It'd be great to include some information about the awesome cross-compilation support!

Thanks for all of your work, it's great.

There's many things you do that I like, but Rust's bad choices about allocation are also almost all library not language mistakes.

You only get one chance to omit something from the standard library. After that, you're stuck with it forever.

Rust has “Editions”, which are points where they can make breaking changes as programs and crates (libraries) have to opt-in to the new edition, and you can mix crates from different editions. So if they need to make backwards-incompatible changes in order to add allocator support, they can do this in an edition.

While I am on the Rust side on this, I am not sold out on mixing crates with different editions, because I believe it won't work at scale in typical enterprise contexts.

Meaning, having binary crates compiled with different epochs, and then passing data and closures across crate public functions, specially using as input data from modern ones into the older ones.

With the language evolution it won't be possible to keep semantic changes to work as expected, or if the runtime requirements have changed, that linking everything together will still work as expected.

To me epochs seem to only work when using a single compiler, compiling all crates from scratch, with is nice, but not what enterprise C, C++, Java, .NET code looks like, and any new language being adopted is expected to play the same game.

Hence why Apple took such a big effort to make Swift ABI being able to deal with language updates.

Editions only support syntactic changes, so what you are afraid of cannot happen.

We mix editions in >1000 crate projects every day just fine, and we are sure it will work with all future editions.

Which just reinforces my opinion about them.

How are the editions going to help when semantic changes do eventually come up in future Rust versions?

If future Rust versions do make semantic changes to existing language constructs, that will presumably only apply to crates built with the new edition, and crates built with the old will get the old semantics.

If we’re talking ABI-level stuff, that doesn’t require an edition because you build all your crates with the same compiler, so it can use a consistent ABI.

Swift’s ABI stability has nothing to do with semantic changes and everything to do with they wanted binary compatibility, so they could start using Swift in the system frameworks that your app links against.

Yes we are talking about ABI level stuff.

Rust will never be an option in certain scenarios if the only option is to be like a scripting language and require its users to compile everything from source code.

Swift's ABI also takes into account ways to secure the ABI while evolving the language.

Rust will never do semantic changes.

That’s a feature.

If you want languages that introduce semantic changes and break your code, you have many options to pick from, C++ being one such language in the same space as Rust.

To the language, but not to the standard library. The standard library is eternal.

One can still deprecate things