| //! This is an NFA-based parser, which calls out to the main Rust parser for named non-terminals |
| //! (which it commits to fully when it hits one in a grammar). There's a set of current NFA threads |
| //! and a set of next ones. Instead of NTs, we have a special case for Kleene star. The big-O, in |
| //! pathological cases, is worse than traditional use of NFA or Earley parsing, but it's an easier |
| //! fit for Macro-by-Example-style rules. |
| //! |
| //! (In order to prevent the pathological case, we'd need to lazily construct the resulting |
| //! `NamedMatch`es at the very end. It'd be a pain, and require more memory to keep around old |
| //! matcher positions, but it would also save overhead) |
| //! |
| //! We don't say this parser uses the Earley algorithm, because it's unnecessarily inaccurate. |
| //! The macro parser restricts itself to the features of finite state automata. Earley parsers |
| //! can be described as an extension of NFAs with completion rules, prediction rules, and recursion. |
| //! |
| //! Quick intro to how the parser works: |
| //! |
| //! A "matcher position" (a.k.a. "position" or "mp") is a dot in the middle of a matcher, usually |
| //! written as a `·`. For example `· a $( a )* a b` is one, as is `a $( · a )* a b`. |
| //! |
| //! The parser walks through the input a token at a time, maintaining a list |
| //! of threads consistent with the current position in the input string: `cur_mps`. |
| //! |
| //! As it processes them, it fills up `eof_mps` with threads that would be valid if |
| //! the macro invocation is now over, `bb_mps` with threads that are waiting on |
| //! a Rust non-terminal like `$e:expr`, and `next_mps` with threads that are waiting |
| //! on a particular token. Most of the logic concerns moving the · through the |
| //! repetitions indicated by Kleene stars. The rules for moving the · without |
| //! consuming any input are called epsilon transitions. It only advances or calls |
| //! out to the real Rust parser when no `cur_mps` threads remain. |
| //! |
| //! Example: |
| //! |
| //! ```text, ignore |
| //! Start parsing a a a a b against [· a $( a )* a b]. |
| //! |
| //! Remaining input: a a a a b |
| //! next: [· a $( a )* a b] |
| //! |
| //! - - - Advance over an a. - - - |
| //! |
| //! Remaining input: a a a b |
| //! cur: [a · $( a )* a b] |
| //! Descend/Skip (first position). |
| //! next: [a $( · a )* a b] [a $( a )* · a b]. |
| //! |
| //! - - - Advance over an a. - - - |
| //! |
| //! Remaining input: a a b |
| //! cur: [a $( a · )* a b] [a $( a )* a · b] |
| //! Follow epsilon transition: Finish/Repeat (first position) |
| //! next: [a $( a )* · a b] [a $( · a )* a b] [a $( a )* a · b] |
| //! |
| //! - - - Advance over an a. - - - (this looks exactly like the last step) |
| //! |
| //! Remaining input: a b |
| //! cur: [a $( a · )* a b] [a $( a )* a · b] |
| //! Follow epsilon transition: Finish/Repeat (first position) |
| //! next: [a $( a )* · a b] [a $( · a )* a b] [a $( a )* a · b] |
| //! |
| //! - - - Advance over an a. - - - (this looks exactly like the last step) |
| //! |
| //! Remaining input: b |
| //! cur: [a $( a · )* a b] [a $( a )* a · b] |
| //! Follow epsilon transition: Finish/Repeat (first position) |
| //! next: [a $( a )* · a b] [a $( · a )* a b] [a $( a )* a · b] |
| //! |
| //! - - - Advance over a b. - - - |
| //! |
| //! Remaining input: '' |
| //! eof: [a $( a )* a b ·] |
| //! ``` |
| |
| crate use NamedMatch::*; |
