Goal:
  
  x : V.t
  y : V.t
  p : VSet.t
  H : x = y -> False
  a : V.t
  H0 : y = a -> False
  H2 : x = a
  ============================
   ((x = a \/ VSet.In a p) /\ y <> a)


DEBUG:Going to execute:
<Coq.Init.Tauto.flatten_contravariant_conj> flags X1 X2 id
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 3: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".
Level 2: Backtrace:

In environment
x, y : V.t
p : VSet.t
H : x = y -> False
a : V.t
H0 : y = a -> False
H2 : x = a
Unable to unify "a" with "y".