∀ {α : Type u} {β : α → Type v} (k : α) (v : β k) (l : Std.DTreeMap.Internal.Impl α β) (hl : l.Balanced)
  (hr_2 : Std.DTreeMap.Internal.Impl.leaf.Balanced)
  (hlr_2 : Std.DTreeMap.Internal.Impl.BalancedAtRoot l.size Std.DTreeMap.Internal.Impl.leaf.size),
  Std.DTreeMap.Internal.Impl.maxView k v l Std.DTreeMap.Internal.Impl.leaf hl hr_2 hlr_2 =
    { k := k, v := v, tree := { impl := l, balanced_impl := hl, size_impl := ⋯ } }