| crate use ParseResult::*; |
| |
| use crate::mbe::{KleeneOp, TokenTree}; |
| |
| use rustc_ast::token::{self, DocComment, Nonterminal, NonterminalKind, Token}; |
| use rustc_parse::parser::{NtOrTt, Parser}; |
| use rustc_session::parse::ParseSess; |
| use rustc_span::symbol::MacroRulesNormalizedIdent; |
| use rustc_span::Span; |
| |
| use smallvec::{smallvec, SmallVec}; |
| |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_data_structures::sync::Lrc; |
| use rustc_span::symbol::Ident; |
| use std::borrow::Cow; |
| use std::collections::hash_map::Entry::{Occupied, Vacant}; |
| |
| // One element is enough to cover 95-99% of vectors for most benchmarks. Also, vectors longer than |
| // one frequently have many elements, not just two or three. |
| type NamedMatchVec = SmallVec<[NamedMatch; 1]>; |
| |
| // This type is used a lot. Make sure it doesn't unintentionally get bigger. |
| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
| rustc_data_structures::static_assert_size!(NamedMatchVec, 48); |
| |
| /// A unit within a matcher that a `MatcherPos` can refer to. Similar to (and derived from) |
| /// `mbe::TokenTree`, but designed specifically for fast and easy traversal during matching. |
| /// Notable differences to `mbe::TokenTree`: |
| /// - It is non-recursive, i.e. there is no nesting. |
| /// - The end pieces of each sequence (the separator, if present, and the Kleene op) are |
| /// represented explicitly, as is the very end of the matcher. |
| /// |
| /// This means a matcher can be represented by `&[MatcherLoc]`, and traversal mostly involves |
| /// simply incrementing the current matcher position index by one. |
| pub(super) enum MatcherLoc { |
| Token { |
| token: Token, |
| }, |
| Delimited, |
| Sequence { |
| op: KleeneOp, |
| num_metavar_decls: usize, |
| idx_first_after: usize, |
| next_metavar: usize, |
| seq_depth: usize, |
| }, |
| SequenceKleeneOpNoSep { |
| op: KleeneOp, |
| idx_first: usize, |
| }, |
| SequenceSep { |
| separator: Token, |
| }, |
| SequenceKleeneOpAfterSep { |
| idx_first: usize, |
| }, |
| MetaVarDecl { |
| span: Span, |
| bind: Ident, |
| kind: Option<NonterminalKind>, |
| next_metavar: usize, |
| seq_depth: usize, |
| }, |
| Eof, |
| } |
| |
| pub(super) fn compute_locs(sess: &ParseSess, matcher: &[TokenTree]) -> Vec<MatcherLoc> { |
| fn inner( |
| sess: &ParseSess, |
| tts: &[TokenTree], |
| locs: &mut Vec<MatcherLoc>, |
| next_metavar: &mut usize, |
| seq_depth: usize, |
| ) { |
| for tt in tts { |
| match tt { |
| TokenTree::Token(token) => { |
| locs.push(MatcherLoc::Token { token: token.clone() }); |
| } |
| TokenTree::Delimited(_, delimited) => { |
| locs.push(MatcherLoc::Delimited); |
| inner(sess, &delimited.all_tts, locs, next_metavar, seq_depth); |
| } |
| TokenTree::Sequence(_, seq) => { |
| // We can't determine `idx_first_after` and construct the final |
| // `MatcherLoc::Sequence` until after `inner()` is called and the sequence end |
| // pieces are processed. So we push a dummy value (`Eof` is cheapest to |
| // construct) now, and overwrite it with the proper value below. |
| let dummy = MatcherLoc::Eof; |
| locs.push(dummy); |
| |
| let next_metavar_orig = *next_metavar; |
| let op = seq.kleene.op; |
| let idx_first = locs.len(); |
| let idx_seq = idx_first - 1; |
| inner(sess, &seq.tts, locs, next_metavar, seq_depth + 1); |
| |
| if let Some(separator) = &seq.separator { |
| locs.push(MatcherLoc::SequenceSep { separator: separator.clone() }); |
