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
  H4 : 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
  e : elt
  e' : elt
  H2 : find k m = Some e
  H3 : find k m' = Some e'
  H5 : forall k : key, find k m' = find k m'
  H6 : forall k : key, find k m = find k m
  ============================
   (eq_elt e e')


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.