Rollup merge of #95710 - fee1-dead-contrib:stabilize_arbitrary_enum_discriminant, r=joshtriplett

Stabilize arbitrary_enum_discriminant, take 2

Documentation has been updated in https://github.com/rust-lang/reference/pull/1055. cc #86860 for previous stabilization report.

Not yet marks https://github.com/rust-lang/rust/issues/60553 as done: need documentation in the rust reference.

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -1,7 +1,7 @@
 use rustc_ast as ast;
 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
 use rustc_ast::{AssocConstraint, AssocConstraintKind, NodeId};
-use rustc_ast::{PatKind, RangeEnd, VariantData};
+use rustc_ast::{PatKind, RangeEnd};
 use rustc_errors::{struct_span_err, Applicability, StashKey};
 use rustc_feature::{AttributeGate, BuiltinAttribute, Features, GateIssue, BUILTIN_ATTRIBUTE_MAP};
 use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
@@ -116,46 +116,6 @@ impl<'a> PostExpansionVisitor<'a> {
         }
     }
 
-    fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
-        let has_fields = variants.iter().any(|variant| match variant.data {
-            VariantData::Tuple(..) | VariantData::Struct(..) => true,
-            VariantData::Unit(..) => false,
-        });
-
-        let discriminant_spans = variants
-            .iter()
-            .filter(|variant| match variant.data {
-                VariantData::Tuple(..) | VariantData::Struct(..) => false,
-                VariantData::Unit(..) => true,
-            })
-            .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
-            .collect::<Vec<_>>();
-
-        if !discriminant_spans.is_empty() && has_fields {
-            let mut err = feature_err(
-                &self.sess.parse_sess,
-                sym::arbitrary_enum_discriminant,
-                discriminant_spans.clone(),
-                "custom discriminant values are not allowed in enums with tuple or struct variants",
-            );
-            for sp in discriminant_spans {
-                err.span_label(sp, "disallowed custom discriminant");
-            }
-            for variant in variants.iter() {
-                match &variant.data {
-                    VariantData::Struct(..) => {
-                        err.span_label(variant.span, "struct variant defined here");
-                    }
-                    VariantData::Tuple(..) => {
-                        err.span_label(variant.span, "tuple variant defined here");
-                    }
-                    VariantData::Unit(..) => {}
-                }
-            }
-            err.emit();
-        }
-    }
-
     /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
     fn check_impl_trait(&self, ty: &ast::Ty) {
         struct ImplTraitVisitor<'a> {
@@ -273,26 +233,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
 
-            ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
-                for variant in variants {
-                    match (&variant.data, &variant.disr_expr) {
-                        (ast::VariantData::Unit(..), _) => {}
-                        (_, Some(disr_expr)) => gate_feature_post!(
-                            &self,
-                            arbitrary_enum_discriminant,
-                            disr_expr.value.span,
-                            "discriminants on non-unit variants are experimental"
-                        ),
-                        _ => {}
-                    }
-                }
-
-                let has_feature = self.features.arbitrary_enum_discriminant;
-                if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
-                    self.maybe_report_invalid_custom_discriminants(&variants);
-                }
-            }
-
             ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
                 if let ast::ImplPolarity::Negative(span) = polarity {
                     gate_feature_post!(

compiler/rustc_error_codes/src/error_codes/E0732.md

@@ -3,8 +3,6 @@ An `enum` with a discriminant must specify a `#[repr(inttype)]`.
 Erroneous code example:
 
 ```compile_fail,E0732
-#![feature(arbitrary_enum_discriminant)]
-
 enum Enum { // error!
     Unit = 1,
     Tuple() = 2,
@@ -20,8 +18,6 @@ is a well-defined way to extract a variant's discriminant from a value;
 for instance:
 
