Goal:
  
  A : Type
  B : Type
  R : A → B → Type
  R' : ∀ (a : A) (b : B), R a b → Type
  ============================
   (eq_refl = eq_refl)


DEBUG:Going to execute:
simpl; DepElim.hnf_eq; DepElim.rewrite_refl_id