b : A y : A t14.lean:12:8: error: unknown identifier 'c' a : foo.A x : foo.A t14.lean:19:8: error: unknown identifier 'c' t14.lean:23:27: error: invalid 'using' command option, mixing explicit and implicit 'using' options a : A c : A A : Type f a c : A foo.f foo.a foo.c : foo.A t14.lean:46:8: error: unknown identifier 'a' f a c : A t14.lean:52:9: error: unexpected token