mejrs · mejrs · Jun 18, 2025 · Jun 20, 2025
diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
@@ -1,4 +1,5 @@
 use rustc_ast::{Block, BlockCheckMode, Local, LocalKind, Stmt, StmtKind};
+use rustc_attr_parsing::AttrTarget;
 use rustc_hir as hir;
 use rustc_span::sym;
 use smallvec::SmallVec;
@@ -109,7 +110,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         };
         let span = self.lower_span(l.span);
         let source = hir::LocalSource::Normal;
-        self.lower_attrs(hir_id, &l.attrs, l.span);
+        self.lower_attrs(hir_id, &l.attrs, AttrTarget::Todo, l.span);
         self.arena.alloc(hir::LetStmt { hir_id, super_, ty, pat, init, els, span, source })
     }
 

diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 use rustc_ast::ptr::P as AstP;
 use rustc_ast::*;
 use rustc_ast_pretty::pprust::expr_to_string;
+use rustc_attr_parsing::AttrTarget;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_hir::HirId;
@@ -74,7 +75,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     if !e.attrs.is_empty() {
                         let old_attrs = self.attrs.get(&ex.hir_id.local_id).copied().unwrap_or(&[]);
                         let new_attrs = self
-                            .lower_attrs_vec(&e.attrs, e.span, ex.hir_id)
+                            .lower_attrs_vec(&e.attrs, AttrTarget::Todo, e.span, ex.hir_id)
                             .into_iter()
                             .chain(old_attrs.iter().cloned());
                         let new_attrs = &*self.arena.alloc_from_iter(new_attrs);
@@ -97,7 +98,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
 
             let expr_hir_id = self.lower_node_id(e.id);
-            self.lower_attrs(expr_hir_id, &e.attrs, e.span);
+            self.lower_attrs(expr_hir_id, &e.attrs, AttrTarget::Todo, e.span);
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
@@ -677,7 +678,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let guard = arm.guard.as_ref().map(|cond| self.lower_expr(cond));
         let hir_id = self.next_id();
         let span = self.lower_span(arm.span);
-        self.lower_attrs(hir_id, &arm.attrs, arm.span);
+        self.lower_attrs(hir_id, &arm.attrs, AttrTarget::Todo, arm.span);
         let is_never_pattern = pat.is_never_pattern();
         // We need to lower the body even if it's unneeded for never pattern in match,
         // ensure that we can get HirId for DefId if need (issue #137708).
@@ -849,6 +850,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     style: AttrStyle::Outer,
                     span: unstable_span,
                 }],
+                AttrTarget::Todo,
                 span,
             );
         }
@@ -1690,7 +1692,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_expr_field(&mut self, f: &ExprField) -> hir::ExprField<'hir> {
         let hir_id = self.lower_node_id(f.id);
-        self.lower_attrs(hir_id, &f.attrs, f.span);
+        self.lower_attrs(hir_id, &f.attrs, AttrTarget::Todo, f.span);
         hir::ExprField {
             hir_id,
             ident: self.lower_ident(f.ident),
@@ -1946,7 +1948,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         //
         // Also, add the attributes to the outer returned expr node.
         let expr = self.expr_drop_temps_mut(for_span, match_expr);
-        self.lower_attrs(expr.hir_id, &e.attrs, e.span);
+        self.lower_attrs(expr.hir_id, &e.attrs, AttrTarget::Todo, e.span);
         expr
     }
 
@@ -2003,7 +2005,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let val_ident = Ident::with_dummy_span(sym::val);
             let (val_pat, val_pat_nid) = self.pat_ident(span, val_ident);
             let val_expr = self.expr_ident(span, val_ident, val_pat_nid);
-            self.lower_attrs(val_expr.hir_id, &attrs, span);
+            self.lower_attrs(val_expr.hir_id, &attrs, AttrTarget::Todo, span);
             let continue_pat = self.pat_cf_continue(unstable_span, val_pat);
             self.arm(continue_pat, val_expr)
         };
@@ -2034,7 +2036,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let ret_expr = self.checked_return(Some(from_residual_expr));
                 self.arena.alloc(self.expr(try_span, ret_expr))
             };
-            self.lower_attrs(ret_expr.hir_id, &attrs, span);
+            self.lower_attrs(ret_expr.hir_id, &attrs, AttrTarget::Todo, span);
 
