Goal:
  
  T : Type -> Type
  M : Monad T
  A : Type
  P : A -> Type
  Q : A -> Type
  f : forall x : A, ∥ Q x ∥ -> T (∥ P x ∥)
  l0 : list A
  a : A
  l : list A
  X : P a
  q : Q a
  allq : All Q l
  ============================
   (All Q l)


DEBUG:Going to execute:
let rec do_ccl :=
            try do_atom; repeat (do_intro; try do_atom);
             try MCPrelude.arith_congr; (solve [ split; do_ccl ])
           in
           (solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"