rustc_feature: Separate renamed features from removed features

Author: nik-rev

compiler/rustc_expand/src/config.rs

@@ -19,7 +19,7 @@ use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_errors::msg;
 use rustc_feature::{
     ACCEPTED_LANG_FEATURES, EnabledLangFeature, EnabledLibFeature, Features, REMOVED_LANG_FEATURES,
-    UNSTABLE_LANG_FEATURES,
+    RENAMED_LANG_FEATURES, UNSTABLE_LANG_FEATURES,
 };
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::{
@@ -33,7 +33,7 @@ use tracing::instrument;
 
 use crate::errors::{
     CrateNameInCfgAttr, CrateTypeInCfgAttr, FeatureNotAllowed, FeatureRemoved,
-    FeatureRemovedReason, InvalidCfg, RemoveExprNotSupported,
+    FeatureRemovedReason, FeatureRenamed, InvalidCfg, RemoveExprNotSupported,
 };
 
 /// A folder that strips out items that do not belong in the current configuration.
@@ -81,6 +81,26 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
                 continue;
             }
 
+            // The feature is also removed, but issue a different error message is issued
+            if let Some(f) =
+                RENAMED_LANG_FEATURES.iter().find(|f| feature_ident.name == f.feature.name)
+            {
+                let pull_note = if let Some(pull) = f.pull {
+                    format!(
+                        "; see <https://github.com/rust-lang/rust/pull/{pull}> for more information",
+                    )
+                } else {
+                    "".to_owned()
+                };
+                sess.dcx().emit_err(FeatureRenamed {
+                    span: feature_ident.span,
+                    new_name: f.new_name,
+                    renamed_rustc_version: f.feature.since,
+                    pull_note,
+                });
+                continue;
+            }
+
             // If the enabled feature is stable, record it.
             if let Some(f) = ACCEPTED_LANG_FEATURES.iter().find(|f| feature_ident.name == f.name) {
                 features.set_enabled_lang_feature(EnabledLangFeature {

compiler/rustc_expand/src/errors.rs

@@ -156,6 +156,23 @@ pub(crate) struct FeatureRemoved<'a> {
     pub pull_note: String,
 }
 
+#[derive(Diagnostic)]
+#[diag("feature was renamed", code = E0557)]
+#[note("renamed in {$renamed_rustc_version}{$pull_note}")]
+pub(crate) struct FeatureRenamed<'a> {
+    #[primary_span]
+    #[suggestion(
+        "update to the new name",
+        code = "{new_name}",
+        applicability = "machine-applicable"
+    )]
+    #[label("feature was renamed")]
+    pub span: Span,
+    pub new_name: &'a str,
+    pub renamed_rustc_version: &'a str,
+    pub pull_note: String,
+}
+
 #[derive(Subdiagnostic)]
 #[note("{$reason}")]
 pub(crate) struct FeatureRemovedReason<'a> {

compiler/rustc_feature/src/lib.rs

@@ -10,10 +10,13 @@
 //! For the purpose of future feature-tracking, once a feature gate is added,
 //! even if it is stabilized or removed, *do not remove it*. Instead, move the
 //! symbol to the `accepted` or `removed` modules respectively.
+//!
+//! If a feature is renamed, move it to the `renamed` module.
 
 mod accepted;
 mod builtin_attrs;
 mod removed;
+mod renamed;
 mod unstable;
 
 #[cfg(test)]
@@ -103,6 +106,9 @@ fn find_lang_feature_issue(feature: Symbol) -> Option<NonZero<u32>> {
     if let Some(f) = REMOVED_LANG_FEATURES.iter().find(|f| f.feature.name == feature) {
         return f.feature.issue;
     }
+    if let Some(f) = RENAMED_LANG_FEATURES.iter().find(|f| f.feature.name == feature) {
+        return f.feature.issue;
+    }
     panic!("feature `{feature}` is not declared anywhere");
 }
 
@@ -135,7 +141,18 @@ pub use builtin_attrs::{
     is_valid_for_get_attr,
 };
 pub use removed::REMOVED_LANG_FEATURES;
+pub use renamed::{RENAMED_LANG_FEATURES, RenamedFeature};
 pub use unstable::{
     DEPENDENT_FEATURES, EnabledLangFeature, EnabledLibFeature, Features, INCOMPATIBLE_FEATURES,
     TRACK_FEATURE, UNSTABLE_LANG_FEATURES,
 };
+
+macro_rules! opt_nonzero_u32 {
+    () => {
+        None
+    };
+    ($val:expr) => {
+        Some(core::num::NonZeroU32::new($val).unwrap())
+    };
+}
+pub(crate) use opt_nonzero_u32;

compiler/rustc_feature/src/removed.rs

@@ -1,26 +1,18 @@
 //! List of the removed feature gates.
 
