From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- compiler/rustc_expand/src/mbe/macro_rules.rs | 1420 ++++++++++++++++++++++++++ 1 file changed, 1420 insertions(+) create mode 100644 compiler/rustc_expand/src/mbe/macro_rules.rs (limited to 'compiler/rustc_expand/src/mbe/macro_rules.rs') diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs new file mode 100644 index 000000000..f7e1575af --- /dev/null +++ b/compiler/rustc_expand/src/mbe/macro_rules.rs @@ -0,0 +1,1420 @@ +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::{Error, ErrorReported, Failure, Success, TtParser}; +use crate::mbe::macro_parser::{MatchedSeq, MatchedTokenTree, MatcherLoc}; +use crate::mbe::transcribe::transcribe; + +use rustc_ast as ast; +use rustc_ast::token::{self, Delimiter, NonterminalKind, Token, TokenKind, 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, FxIndexMap}; +use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; +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::source_map::SourceMap; +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; + +pub(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, +} + +pub(crate) fn annotate_err_with_kind(err: &mut Diagnostic, 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<'_, rustc_errors::ErrorGuaranteed>, + parser: &Parser<'_>, + orig_parser: &mut Parser<'_>, + site_span: Span, + arm_span: Span, + kind: AstFragmentKind, +) { + // FIXME(davidtwco): avoid depending on the error message text + if parser.token == token::Eof && e.message[0].0.expect_str().ends_with(", found ``") { + 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] = ( + rustc_errors::DiagnosticMessage::Str(format!( + "macro expansion ends with an incomplete expression: {}", + msg.0.expect_str().replace(", found ``", ""), + )), + 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(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", + ";", + Applicability::MaybeIncorrect, + ); + } + }, + _ => annotate_err_with_kind(&mut e, kind, site_span), + }; + e.emit(); +} + +impl<'a> ParserAnyMacro<'a> { + pub(crate) fn make(mut self: Box>, 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.create_snapshot_for_diagnostic(); + 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 { + node_id: NodeId, + name: Ident, + span: Span, + transparency: Transparency, + lhses: Vec>, + rhses: Vec, + valid: bool, +} + +impl TTMacroExpander for MacroRulesMacroExpander { + fn expand<'cx>( + &self, + cx: &'cx mut ExtCtxt<'_>, + sp: Span, + input: TokenStream, + ) -> Box { + if !self.valid { + return DummyResult::any(sp); + } + expand_macro( + cx, + sp, + self.span, + self.node_id, + self.name, + self.transparency, + input, + &self.lhses, + &self.rhses, + ) + } +} + +fn macro_rules_dummy_expander<'cx>( + _: &'cx mut ExtCtxt<'_>, + span: Span, + _: TokenStream, +) -> Box { + DummyResult::any(span) +} + +fn trace_macros_note(cx_expansions: &mut FxIndexMap>, 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); +} + +/// Expands the rules based macro defined by `lhses` and `rhses` for a given +/// input `arg`. +fn expand_macro<'cx>( + cx: &'cx mut ExtCtxt<'_>, + sp: Span, + def_span: Span, + node_id: NodeId, + name: Ident, + transparency: Transparency, + arg: TokenStream, + lhses: &[Vec], + rhses: &[mbe::TokenTree], +) -> Box { + let sess = &cx.sess.parse_sess; + // Macros defined in the current crate have a real node id, + // whereas macros from an external crate have a dummy id. + let is_local = node_id != DUMMY_NODE_ID; + + 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()); + + // Try each arm's matchers. + let mut tt_parser = TtParser::new(name); + for (i, lhs) in lhses.iter().enumerate() { + // 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 tt_parser.parse_tt(&mut Cow::Borrowed(&parser), lhs) { + 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, rhs_span): (&mbe::Delimited, DelimSpan) = match &rhses[i] { + mbe::TokenTree::Delimited(span, delimited) => (&delimited, *span), + _ => cx.span_bug(sp, "malformed macro rhs"), + }; + let arm_span = rhses[i].span(); + + let rhs_spans = rhs.tts.iter().map(|t| t.span()).collect::>(); + // rhs has holes ( `$id` and `$(...)