| use crate::{ast, attr}; |
| use crate::edition::Edition; |
| use crate::ext::base::{DummyResult, ExtCtxt, MacResult, SyntaxExtension}; |
| use crate::ext::base::{NormalTT, TTMacroExpander}; |
| use crate::ext::expand::{AstFragment, AstFragmentKind}; |
| use crate::ext::tt::macro_parser::{Success, Error, Failure}; |
| use crate::ext::tt::macro_parser::{MatchedSeq, MatchedNonterminal}; |
| use crate::ext::tt::macro_parser::{parse, parse_failure_msg}; |
| use crate::ext::tt::quoted; |
| use crate::ext::tt::transcribe::transcribe; |
| use crate::feature_gate::Features; |
| use crate::parse::{Directory, ParseSess}; |
| use crate::parse::parser::Parser; |
| use crate::parse::token::{self, NtTT}; |
| use crate::parse::token::Token::*; |
| use crate::symbol::Symbol; |
| use crate::tokenstream::{DelimSpan, TokenStream, TokenTree}; |
| |
| use errors::FatalError; |
| use syntax_pos::{Span, DUMMY_SP, symbol::Ident}; |
| use log::debug; |
| |
| use rustc_data_structures::fx::{FxHashMap}; |
| use std::borrow::Cow; |
| use std::collections::hash_map::Entry; |
| |
| use rustc_data_structures::sync::Lrc; |
| use errors::Applicability; |
| |
| const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \ |
| `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, \ |
| `path`, `meta`, `tt`, `item` and `vis`"; |
| |
| pub struct ParserAnyMacro<'a> { |
| parser: Parser<'a>, |
| |
| /// Span of the expansion site of the macro this parser is for |
| site_span: Span, |
| /// The ident of the macro we're parsing |
| macro_ident: ast::Ident, |
| arm_span: Span, |
| } |
| |
| impl<'a> ParserAnyMacro<'a> { |
| pub fn make(mut self: Box<ParserAnyMacro<'a>>, kind: AstFragmentKind) -> AstFragment { |
| let ParserAnyMacro { site_span, macro_ident, ref mut parser, arm_span } = *self; |
| let fragment = panictry!(parser.parse_ast_fragment(kind, true).map_err(|mut e| { |
| if parser.token == token::Eof && e.message().ends_with(", found `<eof>`") { |
| if !e.span.is_dummy() { // early end of macro arm (#52866) |
| e.replace_span_with(parser.sess.source_map().next_point(parser.span)); |
| } |
| let msg = &e.message[0]; |
| e.message[0] = ( |
| format!( |
| "macro expansion ends with an incomplete expression: {}", |
| msg.0.replace(", found `<eof>`", ""), |
| ), |
| msg.1, |
| ); |
| } |
| if e.span.is_dummy() { // Get around lack of span in error (#30128) |
| e.replace_span_with(site_span); |
| if parser.sess.source_map().span_to_filename(arm_span).is_real() { |
| e.span_label(arm_span, "in this macro arm"); |
| } |
| } else if !parser.sess.source_map().span_to_filename(parser.span).is_real() { |
| e.span_label(site_span, "in this macro invocation"); |
| } |
| e |
| })); |
| |
| // We allow semicolons at the end of expressions -- e.g., the semicolon in |
| // `macro_rules! m { () => { panic!(); } }` isn't parsed by `.parse_expr()`, |
| // but `m!()` is allowed in expression positions (cf. issue #34706). |
| if kind == AstFragmentKind::Expr && parser.token == token::Semi { |
| parser.bump(); |
| } |
| |
| // Make sure we don't have any tokens left to parse so we don't silently drop anything. |
| let path = ast::Path::from_ident(macro_ident.with_span_pos(site_span)); |
| parser.ensure_complete_parse(&path, kind.name(), site_span); |
| fragment |
| } |
| } |
| |
| struct MacroRulesMacroExpander { |
| name: ast::Ident, |
| lhses: Vec<quoted::TokenTree>, |
| rhses: Vec<quoted::TokenTree>, |
| valid: bool, |
| } |
| |
| impl TTMacroExpander for MacroRulesMacroExpander { |
| fn expand<'cx>( |
| &self, |
| cx: &'cx mut ExtCtxt<'_>, |
| sp: Span, |
| input: TokenStream, |
| def_span: Option<Span>, |
| ) -> Box<dyn MacResult+'cx> { |
| if !self.valid { |
| return DummyResult::any(sp); |
| } |
| generic_extension(cx, |
| sp, |
| def_span, |
| self.name, |
| input, |
| &self.lhses, |
| &self.rhses) |
| } |
| } |
| |
| fn trace_macros_note(cx: &mut ExtCtxt<'_>, sp: Span, message: String) { |
| let sp = sp.macro_backtrace().last().map(|trace| trace.call_site).unwrap_or(sp); |
| cx.expansions.entry(sp).or_default().push(message); |
| } |
| |
| /// Given `lhses` and `rhses`, this is the new macro we create |
| fn generic_extension<'cx>(cx: &'cx mut ExtCtxt<'_>, |
| sp: Span, |
| def_span: Option<Span>, |
| name: ast::Ident, |
| arg: TokenStream, |
| lhses: &[quoted::TokenTree], |
| rhses: &[quoted::TokenTree]) |
| -> Box<dyn MacResult+'cx> { |
| if cx.trace_macros() { |
| trace_macros_note(cx, sp, format!("expanding `{}! {{ {} }}`", name, arg)); |
| } |
| |
| // Which arm's failure should we report? (the one furthest along) |
| let mut best_fail_spot = DUMMY_SP; |
| let mut best_fail_tok = None; |
| let mut best_fail_text = None; |
| |
| for (i, lhs) in lhses.iter().enumerate() { // try each arm's matchers |
