Port #[no_mangle] to new attribute parsing infrastructure

JonathanBrouwer · JonathanBrouwer · commit ae3ece2ec871 · 2025-06-21T15:57:42.000+02:00
Signed-off-by: Jonathan Brouwer &lt;jonathantbrouwer@gmail.com&gt;
diff --git a/compiler/rustc_attr_data_structures/src/attributes.rs b/compiler/rustc_attr_data_structures/src/attributes.rs
@@ -233,6 +233,8 @@ pub enum AttributeKind {
 
     /// Represents `#[rustc_macro_transparency]`.
     MacroTransparency(Transparency),
+    /// Represents `#[no_mangle]`
+    NoMangle(Span),
     /// Represents `#[optimize(size|speed)]`
     Optimize(OptimizeAttr, Span),
     /// Represents [`#[repr]`](https://doc.rust-lang.org/stable/reference/type-layout.html#representations).
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -56,3 +56,21 @@ impl<S: Stage> SingleAttributeParser<S> for ColdParser {
         Some(AttributeKind::Cold(cx.attr_span))
     }
 }
+
+pub(crate) struct NoMangleParser;
+
+impl<S: Stage> SingleAttributeParser<S> for NoMangleParser {
+    const PATH: &[rustc_span::Symbol] = &[sym::no_mangle];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepLast;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(Word);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        if !args.no_args() {
+            cx.expected_no_args(args.span().unwrap_or(cx.attr_span));
+            return None;
+        };
+
+        Some(AttributeKind::NoMangle(cx.attr_span))
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
@@ -15,7 +15,7 @@ use rustc_session::Session;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 
 use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInternalUnstableParser};
-use crate::attributes::codegen_attrs::{ColdParser, OptimizeParser};
+use crate::attributes::codegen_attrs::{ColdParser, NoMangleParser, OptimizeParser};
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -110,6 +110,7 @@ attribute_parsers!(
         Single<ConstStabilityIndirectParser>,
         Single<DeprecationParser>,
         Single<InlineParser>,
+        Single<NoMangleParser>,
         Single<OptimizeParser>,
         Single<RustcForceInlineParser>,
         Single<TransparencyParser>,
diff --git a/compiler/rustc_codegen_ssa/messages.ftl b/compiler/rustc_codegen_ssa/messages.ftl
@@ -221,6 +221,8 @@ codegen_ssa_multiple_main_functions = entry symbol `main` declared multiple time
 
 codegen_ssa_no_field = no field `{$name}`
 
+codegen_ssa_no_mangle_nameless = `#[no_mangle]` cannot be used on {$definition} as it has no name
+
 codegen_ssa_no_module_named =
     no module named `{$user_path}` (mangled: {$cgu_name}). available modules: {$cgu_names}
 
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -23,6 +23,7 @@ use rustc_span::{Ident, Span, sym};
 use rustc_target::spec::SanitizerSet;
 
 use crate::errors;
+use crate::errors::NoMangleNameless;
 use crate::target_features::{
     check_target_feature_trait_unsafe, check_tied_features, from_target_feature_attr,
 };
@@ -87,7 +88,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     let mut link_ordinal_span = None;
     let mut no_sanitize_span = None;
     let mut mixed_export_name_no_mangle_lint_state = MixedExportNameAndNoMangleState::default();
-    let mut no_mangle_span = None;
 
