Tracking the old name of renamed unstable library features

compiler/rustc_attr_data_structures/src/stability.rs

@@ -132,6 +132,7 @@ pub enum StabilityLevel {
         /// fn foobar() {}
         /// ```
         implied_by: Option<Symbol>,
+        old_name: Option<Symbol>,
     },
     /// `#[stable]`
     Stable {

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -299,6 +299,7 @@ pub(crate) fn parse_unstability(
     let mut issue_num = None;
     let mut is_soft = false;
     let mut implied_by = None;
+    let mut old_name = None;
     for param in args.list()?.mixed() {
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
@@ -346,11 +347,12 @@ pub(crate) fn parse_unstability(
             Some(sym::implied_by) => {
                 insert_value_into_option_or_error(cx, &param, &mut implied_by)?
             }
+            Some(sym::old_name) => insert_value_into_option_or_error(cx, &param, &mut old_name)?,
             _ => {
                 cx.emit_err(session_diagnostics::UnknownMetaItem {
                     span: param.span(),
                     item: param.path().to_string(),
-                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
+                    expected: &["feature", "reason", "issue", "soft", "implied_by", "old_name"],
                 });
                 return None;
             }
@@ -375,6 +377,7 @@ pub(crate) fn parse_unstability(
                 issue: issue_num,
                 is_soft,
                 implied_by,
+                old_name,
             };
             Some((feature, level))
         }

compiler/rustc_middle/src/middle/mod.rs

@@ -12,7 +12,7 @@ pub mod lib_features {
     #[derive(HashStable, TyEncodable, TyDecodable)]
     pub enum FeatureStability {
         AcceptedSince(Symbol),
-        Unstable,
+        Unstable(Option<Symbol>),
     }
 
     #[derive(HashStable, Debug, Default)]

compiler/rustc_middle/src/middle/stability.rs

@@ -411,7 +411,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(Stability {
-                level: attrs::StabilityLevel::Unstable { reason, issue, is_soft, implied_by },
+                level: attrs::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
                 feature,
                 ..
             }) => {

compiler/rustc_passes/messages.ftl

@@ -748,6 +748,9 @@ passes_unknown_external_lang_item =
 passes_unknown_feature =
     unknown feature `{$feature}`
 
+passes_unknown_feature_alias =
+    feature `{$alias}` has been renamed to `{$feature}`
+
 passes_unknown_lang_item =
     definition of an unknown lang item: `{$name}`
     .label = definition of unknown lang item `{$name}`

compiler/rustc_passes/src/errors.rs

@@ -1560,6 +1560,15 @@ pub(crate) struct UnknownFeature {
     pub feature: Symbol,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_unknown_feature_alias, code = E0635)]
+pub(crate) struct RenamedFeature {
+    #[primary_span]
+    pub span: Span,
+    pub feature: Symbol,
+    pub alias: Symbol,
+}
+
 #[derive(Diagnostic)]
 #[diag(passes_implied_feature_not_exist)]
 pub(crate) struct ImpliedFeatureNotExist {

compiler/rustc_passes/src/lib_features.rs

@@ -40,7 +40,7 @@ impl<'tcx> LibFeatureCollector<'tcx> {
         };
 
         let feature_stability = match level {
-            StabilityLevel::Unstable { .. } => FeatureStability::Unstable,
+            StabilityLevel::Unstable { old_name, .. } => FeatureStability::Unstable(old_name),
             StabilityLevel::Stable { since, .. } => FeatureStability::AcceptedSince(match since {
                 StableSince::Version(v) => Symbol::intern(&v.to_string()),
                 StableSince::Current => sym::env_CFG_RELEASE,
@@ -71,15 +71,15 @@ impl<'tcx> LibFeatureCollector<'tcx> {
                     });
                 }
             }
-            (FeatureStability::AcceptedSince(_), Some((FeatureStability::Unstable, _))) => {
+            (FeatureStability::AcceptedSince(_), Some((FeatureStability::Unstable(_), _))) => {
                 self.tcx.dcx().emit_err(FeaturePreviouslyDeclared {
                     span,
                     feature,
                     declared: "stable",
                     prev_declared: "unstable",
                 });
             }
-            (FeatureStability::Unstable, Some((FeatureStability::AcceptedSince(_), _))) => {
+            (FeatureStability::Unstable(_), Some((FeatureStability::AcceptedSince(_), _))) => {
                 self.tcx.dcx().emit_err(FeaturePreviouslyDeclared {
                     span,
                     feature,
@@ -88,7 +88,7 @@ impl<'tcx> LibFeatureCollector<'tcx> {
                 });
             }
             // duplicate `unstable` feature is ok.
-            (FeatureStability::Unstable, Some((FeatureStability::Unstable, _))) => {}
+            (FeatureStability::Unstable(_), Some((FeatureStability::Unstable(_), _))) => {}
         }
     }
 }

