Messages in this thread | | | Date | Mon, 5 Dec 2022 15:00:05 -0800 | From | Josh Triplett <> | Subject | Re: [PATCH v2 27/28] rust: types: add `Either` type |
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On Sun, Dec 04, 2022 at 05:36:08PM +0000, Wedson Almeida Filho wrote: > On Sun, 4 Dec 2022 at 10:31, Gary Guo <gary@garyguo.net> wrote: > > > > On Fri, 2 Dec 2022 15:41:59 -0800 > > Josh Triplett <josh@joshtriplett.org> wrote: > > > > > On Fri, Dec 02, 2022 at 05:14:58PM +0100, ojeda@kernel.org wrote: > > > > From: Wedson Almeida Filho <wedsonaf@gmail.com> > > > > > > > > Introduce the new `types` module of the `kernel` crate with > > > > `Either` as its first type. > > > > > > > > `Either<L, R>` is a sum type that always holds either a value > > > > of type `L` (`Left` variant) or `R` (`Right` variant). > > > > > > > > For instance: > > > > > > > > struct Executor { > > > > queue: Either<BoxedQueue, &'static Queue>, > > > > } > > > > > > This specific example seems like it would be better served by the > > > existing `Cow` type. > > > > We use `no_global_oom_handling`, which gates most `ToOwned` > > implementations (e.g. `str` cannot implement `to_owned()` because it > > cannot guarantee allocation success). > > > > So the Rust `Cow` is pretty much useless in the kernel. > > It's also implemented in `std`, which the kernel doesn't include. > (Which is actually good for us, since we can't really use it.) > > Josh, how do you feel about adding a `TryToOwned` trait to > `core::borrow`? This would be similar to the precedent of `TryFrom` in > addition to `From` for the fallible case, and would be usable by the > kernel.
I'd expect it to be in alloc rather than core (though I suppose it doesn't *fundamentally* depend on an allocator itself), but I'd be happy to see a fallible version proposed, yeah.
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