Port variance attrs to attr parser.

compiler/rustc_attr_parsing/src/attributes/test_attrs.rs

@@ -91,3 +91,25 @@ impl<S: Stage> SingleAttributeParser<S> for ShouldPanicParser {
         })
     }
 }
+
+pub(crate) struct RustcVarianceParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for RustcVarianceParser {
+    const PATH: &[Symbol] = &[sym::rustc_variance];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Struct),
+        Allow(Target::Enum),
+        Allow(Target::Union),
+    ]);
+    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcVariance;
+}
+
+pub(crate) struct RustcVarianceOfOpaquesParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for RustcVarianceOfOpaquesParser {
+    const PATH: &[Symbol] = &[sym::rustc_variance_of_opaques];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Crate)]);
+    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcVarianceOfOpaques;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -85,7 +85,9 @@ use crate::attributes::semantics::MayDangleParser;
 use crate::attributes::stability::{
     BodyStabilityParser, ConstStabilityIndirectParser, ConstStabilityParser, StabilityParser,
 };
-use crate::attributes::test_attrs::{IgnoreParser, ShouldPanicParser};
+use crate::attributes::test_attrs::{
+    IgnoreParser, RustcVarianceOfOpaquesParser, RustcVarianceParser, ShouldPanicParser,
+};
 use crate::attributes::traits::{
     AllowIncoherentImplParser, CoinductiveParser, DenyExplicitImplParser,
     DoNotImplementViaObjectParser, FundamentalParser, MarkerParser, ParenSugarParser,
@@ -300,6 +302,8 @@ attribute_parsers!(
         Single<WithoutArgs<RustcPassIndirectlyInNonRusticAbisParser>>,
         Single<WithoutArgs<RustcReallocatorParser>>,
         Single<WithoutArgs<RustcShouldNotBeCalledOnConstItems>>,
+        Single<WithoutArgs<RustcVarianceOfOpaquesParser>>,
+        Single<WithoutArgs<RustcVarianceParser>>,
         Single<WithoutArgs<SpecializationTraitParser>>,
         Single<WithoutArgs<StdInternalSymbolParser>>,
         Single<WithoutArgs<ThreadLocalParser>>,

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -1007,6 +1007,12 @@ pub enum AttributeKind {
     /// Represents `#[rustc_simd_monomorphize_lane_limit = "N"]`.
     RustcSimdMonomorphizeLaneLimit(Limit),
 
+    /// Represents `#[rustc_variance]`
+    RustcVariance,
+
+    /// Represents `#[rustc_variance_of_opaques]`
+    RustcVarianceOfOpaques,
+
     /// Represents `#[sanitize]`
     ///
     /// the on set and off set are distjoint since there's a third option: unset.

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -129,6 +129,8 @@ impl AttributeKind {
             RustcScalableVector { .. } => Yes,
             RustcShouldNotBeCalledOnConstItems(..) => Yes,
             RustcSimdMonomorphizeLaneLimit(..) => Yes, // Affects layout computation, which needs to work cross-crate
+            RustcVariance => No,
+            RustcVarianceOfOpaques => No,
             Sanitize { .. } => No,
             ShouldPanic { .. } => No,
             SkipDuringMethodDispatch { .. } => No,

compiler/rustc_hir_analysis/src/variance/dump.rs

@@ -1,8 +1,9 @@
 use std::fmt::Write;
 
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
+use rustc_hir::find_attr;
 use rustc_middle::ty::{GenericArgs, TyCtxt};
-use rustc_span::sym;
 
 fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
     let variances = tcx.variances_of(def_id);
@@ -25,7 +26,7 @@ fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
 pub(crate) fn variances(tcx: TyCtxt<'_>) {
     let crate_items = tcx.hir_crate_items(());
 