     for attr in attrs.iter() {
         // In some cases, attribute are only valid on functions, but it's the `check_attr`
@@ -122,6 +122,25 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 }
                 AttributeKind::Cold(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
                 AttributeKind::Align { align, .. } => codegen_fn_attrs.alignment = Some(*align),
+                AttributeKind::NoMangle(attr_span) => {
+                    if tcx.opt_item_name(did.to_def_id()).is_some() {
+                        codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
+                        mixed_export_name_no_mangle_lint_state.track_no_mangle(
+                            *attr_span,
+                            tcx.local_def_id_to_hir_id(did),
+                            attr,
+                        );
+                    } else {
+                        tcx.dcx().emit_err(NoMangleNameless {
+                            span: *attr_span,
+                            definition: format!(
+                                "{} {}",
+                                tcx.def_descr_article(did.to_def_id()),
+                                tcx.def_descr(did.to_def_id())
+                            ),
+                        });
+                    }
+                }
                 _ => {}
             }
         }
@@ -141,28 +160,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR_ZEROED
             }
             sym::naked => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED,
-            sym::no_mangle => {
-                no_mangle_span = Some(attr.span());
-                if tcx.opt_item_name(did.to_def_id()).is_some() {
-                    codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
-                    mixed_export_name_no_mangle_lint_state.track_no_mangle(
-                        attr.span(),
-                        tcx.local_def_id_to_hir_id(did),
-                        attr,
-                    );
-                } else {
-                    tcx.dcx()
-                        .struct_span_err(
-                            attr.span(),
-                            format!(
-                                "`#[no_mangle]` cannot be used on {} {} as it has no name",
-                                tcx.def_descr_article(did.to_def_id()),
-                                tcx.def_descr(did.to_def_id()),
-                            ),
-                        )
-                        .emit();
-                }
-            }
             sym::rustc_std_internal_symbol => {
                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL
             }
@@ -544,12 +541,15 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
         && codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
     {
+        let no_mangle_span =
+            find_attr!(attrs, AttributeKind::NoMangle(no_mangle_span) => *no_mangle_span)
+                .unwrap_or_default();
         let lang_item =
             lang_items::extract(attrs).map_or(None, |(name, _span)| LangItem::from_name(name));
         let mut err = tcx
             .dcx()
             .struct_span_err(
-                no_mangle_span.unwrap_or_default(),
+                no_mangle_span,
                 "`#[no_mangle]` cannot be used on internal language items",
             )
             .with_note("Rustc requires this item to have a specific mangled name.")
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -1310,3 +1310,11 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_
         diag
     }
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_no_mangle_nameless)]
+pub(crate) struct NoMangleNameless {
+    #[primary_span]
+    pub span: Span,
+    pub definition: String,
+}
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
@@ -21,6 +21,7 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::visit::{FnCtxt, FnKind};
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust::expr_to_string;
+use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{Applicability, LintDiagnostic};
 use rustc_feature::GateIssue;
 use rustc_hir as hir;
@@ -954,7 +955,7 @@ declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GEN
 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         let attrs = cx.tcx.hir_attrs(it.hir_id());
-        let check_no_mangle_on_generic_fn = |attr: &hir::Attribute,
+        let check_no_mangle_on_generic_fn = |attr_span: Span,
                                              impl_generics: Option<&hir::Generics<'_>>,
                                              generics: &hir::Generics<'_>,
                                              span| {
@@ -967,7 +968,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
                         cx.emit_span_lint(
                             NO_MANGLE_GENERIC_ITEMS,
                             span,
-                            BuiltinNoMangleGeneric { suggestion: attr.span() },
+                            BuiltinNoMangleGeneric { suggestion: attr_span },
                         );
                         break;
                     }
@@ -976,14 +977,15 @@ impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
         };
         match it.kind {
             hir::ItemKind::Fn { generics, .. } => {
-                if let Some(attr) = attr::find_by_name(attrs, sym::export_name)
-                    .or_else(|| attr::find_by_name(attrs, sym::no_mangle))
+                if let Some(attr_span) = attr::find_by_name(attrs, sym::export_name)
+                    .map(|at| at.span())
+                    .or_else(|| find_attr!(attrs, AttributeKind::NoMangle(span) => *span))
                 {
-                    check_no_mangle_on_generic_fn(attr, None, generics, it.span);
+                    check_no_mangle_on_generic_fn(attr_span, None, generics, it.span);
                 }
             }
             hir::ItemKind::Const(..) => {
-                if attr::contains_name(attrs, sym::no_mangle) {
+                if find_attr!(attrs, AttributeKind::NoMangle(..)) {
                     // account for "pub const" (#45562)
                     let start = cx
                         .tcx
@@ -1008,11 +1010,12 @@ impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
                 for it in *items {
                     if let hir::AssocItemKind::Fn { .. } = it.kind {
                         let attrs = cx.tcx.hir_attrs(it.id.hir_id());
-                        if let Some(attr) = attr::find_by_name(attrs, sym::export_name)
-                            .or_else(|| attr::find_by_name(attrs, sym::no_mangle))
