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'
  H3 : forall (k : key) (e e' : elt),
       find k m = Some e -> find k m' = Some e' -> eq_elt e e'
  k : key
  x : elt
  H1 : find k m' = Some x
  H4 : forall (k : key) (e : elt),
       find k m = Some e -> exists e0 : elt, find k m' = Some e0
  H5 : forall (k : key) (e : elt),
       find k m' = Some e -> exists e0 : elt, find k m = Some e0
  H2 : forall k : key, find k m' = find k m'
  ============================
   ?T0


DEBUG:Going to execute:
refine v
DEBUG LTAC Evaluated term: E.eq_refl
DEBUG LTAC Evaluated term: (H ?x ?x (E.eq_refl ?x))
Level 10: evaluation returns
H ?x ?x (E.eq_refl ?x) of type constr

Level 6: evaluation returns
H ?x ?x (E.eq_refl ?x) of type constr

Level 2: evaluation returns
H ?x ?x (E.eq_refl ?x) of type constr

Level 1: evaluation returns
H ?x ?x (E.eq_refl ?x) of type constr