pub trait RenameExt {
type Kind;
// Required methods
fn try_db(&self, rn: &RenameMap) -> Option<DbIdent<Self::Kind>>;
fn set_db(&self, rn: &mut RenameMap, name: DbIdent<Self::Kind>);
fn db_assigned(&self, rn: &RenameMap) -> bool;
// Provided method
fn db(&self, rn: &RenameMap) -> DbIdent<Self::Kind> { ... }
}