False Positive on Custom Property Fallbacks

[yuschick]

Describe the bug
The current implementation of the custom property fallbacks check is to search for a comma in the same declaration value as a var. However, this fails to report for some shorthand properties or verbose style values.

To Reproduce
The following style should be flagged as an error, but it passes.

grid-template: var(--page-header-size) 1fr / max-content minmax(0, 1fr) max-content;

This style is passing the check because of the comma in the minmax function.

Expected behavior
The page-heasder-size custom property should be flagged.

Screenshots

[yuschick]

Can use the following regexp to find any var declarations to then search for a fallback value.

/var\(.+?\)/g