Inconsistency between division operator vs assignment (debug only)

[adriandelgado]

Zig Version

0.11.0-dev.1863+a63134a4a

Steps to Reproduce and Observed Behavior

Run this code on debug mode.

const print = @import("std").debug.print;

pub fn main() void {
    const original: u256 = 99999999999999999999000000000000000000000;
    const divisor: u256 = 10000000000000000000000000000000000000000;
    print("Division operation: {}  (correct)\n", .{original / divisor});

    var num = original;
    num /= divisor;

    print("Division asignment: {}\n", .{num});
}

It outputs:

Division operation: 9  (correct)
Division asignment: 10

Expected Behavior

I expected both operations to behave the same way just like in any release mode.

[adriandelgado]

After some trial and error I minimized the constant values as much as possible.

const original: u129 = 99999999999999999997315645440;
const divisor: u129 = 10000000000000000000000000000;

It's bugged with any value greater than the "original". However, using u128 or smaller gets rid of the bug.