I appreciate the usecase you're describing but I feel like "that has good runtime performance (LLVM is great here)" is at odds with the rest of that list. I don't see that as a problem though. I think it's useful to have a very fast lightweight compiler for development and prototyping (both of projects and the compiler itself) and a slower one for highly optimized production releases.
replyYes, that's one answer. But I actually think you can absolutely have both in the same compiler. But you need to have two backends, as I described. You use the custom backend for development (fast to compile) and you use LLVM for release (fast to run).
replyWell yes, but at that point aren't you effectively writing two compilers in one? It seems to me that would be at odds with wanting it to be fast to compile itself (you said under 30s) and would make it more difficult for the uninitiated to contribute to.
replyI don't mean to discourage and I don't disagree with the aims. I just have the (possibly mistaken) impression that compilers inevitably fall on a continuum from simple and fast to complex and slow.