| use crate::base::{DummyResult, ExtCtxt, MacResult, TTMacroExpander}; |
| use crate::base::{SyntaxExtension, SyntaxExtensionKind}; |
| use crate::expand::{ensure_complete_parse, parse_ast_fragment, AstFragment, AstFragmentKind}; |
| use crate::mbe; |
| use crate::mbe::macro_check; |
| use crate::mbe::macro_parser::parse_tt; |
| use crate::mbe::macro_parser::{Error, ErrorReported, Failure, Success}; |
| use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq}; |
| use crate::mbe::transcribe::transcribe; |
| |
| use rustc_ast as ast; |
| use rustc_ast::token::{self, NonterminalKind, NtTT, Token, TokenKind::*}; |
| use rustc_ast::tokenstream::{DelimSpan, TokenStream}; |
| use rustc_ast::{NodeId, DUMMY_NODE_ID}; |
| use rustc_ast_pretty::pprust; |
| use rustc_attr::{self as attr, TransparencyError}; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_data_structures::sync::Lrc; |
| use rustc_errors::{Applicability, DiagnosticBuilder}; |
| use rustc_feature::Features; |
| use rustc_lint_defs::builtin::{ |
| RUST_2021_INCOMPATIBLE_OR_PATTERNS, SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, |
| }; |
| use rustc_lint_defs::BuiltinLintDiagnostics; |
| use rustc_parse::parser::Parser; |
| use rustc_session::parse::ParseSess; |
| use rustc_session::Session; |
| use rustc_span::edition::Edition; |
| use rustc_span::hygiene::Transparency; |
| use rustc_span::symbol::{kw, sym, Ident, MacroRulesNormalizedIdent}; |
| use rustc_span::Span; |
| |
| use std::borrow::Cow; |
| use std::collections::hash_map::Entry; |
| use std::{mem, slice}; |
| use tracing::debug; |
| |
| 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: Ident, |
| lint_node_id: NodeId, |
| is_trailing_mac: bool, |
| arm_span: Span, |
| /// Whether or not this macro is defined in the current crate |
| is_local: bool, |
| } |
| |
| 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"); |
| } |
| _ => {} |
| }; |
| } |
| |
| fn emit_frag_parse_err( |
| mut e: DiagnosticBuilder<'_>, |
| parser: &Parser<'_>, |
| orig_parser: &mut Parser<'_>, |
| site_span: Span, |
| arm_span: Span, |
| kind: AstFragmentKind, |
| ) { |
| 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().is_imported(arm_span) { |
| e.span_label(arm_span, "in this macro arm"); |
| } |
| } else if parser.sess.source_map().is_imported(parser.token.span) { |
| e.span_label(site_span, "in this macro invocation"); |
| } |
| match kind { |
| // Try a statement if an expression is wanted but failed and suggest adding `;` to call. |
| AstFragmentKind::Expr => match parse_ast_fragment(orig_parser, AstFragmentKind::Stmts) { |
| Err(mut err) => err.cancel(), |
| Ok(_) => { |
| e.note( |
| "the macro call doesn't expand to an expression, but it can expand to a statement", |
| ); |
| e.span_suggestion_verbose( |
| site_span.shrink_to_hi(), |
| "add `;` to interpret the expansion as a statement", |
| ";".to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| }, |
| _ => annotate_err_with_kind(&mut e, kind, site_span), |
| }; |
| e.emit(); |
| } |
| |
| impl<'a> ParserAnyMacro<'a> { |
| crate fn make(mut self: Box<ParserAnyMacro<'a>>, kind: AstFragmentKind) -> AstFragment { |
| let ParserAnyMacro { |
| site_span, |
| macro_ident, |
| ref mut parser, |
| lint_node_id, |
| arm_span, |
| is_trailing_mac, |
| is_local, |
| } = *self; |
| let snapshot = &mut parser.clone(); |
| let fragment = match parse_ast_fragment(parser, kind) { |
| Ok(f) => f, |
| Err(err) => { |
| emit_frag_parse_err(err, parser, snapshot, site_span, arm_span, kind); |
| return kind.dummy(site_span); |
| } |
| }; |
| |
| // 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 { |
| if is_local { |
| parser.sess.buffer_lint_with_diagnostic( |
| SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, |
| parser.token.span, |
| lint_node_id, |
| "trailing semicolon in macro used in expression position", |
