Goal:
    A : Type  B : Type  f : A -> B  g : A -> B  Hfg : f =1 g  x : option A
  ============================
   (forall x : A, f x = g x)


DEBUG:Going to execute:
solve
[ trivial
with eq_true
| Init.reflexivity
| Init.symmetry; trivial
| contradiction
| congruence ]