Goal:
  
  elt : Type
  eq_elt : elt -> elt -> Prop
  m : t elt
  m' : t elt
  H : forall x y : key, E.eq x y -> find x m = find y m
  H0 : forall x y : key, E.eq x y -> find x m' = find y m'
  k : key
  H1 : match find k m with
       | Some x =>
           match find k m' with
           | Some y => eq_elt x y
           | None => False
           end
       | None => match find k m' with
                 | Some _ => False
                 | None => True
                 end
       end
  H3 : forall (k : key) (e : elt),
       find k m' = Some e ->
       match find k m with
       | Some x =>
           match find k m' with
           | Some y => eq_elt x y
           | None => False
           end
       | None => match find k m' with
                 | Some _ => False
                 | None => True
                 end
       end
  x : elt
  H2 : find k m = Some x
  H4 : forall k : key, find k m' = find k m'
  H5 : forall k : key, find k m = find k m
  ============================
   ?T0


DEBUG:Going to execute:
match goal with
           | _ =>
               let __ := lazymatch goal with
                         | _ => guard_tac H
                         end in
               open_constr:((H ltac:((progress tac))))
           | _ =>
               let H := open_constr:((H _)) in
               guarded_specialize_term_under_binders_by' guard_tac H tac
           end
DEBUG LTAC Evaluated term: (H0 ?x)
DEBUG LTAC Evaluated term: (forall y : key,
                            E.eq ?x y -> find ?x m' = find y m')
Level 7: type of H
 has value 
(forall y : key, E.eq ?x y -> find ?x m' = find y m')