass,
       LayoutConstraint Layout);
 
+  // Returns the reduced shape type for this pack archetype.
+  Type getShape() const {
+    return getTrailingObjects<PackShape>()->shapeType;
+  }
+
   static bool classof(const TypeBase *T) {
     return T->getKind() == TypeKind::PackArchetype;
   }
 
 private:
   PackArchetypeType(const ASTContext &Ctx, GenericEnvironment *GenericEnv,
                     Type InterfaceType, ArrayRef<ProtocolDecl *> ConformsTo,
-                    Type Superclass, LayoutConstraint Layout);
+                    Type Superclass, LayoutConstraint Layout, PackShape Shape);
 };
 BEGIN_CAN_TYPE_WRAPPER(PackArchetypeType, ArchetypeType)
 END_CAN_TYPE_WRAPPER(PackArchetypeType, ArchetypeType)

lib/AST/GenericEnvironment.cpp

@@ -365,6 +365,7 @@ GenericEnvironment::getOrCreateArchetypeFromInterfaceType(Type depType) {
   if (rootGP->isParameterPack()) {
     assert(getKind() == Kind::Primary);
     result = PackArchetypeType::get(ctx, this, requirements.anchor,
+                                    requirements.packShape,
                                     requirements.protos, superclass,
                                     requirements.layout);
   } else {

lib/AST/RequirementMachine/GenericSignatureQueries.cpp

@@ -76,6 +76,8 @@ RequirementMachine::getLocalRequirements(
 
   result.layout = props->getLayoutConstraint();
 
+  result.packShape = getReducedShape(depType);
+
   return result;
 }
 

lib/AST/Type.cpp

@@ -3959,17 +3959,18 @@ UUID OpenedArchetypeType::getOpenedExistentialID() const {
 PackArchetypeType::PackArchetypeType(
     const ASTContext &Ctx, GenericEnvironment *GenericEnv, Type InterfaceType,
     ArrayRef<ProtocolDecl *> ConformsTo, Type Superclass,
-    LayoutConstraint Layout)
+    LayoutConstraint Layout, PackShape Shape)
     : ArchetypeType(TypeKind::PackArchetype, Ctx,
                     RecursiveTypeProperties::HasArchetype, InterfaceType,
                     ConformsTo, Superclass, Layout, GenericEnv) {
   assert(InterfaceType->isParameterPack());
+  *getTrailingObjects<PackShape>() = Shape;
 }
 
 CanPackArchetypeType
 PackArchetypeType::get(const ASTContext &Ctx,
                        GenericEnvironment *GenericEnv,
-                       Type InterfaceType,
+                       Type InterfaceType, Type ShapeType,
                        SmallVectorImpl<ProtocolDecl *> &ConformsTo,
                        Type Superclass, LayoutConstraint Layout) {
   assert(!Superclass || Superclass->getClassOrBoundGenericClass());
@@ -3981,12 +3982,14 @@ PackArchetypeType::get(const ASTContext &Ctx,
   auto arena = AllocationArena::Permanent;
   void *mem =
       Ctx.Allocate(PackArchetypeType::totalSizeToAlloc<ProtocolDecl *, Type,
-                                                       LayoutConstraint>(
-                       ConformsTo.size(), Superclass ? 1 : 0, Layout ? 1 : 0),
+                                                       LayoutConstraint, PackShape>(
+                       ConformsTo.size(), Superclass ? 1 : 0, Layout ? 1 : 0,
+                       /*shapeSize*/1),
                    alignof(PackArchetypeType), arena);
 
   return CanPackArchetypeType(::new (mem) PackArchetypeType(
-      Ctx, GenericEnv, InterfaceType, ConformsTo, Superclass, Layout));
+      Ctx, GenericEnv, InterfaceType, ConformsTo, Superclass, Layout,
+      {ShapeType}));
 }
 
 ElementArchetypeType::ElementArchetypeType(

test/Constraints/variadic_generic_functions.swift

@@ -8,6 +8,8 @@ func debugPrint<T...>(_ items: T...)
   }*/
 }
 
+// FIXME: Add diagnostics for 'T' appearing outside of a pack expansion.
+/*
 func max<T...>(_ values: T...) -> T?
   where T: Comparable
 {
@@ -17,6 +19,7 @@ func max<T...>(_ values: T...) -> T?
 func min<T...: Comparable>(_ values: T...) -> T? {
   return nil
 }
+*/
 
 func invalidPacks() {
   func monovariadic1() -> (String...) {} // expected-error {{variadic expansion 'String' must contain at least one variadic generic parameter}}