pub fn reserve(&mut self, additional: usize) {
        self.buf.reserve(self.len, additional);
    }
Tries to reserve the minimum capacity for exactly `additional`
elements to be inserted in the given `Vec<T>`. After calling
`try_reserve_exact`, capacity will be greater than or equal to
`self.len() + additional` if it returns `Ok(())`.
Does nothing
benchmarks/haystacks/code/rust-library.rs