This reads like an AI response to me. Would you elaborate? I can see no reason to believe it would achieve stability based on many of the statements in this issue.

It looked to me like it was just due to recurring build issues. Lots of "swift can't import these conflicting C++ versioned libraries concurrently" and "can't use some operator due to versioning or build conflicts". Basically it sounds like trying to add swift to the project was breaking too many things, and they decided it wasn't worth it.

It's a shame, I think swift is an underappreciated language, however I understand their reasoning. I think if they tried to just use swift from the beginning it would have been too ambitious, and trying to add swift to a fragile, massive project was probably too complex.

Well, it was a terrible idea in any case unless it was for high-level-ish code only. Swift generally can't compete with C++ in raw performance (in the same way as Java - yeah, there are benchmarks where it's faster, but it basically doesn't happen in real programs).

> It's a battle tested choice and pretty much every browser actually in use is written in C++.

Pretty much every browser actually in use is stuck with C++ because they're in way too deep at this point, but Chromium and Firefox are both chipping away at their C++ piece by piece and replacing it with safer alternatives where they feasibly can. Chromium even blocked JPEG-XL adoption until there was a safe implementation because they saw the reference C++ decoder as such a colossal liability.

IMO the takeaway is that although those browsers do use a ton of C++ and probably always will, their hard-won lessons have led them to wish they didn't, and to write a brand new browser in C++ is just asking to needlessly repeat all of the same mistakes. Chromium uses C++ because Webkit used C++ because KHTML used C++ in 1998. You have the benefit of hindsight.

> a subset of C++ written with contemporary memory safety practices

What is this mythical subset of C++? Does it include use of contemporary STL features like string_view? (Don’t get me wrong — modern STL is considerably improved, but it’s not even close to being memory-safe.)

    class FontFeatureValuesMapIterationSource final
    : public PairSyncIterable<CSSFontFeatureValuesMap>::IterationSource {
    public:
    FontFeatureValuesMapIterationSource(const CSSFontFeatureValuesMap& map,
                                      const FontFeatureAliases* aliases)
      : map_(map), aliases_(aliases), iterator_(aliases->begin()) {}

Wasn't Rust developed specifically for Mozilla? Isn't mozilla written in Rust?

Swift never felt truly open source either. That people can propose evolution points doesn’t change the fact that Apple still holds all the keys and pushes whatever priorities they need, even if they’re not a good idea (e.g. Concurrency, Swift Testing etc)

Also funny enough, all cross platform work is with small work groups, some even looking for funding … anyway.