| let lhs_tt = match *lhs { |
| quoted::TokenTree::Delimited(_, ref delim) => &delim.tts[..], |
| _ => cx.span_bug(sp, "malformed macro lhs") |
| }; |
| |
| match TokenTree::parse(cx, lhs_tt, arg.clone()) { |
| Success(named_matches) => { |
| let rhs = match rhses[i] { |
| // ignore delimiters |
| quoted::TokenTree::Delimited(_, ref delimed) => delimed.tts.clone(), |
| _ => cx.span_bug(sp, "malformed macro rhs"), |
| }; |
| let arm_span = rhses[i].span(); |
| |
| let rhs_spans = rhs.iter().map(|t| t.span()).collect::<Vec<_>>(); |
| // rhs has holes ( `$id` and `$(...)` that need filled) |
| let mut tts = transcribe(cx, Some(named_matches), rhs); |
| |
| // Replace all the tokens for the corresponding positions in the macro, to maintain |
| // proper positions in error reporting, while maintaining the macro_backtrace. |
| if rhs_spans.len() == tts.len() { |
| tts = tts.map_enumerated(|i, mut tt| { |
| let mut sp = rhs_spans[i]; |
| sp = sp.with_ctxt(tt.span().ctxt()); |
| tt.set_span(sp); |
| tt |
| }); |
| } |
| |
| if cx.trace_macros() { |
| trace_macros_note(cx, sp, format!("to `{}`", tts)); |
| } |
| |
| let directory = Directory { |
| path: Cow::from(cx.current_expansion.module.directory.as_path()), |
| ownership: cx.current_expansion.directory_ownership, |
| }; |
| let mut p = Parser::new(cx.parse_sess(), tts, Some(directory), true, false); |
| p.root_module_name = cx.current_expansion.module.mod_path.last() |
| .map(|id| id.as_str().to_string()); |
| |
| p.process_potential_macro_variable(); |
| // Let the context choose how to interpret the result. |
| // Weird, but useful for X-macros. |
| return Box::new(ParserAnyMacro { |
| parser: p, |
| |
| // Pass along the original expansion site and the name of the macro |
| // so we can print a useful error message if the parse of the expanded |
| // macro leaves unparsed tokens. |
| site_span: sp, |
| macro_ident: name, |
| arm_span, |
| }) |
| } |
| Failure(sp, tok, t) => if sp.lo() >= best_fail_spot.lo() { |
| best_fail_spot = sp; |
| best_fail_tok = Some(tok); |
| best_fail_text = Some(t); |
| }, |
| Error(err_sp, ref msg) => { |
| cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..]) |
| } |
| } |
| } |
| |
| let best_fail_msg = parse_failure_msg(best_fail_tok.expect("ran no matchers")); |
| let span = best_fail_spot.substitute_dummy(sp); |
| let mut err = cx.struct_span_err(span, &best_fail_msg); |
| err.span_label(span, best_fail_text.unwrap_or(&best_fail_msg)); |
| if let Some(sp) = def_span { |
| if cx.source_map().span_to_filename(sp).is_real() && !sp.is_dummy() { |
| err.span_label(cx.source_map().def_span(sp), "when calling this macro"); |
| } |
| } |
| |
| // Check whether there's a missing comma in this macro call, like `println!("{}" a);` |
| if let Some((arg, comma_span)) = arg.add_comma() { |
| for lhs in lhses { // try each arm's matchers |
| let lhs_tt = match *lhs { |
| quoted::TokenTree::Delimited(_, ref delim) => &delim.tts[..], |
| _ => continue, |
| }; |
| match TokenTree::parse(cx, lhs_tt, arg.clone()) { |
| Success(_) => { |
| if comma_span.is_dummy() { |
| err.note("you might be missing a comma"); |
| } else { |
| err.span_suggestion_short( |
| comma_span, |
| "missing comma here", |
| ", ".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| _ => {} |
| } |
| } |
| } |
| err.emit(); |
| cx.trace_macros_diag(); |
| DummyResult::any(sp) |
| } |
| |
| // Note that macro-by-example's input is also matched against a token tree: |
| // $( $lhs:tt => $rhs:tt );+ |
| // |
| // Holy self-referential! |
| |
| /// Converts a `macro_rules!` invocation into a syntax extension. |
| pub fn compile( |
| sess: &ParseSess, |
| features: &Features, |
| def: &ast::Item, |
| edition: Edition |
| ) -> SyntaxExtension { |
| let lhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("lhs")); |
| let rhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("rhs")); |
| |
| // Parse the macro_rules! invocation |
| let body = match def.node { |
| ast::ItemKind::MacroDef(ref body) => body, |
| _ => unreachable!(), |
| }; |
| |
| // The pattern that macro_rules matches. |
| // The grammar for macro_rules! is: |
| // $( $lhs:tt => $rhs:tt );+ |
| // ...quasiquoting this would be nice. |
| // These spans won't matter, anyways |
| let argument_gram = vec![ |
| quoted::TokenTree::Sequence(DelimSpan::dummy(), Lrc::new(quoted::SequenceRepetition { |
| tts: vec![ |
| quoted::TokenTree::MetaVarDecl(DUMMY_SP, lhs_nm, ast::Ident::from_str("tt")), |
| quoted::TokenTree::Token(DUMMY_SP, token::FatArrow), |
| quoted::TokenTree::MetaVarDecl(DUMMY_SP, rhs_nm, ast::Ident::from_str("tt")), |
| ], |
| separator: Some(if body.legacy { token::Semi } else { token::Comma }), |
