Haiku is fantastic and seeing it still developed after 20 years is awesome.
But maybe it would benefit from some modern tech. Given the recent discussion on Swift for Ladybird, since huge parts of Haiku are written in C++ it might make sense to gradually introduce Swift to benefit from the language safety features.
Sometimes pre-standard C++ and sometimes C++ 98. There's a lot of "C with classes" and stuff that C++ proponents will insist isn't now "really" C++ because that no longer suits their understanding of the language. As is common for that era it has its own custom string type, BString, and so on.
So Swift is about 20 years over their horizon, and modern Swift is even further.
Apple, Google and Microsoft "modern C++" frameworks also use their own types, instead of the standard library.
See Android NDK, IO Kit / Driver Kit / Metal bindings, C++/WinRT and WIL.
Let alone those that aren't neither WG21 members, nor C++ compiler vendors.