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, 1 insertions, 1 deletions

diff --git a/src/libsyntax/parse/tests.rs b/src/libsyntax/parse/tests.rs
index 3bdb9227b4e..169eb954efa 100644
--- a/src/libsyntax/parse/tests.rs
+++ b/src/libsyntax/parse/tests.rs
@@ -246,7 +246,7 @@ let mut fflags: c_int = wb();
         let source = "/// doc comment\r\n/// line 2\r\nfn foo() {}".to_string();
         let item = parse_item_from_source_str(name_2, source, &sess)
             .unwrap().unwrap();
-        let docs = item.attrs.iter().filter(|a| a.path == sym::doc)
+        let docs = item.attrs.iter().filter(|a| a.has_name(sym::doc))
                     .map(|a| a.value_str().unwrap().to_string()).collect::<Vec<_>>();
         let b: &[_] = &["/// doc comment".to_string(), "/// line 2".to_string()];
         assert_eq!(&docs[..], b);