Goal:
    z : Z  k : t  H : Some z = k
  ============================
   (None = k)


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

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".
Level 3: Backtrace:

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".
Level 4: Backtrace:

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".
Level 4: Backtrace:

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".
Level 3: Backtrace:

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".
Level 3: Backtrace:

In environment
z : Z
k : t
H : Some z = k
Unable to unify "k" with "None".