Robin Malfait 924dd69bdb
Ensure @custom-variant foo () has a non-empty selector list (#16009)
This PR fixes an issue where an empty selector list was valid when
defining a `@custom-variant`.

Given this input:
```css
@custom-variant foo ();
```

If you then use it with a utility such as `foo:flex`, then the following
(incorrect) CSS was generated:

```css
.foo\:flex {
   {
    display: flex;
  }
}
```

Which is invalid CSS. This PR will now validate that that we have at
least _something_ and show an error accordingly.
2025-01-29 16:09:09 +01:00
..
2024-12-11 15:27:20 +01:00