Auto merge of rust-lang#79519 - cjgillot:noattr, r=wesleywiser

Store HIR attributes in a side table

Same idea as rust-lang#72015 but for attributes.
The objective is to reduce incr-comp invalidations due to modified attributes.
Notably, those due to modified doc comments.

Implementation:
- collect attributes during AST->HIR lowering, in `LocalDefId -> ItemLocalId -> &[Attributes]` nested tables;
- access the attributes through a `hir_owner_attrs` query;
- local refactorings to use this access;
- remove `attrs` from HIR data structures one-by-one.

Change in behaviour:
- the HIR visitor traverses all attributes at once instead of parent-by-parent;
- attribute arrays are sometimes duplicated: for statements and variant constructors;
- as a consequence, attributes are marked as used after unused-attribute lint emission to avoid duplicate lints.

~~Current bug: the lint level is not correctly applied in `std::backtrace_rs`, triggering an unused attribute warning on `#![no_std]`. I welcome suggestions.~~

clippy_lints/src/attrs.rs

@@ -276,14 +276,15 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
     }
 
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
         if is_relevant_item(cx, item) {
-            check_attrs(cx, item.span, item.ident.name, &item.attrs)
+            check_attrs(cx, item.span, item.ident.name, attrs)
         }
         match item.kind {
             ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
-                let skip_unused_imports = item.attrs.iter().any(|attr| attr.has_name(sym::macro_use));
+                let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
 
-                for attr in item.attrs {
+                for attr in attrs {
                     if in_external_macro(cx.sess(), attr.span) {
                         return;
                     }
@@ -353,13 +354,13 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
         if is_relevant_impl(cx, item) {
-            check_attrs(cx, item.span, item.ident.name, &item.attrs)
+            check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()))
         }
     }
 
     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
         if is_relevant_trait(cx, item) {
-            check_attrs(cx, item.span, item.ident.name, &item.attrs)
+            check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()))
         }
     }
 }

clippy_lints/src/cognitive_complexity.rs

@@ -76,8 +76,8 @@ impl CognitiveComplexity {
 
         if rust_cc > self.limit.limit() {
             let fn_span = match kind {
-                FnKind::ItemFn(ident, _, _, _, _) | FnKind::Method(ident, _, _, _) => ident.span,
-                FnKind::Closure(_) => {
+                FnKind::ItemFn(ident, _, _, _) | FnKind::Method(ident, _, _) => ident.span,
+                FnKind::Closure => {
                     let header_span = body_span.with_hi(decl.output.span().lo());
                     let pos = snippet_opt(cx, header_span).and_then(|snip| {
                         let low_offset = snip.find('|')?;

clippy_lints/src/derive.rs

@@ -170,7 +170,8 @@ impl<'tcx> LateLintPass<'tcx> for Derive {
         }) = item.kind
         {
             let ty = cx.tcx.type_of(item.def_id);
-            let is_automatically_derived = is_automatically_derived(&*item.attrs);
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            let is_automatically_derived = is_automatically_derived(attrs);
 
             check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
             check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);

clippy_lints/src/doc.rs

@@ -208,12 +208,14 @@ impl_lint_pass!(DocMarkdown =>
 );
 
 impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
-    fn check_crate(&mut self, cx: &LateContext<'tcx>, krate: &'tcx hir::Crate<'_>) {
-        check_attrs(cx, &self.valid_idents, &krate.item.attrs);
+    fn check_crate(&mut self, cx: &LateContext<'tcx>, _: &'tcx hir::Crate<'_>) {
+        let attrs = cx.tcx.hir().attrs(hir::CRATE_HIR_ID);
+        check_attrs(cx, &self.valid_idents, attrs);
     }
 
