This is interesting. Would it be helpful, and possible, to add a "YOLO mode" to the Scala compiler so that it just make-believes that recursively derived implicit parameters bottom out properly? Maybe force the caller to give an explicit type (even if the type is wrong). I'd do that to reacquire some semblance of quick compile times.
Then, when the developer has finished they can switch off "YOLO mode" and start playing whack a mole with the types, as needed, punctuated by longer compilation times.
> This is interesting. Would it be helpful, and possible, to add a "YOLO mode" to the Scala compiler so that it just make-believes that recursively derived implicit parameters bottom out properly?
It's not possible to actually build, because at the end of the day you are (presumably) using the implicit for something (e.g. JSON-serializing the value). You could explicitly pass ??? where the implicit is wanted to get a runtime failure where it's used. I guess it might be possible to have tooling do that "magically", but I'm not sure how useful that would be; if you're working on that particular area you can use ??? by hand, if you're not working on that area then you presumably won't be rebuilding it since you're presumably using incremental compilation anyway.
What is possible is to fail-fast when resolution fails, and not check for duplicates when resolution succeeds - one main reason for the blowup is that at every stage of recursive resolution you have to check whether the implicits were ambiguous. There's a proposed fix for that piece: https://github.com/scala/scala/pull/5649
Typescript is kind of like that. You can run the compiler with the type validations disabled. That can lead to potentially broken code but it can also be significantly faster than waiting for all type checks to complete.
The idea is to have fast compilation most of the time (local dev) and slower/full compilation during the "real" build.
Here's a testing analogy: My CI server runs all tests, every time. My local machine only runs the ones I tell it to run as if I change one small piece of an app then I'm not going to wait for the entire test suite to run.
Then, when the developer has finished they can switch off "YOLO mode" and start playing whack a mole with the types, as needed, punctuated by longer compilation times.