+                        if let Some(attr_span) = attr::find_by_name(attrs, sym::export_name)
+                            .map(|at| at.span())
+                            .or_else(|| find_attr!(attrs, AttributeKind::NoMangle(span) => *span))
                         {
                             check_no_mangle_on_generic_fn(
-                                attr,
+                                attr_span,
                                 Some(generics),
                                 cx.tcx.hir_get_generics(it.id.owner_id.def_id).unwrap(),
                                 it.span,
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -1,5 +1,5 @@
 use rustc_abi::ExternAbi;
-use rustc_attr_data_structures::{AttributeKind, ReprAttr};
+use rustc_attr_data_structures::{AttributeKind, ReprAttr, find_attr};
 use rustc_attr_parsing::AttributeParser;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::FnKind;
@@ -396,7 +396,9 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
         match &fk {
             FnKind::Method(ident, sig, ..) => match method_context(cx, id) {
                 MethodLateContext::PlainImpl => {
-                    if sig.header.abi != ExternAbi::Rust && cx.tcx.has_attr(id, sym::no_mangle) {
+                    if sig.header.abi != ExternAbi::Rust
+                        && find_attr!(cx.tcx.get_all_attrs(id), AttributeKind::NoMangle(..))
+                    {
                         return;
                     }
                     self.check_snake_case(cx, "method", ident);
@@ -408,7 +410,9 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
             },
             FnKind::ItemFn(ident, _, header) => {
                 // Skip foreign-ABI #[no_mangle] functions (Issue #31924)
-                if header.abi != ExternAbi::Rust && cx.tcx.has_attr(id, sym::no_mangle) {
+                if header.abi != ExternAbi::Rust
+                    && find_attr!(cx.tcx.get_all_attrs(id), AttributeKind::NoMangle(..))
+                {
                     return;
                 }
                 self.check_snake_case(cx, "function", ident);
@@ -514,7 +518,7 @@ impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
         let attrs = cx.tcx.hir_attrs(it.hir_id());
         match it.kind {
             hir::ItemKind::Static(_, ident, ..)
-                if !ast::attr::contains_name(attrs, sym::no_mangle) =>
+                if !find_attr!(attrs, AttributeKind::NoMangle(..)) =>
             {
                 NonUpperCaseGlobals::check_upper_case(cx, "static variable", &ident);
             }
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
@@ -163,6 +163,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::AsPtr(attr_span)) => {
                     self.check_applied_to_fn_or_method(hir_id, *attr_span, span, target)
                 }
+                Attribute::Parsed(AttributeKind::NoMangle(attr_span)) => {
+                    self.check_no_mangle(hir_id, *attr_span, span, target)
+                }
                 Attribute::Unparsed(_) => {
                     match attr.path().as_slice() {
                         [sym::diagnostic, sym::do_not_recommend, ..] => {
@@ -250,7 +253,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::link, ..] => self.check_link(hir_id, attr, span, target),
                         [sym::link_name, ..] => self.check_link_name(hir_id, attr, span, target),
                         [sym::link_section, ..] => self.check_link_section(hir_id, attr, span, target),
-                        [sym::no_mangle, ..] => self.check_no_mangle(hir_id, attr, span, target),
                         [sym::macro_use, ..] | [sym::macro_escape, ..] => {
                             self.check_macro_use(hir_id, attr, target)
                         }
@@ -688,6 +690,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             AttributeKind::Deprecation { .. }
                             | AttributeKind::Repr { .. }
                             | AttributeKind::Align { .. }
+                            | AttributeKind::NoMangle(..)
                             | AttributeKind::Cold(..),
                         ) => {
                             continue;
@@ -1936,7 +1939,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// Checks if `#[no_mangle]` is applied to a function or static.
-    fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
+    fn check_no_mangle(&self, hir_id: HirId, attr_span: Span, span: Span, target: Target) {
         match target {
             Target::Static | Target::Fn => {}
             Target::Method(..) if self.is_impl_item(hir_id) => {}
@@ -1945,7 +1948,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             // erroneously allowed it and some crates used it accidentally, to be compatible
             // with crates depending on them, we can't throw an error here.
             Target::Field | Target::Arm | Target::MacroDef => {
-                self.inline_attr_str_error_with_macro_def(hir_id, attr.span(), "no_mangle");
+                self.inline_attr_str_error_with_macro_def(hir_id, attr_span, "no_mangle");
             }
             // FIXME: #[no_mangle] was previously allowed on non-functions/statics, this should be an error
             // The error should specify that the item that is wrong is specifically a *foreign* fn/static
@@ -1959,8 +1962,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 self.tcx.emit_node_span_lint(
                     UNUSED_ATTRIBUTES,
                     hir_id,
-                    attr.span(),
-                    errors::NoMangleForeign { span, attr_span: attr.span(), foreign_item_kind },
+                    attr_span,
+                    errors::NoMangleForeign { span, attr_span, foreign_item_kind },
                 );
             }
             _ => {
@@ -1969,7 +1972,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 self.tcx.emit_node_span_lint(
                     UNUSED_ATTRIBUTES,
                     hir_id,
-                    attr.span(),
+                    attr_span,
                     errors::NoMangle { span },
                 );
             }
diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
@@ -37,8 +37,8 @@ pub type FxHashMap<K, V> = HashMap<K, V>; // re-export for use in src/librustdoc
 // will instead cause conflicts. See #94591 for more. (This paragraph and the "Latest feature" line
 // are deliberately not in a doc comment, because they need not be in public docs.)
 //
-// Latest feature: Pretty printing of cold attributes changed
-pub const FORMAT_VERSION: u32 = 50;
+// Latest feature: Pretty printing of no_mangle attributes changed
+pub const FORMAT_VERSION: u32 = 51;
 
