commit | c22f8cd1211b7aaa977b0df73957c596d1a5e994 | [log] [tgz] |
---|---|---|
author | Matthew Maurer <mmaurer@google.com> | Tue Jun 14 15:57:18 2022 -0700 |
committer | Matthew Maurer <mmaurer@google.com> | Tue Jun 14 15:57:18 2022 -0700 |
tree | 0a2877e03b38e1209fe8f8f3ef05f50c63e19f9e | |
parent | 63ade5ef23cf6d3e74c5a6a6f539d48afbe90d01 [diff] |
Update TEST_MAPPING Test: None Bug: 236006683 Change-Id: Ibb583d8ef8396b7ca9a7053a76878894215eb96d
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)
.