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
-        let headers = check_attrs(cx, &self.valid_idents, &item.attrs);
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
+        let headers = check_attrs(cx, &self.valid_idents, attrs);
         match item.kind {
             hir::ItemKind::Fn(ref sig, _, body_id) => {
                 if !(is_entrypoint_fn(cx, item.def_id.to_def_id()) || in_external_macro(cx.tcx.sess, item.span)) {
@@ -249,7 +251,8 @@ impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
     }
 
     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
-        let headers = check_attrs(cx, &self.valid_idents, &item.attrs);
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
+        let headers = check_attrs(cx, &self.valid_idents, attrs);
         if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
             if !in_external_macro(cx.tcx.sess, item.span) {
                 lint_for_missing_headers(cx, item.hir_id(), item.span, sig, headers, None, None);
@@ -258,7 +261,8 @@ impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
-        let headers = check_attrs(cx, &self.valid_idents, &item.attrs);
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
+        let headers = check_attrs(cx, &self.valid_idents, attrs);
         if self.in_trait_impl || in_external_macro(cx.tcx.sess, item.span) {
             return;
         }

clippy_lints/src/exhaustive_items.rs

@@ -73,7 +73,8 @@ impl LateLintPass<'_> for ExhaustiveItems {
         if_chain! {
             if let ItemKind::Enum(..) | ItemKind::Struct(..) = item.kind;
             if cx.access_levels.is_exported(item.hir_id());
-            if !item.attrs.iter().any(|a| a.has_name(sym::non_exhaustive));
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            if !attrs.iter().any(|a| a.has_name(sym::non_exhaustive));
             then {
                 let (lint, msg) = if let ItemKind::Struct(ref v, ..) = item.kind {
                     if v.fields().iter().any(|f| !f.vis.node.is_pub()) {

clippy_lints/src/functions.rs

@@ -251,9 +251,9 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
         hir_id: hir::HirId,
     ) {
         let unsafety = match kind {
-            intravisit::FnKind::ItemFn(_, _, hir::FnHeader { unsafety, .. }, _, _) => unsafety,
-            intravisit::FnKind::Method(_, sig, _, _) => sig.header.unsafety,
-            intravisit::FnKind::Closure(_) => return,
+            intravisit::FnKind::ItemFn(_, _, hir::FnHeader { unsafety, .. }, _) => unsafety,
+            intravisit::FnKind::Method(_, sig, _) => sig.header.unsafety,
+            intravisit::FnKind::Closure => return,
         };
 
         // don't warn for implementations, it's not their fault
@@ -267,9 +267,8 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
                         ..
                     },
                     _,
-                    _,
                 )
-                | intravisit::FnKind::ItemFn(_, _, hir::FnHeader { abi: Abi::Rust, .. }, _, _) => {
+                | intravisit::FnKind::ItemFn(_, _, hir::FnHeader { abi: Abi::Rust, .. }, _) => {
                     self.check_arg_number(cx, decl, span.with_hi(decl.output.span().hi()))
                 },
                 _ => {},
@@ -281,7 +280,8 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
     }
 
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
-        let attr = must_use_attr(&item.attrs);
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
+        let attr = must_use_attr(attrs);
         if let hir::ItemKind::Fn(ref sig, ref _generics, ref body_id) = item.kind {
             let is_public = cx.access_levels.is_exported(item.hir_id());
             let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
@@ -292,7 +292,7 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
                 check_needless_must_use(cx, &sig.decl, item.hir_id(), item.span, fn_header_span, attr);
                 return;
             }
-            if is_public && !is_proc_macro(cx.sess(), &item.attrs) && attr_by_name(&item.attrs, "no_mangle").is_none() {
+            if is_public && !is_proc_macro(cx.sess(), attrs) && attr_by_name(attrs, "no_mangle").is_none() {
                 check_must_use_candidate(
                     cx,
                     &sig.decl,
@@ -313,11 +313,12 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
             if is_public && trait_ref_of_method(cx, item.hir_id()).is_none() {
                 check_result_unit_err(cx, &sig.decl, item.span, fn_header_span);
             }
-            let attr = must_use_attr(&item.attrs);
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            let attr = must_use_attr(attrs);
             if let Some(attr) = attr {
                 check_needless_must_use(cx, &sig.decl, item.hir_id(), item.span, fn_header_span, attr);
             } else if is_public
-                && !is_proc_macro(cx.sess(), &item.attrs)
+                && !is_proc_macro(cx.sess(), attrs)
                 && trait_ref_of_method(cx, item.hir_id()).is_none()
             {
                 check_must_use_candidate(
@@ -345,15 +346,16 @@ impl<'tcx> LateLintPass<'tcx> for Functions {
                 check_result_unit_err(cx, &sig.decl, item.span, fn_header_span);
             }
 
