Yeah, slow compile loops are the worst part of Rust for me. (The 2nd-worst part is fighting the borrow checker)

I know it'll get faster as hardware marches on, but I often wish I could draw a boundary and say, "Look compiler, this program is months from being done. Let's say everything outside this boundary can be optimized and it won't change. But everything inside the boundary is quick-changing business logic that I'm actively debugging. Don't link or optimize across that boundary. Use wasm to enforce that if you need it."

In C++ I did that with Lua for a while, but the DevEx cost of FFI boundaries is pretty awful even when the performance cost is affordable. I dunno.