[C++] Fix assign_types.mk
diff --git a/eval.cc b/eval.cc
index 6c7110e..93357b3 100644
--- a/eval.cc
+++ b/eval.cc
@@ -66,8 +66,8 @@
       if (!prev->IsDefined()) {
         rhs = new RecursiveVar(ast->rhs, origin);
       } else {
-        // TODO
-        abort();
+        rhs = prev;
+        needs_assign = false;
       }
       break;
     }