Ideas around anonymous enum types

[scottmcm]

@Ixrec

The usual stumbling block for anonymous enum proposals is that nobody can seem to come up with a good syntax for matching on the variants.

To me, at least, there's only one syntax I've ever seen brought up that isn't horrible:

Pre-RFC: Using existing structs and tuple-structs as enum variants

With type ascription in patterns appearing plausibly-going-to-happen, I more than ever think that this is the right way for this to be consumed: match x { y: Ipv4Addr => ..., z: Ipv6Addr => ..., } I don’t know the rest of the design, though Perhaps the answer is that if the types are the same, it runs the first matching arm – like it would if you translated it into a sequence of downcasts off an any. And yes, that means you can’t use it place of Result, but I …

Given that, the stumbling block is instead arguments over whether enum(i32 | i32 | i32) and enum(i32 | i32) are the same type, and corresponding specialization-like questions around whether enum(&'a i32 | &'b i32) can be a legal type.