trait SizeHint {
// Required methods
fn lower_bound(&self) -> usize;
fn upper_bound(&self) -> Option<usize>;
// Provided method
fn size_hint(&self) -> (usize, Option<usize>) { ... }
}
trait SizeHint {
// Required methods
fn lower_bound(&self) -> usize;
fn upper_bound(&self) -> Option<usize>;
// Provided method
fn size_hint(&self) -> (usize, Option<usize>) { ... }
}