undefined is a valid target for comparisons

[zxubian]

Zig Version

0.11.0-dev.892+3db8cffa3

Steps to Reproduce and Observed Behavior

test "undefined should not be used in comparisons" {
    var a: u8 = undefined;
    while (a == undefined) {}
    @panic("unreachable");
}

Actual Behaviour

test compiles and when run reaches the panic.

Expected Behavior

According to the language reference,

undefined means the value could be anything, even something that is nonsense according to the type. Translated into English, undefined means "Not a meaningful value. Using this value would be a bug. The value will be unused, or overwritten before being used."

Thus, the expected behaviour for the above test is to return a compile message along the lines of:

Cannot use `undefined` in a comparison. Consider using an optional type instead.

[squeek502]

Possible duplicate of #597

[zxubian]

Thanks @squeek502 !
After digging a bit more, I think this is a duplicate of #63, and will be considered in #1947 also.

I'll close this issue now.