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 x : key × elt,
       List.In x (elements m) ->
       let
       '(k, _) := x in
        match find k m with
        | Some x0 =>
            match find k m' with
            | Some y0 => eq_elt x0 y0
            | None => False
            end
        | None => match find k m' with
                  | Some _ => False
                  | None => True
                  end
        end
  H3 : forall x : key × elt,
       List.In x (elements m') ->
       let
       '(k, _) := x in
        match find k m with
        | Some x0 =>
            match find k m' with
            | Some y0 => eq_elt x0 y0
            | None => False
            end
        | None => match find k m' with
                  | Some _ => False
                  | None => True
                  end
        end
  k : key
  k0 : key
  e : elt
  H2 : E.eq k (k0, e).1
  H4 : List.In (k0, e) (elements 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: (H3 ?x)
DEBUG LTAC Evaluated term: (List.In ?x (elements m') ->
                            let
                            '(k, _) := ?x in
                             match find k m with
                             | Some x =>
                                 match find k m' with
                                 | Some y0 => eq_elt x y0
                                 | None => False
                                 end
                             | None =>
                                 match find k m' with
                                 | Some _ => False
                                 | None => True
                                 end
                             end)
Level 7: type of H
 has value 
(List.In ?x (elements m') ->
 let
 '(k, _) := ?x in
  match find k m with
  | Some x =>
      match find k m' with
      | Some y0 => eq_elt x y0
      | None => False
      end
  | None => match find k m' with
            | Some _ => False
            | None => True
            end
  end)