commit | 85b309db0796b83cbbd8f008cfb5c667a3576b06 | [log] [tgz] |
---|---|---|
author | James Farrell <jamesfarrell@google.com> | Mon May 20 16:53:01 2024 +0000 |
committer | James Farrell <jamesfarrell@google.com> | Mon May 20 16:53:01 2024 +0000 |
tree | f607d2e4ab03c334dae807ba5f0de89c79720a33 | |
parent | f94dc0c912d8a5d41b600c2301a4e1e906d901d3 [diff] |
Update Android.bp by running cargo_embargo Test: ran cargo_embargo Change-Id: I6b679f71fd71ffb59f2ac7bed19ff9ef3388c0f1
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)
.