Simplify attribute_groups

compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs

@@ -10,29 +10,29 @@ use crate::session_diagnostics;
 
 pub(crate) struct AllowInternalUnstableParser;
 impl CombineAttributeParser for AllowInternalUnstableParser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::allow_internal_unstable];
+    const PATH: Symbol = sym::allow_internal_unstable;
     type Item = (Symbol, Span);
     const CONVERT: ConvertFn<Self::Item> = AttributeKind::AllowInternalUnstable;
 
     fn extend<'a>(
         cx: &'a AcceptContext<'a>,
         args: &'a ArgParser<'a>,
     ) -> impl IntoIterator<Item = Self::Item> + 'a {
-        parse_unstable(cx, args, Self::PATH[0]).into_iter().zip(iter::repeat(cx.attr_span))
+        parse_unstable(cx, args, Self::PATH).into_iter().zip(iter::repeat(cx.attr_span))
     }
 }
 
 pub(crate) struct AllowConstFnUnstableParser;
 impl CombineAttributeParser for AllowConstFnUnstableParser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::rustc_allow_const_fn_unstable];
+    const PATH: Symbol = sym::rustc_allow_const_fn_unstable;
     type Item = Symbol;
     const CONVERT: ConvertFn<Self::Item> = AttributeKind::AllowConstFnUnstable;
 
     fn extend<'a>(
         cx: &'a AcceptContext<'a>,
         args: &'a ArgParser<'a>,
     ) -> impl IntoIterator<Item = Self::Item> + 'a {
-        parse_unstable(cx, args, Self::PATH[0])
+        parse_unstable(cx, args, Self::PATH)
     }
 }
 

compiler/rustc_attr_parsing/src/attributes/confusables.rs

@@ -13,7 +13,7 @@ pub(crate) struct ConfusablesParser {
 }
 
 impl AttributeParser for ConfusablesParser {
-    const ATTRIBUTES: AcceptMapping<Self> = &[(&[sym::rustc_confusables], |this, cx, args| {
+    const ATTRIBUTES: AcceptMapping<Self> = &[(sym::rustc_confusables, |this, cx, args| {
         let Some(list) = args.list() else {
             // FIXME(jdonszelmann): error when not a list? Bring validation code here.
             //       NOTE: currently subsequent attributes are silently ignored using

compiler/rustc_attr_parsing/src/attributes/deprecation.rs

@@ -46,9 +46,9 @@ fn get(
 }
 
 impl SingleAttributeParser for DeprecationParser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::deprecated];
+    const PATH: Symbol = sym::deprecated;
 
-    fn on_duplicate(cx: &AcceptContext<'_>, first_span: rustc_span::Span) {
+    fn on_duplicate(cx: &AcceptContext<'_>, first_span: Span) {
         // FIXME(jdonszelmann): merge with errors from check_attrs.rs
         cx.emit_err(session_diagnostics::UnusedMultiple {
             this: cx.attr_span,

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -17,7 +17,7 @@
 use std::marker::PhantomData;
 
 use rustc_attr_data_structures::AttributeKind;
-use rustc_span::Span;
+use rustc_span::{Span, Symbol};
 use thin_vec::ThinVec;
 
 use crate::context::{AcceptContext, FinalizeContext};
@@ -33,7 +33,7 @@ pub(crate) mod transparency;
 pub(crate) mod util;
 
 type AcceptFn<T> = fn(&mut T, &AcceptContext<'_>, &ArgParser<'_>);
-type AcceptMapping<T> = &'static [(&'static [rustc_span::Symbol], AcceptFn<T>)];
+type AcceptMapping<T> = &'static [(Symbol, AcceptFn<T>)];
 
 /// An [`AttributeParser`] is a type which searches for syntactic attributes.
 ///
@@ -72,7 +72,7 @@ pub(crate) trait AttributeParser: Default + 'static {
 /// [`SingleAttributeParser`] can only convert attributes one-to-one, and cannot combine multiple
 /// attributes together like is necessary for `#[stable()]` and `#[unstable()]` for example.
 pub(crate) trait SingleAttributeParser: 'static {
-    const PATH: &'static [rustc_span::Symbol];
+    const PATH: Symbol;
 
