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Diffstat (limited to 'src/libsyntax/ext/mbe/macro_rules.rs')
| -rw-r--r-- | src/libsyntax/ext/mbe/macro_rules.rs | 1191 |
1 files changed, 0 insertions, 1191 deletions
diff --git a/src/libsyntax/ext/mbe/macro_rules.rs b/src/libsyntax/ext/mbe/macro_rules.rs deleted file mode 100644 index aec4a683141..00000000000 --- a/src/libsyntax/ext/mbe/macro_rules.rs +++ /dev/null @@ -1,1191 +0,0 @@ -use crate::ast; -use crate::attr::{self, TransparencyError}; -use crate::edition::Edition; -use crate::ext::base::{DummyResult, ExtCtxt, MacResult, TTMacroExpander}; -use crate::ext::base::{SyntaxExtension, SyntaxExtensionKind}; -use crate::ext::expand::{AstFragment, AstFragmentKind}; -use crate::ext::mbe; -use crate::ext::mbe::macro_check; -use crate::ext::mbe::macro_parser::parse; -use crate::ext::mbe::macro_parser::{Error, Failure, Success}; -use crate::ext::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedParseResult}; -use crate::ext::mbe::transcribe::transcribe; -use crate::feature_gate::Features; -use crate::parse::parser::Parser; -use crate::parse::token::TokenKind::*; -use crate::parse::token::{self, NtTT, Token}; -use crate::parse::{Directory, ParseSess}; -use crate::print::pprust; -use crate::symbol::{kw, sym, Symbol}; -use crate::tokenstream::{DelimSpan, TokenStream, TokenTree}; - -use errors::{DiagnosticBuilder, FatalError}; -use log::debug; -use syntax_pos::hygiene::Transparency; -use syntax_pos::Span; - -use rustc_data_structures::fx::FxHashMap; -use std::borrow::Cow; -use std::collections::hash_map::Entry; -use std::slice; - -use errors::Applicability; -use rustc_data_structures::sync::Lrc; - -const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \ - `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \ - `literal`, `path`, `meta`, `tt`, `item` and `vis`"; - -crate 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, -} - -crate fn annotate_err_with_kind( - err: &mut DiagnosticBuilder<'_>, - kind: AstFragmentKind, - span: Span, -) { - match kind { - AstFragmentKind::Ty => { - err.span_label(span, "this macro call doesn't expand to a type"); - } - AstFragmentKind::Pat => { - err.span_label(span, "this macro call doesn't expand to a pattern"); - } - _ => {} - }; -} - -impl<'a> ParserAnyMacro<'a> { - crate 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.token.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.token.span).is_real() { - e.span_label(site_span, "in this macro invocation"); - } - match kind { - AstFragmentKind::Pat if macro_ident.name == sym::vec => { - let mut suggestion = None; - if let Ok(code) = parser.sess.source_map().span_to_snippet(site_span) { - if let Some(bang) = code.find('!') { - suggestion = Some(code[bang + 1..].to_string()); - } - } - if let Some(suggestion) = suggestion { - e.span_suggestion( - site_span, - "use a slice pattern here instead", - suggestion, - Applicability::MachineApplicable, - ); - } else { - e.span_label( - site_span, - "use a slice pattern here instead", - ); - } - e.help("for more information, see https://doc.rust-lang.org/edition-guide/\ - rust-2018/slice-patterns.html"); - } - _ => annotate_err_with_kind(&mut e, kind, site_span), - }; - 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, - span: Span, - transparency: Transparency, - lhses: Vec<mbe::TokenTree>, - rhses: Vec<mbe::TokenTree>, - valid: bool, -} - -impl TTMacroExpander for MacroRulesMacroExpander { - fn expand<'cx>( - &self, - cx: &'cx mut ExtCtxt<'_>, - sp: Span, - input: TokenStream, - ) -> Box<dyn MacResult + 'cx> { - if !self.valid { - return DummyResult::any(sp); - } - generic_extension( - cx, sp, self.span, self.name, self.transparency, 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: Span, - name: ast::Ident, - transparency: Transparency, - arg: TokenStream, - lhses: &[mbe::TokenTree], - rhses: &[mbe::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_failure: Option<(Token, &str)> = None; - - for (i, lhs) in lhses.iter().enumerate() { - // try each arm's matchers - let lhs_tt = match *lhs { - mbe::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 - mbe::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, &named_matches, rhs, transparency); - - // 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, None); - p.root_module_name = - cx.current_expansion.module.mod_path.last().map(|id| id.as_str().to_string()); - p.last_type_ascription = cx.current_expansion.prior_type_ascription; - - 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(token, msg) => match