Goal:
    A : Type  P : nat → A → Type  n : nat  Γ : list A
  ============================
   (All_fold (λ (Γ : list A) (d : A), P (n + #|Γ|) d) Γ
    → All_fold (λ (Γ : list A) (d : A), P (n + #|Γ|) d) Γ)


DEBUG:Going to execute:
(solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"