Goal:
  
  A : Type
  p : A → bool
  n : nat
  x : A
  Hnth : nth_error [] n = Some x
  HPl : is_true (forallb p [])
  ============================
   (p x = true)


DEBUG:Going to execute:
case not_locked_false_eq_true; Ltac.assumption
Level 1: Backtrace:

In environment
A : Type
p : A → bool
n : nat
x : A
Hnth : nth_error [] n = Some x
HPl : forallb p []
Unable to unify "true" with "p x".
Level 0: Backtrace:

In environment
A : Type
p : A → bool
n : nat
x : A
Hnth : nth_error [] n = Some x
HPl : forallb p []
Unable to unify "true" with "p x".
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.