| op: quoted::KleeneOp::OneOrMore, |
| num_captures: 2, |
| })), |
| // to phase into semicolon-termination instead of semicolon-separation |
| quoted::TokenTree::Sequence(DelimSpan::dummy(), Lrc::new(quoted::SequenceRepetition { |
| tts: vec![quoted::TokenTree::Token(DUMMY_SP, token::Semi)], |
| separator: None, |
| op: quoted::KleeneOp::ZeroOrMore, |
| num_captures: 0 |
| })), |
| ]; |
| |
| let argument_map = match parse(sess, body.stream(), &argument_gram, None, true) { |
| Success(m) => m, |
| Failure(sp, tok, t) => { |
| let s = parse_failure_msg(tok); |
| let sp = sp.substitute_dummy(def.span); |
| let mut err = sess.span_diagnostic.struct_span_fatal(sp, &s); |
| err.span_label(sp, t); |
| err.emit(); |
| FatalError.raise(); |
| } |
| Error(sp, s) => { |
| sess.span_diagnostic.span_fatal(sp.substitute_dummy(def.span), &s).raise(); |
| } |
| }; |
| |
| let mut valid = true; |
| |
| // Extract the arguments: |
| let lhses = match *argument_map[&lhs_nm] { |
| MatchedSeq(ref s, _) => { |
| s.iter().map(|m| { |
| if let MatchedNonterminal(ref nt) = *m { |
| if let NtTT(ref tt) = **nt { |
| let tt = quoted::parse( |
| tt.clone().into(), |
| true, |
| sess, |
| features, |
| &def.attrs, |
| edition, |
| def.id, |
| ) |
| .pop() |
| .unwrap(); |
| valid &= check_lhs_nt_follows(sess, features, &def.attrs, &tt); |
| return tt; |
| } |
| } |
| sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
| }).collect::<Vec<quoted::TokenTree>>() |
| } |
| _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
| }; |
| |
| let rhses = match *argument_map[&rhs_nm] { |
| MatchedSeq(ref s, _) => { |
| s.iter().map(|m| { |
| if let MatchedNonterminal(ref nt) = *m { |
| if let NtTT(ref tt) = **nt { |
| return quoted::parse( |
| tt.clone().into(), |
| false, |
| sess, |
| features, |
| &def.attrs, |
| edition, |
| def.id, |
| ).pop() |
| .unwrap(); |
| } |
| } |
| sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
| }).collect::<Vec<quoted::TokenTree>>() |
| } |
| _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs") |
| }; |
| |
| for rhs in &rhses { |
| valid &= check_rhs(sess, rhs); |
| } |
| |
| // don't abort iteration early, so that errors for multiple lhses can be reported |
| for lhs in &lhses { |
| valid &= check_lhs_no_empty_seq(sess, &[lhs.clone()]); |
| valid &= check_lhs_duplicate_matcher_bindings( |
| sess, |
| &[lhs.clone()], |
| &mut FxHashMap::default(), |
| def.id |
| ); |
| } |
| |
| let expander: Box<_> = Box::new(MacroRulesMacroExpander { |
| name: def.ident, |
| lhses, |
| rhses, |
| valid, |
| }); |
| |
| if body.legacy { |
| let allow_internal_unstable = attr::find_by_name(&def.attrs, "allow_internal_unstable") |
| .map(|attr| attr |
| .meta_item_list() |
| .map(|list| list.iter() |
| .filter_map(|it| { |
| let name = it.ident().map(|ident| ident.name); |
| if name.is_none() { |
| sess.span_diagnostic.span_err(it.span(), |
| "allow internal unstable expects feature names") |
| } |
| name |
| }) |
| .collect::<Vec<Symbol>>().into() |
| ) |
| .unwrap_or_else(|| { |
| sess.span_diagnostic.span_warn( |
| attr.span, "allow_internal_unstable expects list of feature names. In the \ |
| future this will become a hard error. Please use `allow_internal_unstable(\ |
| foo, bar)` to only allow the `foo` and `bar` features", |
| ); |
| vec![Symbol::intern("allow_internal_unstable_backcompat_hack")].into() |
| }) |
| ); |
| let allow_internal_unsafe = attr::contains_name(&def.attrs, "allow_internal_unsafe"); |
| let mut local_inner_macros = false; |
| if let Some(macro_export) = attr::find_by_name(&def.attrs, "macro_export") { |
| if let Some(l) = macro_export.meta_item_list() { |
| local_inner_macros = attr::list_contains_name(&l, "local_inner_macros"); |
| } |
| } |
| |
| let unstable_feature = attr::find_stability(&sess, |
| &def.attrs, def.span).and_then(|stability| { |
| if let attr::StabilityLevel::Unstable { issue, .. } = stability.level { |
| Some((stability.feature, issue)) |
| } else { |
| None |
| } |
| }); |
| |
| NormalTT { |
| expander, |
| def_info: Some((def.id, def.span)), |
| allow_internal_unstable, |
| allow_internal_unsafe, |
| local_inner_macros, |
| unstable_feature, |
| edition, |
| } |
| } else { |
| let is_transparent = attr::contains_name(&def.attrs, "rustc_transparent_macro"); |
| |
| SyntaxExtension::DeclMacro { |
| expander, |
| def_info: Some((def.id, def.span)), |
| is_transparent, |
| edition, |
| } |
| } |
| } |
| |
| fn check_lhs_nt_follows(sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| lhs: "ed::TokenTree) -> bool { |
| // lhs is going to be like TokenTree::Delimited(...), where the |
| // entire lhs is those tts. Or, it can be a "bare sequence", not wrapped in parens. |
