However, I'm afraid that the ISO C++ group is not ready for his proposal. We're talking about a committee which has stubbornly and consistently shown that they are willing to sacrifice safety and ergonomics in the name of backward compatibility. The introduction of a borrow checker is a huge change that will get shut down because someone somewhere is unwilling to rewrite their (often broken) code and/or compile their binaries again.
It's no doubt a lot of work but if any of the successors to C++ such as Carbon, Circle, or cpp2 manage to release a solid compiler that is mostly compatible with C++17, I think you'll see a large migration towards it.
Maybe it is becoming less relevant, but language proposals and attendance has grown tremendously since 2010, with no signs of slowing down. The real issue is that it's functionally impossible for a single group to meet the needs of the entire community.
It's no doubt a lot of work but if any of the successors to C++ such as Carbon, Circle, or cpp2 manage to release a solid compiler that is mostly compatible with C++17, I think you'll see a large migration towards it.
Only time will tell, however I would bet against C++ successors. In particular, C++ is fundamentally hostile to cross-language interopt, to the degree that even C++ compilers struggle to maintain compatibility between themselves. For a language to work with C++, its compiler basically needs to contain a C++ compiler as well (as Carbon does). Moreover, simply being "compatible with C++17" is only the very first step to practical usage, e.g. consider how much work the Clang developers put into reverse engineering GCCisms. And that is before considering more exotic language extensions and APIs like OpenMP (and perhaps SYCL at some point as well). All the while C++ continues to change and evolve.
But the part about "numerous groups to create a successor" doesn't really make your case: one of the best ways for things to get into any standard is to have multiple efforts that can be used as experience and starting points for the evolution of a standard. This has already happened a lot in the history of C++
Buy the compiler, get somebody who could build you a nuclear reactor, drug discovery simulator and a GPU architecture. Deal of the century.
FWIW, with Hylo you would rely on value semantics, you would not need Rust-style full-blown borrow checks with viral annotations, which is what he has been implementing and you would get rid of any kind of view types for parameter passing. You would just pass values.
I really think that is the path forward to bet on.
For whoever thinks Hylo is too new or experimental, it is not the language itself what is important but what C++ can learn from it. Hylo is based in experience implementing Swift by Dave Abrahams, Generic programming from Alex Stepanov and value semantics and structural polymorphism and value semantics and related work from Sean Parent.
So even if the implementation itself is not so advanced, it is just a natural evolution of all things I just named here which have a track record of like 30 years at least in total with a lot of generic code and value semantics lessons and runtime polynorphism lessons learned.
Too much infrastructure code and industry standards, that will be kept being done in C++ for decades to come, and need a way for improving the whole security story.
