commit | 85e6ab1de56ec8cb937a8c584c14e684357ffc3b | [log] [tgz] |
---|---|---|
author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Mar 08 15:41:29 2023 +0000 |
committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Mar 08 15:41:29 2023 +0000 |
tree | f4824cef7c18434e47696e520e4167a43a0b7c41 | |
parent | 3f023437ef28c396b2b7f43f6ecb4e76617d6f70 [diff] | |
parent | 7cd1272f9094fe6e43e00542b445ab4f081607af [diff] |
Snap for 9710098 from 7cd1272f9094fe6e43e00542b445ab4f081607af to mainline-tzdata5-release Change-Id: If31dcdd02f1e9c298fbafd386668310508be3d34
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)
.