| locs.push(MatcherLoc::SequenceKleeneOpAfterSep { idx_first }); |
| } else { |
| locs.push(MatcherLoc::SequenceKleeneOpNoSep { op, idx_first }); |
| } |
| |
| // Overwrite the dummy value pushed above with the proper value. |
| locs[idx_seq] = MatcherLoc::Sequence { |
| op, |
| num_metavar_decls: seq.num_captures, |
| idx_first_after: locs.len(), |
| next_metavar: next_metavar_orig, |
| seq_depth, |
| }; |
| } |
| &TokenTree::MetaVarDecl(span, bind, kind) => { |
| locs.push(MatcherLoc::MetaVarDecl { |
| span, |
| bind, |
| kind, |
| next_metavar: *next_metavar, |
| seq_depth, |
| }); |
| *next_metavar += 1; |
| } |
| TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(), |
| } |
| } |
| } |
| |
| let mut locs = vec![]; |
| let mut next_metavar = 0; |
| inner(sess, matcher, &mut locs, &mut next_metavar, /* seq_depth */ 0); |
| |
| // A final entry is needed for eof. |
| locs.push(MatcherLoc::Eof); |
| |
| locs |
| } |
| |
| /// A single matcher position, representing the state of matching. |
| struct MatcherPos { |
| /// The index into `TtParser::locs`, which represents the "dot". |
| idx: usize, |
| |
| /// The matches made against metavar decls so far. On a successful match, this vector ends up |
| /// with one element per metavar decl in the matcher. Each element records token trees matched |
| /// against the relevant metavar by the black box parser. An element will be a `MatchedSeq` if |
| /// the corresponding metavar decl is within a sequence. |
| matches: Lrc<NamedMatchVec>, |
| } |
| |
| // This type is used a lot. Make sure it doesn't unintentionally get bigger. |
| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
| rustc_data_structures::static_assert_size!(MatcherPos, 16); |
| |
| impl MatcherPos { |
| /// Adds `m` as a named match for the `metavar_idx`-th metavar. There are only two call sites, |
| /// and both are hot enough to be always worth inlining. |
| #[inline(always)] |
| fn push_match(&mut self, metavar_idx: usize, seq_depth: usize, m: NamedMatch) { |
| let matches = Lrc::make_mut(&mut self.matches); |
| match seq_depth { |
| 0 => { |
| // We are not within a sequence. Just append `m`. |
| assert_eq!(metavar_idx, matches.len()); |
| matches.push(m); |
| } |
| _ => { |
| // We are within a sequence. Find the final `MatchedSeq` at the appropriate depth |
| // and append `m` to its vector. |
| let mut curr = &mut matches[metavar_idx]; |
| for _ in 0..seq_depth - 1 { |
| match curr { |
| MatchedSeq(seq) => { |
| let seq = Lrc::make_mut(seq); |
| curr = seq.last_mut().unwrap(); |
| } |
| _ => unreachable!(), |
| } |
| } |
| match curr { |
| MatchedSeq(seq) => { |
| let seq = Lrc::make_mut(seq); |
| seq.push(m); |
| } |
| _ => unreachable!(), |
| } |
| } |
| } |
| } |
| } |
| |
| enum EofMatcherPositions { |
| None, |
| One(MatcherPos), |
| Multiple, |
| } |
| |
| /// Represents the possible results of an attempted parse. |
| crate enum ParseResult<T> { |
| /// Parsed successfully. |
| Success(T), |
| /// Arm failed to match. If the second parameter is `token::Eof`, it indicates an unexpected |
| /// end of macro invocation. Otherwise, it indicates that no rules expected the given token. |
| Failure(Token, &'static str), |
| /// Fatal error (malformed macro?). Abort compilation. |
| Error(rustc_span::Span, String), |
| ErrorReported, |
| } |
| |
| /// A `ParseResult` where the `Success` variant contains a mapping of |
| /// `MacroRulesNormalizedIdent`s to `NamedMatch`es. This represents the mapping |
| /// of metavars to the token trees they bind to. |
