Goal:
  
  A : Type
  P : list A → A → Type
  Q : list A → list A → A → A → Type
  hlen : #|[]| = #|[]|
  H : ∀ (Δ Δ' : list A) (x y : A),
        All_fold P Δ
        → All_fold P Δ' → All2_fold Q Δ Δ' → P Δ x → P Δ' y → Q Δ Δ' x y
  ============================
   (locked false = true)


DEBUG:Going to execute:
Ltac.assumption
DEBUG LTAC Evaluated term: not_locked_false_eq_true