commit | 856ed9a3e6ab64e36a42aa2032a7bbbcc553f66f | [log] [tgz] |
---|---|---|
author | Bob Badour <bbadour@google.com> | Wed Jan 05 11:10:55 2022 -0800 |
committer | Bob Badour <bbadour@google.com> | Wed Jan 05 11:10:55 2022 -0800 |
tree | df203de1940d8a090d6e47d90d82252c7274f18e | |
parent | 539e63f8e38961ca6ebe153aa63777b4abcaeebb [diff] |
[LSC] Add LOCAL_LICENSE_KINDS to external/rust/crates/enumn Added SPDX-license-identifier-Apache-2.0 SPDX-license-identifier-MIT to: Android.bp Bug: 68860345 Bug: 151177513 Bug: 151953481 Test: m all Change-Id: I185ebe503cc46e2a4b066b2fd86020a1e0544497
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)
.