Add a way to iterate over all values in any enum

language design
1

I believe it could be good to add a way to iterate over all values of any enum, I fell there are a lot of use cases for it

2

The strum crate provides this with #[derive(EnumIter)].

1 Like
3

Do you mean over C-like or an enum where all variants are non-tuple and non-struct? As an example, what are the values of

enum Hmm {
    Big(u64),
    Other,
}

or

enum Weird {
    File(std::fs::File),
    Vector(Vec<bool>),
}
4

I don't think I've ever wanted iteration for such an enum, but strum opts for [Big(0), Other]. I think a derive macro which recursively iterates enums could be derived from strum's macro, if that's what's desired.

5

I can't say I've wanted it either, but "all values of any enum" is quite a bit more than what strum is doing there. Of course, this isn't even in a pre-pre-pre-RFC form, so knowing whether such a phrasing is intentional or not realizing what such a phrasing would imply is difficult to discern without asking such questions (IMO).

3 Likes
6

Usually what I need is a visitor or mutable visitor on such types to do recursive descent on every field. There's no sugar for it, but the code is straightforward and a proc-macro (or even a regular macro) can be written for it too.

1 Like
7

Anything prevents from implementing an Iterator for the enum? I don't really see the use case, though. Can you explain one or two of them?

8

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