Serde_derive v1.0.172+ uses a precompiled binary has since v1.0.172, July 10, shipped a pre-compiled binary for Linux x64, which it uses to reduce compile times for users of this crate.

As this was a patch release, it has mostly gone under the radar. was raised July 28 and closed August 17 as effectively wontfix, and the issue is now locked.

There are two PRs to make this feature optional:

This is filed under announcements as in the current state, some users in regulated industries (Automotive, Medicine, etc) will need to do additional work to document this precompiled binary as a separate dependency that is being injected into the Rust compilation phase.


FYI: v1.0.184 doesn't contain the precompiled binary any more and the release note

matklad raised the [target.'cfg(any())'.dependencies] hack to solve parallelism problem of building proc macro crates in GitHub - matklad/macro-dep-test , and dtolnay is watching it.

Update: found Pre-RFC: Sandboxed, deterministic, reproducible, efficient Wasm compilation of proc macros - language design - Rust Internals proposed by dtolnay a few hours ago.