Fix a typo introduced in r172665.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172682 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/DeclObjC.h b/include/clang/AST/DeclObjC.h
index e7fa5e7..5464957 100644
--- a/include/clang/AST/DeclObjC.h
+++ b/include/clang/AST/DeclObjC.h
@@ -932,7 +932,7 @@
 
     friend bool operator==(filtered_category_iterator X,
                            filtered_category_iterator Y) {
-      return X.Current = Y.Current;
+      return X.Current == Y.Current;
     }
 
     friend bool operator!=(filtered_category_iterator X,