Goal:
    A : Type  B : Type  C : Type  R : A → B → C → Type
  ============================
   (eq_refl = eq_refl)


DEBUG:Going to execute:
let y' := eval hnf in y in
           change_no_check (x' = y')
DEBUG LTAC Evaluated term: eq_refl
DEBUG LTAC Evaluated term: eq_refl