AST: Only print DynamicSelfType as 'Self' for class types

This fixes a regression from the previous patch which got
rid of PrintOptions::StripDynamicSelf.

When printing protocol declarations with a BaseType set in
PrintOptions, we can end up with a DynamicSelfType wrapping
a non-class type, if the protocol requirement returned
Self.

Note that this changes the diagnostic for missing protocol
requirements slightly; we used to sometimes refer to 'Self'
even if the conforming type is not a class, which is not
accepted by the type checker anyway. I believe the new
diagnostics are more correct.

Author: slavapestov

lib/AST/ASTPrinter.cpp

@@ -3643,9 +3643,11 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
     auto staticSelfT = T->getSelfType();
 
     if (auto *NTD = staticSelfT->getAnyNominal()) {
-      auto Name = T->getASTContext().Id_Self;
-      Printer.printTypeRef(T, NTD, Name);
-      return;
+      if (isa<ClassDecl>(NTD)) {
+        auto Name = T->getASTContext().Id_Self;
+        Printer.printTypeRef(T, NTD, Name);
+        return;
+      }
     }
 
     visit(staticSelfT);

test/decl/protocol/conforms/fixit_stub.swift

@@ -55,8 +55,8 @@ extension Adopter4: ProtocolWithAssocType2 { //expected-error{{type 'Adopter4' d
 
 
 protocol ProtocolWithSelfRequirement {
-  func foo() -> Self // expected-note{{protocol requires function 'foo()' with type '() -> Self'; do you want to add a stub?}} {{47-47=\n    func foo() -> Adopter5 {\n        <#code#>\n    \}\n}}
-  func foo(lhs: Self, rhs: Self) -> Self //expected-note{{protocol requires function 'foo(lhs:rhs:)' with type '(Adopter5, Adopter5) -> Self'; do you want to add a stub?}} {{47-47=\n    func foo(lhs: Adopter5, rhs: Adopter5) -> Adopter5 {\n        <#code#>\n    \}\n}}
+  func foo() -> Self // expected-note{{protocol requires function 'foo()' with type '() -> Adopter5'; do you want to add a stub?}} {{47-47=\n    func foo() -> Adopter5 {\n        <#code#>\n    \}\n}}
+  func foo(lhs: Self, rhs: Self) -> Self //expected-note{{protocol requires function 'foo(lhs:rhs:)' with type '(Adopter5, Adopter5) -> Adopter5'; do you want to add a stub?}} {{47-47=\n    func foo(lhs: Adopter5, rhs: Adopter5) -> Adopter5 {\n        <#code#>\n    \}\n}}
 }
 
 struct Adopter5: ProtocolWithSelfRequirement { //expected-error{{type 'Adopter5' does not conform to protocol 'ProtocolWithSelfRequirement'}}
@@ -65,8 +65,8 @@ struct Adopter5: ProtocolWithSelfRequirement { //expected-error{{type 'Adopter5'
 
 
 protocol ProtocolWithSelfRequirement2 {
-  func foo() -> Self // expected-note{{protocol requires function 'foo()' with type '() -> Self'; do you want to add a stub?}} {{51-51=\n    func foo() -> Adopter6 {\n        <#code#>\n    \}\n}}
-  func foo(lhs: Self, rhs: Self) -> Self //expected-note{{protocol requires function 'foo(lhs:rhs:)' with type '(Adopter6, Adopter6) -> Self'; do you want to add a stub?}} {{51-51=\n    func foo(lhs: Adopter6, rhs: Adopter6) -> Adopter6 {\n        <#code#>\n    \}\n}}
+  func foo() -> Self // expected-note{{protocol requires function 'foo()' with type '() -> Adopter6'; do you want to add a stub?}} {{51-51=\n    func foo() -> Adopter6 {\n        <#code#>\n    \}\n}}
+  func foo(lhs: Self, rhs: Self) -> Self //expected-note{{protocol requires function 'foo(lhs:rhs:)' with type '(Adopter6, Adopter6) -> Adopter6'; do you want to add a stub?}} {{51-51=\n    func foo(lhs: Adopter6, rhs: Adopter6) -> Adopter6 {\n        <#code#>\n    \}\n}}
 }
 
 struct Adopter6 {}

test/decl/protocol/req/dynamic_self.swift

@@ -1,9 +1,15 @@
 // RUN: %target-parse-verify-swift
 
 protocol P {
-  func f() -> Self // expected-note 2{{protocol requires function 'f()' with type '() -> Self'}}
+  func f() -> Self
+  // expected-note@-1{{protocol requires function 'f()' with type '() -> Self'}}
+  // expected-note@-2{{protocol requires function 'f()' with type '() -> EError'}}
+  // expected-note@-3{{protocol requires function 'f()' with type '() -> SError'}}
 }
 
+// Error: Missing Self method in a class.
+class W : P {} // expected-error{{type 'W' does not conform to protocol 'P'}}
+
 // Okay: Self method in class.
 class X : P {
   func f() -> Self { return self }