Subset enums

I see this:

PreRFC] enum-variant-types [language design

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

Which after digging on the closed and unmerged MVP PR brings up this:

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Which was left @

In June 2023.

There's an older thread from 2018 which mentioned this and ended as:

However I cannot find the newer thread, the one that mentioned it was about floating point rounding. Is it this commit: Rollup merge of #123648 - oli-obk:pattern_types_syntax, r=compiler-er… · rust-lang/rust@727c31a · GitHub

Does that mean it is in the current version of Rust? How do we use it?

Ahhh... It seems it is internal only and worked only for ranges: Implement minimal, internal-only pattern types in the type system by oli-obk · Pull Request #120131 · rust-lang/rust · GitHub

So basically, this is all still in flux and not currently being worked on? Not saying that is negative, I am just trying to understand where things are at the moment.