I’m afraid that :last-child and :last-of-type won’t be supported without a complete refactoring of the CSS runtime.

Support requires either an additional parsing pass of entire HTML document, or non-trivial look-ahead parsing logic (in extreme cases, it takes even more time/resources than a second parsing pass).

All our attempts to implement this feature resulted in significant performance degradation even in simple cases where this feature was not used. We have decided to temporarily omit the feature