Goal:
    T : Type -> Type
  ============================
   (Monad T ->
    forall (A : Type) (P : nat -> A -> Type) (Q : A -> Type),
    (forall (n : nat) (x : A), ∥ Q x ∥ -> T (∥ P n x ∥)) ->
    nat -> forall (a : A) (l : list A), ∥ All Q (a :: l) ∥ -> ∥ Q a ∥)


DEBUG:Going to execute:
let ty := type of B in
           intro || (let H := fresh in
                     intro
                     H)
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.