Goal:
  
  G1 : t
  ext : EdgeSet.t
  x : VSet.elt
  v : VSet.elt
  s : VSet.t
  E : VSet.mem v (V G1) = false
  H : VSet.In x s
  ============================
   (x = v)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_empty> flags X1; elim H
Level 3: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".
Level 3: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".
Level 4: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".
Level 4: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".
Level 3: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".
Level 3: Backtrace:

In environment
G1 : t
ext : EdgeSet.t
x, v : VSet.elt
s : VSet.t
E : VSet.mem v (V G1) = false
H : VSet.In x s
Unable to unify "v" with "x".