Goal:
  
  A : Type
  a : A
  l : list (option A)
  l' : list A
  l0 : list A
  Heq : map_option_out l = Some l0
  IHl : forall l' : list A, Some l0 = Some l' -> #|l| = #|l'|
  ============================
   (S #|l0| = #|a :: l0|)


DEBUG:Going to execute:
<coq-core.plugins.ltac::trivial@0> $1 $2

Goals:

DEBUG:Going to execute:
hnf

Goals:

DEBUG:Going to execute:
intros

Goals:

DEBUG:Going to execute:
solve
[ do
![ solve
 [ trivial | apply : eq_sym ; trivial ]
 | discriminate
 | contradiction
 | split ]
| case not_locked_false_eq_true; assumption
| match goal with
  | H:~ _ |- _ => solve [ case H; trivial ]
  end ]