     /// Caled when a duplicate attribute is found.
     ///
@@ -119,7 +119,7 @@ type ConvertFn<E> = fn(ThinVec<E>) -> AttributeKind;
 /// [`CombineAttributeParser`] can only convert a single kind of attribute, and cannot combine multiple
 /// attributes together like is necessary for `#[stable()]` and `#[unstable()]` for example.
 pub(crate) trait CombineAttributeParser: 'static {
-    const PATH: &'static [rustc_span::Symbol];
+    const PATH: Symbol;
 
     type Item;
     const CONVERT: ConvertFn<Self::Item>;

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -21,7 +21,7 @@ pub(crate) struct ReprParser;
 
 impl CombineAttributeParser for ReprParser {
     type Item = (ReprAttr, Span);
-    const PATH: &'static [rustc_span::Symbol] = &[sym::repr];
+    const PATH: Symbol = sym::repr;
     const CONVERT: ConvertFn<Self::Item> = AttributeKind::Repr;
 
     fn extend<'a>(

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -43,23 +43,23 @@ impl StabilityParser {
 
 impl AttributeParser for StabilityParser {
     const ATTRIBUTES: AcceptMapping<Self> = &[
-        (&[sym::stable], |this, cx, args| {
+        (sym::stable, |this, cx, args| {
             reject_outside_std!(cx);
             if !this.check_duplicate(cx)
                 && let Some((feature, level)) = parse_stability(cx, args)
             {
                 this.stability = Some((Stability { level, feature }, cx.attr_span));
             }
         }),
-        (&[sym::unstable], |this, cx, args| {
+        (sym::unstable, |this, cx, args| {
             reject_outside_std!(cx);
             if !this.check_duplicate(cx)
                 && let Some((feature, level)) = parse_unstability(cx, args)
             {
                 this.stability = Some((Stability { level, feature }, cx.attr_span));
             }
         }),
-        (&[sym::rustc_allowed_through_unstable_modules], |this, cx, args| {
+        (sym::rustc_allowed_through_unstable_modules, |this, cx, args| {
             reject_outside_std!(cx);
             this.allowed_through_unstable_modules = args.name_value().and_then(|i| i.value_as_str())
         }),
@@ -97,7 +97,7 @@ pub(crate) struct BodyStabilityParser {
 
 impl AttributeParser for BodyStabilityParser {
     const ATTRIBUTES: AcceptMapping<Self> =
-        &[(&[sym::rustc_default_body_unstable], |this, cx, args| {
+        &[(sym::rustc_default_body_unstable, |this, cx, args| {
             reject_outside_std!(cx);
             if this.stability.is_some() {
                 cx.dcx()
@@ -117,7 +117,7 @@ impl AttributeParser for BodyStabilityParser {
 pub(crate) struct ConstStabilityIndirectParser;
 // FIXME(jdonszelmann): single word attribute group when we have these
 impl SingleAttributeParser for ConstStabilityIndirectParser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::rustc_const_stable_indirect];
+    const PATH: Symbol = sym::rustc_const_stable_indirect;
 
     // ignore
     fn on_duplicate(_cx: &AcceptContext<'_>, _first_span: Span) {}
@@ -147,7 +147,7 @@ impl ConstStabilityParser {
 
 impl AttributeParser for ConstStabilityParser {
     const ATTRIBUTES: AcceptMapping<Self> = &[
-        (&[sym::rustc_const_stable], |this, cx, args| {
+        (sym::rustc_const_stable, |this, cx, args| {
             reject_outside_std!(cx);
 