| BuiltinLintDiagnostics::TrailingMacro(is_trailing_mac, macro_ident), |
| ); |
| } |
| 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)); |
| ensure_complete_parse(parser, &path, kind.name(), site_span); |
| fragment |
| } |
| } |
| |
| struct MacroRulesMacroExpander { |
| name: Ident, |
| span: Span, |
| transparency: Transparency, |
| lhses: Vec<mbe::TokenTree>, |
| rhses: Vec<mbe::TokenTree>, |
| valid: bool, |
| is_local: 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, |
| self.is_local, |
| ) |
| } |
| } |
| |
| fn macro_rules_dummy_expander<'cx>( |
| _: &'cx mut ExtCtxt<'_>, |
| span: Span, |
| _: TokenStream, |
| ) -> Box<dyn MacResult + 'cx> { |
| DummyResult::any(span) |
| } |
| |
| fn trace_macros_note(cx_expansions: &mut FxHashMap<Span, Vec<String>>, sp: Span, message: String) { |
| let sp = sp.macro_backtrace().last().map_or(sp, |trace| trace.call_site); |
| 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: Ident, |
| transparency: Transparency, |
| arg: TokenStream, |
| lhses: &[mbe::TokenTree], |
| rhses: &[mbe::TokenTree], |
| is_local: bool, |
| ) -> Box<dyn MacResult + 'cx> { |
| let sess = &cx.sess.parse_sess; |
| |
| if cx.trace_macros() { |
| let msg = format!("expanding `{}! {{ {} }}`", name, pprust::tts_to_string(&arg)); |
| trace_macros_note(&mut cx.expansions, sp, msg); |
| } |
| |
| // Which arm's failure should we report? (the one furthest along) |
| let mut best_failure: Option<(Token, &str)> = None; |
| |
| // We create a base parser that can be used for the "black box" parts. |
| // Every iteration needs a fresh copy of that parser. However, the parser |
| // is not mutated on many of the iterations, particularly when dealing with |
| // macros like this: |
| // |
| // macro_rules! foo { |
| // ("a") => (A); |
| // ("b") => (B); |
| // ("c") => (C); |
| // // ... etc. (maybe hundreds more) |
| // } |
| // |
| // as seen in the `html5ever` benchmark. We use a `Cow` so that the base |
| // parser is only cloned when necessary (upon mutation). Furthermore, we |
| // reinitialize the `Cow` with the base parser at the start of every |
| // iteration, so that any mutated parsers are not reused. This is all quite |
| // hacky, but speeds up the `html5ever` benchmark significantly. (Issue |
| // 68836 suggests a more comprehensive but more complex change to deal with |
| // this situation.) |
| let parser = parser_from_cx(sess, arg.clone()); |
| |
| 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"), |
| }; |
| |
| // Take a snapshot of the state of pre-expansion gating at this point. |
| // This is used so that if a matcher is not `Success(..)`ful, |
| // then the spans which became gated when parsing the unsuccessful matcher |
| // are not recorded. On the first `Success(..)`ful matcher, the spans are merged. |
| let mut gated_spans_snapshot = mem::take(&mut *sess.gated_spans.spans.borrow_mut()); |
| |
| match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt, name) { |
| Success(named_matches) => { |
| // The matcher was `Success(..)`ful. |
| // Merge the gated spans from parsing the matcher with the pre-existing ones. |
| sess.gated_spans.merge(gated_spans_snapshot); |
| |
| 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 = match transcribe(cx, &named_matches, rhs, transparency) { |
| Ok(tts) => tts, |
| Err(mut err) => { |
| err.emit(); |
| return DummyResult::any(arm_span); |
| } |
| }; |
| |
| // 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, tt| { |
| let mut tt = tt.clone(); |
| let mut sp = rhs_spans[i]; |
| sp = sp.with_ctxt(tt.span().ctxt()); |
| tt.set_span(sp); |
| tt |
| }); |
| } |
| |
| if cx.trace_macros() { |
| let msg = format!("to `{}`", pprust::tts_to_string(&tts)); |
| trace_macros_note(&mut cx.expansions, sp, msg); |
| } |
| |
| let mut p = Parser::new(sess, tts, false, None); |