compiler/rustc_passes/src/stability.rs

@@ -718,6 +718,7 @@ fn stability_index(tcx: TyCtxt<'_>, (): ()) -> Index {
                     issue: NonZero::new(27812),
                     is_soft: false,
                     implied_by: None,
+                    old_name: None,
                 },
                 feature: sym::rustc_private,
             };
@@ -1161,8 +1162,8 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
         defined_features: &LibFeatures,
         all_implications: &UnordMap<Symbol, Symbol>,
     ) {
-        for (feature, since) in defined_features.to_sorted_vec() {
-            if let FeatureStability::AcceptedSince(since) = since
+        for (feature, stability) in defined_features.to_sorted_vec() {
+            if let FeatureStability::AcceptedSince(since) = stability
                 && let Some(span) = remaining_lib_features.get(&feature)
             {
                 // Warn if the user has enabled an already-stable lib feature.
@@ -1181,6 +1182,12 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
             // implications from this crate.
             remaining_implications.remove(&feature);
 
+            if let FeatureStability::Unstable(Some(alias)) = stability {
+                if let Some(span) = remaining_lib_features.swap_remove(&alias) {
+                    tcx.dcx().emit_err(errors::RenamedFeature { span, feature, alias });
+                }
+            }
+
             if remaining_lib_features.is_empty() && remaining_implications.is_empty() {
                 break;
             }

compiler/rustc_resolve/src/macros.rs

@@ -974,7 +974,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     ) {
         let span = path.span;
         if let Some(stability) = &ext.stability {
-            if let StabilityLevel::Unstable { reason, issue, is_soft, implied_by } = stability.level
+            if let StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. } =
+                stability.level
             {
                 let feature = stability.feature;
 

compiler/rustc_span/src/symbol.rs

@@ -1496,6 +1496,7 @@ symbols! {
         offset_of_nested,
         offset_of_slice,
         ok_or_else,
+        old_name,
         omit_gdb_pretty_printer_section,
         on,
         on_unimplemented,

library/core/src/ops/control_flow.rs

@@ -98,7 +98,7 @@ pub enum ControlFlow<B, C = ()> {
     // is a no-op conversion in the `Try` implementation.
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<B, C> ops::Try for ControlFlow<B, C> {
     type Output = C;
     type Residual = ControlFlow<B, convert::Infallible>;
@@ -117,7 +117,7 @@ impl<B, C> ops::Try for ControlFlow<B, C> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 // Note: manually specifying the residual type instead of using the default to work around
 // https://github.com/rust-lang/rust/issues/99940
 impl<B, C> ops::FromResidual<ControlFlow<B, convert::Infallible>> for ControlFlow<B, C> {

library/core/src/ops/mod.rs

@@ -194,7 +194,7 @@ pub use self::try_trait::Residual;
 #[unstable(feature = "try_trait_v2_yeet", issue = "96374")]
 pub use self::try_trait::Yeet;
 pub(crate) use self::try_trait::{ChangeOutputType, NeverShortCircuit};
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 pub use self::try_trait::{FromResidual, Try};
 #[unstable(feature = "coerce_unsized", issue = "18598")]
 pub use self::unsize::CoerceUnsized;

library/core/src/ops/try_trait.rs

@@ -112,7 +112,7 @@ use crate::ops::ControlFlow;
 ///     R::from_output(accum)
 /// }
 /// ```
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 #[rustc_on_unimplemented(
     on(
         all(from_desugaring = "TryBlock"),
@@ -130,7 +130,7 @@ use crate::ops::ControlFlow;
 #[lang = "Try"]
 pub trait Try: FromResidual {
     /// The type of the value produced by `?` when *not* short-circuiting.
-    #[unstable(feature = "try_trait_v2", issue = "84277")]
+    #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
     type Output;
 
     /// The type of the value passed to [`FromResidual::from_residual`]
@@ -154,7 +154,7 @@ pub trait Try: FromResidual {
     /// then typically you can use `Foo<std::convert::Infallible>` as its `Residual`
     /// type: that type will have a "hole" in the correct place, and will maintain the
     /// "foo-ness" of the residual so other types need to opt-in to interconversion.
-    #[unstable(feature = "try_trait_v2", issue = "84277")]
+    #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
     type Residual;
 
     /// Constructs the type from its `Output` type.
@@ -186,7 +186,7 @@ pub trait Try: FromResidual {
     /// assert_eq!(r, Some(4));
     /// ```
     #[lang = "from_output"]
-    #[unstable(feature = "try_trait_v2", issue = "84277")]
+    #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
     fn from_output(output: Self::Output) -> Self;
 
     /// Used in `?` to decide whether the operator should produce a value
@@ -213,7 +213,7 @@ pub trait Try: FromResidual {
     /// );
     /// ```
     #[lang = "branch"]
-    #[unstable(feature = "try_trait_v2", issue = "84277")]
+    #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
     fn branch(self) -> ControlFlow<Self::Residual, Self::Output>;
 }
 