-use std::num::{NonZero, NonZeroU32};
+use std::num::NonZero;
 
 use rustc_span::sym;
 
 use super::{Feature, to_nonzero};
+use crate::opt_nonzero_u32;
 
 pub struct RemovedFeature {
     pub feature: Feature,
     pub reason: Option<&'static str>,
     pub pull: Option<NonZero<u32>>,
 }
 
-macro_rules! opt_nonzero_u32 {
-    () => {
-        None
-    };
-    ($val:expr) => {
-        Some(NonZeroU32::new($val).unwrap())
-    };
-}
-
 macro_rules! declare_features {
     ($(
         $(#[doc = $doc:tt])* (removed, $feature:ident, $ver:expr, $issue:expr, $reason:expr $(, $pull:expr)?),
@@ -54,7 +46,6 @@ declare_features! (
 
     /// Allows using the `amdgpu-kernel` ABI.
     (removed, abi_amdgpu_kernel, "1.77.0", Some(51575), None, 120495),
-    (removed, abi_c_cmse_nonsecure_call, "1.90.0", Some(81391), Some("renamed to abi_cmse_nonsecure_call"), 142146),
     (removed, advanced_slice_patterns, "1.42.0", Some(62254),
      Some("merged into `#![feature(slice_patterns)]`"), 67712),
     (removed, allocator, "1.0.0", None, None),
@@ -74,8 +65,6 @@ declare_features! (
      Some("cannot be allowed in const eval in any meaningful way"), 73398),
     /// Allows limiting the evaluation steps of const expressions
     (removed, const_eval_limit, "1.72.0", Some(67217), Some("removed the limit entirely"), 103877),
-    /// Allows non-trivial generic constants which have to be manually propagated upwards.
-    (removed, const_evaluatable_checked, "1.56.0", Some(76560), Some("renamed to `generic_const_exprs`"), 88369),
     /// Allows the definition of `const` functions with some advanced features.
     (removed, const_fn, "1.54.0", Some(57563),
      Some("split into finer-grained feature gates"), 85109),
@@ -116,11 +105,6 @@ declare_features! (
     /// Allows using `doc(primitive)` without a future-incompat warning.
     (removed, doc_primitive, "1.58.0", Some(88070),
      Some("merged into `#![feature(rustdoc_internals)]`"), 90420),
-    /// Allows `#[doc(spotlight)]`.
-    /// The attribute was renamed to `#[doc(notable_trait)]`
-    /// and the feature to `doc_notable_trait`.
-    (removed, doc_spotlight, "1.53.0", Some(45040),
-     Some("renamed to `doc_notable_trait`"), 80965),
     /// Allows using `#[unsafe_destructor_blind_to_params]` (RFC 1238).
     (removed, dropck_parametricity, "1.38.0", Some(28498), None),
     /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn compatible[^1].
@@ -150,10 +134,6 @@ declare_features! (
     /// Allows using `#[ffi_returns_twice]` on foreign functions.
     (removed, ffi_returns_twice, "1.78.0", Some(58314),
      Some("being investigated by the ffi-unwind project group"), 120502),
-    /// Allows generators to be cloned.
-    (removed, generator_clone, "1.75.0", Some(95360), Some("renamed to `coroutine_clone`"), 116958),
-    /// Allows defining generators.
-    (removed, generators, "1.75.0", Some(43122), Some("renamed to `coroutines`"), 116958),
     /// An extension to the `generic_associated_types` feature, allowing incomplete features.
     (removed, generic_associated_types_extended, "1.85.0", Some(95451),
         Some(
@@ -199,34 +179,20 @@ declare_features! (
     (removed, negate_unsigned, "1.0.0", Some(29645), None),
     /// Allows diverging expressions to fall back to `!` rather than `()`.
     (removed, never_type_fallback, "1.93.0", Some(65992), Some("removed in favor of unconditional fallback"), 148871),
-    /// Allows `#[no_coverage]` on functions.
-    /// The feature was renamed to `coverage_attribute` and the attribute to `#[coverage(on|off)]`
-    (removed, no_coverage, "1.74.0", Some(84605), Some("renamed to `coverage_attribute`"), 114656),
     /// Allows `#[no_debug]`.
     (removed, no_debug, "1.43.0", Some(29721), Some("removed due to lack of demand"), 69667),
-    // Allows the use of `no_sanitize` attribute.
-    /// The feature was renamed to `sanitize` and the attribute to `#[sanitize(xyz = "on|off")]`
-    (removed, no_sanitize, "1.91.0", Some(39699), Some(r#"renamed to sanitize(xyz = "on|off")"#), 142681),
     /// Note: this feature was previously recorded in a separate
     /// `STABLE_REMOVED` list because it, uniquely, was once stable but was
     /// then removed. But there was no utility storing it separately, so now
     /// it's in this list.
     (removed, no_stack_check, "1.0.0", None, None, 40110),
-    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn compatible (object safe).
-    /// Renamed to `dyn_compatible_for_dispatch`.
-    (removed, object_safe_for_dispatch, "1.83.0", Some(43561),
-     Some("renamed to `dyn_compatible_for_dispatch`"), 131511),
     /// Allows using `#[omit_gdb_pretty_printer_section]`.
     (removed, omit_gdb_pretty_printer_section, "1.91.0", None, None, 144738),
     /// Allows using `#[on_unimplemented(..)]` on traits.
     /// (Moved to `rustc_attrs`.)
     (removed, on_unimplemented, "1.40.0", None, None, 65794),
     /// A way to temporarily opt out of opt-in copy. This will *never* be accepted.
     (removed, opt_out_copy, "1.0.0", None, None, 20740),
-    /// Allows features specific to OIBIT (now called auto traits).
-    /// Renamed to `auto_traits`.
-    (removed, optin_builtin_traits, "1.50.0", Some(13231),
-     Some("renamed to `auto_traits`"), 79336),
     /// Allows overlapping impls of marker traits.
     (removed, overlapping_marker_traits, "1.42.0", Some(29864),
      Some("removed in favor of `#![feature(marker_trait_attr)]`"), 68544),