| if let quoted::TokenTree::Delimited(_, ref tts) = *lhs { |
| check_matcher(sess, features, attrs, &tts.tts) |
| } else { |
| let msg = "invalid macro matcher; matchers must be contained in balanced delimiters"; |
| sess.span_diagnostic.span_err(lhs.span(), msg); |
| false |
| } |
| // we don't abort on errors on rejection, the driver will do that for us |
| // after parsing/expansion. we can report every error in every macro this way. |
| } |
| |
| /// Checks that the lhs contains no repetition which could match an empty token |
| /// tree, because then the matcher would hang indefinitely. |
| fn check_lhs_no_empty_seq(sess: &ParseSess, tts: &[quoted::TokenTree]) -> bool { |
| use quoted::TokenTree; |
| for tt in tts { |
| match *tt { |
| TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => (), |
| TokenTree::Delimited(_, ref del) => if !check_lhs_no_empty_seq(sess, &del.tts) { |
| return false; |
| }, |
| TokenTree::Sequence(span, ref seq) => { |
| if seq.separator.is_none() && seq.tts.iter().all(|seq_tt| { |
| match *seq_tt { |
| TokenTree::MetaVarDecl(_, _, id) => id.name == "vis", |
| TokenTree::Sequence(_, ref sub_seq) => |
| sub_seq.op == quoted::KleeneOp::ZeroOrMore |
| || sub_seq.op == quoted::KleeneOp::ZeroOrOne, |
| _ => false, |
| } |
| }) { |
| let sp = span.entire(); |
| sess.span_diagnostic.span_err(sp, "repetition matches empty token tree"); |
| return false; |
| } |
| if !check_lhs_no_empty_seq(sess, &seq.tts) { |
| return false; |
| } |
| } |
| } |
| } |
| |
| true |
| } |
| |
| /// Check that the LHS contains no duplicate matcher bindings. e.g. `$a:expr, $a:expr` would be |
| /// illegal, since it would be ambiguous which `$a` to use if we ever needed to. |
| fn check_lhs_duplicate_matcher_bindings( |
| sess: &ParseSess, |
| tts: &[quoted::TokenTree], |
| metavar_names: &mut FxHashMap<Ident, Span>, |
| node_id: ast::NodeId, |
| ) -> bool { |
| use self::quoted::TokenTree; |
| use crate::early_buffered_lints::BufferedEarlyLintId; |
| for tt in tts { |
| match *tt { |
| TokenTree::MetaVarDecl(span, name, _kind) => { |
| if let Some(&prev_span) = metavar_names.get(&name) { |
| // FIXME(mark-i-m): in a few cycles, make this a hard error. |
| // sess.span_diagnostic |
| // .struct_span_err(span, "duplicate matcher binding") |
| // .span_note(prev_span, "previous declaration was here") |
| // .emit(); |
| sess.buffer_lint( |
| BufferedEarlyLintId::DuplicateMacroMatcherBindingName, |
| crate::source_map::MultiSpan::from(vec![prev_span, span]), |
| node_id, |
| "duplicate matcher binding" |
| ); |
| return false; |
| } else { |
| metavar_names.insert(name, span); |
| } |
| } |
| TokenTree::Delimited(_, ref del) => { |
| if !check_lhs_duplicate_matcher_bindings(sess, &del.tts, metavar_names, node_id) { |
| return false; |
| } |
| }, |
| TokenTree::Sequence(_, ref seq) => { |
| if !check_lhs_duplicate_matcher_bindings(sess, &seq.tts, metavar_names, node_id) { |
| return false; |
| } |
| } |
| _ => {} |
| } |
| } |
| |
| true |
| } |
| |
| fn check_rhs(sess: &ParseSess, rhs: "ed::TokenTree) -> bool { |
| match *rhs { |
| quoted::TokenTree::Delimited(..) => return true, |
| _ => sess.span_diagnostic.span_err(rhs.span(), "macro rhs must be delimited") |
| } |
| false |
| } |
| |
| fn check_matcher(sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| matcher: &[quoted::TokenTree]) -> bool { |
| let first_sets = FirstSets::new(matcher); |
| let empty_suffix = TokenSet::empty(); |
| let err = sess.span_diagnostic.err_count(); |
| check_matcher_core(sess, features, attrs, &first_sets, matcher, &empty_suffix); |
| err == sess.span_diagnostic.err_count() |
| } |
| |
| // `The FirstSets` for a matcher is a mapping from subsequences in the |
| // matcher to the FIRST set for that subsequence. |
| // |
| // This mapping is partially precomputed via a backwards scan over the |
| // token trees of the matcher, which provides a mapping from each |
| // repetition sequence to its *first* set. |
| // |
| // (Hypothetically, sequences should be uniquely identifiable via their |
| // spans, though perhaps that is false, e.g., for macro-generated macros |
| // that do not try to inject artificial span information. My plan is |
| // to try to catch such cases ahead of time and not include them in |
| // the precomputed mapping.) |
| struct FirstSets { |
| // this maps each TokenTree::Sequence `$(tt ...) SEP OP` that is uniquely identified by its |
| // span in the original matcher to the First set for the inner sequence `tt ...`. |
| // |
| // If two sequences have the same span in a matcher, then map that |
| // span to None (invalidating the mapping here and forcing the code to |
| // use a slow path). |
| first: FxHashMap<Span, Option<TokenSet>>, |
