rework #[naked] attribute parser

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -237,6 +237,9 @@ pub enum AttributeKind {
     /// Represents [`#[may_dangle]`](https://std-dev-guide.rust-lang.org/tricky/may-dangle.html).
     MayDangle(Span),
 
+    /// Represents `#[naked]`
+    Naked(Span),
+
     /// Represents `#[optimize(size|speed)]`
     Optimize(OptimizeAttr, Span),
 

compiler/rustc_attr_parsing/messages.ftl

@@ -89,6 +89,10 @@ attr_parsing_missing_since =
 attr_parsing_multiple_stability_levels =
     multiple stability levels
 
+attr_parsing_naked_functions_incompatible_attribute =
+    attribute incompatible with `#[unsafe(naked)]`
+    .label = the `{$attr}` attribute is incompatible with `#[unsafe(naked)]`
+    .naked_attribute = function marked with `#[unsafe(naked)]` here
 attr_parsing_non_ident_feature =
     'feature' is not an identifier
 

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -1,10 +1,12 @@
 use rustc_attr_data_structures::{AttributeKind, OptimizeAttr};
 use rustc_feature::{AttributeTemplate, template};
-use rustc_span::sym;
+use rustc_session::parse::feature_err;
+use rustc_span::{Span, sym};
 
-use super::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::{AcceptContext, Stage};
+use super::{AcceptMapping, AttributeOrder, AttributeParser, OnDuplicate, SingleAttributeParser};
+use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::ArgParser;
+use crate::session_diagnostics::NakedFunctionIncompatibleAttribute;
 
 pub(crate) struct OptimizeParser;
 
@@ -51,8 +53,115 @@ impl<S: Stage> SingleAttributeParser<S> for ColdParser {
         if !args.no_args() {
             cx.expected_no_args(args.span().unwrap_or(cx.attr_span));
             return None;
-        };
+        }
 
         Some(AttributeKind::Cold(cx.attr_span))
     }
 }
+
+#[derive(Default)]
+pub(crate) struct NakedParser {
+    span: Option<Span>,
+}
+
+impl<S: Stage> AttributeParser<S> for NakedParser {
+    const ATTRIBUTES: AcceptMapping<Self, S> =
+        &[(&[sym::naked], template!(Word), |this, cx, args| {
+            if !args.no_args() {
+                cx.expected_no_args(args.span().unwrap_or(cx.attr_span));
+                return;
+            }
+
+            if let Some(earlier) = this.span {
+                let span = cx.attr_span;
+                cx.warn_unused_duplicate(earlier, span);
+            } else {
+                this.span = Some(cx.attr_span);
+            }
+        })];
+
+    fn finalize(self, cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
+        // FIXME(jdonszelmann): upgrade this list to *parsed* attributes
+        // once all of these have parsed forms. That'd make the check much nicer...
+        //
+        // many attributes don't make sense in combination with #[naked].
+        // Notable attributes that are incompatible with `#[naked]` are:
+        //
+        // * `#[inline]`
+        // * `#[track_caller]`
+        // * `#[test]`, `#[ignore]`, `#[should_panic]`
+        //
+        // NOTE: when making changes to this list, check that `error_codes/E0736.md` remains
+        // accurate.
+        const ALLOW_LIST: &[rustc_span::Symbol] = &[
+            // conditional compilation
+            sym::cfg_trace,
+            sym::cfg_attr_trace,
+            // testing (allowed here so better errors can be generated in `rustc_builtin_macros::test`)
+            sym::test,
+            sym::ignore,
+            sym::should_panic,
+            sym::bench,
+            // diagnostics
+            sym::allow,
+            sym::warn,
+            sym::deny,
+            sym::forbid,
+            sym::deprecated,
+            sym::must_use,
+            // abi, linking and FFI
+            sym::cold,
+            sym::export_name,
+            sym::link_section,
+            sym::linkage,
+            sym::no_mangle,
+            sym::instruction_set,
+            sym::repr,
+            sym::rustc_std_internal_symbol,
+            sym::align,
+            // obviously compatible with self
+            sym::naked,
+            // documentation
+            sym::doc,
+        ];
+
+        let span = self.span?;
+
+        // only if we found a naked attribute do we do the somewhat expensive check
+        'outer: for other_attr in cx.all_attrs {
+            for allowed_attr in ALLOW_LIST {
+                if other_attr.segments().next().is_some_and(|i| cx.tools.contains(&i.name)) {
+                    // effectively skips the error message  being emitted below
+                    // if it's a tool attribute
+                    continue 'outer;
+                }
+                if other_attr.word_is(*allowed_attr) {
+                    // effectively skips the error message  being emitted below
+                    // if its an allowed attribute
+                    continue 'outer;
+                }
+
+                if other_attr.word_is(sym::target_feature) {
+                    if !cx.features().naked_functions_target_feature() {
+                        feature_err(
+                            &cx.sess(),
+                            sym::naked_functions_target_feature,
+                            other_attr.span(),
+                            "`#[target_feature(/* ... */)]` is currently unstable on `#[naked]` functions",
+                        ).emit();
+                    }
+
+                    continue 'outer;
+                }
+            }
+
+            cx.emit_err(NakedFunctionIncompatibleAttribute {
+                span: other_attr.span(),
+                naked_span: span,
+                attr: other_attr.get_attribute_path().to_string(),
+            });
+        }
+
+        Some(AttributeKind::Naked(span))
+    }
+}

compiler/rustc_attr_parsing/src/attributes/inline.rs

@@ -45,10 +45,8 @@ impl<S: Stage> SingleAttributeParser<S> for InlineParser {
             ArgParser::NameValue(_) => {
                 let suggestions =
                     <Self as SingleAttributeParser<S>>::TEMPLATE.suggestions(false, "inline");
-                cx.emit_lint(
-                    AttributeLintKind::IllFormedAttributeInput { suggestions },
-                    cx.attr_span,
-                );
+                let span = cx.attr_span;
+                cx.emit_lint(AttributeLintKind::IllFormedAttributeInput { suggestions }, span);
                 return None;
             }
         }

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -17,7 +17,6 @@
 use std::marker::PhantomData;
 
 use rustc_attr_data_structures::AttributeKind;
-use rustc_attr_data_structures::lints::AttributeLintKind;
 use rustc_feature::AttributeTemplate;
 use rustc_span::{Span, Symbol};
 use thin_vec::ThinVec;
@@ -188,14 +187,8 @@ impl<S: Stage> OnDuplicate<S> {
         unused: Span,
     ) {
         match self {
-            OnDuplicate::Warn => cx.emit_lint(
-                AttributeLintKind::UnusedDuplicate { this: unused, other: used, warning: false },
-                unused,
-            ),
-            OnDuplicate::WarnButFutureError => cx.emit_lint(
-                AttributeLintKind::UnusedDuplicate { this: unused, other: used, warning: true },
-                unused,
-            ),
+            OnDuplicate::Warn => cx.warn_unused_duplicate(used, unused),
+            OnDuplicate::WarnButFutureError => cx.warn_unused_duplicate_future_error(used, unused),
             OnDuplicate::Error => {
                 cx.emit_err(UnusedMultiple {
                     this: used,