| crate type NamedParseResult = ParseResult<FxHashMap<MacroRulesNormalizedIdent, NamedMatch>>; |
| |
| /// Count how many metavars declarations are in `matcher`. |
| pub(super) fn count_metavar_decls(matcher: &[TokenTree]) -> usize { |
| matcher |
| .iter() |
| .map(|tt| match tt { |
| TokenTree::MetaVarDecl(..) => 1, |
| TokenTree::Sequence(_, seq) => seq.num_captures, |
| TokenTree::Delimited(_, delim) => count_metavar_decls(delim.inner_tts()), |
| TokenTree::Token(..) => 0, |
| TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(), |
| }) |
| .sum() |
| } |
| |
| /// `NamedMatch` is a pattern-match result for a single metavar. All |
| /// `MatchedNonterminal`s in the `NamedMatch` have the same non-terminal type |
| /// (expr, item, etc). |
| /// |
| /// The in-memory structure of a particular `NamedMatch` represents the match |
| /// that occurred when a particular subset of a matcher was applied to a |
| /// particular token tree. |
| /// |
| /// The width of each `MatchedSeq` in the `NamedMatch`, and the identity of |
| /// the `MatchedNtNonTts`s, will depend on the token tree it was applied |
| /// to: each `MatchedSeq` corresponds to a single repetition in the originating |
| /// token tree. The depth of the `NamedMatch` structure will therefore depend |
| /// only on the nesting depth of repetitions in the originating token tree it |
| /// was derived from. |
| /// |
| /// In layperson's terms: `NamedMatch` will form a tree representing nested matches of a particular |
| /// meta variable. For example, if we are matching the following macro against the following |
| /// invocation... |
| /// |
| /// ```rust |
| /// macro_rules! foo { |
| /// ($($($x:ident),+);+) => {} |
| /// } |
| /// |
| /// foo!(a, b, c, d; a, b, c, d, e); |
| /// ``` |
| /// |
| /// Then, the tree will have the following shape: |
| /// |
| /// ```rust |
| /// MatchedSeq([ |
| /// MatchedSeq([ |
| /// MatchedNonterminal(a), |
| /// MatchedNonterminal(b), |
| /// MatchedNonterminal(c), |
| /// MatchedNonterminal(d), |
| /// ]), |
| /// MatchedSeq([ |
| /// MatchedNonterminal(a), |
| /// MatchedNonterminal(b), |
| /// MatchedNonterminal(c), |
| /// MatchedNonterminal(d), |
| /// MatchedNonterminal(e), |
| /// ]) |
| /// ]) |
| /// ``` |
| #[derive(Debug, Clone)] |
| crate enum NamedMatch { |
| MatchedSeq(Lrc<NamedMatchVec>), |
| |
| // A metavar match of type `tt`. |
| MatchedTokenTree(rustc_ast::tokenstream::TokenTree), |
| |
| // A metavar match of any type other than `tt`. |
| MatchedNonterminal(Lrc<Nonterminal>), |
| } |
| |
| /// Performs a token equality check, ignoring syntax context (that is, an unhygienic comparison) |
| fn token_name_eq(t1: &Token, t2: &Token) -> bool { |
| if let (Some((ident1, is_raw1)), Some((ident2, is_raw2))) = (t1.ident(), t2.ident()) { |
| ident1.name == ident2.name && is_raw1 == is_raw2 |
| } else if let (Some(ident1), Some(ident2)) = (t1.lifetime(), t2.lifetime()) { |
| ident1.name == ident2.name |
| } else { |
| t1.kind == t2.kind |
| } |
| } |
| |
| // Note: the vectors could be created and dropped within `parse_tt`, but to avoid excess |
| // allocations we have a single vector fo each kind that is cleared and reused repeatedly. |
| pub struct TtParser { |
| macro_name: Ident, |
| |
| /// The set of current mps to be processed. This should be empty by the end of a successful |
| /// execution of `parse_tt_inner`. |
| cur_mps: Vec<MatcherPos>, |
| |
| /// The set of newly generated mps. These are used to replenish `cur_mps` in the function |