| } |
| |
| impl FirstSets { |
| fn new(tts: &[quoted::TokenTree]) -> FirstSets { |
| use quoted::TokenTree; |
| |
| let mut sets = FirstSets { first: FxHashMap::default() }; |
| build_recur(&mut sets, tts); |
| return sets; |
| |
| // walks backward over `tts`, returning the FIRST for `tts` |
| // and updating `sets` at the same time for all sequence |
| // substructure we find within `tts`. |
| fn build_recur(sets: &mut FirstSets, tts: &[TokenTree]) -> TokenSet { |
| let mut first = TokenSet::empty(); |
| for tt in tts.iter().rev() { |
| match *tt { |
| TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
| first.replace_with(tt.clone()); |
| } |
| TokenTree::Delimited(span, ref delimited) => { |
| build_recur(sets, &delimited.tts[..]); |
| first.replace_with(delimited.open_tt(span.open)); |
| } |
| TokenTree::Sequence(sp, ref seq_rep) => { |
| let subfirst = build_recur(sets, &seq_rep.tts[..]); |
| |
| match sets.first.entry(sp.entire()) { |
| Entry::Vacant(vac) => { |
| vac.insert(Some(subfirst.clone())); |
| } |
| Entry::Occupied(mut occ) => { |
| // if there is already an entry, then a span must have collided. |
| // This should not happen with typical macro_rules macros, |
| // but syntax extensions need not maintain distinct spans, |
| // so distinct syntax trees can be assigned the same span. |
| // In such a case, the map cannot be trusted; so mark this |
| // entry as unusable. |
| occ.insert(None); |
| } |
| } |
| |
| // If the sequence contents can be empty, then the first |
| // token could be the separator token itself. |
| |
| if let (Some(ref sep), true) = (seq_rep.separator.clone(), |
| subfirst.maybe_empty) { |
| first.add_one_maybe(TokenTree::Token(sp.entire(), sep.clone())); |
| } |
| |
| // Reverse scan: Sequence comes before `first`. |
| if subfirst.maybe_empty |
| || seq_rep.op == quoted::KleeneOp::ZeroOrMore |
| || seq_rep.op == quoted::KleeneOp::ZeroOrOne |
| { |
| // If sequence is potentially empty, then |
| // union them (preserving first emptiness). |
| first.add_all(&TokenSet { maybe_empty: true, ..subfirst }); |
| } else { |
| // Otherwise, sequence guaranteed |
| // non-empty; replace first. |
| first = subfirst; |
| } |
| } |
| } |
| } |
| |
| first |
| } |
| } |
| |
| // walks forward over `tts` until all potential FIRST tokens are |
| // identified. |
| fn first(&self, tts: &[quoted::TokenTree]) -> TokenSet { |
| use quoted::TokenTree; |
| |
| let mut first = TokenSet::empty(); |
| for tt in tts.iter() { |
| assert!(first.maybe_empty); |
| match *tt { |
| TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
| first.add_one(tt.clone()); |
| return first; |
| } |
| TokenTree::Delimited(span, ref delimited) => { |
| first.add_one(delimited.open_tt(span.open)); |
| return first; |
| } |
| TokenTree::Sequence(sp, ref seq_rep) => { |
| match self.first.get(&sp.entire()) { |
| Some(&Some(ref subfirst)) => { |
| |
| // If the sequence contents can be empty, then the first |
| // token could be the separator token itself. |
| |
| if let (Some(ref sep), true) = (seq_rep.separator.clone(), |
| subfirst.maybe_empty) { |
| first.add_one_maybe(TokenTree::Token(sp.entire(), sep.clone())); |
| } |
| |
| assert!(first.maybe_empty); |
| first.add_all(subfirst); |
| if subfirst.maybe_empty |
| || seq_rep.op == quoted::KleeneOp::ZeroOrMore |
| || seq_rep.op == quoted::KleeneOp::ZeroOrOne |
| { |
| // continue scanning for more first |
| // tokens, but also make sure we |
| // restore empty-tracking state |
| first.maybe_empty = true; |
| continue; |
| } else { |
| return first; |
| } |
| } |
| |
| Some(&None) => { |
| panic!("assume all sequences have (unique) spans for now"); |
| } |
| |
| None => { |
| panic!("We missed a sequence during FirstSets construction"); |
| } |
| } |
| } |
| } |
| } |
| |
| // we only exit the loop if `tts` was empty or if every |
| // element of `tts` matches the empty sequence. |
| assert!(first.maybe_empty); |
| first |
| } |
| } |
| |
| // A set of `quoted::TokenTree`s, which may include `TokenTree::Match`s |
| // (for macro-by-example syntactic variables). It also carries the |
| // `maybe_empty` flag; that is true if and only if the matcher can |
| // match an empty token sequence. |
| // |
| // The First set is computed on submatchers like `$($a:expr b),* $(c)* d`, |
| // which has corresponding FIRST = {$a:expr, c, d}. |
| // Likewise, `$($a:expr b),* $(c)+ d` has FIRST = {$a:expr, c}. |
| // |
| // (Notably, we must allow for *-op to occur zero times.) |
| #[derive(Clone, Debug)] |
| struct TokenSet { |
| tokens: Vec<quoted::TokenTree>, |
| maybe_empty: bool, |
| } |
| |
| impl TokenSet { |
| // Returns a set for the empty sequence. |
