Goal:
  
  _z_ : VSet.t
  x0 : V.t
  x1 : V.t
  x2 : V.t
  x3 : V.t
  a : V.t
  H : VSet.In a _z_
  ============================
   (x1 = a)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_empty> flags X1; elim H
Level 5: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".
Level 5: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".
Level 6: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".
Level 6: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".
Level 5: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".
Level 5: Backtrace:

In environment
_z_ : VSet.t
x0, x1, x2, x3, a : V.t
H : VSet.In a _z_
Unable to unify "a" with "x1".