Goal:
  
  A : Type
  B : Type
  p : A → B → bool
  a : A
  l : list A
  b : B
  l' : list B
  q : list A
  q' : list B
  IHl : ∀ l' : list B,
          forallb2 p l l' && forallb2 p q q' → forallb2 p (l ++ q) (l' ++ q')
  pa : is_true (p a b)
  pl : is_true (forallb2 p l l')
  pq : is_true (forallb2 p q q')
  ============================
   (forallb2 p l l' && forallb2 p q q' = true)


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

In environment
A : Type
B : Type
p : A → B → bool
a : A
l : list A
b : B
l' : list B
q : list A
q' : list B
IHl : ∀ l' : list B,
        forallb2 p l l' && forallb2 p q q' → forallb2 p (l ++ q) (l' ++ q')
pa : p a b
pl : forallb2 p l l'
pq : forallb2 p q q'
Unable to unify "true" with "forallb2 p l l' && forallb2 p q q'".
Level 0: Backtrace:

In environment
A : Type
B : Type
p : A → B → bool
a : A
l : list A
b : B
l' : list B
q : list A
q' : list B
IHl : ∀ l' : list B,
        forallb2 p l l' && forallb2 p q q' → forallb2 p (l ++ q) (l' ++ q')
pa : p a b
pl : forallb2 p l l'
pq : forallb2 p q q'
Unable to unify "true" with "forallb2 p l l' && forallb2 p q q'".
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.