| p.last_type_ascription = cx.current_expansion.prior_type_ascription; |
| |
| // 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, |
| lint_node_id: cx.current_expansion.lint_node_id, |
| is_trailing_mac: cx.current_expansion.is_trailing_mac, |
| arm_span, |
| is_local, |
| }); |
| } |
| 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) => { |
| let span = err_sp.substitute_dummy(sp); |
| cx.struct_span_err(span, &msg).emit(); |
| return DummyResult::any(span); |
| } |
| ErrorReported => return DummyResult::any(sp), |
| } |
| |
| // The matcher was not `Success(..)`ful. |
| // Restore to the state before snapshotting and maybe try again. |
| mem::swap(&mut gated_spans_snapshot, &mut sess.gated_spans.spans.borrow_mut()); |
| } |
| drop(parser); |
| |
| 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().is_imported(def_span) { |
| err.span_label(cx.source_map().guess_head_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, |
| }; |
| if let Success(_) = |
| parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt, name) |
| { |
| 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: &Session, |
| features: &Features, |
| def: &ast::Item, |
| edition: Edition, |
| ) -> SyntaxExtension { |
| debug!("compile_declarative_macro: {:?}", def); |
| let mk_syn_ext = |expander| { |
| SyntaxExtension::new( |
| sess, |
| SyntaxExtensionKind::LegacyBang(expander), |
| def.span, |
| Vec::new(), |
| edition, |
| def.ident.name, |
| &def.attrs, |
| ) |
| }; |
| |
| let diag = &sess.parse_sess.span_diagnostic; |
| let lhs_nm = Ident::new(sym::lhs, def.span); |
| let rhs_nm = Ident::new(sym::rhs, def.span); |
| let tt_spec = Some(NonterminalKind::TT); |
| |
| // Parse the macro_rules! invocation |
| let (macro_rules, body) = match &def.kind { |
| ast::ItemKind::MacroDef(def) => (def.macro_rules, def.body.inner_tokens()), |
| _ => 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 macro_rules { 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 macro_rules { token::Semi } else { token::Comma }, |
| def.span, |
| )], |
| separator: None, |
| kleene: mbe::KleeneToken::new(mbe::KleeneOp::ZeroOrMore, def.span), |
| num_captures: 0, |
| }), |
| ), |
| ]; |
| |
| let parser = Parser::new(&sess.parse_sess, body, true, rustc_parse::MACRO_ARGUMENTS); |
| let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram, def.ident) { |
| Success(m) => m, |
| Failure(token, msg) => { |
| let s = parse_failure_msg(&token); |
| let sp = token.span.substitute_dummy(def.span); |
| sess.parse_sess.span_diagnostic.struct_span_err(sp, &s).span_label(sp, msg).emit(); |
| return mk_syn_ext(Box::new(macro_rules_dummy_expander)); |
| } |
| Error(sp, msg) => { |
| sess.parse_sess |
| .span_diagnostic |
| .struct_span_err(sp.substitute_dummy(def.span), &msg) |
| .emit(); |
| return mk_syn_ext(Box::new(macro_rules_dummy_expander)); |
| } |
| ErrorReported => { |
| return mk_syn_ext(Box::new(macro_rules_dummy_expander)); |
| } |
| }; |
| |
| let mut valid = true; |
| |
| // Extract the arguments: |
| let lhses = match argument_map[&MacroRulesNormalizedIdent::new(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.parse_sess, |
| def.id, |
| features, |
| edition, |
| ) |
| .pop() |
| .unwrap(); |
| valid &= check_lhs_nt_follows(&sess.parse_sess, features, &def, &tt); |
| return tt; |
| } |
| } |
| sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
| }) |
| .collect::<Vec<mbe::TokenTree>>(), |
| _ => sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs"), |
| }; |
| |
| let rhses = match argument_map[&MacroRulesNormalizedIdent::new(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.parse_sess, |
| def.id, |
| features, |
| edition, |
| ) |
| .pop() |
| .unwrap(); |
| } |
| } |
| sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") |
| }) |
| .collect::<Vec<mbe::TokenTree>>(), |
