diff options
Diffstat (limited to 'src/libsyntax')
| -rw-r--r-- | src/libsyntax/ext/tt/macro_parser.rs | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs index fe458fa9977..3046525b714 100644 --- a/src/libsyntax/ext/tt/macro_parser.rs +++ b/src/libsyntax/ext/tt/macro_parser.rs @@ -697,9 +697,14 @@ pub fn parse( return Failure(parser.span, token::Eof); } } + // Performance hack: eof_items may share matchers via Rc with other things that we want + // to modify. Dropping eof_items now may drop these refcounts to 1, preventing an + // unnecessary implicit clone later in Rc::make_mut. + drop(eof_items); + // Another possibility is that we need to call out to parse some rust nonterminal // (black-box) parser. However, if there is not EXACTLY ONE of these, something is wrong. - else if (!bb_items.is_empty() && !next_items.is_empty()) || bb_items.len() > 1 { + if (!bb_items.is_empty() && !next_items.is_empty()) || bb_items.len() > 1 { let nts = bb_items .iter() .map(|item| match item.top_elts.get_tt(item.idx) { |