Sema: Tweak inheritance clause checks for primitive AnyObject

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -444,11 +444,19 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
     // protocols.
     if (inheritedTy->isExistentialType()) {
       auto layout = inheritedTy->getExistentialLayout();
-      for (auto proto : layout.getProtocols()) {
-        auto *protoDecl = proto->getDecl();
-        allProtocols.insert(protoDecl);
+
+      // Classes and extensions cannot inherit from subclass
+      // existentials or AnyObject.
+      if (isa<ProtocolDecl>(decl) ||
+          isa<AbstractTypeParamDecl>(decl) ||
+          (!layout.hasExplicitAnyObject &&
+           !layout.superclass)) {
+        for (auto proto : layout.getProtocols()) {
+          auto *protoDecl = proto->getDecl();
+          allProtocols.insert(protoDecl);
+        }
+        continue;
       }
-      continue;
     }
 
     // If this is an enum inheritance clause, check for a raw type.

test/type/subclass_composition.swift

@@ -463,7 +463,7 @@ class ClassConformsToClassProtocolBad2 : ProtoRefinesClass {} // FIXME
 class ClassConformsToClassProtocolGood2 : Derived, ProtoRefinesClass {}
 
 // Subclass existentials inside inheritance clauses
-class CompositionInClassInheritanceClauseAlias : BaseIntAndP2 {
+class CompositionInClassInheritanceClauseAlias : BaseIntAndP2 { // FIXME: expected-error {{}}
   required init(classInit: ()) {
     super.init(classInit: ()) // FIXME: expected-error {{}}
   }