Auto merge of rust-lang#145085 - JonathanBrouwer:target_checking, r=jdonszelmann

Rework target checking for built-in attributes

This is a refactoring of target checking for built-in attributes.
This PR has the following goals:
- Only refactor the 80% of the attributes that are simple to target check. More complicated ones like `#[repr]` will be in a future PR. Tho I have written the code in such a way that this will be possible to add in the future.
- No breaking changes.
  - This part of the codebase is not very well tested though, we can do a crater run if we want to be sure.
  - I've spotted quite a few weird situations (like I don't think an impl block should be deprecated?). We can propose fixing these to  in a future PR

Fixes rust-lang#143780
Fixes rust-lang#138510

I've split it in commits and left a description on some of the commits to help review.
r? `@jdonszelmann`

Author: bors

Cargo.lock

@@ -3480,6 +3480,7 @@ dependencies = [
 name = "rustc_attr_parsing"
 version = "0.0.0"
 dependencies = [
+ "itertools",
  "rustc_abi",
  "rustc_ast",
  "rustc_ast_pretty",

compiler/rustc_ast_lowering/src/block.rs

@@ -1,5 +1,6 @@
 use rustc_ast::{Block, BlockCheckMode, Local, LocalKind, Stmt, StmtKind};
 use rustc_hir as hir;
+use rustc_hir::Target;
 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, l.span, Target::Statement);
         self.arena.alloc(hir::LetStmt { hir_id, super_, ty, pat, init, els, span, source })
     }
 

compiler/rustc_ast_lowering/src/expr.rs

@@ -7,7 +7,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{HirId, find_attr};
+use rustc_hir::{HirId, Target, find_attr};
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::errors::report_lit_error;
@@ -74,7 +74,7 @@ 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, e.span, ex.hir_id, Target::from_expr(e))
                             .into_iter()
                             .chain(old_attrs.iter().cloned());
                         let new_attrs = &*self.arena.alloc_from_iter(new_attrs);
@@ -97,7 +97,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
 
             let expr_hir_id = self.lower_node_id(e.id);
-            let attrs = self.lower_attrs(expr_hir_id, &e.attrs, e.span);
+            let attrs = self.lower_attrs(expr_hir_id, &e.attrs, e.span, Target::from_expr(e));
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
@@ -639,7 +639,7 @@ 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, arm.span, Target::Arm);
         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).
@@ -820,6 +820,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     span: unstable_span,
                 }],
                 span,
+                Target::Fn,
             );
         }
     }
@@ -1654,7 +1655,7 @@ 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, f.span, Target::ExprField);
         hir::ExprField {
             hir_id,
             ident: self.lower_ident(f.ident),
@@ -1910,7 +1911,7 @@ 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, e.span, Target::from_expr(e));
         expr
     }
 
@@ -1967,7 +1968,7 @@ 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, span, Target::Expression);
             let continue_pat = self.pat_cf_continue(unstable_span, val_pat);
             self.arm(continue_pat, val_expr)
         };
@@ -1998,7 +1999,7 @@ 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, span, Target::Expression);
 
             let break_pat = self.pat_cf_break(try_span, residual_local);
             self.arm(break_pat, ret_expr)

compiler/rustc_ast_lowering/src/item.rs

@@ -5,7 +5,7 @@ use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
-use rustc_hir::{self as hir, HirId, LifetimeSource, PredicateOrigin, find_attr};
+use rustc_hir::{self as hir, HirId, LifetimeSource, PredicateOrigin, Target, find_attr};
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
@@ -80,7 +80,7 @@ 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, DUMMY_SP, Target::Crate);
                         hir::OwnerNode::Crate(module)
                     })
                 }
@@ -136,7 +136,7 @@ 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, i.span, Target::from_ast_item(i));
         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(),
@@ -621,7 +621,8 @@ 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, i.span, Target::from_foreign_item_kind(&i.kind));
         let (ident, kind) = match &i.kind {
             ForeignItemKind::Fn(box Fn { sig, ident, generics, define_opaque, .. }) => {
                 let fdec = &sig.decl;
@@ -690,7 +691,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_variant(&mut self, item_kind: &ItemKind, 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, v.span, Target::Variant);
         hir::Variant {
             hir_id,
             def_id: self.local_def_id(v.id),
@@ -773,7 +774,7 @@ 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, f.span, Target::Field);
         hir::FieldDef {
             span: self.lower_span(f.span),
             hir_id,
@@ -792,7 +793,12 @@ 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,
+            i.span,
+            Target::from_assoc_item_kind(&i.kind, AssocCtxt::Trait),
+        );
         let trait_item_def_id = hir_id.expect_owner();
 
         let (ident, generics, kind, has_default) = match &i.kind {
@@ -1001,7 +1007,12 @@ 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,
+            i.span,
+            Target::from_assoc_item_kind(&i.kind, AssocCtxt::Impl { of_trait: is_in_trait_impl }),
+        );
 
         let (ident, (generics, kind)) = match &i.kind {
             AssocItemKind::Const(box ConstItem {
@@ -1171,7 +1182,7 @@ 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, param.span, Target::Param);
         hir::Param {
             hir_id,
             pat: self.lower_pat(&param.pat),
@@ -1851,7 +1862,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> 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, span, Target::WherePredicate);
         let kind = self.arena.alloc(match &pred.kind {
             WherePredicateKind::BoundPredicate(WhereBoundPredicate {
                 bound_generic_params,

