Rustaceans at the border

Rustaceans at the border

An important point here is that while Rust 2021 code will not compile with a Rust 2015-only compiler, a future Rust compiler is expected to be able to compile all past editions, and to support interface-level interoperability between the editions at the crate level. Note that the crate is the unit of compilation in Rust, just as the translation unit is the unit of compilation in C.

So, within a crate, I must stick to one edition; but within a project such as the kernel, I can freely mix editions (because I'd expect the kernel to be made of several crates, not to be one giant crate - just as in C I'd expect the kernel to be in multiple files spread around several directories, and not in a single giant source file). The only limitation I have is that I cannot use recent editions without a bump to the MSRV; but the same applies to C, where I can't use the full language without allowing for the bugs in older versions of GCC.