diff options
| -rw-r--r-- | compiler/rustc_expand/src/mbe/macro_parser.rs | 129 |
1 files changed, 68 insertions, 61 deletions
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs index 04137086088..718f155c60c 100644 --- a/compiler/rustc_expand/src/mbe/macro_parser.rs +++ b/compiler/rustc_expand/src/mbe/macro_parser.rs @@ -744,70 +744,77 @@ pub(super) fn parse_tt( // unnecessary implicit clone later in `Rc::make_mut`. drop(eof_items); - // If there are no possible next positions AND we aren't waiting for the black-box parser, - // then there is a syntax error. - if bb_items.is_empty() && next_items.is_empty() { - return Failure(parser.token.clone(), "no rules expected this token in macro call"); - } + match (next_items.len(), bb_items.len()) { + (0, 0) => { + // There are no possible next positions AND we aren't waiting for the black-box + // parser: syntax error. + return Failure(parser.token.clone(), "no rules expected this token in macro call"); + } - if (!bb_items.is_empty() && !next_items.is_empty()) || bb_items.len() > 1 { - // We need to call out to parse some rust nonterminal (black-box) parser. But something - // is wrong, because there is not EXACTLY ONE of these. - let nts = bb_items - .iter() - .map(|item| match item.top_elts.get_tt(item.idx) { - TokenTree::MetaVarDecl(_, bind, Some(kind)) => format!("{} ('{}')", kind, bind), - _ => panic!(), - }) - .collect::<Vec<String>>() - .join(" or "); - - return Error( - parser.token.span, - format!( - "local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}", - match next_items.len() { - 0 => format!("built-in NTs {}.", nts), - 1 => format!("built-in NTs {} or 1 other option.", nts), - n => format!("built-in NTs {} or {} other options.", nts, n), - } - ), - ); - } + (_, 0) => { + // Dump all possible `next_items` into `cur_items` for the next iteration. Then + // process the next token. + cur_items.extend(next_items.drain(..)); + parser.to_mut().bump(); + } - if !next_items.is_empty() { - // Dump all possible `next_items` into `cur_items` for the next iteration. Then process - // the next token. - cur_items.extend(next_items.drain(..)); - parser.to_mut().bump(); - } else { - // Finally, we have the case where we need to call the black-box parser to get some - // nonterminal. - assert_eq!(bb_items.len(), 1); - - let mut item = bb_items.pop().unwrap(); - if let TokenTree::MetaVarDecl(span, _, Some(kind)) = item.top_elts.get_tt(item.idx) { - let match_cur = item.match_cur; - // We use the span of the metavariable declaration to determine any - // edition-specific matching behavior for non-terminals. - let nt = match parser.to_mut().parse_nonterminal(kind) { - Err(mut err) => { - err.span_label( - span, - format!("while parsing argument for this `{}` macro fragment", kind), - ) - .emit(); - return ErrorReported; - } - Ok(nt) => nt, - }; - item.push_match(match_cur, MatchedNonterminal(Lrc::new(nt))); - item.idx += 1; - item.match_cur += 1; - } else { - unreachable!() + (0, 1) => { + // We need to call the black-box parser to get some nonterminal. + let mut item = bb_items.pop().unwrap(); + if let TokenTree::MetaVarDecl(span, _, Some(kind)) = item.top_elts.get_tt(item.idx) + { + let match_cur = item.match_cur; + // We use the span of the metavariable declaration to determine any + // edition-specific matching behavior for non-terminals. + let nt = match parser.to_mut().parse_nonterminal(kind) { + Err(mut err) => { + err.span_label( + span, + format!( + "while parsing argument for this `{}` macro fragment", + kind + ), + ) + .emit(); + return ErrorReported; + } + Ok(nt) => nt, + }; + item.push_match(match_cur, MatchedNonterminal(Lrc::new(nt))); + item.idx += 1; + item.match_cur += 1; + } else { + unreachable!() + } + cur_items.push(item); + } + + (_, _) => { + // We need to call the black-box parser to get some nonterminal, but something is + // wrong. + let nts = bb_items + .iter() + .map(|item| match item.top_elts.get_tt(item.idx) { + TokenTree::MetaVarDecl(_, bind, Some(kind)) => { + format!("{} ('{}')", kind, bind) + } + _ => panic!(), + }) + .collect::<Vec<String>>() + .join(" or "); + + return Error( + parser.token.span, + format!( + "local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}", + match next_items.len() { + 0 => format!("built-in NTs {}.", nts), + 1 => format!("built-in NTs {} or 1 other option.", nts), + n => format!("built-in NTs {} or {} other options.", nts, n), + } + ), + ); } - cur_items.push(item); } assert!(!cur_items.is_empty()); |