_is-undefined() not working

[K3TH3R]

I'm not sure if this is something that broke in a recent version of SASS, or I'm just using it wrong, but I have been running into a problem using _is-undefined(). There wasn't an example in the docs, so I was trying multiple options, but it just doesn't seem to be working properly either way:

// $zcfg doesn't exist yet
@warn 'is $zcfg undefined? ' _is-undefined(zcfg); // false, should be true?
@warn 'is $zcfg undefined? ' _is-undefined('zcfg'); // false, should be true?
@warn 'is $zcfg undefined? ' _is-undefined('$zcfg'); // false, should be true?
@warn 'is $zcfg undefined? ' _is-undefined($zcfg); // SASS exits with: Error: Undefined variable: "$zcfg".
@warn '$zcfg exists: ' variable-exists(zcfg); // false

$zcfg: 'test';
@warn 'is $zcfg undefined? ' _is-undefined(zcfg); // false
@warn 'is $zcfg undefined? ' _is-undefined('zcfg'); // false
@warn 'is $zcfg undefined? ' _is-undefined('$zcfg'); // false
@warn '$zcfg exists: ' variable-exists(zcfg); // true

This is using [email protected] -> [email protected] -> [email protected]

[davidkpiano]

This is the only one that should "return" true:

@warn 'is $zcfg undefined? ' _is-undefined($zcfg); // SASS exits with: Error: Undefined variable: "$zcfg".

since the others are values, and therefore defined.

[K3TH3R]

That's what my initial expectation was, but the SASS compiler refuses to let me use that syntax.

[davidkpiano]

I would default to using variable-exists.