 ```
-#![feature(arbitrary_enum_discriminant)]
-
 #[repr(u8)]
 enum Enum {
     Unit = 3,

compiler/rustc_feature/src/accepted.rs

@@ -53,6 +53,8 @@ declare_features! (
     (accepted, abi_sysv64, "1.24.0", Some(36167), None),
     /// Allows using ADX intrinsics from `core::arch::{x86, x86_64}`.
     (accepted, adx_target_feature, "1.61.0", Some(44839), None),
+    /// Allows explicit discriminants on non-unit enum variants.
+    (accepted, arbitrary_enum_discriminant, "CURRENT_RUSTC_VERSION", Some(60553), None),
     /// Allows using `sym` operands in inline assembly.
     (accepted, asm_sym, "CURRENT_RUSTC_VERSION", Some(93333), None),
     /// Allows the definition of associated constants in `trait` or `impl` blocks.

compiler/rustc_feature/src/active.rs

@@ -292,8 +292,6 @@ declare_features! (
     (incomplete, adt_const_params, "1.56.0", Some(95174), None),
     /// Allows defining an `#[alloc_error_handler]`.
     (active, alloc_error_handler, "1.29.0", Some(51540), None),
-    /// Allows explicit discriminants on non-unit enum variants.
-    (active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
     /// Allows trait methods with arbitrary self types.
     (active, arbitrary_self_types, "1.23.0", Some(44874), None),
     /// Allows using `const` operands in inline assembly.

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1180,7 +1180,7 @@ fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, vs: &'tcx [hir::Variant<'tcx>], def_id: L
         }
     }
 
-    if tcx.adt_def(def_id).repr().int.is_none() && tcx.features().arbitrary_enum_discriminant {
+    if tcx.adt_def(def_id).repr().int.is_none() {
         let is_unit = |var: &hir::Variant<'_>| matches!(var.data, hir::VariantData::Unit(..));
 
         let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();

src/doc/unstable-book/src/language-features/arbitrary-enum-discriminant.md

@@ -1,37 +0,0 @@
-# `arbitrary_enum_discriminant`
-
-The tracking issue for this feature is: [#60553]
-
-[#60553]: https://github.com/rust-lang/rust/issues/60553
-
-------------------------
-
-The `arbitrary_enum_discriminant` feature permits tuple-like and
-struct-like enum variants with `#[repr(<int-type>)]` to have explicit discriminants.
-
-## Examples
-
-```rust
-#![feature(arbitrary_enum_discriminant)]
-
-#[allow(dead_code)]
-#[repr(u8)]
-enum Enum {
-    Unit = 3,
-    Tuple(u16) = 2,
-    Struct {
-        a: u8,
-        b: u16,
-    } = 1,
-}
-
-impl Enum {
-    fn tag(&self) -> u8 {
-        unsafe { *(self as *const Self as *const u8) }
-    }
-}
-
-assert_eq!(3, Enum::Unit.tag());
-assert_eq!(2, Enum::Tuple(5).tag());
-assert_eq!(1, Enum::Struct{a: 7, b: 11}.tag());
-```

src/test/ui/cast/issue-88621.rs

@@ -1,5 +1,3 @@
-#![feature(arbitrary_enum_discriminant)]
-
 #[repr(u8)]
 enum Kind2 {
     Foo() = 1,

src/test/ui/cast/issue-88621.stderr

@@ -1,5 +1,5 @@
 error[E0605]: non-primitive cast: `Kind2` as `u8`
-  --> $DIR/issue-88621.rs:11:13
+  --> $DIR/issue-88621.rs:9:13
    |
 LL |     let _ = Kind2::Foo() as u8;
    |             ^^^^^^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object

src/test/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.rs

@@ -1,5 +1,4 @@
 #![crate_type="lib"]
-#![feature(arbitrary_enum_discriminant)]
 
 enum Enum {
 //~^ ERROR `#[repr(inttype)]` must be specified

src/test/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.stderr

@@ -1,5 +1,5 @@
 error[E0732]: `#[repr(inttype)]` must be specified
-  --> $DIR/arbitrary_enum_discriminant-no-repr.rs:4:1
+  --> $DIR/arbitrary_enum_discriminant-no-repr.rs:3:1
    |
 LL | enum Enum {
    | ^^^^^^^^^