| _ => sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs"), |
| }; |
| |
| for rhs in &rhses { |
| valid &= check_rhs(&sess.parse_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.parse_sess, slice::from_ref(lhs)); |
| } |
| |
| valid &= macro_check::check_meta_variables(&sess.parse_sess, def.id, def.span, &lhses, &rhses); |
| |
| let (transparency, transparency_error) = attr::find_transparency(&def.attrs, macro_rules); |
| 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 => {} |
| } |
| |
| mk_syn_ext(Box::new(MacroRulesMacroExpander { |
| name: def.ident, |
| span: def.span, |
| transparency, |
| lhses, |
| rhses, |
| valid, |
| // Macros defined in the current crate have a real node id, |
| // whereas macros from an external crate have a dummy id. |
| is_local: def.id != DUMMY_NODE_ID, |
| })) |
| } |
| |
| fn check_lhs_nt_follows( |
| sess: &ParseSess, |
| features: &Features, |
| def: &ast::Item, |
| 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, def, &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(_, _, Some(NonterminalKind::Vis)) => true, |
| 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, |
| def: &ast::Item, |
| 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, def, &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)); |
| } |
| 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)); |
| 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, |
| def: &ast::Item, |
| 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(..) => { |
| if token_can_be_followed_by_any(token) { |
| // 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)); |
| check_matcher_core(sess, features, def, 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, def, 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`. |
| for token in &last.tokens { |
| if let TokenTree::MetaVarDecl(span, name, Some(kind)) = *token { |
| for next_token in &suffix_first.tokens { |
| // Check if the old pat is used and the next token is `|` |
| // to warn about incompatibility with Rust 2021. |
| // We only emit this lint if we're parsing the original |
| // definition of this macro_rules, not while (re)parsing |
| // the macro when compiling another crate that is using the |
| // macro. (See #86567.) |
| // Macros defined in the current crate have a real node id, |
| // whereas macros from an external crate have a dummy id. |
| if def.id != DUMMY_NODE_ID |
| && matches!(kind, NonterminalKind::PatParam { inferred: true }) |
| && matches!(next_token, TokenTree::Token(token) if token.kind == BinOp(token::BinOpToken::Or)) |
| { |
| // It is suggestion to use pat_param, for example: $x:pat -> $x:pat_param. |
| let suggestion = quoted_tt_to_string(&TokenTree::MetaVarDecl( |
| span, |
| name, |
| Some(NonterminalKind::PatParam { inferred: false }), |
| )); |
| sess.buffer_lint_with_diagnostic( |
| &RUST_2021_INCOMPATIBLE_OR_PATTERNS, |
| span, |
| ast::CRATE_NODE_ID, |
| "the meaning of the `pat` fragment specifier is changing in Rust 2021, which may affect this macro", |
| BuiltinLintDiagnostics::OrPatternsBackCompat(span, suggestion), |
| ); |
| } |
| match is_in_follow(next_token, kind) { |
| IsInFollow::Yes => {} |
| IsInFollow::No(possible) => { |
| let may_be = if last.tokens.len() == 1 && suffix_first.tokens.len() == 1 |
| { |
| "is" |
| } else { |
| "may be" |
| }; |
| |
| let sp = next_token.span(); |
| let mut err = sess.span_diagnostic.struct_span_err( |
| sp, |
| &format!( |
| "`${name}:{frag}` {may_be} followed by `{next}`, which \ |
| is not allowed for `{frag}` fragments", |
| name = name, |
| frag = kind, |
| next = quoted_tt_to_string(next_token), |
| may_be = may_be |
| ), |
| ); |
| err.span_label(sp, format!("not allowed after `{}` fragments", kind)); |
| let msg = "allowed there are: "; |
| match possible { |
| &[] => {} |
| &[t] => { |
| err.note(&format!( |
