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
  x : elt
  x0 : elt
  H3 : eq_elt x0 x
  H1 : find k m' = Some x
  H4 : exists e : elt, find k m' = Some e
  H5 : find k m = Some x0
  H2 : forall k : key, find k m' = find k m'
  H6 : forall k : key, find k m = find k 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


DEBUG:Going to execute:
first
[ progress destruct_head'_ex
| match goal with
  | H:List.In _ _ |- _ => progress specialize_under_binders_by exact H
  | H:E.eq _ _ |- _ => progress specialize_under_binders_by exact H
  | H:find _ _ = Some _ |- _ => progress specialize_under_binders_by exact H
  end ]
DEBUG LTAC Evaluated term: elt
DEBUG LTAC Evaluated term: Type
Level 3: type of H
 has value 
Type

Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 2: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 2: Backtrace:

No matching clauses for match.
Level 1: Backtrace:

No matching clauses for match.
Level 1: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 0: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No matching clauses for match.
Level 1: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No matching clauses for match.
Level 7: interpretation of term ltac:((let H := fresh in
                                       pose  H  :=
                                        ltac:((let v := tac ltac:(()) in
                                               refine
                                               v)); exact H))
raised the exception
Backtrace:

No matching clauses for match.

Level 7: evaluation of term
raised the exception
Backtrace:

No matching clauses for match.

Level 7: Backtrace:

No matching clauses for match.
Level 6: Backtrace:

No matching clauses for match.
Level 6: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 6: Backtrace:

No matching clauses for match.
Level 6: Backtrace:

No matching clauses for match.
Level 5: Backtrace:

No matching clauses for match.
Level 5: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 5: Backtrace:

No matching clauses for match.
Level 4: Backtrace:

No matching clauses for match.
Level 4: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 1: Backtrace:

No matching clauses for match.
Level 1: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.
Level 1: Backtrace:

No matching clauses for match.