compiler/rustc_feature/src/renamed.rs

@@ -0,0 +1,88 @@
+//! List of the renamed feature gates.
+
+use std::num::NonZero;
+
+use rustc_span::sym;
+
+use super::{Feature, to_nonzero};
+use crate::opt_nonzero_u32;
+
+pub struct RenamedFeature {
+    pub feature: Feature,
+    pub new_name: &'static str,
+    pub pull: Option<NonZero<u32>>,
+}
+
+macro_rules! declare_features {
+    ($(
+        $(#[doc = $doc:tt])* (renamed, $old_feature_name:ident => $new_feature_name:ident, $ver:expr, $issue:expr $(, $pull:expr)?),
+    )+) => {
+        /// Formerly unstable features that have now been renamed.
+        pub static RENAMED_LANG_FEATURES: &[RenamedFeature] = &[
+            $(RenamedFeature {
+                feature: Feature {
+                    name: sym::$old_feature_name,
+                    since: $ver,
+                    issue: to_nonzero($issue),
+                },
+                new_name: stringify!($new_feature_name),
+                pull:  opt_nonzero_u32!($($pull)?),
+            }),+
+        ];
+    };
+}
+
+#[rustfmt::skip]
+declare_features! {
+    // -------------------------------------------------------------------------
+    // feature-group-start: renamed features
+    // -------------------------------------------------------------------------
+
+    // Note that the version indicates when it got *renamed*.
+    //
+    // When moving an unstable feature here, set the version number to
+    // `CURRENT RUSTC VERSION` with ` ` replaced by `_`.
+    // (But not all features below do this properly; many indicate the
+    // version they got originally added in.)
+
+    (renamed, abi_c_cmse_nonsecure_call => abi_cmse_nonsecure_call, "1.90.0", Some(81391), 142146),
+    /// Allows non-trivial generic constants which have to be manually propagated upwards.
+    (renamed, const_evaluatable_checked => generic_const_exprs, "1.56.0", Some(76560), 88369),
+    /// Allows `#[doc(spotlight)]`.
+    /// The attribute was renamed to `#[doc(notable_trait)]`
+    /// and the feature to `doc_notable_trait`.
+    (renamed, doc_spotlight => doc_notable_trait, "1.53.0", Some(45040), 80965),
+    /// Allows generators to be cloned.
+    (renamed, generator_clone => coroutine_clone, "1.75.0", Some(95360), 116958),
+    /// Allows defining generators.
+    (renamed, generators => coroutines, "1.75.0", Some(43122), 116958),
+    /// Allows `#[no_coverage]` on functions.
+    /// The feature was renamed to `coverage_attribute` and the attribute to `#[coverage(on|off)]`
+    (renamed, no_coverage => coverage_attribute, "1.74.0", Some(84605), 114656),
+    // Allows the use of `no_sanitize` attribute.
+    /// The feature was renamed to `sanitize` and the attribute to `#[sanitize(xyz = "on|off")]`
+    (renamed, no_sanitize => sanitize, "1.91.0", Some(39699), 142681),
+    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn compatible (object safe).
+    /// Renamed to `dyn_compatible_for_dispatch`.
+    (renamed, object_safe_for_dispatch => dyn_compatible_for_dispatch, "1.83.0", Some(43561), 131511),
+    /// Allows features specific to OIBIT (now called auto traits).
+    /// Renamed to `auto_traits`.
+    (renamed, optin_builtin_traits => auto_traits, "1.50.0", Some(13231), 79336),
+
+    // -------------------------------------------------------------------------
+    // feature-group-end: renamed features
+    // -------------------------------------------------------------------------
+
+
+    // -------------------------------------------------------------------------
+    // feature-group-start: renamed library features
+    // -------------------------------------------------------------------------
+    //
+    // FIXME(#141617): we should have a better way to track removed library features, but we reuse
+    // the infrastructure here so users still get hints. The symbols used here can be remove from
+    // `symbol.rs` when that happens.
+
+    // -------------------------------------------------------------------------
+    // feature-group-end: renamed library features
+    // -------------------------------------------------------------------------
+ }