[FEATURE] Parse simple expressions

[JakeQZ]

Part of #389

[coveralls]

coverage: 69.267% (+0.08%) from 69.191%
when pulling bf16950 on feature/css-expressions
into 3500d42 on main.

[JakeQZ]

I can't find any specification reference that indicates this should be allowed or possible, though I'm sure I've seen it before.

Unless anyone can find it, I suggest this PR be closed as invalid.

[oliverklee]

I can't find any specification reference that indicates this should be allowed or possible, though I'm sure I've seen it before.

Unless anyone can find it, I suggest this PR be closed as invalid.

I also can only find the calc() syntax.

I agree that we should close this as invalid.

Closing it now.

[JakeQZ]

I also can only find the calc() syntax.

I just put the test CSS into Firefox. If it's fixed so that the values are well formed (with a length and a unit), the expressions do work inside the max function, but not as standalones.

So there is something to support - expressions within CSS function values. I don't know if all functions support expressions - or just specific length calculation functions like max...

[JakeQZ]

So there is something to support - expressions within CSS function values. I don't know if all functions support expressions - or just specific length calculation functions like max...

#1438 captures this.