Make doc comments cheaper with `AttrKind`.

`AttrKind` is a new type with two variants, `Normal` and `DocComment`. It's a
big performance win (over 10% in some cases) because `DocComment` lets doc
comments (which are common) be represented very cheaply.

`Attribute` gets some new helper methods to ease the transition:
- `has_name()`: check if the attribute name matches a single `Symbol`; for
  `DocComment` variants it succeeds if the symbol is `sym::doc`.
- `is_doc_comment()`: check if it has a `DocComment` kind.
- `{get,unwrap}_normal_item()`: extract the item from a `Normal` variant;
  panic otherwise.

Fixes #60935.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index 7592df57fc6..9408bbe557a 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -885,7 +885,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
         for attr in attrs {
             if attr.check_name(sym::doc) {
                 if let Some(val) = attr.value_str() {
-                    if attr.is_sugared_doc {
+                    if attr.is_doc_comment() {
                         result.push_str(&strip_doc_comment_decoration(&val.as_str()));
                     } else {
                         result.push_str(&val.as_str());
@@ -1195,7 +1195,7 @@ fn null_id() -> rls_data::Id {
 fn lower_attributes(attrs: Vec<Attribute>, scx: &SaveContext<'_, '_>) -> Vec<rls_data::Attribute> {
     attrs.into_iter()
     // Only retain real attributes. Doc comments are lowered separately.
-    .filter(|attr| attr.item.path != sym::doc)
+    .filter(|attr| !attr.has_name(sym::doc))
     .map(|mut attr| {
         // Remove the surrounding '#[..]' or '#![..]' of the pretty printed
         // attribute. First normalize all inner attribute (#![..]) to outer