From 04c4455dd443c67584d59c5d993aaada92233073 Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Tue, 24 Jan 2012 00:40:15 +0000
Subject: [PATCH] objective-c: Ignore with warning forward class declaration
 whose name matches a typedef declaring an object type. // rdar://10733000

llvm-svn: 148760
---
 .../clang/Basic/DiagnosticSemaKinds.td        |  3 ++
 clang/lib/Sema/SemaDeclObjC.cpp               | 15 ++++++----
 clang/test/SemaObjC/forward-class-1.m         |  4 +--
 clang/test/SemaObjC/forward-class-redeclare.m | 29 +++++++++++++++++++
 clang/test/SemaObjC/typedef-class.m           |  4 +--
 5 files changed, 46 insertions(+), 9 deletions(-)
 create mode 100644 clang/test/SemaObjC/forward-class-redeclare.m

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index dfe49108acb9..73f3cda545b6 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2809,6 +2809,9 @@ def err_redefinition_different_type : Error<
   "redefinition of %0 with a different type">;
 def err_redefinition_different_kind : Error<
   "redefinition of %0 as different kind of symbol">;
+def warn_forward_class_redefinition : Warning<
+  "redefinition of forward class %0 of a typedef name of an object type is ignored">,
+  InGroup<DiagGroup<"objc-forward-class-redefinition">>;
 def err_redefinition_different_typedef : Error<
   "%select{typedef|type alias|type alias template}0 redefinition with different types (%1 vs %2)">;
 def err_tag_reference_non_tag : Error<
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index ff92453ca7fb..4264b7105a7f 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -1776,17 +1776,22 @@ Sema::ActOnForwardClassDeclaration(SourceLocation AtClassLoc,
       // typedef NSObject < XCElementTogglerP > XCElementToggler;
       // @class XCElementToggler;
       //
-      // FIXME: Make an extension?
+      // Here we have chosen to ignore the forward class declaration
+      // with a warning. Since this is the implied behavior.
       TypedefNameDecl *TDD = dyn_cast<TypedefNameDecl>(PrevDecl);
       if (!TDD || !TDD->getUnderlyingType()->isObjCObjectType()) {
         Diag(AtClassLoc, diag::err_redefinition_different_kind) << IdentList[i];
         Diag(PrevDecl->getLocation(), diag::note_previous_definition);
       } else {
         // a forward class declaration matching a typedef name of a class refers
-        // to the underlying class.
-        if (const ObjCObjectType *OI =
-              TDD->getUnderlyingType()->getAs<ObjCObjectType>())
-          PrevDecl = OI->getInterface();
+        // to the underlying class. Just ignore the forward class with a warning
+        // as this will force the intended behavior which is to lookup the typedef
+        // name.
+        if (isa<ObjCObjectType>(TDD->getUnderlyingType())) {
+          Diag(AtClassLoc, diag::warn_forward_class_redefinition) << IdentList[i];
+          Diag(PrevDecl->getLocation(), diag::note_previous_definition);
+          continue;
+        }
       }
     }
     
diff --git a/clang/test/SemaObjC/forward-class-1.m b/clang/test/SemaObjC/forward-class-1.m
index e8c36957a31d..30a06358c5ef 100644
--- a/clang/test/SemaObjC/forward-class-1.m
+++ b/clang/test/SemaObjC/forward-class-1.m
@@ -31,14 +31,14 @@
 
 @protocol XCElementP @end
 
-typedef NSObject <XCElementP> XCElement;
+typedef NSObject <XCElementP> XCElement; // expected-note {{previous definition is here}}
 
 @interface XCElementMainImp  {
   XCElement * _editingElement;
 }
 @end
 
-@class XCElement;
+@class XCElement; // expected-warning {{redefinition of forward class 'XCElement' of a typedef name of an object type is ignored}}
 
 @implementation XCElementMainImp
 - (XCElement *)editingElement  { return _editingElement;  }
diff --git a/clang/test/SemaObjC/forward-class-redeclare.m b/clang/test/SemaObjC/forward-class-redeclare.m
new file mode 100644
index 000000000000..80dc33536280
--- /dev/null
+++ b/clang/test/SemaObjC/forward-class-redeclare.m
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// rdar://10733000
+
+@interface NSObject @end
+
+@protocol PLAssetContainer
+@property (readonly, nonatomic, retain) id assets;
+@end
+
+
+typedef NSObject <PLAssetContainer> PLAlbum; // expected-note {{previous definition is here}}
+
+@class PLAlbum; // expected-warning {{redefinition of forward class 'PLAlbum' of a typedef name of an object type is ignore}}
+
+@interface PLPhotoBrowserController
+{
+    PLAlbum *_album;
+}
+@end
+
+@interface WPhotoViewController:PLPhotoBrowserController
+@end
+
+@implementation WPhotoViewController
+- (void)_prepareForContracting
+{
+  (void)_album.assets;
+}
+@end
diff --git a/clang/test/SemaObjC/typedef-class.m b/clang/test/SemaObjC/typedef-class.m
index c983195b243e..bd68397fd969 100644
--- a/clang/test/SemaObjC/typedef-class.m
+++ b/clang/test/SemaObjC/typedef-class.m
@@ -48,13 +48,13 @@ typedef NSObject < XCElementSpacerP > XCElementSpacer;
 @protocol XCElementTogglerP < XCElementP > -(void) setDisplayed:(BOOL) displayed;
 @end
 
-typedef NSObject < XCElementTogglerP > XCElementToggler;
+typedef NSObject < XCElementTogglerP > XCElementToggler; // expected-note {{previous definition is here}}
 
 @interface XCElementRootFace:NSObject {} @end
 
 @interface XCElementFace:XCElementRootFace {} @end
 
-@class XCElementToggler; 
+@class XCElementToggler;  // expected-warning {{redefinition of forward class 'XCElementToggler' of a typedef name of an object type is ignored}}
 
 @interface XCRASlice:XCElementFace {} @end