> I don't think this is true. Anyone who can see both the type and the type > class visible can declare an instance. This is very convenient and something > that should be retained in a potential Rust version, IMO.
I indeed can't find anything about this in a quick scanning of the standard. Maybe it's another language that does it this way, or maybe I'm just completely making things up here. Declaring instances anywhere is a gain in expressiveness, but does lead to the unsavory possibility of clashes, when linking stuff together that declares two different instances for a type/class pair. (I also assumed this would lead to not being able to determine which instance to use statically, but actually that's not much of a problem--it'd just be a compile-time error to use a value of type X where class Y was expected unless the compiler can see that X was declared instance of Y somewhere in the linked libraries.) _______________________________________________ Rust-dev mailing list [email protected] https://mail.mozilla.org/listinfo/rust-dev
