Potentially improved pseudo filter perf

[bkardell]

Simple matchers are simple - known complexity. Filters are potentially substantially more complex. It makes sense to avoid calling them when possible. There are cases where filters are included as part of a compound selector[1] in which the simple selectors are leading. In this case it is functionally equivalent, but potentially much faster to test the filter only if the other simple selectors don't match. I explained this more on the forum[2], but, that's the gist and I don't know that anyone is actively watching this. I implemented and tested this in my fork[3] and it seems good, but I don't want to send a pull or think about taking it further without some feedback.

[1] http://dev.w3.org/csswg/selectors4/#compound
[2] http://forum.jquery.com/topic/matchers-and-pseudos
[3] https://github.com/bkardell/sizzle/blob/master/src/sizzle.js#L1749

[gibson042]

Thanks very much for the feedback! We actually already have something similar in the works for Sizzle 2.0 (see https://github.com/jquery/sizzle/blob/2.0-WIP/src/sizzle.js#L1568 and https://github.com/jquery/sizzle/blob/2.0-WIP/src/sizzle.js#L43-L46), and would welcome your contributions to that branch.