Hi Am 2025-03-11 22:45, schrieb Larry Garfield:
We should not block this kind of improvement on the hope of generics. Worst case, we have this plus generics so you have options, how terrible.
In this case, I agree. This is an obvious addition to the type system that uses the existing infrastructure of the type system.
But generally speaking, having too many options is not a good thing. It makes the language larger and more complex to learn, requires documentation effort, support by IDEs and static analyzers and similar things.
Rust-style associated types would probably work as well. I'd be fine with that approach, too. One could argue they're more valuable as a sort of "junior generics," but absent anyone able and willing to implement them, again, worst-case we end up with options in the future.
… so for associated types, I do not necessarily agree. They seem to be a strict subset of the functionality enabled by generics, or the functionality enabled by type aliases combined with “inner classes / inner types”. Since introducing associated types would bring entirely new syntax and semantics to the language, it is less obvious to me that they are a useful (intermediate) addition to the language.
Best regards Tim Düsterhus
