commit | 16f01394451f75e73d1a138aba7551c874db7258 | [log] [tgz] |
---|---|---|
author | David Drysdale <drysdale@google.com> | Thu May 26 15:59:25 2022 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Thu May 26 15:59:25 2022 +0000 |
tree | 148758f776080cbfcdf37b75de4f4195eb477cb7 | |
parent | dd00740b1d48623da248e01beeae74ddd16fd627 [diff] | |
parent | 3615f88937d381549531e14dd2b51e63f660f285 [diff] |
Make crate vendor_available am: a07da2af9a am: 3615f88937 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/enumn/+/2106347 Change-Id: I3cc7856bdb80a0ce7da6686298fc84ae6b3de083 Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
This crate provides a derive macro to generate a function for converting a primitive integer into the corresponding variant of an enum.
The generated function is named n
and has the following signature:
impl YourEnum { pub fn n(value: Repr) -> Option<Self>; }
where Repr
is an integer type of the right size as described in more detail below.
use enumn::N; #[derive(PartialEq, Debug, N)] enum Status { LegendaryTriumph, QualifiedSuccess, FortuitousRevival, IndeterminateStalemate, RecoverableSetback, DireMisadventure, AbjectFailure, } fn main() { let s = Status::n(1); assert_eq!(s, Some(Status::QualifiedSuccess)); let s = Status::n(9); assert_eq!(s, None); }
The generated signature depends on whether the enum has a #[repr(..)]
attribute. If a repr
is specified, the input to n
will be required to be of that type.
#[derive(enumn::N)] #[repr(u8)] enum E { /* ... */ } // expands to: impl E { pub fn n(value: u8) -> Option<Self> { /* ... */ } }
On the other hand if no repr
is specified then we get a signature that is generic over a variety of possible types.
impl E { pub fn n<REPR: Into<i64>>(value: REPR) -> Option<Self> { /* ... */ } }
The conversion respects explictly specified enum discriminants. Consider this enum:
#[derive(enumn::N)] enum Letter { A = 65, B = 66, }
Here Letter::n(65)
would return Some(Letter::A)
.