Checked the ASM output for these three options: pub enum Operation { /// Move cursor by n characters. Retain(usize), /// Delete n characters. Delete(usize), /// Insert text at position. Insert(String), } pub struct A { changes: Vec<Operation>, len: usize, } impl A { pub fn is_empty1(&self) -> bool { match self.changes.as_slice() { [] => true, [Operation::Retain(_)] => true, _ => false, } } /// `true` when the set is empty. pub fn is_empty2(&self) -> bool { let len = self.changes.len(); len == 0 || ( len == 1 && self.changes[0] == Operation::Retain(self.len) ) } pub fn is_empty3(&self) -> bool { match self.changes.as_slice() { [] | [Operation::Retain(_)] => true, _ => false } } }