One super rough idea I am thinking about recently is that maybe we don‘t need „Rust“ ABI, but „System ABI“? Today, the interop language of software components is C ABI, and it is wholly inadequate: it doesn’t even have slices, strings are slow and error-prone, etc.
It seems like developing language-independent ABI which significantly improves over C, without being Rust specific, is possible. Slices, tagged unions, utf8 strings, borrowed closures are features which immediately come to mind and have obvious-ish implementations.
Distinction between borrowed and owned (callee must invoke destructor) data and simple lifetimes are somewhat more Rust/C++ specific, but don’t seem too controversial either.
Support for dynamic dispatch (where fat vs thin pointer is a big tradeoff) and templates seems pretty hard, but also desirable and plausible.
It seems like if we had this „C ABI, but you also can have nice things“ , then interoperability between various software components would be easier and far less error prone.