tag | 028b0e8a31063c880b1d837ddfa0da762bbbf3b7 | |
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tagger | The Android Open Source Project <initial-contribution@android.com> | Sat Oct 01 12:32:21 2022 -0700 |
object | 48de6fd87db964c2dcc4784b7ed15f2572f02ca0 |
aml_go_doc_330912000
commit | 48de6fd87db964c2dcc4784b7ed15f2572f02ca0 | [log] [tgz] |
---|---|---|
author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Thu Jun 16 22:00:06 2022 +0000 |
committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Thu Jun 16 22:00:06 2022 +0000 |
tree | 0a2877e03b38e1209fe8f8f3ef05f50c63e19f9e | |
parent | dd00740b1d48623da248e01beeae74ddd16fd627 [diff] | |
parent | 57038662745311c211a8484f68314af288c8adc4 [diff] |
Snap for 8736029 from 57038662745311c211a8484f68314af288c8adc4 to mainline-go-documentsui-release Change-Id: I00c27a482bfde7d5d0fc79b2c8581d92650607d2
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)
.