-            let attr = must_use_attr(&item.attrs);
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            let attr = must_use_attr(attrs);
             if let Some(attr) = attr {
                 check_needless_must_use(cx, &sig.decl, item.hir_id(), item.span, fn_header_span, attr);
             }
             if let hir::TraitFn::Provided(eid) = *eid {
                 let body = cx.tcx.hir().body(eid);
                 Self::check_raw_ptr(cx, sig.header.unsafety, &sig.decl, body, item.hir_id());
 
-                if attr.is_none() && is_public && !is_proc_macro(cx.sess(), &item.attrs) {
+                if attr.is_none() && is_public && !is_proc_macro(cx.sess(), attrs) {
                     check_must_use_candidate(
                         cx,
                         &sig.decl,

clippy_lints/src/future_not_send.rs

@@ -58,7 +58,7 @@ impl<'tcx> LateLintPass<'tcx> for FutureNotSend {
         _: Span,
         hir_id: HirId,
     ) {
-        if let FnKind::Closure(_) = kind {
+        if let FnKind::Closure = kind {
             return;
         }
         let ret_ty = utils::return_ty(cx, hir_id);

clippy_lints/src/inline_fn_without_body.rs

@@ -34,7 +34,8 @@ declare_lint_pass!(InlineFnWithoutBody => [INLINE_FN_WITHOUT_BODY]);
 impl<'tcx> LateLintPass<'tcx> for InlineFnWithoutBody {
     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
         if let TraitItemKind::Fn(_, TraitFn::Required(_)) = item.kind {
-            check_attrs(cx, item.ident.name, &item.attrs);
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            check_attrs(cx, item.ident.name, attrs);
         }
     }
 }

clippy_lints/src/loops.rs

@@ -578,7 +578,7 @@ impl<'tcx> LateLintPass<'tcx> for Loops {
             // also check for empty `loop {}` statements, skipping those in #[panic_handler]
             if block.stmts.is_empty() && block.expr.is_none() && !is_in_panic_handler(cx, expr) {
                 let msg = "empty `loop {}` wastes CPU cycles";
-                let help = if is_no_std_crate(cx.tcx.hir().krate()) {
+                let help = if is_no_std_crate(cx) {
                     "you should either use `panic!()` or add a call pausing or sleeping the thread to the loop body"
                 } else {
                     "you should either use `panic!()` or add `std::thread::sleep(..);` to the loop body"

clippy_lints/src/macro_use.rs

@@ -107,8 +107,8 @@ impl<'tcx> LateLintPass<'tcx> for MacroUseImports {
         if_chain! {
             if cx.sess().opts.edition >= Edition::Edition2018;
             if let hir::ItemKind::Use(path, _kind) = &item.kind;
-            if let Some(mac_attr) = item
-                .attrs
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            if let Some(mac_attr) = attrs
                 .iter()
                 .find(|attr| attr.ident().map(|s| s.to_string()) == Some("macro_use".to_string()));
             if let Res::Def(DefKind::Mod, id) = path.res;

clippy_lints/src/main_recursion.rs

@@ -32,8 +32,8 @@ pub struct MainRecursion {
 impl_lint_pass!(MainRecursion => [MAIN_RECURSION]);
 