| /// `parse_tt`. |
| next_mps: Vec<MatcherPos>, |
| |
| /// The set of mps that are waiting for the black-box parser. |
| bb_mps: Vec<MatcherPos>, |
| |
| /// Pre-allocate an empty match array, so it can be cloned cheaply for macros with many rules |
| /// that have no metavars. |
| empty_matches: Lrc<NamedMatchVec>, |
| } |
| |
| impl TtParser { |
| pub(super) fn new(macro_name: Ident) -> TtParser { |
| TtParser { |
| macro_name, |
| cur_mps: vec![], |
| next_mps: vec![], |
| bb_mps: vec![], |
| empty_matches: Lrc::new(smallvec![]), |
| } |
| } |
| |
| /// Process the matcher positions of `cur_mps` until it is empty. In the process, this will |
| /// produce more mps in `next_mps` and `bb_mps`. |
| /// |
| /// # Returns |
| /// |
| /// `Some(result)` if everything is finished, `None` otherwise. Note that matches are kept |
| /// track of through the mps generated. |
| fn parse_tt_inner( |
| &mut self, |
| sess: &ParseSess, |
| matcher: &[MatcherLoc], |
| token: &Token, |
| ) -> Option<NamedParseResult> { |
| // Matcher positions that would be valid if the macro invocation was over now. Only |
| // modified if `token == Eof`. |
| let mut eof_mps = EofMatcherPositions::None; |
| |
| while let Some(mut mp) = self.cur_mps.pop() { |
| match &matcher[mp.idx] { |
| MatcherLoc::Token { token: t } => { |
| // If it's a doc comment, we just ignore it and move on to the next tt in the |
| // matcher. This is a bug, but #95267 showed that existing programs rely on |
| // this behaviour, and changing it would require some care and a transition |
| // period. |
| // |
| // If the token matches, we can just advance the parser. |
| // |
| // Otherwise, this match has failed, there is nothing to do, and hopefully |
| // another mp in `cur_mps` will match. |
| if matches!(t, Token { kind: DocComment(..), .. }) { |
| mp.idx += 1; |
| self.cur_mps.push(mp); |
| } else if token_name_eq(&t, token) { |
| mp.idx += 1; |
| self.next_mps.push(mp); |
| } |
| } |
| MatcherLoc::Delimited => { |
| // Entering the delimeter is trivial. |
| mp.idx += 1; |
| self.cur_mps.push(mp); |
| } |
| &MatcherLoc::Sequence { |
| op, |
| num_metavar_decls, |
| idx_first_after, |
| next_metavar, |
| seq_depth, |
| } => { |
| // Install an empty vec for each metavar within the sequence. |
| for metavar_idx in next_metavar..next_metavar + num_metavar_decls { |
| mp.push_match( |
| metavar_idx, |
| seq_depth, |
| MatchedSeq(self.empty_matches.clone()), |
| ); |
| } |
| |
| if op == KleeneOp::ZeroOrMore || op == KleeneOp::ZeroOrOne { |
| // Try zero matches of this sequence, by skipping over it. |
| self.cur_mps.push(MatcherPos { |
| idx: idx_first_after, |
| matches: mp.matches.clone(), // a cheap clone |
| }); |
| } |
| |
| // Try one or more matches of this sequence, by entering it. |
| mp.idx += 1; |
| self.cur_mps.push(mp); |
| } |
| &MatcherLoc::SequenceKleeneOpNoSep { op, idx_first } => { |
| // We are past the end of a sequence with no separator. Try ending the |
| // sequence. If that's not possible, `ending_mp` will fail quietly when it is |
| // processed next time around the loop. |
| let ending_mp = MatcherPos { |
| idx: mp.idx + 1, // +1 skips the Kleene op |
| matches: mp.matches.clone(), // a cheap clone |
| }; |
| self.cur_mps.push(ending_mp); |
| |
| if op != KleeneOp::ZeroOrOne { |
| // Try another repetition. |
| mp.idx = idx_first; |
| self.cur_mps.push(mp); |
| } |
| } |
| MatcherLoc::SequenceSep { separator } => { |
