commit | 14990a7f0d6a0c95bc99d2b878254a7bea7de4b9 | [log] [tgz] |
---|---|---|
author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Sat Jan 08 04:05:53 2022 +0000 |
committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Sat Jan 08 04:05:53 2022 +0000 |
tree | df203de1940d8a090d6e47d90d82252c7274f18e | |
parent | 9ca1b7187e8cd56973ee2a256a8240a8fedd9852 [diff] | |
parent | d5b902757f8a5b144c813e6838b16b32bd1ec76a [diff] |
Snap for 8055626 from d5b902757f8a5b144c813e6838b16b32bd1ec76a to tm-release Change-Id: If8fa89d41eb7776bd9ee0d625c9c401138d39703
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)
.