pub trait HasSpan {
// Required method
fn span(&self) -> Span;
// Provided methods
fn start_position(&self) -> Position { ... }
fn end_position(&self) -> Position { ... }
}pub trait HasSpan {
// Required method
fn span(&self) -> Span;
// Provided methods
fn start_position(&self) -> Position { ... }
fn end_position(&self) -> Position { ... }
}