Auto merge of #95562 - lcnr:attr-no-encode, r=davidtwco

don't encode only locally used attrs

Part of https://github.com/rust-lang/compiler-team/issues/505.

We now filter builtin attributes before encoding them in the crate metadata in case they should only be used in the local crate. To prevent accidental misuse `get_attrs` now requires the caller to state which attribute they are interested in. For places where that isn't trivially possible, I've added a method `fn get_attrs_unchecked` which I intend to remove in a followup PR.

After this pull request landed, we can then slowly move all attributes to only be used in the local crate while being certain that we don't accidentally try to access them from extern crates.

cc https://github.com/rust-lang/rust/pull/94963#issuecomment-1082924289

5 files changed, 27 insertions, 23 deletions

diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 261eb39bf72..9a579cb5311 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -22,7 +22,7 @@ use crate::clean::{
 use crate::core::DocContext;
 use crate::formats::item_type::ItemType;
 
-type Attrs<'hir> = rustc_middle::ty::Attributes<'hir>;
+type Attrs<'hir> = &'hir [ast::Attribute];
 
 /// Attempt to inline a definition into this AST.
 ///
@@ -155,7 +155,7 @@ crate fn try_inline_glob(
 }
 
 crate fn load_attrs<'hir>(cx: &DocContext<'hir>, did: DefId) -> Attrs<'hir> {
-    cx.tcx.get_attrs(did)
+    cx.tcx.get_attrs_unchecked(did)
 }
 
 /// Record an external fully qualified name in the external_paths cache.
@@ -691,7 +691,7 @@ crate fn record_extern_trait(cx: &mut DocContext<'_>, did: DefId) {
 
     let trait_ = clean::TraitWithExtraInfo {
         trait_,
-        is_notable: clean::utils::has_doc_flag(cx.tcx.get_attrs(did), sym::notable_trait),
+        is_notable: clean::utils::has_doc_flag(cx.tcx, did, sym::notable_trait),
     };
     cx.external_traits.borrow_mut().insert(did, trait_);
     cx.active_extern_traits.remove(&did);
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 2b65b8f910c..456d860f125 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -211,8 +211,8 @@ impl ExternalCrate {
         // Failing that, see if there's an attribute specifying where to find this
         // external crate
         let did = self.crate_num.as_def_id();
-        tcx.get_attrs(did)
-            .lists(sym::doc)
+        tcx.get_attrs(did, sym::doc)
+            .flat_map(|attr| attr.meta_item_list().unwrap_or_default())
             .filter(|a| a.has_name(sym::html_root_url))
             .filter_map(|a| a.value_str())
             .map(to_remote)
@@ -226,11 +226,13 @@ impl ExternalCrate {
 
         let as_keyword = |res: Res<!>| {
             if let Res::Def(DefKind::Mod, def_id) = res {
-                let attrs = tcx.get_attrs(def_id);
                 let mut keyword = None;
-                for attr in attrs.lists(sym::doc) {
-                    if attr.has_name(sym::keyword) {
-                        if let Some(v) = attr.value_str() {
+                let meta_items = tcx
+                    .get_attrs(def_id, sym::doc)
+                    .flat_map(|attr| attr.meta_item_list().unwrap_or_default());
+                for meta in meta_items {
+                    if meta.has_name(sym::keyword) {
+                        if let Some(v) = meta.value_str() {
                             keyword = Some(v);
                             break;
                         }
@@ -288,11 +290,13 @@ impl ExternalCrate {
         // rendering by delegating everything to a hash map.
         let as_primitive = |res: Res<!>| {
             if let Res::Def(DefKind::Mod, def_id) = res {
-                let attrs = tcx.get_attrs(def_id);
                 let mut prim = None;
-                for attr in attrs.lists(sym::doc) {
-                    if let Some(v) = attr.value_str() {
-                        if attr.has_name(sym::primitive) {
+                let meta_items = tcx
+                    .get_attrs(def_id, sym::doc)
+                    .flat_map(|attr| attr.meta_item_list().unwrap_or_default());
+                for meta in meta_items {
+                    if let Some(v) = meta.value_str() {
+                        if meta.has_name(sym::primitive) {
                             prim = PrimitiveType::from_symbol(v);
                             if prim.is_some() {
                                 break;
@@ -413,7 +417,10 @@ impl Item {
     }
 
     crate fn inner_docs(&self, tcx: TyCtxt<'_>) -> bool {
-        self.item_id.as_def_id().map(|did| tcx.get_attrs(did).inner_docs()).unwrap_or(false)
+        self.item_id
+            .as_def_id()
+            .map(|did| tcx.get_attrs_unchecked(did).inner_docs())
+            .unwrap_or(false)
     }
 
     crate fn span(&self, tcx: TyCtxt<'_>) -> Span {
@@ -464,7 +471,7 @@ impl Item {
         kind: ItemKind,
         cx: &mut DocContext<'_>,
     ) -> Item {
-        let ast_attrs = cx.tcx.get_attrs(def_id);
+        let ast_attrs = cx.tcx.get_attrs_unchecked(def_id);
 
         Self::from_def_id_and_attrs_and_parts(
             def_id,
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 3a2f24d719c..c67b92df643 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -474,10 +474,9 @@ crate fn find_nearest_parent_module(tcx: TyCtxt<'_>, def_id: DefId) -> Option<De
 ///
 /// This function exists because it runs on `hir::Attributes` whereas the other is a
 /// `clean::Attributes` method.
-crate fn has_doc_flag(attrs: ty::Attributes<'_>, flag: Symbol) -> bool {
-    attrs.iter().any(|attr| {
-        attr.has_name(sym::doc)
-            && attr.meta_item_list().map_or(false, |l| rustc_attr::list_contains_name(&l, flag))
+crate fn has_doc_flag(tcx: TyCtxt<'_>, did: DefId, flag: Symbol) -> bool {
+    tcx.get_attrs(did, sym::doc).any(|attr| {
+        attr.meta_item_list().map_or(false, |l| rustc_attr::list_contains_name(&l, flag))
     })
 }
 
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index fbb3d3e4584..4951cd83af2 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -323,7 +323,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
 
             clean::ImportItem(ref import) => {
                 let (stab, stab_tags) = if let Some(import_def_id) = import.source.did {
-                    let ast_attrs = cx.tcx().get_attrs(import_def_id);
+                    let ast_attrs = cx.tcx().get_attrs_unchecked(import_def_id);
                     let import_attrs = Box::new(clean::Attributes::from_ast(ast_attrs, None));
 
                     // Just need an item with the correct def_id and attrs
diff --git a/src/librustdoc/passes/collect_trait_impls.rs b/src/librustdoc/passes/collect_trait_impls.rs
index d245c3750ec..3b7ca7dc3c5 100644
--- a/src/librustdoc/passes/collect_trait_impls.rs
+++ b/src/librustdoc/passes/collect_trait_impls.rs
@@ -53,9 +53,7 @@ crate fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate
             while let Some(did) = parent {
                 attr_buf.extend(
                     cx.tcx
-                        .get_attrs(did)
-                        .iter()
-                        .filter(|attr| attr.has_name(sym::doc))
+                        .get_attrs(did, sym::doc)
                         .filter(|attr| {
                             if let Some([attr]) = attr.meta_item_list().as_deref() {
                                 attr.has_name(sym::cfg)