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
  x1 : elt
  H4 : find k m' = Some x1
  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
  ============================
   ?T0


DEBUG:Going to execute:
let H := open_constr:((H _)) in
           guarded_specialize_term_under_binders_by' guard_tac H tac
Level 0: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 0: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 5: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 8: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 8: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 7: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 6: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 5: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".
Level 4: Backtrace:

In environment
elt : Type
eq_elt : elt -> elt -> Prop
m, 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, x0 : elt
H3 : eq_elt x0 x
H1 : find k m' = Some x
x1 : elt
H4 : find k m' = Some x1
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
The term "H1" has type "find k m' = Some x" while it is expected to have type
 "elt".