 impl LateLintPass<'_> for MainRecursion {
-    fn check_crate(&mut self, _: &LateContext<'_>, krate: &Crate<'_>) {
-        self.has_no_std_attr = is_no_std_crate(krate);
+    fn check_crate(&mut self, cx: &LateContext<'_>, _: &Crate<'_>) {
+        self.has_no_std_attr = is_no_std_crate(cx);
     }
 
     fn check_expr_post(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {

clippy_lints/src/matches.rs

@@ -1207,11 +1207,11 @@ fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr
         if b0 != b1;
         let if_guard = &b0_arms[0].guard;
         if if_guard.is_none() || b0_arms.len() == 1;
-        if b0_arms[0].attrs.is_empty();
+        if cx.tcx.hir().attrs(b0_arms[0].hir_id).is_empty();
         if b0_arms[1..].iter()
             .all(|arm| {
                 find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) &&
-                arm.guard.is_none() && arm.attrs.is_empty()
+                arm.guard.is_none() && cx.tcx.hir().attrs(arm.hir_id).is_empty()
             });
         then {
             // The suggestion may be incorrect, because some arms can have `cfg` attributes

clippy_lints/src/misc.rs

@@ -278,7 +278,7 @@ impl<'tcx> LateLintPass<'tcx> for MiscLints {
         span: Span,
         _: HirId,
     ) {
-        if let FnKind::Closure(_) = k {
+        if let FnKind::Closure = k {
             // Does not apply to closures
             return;
         }

clippy_lints/src/missing_const_for_fn.rs

@@ -133,7 +133,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingConstForFn {
                     return;
                 }
             },
-            FnKind::Closure(..) => return,
+            FnKind::Closure => return,
         }
 
         let mir = cx.tcx.optimized_mir(def_id);

clippy_lints/src/missing_doc.rs

@@ -127,7 +127,8 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
     }
 
     fn check_crate(&mut self, cx: &LateContext<'tcx>, krate: &'tcx hir::Crate<'_>) {
-        self.check_missing_docs_attrs(cx, &krate.item.attrs, krate.item.span, "the", "crate");
+        let attrs = cx.tcx.hir().attrs(hir::CRATE_HIR_ID);
+        self.check_missing_docs_attrs(cx, attrs, krate.item.span, "the", "crate");
     }
 
     fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
@@ -160,13 +161,15 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 
         let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
 
-        self.check_missing_docs_attrs(cx, &it.attrs, it.span, article, desc);
+        let attrs = cx.tcx.hir().attrs(it.hir_id());
+        self.check_missing_docs_attrs(cx, attrs, it.span, article, desc);
     }
 
     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, trait_item: &'tcx hir::TraitItem<'_>) {
         let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
 
-        self.check_missing_docs_attrs(cx, &trait_item.attrs, trait_item.span, article, desc);
+        let attrs = cx.tcx.hir().attrs(trait_item.hir_id());
+        self.check_missing_docs_attrs(cx, attrs, trait_item.span, article, desc);
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
@@ -181,16 +184,19 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
         }
 
         let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
-        self.check_missing_docs_attrs(cx, &impl_item.attrs, impl_item.span, article, desc);
+        let attrs = cx.tcx.hir().attrs(impl_item.hir_id());
+        self.check_missing_docs_attrs(cx, attrs, impl_item.span, article, desc);
     }
 
     fn check_struct_field(&mut self, cx: &LateContext<'tcx>, sf: &'tcx hir::StructField<'_>) {
         if !sf.is_positional() {
-            self.check_missing_docs_attrs(cx, &sf.attrs, sf.span, "a", "struct field");
+            let attrs = cx.tcx.hir().attrs(sf.hir_id);
+            self.check_missing_docs_attrs(cx, attrs, sf.span, "a", "struct field");
         }
     }
 
