When checking the redeclaration context of a typedef that refers to a

tag of the same name, compare the lookup contexts rather than the
actual contexts. Fixes PR6923.

llvm-svn: 102437

Author: DougGregor

clang/lib/Sema/SemaDecl.cpp

@@ -5029,7 +5029,8 @@ Sema::DeclPtrTy Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
         if (const TagType *TT = TD->getUnderlyingType()->getAs<TagType>()) {
           TagDecl *Tag = TT->getDecl();
           if (Tag->getDeclName() == Name &&
-              Tag->getDeclContext()->Equals(TD->getDeclContext())) {
+              Tag->getDeclContext()->getLookupContext()
+                          ->Equals(TD->getDeclContext()->getLookupContext())) {
             PrevDecl = Tag;
             Previous.clear();
             Previous.addDecl(Tag);

clang/test/SemaCXX/typedef-redecl.cpp

@@ -37,3 +37,14 @@ namespace test1 {
   using namespace a; 
   foo x;
 }
+
+namespace PR6923 {
+  struct A;
+
+  extern "C" {
+    struct A;
+    typedef struct A A;
+  }
+
+  struct A;
+}