Goal:
  
  T : Type -> Type
  M : Monad T
  A : Type
  P : nat -> A -> Type
  Q : A -> Type
  f : forall (n : nat) (x : A), ∥ Q x ∥ -> T (∥ P n x ∥)
  n : nat
  a : A
  l : list A
  X : P n a
  allq1 : list A
  allq : All Q allq1
  ============================
   (a :: l = allq1 ->
    let H := CoreTactics.block in let H0 := CoreTactics.block in All Q l)


DEBUG:Going to execute:
fun p => first
             [ match p with
               | _ => generalize dependent p; intros p
               end
             | intros
             until
             p
             | intros
             until
             1
             | intros ]