Goal:
  
  f : Edge.t -> Edge.t
  es : EdgeSet.t
  e : EdgeSet.elt
  x : Edge.t
  __view_subject_1_ : EdgeSet.In x es
  ============================
   (EdgeSet.In x es)


DEBUG:Going to execute:
trivial; hnf; intros; (solve
            [ do
            ![ solve
             [ trivial | apply : eq_sym ; trivial ]
             | discriminate
             | contradiction
             | Ltac.split ]
            | case not_locked_false_eq_true; Ltac.assumption
            | match goal with
              | H:~ _ |- _ => solve [ case H; trivial ]
              end ])