src/test/ui/enum-discriminant/arbitrary_enum_discriminant.rs

@@ -1,5 +1,5 @@
 // run-pass
-#![feature(arbitrary_enum_discriminant, test)]
+#![feature(test)]
 
 extern crate test;
 

src/test/ui/enum-discriminant/discriminant_value.rs

@@ -1,6 +1,6 @@
 // run-pass
 #![allow(stable_features)]
-#![feature(arbitrary_enum_discriminant, core, core_intrinsics)]
+#![feature(core, core_intrinsics)]
 
 extern crate core;
 use core::intrinsics::discriminant_value;

src/test/ui/enum-discriminant/feature-gate-arbitrary_enum_discriminant.rs

@@ -1,10 +0,0 @@
-#![crate_type="lib"]
-
-enum Enum {
-  Unit = 1,
-  //~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
-  Tuple() = 2,
-  //~^ ERROR discriminants on non-unit variants are experimental
-  Struct{} = 3,
-  //~^ ERROR discriminants on non-unit variants are experimental
-}

src/test/ui/enum-discriminant/feature-gate-arbitrary_enum_discriminant.stderr

@@ -1,36 +0,0 @@
-error[E0658]: discriminants on non-unit variants are experimental
-  --> $DIR/feature-gate-arbitrary_enum_discriminant.rs:6:13
-   |
-LL |   Tuple() = 2,
-   |             ^
-   |
-   = note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
-   = help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
-
-error[E0658]: discriminants on non-unit variants are experimental
-  --> $DIR/feature-gate-arbitrary_enum_discriminant.rs:8:14
-   |
-LL |   Struct{} = 3,
-   |              ^
-   |
-   = note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
-   = help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
-
-error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
-  --> $DIR/feature-gate-arbitrary_enum_discriminant.rs:4:10
-   |
-LL |   Unit = 1,
-   |          ^ disallowed custom discriminant
-LL |
-LL |   Tuple() = 2,
-   |   ----------- tuple variant defined here
-LL |
-LL |   Struct{} = 3,
-   |   ------------ struct variant defined here
-   |
-   = note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
-   = help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
-
-error: aborting due to 3 previous errors
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/enum-discriminant/issue-70453-generics-in-discr-ice-2.rs

@@ -1,4 +1,4 @@
-#![feature(arbitrary_enum_discriminant, core_intrinsics)]
+#![feature(core_intrinsics)]
 
 extern crate core;
 use core::intrinsics::discriminant_value;

src/test/ui/enum-discriminant/issue-70453-polymorphic-ctfe.rs

@@ -1,4 +1,4 @@
-#![feature(arbitrary_enum_discriminant, core_intrinsics)]
+#![feature(core_intrinsics)]
 
 extern crate core;
 use core::intrinsics::discriminant_value;

src/test/ui/enum-discriminant/issue-70509-partial_eq.rs

@@ -1,5 +1,5 @@
 // run-pass
-#![feature(repr128, arbitrary_enum_discriminant)]
+#![feature(repr128)]
 //~^ WARN the feature `repr128` is incomplete
 
 #[derive(PartialEq, Debug)]

src/test/ui/enum-discriminant/issue-70509-partial_eq.stderr

@@ -1,7 +1,7 @@
 warning: the feature `repr128` is incomplete and may not be safe to use and/or cause compiler crashes
   --> $DIR/issue-70509-partial_eq.rs:2:12
    |
-LL | #![feature(repr128, arbitrary_enum_discriminant)]
+LL | #![feature(repr128)]
    |            ^^^^^^^
    |
    = note: see issue #56071 <https://github.com/rust-lang/rust/issues/56071> for more information

src/test/ui/intrinsics/panic-uninitialized-zeroed.rs

@@ -7,7 +7,7 @@
 
 // This test checks panic emitted from `mem::{uninitialized,zeroed}`.
 
-#![feature(never_type, arbitrary_enum_discriminant)]
+#![feature(never_type)]
 #![allow(deprecated, invalid_value)]
 
 use std::{

src/test/ui/macros/macros-nonfatal-errors.rs

@@ -4,7 +4,7 @@
 // immediately, so that we get more errors listed at a time.
 
