@jsgf I respectfully disagree with you on this. Pretend that you need to solve a particular NP-complete problem instance to really optimize some block of code. You've done something really smart and written a procedural macro that is able to use rayon to parallelize the work, but since you have to search an exponential space, you really can't tell how long it will take. This is best done once, at compile time, on some really powerful dev machine (maybe overnight). The alternative is finding each block of code that needs this optimization, extracting it by hand, running some custom code over that extraction, and then putting it back into the code base. You can extend this idea to run it on something like scoop, which makes the compilation time non-deterministic.