| fn empty() -> Self { TokenSet { tokens: Vec::new(), maybe_empty: true } } |
| |
| // Returns the set `{ tok }` for the single-token (and thus |
| // non-empty) sequence [tok]. |
| fn singleton(tok: quoted::TokenTree) -> Self { |
| TokenSet { tokens: vec![tok], maybe_empty: false } |
| } |
| |
| // Changes self to be the set `{ tok }`. |
| // Since `tok` is always present, marks self as non-empty. |
| fn replace_with(&mut self, tok: quoted::TokenTree) { |
| self.tokens.clear(); |
| self.tokens.push(tok); |
| self.maybe_empty = false; |
| } |
| |
| // Changes self to be the empty set `{}`; meant for use when |
| // the particular token does not matter, but we want to |
| // record that it occurs. |
| fn replace_with_irrelevant(&mut self) { |
| self.tokens.clear(); |
| self.maybe_empty = false; |
| } |
| |
| // Adds `tok` to the set for `self`, marking sequence as non-empy. |
| fn add_one(&mut self, tok: quoted::TokenTree) { |
| if !self.tokens.contains(&tok) { |
| self.tokens.push(tok); |
| } |
| self.maybe_empty = false; |
| } |
| |
| // Adds `tok` to the set for `self`. (Leaves `maybe_empty` flag alone.) |
| fn add_one_maybe(&mut self, tok: quoted::TokenTree) { |
| if !self.tokens.contains(&tok) { |
| self.tokens.push(tok); |
| } |
| } |
| |
| // Adds all elements of `other` to this. |
| // |
| // (Since this is a set, we filter out duplicates.) |
| // |
| // If `other` is potentially empty, then preserves the previous |
| // setting of the empty flag of `self`. If `other` is guaranteed |
| // non-empty, then `self` is marked non-empty. |
| fn add_all(&mut self, other: &Self) { |
| for tok in &other.tokens { |
| if !self.tokens.contains(tok) { |
| self.tokens.push(tok.clone()); |
| } |
| } |
| if !other.maybe_empty { |
| self.maybe_empty = false; |
| } |
| } |
| } |
| |
| // Checks that `matcher` is internally consistent and that it |
| // can legally by followed by a token N, for all N in `follow`. |
| // (If `follow` is empty, then it imposes no constraint on |
| // the `matcher`.) |
| // |
| // Returns the set of NT tokens that could possibly come last in |
| // `matcher`. (If `matcher` matches the empty sequence, then |
| // `maybe_empty` will be set to true.) |
| // |
| // Requires that `first_sets` is pre-computed for `matcher`; |
| // see `FirstSets::new`. |
| fn check_matcher_core(sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| first_sets: &FirstSets, |
| matcher: &[quoted::TokenTree], |
| follow: &TokenSet) -> TokenSet { |
| use quoted::TokenTree; |
| |
| let mut last = TokenSet::empty(); |
| |
| // 2. For each token and suffix [T, SUFFIX] in M: |
| // ensure that T can be followed by SUFFIX, and if SUFFIX may be empty, |
| // then ensure T can also be followed by any element of FOLLOW. |
| 'each_token: for i in 0..matcher.len() { |
| let token = &matcher[i]; |
| let suffix = &matcher[i+1..]; |
| |
| let build_suffix_first = || { |
| let mut s = first_sets.first(suffix); |
| if s.maybe_empty { s.add_all(follow); } |
| s |
| }; |
| |
| // (we build `suffix_first` on demand below; you can tell |
| // which cases are supposed to fall through by looking for the |
| // initialization of this variable.) |
| let suffix_first; |
| |
| // First, update `last` so that it corresponds to the set |
| // of NT tokens that might end the sequence `... token`. |
| match *token { |
| TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl(..) => { |
| let can_be_followed_by_any; |
| if let Err(bad_frag) = has_legal_fragment_specifier(sess, features, attrs, token) { |
| let msg = format!("invalid fragment specifier `{}`", bad_frag); |
| sess.span_diagnostic.struct_span_err(token.span(), &msg) |
| .help(VALID_FRAGMENT_NAMES_MSG) |
| .emit(); |
| // (This eliminates false positives and duplicates |
| // from error messages.) |
| can_be_followed_by_any = true; |
| } else { |
| can_be_followed_by_any = token_can_be_followed_by_any(token); |
| } |
| |
| if can_be_followed_by_any { |
| // don't need to track tokens that work with any, |
| last.replace_with_irrelevant(); |
| // ... and don't need to check tokens that can be |
| // followed by anything against SUFFIX. |
| continue 'each_token; |
| } else { |
| last.replace_with(token.clone()); |
| suffix_first = build_suffix_first(); |
| } |
| } |
| TokenTree::Delimited(span, ref d) => { |
| let my_suffix = TokenSet::singleton(d.close_tt(span.close)); |
| check_matcher_core(sess, features, attrs, first_sets, &d.tts, &my_suffix); |
| // don't track non NT tokens |
| last.replace_with_irrelevant(); |
| |
| // also, we don't need to check delimited sequences |
| // against SUFFIX |
| continue 'each_token; |
| } |
| TokenTree::Sequence(sp, ref seq_rep) => { |
| suffix_first = build_suffix_first(); |