compiler/rustc_ast_lowering/src/lib.rs

@@ -54,7 +54,7 @@ use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId};
 use rustc_hir::lints::DelayedLint;
 use rustc_hir::{
     self as hir, AngleBrackets, ConstArg, GenericArg, HirId, ItemLocalMap, LifetimeSource,
-    LifetimeSyntax, ParamName, TraitCandidate,
+    LifetimeSyntax, ParamName, Target, TraitCandidate,
 };
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::extension;
@@ -943,11 +943,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         id: HirId,
         attrs: &[Attribute],
         target_span: Span,
+        target: Target,
     ) -> &'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, self.lower_span(target_span), id, target);
 
             assert_eq!(id.owner, self.current_hir_id_owner);
             let ret = self.arena.alloc_from_iter(lowered_attrs);
@@ -972,12 +974,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         attrs: &[Attribute],
         target_span: Span,
         target_hir_id: HirId,
+        target: Target,
     ) -> Vec<hir::Attribute> {
         let l = self.span_lowerer();
         self.attribute_parser.parse_attribute_list(
             attrs,
             target_span,
             target_hir_id,
+            target,
             OmitDoc::Lower,
             |s| l.lower(s),
             |l| {
@@ -1942,7 +1946,7 @@ 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, param.span(), Target::Param);
         hir::GenericParam {
             hir_id,
             def_id: self.local_def_id(param.id),

compiler/rustc_ast_lowering/src/pat.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 use rustc_ast::*;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{self as hir, LangItem};
+use rustc_hir::{self as hir, LangItem, Target};
 use rustc_middle::span_bug;
 use rustc_span::source_map::{Spanned, respan};
 use rustc_span::{DesugaringKind, Ident, Span};
@@ -93,7 +93,7 @@ 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, f.span, Target::PatField);
 
                             hir::PatField {
                                 hir_id,

compiler/rustc_attr_parsing/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }

compiler/rustc_attr_parsing/messages.ftl

@@ -10,6 +10,12 @@ attr_parsing_empty_attribute =
     unused attribute
     .suggestion = remove this attribute
 
+attr_parsing_invalid_target = `#[{$name}]` attribute cannot be used on {$target}
+    .help = `#[{$name}]` can {$only}be applied to {$applied}
+attr_parsing_invalid_target_lint = `#[{$name}]` attribute cannot be used on {$target}
+    .warn = {-attr_parsing_previously_accepted}
+    .help = `#[{$name}]` can {$only}be applied to {$applied}
+
 attr_parsing_empty_confusables =
     expected at least one confusable name
 attr_parsing_expected_one_cfg_pattern =

compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs

@@ -2,10 +2,12 @@ use std::iter;
 
 use rustc_feature::{AttributeTemplate, template};
 use rustc_hir::attrs::AttributeKind;
+use rustc_hir::{MethodKind, Target};
 use rustc_span::{Span, Symbol, sym};
 
 use super::{CombineAttributeParser, ConvertFn};
-use crate::context::{AcceptContext, Stage};
+use crate::context::MaybeWarn::{Allow, Warn};
+use crate::context::{AcceptContext, AllowedTargets, Stage};
 use crate::parser::ArgParser;
 use crate::session_diagnostics;
 
@@ -15,6 +17,12 @@ impl<S: Stage> CombineAttributeParser<S> for AllowInternalUnstableParser {
     type Item = (Symbol, Span);
     const CONVERT: ConvertFn<Self::Item> =
         |items, span| AttributeKind::AllowInternalUnstable(items, span);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::MacroDef),
+        Allow(Target::Fn),
+        Warn(Target::Field),
+        Warn(Target::Arm),
+    ]);
     const TEMPLATE: AttributeTemplate = template!(Word, List: &["feat1, feat2, ..."]);
 
     fn extend<'c>(
@@ -32,6 +40,11 @@ impl<S: Stage> CombineAttributeParser<S> for UnstableFeatureBoundParser {
     const PATH: &'static [rustc_span::Symbol] = &[sym::unstable_feature_bound];
     type Item = (Symbol, Span);
     const CONVERT: ConvertFn<Self::Item> = |items, _| AttributeKind::UnstableFeatureBound(items);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Fn),
+        Allow(Target::Impl { of_trait: true }),
+        Allow(Target::Trait),
+    ]);
     const TEMPLATE: AttributeTemplate = template!(Word, List: &["feat1, feat2, ..."]);
 
     fn extend<'c>(
@@ -53,6 +66,13 @@ impl<S: Stage> CombineAttributeParser<S> for AllowConstFnUnstableParser {
     type Item = Symbol;
     const CONVERT: ConvertFn<Self::Item> =
         |items, first_span| AttributeKind::AllowConstFnUnstable(items, first_span);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Fn),
+        Allow(Target::Method(MethodKind::Inherent)),
+        Allow(Target::Method(MethodKind::Trait { body: false })),
+        Allow(Target::Method(MethodKind::Trait { body: true })),
+        Allow(Target::Method(MethodKind::TraitImpl)),
+    ]);
     const TEMPLATE: AttributeTemplate = template!(Word, List: &["feat1, feat2, ..."]);
 
     fn extend<'c>(

compiler/rustc_attr_parsing/src/attributes/body.rs

@@ -1,15 +1,18 @@
 //! Attributes that can be found in function body.
 
+use rustc_hir::Target;
 use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use super::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::Stage;
+use crate::context::MaybeWarn::Allow;
+use crate::context::{AllowedTargets, Stage};
 
 pub(crate) struct CoroutineParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for CoroutineParser {
     const PATH: &[Symbol] = &[sym::coroutine];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Closure)]);
     const CREATE: fn(rustc_span::Span) -> AttributeKind = |span| AttributeKind::Coroutine(span);
 }