Re: [selectors] Previous-sibling combinator?

On Thu, Feb 12, 2015 at 9:52 AM, Benjamin Poulain <benjamin@webkit.org> wrote:
> On 2/11/15 2:47 PM, Tab Atkins Jr. wrote:
>> The problem with "giving people enough rope to hang themselves" is
>> when the mere existence of the feature slows down or complexifies the
>> engine as a whole, regardless of whether it's used.
>
> Can you explain this? Why is that the case?

Because being able to handle style invalidations from arbitrarily high
up in the tree prevents simplifications that assume that can't happen;
at minimum, it probably adds branches in the code which can have
measurable perf effects.

~TJ