[Arnavion]

You keep saying this but I suggest you actually look at the code. The precompiled binary is not a sandboxed WASM binary. Despite the name "watt" it has nothing to do with https://github.com/dtolnay/watt . `watt::bytecode` refers to the serialization protocol used by the proc macro shim and the precompiled binary to transfer the token stream over stdio, not anything related to WASM.

Also it's worth noting that even if it was a sandboxed binary ala https://github.com/dtolnay/watt , it's not obvious that distributions or users would be satisfied with that. For example Zig had this discussion with the own WASM blob compiler that they use as part of bootstrapping. https://news.ycombinator.com/item?id=33915321 . As I suggested there, distributions might be okay with building their own golden blobs that they maintain themselves instead of using upstream's, and that could even work in this Rust case for distributions that only care about a single copy of serde for compiling everything. But it's hard for the average user doing `cargo build` for their own projects with cargo registry in `~/.cargo` to do the same replacement.

[amluto]

A really nice (IMO) solution would be to build a wasm blob reproducibly and to ship the blob’s hash, along with a way to download the blob, as part of a release. Then distros could build the blob, confirm that the hash matches, and ship a package that is built from source and nonetheless bit-for-bit identical to the upstream binary.

[mmastrac]

You're right. I misread that code and edited the parent post.