I’d love static analysis that finds which functions may panic, which are guaranteed not to. On a related note, it’d be nice to be able to hoist panics out of loops and coalesce multiple consecutive assertions into one (llvm can’t do it, because partially done work is a side effect).
I maintain a long-term Rust + Node.js project, and the Node side is the painful one.
Node makes backwards-incompatible changes, and doesn’t have anything like the editions to keep old packages working. I can end up with some dependencies working only up to Node vX, and some other deps needing at least Node v(X+1).