[lib] Can we add an enum `Either` in std?

libs
22

The futures crate already provides an either for that case.

1 Like
23

Yes, but impl Trait is not just for futures. It is now a core language feature, should have good library support as well.

1 Like
24

I think we should consider extending the language with anonymous sum types instead.

A lot of the frunk crate is essentially a hack around that.

3 Likes
25

A|B types?

1 Like
26

Yes, those; See also https://github.com/rust-lang/rfcs/issues/294

1 Like
27

Huh. I’d’ve thought the syntax would be more like:

let x = (&str, i32, i32)::2(1);
match x {
    <x>::0(s) => ...,
    <x>::1(i) => ...,
    <x>::2(j) => ...,
}

But okay… (this would be the opposite of a tuple - while a tuple’s attribute operates on values (t.0, t.1, etc), a summer’s attribute operates on types (T::0, T::1, etc))

(alternatively it wouldn’t support repeated types at all and construction and matching would be trivial)

1 Like
28

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