Merge pull request #4029 from aleksgapp/bugfix/SR-1894

[SR-1894] Consider protocol metatypes as not @objc compatible.

Author: jrose-apple

lib/AST/ASTDumper.cpp

@@ -2477,7 +2477,13 @@ class PrintTypeRepr : public TypeReprVisitor<PrintTypeRepr> {
     printRec(T->getBase());
     OS << ')';
   }
-  
+
+  void visitProtocolTypeRepr(ProtocolTypeRepr *T) {
+    printCommon(T, "type_protocol") << '\n';
+    printRec(T->getBase());
+    OS << ')';
+  }
+
   void visitInOutTypeRepr(InOutTypeRepr *T) {
     printCommon(T, "type_inout") << '\n';
     printRec(T->getBase());

lib/AST/Type.cpp

@@ -2027,9 +2027,15 @@ static ForeignRepresentableKind
 getObjCObjectRepresentable(Type type, const DeclContext *dc) {
   // @objc metatypes are representable when their instance type is.
   if (auto metatype = type->getAs<AnyMetatypeType>()) {
+    auto instanceType = metatype->getInstanceType();
+
+    // Consider metatype of any existential type as not Objective-C
+    // representable.
+    if (metatype->is<MetatypeType>() && instanceType->isAnyExistentialType())
+      return ForeignRepresentableKind::None;
+
     // If the instance type is not representable verbatim, the metatype is not
     // representable.
-    auto instanceType = metatype->getInstanceType();
     if (getObjCObjectRepresentable(instanceType, dc)
           != ForeignRepresentableKind::Object)
       return ForeignRepresentableKind::None;

test/attr/attr_objc.swift

@@ -314,13 +314,46 @@ class ConcreteContext2 {
 }
 
 class ConcreteContext3 {
+
   func dynamicSelf1() -> Self { return self }
 
   @objc func dynamicSelf1_() -> Self { return self }
   // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
 
   @objc func genericParams<T: NSObject>() -> [T] { return [] }
   // expected-error@-1{{method cannot be marked @objc because it has generic parameters}}
+
+  @objc func returnObjCProtocolMetatype() -> NSCoding.Protocol { return NSCoding.self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  typealias AnotherNSCoding = NSCoding
+  typealias MetaNSCoding1 = NSCoding.Protocol
+  typealias MetaNSCoding2 = AnotherNSCoding.Protocol
+
+  @objc func returnObjCAliasProtocolMetatype1() -> AnotherNSCoding.Protocol { return NSCoding.self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  @objc func returnObjCAliasProtocolMetatype2() -> MetaNSCoding1 { return NSCoding.self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  @objc func returnObjCAliasProtocolMetatype3() -> MetaNSCoding2 { return NSCoding.self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  typealias Composition = NSCopying & NSCoding
+
+  @objc func returnCompositionMetatype1() -> Composition.Protocol { return Composition.self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  @objc func returnCompositionMetatype2() -> (NSCopying & NSCoding).Protocol { return (NSCopying & NSCoding).self }
+  // expected-error@-1{{method cannot be marked @objc because its result type cannot be represented in Objective-C}}
+
+  typealias NSCodingExistential = NSCoding.Type
+
+  @objc func metatypeOfExistentialMetatypePram1(a: NSCodingExistential.Protocol) {}
+  // expected-error@-1{{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
+
+  @objc func metatypeOfExistentialMetatypePram2(a: NSCoding.Type.Protocol) {}
+  // expected-error@-1{{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
 }
 
 func genericContext1<T>(_: T) {