Diagnose if an implementation implements a forward class

declaration (and avoid issuing bogus error later on).

llvm-svn: 69928

clang/lib/Sema/SemaDeclObjC.cpp

@@ -623,8 +623,10 @@ Sema::DeclPtrTy Sema::ActOnStartClassImplementation(
   }  else {
     // Is there an interface declaration of this class; if not, warn!
     IDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl); 
-    if (!IDecl)
+    if (!IDecl || IDecl->isForwardDecl()) {
       Diag(ClassLoc, diag::warn_undef_interface) << ClassName;
+      IDecl = 0;
+    }
   }
   
   // Check that super class name is valid class name

clang/test/SemaObjC/class-impl-1.m

@@ -31,3 +31,10 @@ typedef int INTF3; // expected-note {{previous definition is here}}
 
 @implementation INTF4 @end // expected-warning {{cannot find interface declaration for 'INTF4'}}
 
+@class INTF5;
+
+@implementation INTF5 {  // expected-warning {{cannot find interface declaration for 'INTF5'}}
+  int x;
+}
+@end
+

clang/test/SemaObjC/synchronized.m

@@ -1,6 +1,6 @@
 // RUN: clang-cc -fsyntax-only -verify %s
 
-@class PBXTrackableTaskManager;
+@interface PBXTrackableTaskManager @end
 
 @implementation PBXTrackableTaskManager
 - (id) init {}