Even PHP as traits by now. Languages tend to incorporate others Languages successful features. There is of course feature inflation risk of course. There are Languages that take as a goal to avoid that inflation, such as Zig, or that arrives there as a byproduct of being very focused in a specific use case like AWK.
AFAIK composition, in the traditional sense, means that you put your objects/concepts together from different smaller objects or concepts. Composition would be to have a struct Car that uses another struct called Engine to handle its driving needs. A car “has a” engine. A trait that implements the “this thing has an engine” behavior isn’t composition, it’s actually much closer to [multiple] inheritance (a car “is a” motorized vehicle).
Traits do implement interface inheritance, but that doesn't have the same general drawbacks as implementation inheritance (such as the well-known "fragile base class" problem).
I don't know the terminology. I just know that Rust does whatever the alternative is to the Java way with inheritance. You don't get stuck with the classic classification problem.
If I say "I don't care about safety, I care about expressiveness. Which is Rust's model"... "which" has to refer to one of the other things I just mentioned (safety or expressiveness) not some other concept.
You can also have structs be generic over some "tag" type, which when combined with trait definitions gets you quite close to implementation inheritance as seen in C++ and elsewhere. It's just less common because usually composition is all that's required.