 /// The root of the emitted JSON blob.
 ///
diff --git a/src/tools/clippy/clippy_lints/src/functions/must_use.rs b/src/tools/clippy/clippy_lints/src/functions/must_use.rs
@@ -15,6 +15,7 @@ use clippy_utils::ty::is_must_use_ty;
 use clippy_utils::visitors::for_each_expr_without_closures;
 use clippy_utils::{return_ty, trait_ref_of_method};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
+use rustc_attr_data_structures::{AttributeKind, find_attr};
 
 use core::ops::ControlFlow;
 
@@ -33,7 +34,7 @@ pub(super) fn check_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>
         let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
         if let Some(attr) = attr {
             check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr, attrs, sig);
-        } else if is_public && !is_proc_macro(attrs) && !attrs.iter().any(|a| a.has_name(sym::no_mangle)) {
+        } else if is_public && !is_proc_macro(attrs) && !find_attr!(attrs, AttributeKind::NoMangle(..)) {
             check_must_use_candidate(
                 cx,
                 sig.decl,
diff --git a/src/tools/clippy/clippy_lints/src/no_mangle_with_rust_abi.rs b/src/tools/clippy/clippy_lints/src/no_mangle_with_rust_abi.rs
@@ -6,6 +6,8 @@ use rustc_hir::{Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
 use rustc_span::{BytePos, Pos};
+use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::Attribute;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -44,8 +46,7 @@ impl<'tcx> LateLintPass<'tcx> for NoMangleWithRustAbi {
             let mut app = Applicability::MaybeIncorrect;
             let fn_snippet = snippet_with_applicability(cx, fn_sig.span.with_hi(ident.span.lo()), "..", &mut app);
             for attr in attrs {
-                if let Some(ident) = attr.ident()
-                    && ident.name == rustc_span::sym::no_mangle
+                if let Attribute::Parsed(AttributeKind::NoMangle(attr_span)) = attr
                     && fn_sig.header.abi == ExternAbi::Rust
                     && let Some((fn_attrs, _)) = fn_snippet.rsplit_once("fn")
                     && !fn_attrs.contains("extern")
@@ -54,7 +55,7 @@ impl<'tcx> LateLintPass<'tcx> for NoMangleWithRustAbi {
                         .span
                         .with_lo(fn_sig.span.lo() + BytePos::from_usize(fn_attrs.len()))
                         .shrink_to_lo();
-                    let attr_snippet = snippet(cx, attr.span(), "..");
+                    let attr_snippet = snippet(cx, *attr_span, "..");
 
                     span_lint_and_then(
                         cx,
diff --git a/tests/rustdoc-json/attrs/no_mangle_2021.rs b/tests/rustdoc-json/attrs/no_mangle_2021.rs
@@ -1,6 +1,6 @@
 //@ edition: 2021
 #![no_std]
 
-//@ is "$.index[?(@.name=='example')].attrs" '["#[no_mangle]"]'
+//@ is "$.index[?(@.name=='example')].attrs" '["#[attr = NoMangle]"]'
 #[no_mangle]
 pub extern "C" fn example() {}
diff --git a/tests/rustdoc-json/attrs/no_mangle_2024.rs b/tests/rustdoc-json/attrs/no_mangle_2024.rs
@@ -4,6 +4,6 @@
 // The representation of `#[unsafe(no_mangle)]` in rustdoc in edition 2024
 // is still `#[no_mangle]` without the `unsafe` attribute wrapper.
 
-//@ is "$.index[?(@.name=='example')].attrs" '["#[no_mangle]"]'
+//@ is "$.index[?(@.name=='example')].attrs" '["#[attr = NoMangle]"]'
 #[unsafe(no_mangle)]
 pub extern "C" fn example() {}
diff --git a/tests/ui/lint/unused/unused-attr-duplicate.rs b/tests/ui/lint/unused/unused-attr-duplicate.rs
diff --git a/tests/ui/lint/unused/unused-attr-duplicate.stderr b/tests/ui/lint/unused/unused-attr-duplicate.stderr

Original file line number	Diff line number	Diff line change
`@@ -1310,3 +1310,11 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_`
`1310`	`1310`	`diag`
`1311`	`1311`	`}`
`1312`	`1312`	`}`
	`1313`	`+`
	`1314`	`+#[derive(Diagnostic)]`
	`1315`	`+#[diag(codegen_ssa_no_mangle_nameless)]`
	`1316`	`+pub(crate) struct NoMangleNameless {`
	`1317`	`+ #[primary_span]`
	`1318`	`+ pub span: Span,`
	`1319`	`+ pub definition: String,`
	`1320`	`+}`