Goal:
  
  A : Type
  p : A → bool
  x : A
  l : list A
  H : is_true (p x)
  H0 : Forall (λ x : A, p x) l
  IHForall : is_true (forallb p l)
  ============================
   (p x && forallb p l = true)


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

In environment
A : Type
p : A → bool
x : A
l : list A
H : p x
H0 : Forall (λ x : A, p x) l
IHForall : forallb p l
Unable to unify "true" with "p x && forallb p l".
Level 0: Backtrace:

In environment
A : Type
p : A → bool
x : A
l : list A
H : p x
H0 : Forall (λ x : A, p x) l
IHForall : forallb p l
Unable to unify "true" with "p x && forallb p l".
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.