Auto merge of #65885 - Centril:rollup-y6b2qbf, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #64747 (Stabilize `Option::flatten`)
 - #65664 (`std::panic::Location` is a lang_item, add `core::intrinsics::caller_location` (RFC 2091 3/N))
 - #65792 (rustc, rustc_passes: reduce deps on rustc_expand)
 - #65849 (librustc_lexer: Enhance documentation)
 - #65873 (doc: explain why it is unsafe to construct Vec<u8> from Vec<u16>)
 - #65880 (Gather together usefulness tests)

Failed merges:

r? @ghost

2 files changed, 22 insertions, 1 deletions

diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index e6ddf8778cc..f5e416b722b 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -288,6 +288,27 @@ pub fn stream_to_parser_with_base_dir<'a>(
     Parser::new(sess, stream, Some(base_dir), true, false, None)
 }
 
+/// Runs the given subparser `f` on the tokens of the given `attr`'s item.
+pub fn parse_in_attr<'a, T>(
+    sess: &'a ParseSess,
+    attr: &ast::Attribute,
+    mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+) -> PResult<'a, T> {
+    let mut parser = Parser::new(
+        sess,
+        attr.tokens.clone(),
+        None,
+        false,
+        false,
+        Some("attribute"),
+    );
+    let result = f(&mut parser)?;
+    if parser.token != token::Eof {
+        parser.unexpected()?;
+    }
+    Ok(result)
+}
+
 // NOTE(Centril): The following probably shouldn't be here but it acknowledges the
 // fact that architecturally, we are using parsing (read on below to understand why).
 
diff --git a/src/libsyntax/parse/parser/path.rs b/src/libsyntax/parse/parser/path.rs
index 77709a22953..38a28224dab 100644
--- a/src/libsyntax/parse/parser/path.rs
+++ b/src/libsyntax/parse/parser/path.rs
@@ -130,7 +130,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse a list of paths inside `#[derive(path_0, ..., path_n)]`.
-    crate fn parse_derive_paths(&mut self) -> PResult<'a, Vec<Path>> {
+    pub fn parse_derive_paths(&mut self) -> PResult<'a, Vec<Path>> {
         self.expect(&token::OpenDelim(token::Paren))?;
         let mut list = Vec::new();
         while !self.eat(&token::CloseDelim(token::Paren)) {