From 3ee91fad906363c4f65d6e15ed4808c23972593c Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Thu, 23 Jun 2011 23:16:19 +0000
Subject: [PATCH] When forming a cycle in objc's inheritance hierarchy,
 diagnose it properly and don't throw clang into an infinit loop. //
 rdar://9653341

llvm-svn: 133773
---
 clang/include/clang/Basic/DiagnosticSemaKinds.td |  2 ++
 clang/lib/Sema/SemaDeclObjC.cpp                  |  7 +++++--
 clang/test/SemaObjC/class-proto-1.m              |  4 ++--
 clang/test/SemaObjC/forward-class-1.m            | 15 +++++++++++++--
 clang/test/SemaObjC/undef-superclass-1.m         |  6 +++---
 5 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index c734c064e7fe..84aac0c14f90 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -330,6 +330,8 @@ def err_duplicate_class_def : Error<
   "duplicate interface definition for class %0">;
 def err_undef_superclass : Error<
   "cannot find interface declaration for %0, superclass of %1">;
+def err_forward_superclass : Error<
+  "attempting to use the forward class %0 as superclass of %1">;
 def err_no_nsconstant_string_class : Error<
   "cannot find interface declaration for %0">;
 def err_recursive_superclass : Error<
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index b54e2425b2cd..3bbe421cd144 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -491,10 +491,13 @@ ActOnStartClassInterface(SourceLocation AtInterfaceLoc,
         if (!SuperClassDecl)
           Diag(SuperLoc, diag::err_undef_superclass)
             << SuperName << ClassName << SourceRange(AtInterfaceLoc, ClassLoc);
-        else if (SuperClassDecl->isForwardDecl())
-          Diag(SuperLoc, diag::err_undef_superclass)
+        else if (SuperClassDecl->isForwardDecl()) {
+          Diag(SuperLoc, diag::err_forward_superclass)
             << SuperClassDecl->getDeclName() << ClassName
             << SourceRange(AtInterfaceLoc, ClassLoc);
+          Diag(SuperClassDecl->getLocation(), diag::note_forward_class);
+          SuperClassDecl = 0;
+        }
       }
       IDecl->setSuperClass(SuperClassDecl);
       IDecl->setSuperClassLoc(SuperLoc);
diff --git a/clang/test/SemaObjC/class-proto-1.m b/clang/test/SemaObjC/class-proto-1.m
index 246b5002f67f..80309764335b 100644
--- a/clang/test/SemaObjC/class-proto-1.m
+++ b/clang/test/SemaObjC/class-proto-1.m
@@ -23,9 +23,9 @@
 
 @interface E2 <p1,p2,p3> @end  // expected-warning {{cannot find protocol definition for 'p3'}}
 
-@class U1, U2;
+@class U1, U2; // expected-note {{forward class is declared here}}
 
-@interface E3 : U1 @end // expected-error {{cannot find interface declaration for 'U1', superclass of 'E3'}}
+@interface E3 : U1 @end // expected-error {{attempting to use the forward class 'U1' as superclass of 'E3'}}
 
 
 @interface I3 : E3  @end
diff --git a/clang/test/SemaObjC/forward-class-1.m b/clang/test/SemaObjC/forward-class-1.m
index ab213fb4ce72..de94e884aee2 100644
--- a/clang/test/SemaObjC/forward-class-1.m
+++ b/clang/test/SemaObjC/forward-class-1.m
@@ -1,9 +1,9 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-@class FOO, BAR;
+@class FOO, BAR; // expected-note {{forward class is declared here}}
 @class FOO, BAR;
 
-@interface INTF : FOO	// expected-error {{cannot find interface declaration for 'FOO', superclass of 'INTF'}}
+@interface INTF : FOO	// expected-error {{attempting to use the forward class 'FOO' as superclass of 'INTF'}}
 @end
 
 @interface FOO 
@@ -45,3 +45,14 @@ typedef NSObject <XCElementP> XCElement;
 @end
 
 
+// rdar://9653341
+@class B; // expected-note {{forward class is declared here}}
+@interface A : B {} // expected-error {{attempting to use the forward class 'B' as superclass of 'A'}}
+@end
+
+@interface B : A {}
+@end
+
+@implementation A @end
+@implementation B @end
+
diff --git a/clang/test/SemaObjC/undef-superclass-1.m b/clang/test/SemaObjC/undef-superclass-1.m
index c941f82e435c..41cf1439bd9c 100644
--- a/clang/test/SemaObjC/undef-superclass-1.m
+++ b/clang/test/SemaObjC/undef-superclass-1.m
@@ -1,8 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-@class SUPER, Y;
+@class SUPER, Y; // expected-note 2 {{forward class is declared here}}
 
-@interface INTF :SUPER  // expected-error {{cannot find interface declaration for 'SUPER', superclass of 'INTF'}}
+@interface INTF :SUPER  // expected-error {{attempting to use the forward class 'SUPER' as superclass of 'INTF'}}
 @end
 
 @interface SUPER @end
@@ -13,7 +13,7 @@
 @interface INTF2 : INTF1
 @end
 
-@interface INTF3 : Y // expected-error {{cannot find interface declaration for 'Y', superclass of 'INTF3'}} \
+@interface INTF3 : Y // expected-error {{attempting to use the forward class 'Y' as superclass of 'INTF3'}} \
                      // expected-note{{'INTF3' declared here}}
 @end