Why not? WASM with optimisations will mostly run faster than binaries without optimisations, which is the current strategy. Plus you won't need the compile ste

Why not? WASM with optimisations will mostly run faster than binaries without optimisations, which is the current strategy. Plus you won't need the compile step that's necessary at the moment. Distributing arbitrary binaries right now is bad because it's not clear what those binaries contain, but the WASM environment is completely sandboxed, so it wouldn't be possible for them to read files they weren't meant to or phone home with telemetry. The Cargo project already does some amount of automatic building e.g. of docs pages - this could be extended to proc macro crates to ensure that the uploaded binaries must be built from the uploaded source files. Alternatively, making sure that reproducible binaries are standard would help a lot from a trust perspective. This isn't suitable for every situation, but as a tool to reduce the compile times of some of the bigger and slower macro crates, it sounds like a great option to have.