Goal forall (O obj : Type) (f : O -> obj) (x : O) (e : x = x)
     (T : obj -> obj -> Type) (m : forall x0 : obj, T x0 x0),
   match eq_sym e in (_ = y) return (T (f y) (f x)) with
   | eq_refl => m (f x)
   end = m (f x).
intros.
try case e.
Abort.