Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -1605,6 +1605,11 @@
         OS << *ED;
       else
         continue;
+    } else if (const auto *CD = dyn_cast<ObjCCategoryDecl>(DC)) {
+      if (CD->IsClassExtension())
+         OS << "(class extension)";
+      else
+        OS << *CD;
     } else {
       OS << *cast<NamedDecl>(DC);
     }