| // The trick here: when we check the interior, we want |
| // to include the separator (if any) as a potential |
| // (but not guaranteed) element of FOLLOW. So in that |
| // case, we make a temp copy of suffix and stuff |
| // delimiter in there. |
| // |
| // FIXME: Should I first scan suffix_first to see if |
| // delimiter is already in it before I go through the |
| // work of cloning it? But then again, this way I may |
| // get a "tighter" span? |
| let mut new; |
| let my_suffix = if let Some(ref u) = seq_rep.separator { |
| new = suffix_first.clone(); |
| new.add_one_maybe(TokenTree::Token(sp.entire(), u.clone())); |
| &new |
| } else { |
| &suffix_first |
| }; |
| |
| // At this point, `suffix_first` is built, and |
| // `my_suffix` is some TokenSet that we can use |
| // for checking the interior of `seq_rep`. |
| let next = check_matcher_core(sess, |
| features, |
| attrs, |
| first_sets, |
| &seq_rep.tts, |
| my_suffix); |
| if next.maybe_empty { |
| last.add_all(&next); |
| } else { |
| last = next; |
| } |
| |
| // the recursive call to check_matcher_core already ran the 'each_last |
| // check below, so we can just keep going forward here. |
| continue 'each_token; |
| } |
| } |
| |
| // (`suffix_first` guaranteed initialized once reaching here.) |
| |
| // Now `last` holds the complete set of NT tokens that could |
| // end the sequence before SUFFIX. Check that every one works with `suffix`. |
| 'each_last: for token in &last.tokens { |
| if let TokenTree::MetaVarDecl(_, ref name, ref frag_spec) = *token { |
| for next_token in &suffix_first.tokens { |
| match is_in_follow(next_token, &frag_spec.as_str()) { |
| IsInFollow::Invalid(msg, help) => { |
| sess.span_diagnostic.struct_span_err(next_token.span(), &msg) |
| .help(help).emit(); |
| // don't bother reporting every source of |
| // conflict for a particular element of `last`. |
| continue 'each_last; |
| } |
| IsInFollow::Yes => {} |
| IsInFollow::No(ref possible) => { |
| let may_be = if last.tokens.len() == 1 && |
| suffix_first.tokens.len() == 1 |
| { |
| "is" |
| } else { |
| "may be" |
| }; |
| |
| let sp = next_token.span(); |
| let mut err = sess.span_diagnostic.struct_span_err( |
| sp, |
| &format!("`${name}:{frag}` {may_be} followed by `{next}`, which \ |
| is not allowed for `{frag}` fragments", |
| name=name, |
| frag=frag_spec, |
| next=quoted_tt_to_string(next_token), |
| may_be=may_be), |
| ); |
| err.span_label( |
| sp, |
| format!("not allowed after `{}` fragments", frag_spec), |
| ); |
| let msg = "allowed there are: "; |
| match &possible[..] { |
| &[] => {} |
| &[t] => { |
| err.note(&format!( |
| "only {} is allowed after `{}` fragments", |
| t, |
| frag_spec, |
| )); |
| } |
| ts => { |
| err.note(&format!( |
| "{}{} or {}", |
| msg, |
| ts[..ts.len() - 1].iter().map(|s| *s) |
| .collect::<Vec<_>>().join(", "), |
| ts[ts.len() - 1], |
| )); |
| } |
| } |
| err.emit(); |
| } |
| } |
| } |
| } |
| } |
| } |
| last |
| } |
| |
| fn token_can_be_followed_by_any(tok: "ed::TokenTree) -> bool { |
| if let quoted::TokenTree::MetaVarDecl(_, _, frag_spec) = *tok { |
| frag_can_be_followed_by_any(&frag_spec.as_str()) |
| } else { |
| // (Non NT's can always be followed by anthing in matchers.) |
| true |
| } |
| } |
| |
| /// Returns `true` if a fragment of type `frag` can be followed by any sort of |
| /// token. We use this (among other things) as a useful approximation |
| /// for when `frag` can be followed by a repetition like `$(...)*` or |
| /// `$(...)+`. In general, these can be a bit tricky to reason about, |
| /// so we adopt a conservative position that says that any fragment |
| /// specifier which consumes at most one token tree can be followed by |
| /// a fragment specifier (indeed, these fragments can be followed by |
| /// ANYTHING without fear of future compatibility hazards). |
| fn frag_can_be_followed_by_any(frag: &str) -> bool { |
| match frag { |
| "item" | // always terminated by `}` or `;` |
| "block" | // exactly one token tree |
| "ident" | // exactly one token tree |
| "literal" | // exactly one token tree |
| "meta" | // exactly one token tree |
| "lifetime" | // exactly one token tree |
| "tt" => // exactly one token tree |
| true, |
| |
| _ => |
| false, |
| } |
| } |
| |
| enum IsInFollow { |
| Yes, |
| No(Vec<&'static str>), |
| Invalid(String, &'static str), |
| } |
| |
| /// Returns `true` if `frag` can legally be followed by the token `tok`. For |
| /// fragments that can consume an unbounded number of tokens, `tok` |
| /// must be within a well-defined follow set. This is intended to |
| /// guarantee future compatibility: for example, without this rule, if |
| /// we expanded `expr` to include a new binary operator, we might |
