[PreRFC] enum-variant-types

[Jules-Bertholet]

A more general version of this feature has been discussed under the name "pattern types".

Wayback Machine

Pattern types MVP

Thoughts on pattern types and subtyping

Recently, there has been a lot of discussion about some form of "pattern types" or "value-restricted types": types that are just like a base type, but restricted to a narrower set of values. I've been thinking about this for a while, and there are some important subtleties to consider, relating to subtyping. Introduction @oli-obk's post is a good introduction to this feature. The basic idea is that you take a type, say i32, you take a pattern that matches on that type, say 1..3, and you get a …