On Mon, Sep 7, 2015 at 5:08 AM, Joachim Breitner
Given such a guideline, I would then know what to do with such a ticket, instead of stabbing in the dark. It might mean that we would have to tell a user who observes suboptimal performance in one case that this is unavoidable (we cannot optimize for everyone) and possibly explain how to work around the issue. Or we might find that the discipline could be improved, but then the improvement should be applied to all functions.
I'm all for this. I've messed around with a lot of list-fusion rewrite rules, and though I have a good handle on them now, it took a good deal of trial and error to learn the art of it. In addition to offering a route to learning, another key aspect of these guidelines should be to keep track of which practices are still relevant. Over the years there've been a number of changes in the details of how rules interact with other optimizations, so it'd be good to air out what practices are still relevant (and why) vs which ones arose from legacy issues (and maybe note why they used to but no longer are a concern) -- Live well, ~wren