Re: Consideration for Rust contributions in Emacs

[Daniel Martín]

Troy Hinckley <comms@dabrev.com> writes:

> I've had a discussion with several people recently about future
> possibilities of Rust in GNU Emacs core. I could not find an answer to
> this on the archives, so if it has been resolved previously please
> point me to that thread.
>
> Let assume for the sake of this discussion that there was a some Rust
> code that someone wanted to contribute and the maintainers wanted the
> functionality it provided. What would be the consideration/objections?
> Here are few that we came up with:
>
> 1. The Rust tool-chain is Apache licensed and so is LLVM. There is work on a 
> GCC backend, but it is not production ready yet. Would Emacs allow the 
> current Rust tool-chain?
> 2. LLVM (and hence Rust) support fewer targets than GCC. Are there certain 
> target that LLVM doesn’t support that are important to Emacs?
> 3. Many Rust libraries (crates) are MIT and/or Apache licensed. Do all 
> Libraries used by GNU Emacs need to be GPL or is it sufficient to have a GPL 
> compatible license?
> 4. How sizable of a contribution would be needed for the maintainers
> to accept Rust in Emacs core? Would auxiliary functionality be
> considered (such as Rust in the Linux Kernel) or would it need to have
> major impact.
> 5. Concerns over having more than one core language in GNU Emacs.
> 6. Concerns over using such a new language. Rust still changes at a fast pace 
> relative to C and it’s future is less certain then a more established 
> language.
> 7. Concerns over support for Rust being a distraction from other development 
> work.
> 8. I assume that FSF copyright would still be a requirement. I just bring it 
> up so no one else has to.
>

The first question to ask is if and how Rust would make the Emacs
codebase better.  Do you have any concrete examples of that?  I don't
think that the alleged benefits of Rust, even when used in small parts
of new functionality, would outweigh the costs of concerns 5, 6, and 7,
at least.

This answer is not exclusive to Rust.  I don't see any clear net benefit
from using another language along with C (even C++) in Emacs core.