alt Hacker NewsIt's a social problem that's created by a technical problem.
In many languages, if you want to integrate package A with package B, you can make and share a package AB, which people can reuse. That scales, and facilitates reuse, and avoids either package having to support everything.
In Rust, if the integration involves traits, integration between package A and package B must happen either in A or in B. That creates a scaling problem, and a social problem.
Other than duck-typed languages (and I count Go as basically that), which languages actually provide this feature?
AFAIK, it’s not really very common to be able to extend foreign types with new interfaces, especially not if you own neither.
C++ can technically do it using partial specialization, but it’s not exactly nice, and results in UB via ODR violation when it goes wrong (say you have two implementations of a `std::hash` specialization, etc.). And it only works for interfaces that are specifically designed to be specialized this way - not for vanilla dynamic dispatch, say.