Sema: Don't break inheritance cycles in checkCircularity()

It's too late to do it here, because this method is only called as part
of typeCheckDecl() and not validateDecl().

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -603,23 +603,6 @@ static ArrayRef<EnumDecl *> getInheritedForCycleCheck(TypeChecker &tc,
   return { };
 }
 
-// Break the inheritance cycle for a protocol by removing all inherited
-// protocols.
-//
-// FIXME: Just remove the problematic inheritance?
-static void breakInheritanceCycle(ProtocolDecl *proto) {
-}
-
-/// Break the inheritance cycle for a class by removing its superclass.
-static void breakInheritanceCycle(ClassDecl *classDecl) {
-  classDecl->setSuperclass(Type());
-}
-
-/// Break the inheritance cycle for an enum by removing its raw type.
-static void breakInheritanceCycle(EnumDecl *enumDecl) {
-  enumDecl->setRawType(Type());
-}
-
 /// Check for circular inheritance.
 template<typename T>
 static void checkCircularity(TypeChecker &tc, T *decl,
@@ -649,9 +632,6 @@ static void checkCircularity(TypeChecker &tc, T *decl,
                   circularDiag,
                   path.back()->getName());
 
-      decl->setInvalid();
-      decl->setInterfaceType(ErrorType::get(tc.Context));
-      breakInheritanceCycle(decl);
       break;
     }
 
@@ -663,10 +643,6 @@ static void checkCircularity(TypeChecker &tc, T *decl,
                   declKind, (*i)->getName());
     }
 
-    // Set this declaration as invalid, then break the cycle somehow.
-    decl->setInvalid();
-    decl->setInterfaceType(ErrorType::get(tc.Context));
-    breakInheritanceCycle(decl);
     break;
   }
 

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1345,6 +1345,10 @@ static bool diagnoseOverrideForAvailability(ValueDecl *override,
 
 static bool recordOverride(TypeChecker &TC, ValueDecl *override,
                            ValueDecl *base, bool isKnownObjC) {
+  // This can happen with circular inheritance.
+  if (override == base)
+    return true;
+
   ASTContext &ctx = override->getASTContext();
   auto &diags = ctx.Diags;