Throw on trailing colons?

[ben-eb]

Currently we do this, as it turns out it breaks support for Polymer mixins, see: https://github.com/ben-eb/gulp-cssnano/issues/17.

How should we handle these in future? Should we still throw or parse them as a type?

/cc @davidtheclark

[davidtheclark]

parse them as a type

Does that mean --something: would have two type selectors, --something and :? Or that the whole thing would be one type selector?

The weird thing that I'm trying to get about the Polymer syntax is that it's mimicking custom properties -- so it's actually not intended to be a selector, I think, but a custom property -- but it doesn't look like they're applying it to :root. What I'm saying is I'm not sure that should be parsed as a selector.

If Polymer users put they're custom-property-mixin-declarations in :root rules, this would be a non-issue, right?

[ben-eb]

Not parsing these is much more acceptable, I think. I chose to ignore these "selectors" in postcss-minify-selectors so my use case is covered, but I wanted a second opinion. Thanks!