` that need filled) + let mut tts = match transcribe(cx, &named_matches, &rhs, rhs_span, 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; + + if is_local { + cx.resolver.record_macro_rule_usage(node_id, i); + } + + // 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"); + } + annotate_doc_comment(&mut err, sess.source_map(), span); + // 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 { + let parser = parser_from_cx(sess, arg.clone()); + if let Success(_) = tt_parser.parse_tt(&mut Cow::Borrowed(&parser), lhs) { + if comma_span.is_dummy() { + err.note("you might be missing a comma"); + } else { + err.span_suggestion_short( + comma_span, + "missing comma here", + ", ", + 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, Vec<(usize, Span)>) { + 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 dummy_syn_ext = || (mk_syn_ext(Box::new(macro_rules_dummy_expander)), Vec::new()); + + 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(), + 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(), + 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, + }, + ), + ]; + // Convert it into `MatcherLoc` form. + let argument_gram = mbe::macro_parser::compute_locs(&argument_gram); + + let parser = Parser::new(&sess.parse_sess, body, true, rustc_parse::MACRO_ARGUMENTS); + let mut tt_parser = + TtParser::new(Ident::with_dummy_span(if macro_rules { kw::MacroRules } else { kw::Macro })); + let argument_map = match tt_parser.parse_tt(&mut Cow::Borrowed(&parser), &argument_gram) { + Success(m) => m, + Failure(token, msg) => { + let s = parse_failure_msg(&token); + let sp = token.span.substitute_dummy(def.span); + let mut err = sess.parse_sess.span_diagnostic.struct_span_err(sp, &s); + err.span_label(sp, msg); + annotate_doc_comment(&mut err, sess.source_map(), sp); + err.emit(); + return dummy_syn_ext(); + } + Error(sp, msg) => { + sess.parse_sess + .span_diagnostic + .struct_span_err(sp.substitute_dummy(def.span), &msg) + .emit(); + return dummy_syn_ext(); + } + ErrorReported => { + return dummy_syn_ext(); + } + }; + + 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 MatchedTokenTree(ref tt) = *m { + let tt = mbe::quoted::parse( + TokenStream::new(vec![tt.clone()]), + true, + &sess.parse_sess, + def.id, + features, + edition, + ) + .pop() + .unwrap(); + valid &= check_lhs_nt_follows(&sess.parse_sess, &def, &tt); + return tt; + } + sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") + }) + .collect::>(), + _ => 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 MatchedTokenTree(ref tt) = *m { + return mbe::quoted::parse( + TokenStream::new(vec![tt.clone()]), + false, + &sess.parse_sess, + def.id, + features, + edition, + ) + .pop() + .unwrap(); + } + sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs") + }) + .collect::>(), + _ => 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 => {} + } + + // Compute the spans of the macro rules for unused rule linting. + // To avoid warning noise, only consider the rules of this + // macro for the lint, if all rules are valid. + // Also, we are only interested in non-foreign macros. + let rule_spans = if valid && def.id != DUMMY_NODE_ID { + lhses + .iter() + .zip(rhses.iter()) + .enumerate() + // If the rhs contains an invocation like compile_error!, + // don't consider the rule for the unused rule lint. + .filter(|(_idx, (_lhs, rhs))| !has_compile_error_macro(rhs)) + // We only take the span of the lhs here, + // so that the spans of created warnings are smaller. + .map(|(idx, (lhs, _rhs))| (idx, lhs.span())) + .collect::>() + } else { + Vec::new() + }; + + // Convert the lhses into `MatcherLoc` form, which is better for doing the + // actual