commit | d5b902757f8a5b144c813e6838b16b32bd1ec76a | [log] [tgz] |
---|---|---|
author | Bob Badour <bbadour@google.com> | Fri Jan 07 01:29:43 2022 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Fri Jan 07 01:29:43 2022 +0000 |
tree | df203de1940d8a090d6e47d90d82252c7274f18e | |
parent | cfed7c3ab22c56d44c873feb7876b1310013b1ea [diff] | |
parent | da90a1291fcdb45a57b5ad815c13b3458f9345f6 [diff] |
[LSC] Add LOCAL_LICENSE_KINDS to external/rust/crates/enumn am: 856ed9a3e6 am: 6f13c54e52 am: 7b3936c29a am: da90a1291f Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/enumn/+/1932023 Change-Id: Ie5aa35c94864bd5b5c4c8209131c1fef14f3759b
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)
.