| "only {} is allowed after `{}` fragments", |
| t, kind, |
| )); |
| } |
| ts => { |
| err.note(&format!( |
| "{}{} or {}", |
| msg, |
| ts[..ts.len() - 1] |
| .iter() |
| .copied() |
| .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(_, _, Some(kind)) = *tok { |
| frag_can_be_followed_by_any(kind) |
| } else { |
| // (Non NT's can always be followed by anything 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(kind: NonterminalKind) -> bool { |
| matches!( |
| kind, |
| NonterminalKind::Item // always terminated by `}` or `;` |
| | NonterminalKind::Block // exactly one token tree |
| | NonterminalKind::Ident // exactly one token tree |
| | NonterminalKind::Literal // exactly one token tree |
| | NonterminalKind::Meta // exactly one token tree |
| | NonterminalKind::Lifetime // exactly one token tree |
| | NonterminalKind::TT // exactly one token tree |
| ) |
| } |
| |
| enum IsInFollow { |
| Yes, |
| No(&'static [&'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, kind: NonterminalKind) -> 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 kind { |
| NonterminalKind::Item => { |
| // since items *must* be followed by either a `;` or a `}`, we can |
| // accept anything after them |
| IsInFollow::Yes |
| } |
| NonterminalKind::Block => { |
| // anything can follow block, the braces provide an easy boundary to |
| // maintain |
| IsInFollow::Yes |
| } |
| NonterminalKind::Stmt | NonterminalKind::Expr => { |
| const TOKENS: &[&str] = &["`=>`", "`,`", "`;`"]; |
| match tok { |
| TokenTree::Token(token) => match token.kind { |
| FatArrow | Comma | Semi => IsInFollow::Yes, |
| _ => IsInFollow::No(TOKENS), |
| }, |
| _ => IsInFollow::No(TOKENS), |
| } |
| } |
| NonterminalKind::PatParam { .. } => { |
| 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), |
| } |
| } |
| NonterminalKind::PatWithOr { .. } => { |
| const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`if`", "`in`"]; |
| match tok { |
| TokenTree::Token(token) => match token.kind { |
| FatArrow | Comma | Eq => IsInFollow::Yes, |
| Ident(name, false) if name == kw::If || name == kw::In => IsInFollow::Yes, |
| _ => IsInFollow::No(TOKENS), |
| }, |
| _ => IsInFollow::No(TOKENS), |
| } |
| } |
| NonterminalKind::Path | NonterminalKind::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(_, _, Some(NonterminalKind::Block)) => IsInFollow::Yes, |
| _ => IsInFollow::No(TOKENS), |
| } |
| } |
| NonterminalKind::Ident | NonterminalKind::Lifetime => { |
| // being a single token, idents and lifetimes are harmless |
| IsInFollow::Yes |
| } |
| NonterminalKind::Literal => { |
| // literals may be of a single token, or two tokens (negative numbers) |
| IsInFollow::Yes |
| } |
| NonterminalKind::Meta | NonterminalKind::TT => { |
| // being either a single token or a delimited sequence, tt is |
| // harmless |
| IsInFollow::Yes |
| } |
| NonterminalKind::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( |
| _, |
| _, |
| Some(NonterminalKind::Ident | NonterminalKind::Ty | NonterminalKind::Path), |
| ) => IsInFollow::Yes, |
| _ => IsInFollow::No(TOKENS), |
| } |
| } |
| } |
| } |
| } |
| |
| fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String { |
| match *tt { |
| mbe::TokenTree::Token(ref token) => pprust::token_to_string(&token).into(), |
| mbe::TokenTree::MetaVar(_, name) => format!("${}", name), |
| mbe::TokenTree::MetaVarDecl(_, name, Some(kind)) => format!("${}:{}", name, kind), |
| mbe::TokenTree::MetaVarDecl(_, name, None) => format!("${}:", name), |
| _ => panic!( |
| "{}", |
| "unexpected mbe::TokenTree::{Sequence or Delimited} \ |
| in follow set checker" |
| ), |
| } |
| } |
| |
| fn parser_from_cx(sess: &ParseSess, tts: TokenStream) -> Parser<'_> { |
| Parser::new(sess, tts, true, rustc_parse::MACRO_ARGUMENTS) |
| } |
| |
| /// 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),), |
| } |
| } |
