commit | 63ade5ef23cf6d3e74c5a6a6f539d48afbe90d01 | [log] [tgz] |
---|---|---|
author | Matthew Maurer <mmaurer@google.com> | Thu May 26 10:55:54 2022 -0700 |
committer | Matthew Maurer <mmaurer@google.com> | Thu May 26 10:55:54 2022 -0700 |
tree | 90753994e8d921a60a8760d2c639c883309e666d | |
parent | 2f975df577f1413d869988c92ec5461c21479dff [diff] |
Update TEST_MAPPING Test: None Bug: 233924440 Change-Id: I54b9cf461433ef993c5e8ed5e58b7a99991a8c72
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)
.