[zozbot234]

Safe C++ could still be a genuine improvement on Rust - if only because the community would be larger by at least one order of magnitude compared to present-day Rust. Though you would also need a viable C++ epochs proposal to keep the complexity from becoming totally unmanageable.

[pcwalton]

I'm not convinced, actually. The problem is that every proposal for safe C++ that I've seen sacrifices compatibility with the broader C++ ecosystem. Yes, you could graft borrow checking onto a C++-like semantics, but what you would end up creating is an incompatible dialect of C++--essentially a new language. So the resulting ecosystem would actually be smaller than that of Rust.

[zozbot234]

I think this issue is a bit overstated. What people want is not to have interop with existing C++ code, but to just keep writing C++ in the same idiomatic style. And this just isn't feasible if you want to automatically ensure memory safety. It's especially problematic in larger codebases that can't be comprehensively surveyed, which is what people mostly want to use C++ for. So, something has to give.

Rust is a bit of a different story, because the clunkiness of Pin<> actually makes interop with C++ (and, to a lesser extent, C) surprisingly difficult in a way that might be amenable to improvement.