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'
  H1 : 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
  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
  k : key
  x : elt
  H2 : find k m' = Some x
  ============================
   ?T0


DEBUG:Going to execute:
idtac
DEBUG LTAC Evaluated term: (H3 ?k ?e)
DEBUG LTAC Evaluated term: (find ?k m' = Some ?e ->
                            match find ?k m with
                            | Some x0 =>
                                match find ?k m' with
                                | Some y => eq_elt x0 y
                                | None => False
                                end
                            | None =>
                                match find ?k m' with
                                | Some _ => False
                                | None => True
                                end
                            end)
Level 16: type of H
 has value 
(find ?k m' = Some ?e ->
 match find ?k m with
 | Some x0 =>
     match find ?k m' with
     | Some y => eq_elt x0 y
     | None => False
     end
 | None => match find ?k m' with
           | Some _ => False
           | None => True
           end
 end)