matching. Unless the matcher is invalid. + let lhses = if valid { + lhses + .iter() + .map(|lhs| { + // Ignore the delimiters around the matcher. + match lhs { + mbe::TokenTree::Delimited(_, delimited) => { + mbe::macro_parser::compute_locs(&delimited.tts) + } + _ => sess.parse_sess.span_diagnostic.span_bug(def.span, "malformed macro lhs"), + } + }) + .collect() + } else { + vec![] + }; + + let expander = Box::new(MacroRulesMacroExpander { + name: def.ident, + span: def.span, + node_id: def.id, + transparency, + lhses, + rhses, + valid, + }); + (mk_syn_ext(expander), rule_spans) +} + +#[derive(SessionSubdiagnostic)] +enum ExplainDocComment { + #[label(expand::explain_doc_comment_inner)] + Inner { + #[primary_span] + span: Span, + }, + #[label(expand::explain_doc_comment_outer)] + Outer { + #[primary_span] + span: Span, + }, +} + +fn annotate_doc_comment( + err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>, + sm: &SourceMap, + span: Span, +) { + if let Ok(src) = sm.span_to_snippet(span) { + if src.starts_with("///") || src.starts_with("/**") { + err.subdiagnostic(ExplainDocComment::Outer { span }); + } else if src.starts_with("//!") || src.starts_with("/*!") { + err.subdiagnostic(ExplainDocComment::Inner { span }); + } + } +} + +fn check_lhs_nt_follows(sess: &ParseSess, 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(_, delimited) = lhs { + check_matcher(sess, def, &delimited.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::MetaVarExpr(..) => (), + 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, 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, def, &first_sets, matcher, &empty_suffix); + err == sess.span_diagnostic.err_count() +} + +fn has_compile_error_macro(rhs: &mbe::TokenTree) -> bool { + match rhs { + mbe::TokenTree::Delimited(_sp, d) => { + let has_compile_error = d.tts.array_windows::<3>().any(|[ident, bang, args]| { + if let mbe::TokenTree::Token(ident) = ident && + let TokenKind::Ident(ident, _) = ident.kind && + ident == sym::compile_error && + let mbe::TokenTree::Token(bang) = bang && + let TokenKind::Not = bang.kind && + let mbe::TokenTree::Delimited(_, del) = args && + del.delim != Delimiter::Invisible + { + true + } else { + false + } + }); + if has_compile_error { true } else { d.tts.iter().any(has_compile_error_macro) } + } + _ => false, + } +} + +// `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<'tt> { + // 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>>, +} + +impl<'tt> FirstSets<'tt> { + fn new(tts: &'tt [mbe::TokenTree]) -> FirstSets<'tt> { + 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<'tt>(sets: &mut FirstSets<'tt>, tts: &'tt [TokenTree]) -> TokenSet<'tt> { + let mut first = TokenSet::empty(); + for tt in tts.iter().rev() { + match *tt { + TokenTree::Token(..) + | TokenTree::MetaVar(..) + | TokenTree::MetaVarDecl(..) + | TokenTree::MetaVarExpr(..) => { + first.replace_with(TtHandle::TtRef(tt)); + } + TokenTree::Delimited(span, ref delimited) => { + build_recur(sets, &delimited.tts); + first.replace_with(TtHandle::from_token_kind( + token::OpenDelim(delimited.delim), + 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(TtHandle::from_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: &'tt [mbe::TokenTree]) -> TokenSet<'tt> { + 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(..) + | TokenTree::MetaVarExpr(..) => { + first.add_one(TtHandle::TtRef(tt)); + return first; + } + TokenTree::Delimited(span, ref delimited) => { + first.add_one(TtHandle::from_token_kind( + token::OpenDelim(delimited.delim), + 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(TtHandle::from_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 + } +} + +// Most `mbe::TokenTree`s are pre-existing in the matcher, but some are defined +// implicitly, such as opening/closing delimiters and sequence repetition ops. +// This type encapsulates both kinds. It implements `Clone` while avoiding the +// need for `mbe::TokenTree` to implement `Clone`. +#[derive(Debug)] +enum TtHandle<'tt> { + /// This is used in most cases. + TtRef(&'tt mbe::TokenTree), + + /// This is only used for implicit token trees. The `mbe::TokenTree` *must* + /// be `mbe::TokenTree::Token`. No other variants are allowed. We store an + /// `mbe::TokenTree` rather than a `Token` so that `get()` can return a + /// `&mbe::TokenTree`. + Token(mbe::TokenTree), +} + +impl<'tt> TtHandle<'tt> { + fn from_token(tok: Token) -> Self { + TtHandle::Token(mbe::TokenTree::Token(tok)) + } + + fn from_token_kind(kind: TokenKind, span: Span) -> Self { + TtHandle::from_token(Token::new(kind, span)) + } + + // Get a reference to a token tree. + fn get(&'tt self) -> &'tt mbe::TokenTree { + match self { + TtHandle::TtRef(tt) => tt, + TtHandle::Token(token_tt) => &token_tt, + } + } +} + +impl<'tt> PartialEq for TtHandle<'tt> { + fn eq(&self, other: &TtHandle<'tt>) -> bool { + self.get() == other.get() + } +} + +impl<'tt> Clone for TtHandle<'tt> { + fn clone(&self) -> Self { + match self { + TtHandle::TtRef(tt) => TtHandle::TtRef(tt), + + // This variant *must* contain a `mbe::TokenTree::Token`, and not + // any other variant of `mbe::TokenTree`. + TtHandle::Token(mbe::TokenTree::Token(tok)) => { + TtHandle::Token(mbe::TokenTree::Token(tok.clone())) + } + + _ => unreachable!(), + } + } +} + +// 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<'tt> { + tokens: Vec>, + maybe_empty: bool, +} + +impl<'tt> TokenSet<'tt> { + // 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(tt: TtHandle<'tt>) -> Self { + TokenSet { tokens: vec![tt], 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, tt: TtHandle<'tt>) { + self.tokens.clear(); + self.tokens.push(tt); + 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, tt: TtHandle<'tt>) { + if !self.tokens.contains(&tt) { + self.tokens.push(tt); + } + self.maybe_empty = false; + } + + // Adds `tok` to the set for `self`. (Leaves `maybe_empty` flag alone.) + fn add_one_maybe(&mut self, tt: TtHandle<'tt>) { + if !self.tokens.contains(&tt) { + self.tokens.push(tt); + } + } + + // 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 tt in &other.tokens { + if !self.tokens.contains(tt) { + self.tokens.push(tt.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<'tt>( + sess: &ParseSess, + def: &ast::Item, + first_sets: &FirstSets<'tt>, + matcher: &'tt [mbe::TokenTree], + follow: &TokenSet<'tt>, +) -> TokenSet<'tt> { + 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(..) + | TokenTree::MetaVarExpr(..) => { + 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(TtHandle::TtRef(token)); + suffix_first = build_suffix_first(); + } + } + TokenTree::Delimited(span, ref d) => { + let my_suffix = TokenSet::singleton(TtHandle::from_token_kind( + token::CloseDelim(d.delim), + span.close, + )); + check_matcher_core(sess, 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(TtHandle::from_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, 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 tt in &last.tokens { + if let &TokenTree::MetaVarDecl(span, name, Some(kind)) = tt.get() { + for next_token in &suffix_first.tokens { + let next_token = next_token.get(); + + // 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)); + + if kind == NonterminalKind::PatWithOr + && sess.edition.rust_2021() + && next_token.is_token(&BinOp(token::BinOpToken::Or)) + { + let suggestion = quoted_tt_to_string(&TokenTree::MetaVarDecl( + span, + name, + Some(NonterminalKind::PatParam { inferred: false }), + )); + err.span_suggestion( + span, + "try a `pat_param` fragment specifier instead", + suggestion, + Applicability::MaybeIncorrect, + ); + } + + 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::>() + .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(Delimiter::Brace) + | OpenDelim(Delimiter::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),), + } +} -- cgit v1.2.3