             if !this.check_duplicate(cx)
@@ -159,7 +159,7 @@ impl AttributeParser for ConstStabilityParser {
                 ));
             }
         }),
-        (&[sym::rustc_const_unstable], |this, cx, args| {
+        (sym::rustc_const_unstable, |this, cx, args| {
             reject_outside_std!(cx);
             if !this.check_duplicate(cx)
                 && let Some((feature, level)) = parse_unstability(cx, args)
@@ -170,7 +170,7 @@ impl AttributeParser for ConstStabilityParser {
                 ));
             }
         }),
-        (&[sym::rustc_promotable], |this, cx, _| {
+        (sym::rustc_promotable, |this, cx, _| {
             reject_outside_std!(cx);
             this.promotable = true;
         }),

compiler/rustc_attr_parsing/src/attributes/transparency.rs

@@ -1,6 +1,6 @@
 use rustc_attr_data_structures::AttributeKind;
 use rustc_span::hygiene::Transparency;
-use rustc_span::sym;
+use rustc_span::{Span, Symbol, sym};
 
 use super::{AcceptContext, SingleAttributeParser};
 use crate::parser::ArgParser;
@@ -11,9 +11,9 @@ pub(crate) struct TransparencyParser;
 #[allow(rustc::untranslatable_diagnostic)]
 #[allow(rustc::diagnostic_outside_of_impl)]
 impl SingleAttributeParser for TransparencyParser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::rustc_macro_transparency];
+    const PATH: Symbol = sym::rustc_macro_transparency;
 
-    fn on_duplicate(cx: &crate::context::AcceptContext<'_>, first_span: rustc_span::Span) {
+    fn on_duplicate(cx: &crate::context::AcceptContext<'_>, first_span: Span) {
         cx.dcx().span_err(vec![first_span, cx.attr_span], "multiple macro transparency attributes");
     }
 

compiler/rustc_attr_parsing/src/context.rs

@@ -26,24 +26,29 @@ macro_rules! attribute_groups {
     (
         pub(crate) static $name: ident = [$($names: ty),* $(,)?];
     ) => {
-        pub(crate) static $name: LazyLock<(
-            BTreeMap<&'static [Symbol], Vec<Box<dyn Fn(&AcceptContext<'_>, &ArgParser<'_>) + Send + Sync>>>,
-            Vec<Box<dyn Send + Sync + Fn(&FinalizeContext<'_>) -> Option<AttributeKind>>>
-        )> = LazyLock::new(|| {
-            let mut accepts = BTreeMap::<_, Vec<Box<dyn Fn(&AcceptContext<'_>, &ArgParser<'_>) + Send + Sync>>>::new();
-            let mut finalizes = Vec::<Box<dyn Send + Sync + Fn(&FinalizeContext<'_>) -> Option<AttributeKind>>>::new();
+        type Accepts = BTreeMap<
+            Symbol,
+            Box<dyn Send + Sync + Fn(&AcceptContext<'_>, &ArgParser<'_>)>
+        >;
+        type Finalizes = Vec<
+            Box<dyn Send + Sync + Fn(&FinalizeContext<'_>) -> Option<AttributeKind>>
+        >;
+        pub(crate) static $name: LazyLock<(Accepts, Finalizes)> = LazyLock::new(|| {
+            let mut accepts = Accepts::new();
+            let mut finalizes = Finalizes::new();
             $(
                 {
                     thread_local! {
                         static STATE_OBJECT: RefCell<$names> = RefCell::new(<$names>::default());
                     };
 
                     for (k, v) in <$names>::ATTRIBUTES {
-                        accepts.entry(*k).or_default().push(Box::new(|cx, args| {
+                        let old = accepts.insert(*k, Box::new(|cx, args| {
                             STATE_OBJECT.with_borrow_mut(|s| {
                                 v(s, cx, args)
                             })
                         }));
+                        assert!(old.is_none());
                     }
 
                     finalizes.push(Box::new(|cx| {
@@ -110,7 +115,8 @@ impl<'a> Deref for AcceptContext<'a> {
 
 /// Context given to every attribute parser during finalization.
 ///
-/// Gives [`AttributeParser`](crate::attributes::AttributeParser)s enough information to create errors, for example.
+/// Gives [`AttributeParser`](crate::attributes::AttributeParser)s enough information to create
+/// errors, for example.
 pub(crate) struct FinalizeContext<'a> {
     /// The parse context, gives access to the session and the
     /// diagnostics context.
@@ -141,10 +147,9 @@ pub struct AttributeParser<'sess> {
     sess: &'sess Session,
     features: Option<&'sess Features>,
 