             let break_pat = self.pat_cf_break(try_span, residual_local);
             self.arm(break_pat, ret_expr)

diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
@@ -2,6 +2,7 @@ use rustc_abi::ExternAbi;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
+use rustc_attr_parsing::AttrTarget;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
@@ -82,7 +83,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
                     self.with_lctx(CRATE_NODE_ID, |lctx| {
                         let module = lctx.lower_mod(&c.items, &c.spans);
                         // FIXME(jdonszelman): is dummy span ever a problem here?
-                        lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs, DUMMY_SP);
+                        lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs, AttrTarget::Todo, DUMMY_SP);
                         hir::OwnerNode::Crate(module)
                     })
                 }
@@ -138,7 +139,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
         let vis_span = self.lower_span(i.vis.span);
         let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
-        let attrs = self.lower_attrs(hir_id, &i.attrs, i.span);
+        let attrs = self.lower_attrs(hir_id, &i.attrs, AttrTarget::from(&i.kind), i.span);
         let kind = self.lower_item_kind(i.span, i.id, hir_id, attrs, vis_span, &i.kind);
         let item = hir::Item {
             owner_id: hir_id.expect_owner(),
@@ -641,7 +642,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
         let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         let owner_id = hir_id.expect_owner();
-        let attrs = self.lower_attrs(hir_id, &i.attrs, i.span);
+        let attrs = self.lower_attrs(hir_id, &i.attrs, AttrTarget::Todo, i.span);
         let (ident, kind) = match &i.kind {
             ForeignItemKind::Fn(box Fn { sig, ident, generics, define_opaque, .. }) => {
                 let fdec = &sig.decl;
@@ -716,7 +717,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
         let hir_id = self.lower_node_id(v.id);
-        self.lower_attrs(hir_id, &v.attrs, v.span);
+        self.lower_attrs(hir_id, &v.attrs, AttrTarget::Todo, v.span);
         hir::Variant {
             hir_id,
             def_id: self.local_def_id(v.id),
@@ -778,7 +779,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::FieldDef<'hir> {
         let ty = self.lower_ty(&f.ty, ImplTraitContext::Disallowed(ImplTraitPosition::FieldTy));
         let hir_id = self.lower_node_id(f.id);
-        self.lower_attrs(hir_id, &f.attrs, f.span);
+        self.lower_attrs(hir_id, &f.attrs, AttrTarget::Todo, f.span);
         hir::FieldDef {
             span: self.lower_span(f.span),
             hir_id,
@@ -797,7 +798,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
         let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
-        let attrs = self.lower_attrs(hir_id, &i.attrs, i.span);
+        let attrs = self.lower_attrs(hir_id, &i.attrs, AttrTarget::from((true, &i.kind)), i.span);
         let trait_item_def_id = hir_id.expect_owner();
 
         let (ident, generics, kind, has_default) = match &i.kind {
@@ -991,7 +992,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let has_value = true;
         let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
         let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
-        let attrs = self.lower_attrs(hir_id, &i.attrs, i.span);
+        let attrs = self.lower_attrs(
+            hir_id,
+            &i.attrs,
+            AttrTarget::from((is_in_trait_impl, &i.kind)),
+            i.span,
+        );
 
         let (ident, (generics, kind)) = match &i.kind {
             AssocItemKind::Const(box ConstItem {
@@ -1185,7 +1191,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
         let hir_id = self.lower_node_id(param.id);
-        self.lower_attrs(hir_id, &param.attrs, param.span);
+        self.lower_attrs(hir_id, &param.attrs, AttrTarget::Todo, param.span);
         hir::Param {
             hir_id,
             pat: self.lower_pat(&param.pat),
@@ -1894,7 +1900,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
         let hir_id = self.lower_node_id(pred.id);
         let span = self.lower_span(pred.span);
-        self.lower_attrs(hir_id, &pred.attrs, span);
+        self.lower_attrs(hir_id, &pred.attrs, AttrTarget::Todo, span);
         let kind = self.arena.alloc(match &pred.kind {
             WherePredicateKind::BoundPredicate(WhereBoundPredicate {
                 bound_generic_params,