| // We are past the end of a sequence with a separator but we haven't seen the |
| // separator yet. Try ending the sequence. If that's not possible, `ending_mp` |
| // will fail quietly when it is processed next time around the loop. |
| let ending_mp = MatcherPos { |
| idx: mp.idx + 2, // +2 skips the separator and the Kleene op |
| matches: mp.matches.clone(), // a cheap clone |
| }; |
| self.cur_mps.push(ending_mp); |
| |
| if token_name_eq(token, separator) { |
| // The separator matches the current token. Advance past it. |
| mp.idx += 1; |
| self.next_mps.push(mp); |
| } |
| } |
| &MatcherLoc::SequenceKleeneOpAfterSep { idx_first } => { |
| // We are past the sequence separator. This can't be a `?` Kleene op, because |
| // they don't permit separators. Try another repetition. |
| mp.idx = idx_first; |
| self.cur_mps.push(mp); |
| } |
| &MatcherLoc::MetaVarDecl { span, kind, .. } => { |
| // Built-in nonterminals never start with these tokens, so we can eliminate |
| // them from consideration. We use the span of the metavariable declaration |
| // to determine any edition-specific matching behavior for non-terminals. |
| if let Some(kind) = kind { |
| if Parser::nonterminal_may_begin_with(kind, token) { |
| self.bb_mps.push(mp); |
| } |
| } else { |
| // Both this check and the one in `nameize` are necessary, surprisingly. |
| if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() { |
| // E.g. `$e` instead of `$e:expr`. |
| return Some(Error(span, "missing fragment specifier".to_string())); |
| } |
| } |
| } |
| MatcherLoc::Eof => { |
| // We are past the matcher's end, and not in a sequence. Try to end things. |
| debug_assert_eq!(mp.idx, matcher.len() - 1); |
| if *token == token::Eof { |
| eof_mps = match eof_mps { |
| EofMatcherPositions::None => EofMatcherPositions::One(mp), |
| EofMatcherPositions::One(_) | EofMatcherPositions::Multiple => { |
| EofMatcherPositions::Multiple |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| // If we reached the end of input, check that there is EXACTLY ONE possible matcher. |
| // Otherwise, either the parse is ambiguous (which is an error) or there is a syntax error. |
| if *token == token::Eof { |
| Some(match eof_mps { |
| EofMatcherPositions::One(mut eof_mp) => { |
| // Need to take ownership of the matches from within the `Lrc`. |
| Lrc::make_mut(&mut eof_mp.matches); |
| let matches = Lrc::try_unwrap(eof_mp.matches).unwrap().into_iter(); |
| self.nameize(sess, matcher, matches) |
| } |
| EofMatcherPositions::Multiple => { |
| Error(token.span, "ambiguity: multiple successful parses".to_string()) |
| } |
| EofMatcherPositions::None => Failure( |
| Token::new( |
| token::Eof, |
| if token.span.is_dummy() { token.span } else { token.span.shrink_to_hi() }, |
| ), |
| "missing tokens in macro arguments", |
| ), |
| }) |
| } else { |
| None |
| } |
| } |
| |
| /// Match the token stream from `parser` against `matcher`. |
| pub(super) fn parse_tt( |
| &mut self, |
| parser: &mut Cow<'_, Parser<'_>>, |
| matcher: &[MatcherLoc], |
| ) -> NamedParseResult { |
| // A queue of possible matcher positions. We initialize it with the matcher position in |
| // which the "dot" is before the first token of the first token tree in `matcher`. |
| // `parse_tt_inner` then processes all of these possible matcher positions and produces |
| // possible next positions into `next_mps`. After some post-processing, the contents of |
| // `next_mps` replenish `cur_mps` and we start over again. |
