| commit | 1e5d8e387441ce76e713a010be314f9cec25ccf7 | [log] [tgz] |
|---|---|---|
| author | James Farrell <[email protected]> | Mon Aug 26 20:42:40 2024 +0000 |
| committer | James Farrell <[email protected]> | Mon Aug 26 20:42:40 2024 +0000 |
| tree | 5148242dd25dfcc978c0dce380c9e0a588eaf84b | |
| parent | 2209338dfa5a11b836f0e99ba54c6ba6e605bbc3 [diff] |
Migrate 25 crates to monorepo. combine command-fds const-oid coset crc32fast criterion criterion-plot crossbeam-channel crossbeam-deque crossbeam-epoch crossbeam-queue crossbeam-utils darling_core darling_macro dashmap data-encoding der der_derive derive_arbitrary displaydoc document-features downcast-rs drm either enumn Bug: 339424309 Test: treehugger Change-Id: Ic983bf6e2bd0648f437a39b9c6f1209530997e48
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).