> The resulting constraint is roughly similar to that of never ever breaking ABI in C++.
No, not even remotely. ABI-stability in C++ means that C++ is stuck with suboptimal implementations of stdlib functions, whereas Rust only stabilizes the exposed interface without stabilizing implementation details.
> Unfortunately editions don't allow breaking changes in the standard library
Surprisingly, this isn't true in practice either. The only thing that Rust needs to guarantee here is that once a specific symbol is exported from the stdlib, that symbol needs to be exported forever. But this still gives an immense amount of flexibility. For example, a new edition could "remove" a deprecated function by completely disallowing any use of a given symbol, while still allowing code on an older edition to access that symbol. Likewise, it's possible to "swap out" a deprecated item for a new item by atomically moving the deprecated item to a new namespace and making the existing item an alias to that new location, then in the new edition you can change the alias to point to the new item instead while leaving the old item accessible (people are exploring this possibility for making non-poisoning mutexes the default in the next edition).
Only because Rust is a source only language for distribution.
One business domain that Rust currently doesn't have an answer for, is selling commercial SDKs with binary libraries, which is exactly the kind of customers that get pissed off when C and C++ compilers break ABIs.
Microsoft mentions this in the adoption issues they are having with Rust, see talks from Victor Ciura, and while they can work around this with DLLs and COM/WinRT, it isn't optimal, after all Rust's safety gets reduced to the OS ABI for DLLs and COM.
Rust allows binary libraries with a C ABI. Having safety within any given module is still a big deal, and it's hard to guarantee safety across dynamic modules when the code that's actually loaded can be overridden by a separately-built version.
I'm not expecting to convince you of this position, but I find it to be a feature, not a bug, that Rust is inherently hostile to companies whose business models rely on tossing closed-source proprietary blobs over the wall. I'm fairly certain that Andrew Kelley would say the same thing about Zig. Give me the source or GTFO.
In the end it is a matter of which industries the Rust community sees as relevant to gain adoption, and which ones the community is happy that Rust will never take off.
Do you know one industry that likes very much tossing closed-source proprietary blobs over the wall?
Game studios, and everyone that works in the games industry providing tooling for AAA studios.
> Game studios, and everyone that works in the games industry providing tooling for AAA studios.
You know what else is common in the games industry? C# and NDA's.
C# means that game development is no longer a C/C++ monoculture, and if someone can make their engine or middleware usable with C# through an API shim, Native AOT, or some other integration, there are similar paths forward for using Rust, Zig, or whatever else.
NDA's means that making source available isn't as much of a concern. Quite a bit of the modern game development stack is actually source-available, especially when you're talking about game engines.
Do you know what C# has and Rust doesn't? A binary distribution package for libraries with a defined ABI.
> I'm fairly certain that Andrew Kelley would say the same thing about Zig. Give me the source or GTFO.
Thus it will never be even considered outside the tech bubble.