Goal:
    G : t  H : is_true false
  ============================
   (exists z : Z, None = Some z /\ z <= 0)


DEBUG:Going to execute:
Ltac.assumption
Level 3: evaluation returns
<coq-core.plugins.tauto::is_empty@0>
where
tauto_flags := 
of type
tauto_flags
X1 := is_true false
of type
constr of type tacvalue

Level 3: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.