Beginner-rust solution to Advent of Code 2020 Day 01 - Feedback very welcome!

aoc2020_01_rust.rs

// Uses the cargo-aoc crate to help take care of inputs and benchmarks
use aoc_runner_derive::{aoc, aoc_generator};
use std::num::ParseIntError;

#[aoc_generator(day1)]
fn parse_input_day1(input: &str) -> Result<Vec<i32>, ParseIntError> {
    input.lines().map(|l| l.parse()).collect()
}

#[aoc(day1, part1)]
fn part1(numbers: &[i32]) -> i32 {
    let mut numbers = numbers.to_vec();
    numbers.sort();
    let mut sum;
    
    let mut iter = numbers.iter();
    let mut low = iter.next();
    let mut high = iter.next_back();

    let result = loop {
        let lowval = low.unwrap();
        let highval = high.unwrap();

        sum = lowval + highval;
        if sum > 2020 {
            high = iter.next_back();
        }
        else if sum < 2020 {
            low = iter.next();
        }
        else {
            break lowval * highval;
        }
    };
    return result
}