-    /// *only* parse attributes with this symbol.
+    /// *Only* parse attributes with this symbol.
     ///
-    /// Used in cases where we want the lowering infrastructure for
-    /// parse just a single attribute.
+    /// Used in cases where we want the lowering infrastructure for parse just a single attribute.
     parse_only: Option<Symbol>,
 
     /// Can be used to instruct parsers to reduce the number of diagnostics it emits.
@@ -157,9 +162,9 @@ impl<'sess> AttributeParser<'sess> {
     /// One example where this is necessary, is to parse `feature` attributes themselves for
     /// example.
     ///
-    /// Try to use this as little as possible. Attributes *should* be lowered during `rustc_ast_lowering`.
-    /// Some attributes require access to features to parse, which would crash if you tried to do so
-    /// through [`parse_limited`](Self::parse_limited).
+    /// Try to use this as little as possible. Attributes *should* be lowered during
+    /// `rustc_ast_lowering`. Some attributes require access to features to parse, which would
+    /// crash if you tried to do so through [`parse_limited`](Self::parse_limited).
     ///
     /// To make sure use is limited, supply a `Symbol` you'd like to parse. Only attributes with
     /// that symbol are picked out of the list of instructions and parsed. Those are returned.
@@ -217,19 +222,18 @@ impl<'sess> AttributeParser<'sess> {
         let group_cx = FinalizeContext { cx: self, target_span };
 
         for attr in attrs {
-            // if we're only looking for a single attribute,
-            // skip all the ones we don't care about
+            // If we're only looking for a single attribute, skip all the ones we don't care about.
             if let Some(expected) = self.parse_only {
                 if !attr.has_name(expected) {
                     continue;
                 }
             }
 
-            // sometimes, for example for `#![doc = include_str!("readme.md")]`,
+            // Sometimes, for example for `#![doc = include_str!("readme.md")]`,
             // doc still contains a non-literal. You might say, when we're lowering attributes
             // that's expanded right? But no, sometimes, when parsing attributes on macros,
             // we already use the lowering logic and these are still there. So, when `omit_doc`
-            // is set we *also* want to ignore these
+            // is set we *also* want to ignore these.
             if omit_doc == OmitDoc::Skip && attr.has_name(sym::doc) {
                 continue;
             }
@@ -263,21 +267,19 @@ impl<'sess> AttributeParser<'sess> {
                     let (path, args) = parser.deconstruct();
                     let parts = path.segments().map(|i| i.name).collect::<Vec<_>>();
 
-                    if let Some(accepts) = ATTRIBUTE_MAPPING.0.get(parts.as_slice()) {
-                        for f in accepts {
-                            let cx = AcceptContext {
-                                group_cx: &group_cx,
-                                attr_span: lower_span(attr.span),
-                            };
+                    if let [part] = &parts[..]
+                        && let Some(accept) = ATTRIBUTE_MAPPING.0.get(part)
+                    {
+                        let cx =
+                            AcceptContext { group_cx: &group_cx, attr_span: lower_span(attr.span) };
 
-                            f(&cx, &args)
-                        }
+                        accept(&cx, &args)
                     } else {
-                        // if we're here, we must be compiling a tool attribute... Or someone forgot to
-                        // parse their fancy new attribute. Let's warn them in any case. If you are that
-                        // person, and you really your attribute should remain unparsed, carefully read the
-                        // documentation in this module and if you still think so you can add an exception
-                        // to this assertion.
+                        // If we're here, we must be compiling a tool attribute... Or someone
+                        // forgot to parse their fancy new attribute. Let's warn them in any case.
+                        // If you are that person, and you really think your attribute should
+                        // remain unparsed, carefully read the documentation in this module and if
+                        // you still think so you can add an exception to this assertion.
 
                         // FIXME(jdonszelmann): convert other attributes, and check with this that
                         // we caught em all