Auto merge of #86860 - fee1-dead:stabilize, r=LeSeulArtichaut
Stabilize `arbitrary_enum_discriminant` Closes #60553. ---- ## Stabilization Report _copied from https://github.com/rust-lang/rust/issues/60553#issuecomment-865922311_ ### Summary Enables a user to specify *explicit* discriminants on arbitrary enums. Previously, this was hard to achieve: ```rust #[repr(u8)] enum Foo { A(u8) = 0, B(i8) = 1, C(bool) = 42, } ``` Someone would need to add 41 hidden variants in between as a workaround with implicit discriminants. In conjunction with [RFC 2195](https://github.com/rust-lang/rfcs/blob/master/text/2195-really-tagged-unions.md), this feature would provide more flexibility for FFI and unsafe code involving enums. ### Test cases Most tests are in [`src/test/ui/enum-discriminant`](https://github.com/rust-lang/rust/tree/master/src/test/ui/enum-discriminant), there are two [historical](https://github.com/rust-lang/rust/blob/master/src/test/ui/parser/tag-variant-disr-non-nullary.rs) [tests](https://github.com/rust-lang/rust/blob/master/src/test/ui/parser/issue-17383.rs) that are now covered by the feature (removed by this pr due to them being obsolete). ### Edge cases The feature is well defined and does not have many edge cases. One [edge case](https://github.com/rust-lang/rust/issues/70509) was related to another unstable feature named `repr128` and is resolved. ### Previous PRs The [implementation PR](https://github.com/rust-lang/rust/pull/60732) added documentation to the Unstable Book, https://github.com/rust-lang/reference/pull/1055 was opened as a continuation of https://github.com/rust-lang/reference/pull/639. ### Resolution of unresolved questions The questions are resolved in https://github.com/rust-lang/rust/issues/60553#issuecomment-511235271. ---- (someone please add `needs-fcp`)
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21 changed files with 13 additions and 221 deletions
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#![crate_type="lib"]
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#![feature(arbitrary_enum_discriminant)]
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enum Enum {
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//~^ ERROR `#[repr(inttype)]` must be specified
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error[E0732]: `#[repr(inttype)]` must be specified
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--> $DIR/arbitrary_enum_discriminant-no-repr.rs:4:1
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--> $DIR/arbitrary_enum_discriminant-no-repr.rs:3:1
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LL | / enum Enum {
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LL | |
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// run-pass
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#![feature(arbitrary_enum_discriminant, const_raw_ptr_deref, test)]
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#![feature(const_raw_ptr_deref, test)]
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extern crate test;
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// run-pass
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#![allow(stable_features)]
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#![feature(arbitrary_enum_discriminant, core, core_intrinsics)]
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#![feature(core, core_intrinsics)]
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extern crate core;
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use core::intrinsics::discriminant_value;
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#![crate_type="lib"]
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enum Enum {
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Unit = 1,
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//~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
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Tuple() = 2,
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//~^ ERROR discriminants on non-unit variants are experimental
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Struct{} = 3,
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//~^ ERROR discriminants on non-unit variants are experimental
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}
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error[E0658]: discriminants on non-unit variants are experimental
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--> $DIR/feature-gate-arbitrary_enum_discriminant.rs:6:13
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LL | Tuple() = 2,
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| ^
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= note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
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= help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
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error[E0658]: discriminants on non-unit variants are experimental
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--> $DIR/feature-gate-arbitrary_enum_discriminant.rs:8:14
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LL | Struct{} = 3,
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| ^
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= note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
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= help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
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error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
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--> $DIR/feature-gate-arbitrary_enum_discriminant.rs:4:10
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LL | Unit = 1,
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| ^ disallowed custom discriminant
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LL |
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LL | Tuple() = 2,
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| ----------- tuple variant defined here
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LL |
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LL | Struct{} = 3,
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| ------------ struct variant defined here
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= note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
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= help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0658`.
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#![feature(arbitrary_enum_discriminant, core_intrinsics)]
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#![feature(core_intrinsics)]
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extern crate core;
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use core::intrinsics::discriminant_value;
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#![feature(arbitrary_enum_discriminant, core_intrinsics)]
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#![feature(core_intrinsics)]
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extern crate core;
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use core::intrinsics::discriminant_value;
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// run-pass
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#![feature(repr128, arbitrary_enum_discriminant)]
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#![feature(repr128)]
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//~^ WARN the feature `repr128` is incomplete
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#[derive(PartialEq, Debug)]
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warning: the feature `repr128` is incomplete and may not be safe to use and/or cause compiler crashes
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--> $DIR/issue-70509-partial_eq.rs:2:12
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LL | #![feature(repr128, arbitrary_enum_discriminant)]
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LL | #![feature(repr128)]
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| ^^^^^^^
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= note: `#[warn(incomplete_features)]` on by default
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// This test checks panic emitted from `mem::{uninitialized,zeroed}`.
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#![feature(never_type, arbitrary_enum_discriminant)]
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#![feature(never_type)]
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#![allow(deprecated, invalid_value)]
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use std::{
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enum X {
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A = 3,
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//~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
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B(usize)
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}
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fn main() {}
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error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
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--> $DIR/issue-17383.rs:2:9
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LL | A = 3,
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| ^ disallowed custom discriminant
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LL |
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LL | B(usize)
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| -------- tuple variant defined here
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= note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
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= help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0658`.
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enum Color {
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Red = 0xff0000,
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//~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
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Green = 0x00ff00,
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Blue = 0x0000ff,
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Black = 0x000000,
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White = 0xffffff,
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Other(usize),
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Other2(usize, usize),
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}
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fn main() {}
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error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
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--> $DIR/tag-variant-disr-non-nullary.rs:2:11
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LL | Red = 0xff0000,
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| ^^^^^^^^ disallowed custom discriminant
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LL |
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LL | Green = 0x00ff00,
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| ^^^^^^^^ disallowed custom discriminant
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LL | Blue = 0x0000ff,
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| ^^^^^^^^ disallowed custom discriminant
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LL | Black = 0x000000,
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| ^^^^^^^^ disallowed custom discriminant
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LL | White = 0xffffff,
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| ^^^^^^^^ disallowed custom discriminant
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LL | Other(usize),
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| ------------ tuple variant defined here
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LL | Other2(usize, usize),
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| -------------------- tuple variant defined here
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= note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
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= help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0658`.
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