Goal:
  
  x : V.t
  y : V.t
  p : VSet.t
  H : x = y -> False
  a : V.t
  H0 : y = a -> False
  ============================
   ((x = a \/ VSet.In a p /\ y <> a -> (x = a \/ VSet.In a p) /\ y <> a) /\
    ((x = a \/ VSet.In a p) /\ y <> a -> x = a \/ VSet.In a p /\ y <> a))


DEBUG:Going to execute:
<Coq.Init.Tauto.is_unit_or_eq> flags X1; Ltac.cut X2;
            [ intro; clear id
            | Ltac.cut X1; [ exact id | constructor 1; fail ] ]
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
Unable to unify "y" with "x".