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
@@ -42,7 +42,7 @@ use std::sync::Arc;
 
 use rustc_ast::node_id::NodeMap;
 use rustc_ast::{self as ast, *};
-use rustc_attr_parsing::{AttributeParser, OmitDoc};
+use rustc_attr_parsing::{AttrTarget, AttributeParser, OmitDoc};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -911,12 +911,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         id: HirId,
         attrs: &[Attribute],
+        target: AttrTarget<'_>,
         target_span: Span,
     ) -> &'hir [hir::Attribute] {
         if attrs.is_empty() {
             &[]
         } else {
-            let lowered_attrs = self.lower_attrs_vec(attrs, self.lower_span(target_span), id);
+            let lowered_attrs =
+                self.lower_attrs_vec(attrs, target, self.lower_span(target_span), id);
 
             assert_eq!(id.owner, self.current_hir_id_owner);
             let ret = self.arena.alloc_from_iter(lowered_attrs);
@@ -939,12 +941,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_attrs_vec(
         &mut self,
         attrs: &[Attribute],
+        target: AttrTarget<'_>,
         target_span: Span,
         target_hir_id: HirId,
     ) -> Vec<hir::Attribute> {
         let l = self.span_lowerer();
         self.attribute_parser.parse_attribute_list(
             attrs,
+            target,
             target_span,
             target_hir_id,
             OmitDoc::Lower,
@@ -1899,7 +1903,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let (name, kind) = self.lower_generic_param_kind(param, source);
 
         let hir_id = self.lower_node_id(param.id);
-        self.lower_attrs(hir_id, &param.attrs, param.span());
+        self.lower_attrs(hir_id, &param.attrs, AttrTarget::Todo, param.span());
         hir::GenericParam {
             hir_id,
             def_id: self.local_def_id(param.id),

diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
@@ -2,6 +2,7 @@ use std::sync::Arc;
 
 use rustc_ast::ptr::P;
 use rustc_ast::*;
+use rustc_attr_parsing::AttrTarget;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{self as hir, LangItem};
@@ -94,7 +95,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                         let fs = self.arena.alloc_from_iter(fields.iter().map(|f| {
                             let hir_id = self.lower_node_id(f.id);
-                            self.lower_attrs(hir_id, &f.attrs, f.span);
+                            self.lower_attrs(hir_id, &f.attrs, AttrTarget::Todo, f.span);
 
                             hir::PatField {
                                 hir_id,

diff --git a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
@@ -45,6 +45,7 @@ impl<S: Stage> SingleAttributeParser<S> for DeprecationParser {
     const PATH: &[Symbol] = &[sym::deprecated];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const POSITIONS: &[crate::TargetChecker] = &[crate::allowed!(_)];
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
         let features = cx.features();

diff --git a/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs b/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
@@ -13,6 +13,7 @@ impl<S: Stage> SingleAttributeParser<S> for AsPtrParser {
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
 
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const POSITIONS: &[crate::TargetChecker] = &[crate::allowed!(Function | Method)];
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, _args: &ArgParser<'_>) -> Option<AttributeKind> {
         // FIXME: check that there's no args (this is currently checked elsewhere)

diff --git a/compiler/rustc_attr_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -21,6 +21,7 @@ use rustc_attr_data_structures::lints::AttributeLintKind;
 use rustc_span::{Span, Symbol};
 use thin_vec::ThinVec;
 
+use crate::TargetChecker;
 use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::ArgParser;
 use crate::session_diagnostics::UnusedMultiple;
@@ -87,6 +88,7 @@ pub(crate) trait SingleAttributeParser<S: Stage>: 'static {
     const PATH: &[Symbol];
     const ATTRIBUTE_ORDER: AttributeOrder;
     const ON_DUPLICATE: OnDuplicate<S>;
+    const POSITIONS: &[TargetChecker];
 
