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'
  k0 : key
  H1 : match find k0 m with
       | Some x =>
           match find k0 m' with
           | Some y => eq_elt x y
           | None => False
           end
       | None => match find k0 m' with
                 | Some _ => False
                 | None => True
                 end
       end
  H3 : forall (k : key) (e : elt),
       List.In (k, e) (elements m') ->
       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
  e : elt
  H2 : E.eq k k0
  H4 : List.In (k0, e) (elements m)
  H5 : forall k : key, find k m' = find k m'
  H6 : forall k : key, find k m = find k m
  ============================
   ?T0


DEBUG:Going to execute:
let H := open_constr:((H _)) in
           guarded_specialize_term_under_binders_by' guard_tac H tac
DEBUG LTAC Evaluated term: (H3 ?k)
DEBUG LTAC Evaluated term: (forall e0 : elt,
                            List.In (?k, e0) (elements m') ->
                            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)
Level 12: type of H
 has value 
(forall e0 : elt,
 List.In (?k, e0) (elements m') ->
 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)

Level 12: Backtrace:

No matching clauses for match.
Level 11: Backtrace:

No matching clauses for match.
Level 11: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 10: Backtrace:

No matching clauses for match.
Level 9: Backtrace:

No matching clauses for match.
Level 8: Backtrace:

No matching clauses for match.