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


DEBUG:Going to execute:
solve [ Ltac.left; t_tauto_intuit | Ltac.right; t_tauto_intuit ]
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := Some z = k \/ None = k
of type
constr of type tacvalue