     /// Converts a single syntactical attribute to a single semantic attribute, or [`AttributeKind`]
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind>;
@@ -106,6 +108,25 @@ impl<T: SingleAttributeParser<S>, S: Stage> Default for Single<T, S> {
 impl<T: SingleAttributeParser<S>, S: Stage> AttributeParser<S> for Single<T, S> {
     const ATTRIBUTES: AcceptMapping<Self, S> =
         &[(T::PATH, |group: &mut Single<T, S>, cx, args| {
+            let mut allowed = false;
+            for checker in T::POSITIONS {
+                for pos in checker.check {
+                    allowed |= pos(cx.target);
+                }
+            }
+
+            if !allowed {
+                let allowed_targets = crate::AttrTarget::allowed(T::POSITIONS);
+                cx.dcx().span_err(
+                    cx.attr_span,
+                    format!(
+                        "`{}` is not valid at that position. It is only allowed in {:?}",
+                        crate::attributes::util::PathPrinter(T::PATH),
+                        allowed_targets,
+                    ),
+                );
+                return;
+            }
             if let Some(pa) = T::convert(cx, args) {
                 match T::ATTRIBUTE_ORDER {
                     // keep the first and report immediately. ignore this attribute

diff --git a/compiler/rustc_attr_parsing/src/attributes/stability.rs b/compiler/rustc_attr_parsing/src/attributes/stability.rs
@@ -9,6 +9,7 @@ use rustc_span::{Span, Symbol, sym};
 
 use super::util::parse_version;
 use super::{AcceptMapping, AttributeOrder, AttributeParser, OnDuplicate, SingleAttributeParser};
+use crate::allowed;
 use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::{ArgParser, MetaItemParser};
 use crate::session_diagnostics::{self, UnsupportedLiteralReason};
@@ -120,6 +121,7 @@ impl<S: Stage> SingleAttributeParser<S> for ConstStabilityIndirectParser {
     const PATH: &[Symbol] = &[sym::rustc_const_stable_indirect];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Ignore;
+    const POSITIONS: &[crate::TargetChecker] = &[allowed!(_)];
 
     fn convert(_cx: &mut AcceptContext<'_, '_, S>, _args: &ArgParser<'_>) -> Option<AttributeKind> {
         Some(AttributeKind::ConstStabilityIndirect)

diff --git a/compiler/rustc_attr_parsing/src/attributes/transparency.rs b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
@@ -3,9 +3,9 @@ use rustc_span::hygiene::Transparency;
 use rustc_span::{Symbol, sym};
 
 use super::{AttributeOrder, OnDuplicate, SingleAttributeParser};
+use crate::allowed;
 use crate::context::{AcceptContext, Stage};
 use crate::parser::ArgParser;
-
 pub(crate) struct TransparencyParser;
 
 // FIXME(jdonszelmann): make these proper diagnostics
@@ -17,6 +17,7 @@ impl<S: Stage> SingleAttributeParser<S> for TransparencyParser {
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Custom(|cx, used, unused| {
         cx.dcx().span_err(vec![used, unused], "multiple macro transparency attributes");
     });
+    const POSITIONS: &[crate::TargetChecker] = &[allowed!(_)];
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
         match args.name_value().and_then(|nv| nv.value_as_str()) {

diff --git a/compiler/rustc_attr_parsing/src/attributes/util.rs b/compiler/rustc_attr_parsing/src/attributes/util.rs
@@ -1,3 +1,5 @@
+use std::fmt;
+
 use rustc_ast::attr::{AttributeExt, first_attr_value_str_by_name};
 use rustc_attr_data_structures::RustcVersion;
 use rustc_feature::is_builtin_attr_name;
@@ -56,3 +58,25 @@ pub fn is_doc_alias_attrs_contain_symbol<'tcx, T: AttributeExt + 'tcx>(
     }
     false
 }
+
+pub(crate) struct PathPrinter<'s>(pub &'s [Symbol]);
+
+impl fmt::Display for PathPrinter<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "#[")?;
+        match &self.0 {
+            &[] => {}
+            &[one] => {
+                write!(f, "{one}")?;
+            }
+            &[start @ .., last] => {
+                for segment in start {
+                    write!(f, "{segment}::")?;
+                }
+                write!(f, "{last}")?;
+            }
+        }
+        write!(f, "]")?;
+        Ok(())
+    }
+}