∀ {α : Type u} {r : Std.Rii α} [inst : LT α] [inst_1 : Std.PRange.Least? α] [inst_2 : Std.PRange.UpwardEnumerable α]
  [Std.PRange.LawfulUpwardEnumerableLT α] [inst : Std.PRange.LawfulUpwardEnumerableLeast? α]
  [inst_3 : Std.Rxi.IsAlwaysFinite α] [inst_4 : Std.PRange.LawfulUpwardEnumerable α] {γ : Type u} {init : γ}
  {m : Type u → Type w} [inst_5 : Monad m] [LawfulMonad m] {f : (a : α) → a ∈ r.toArray → γ → m (ForInStep γ)},
  forIn' r.toArray init f = forIn' r init fun a x acc => f a ⋯ acc