best_failure { - Some((ref best_token, _)) if best_token.span.lo() >= token.span.lo() => {} - _ => best_failure = Some((token, msg)), - }, - Error(err_sp, ref msg) => cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..]), - } - } - - let (token, label) = best_failure.expect("ran no matchers"); - let span = token.span.substitute_dummy(sp); - let mut err = cx.struct_span_err(span, &parse_failure_msg(&token)); - err.span_label(span, label); - if !def_span.is_dummy() && cx.source_map().span_to_filename(def_span).is_real() { - err.span_label(cx.source_map().def_span(def_span), "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 { - mbe::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 item into a syntax extension. -pub fn compile_declarative_macro( - sess: &ParseSess, - features: &Features, - def: &ast::Item, - edition: Edition, -) -> SyntaxExtension { - let diag = &sess.span_diagnostic; - let lhs_nm = ast::Ident::new(sym::lhs, def.span); - let rhs_nm = ast::Ident::new(sym::rhs, def.span); - let tt_spec = ast::Ident::new(sym::tt, def.span); - - // Parse the macro_rules! invocation - let body = match def.kind { - 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![ - mbe::TokenTree::Sequence( - DelimSpan::dummy(), - Lrc::new(mbe::SequenceRepetition { - tts: vec![ - mbe::TokenTree::MetaVarDecl(def.span, lhs_nm, tt_spec), - mbe::TokenTree::token(token::FatArrow, def.span), - mbe::TokenTree::MetaVarDecl(def.span, rhs_nm, tt_spec), - ], - separator: Some(Token::new( - if body.legacy { token::Semi } else { token::Comma }, - def.span, - )), - kleene: mbe::KleeneToken::new(mbe::KleeneOp::OneOrMore, def.span), - num_captures: 2, - }), - ), - // to phase into semicolon-termination instead of semicolon-separation - mbe::TokenTree::Sequence( - DelimSpan::dummy(), - Lrc::new(mbe::SequenceRepetition { - tts: vec![mbe::TokenTree::token( - if body.legacy { token::Semi } else { token::Comma }, - def.span, - )], - separator: None, - kleene: mbe::KleeneToken::new(mbe::KleeneOp::ZeroOrMore, def.span), - num_captures: 0, - }), - ), - ]; - - let argument_map = match parse(sess, body.stream(), &argument_gram, None, true) { - Success(m) => m, - Failure(token, msg) => { - let s = parse_failure_msg(&token); - let sp = token.span.substitute_dummy(def.span); - let mut err = sess.span_diagnostic.struct_span_fatal(sp, &s); - err.span_label(sp, msg); - 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 = mbe::quoted::parse( - tt.clone().into(), - true, - sess, - ) - .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<mbe::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 mbe::quoted::parse( - tt.clone().into(), - false, - sess, - ) - .pop() - .unwrap(); - } - } - sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") - }) - .collect::<Vec<mbe::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, slice::from_ref(lhs)); - } - - // We use CRATE_NODE_ID instead of `def.id` otherwise we may emit buffered lints for a node id - // that is not lint-checked and trigger the "failed to process buffered lint here" bug. - valid &= macro_check::check_meta_variables(sess, ast::CRATE_NODE_ID, def.span, &lhses, &rhses); - - let (transparency, transparency_error) = attr::find_transparency(&def.attrs, body.legacy); - match transparency_error { - Some(TransparencyError::UnknownTransparency(value, span)) => - diag.span_err(span, &format!("unknown macro transparency: `{}`", value)), - Some(TransparencyError::MultipleTransparencyAttrs(old_span, new_span)) => - diag.span_err(vec![old_span, new_span], "multiple macro transparency attributes"), - None => {} - } - - let expander: Box<_> = Box::new(MacroRulesMacroExpander { - name: def.ident, span: def.span, transparency, lhses, rhses, valid - }); - - SyntaxExtension::new( - sess, - SyntaxExtensionKind::LegacyBang(expander), - def.span, - Vec::new(), - edition, - def.ident.name, - &def.attrs, - ) -} - -fn check_lhs_nt_follows( - sess: &ParseSess, - features: &Features, - attrs: &[ast::Attribute], - lhs: &mbe::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 mbe::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: &[mbe::TokenTree]) -> bool { - use mbe::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 == sym::vis, - TokenTree::Sequence(_, ref sub_seq) => { - sub_seq.kleene.op == mbe::KleeneOp::ZeroOrMore - || sub_seq.kleene.op == mbe::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 -} - -fn check_rhs(sess: &ParseSess, rhs: &mbe::TokenTree) -> bool { - match *rhs { - mbe::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: &[mbe::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: &[mbe::TokenTree]) -> FirstSets { - use mbe::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(sep), true) = (&seq_rep.separator, subfirst.maybe_empty) { - first.add_one_maybe(TokenTree::Token(sep.clone())); - } - - // Reverse scan: Sequence comes before `first`. - if subfirst.maybe_empty - || seq_rep.kleene.op == mbe::KleeneOp::ZeroOrMore - || seq_rep.kleene.op == mbe::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: &[mbe::TokenTree]) -> TokenSet { - use mbe::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) => { - let subfirst_owned; - let subfirst = match self.first.get(&sp.entire()) { - Some(&Some(ref subfirst)) => subfirst, - Some(&None) => { - subfirst_owned = self.first(&seq_rep.tts[..]); - &subfirst_owned - } - None => { - panic!("We missed a sequence during FirstSets construction"); - } - }; - - // If the sequence contents can be empty, then the first - // token could be the separator token itself. - if let (Some(sep), true) = (&seq_rep.separator, subfirst.maybe_empty) { - first.add_one_maybe(TokenTree::Token(sep.clone())); - } - - assert!(first.maybe_empty); - first.add_all(subfirst); - if subfirst.maybe_empty - || seq_rep.kleene.op == mbe::KleeneOp::ZeroOrMore - || seq_rep.kleene.op == mbe::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; - } - } - } - } - - // 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 `mbe::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<mbe::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: mbe::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: mbe::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: mbe::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: mbe::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 be 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: &[mbe::TokenTree], - follow: &TokenSet, -) -> TokenSet { - use mbe::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(_, 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(sep) = &seq_rep.separator { - new = suffix_first.clone(); - new.add_one_maybe(TokenTree::Token(sep.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(_, name, frag_spec) = *token { - for next_token in &suffix_first.tokens { - match is_in_follow(next_token, frag_spec.name) { - 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(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!( - "`${name}:{frag}` {may_be} followed by `{next}`, which \ - is not allowed for `{frag}` fragments", - name = name, - frag = frag_spec, - next = quoted_tt_to_string(next_token), - may_be = may_be - ), - ); - err.span_label( - sp, - format!("not allowed after `{}` fragments", frag_spec), - ); - let msg = "allowed there are: "; - match possible { - &[] => {} - &[t] => { - err.note(&format!( - "only {} is allowed after `{}` fragments", - t, frag_spec, - )); - } - ts => { - err.note(&format!( - "{}{} or {}", - msg, - ts[..ts.len() - 1] - .iter() - .map(|s| *s) - .collect::<Vec<_>>() - .join(", "), - ts[ts.len() - 1], - )); - } - } - err.emit(); - } - } - } - } - } - } - last -} - -fn token_can_be_followed_by_any(tok: &mbe::TokenTree) -> bool { - if let mbe::TokenTree::MetaVarDecl(_, _, frag_spec) = *tok { - frag_can_be_followed_by_any(frag_spec.name) - } else { - // (Non NT's can always be followed by anthing in matchers.) - true - } -} - -/// Returns `true` if a fragment of type `frag` can be followed by any sort of -/// token. We use this (among other things) as a useful approximation -/// for when `frag` can be followed by a repetition like `$(...)*` 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: Symbol) -> bool { - match frag { - sym::item | // always terminated by `}` or `;` - sym::block | // exactly one token tree - sym::ident | // exactly one token tree - sym::literal | // exactly one token tree - sym::meta | // exactly one token tree - sym::lifetime | // exactly one token tree - sym::tt => // exactly one token tree - true, - - _ => - false, - } -} - -enum IsInFollow { - Yes, - No(&'static [&'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: &mbe::TokenTree, frag: Symbol) -> IsInFollow { - use mbe::TokenTree; - - if let TokenTree::Token(Token { kind: 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 { - sym::item => { - // since items *must* be followed by either a `;` or a `}`, we can - // accept anything after them - IsInFollow::Yes - } - sym::block => { - // anything can follow block, the braces provide an easy boundary to - // maintain - IsInFollow::Yes - } - sym::stmt | sym::expr => { - const TOKENS: &[&str] = &["`=>`", "`,`", "`;`"]; - match tok { - TokenTree::Token(token) => match token.kind { - FatArrow | Comma | Semi => IsInFollow::Yes, - _ => IsInFollow::No(TOKENS), - }, - _ => IsInFollow::No(TOKENS), - } - } - sym::pat => { - const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`|`", "`if`", "`in`"]; - match tok { - TokenTree::Token(token) => match token.kind { - FatArrow | Comma | Eq | BinOp(token::Or) => IsInFollow::Yes, - Ident(name, false) if name == kw::If || name == kw::In => IsInFollow::Yes, - _ => IsInFollow::No(TOKENS), - }, - _ => IsInFollow::No(TOKENS), - } - } - sym::path | sym::ty => { - const TOKENS: &[&str] = &[ - "`{`", "`[`", "`=>`", "`,`", "`>`", "`=`", "`:`", "`;`", "`|`", "`as`", - "`where`", - ]; - match tok { - TokenTree::Token(token) => match token.kind { - OpenDelim(token::DelimToken::Brace) - | OpenDelim(token::DelimToken::Bracket) - | Comma - | FatArrow - | Colon - | Eq - | Gt - | BinOp(token::Shr) - | Semi - | BinOp(token::Or) => IsInFollow::Yes, - Ident(name, false) if name == kw::As || name == kw::Where => { - IsInFollow::Yes - } - _ => IsInFollow::No(TOKENS), - }, - TokenTree::MetaVarDecl(_, _, frag) if frag.name == sym::block => { - IsInFollow::Yes - } - _ => IsInFollow::No(TOKENS), - } - } - sym::ident | sym::lifetime => { - // being a single token, idents and lifetimes are harmless - IsInFollow::Yes - } - sym::literal => { - // literals may be of a single token, or two tokens (negative numbers) - IsInFollow::Yes - } - sym::meta | sym::tt => { - // being either a single token or a delimited sequence, tt is - // harmless - IsInFollow::Yes - } - sym::vis => { - // Explicitly disallow `priv`, on the off chance it comes back. - const TOKENS: &[&str] = &["`,`", "an ident", "a type"]; - match tok { - TokenTree::Token(token) => match token.kind { - Comma => IsInFollow::Yes, - Ident(name, is_raw) if is_raw || name != kw::Priv => IsInFollow::Yes, - _ => { - if token.can_begin_type() { - IsInFollow::Yes - } else { - IsInFollow::No(TOKENS) - } - } - }, - TokenTree::MetaVarDecl(_, _, frag) - if frag.name == sym::ident - || frag.name == sym::ty - || frag.name == sym::path => - { - IsInFollow::Yes - } - _ => IsInFollow::No(TOKENS), - } - } - kw::Invalid => IsInFollow::Yes, - _ => IsInFollow::Invalid( - format!("invalid fragment specifier `{}`", frag), - VALID_FRAGMENT_NAMES_MSG, - ), - } - } -} - -fn has_legal_fragment_specifier( - sess: &ParseSess, - features: &Features, - attrs: &[ast::Attribute], - tok: &mbe::TokenTree, -) -> Result<(), String> { - debug!("has_legal_fragment_specifier({:?})", tok); - if let mbe::TokenTree::MetaVarDecl(_, _, ref frag_spec) = *tok { - let frag_span = tok.span(); - if !is_legal_fragment_specifier(sess, features, attrs, frag_spec.name, frag_span) { - return Err(frag_spec.to_string()); - } - } - Ok(()) -} - -fn is_legal_fragment_specifier( - _sess: &ParseSess, - _features: &Features, - _attrs: &[ast::Attribute], - frag_name: Symbol, - _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 { - sym::item - | sym::block - | sym::stmt - | sym::expr - | sym::pat - | sym::lifetime - | sym::path - | sym::ty - | sym::ident - | sym::meta - | sym::tt - | sym::vis - | sym::literal - | kw::Invalid => true, - _ => false, - } -} - -fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String { - match *tt { - mbe::TokenTree::Token(ref token) => crate::print::pprust::token_to_string(&token), - mbe::TokenTree::MetaVar(_, name) => format!("${}", name), - mbe::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind), - _ => panic!( - "unexpected mbe::TokenTree::{{Sequence or Delimited}} \ - in follow set checker" - ), - } -} - -impl TokenTree { - /// Use this token tree as a matcher to parse given tts. - fn parse(cx: &ExtCtxt<'_>, mtch: &[mbe::TokenTree], tts: TokenStream) - -> NamedParseResult { - // `None` is because we're not interpolating - let directory = Directory { - path: Cow::from(cx.current_expansion.module.directory.as_path()), - ownership: cx.current_expansion.directory_ownership, - }; - parse(cx.parse_sess(), tts, mtch, Some(directory), true) - } -} - -/// Generates an appropriate parsing failure message. For EOF, this is "unexpected end...". For -/// other tokens, this is "unexpected token...". -fn parse_failure_msg(tok: &Token) -> String { - match tok.kind { - token::Eof => "unexpected end of macro invocation".to_string(), - _ => format!( - "no rules expected the token `{}`", - pprust::token_to_string(tok), - ), - } -} |