exact mapM.map_cons_succ f a x 0 b #[]
case h
α : Type u
m : Type v → Type w
inst✝¹ : Monad m
β : Type v
inst✝ : LawfulMonad m
f : α → m β
a : α
x : Array α
b : β
⊢ mapM.map f (cons a x) (0 + 1) (push (mkEmpty (Nat.succ (size x))) b) = do
    let y ← mapM.map f x 0 (mkEmpty (size x))
    pure (cons b y)
no goals