| self.cur_mps.clear(); |
| self.cur_mps.push(MatcherPos { idx: 0, matches: self.empty_matches.clone() }); |
| |
| loop { |
| self.next_mps.clear(); |
| self.bb_mps.clear(); |
| |
| // Process `cur_mps` until either we have finished the input or we need to get some |
| // parsing from the black-box parser done. |
| if let Some(res) = self.parse_tt_inner(&parser.sess, matcher, &parser.token) { |
| return res; |
| } |
| |
| // `parse_tt_inner` handled all of `cur_mps`, so it's empty. |
| assert!(self.cur_mps.is_empty()); |
| |
| // Error messages here could be improved with links to original rules. |
| match (self.next_mps.len(), self.bb_mps.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", |
| ); |
| } |
| |
| (_, 0) => { |
| // Dump all possible `next_mps` into `cur_mps` for the next iteration. Then |
| // process the next token. |
| self.cur_mps.extend(self.next_mps.drain(..)); |
| parser.to_mut().bump(); |
| } |
| |
| (0, 1) => { |
| // We need to call the black-box parser to get some nonterminal. |
| let mut mp = self.bb_mps.pop().unwrap(); |
| let loc = &matcher[mp.idx]; |
| if let &MatcherLoc::MetaVarDecl { |
| span, |
| kind: Some(kind), |
| next_metavar, |
| seq_depth, |
| .. |
| } = loc |
| { |
| // 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 `{kind}` macro fragment" |
| ), |
| ) |
| .emit(); |
| return ErrorReported; |
| } |
| Ok(nt) => nt, |
| }; |
| let m = match nt { |
| NtOrTt::Nt(nt) => MatchedNonterminal(Lrc::new(nt)), |
| NtOrTt::Tt(tt) => MatchedTokenTree(tt), |
| }; |
| mp.push_match(next_metavar, seq_depth, m); |
| mp.idx += 1; |
| } else { |
| unreachable!() |
| } |
| self.cur_mps.push(mp); |
| } |
| |
| (_, _) => { |
| // Too many possibilities! |
| return self.ambiguity_error(matcher, parser.token.span); |
| } |
| } |
| |
| assert!(!self.cur_mps.is_empty()); |
| } |
| } |
| |
| fn ambiguity_error( |
| &self, |
| matcher: &[MatcherLoc], |
| token_span: rustc_span::Span, |
| ) -> NamedParseResult { |
| let nts = self |
| .bb_mps |
| .iter() |
| .map(|mp| match &matcher[mp.idx] { |
| MatcherLoc::MetaVarDecl { bind, kind: Some(kind), .. } => { |
| format!("{} ('{}')", kind, bind) |
| } |
| _ => unreachable!(), |
| }) |
| .collect::<Vec<String>>() |
| .join(" or "); |
| |
| Error( |
| token_span, |
| format!( |
| "local ambiguity when calling macro `{}`: multiple parsing options: {}", |
| self.macro_name, |
| match self.next_mps.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), |
| } |
| ), |
| ) |
| } |
| |
| fn nameize<I: Iterator<Item = NamedMatch>>( |
| &self, |
| sess: &ParseSess, |
| matcher: &[MatcherLoc], |
| mut res: I, |
| ) -> NamedParseResult { |
| // Make that each metavar has _exactly one_ binding. If so, insert the binding into the |
| // `NamedParseResult`. Otherwise, it's an error. |
| let mut ret_val = FxHashMap::default(); |
| for loc in matcher { |
| if let &MatcherLoc::MetaVarDecl { span, bind, kind, .. } = loc { |
| if kind.is_some() { |
| match ret_val.entry(MacroRulesNormalizedIdent::new(bind)) { |
| Vacant(spot) => spot.insert(res.next().unwrap()), |
| Occupied(..) => { |
| return Error(span, format!("duplicated bind name: {}", bind)); |
| } |
| }; |
| } else { |
| // Both this check and the one in `parse_tt_inner` are necessary, surprisingly. |
| if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() { |
| // E.g. `$e` instead of `$e:expr`. |
| return Error(span, "missing fragment specifier".to_string()); |
| } |
| } |
| } |
| } |
| Success(ret_val) |
| } |
| } |
