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 x x0
  H1 : find k m = Some x
  H4 : find k m' = Some x0
  H5 : exists e : elt, find k m = Some e
  H2 : forall k : key, find k m' = find k m'
  H6 : forall k : key, find k m = find k m
  ============================
   ?T0


DEBUG:Going to execute:
idtac
DEBUG LTAC Evaluated term: (H0 ?x ?y)
DEBUG LTAC Evaluated term: (E.eq ?x ?y -> find ?x m' = find ?y m')
Level 16: type of H
 has value 
(E.eq ?x ?y -> find ?x m' = find ?y m')