Auto merge of #132027 - RalfJung:lang-feature-bool-fields, r=nnethercote

nightly feature tracking: get rid of the per-feature bool fields

The `struct Features` that tracks which features are enabled has a ton of public `bool`-typed fields that are basically caching the result of looking up the corresponding feature in `enabled_lang_features`. Having public fields with an invariant is not great, so at least they should be made private. However, it turns out caching these lookups is actually [not worth it](https://github.com/rust-lang/rust/pull/131321#issuecomment-2402068336), so this PR just entirely gets rid of these fields. (The alternative would be to make them private and have a method for each of them to expose them in a read-only way. Most of the diff of this PR would be the same in that case.)

r? `@nnethercote`

3 files changed, 12 insertions, 11 deletions

diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index a6b7291ee8f..5bd9e2fbcb9 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -11,7 +11,8 @@ use rustc_ast::{
 use rustc_attr as attr;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_feature::{
-    ACCEPTED_FEATURES, AttributeSafety, Features, REMOVED_FEATURES, UNSTABLE_FEATURES,
+    ACCEPTED_LANG_FEATURES, AttributeSafety, Features, REMOVED_LANG_FEATURES,
+    UNSTABLE_LANG_FEATURES,
 };
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_parse::validate_attr;
@@ -77,7 +78,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
             };
 
             // If the enabled feature has been removed, issue an error.
-            if let Some(f) = REMOVED_FEATURES.iter().find(|f| name == f.feature.name) {
+            if let Some(f) = REMOVED_LANG_FEATURES.iter().find(|f| name == f.feature.name) {
                 sess.dcx().emit_err(FeatureRemoved {
                     span: mi.span(),
                     reason: f.reason.map(|reason| FeatureRemovedReason { reason }),
@@ -86,9 +87,9 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
             }
 
             // If the enabled feature is stable, record it.
-            if let Some(f) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
+            if let Some(f) = ACCEPTED_LANG_FEATURES.iter().find(|f| name == f.name) {
                 let since = Some(Symbol::intern(f.since));
-                features.set_enabled_lang_feature(name, mi.span(), since, None);
+                features.set_enabled_lang_feature(name, mi.span(), since);
                 continue;
             }
 
@@ -103,7 +104,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
             }
 
             // If the enabled feature is unstable, record it.
-            if let Some(f) = UNSTABLE_FEATURES.iter().find(|f| name == f.feature.name) {
+            if UNSTABLE_LANG_FEATURES.iter().find(|f| name == f.name).is_some() {
                 // When the ICE comes from core, alloc or std (approximation of the standard
                 // library), there's a chance that the person hitting the ICE may be using
                 // -Zbuild-std or similar with an untested target. The bug is probably in the
@@ -114,7 +115,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
                 {
                     sess.using_internal_features.store(true, std::sync::atomic::Ordering::Relaxed);
                 }
-                features.set_enabled_lang_feature(name, mi.span(), None, Some(f));
+                features.set_enabled_lang_feature(name, mi.span(), None);
                 continue;
             }
 
@@ -395,7 +396,7 @@ impl<'a> StripUnconfigured<'a> {
     /// If attributes are not allowed on expressions, emit an error for `attr`
     #[instrument(level = "trace", skip(self))]
     pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
-        if self.features.is_some_and(|features| !features.stmt_expr_attributes)
+        if self.features.is_some_and(|features| !features.stmt_expr_attributes())
             && !attr.span.allows_unstable(sym::stmt_expr_attributes)
         {
             let mut err = feature_err(
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index a872b12e744..5ffafcaa542 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -867,7 +867,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             | Annotatable::FieldDef(..)
             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
         };
-        if self.cx.ecfg.features.proc_macro_hygiene {
+        if self.cx.ecfg.features.proc_macro_hygiene() {
             return;
         }
         feature_err(
@@ -905,7 +905,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             }
         }
 
-        if !self.cx.ecfg.features.proc_macro_hygiene {
+        if !self.cx.ecfg.features.proc_macro_hygiene() {
             annotatable.visit_with(&mut GateProcMacroInput { sess: &self.cx.sess });
         }
     }
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs
index e518b27e419..1345f06d5ac 100644
--- a/compiler/rustc_expand/src/mbe/quoted.rs
+++ b/compiler/rustc_expand/src/mbe/quoted.rs
@@ -121,14 +121,14 @@ pub(super) fn parse(
 
 /// Asks for the `macro_metavar_expr` feature if it is not enabled
 fn maybe_emit_macro_metavar_expr_feature(features: &Features, sess: &Session, span: Span) {
-    if !features.macro_metavar_expr {
+    if !features.macro_metavar_expr() {
         let msg = "meta-variable expressions are unstable";
         feature_err(sess, sym::macro_metavar_expr, span, msg).emit();
     }
 }
 
 fn maybe_emit_macro_metavar_expr_concat_feature(features: &Features, sess: &Session, span: Span) {
-    if !features.macro_metavar_expr_concat {
+    if !features.macro_metavar_expr_concat() {
         let msg = "the `concat` meta-variable expression is unstable";
         feature_err(sess, sym::macro_metavar_expr_concat, span, msg).emit();
     }