| /// break macros that were relying on that binary operator as a |
| /// separator. |
| // when changing this do not forget to update doc/book/macros.md! |
| fn is_in_follow(tok: "ed::TokenTree, frag: &str) -> IsInFollow { |
| use quoted::TokenTree; |
| |
| if let TokenTree::Token(_, token::CloseDelim(_)) = *tok { |
| // closing a token tree can never be matched by any fragment; |
| // iow, we always require that `(` and `)` match, etc. |
| IsInFollow::Yes |
| } else { |
| match frag { |
| "item" => { |
| // since items *must* be followed by either a `;` or a `}`, we can |
| // accept anything after them |
| IsInFollow::Yes |
| }, |
| "block" => { |
| // anything can follow block, the braces provide an easy boundary to |
| // maintain |
| IsInFollow::Yes |
| }, |
| "stmt" | "expr" => { |
| let tokens = vec!["`=>`", "`,`", "`;`"]; |
| match *tok { |
| TokenTree::Token(_, ref tok) => match *tok { |
| FatArrow | Comma | Semi => IsInFollow::Yes, |
| _ => IsInFollow::No(tokens), |
| }, |
| _ => IsInFollow::No(tokens), |
| } |
| }, |
| "pat" => { |
| let tokens = vec!["`=>`", "`,`", "`=`", "`|`", "`if`", "`in`"]; |
| match *tok { |
| TokenTree::Token(_, ref tok) => match *tok { |
| FatArrow | Comma | Eq | BinOp(token::Or) => IsInFollow::Yes, |
| Ident(i, false) if i.name == "if" || i.name == "in" => IsInFollow::Yes, |
| _ => IsInFollow::No(tokens), |
| }, |
| _ => IsInFollow::No(tokens), |
| } |
| }, |
| "path" | "ty" => { |
| let tokens = vec![ |
| "`{`", "`[`", "`=>`", "`,`", "`>`","`=`", "`:`", "`;`", "`|`", "`as`", |
| "`where`", |
| ]; |
| match *tok { |
| TokenTree::Token(_, ref tok) => match *tok { |
| OpenDelim(token::DelimToken::Brace) | |
| OpenDelim(token::DelimToken::Bracket) | |
| Comma | FatArrow | Colon | Eq | Gt | BinOp(token::Shr) | Semi | |
| BinOp(token::Or) => IsInFollow::Yes, |
| Ident(i, false) if i.name == "as" || i.name == "where" => IsInFollow::Yes, |
| _ => IsInFollow::No(tokens), |
| }, |
| TokenTree::MetaVarDecl(_, _, frag) if frag.name == "block" => IsInFollow::Yes, |
| _ => IsInFollow::No(tokens), |
| } |
| }, |
| "ident" | "lifetime" => { |
| // being a single token, idents and lifetimes are harmless |
| IsInFollow::Yes |
| }, |
| "literal" => { |
| // literals may be of a single token, or two tokens (negative numbers) |
| IsInFollow::Yes |
| }, |
| "meta" | "tt" => { |
| // being either a single token or a delimited sequence, tt is |
| // harmless |
| IsInFollow::Yes |
| }, |
| "vis" => { |
| // Explicitly disallow `priv`, on the off chance it comes back. |
| let tokens = vec!["`,`", "an ident", "a type"]; |
| match *tok { |
| TokenTree::Token(_, ref tok) => match *tok { |
| Comma => IsInFollow::Yes, |
| Ident(i, is_raw) if is_raw || i.name != "priv" => IsInFollow::Yes, |
| ref tok => if tok.can_begin_type() { |
| IsInFollow::Yes |
| } else { |
| IsInFollow::No(tokens) |
| } |
| }, |
| TokenTree::MetaVarDecl(_, _, frag) if frag.name == "ident" |
| || frag.name == "ty" |
| || frag.name == "path" => IsInFollow::Yes, |
| _ => IsInFollow::No(tokens), |
| } |
| }, |
| "" => IsInFollow::Yes, // keywords::Invalid |
| _ => IsInFollow::Invalid(format!("invalid fragment specifier `{}`", frag), |
| VALID_FRAGMENT_NAMES_MSG), |
| } |
| } |
| } |
| |
| fn has_legal_fragment_specifier(sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| tok: "ed::TokenTree) -> Result<(), String> { |
| debug!("has_legal_fragment_specifier({:?})", tok); |
| if let quoted::TokenTree::MetaVarDecl(_, _, ref frag_spec) = *tok { |
| let frag_name = frag_spec.as_str(); |
| let frag_span = tok.span(); |
| if !is_legal_fragment_specifier(sess, features, attrs, &frag_name, frag_span) { |
| return Err(frag_name.to_string()); |
| } |
| } |
| Ok(()) |
| } |
| |
| fn is_legal_fragment_specifier(_sess: &ParseSess, |
| _features: &Features, |
| _attrs: &[ast::Attribute], |
| frag_name: &str, |
| _frag_span: Span) -> bool { |
| /* |
| * If new fragment specifiers are invented in nightly, `_sess`, |
| * `_features`, `_attrs`, and `_frag_span` will be useful here |
| * for checking against feature gates. See past versions of |
| * this function. |
| */ |
| match frag_name { |
| "item" | "block" | "stmt" | "expr" | "pat" | "lifetime" | |
| "path" | "ty" | "ident" | "meta" | "tt" | "vis" | "literal" | |
| "" => true, |
| _ => false, |
| } |
| } |
| |
| fn quoted_tt_to_string(tt: "ed::TokenTree) -> String { |
| match *tt { |
| quoted::TokenTree::Token(_, ref tok) => crate::print::pprust::token_to_string(tok), |
| quoted::TokenTree::MetaVar(_, name) => format!("${}", name), |
| quoted::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind), |
| _ => panic!("unexpected quoted::TokenTree::{{Sequence or Delimited}} \ |
| in follow set checker"), |
| } |
| } |
