Summing a file of integers in Rust and Zig

sum-file.rs

use std::fs::File;
use std::io::prelude::*;

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;

    let mut sum: u64 = 0;
    for line in contents.lines() {
        match line.parse::<u64>() {
            Ok(val) => sum += val,
            Err(_) => println!("\"{}\" was not a number", line),
        };
    }
    println!("{}", sum);

    Ok(())
}

sum-file.zig

const std = @import("std");
const ArrayList = std.ArrayList;
const test_allocator = std.testing.allocator;

pub fn main() anyerror!void {
    const file = try std.fs.cwd().openFile("numbers.txt", .{ .read = true });
    const contents = try file.reader().readAllAlloc(
        test_allocator,
        10000,
    );
    var lines = ArrayList(ArrayList(u8)).init(test_allocator);
    var lineIndex: u8 = 0;
    var currentLine = ArrayList(u8).init(test_allocator);
    for (contents) |c| {
        if (c == '\n') {
            try lines.append(currentLine);
            currentLine = ArrayList(u8).init(test_allocator);
        } else {
            try currentLine.append(c);
        }
    }
    var sum: u64 = 0;
    for (lines.items) |line| {
        if (std.fmt.parseInt(u64, line.items, 10)) |value| {
            sum += value;
        } else |err| {
            std.log.warn("Unable to parse {s}", .{line.items});
        }
    }
    std.log.info("{d}", .{sum});
}