     fn check_variant(&mut self, cx: &LateContext<'tcx>, v: &'tcx hir::Variant<'_>) {
-        self.check_missing_docs_attrs(cx, &v.attrs, v.span, "a", "variant");
+        let attrs = cx.tcx.hir().attrs(v.id);
+        self.check_missing_docs_attrs(cx, attrs, v.span, "a", "variant");
     }
 }

clippy_lints/src/missing_inline.rs

@@ -93,7 +93,8 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
         match it.kind {
             hir::ItemKind::Fn(..) => {
                 let desc = "a function";
-                check_missing_inline_attrs(cx, &it.attrs, it.span, desc);
+                let attrs = cx.tcx.hir().attrs(it.hir_id());
+                check_missing_inline_attrs(cx, attrs, it.span, desc);
             },
             hir::ItemKind::Trait(ref _is_auto, ref _unsafe, ref _generics, ref _bounds, trait_items) => {
                 // note: we need to check if the trait is exported so we can't use
@@ -108,7 +109,8 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
                                 // an impl is not provided
                                 let desc = "a default trait method";
                                 let item = cx.tcx.hir().trait_item(tit.id);
-                                check_missing_inline_attrs(cx, &item.attrs, item.span, desc);
+                                let attrs = cx.tcx.hir().attrs(item.hir_id());
+                                check_missing_inline_attrs(cx, attrs, item.span, desc);
                             }
                         },
                     }
@@ -160,6 +162,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
             }
         }
 
-        check_missing_inline_attrs(cx, &impl_item.attrs, impl_item.span, desc);
+        let attrs = cx.tcx.hir().attrs(impl_item.hir_id());
+        check_missing_inline_attrs(cx, attrs, impl_item.span, desc);
     }
 }

clippy_lints/src/needless_borrow.rs

@@ -115,8 +115,9 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessBorrow {
         }
     }
 
-    fn check_item(&mut self, _: &LateContext<'tcx>, item: &'tcx Item<'_>) {
-        if is_automatically_derived(item.attrs) {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+        let attrs = cx.tcx.hir().attrs(item.hir_id());
+        if is_automatically_derived(attrs) {
             debug_assert!(self.derived_item.is_none());
             self.derived_item = Some(item.def_id);
         }

clippy_lints/src/needless_pass_by_value.rs

@@ -80,13 +80,14 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
         }
 
         match kind {
-            FnKind::ItemFn(.., header, _, attrs) => {
+            FnKind::ItemFn(.., header, _) => {
+                let attrs = cx.tcx.hir().attrs(hir_id);
                 if header.abi != Abi::Rust || requires_exact_signature(attrs) {
                     return;
                 }
             },
             FnKind::Method(..) => (),
-            FnKind::Closure(..) => return,
+            FnKind::Closure => return,
         }
 
         // Exclude non-inherent impls

clippy_lints/src/panic_in_result_fn.rs

@@ -43,9 +43,7 @@ impl<'tcx> LateLintPass<'tcx> for PanicInResultFn {
         span: Span,
         hir_id: hir::HirId,
     ) {
-        if !matches!(fn_kind, FnKind::Closure(_))
-            && is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym::result_type)
-        {
+        if !matches!(fn_kind, FnKind::Closure) && is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym::result_type) {
             lint_impl_body(cx, span, body);
         }
     }

clippy_lints/src/partialeq_ne_impl.rs

@@ -35,7 +35,8 @@ impl<'tcx> LateLintPass<'tcx> for PartialEqNeImpl {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
         if_chain! {
             if let ItemKind::Impl(Impl { of_trait: Some(ref trait_ref), items: impl_items, .. }) = item.kind;
-            if !is_automatically_derived(&*item.attrs);
+            let attrs = cx.tcx.hir().attrs(item.hir_id());
+            if !is_automatically_derived(attrs);
             if let Some(eq_trait) = cx.tcx.lang_items().eq_trait();
             if trait_ref.path.res.def_id() == eq_trait;
             then {