@@ -303,7 +303,7 @@ pub trait Try: FromResidual {
     ),
 )]
 #[rustc_diagnostic_item = "FromResidual"]
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 pub trait FromResidual<R = <Self as Try>::Residual> {
     /// Constructs the type from a compatible `Residual` type.
     ///
@@ -326,7 +326,7 @@ pub trait FromResidual<R = <Self as Try>::Residual> {
     /// );
     /// ```
     #[lang = "from_residual"]
-    #[unstable(feature = "try_trait_v2", issue = "84277")]
+    #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
     fn from_residual(residual: R) -> Self;
 }
 

library/core/src/option.rs

@@ -2532,7 +2532,7 @@ impl<A, V: FromIterator<A>> FromIterator<Option<A>> for Option<V> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T> ops::Try for Option<T> {
     type Output = T;
     type Residual = Option<convert::Infallible>;
@@ -2551,7 +2551,7 @@ impl<T> ops::Try for Option<T> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 // Note: manually specifying the residual type instead of using the default to work around
 // https://github.com/rust-lang/rust/issues/99940
 impl<T> ops::FromResidual<Option<convert::Infallible>> for Option<T> {

library/core/src/result.rs

@@ -2051,7 +2051,7 @@ impl<A, E, V: FromIterator<A>> FromIterator<Result<A, E>> for Result<V, E> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E> ops::Try for Result<T, E> {
     type Output = T;
     type Residual = Result<convert::Infallible, E>;
@@ -2070,7 +2070,7 @@ impl<T, E> ops::Try for Result<T, E> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Result<T, F> {
     #[inline]
     #[track_caller]

library/core/src/task/poll.rs

@@ -229,7 +229,7 @@ impl<T> From<T> for Poll<T> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E> ops::Try for Poll<Result<T, E>> {
     type Output = Poll<T>;
     type Residual = Result<convert::Infallible, E>;
@@ -249,7 +249,7 @@ impl<T, E> ops::Try for Poll<Result<T, E>> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Poll<Result<T, F>> {
     #[inline]
     fn from_residual(x: Result<convert::Infallible, E>) -> Self {
@@ -259,7 +259,7 @@ impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Pol
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E> ops::Try for Poll<Option<Result<T, E>>> {
     type Output = Poll<Option<T>>;
     type Residual = Result<convert::Infallible, E>;
@@ -280,7 +280,7 @@ impl<T, E> ops::Try for Poll<Option<Result<T, E>>> {
     }
 }
 
-#[unstable(feature = "try_trait_v2", issue = "84277")]
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>>
     for Poll<Option<Result<T, F>>>
 {

src/librustdoc/clean/types.rs

@@ -2638,7 +2638,7 @@ mod size_asserts {
     static_assert_size!(GenericParamDef, 40);
     static_assert_size!(Generics, 16);
     static_assert_size!(Item, 8);
-    static_assert_size!(ItemInner, 136);
+    static_assert_size!(ItemInner, 144);
     static_assert_size!(ItemKind, 48);
     static_assert_size!(PathSegment, 32);
     static_assert_size!(Type, 32);

tests/ui/stability-attribute/renamed_feature.rs

@@ -0,0 +1,3 @@
+#![feature(try_trait)] //~ ERROR feature `try_trait` has been renamed to `try_trait_v2` [E0635]
+
+fn main() {}

tests/ui/stability-attribute/renamed_feature.stderr

@@ -0,0 +1,9 @@
+error[E0635]: feature `try_trait` has been renamed to `try_trait_v2`
+  --> $DIR/renamed_feature.rs:1:12
+   |
+LL | #![feature(try_trait)]
+   |            ^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0635`.

tests/ui/stats/input-stats.stderr

@@ -82,10 +82,10 @@ hir-stats - Expr                      32 (NN.N%)             1
 hir-stats - Let                       32 (NN.N%)             1
 hir-stats - Semi                      32 (NN.N%)             1
 hir-stats FnDecl                   120 (NN.N%)             3            40
-hir-stats Attribute                128 (NN.N%)             4            32
 hir-stats FieldDef                 128 (NN.N%)             2            64
 hir-stats GenericArgs              144 (NN.N%)             3            48
 hir-stats Variant                  144 (NN.N%)             2            72
+hir-stats Attribute                160 (NN.N%)             4            40
 hir-stats GenericBound             256 (NN.N%)             4            64
 hir-stats - Trait                    256 (NN.N%)             4
 hir-stats Block                    288 (NN.N%)             6            48
@@ -117,5 +117,5 @@ hir-stats - Use                      352 (NN.N%)             4
 hir-stats Path                   1_040 (NN.N%)            26            40
 hir-stats PathSegment            1_776 (NN.N%)            37            48
 hir-stats ----------------------------------------------------------------
-hir-stats Total                  8_644                   172
+hir-stats Total                  8_676                   172
 hir-stats