 #![feature(trace_macros, concat_idents)]
-#![feature(stmt_expr_attributes, arbitrary_enum_discriminant)]
+#![feature(stmt_expr_attributes)]
 
 use std::arch::asm;
 

src/test/ui/parser/issues/issue-17383.rs

@@ -1,7 +0,0 @@
-enum X {
-    A = 3,
-    //~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
-    B(usize)
-}
-
-fn main() {}

src/test/ui/parser/issues/issue-17383.stderr

@@ -1,15 +0,0 @@
-error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
-  --> $DIR/issue-17383.rs:2:9
-   |
-LL |     A = 3,
-   |         ^ disallowed custom discriminant
-LL |
-LL |     B(usize)
-   |     -------- tuple variant defined here
-   |
-   = note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
-   = help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/parser/tag-variant-disr-non-nullary.rs

@@ -1,12 +0,0 @@
-enum Color {
-    Red = 0xff0000,
-    //~^ ERROR custom discriminant values are not allowed in enums with tuple or struct variants
-    Green = 0x00ff00,
-    Blue = 0x0000ff,
-    Black = 0x000000,
-    White = 0xffffff,
-    Other(usize),
-    Other2(usize, usize),
-}
-
-fn main() {}

src/test/ui/parser/tag-variant-disr-non-nullary.stderr

@@ -1,25 +0,0 @@
-error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
-  --> $DIR/tag-variant-disr-non-nullary.rs:2:11
-   |
-LL |     Red = 0xff0000,
-   |           ^^^^^^^^ disallowed custom discriminant
-LL |
-LL |     Green = 0x00ff00,
-   |             ^^^^^^^^ disallowed custom discriminant
-LL |     Blue = 0x0000ff,
-   |            ^^^^^^^^ disallowed custom discriminant
-LL |     Black = 0x000000,
-   |             ^^^^^^^^ disallowed custom discriminant
-LL |     White = 0xffffff,
-   |             ^^^^^^^^ disallowed custom discriminant
-LL |     Other(usize),
-   |     ------------ tuple variant defined here
-LL |     Other2(usize, usize),
-   |     -------------------- tuple variant defined here
-   |
-   = note: see issue #60553 <https://github.com/rust-lang/rust/issues/60553> for more information
-   = help: add `#![feature(arbitrary_enum_discriminant)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/transmutability/enums/should_order_correctly.rs

@@ -2,7 +2,6 @@
 //! The payloads of an enum variant should be ordered after its tag.
 
 #![crate_type = "lib"]
-#![feature(arbitrary_enum_discriminant)]
 #![feature(transmutability)]
 #![allow(dead_code)]
 

src/test/ui/transmutability/enums/should_respect_endianness.rs

@@ -2,7 +2,6 @@
 //! an enum with a multi-byte tag.
 
 #![crate_type = "lib"]
-#![feature(arbitrary_enum_discriminant)]
 #![feature(transmutability)]
 #![allow(dead_code)]
 

src/test/ui/transmutability/enums/should_respect_endianness.stderr

@@ -1,12 +1,12 @@
 error[E0277]: `Src` cannot be safely transmuted into `Unexpected` in the defining scope of `assert::Context`.
-  --> $DIR/should_respect_endianness.rs:37:36
+  --> $DIR/should_respect_endianness.rs:36:36
    |
 LL |     assert::is_transmutable::<Src, Unexpected>();
    |                                    ^^^^^^^^^^ `Src` cannot be safely transmuted into `Unexpected` in the defining scope of `assert::Context`.
    |
    = help: the trait `BikeshedIntrinsicFrom<Src, assert::Context, Assume { alignment: true, lifetimes: true, safety: true, validity: true }>` is not implemented for `Unexpected`
 note: required by a bound in `is_transmutable`
-  --> $DIR/should_respect_endianness.rs:15:14
+  --> $DIR/should_respect_endianness.rs:14:14
    |
 LL |       pub fn is_transmutable<Src, Dst>()
    |              --------------- required by a bound in this