Rollup merge of #63674 - petrochenkov:meta2, r=Centril

syntax: Support modern attribute syntax in the `meta` matcher

Where "modern" means https://github.com/rust-lang/rust/pull/57367:
```
PATH
PATH `(` TOKEN_STREAM `)`
PATH `[` TOKEN_STREAM `]`
PATH `{` TOKEN_STREAM `}`
```

Unfortunately, `meta` wasn't future-proofed using the `FOLLOW` token set like other matchers (https://github.com/rust-lang/rust/issues/34011), so code like `$meta:meta {` or `$meta:meta [` may break, and we need a crater run to find out how often this happens in practice.

Closes https://github.com/rust-lang/rust/issues/49629 (by fully supporting `meta` rather than removing it.)

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libsyntax/parse/parser/path.rs b/src/libsyntax/parse/parser/path.rs
index 463ae9124ca..ca823991a2e 100644
--- a/src/libsyntax/parse/parser/path.rs
+++ b/src/libsyntax/parse/parser/path.rs
@@ -114,9 +114,9 @@ impl<'a> Parser<'a> {
     pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, Path> {
         let meta_ident = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
-                token::NtMeta(ref meta) => match meta.kind {
-                    ast::MetaItemKind::Word => Some(meta.path.clone()),
-                    _ => None,
+                token::NtMeta(ref item) => match item.tokens.is_empty() {
+                    true => Some(item.path.clone()),
+                    false => None,
                 },
                 _ => None,
             },