-error_ref_attr.nit:20,15--17: Redef Error: Wrong return type. found Int, expected B.
+error_ref_attr.nit:20,15--17: Redef Error: expected `B` return type; got `Int`.
+error_ref_attr.nit:20,15--17: Redef Error: expected `B` type for parameter `a'; got `Int`.