commit | 2c792c5a026eab5d60e10b8fd798f827ef596004 | [log] [tgz] |
---|---|---|
author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed May 10 16:17:04 2023 +0000 |
committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed May 10 16:17:04 2023 +0000 |
tree | 8ae195a806078dddb243dd9857481738fdc27cb7 | |
parent | 85e6ab1de56ec8cb937a8c584c14e684357ffc3b [diff] | |
parent | 49a3012dee89afb715c0522baab3c5132d91c53c [diff] |
Snap for 10103804 from 49a3012dee89afb715c0522baab3c5132d91c53c to mainline-tzdata5-release Change-Id: Ia739f69f2eeaa0e9fdd4ac24d87d4f605ea95ab5
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)
.