-    if tcx.has_attr(CRATE_DEF_ID, sym::rustc_variance_of_opaques) {
+    if find_attr!(tcx.get_all_attrs(CRATE_DEF_ID), AttributeKind::RustcVarianceOfOpaques) {
         for id in crate_items.opaques() {
             tcx.dcx().emit_err(crate::errors::VariancesOf {
                 span: tcx.def_span(id),
@@ -35,7 +36,7 @@ pub(crate) fn variances(tcx: TyCtxt<'_>) {
     }
 
     for id in crate_items.free_items() {
-        if !tcx.has_attr(id.owner_id, sym::rustc_variance) {
+        if !find_attr!(tcx.get_all_attrs(id.owner_id), AttributeKind::RustcVariance) {
             continue;
         }
 

compiler/rustc_passes/src/check_attr.rs

@@ -274,6 +274,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::RustcScalableVector { .. }
                     | AttributeKind::RustcSimdMonomorphizeLaneLimit(..)
                     | AttributeKind::RustcShouldNotBeCalledOnConstItems(..)
+                    | AttributeKind::RustcVariance
+                    | AttributeKind::RustcVarianceOfOpaques
                     | AttributeKind::ExportStable
                     | AttributeKind::FfiConst(..)
                     | AttributeKind::UnstableFeatureBound(..)
@@ -378,8 +380,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             | sym::rustc_capture_analysis
                             | sym::rustc_regions
                             | sym::rustc_strict_coherence
-                            | sym::rustc_variance
-                            | sym::rustc_variance_of_opaques
                             | sym::rustc_hidden_type_of_opaques
                             | sym::rustc_mir
                             | sym::rustc_effective_visibility

tests/ui/feature-gates/feature-gate-rustc-attrs-1.rs

@@ -1,12 +1,14 @@
 // Test that `#[rustc_*]` attributes are gated by `rustc_attrs` feature gate.
 
-#[rustc_variance]
-//~^ ERROR use of an internal attribute [E0658]
-//~| NOTE the `#[rustc_variance]` attribute is an internal implementation detail that will never be stable
-//~| NOTE the `#[rustc_variance]` attribute is used for rustc unit tests
 #[rustc_nonnull_optimization_guaranteed]
 //~^ ERROR use of an internal attribute [E0658]
 //~| NOTE the `#[rustc_nonnull_optimization_guaranteed]` attribute is an internal implementation detail that will never be stable
 //~| NOTE  the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document guaranteed niche optimizations in the standard library
 //~| NOTE the compiler does not even check whether the type indeed is being non-null-optimized; it is your responsibility to ensure that the attribute is only used on types that are optimized
 fn main() {}
+
+#[rustc_variance]
+//~^ ERROR use of an internal attribute [E0658]
+//~| NOTE the `#[rustc_variance]` attribute is an internal implementation detail that will never be stable
+//~| NOTE the `#[rustc_variance]` attribute is used for rustc unit tests
+enum E {}

tests/ui/feature-gates/feature-gate-rustc-attrs-1.stderr

@@ -1,16 +1,6 @@
 error[E0658]: use of an internal attribute
   --> $DIR/feature-gate-rustc-attrs-1.rs:3:1
    |
-LL | #[rustc_variance]
-   | ^^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
-   = note: the `#[rustc_variance]` attribute is an internal implementation detail that will never be stable
-   = note: the `#[rustc_variance]` attribute is used for rustc unit tests
-
-error[E0658]: use of an internal attribute
-  --> $DIR/feature-gate-rustc-attrs-1.rs:7:1
-   |
 LL | #[rustc_nonnull_optimization_guaranteed]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
@@ -19,6 +9,16 @@ LL | #[rustc_nonnull_optimization_guaranteed]
    = note: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document guaranteed niche optimizations in the standard library
    = note: the compiler does not even check whether the type indeed is being non-null-optimized; it is your responsibility to ensure that the attribute is only used on types that are optimized
 
+error[E0658]: use of an internal attribute
+  --> $DIR/feature-gate-rustc-attrs-1.rs:10:1
+   |
+LL | #[rustc_variance]
+   | ^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
+   = note: the `#[rustc_variance]` attribute is an internal implementation detail that will never be stable
+   = note: the `#[rustc_variance]` attribute is used for rustc unit tests
+
 error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0658`.