Test "merging" of typedef types across distinct modules. At present,
the AST reader doesn't actually perform a merge, because name lookup
knows how to merge identical typedefs together.

As part of this, teach C/Objective-C name lookup to return multiple
results in all cases, rather than first digging through the attributes
to see if the value is overloadable. This way, we'll catch ambiguous
lookups in C/Objective-C.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147498 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 31a9b3b..479f80f 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -938,6 +938,12 @@
                                         cast<UsingDecl>(OldD)->getQualifier());
   }
 
+  // A typedef of an Objective-C class type can replace an Objective-C class
+  // declaration or definition, and vice versa.
+  if ((isa<TypedefNameDecl>(this) && isa<ObjCInterfaceDecl>(OldD)) ||
+      (isa<ObjCInterfaceDecl>(this) && isa<TypedefNameDecl>(OldD)))
+    return true;
+  
   // For non-function declarations, if the declarations are of the
   // same kind then this must be a redeclaration, or semantic analysis
   // would not have given us the new declaration.