use std::borrow::Cow; use std::collections::hash_map::Entry; use std::sync::Arc; use std::{mem, slice}; use ast::token::IdentIsRaw; use rustc_ast::token::NtPatKind::*; use rustc_ast::token::TokenKind::*; use rustc_ast::token::{self, Delimiter, NonterminalKind, Token, TokenKind}; use rustc_ast::tokenstream::{self, DelimSpan, TokenStream}; use rustc_ast::{self as ast, DUMMY_NODE_ID, NodeId}; use rustc_ast_pretty::pprust; use rustc_data_structures::fx::{FxHashMap, FxIndexMap}; use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan}; use rustc_feature::Features; use rustc_hir as hir; use rustc_hir::attrs::AttributeKind; use rustc_hir::def::MacroKinds; use rustc_hir::find_attr; use rustc_lint_defs::builtin::{ RUST_2021_INCOMPATIBLE_OR_PATTERNS, SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, }; use rustc_parse::exp; use rustc_parse::parser::{Parser, Recovery}; use rustc_session::Session; use rustc_session::parse::{ParseSess, feature_err}; use rustc_span::edition::Edition; use rustc_span::hygiene::Transparency; use rustc_span::{Ident, Span, Symbol, kw, sym}; use tracing::{debug, instrument, trace, trace_span}; use super::diagnostics::{FailedMacro, failed_to_match_macro}; use super::macro_parser::{NamedMatches, NamedParseResult}; use super::{SequenceRepetition, diagnostics}; use crate::base::{ AttrProcMacro, BangProcMacro, DummyResult, ExpandResult, ExtCtxt, MacResult, MacroExpanderResult, SyntaxExtension, SyntaxExtensionKind, TTMacroExpander, }; use crate::errors; use crate::expand::{AstFragment, AstFragmentKind, ensure_complete_parse, parse_ast_fragment}; use crate::mbe::macro_check::check_meta_variables; use crate::mbe::macro_parser::{Error, ErrorReported, Failure, MatcherLoc, Success, TtParser}; use crate::mbe::quoted::{RulePart, parse_one_tt}; use crate::mbe::transcribe::transcribe; use crate::mbe::{self, KleeneOp}; 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, } 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) => { let guar = diagnostics::emit_frag_parse_err( err, parser, snapshot, site_span, arm_span, kind, ); return kind.dummy(site_span, guar); } }; // 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.psess.buffer_lint( SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, parser.token.span, lint_node_id, errors::TrailingMacro { is_trailing: is_trailing_mac, name: 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 } #[instrument(skip(cx, tts))] pub(crate) fn from_tts<'cx>( cx: &'cx mut ExtCtxt<'a>, tts: TokenStream, site_span: Span, arm_span: Span, is_local: bool, macro_ident: Ident, ) -> Self { Self { parser: Parser::new(&cx.sess.psess, tts, None), // 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, macro_ident, lint_node_id: cx.current_expansion.lint_node_id, is_trailing_mac: cx.current_expansion.is_trailing_mac, arm_span, is_local, } } } pub(super) enum MacroRule { /// A function-style rule, for use with `m!()` Func { lhs: Vec, lhs_span: Span, rhs: mbe::TokenTree }, /// An attr rule, for use with `#[m]` Attr { args: Vec, args_span: Span, body: Vec, body_span: Span, rhs: mbe::TokenTree, }, /// A derive rule, for use with `#[m]` Derive { body: Vec, body_span: Span, rhs: mbe::TokenTree }, } pub struct MacroRulesMacroExpander { node_id: NodeId, name: Ident, span: Span, transparency: Transparency, kinds: MacroKinds, rules: Vec, } impl MacroRulesMacroExpander { pub fn get_unused_rule(&self, rule_i: usize) -> Option<(&Ident, MultiSpan)> { // If the rhs contains an invocation like `compile_error!`, don't report it as unused. let (span, rhs) = match self.rules[rule_i] { MacroRule::Func { lhs_span, ref rhs, .. } => (MultiSpan::from_span(lhs_span), rhs), MacroRule::Attr { args_span, body_span, ref rhs, .. } => { (MultiSpan::from_spans(vec![args_span, body_span]), rhs) } MacroRule::Derive { body_span, ref rhs, .. } => (MultiSpan::from_span(body_span), rhs), }; if has_compile_error_macro(rhs) { None } else { Some((&self.name, span)) } } pub fn kinds(&self) -> MacroKinds { self.kinds } pub fn expand_derive( &self, cx: &mut ExtCtxt<'_>, sp: Span, body: &TokenStream, ) -> Result { // This is similar to `expand_macro`, but they have very different signatures, and will // diverge further once derives support arguments. let Self { name, ref rules, node_id, .. } = *self; let psess = &cx.sess.psess; if cx.trace_macros() { let msg = format!("expanding `#[derive({name})] {}`", pprust::tts_to_string(body)); trace_macros_note(&mut cx.expansions, sp, msg); } match try_match_macro_derive(psess, name, body, rules, &mut NoopTracker) { Ok((rule_index, rule, named_matches)) => { let MacroRule::Derive { rhs, .. } = rule else { panic!("try_match_macro_derive returned non-derive rule"); }; let mbe::TokenTree::Delimited(rhs_span, _, rhs) = rhs else { cx.dcx().span_bug(sp, "malformed macro derive rhs"); }; let id = cx.current_expansion.id; let tts = transcribe(psess, &named_matches, rhs, *rhs_span, self.transparency, id) .map_err(|e| e.emit())?; if cx.trace_macros() { let msg = format!("to `{}`", pprust::tts_to_string(&tts)); trace_macros_note(&mut cx.expansions, sp, msg); } if is_defined_in_current_crate(node_id) { cx.resolver.record_macro_rule_usage(node_id, rule_index); } Ok(tts) } Err(CanRetry::No(guar)) => Err(guar), Err(CanRetry::Yes) => { let (_, guar) = failed_to_match_macro( cx.psess(), sp, self.span, name, FailedMacro::Derive, body, rules, ); cx.macro_error_and_trace_macros_diag(); Err(guar) } } } } impl TTMacroExpander for MacroRulesMacroExpander { fn expand<'cx>( &self, cx: &'cx mut ExtCtxt<'_>, sp: Span, input: TokenStream, ) -> MacroExpanderResult<'cx> { ExpandResult::Ready(expand_macro( cx, sp, self.span, self.node_id, self.name, self.transparency, input, &self.rules, )) } } impl AttrProcMacro for MacroRulesMacroExpander { fn expand( &self, cx: &mut ExtCtxt<'_>, sp: Span, args: TokenStream, body: TokenStream, ) -> Result { expand_macro_attr( cx, sp, self.span, self.node_id, self.name, self.transparency, args, body, &self.rules, ) } } struct DummyBang(ErrorGuaranteed); impl BangProcMacro for DummyBang { fn expand<'cx>( &self, _: &'cx mut ExtCtxt<'_>, _: Span, _: TokenStream, ) -> Result { Err(self.0) } } 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); } pub(super) trait Tracker<'matcher> { /// The contents of `ParseResult::Failure`. type Failure; /// Arm failed to match. If the token is `token::Eof`, it indicates an unexpected /// end of macro invocation. Otherwise, it indicates that no rules expected the given token. /// The usize is the approximate position of the token in the input token stream. fn build_failure(tok: Token, position: u32, msg: &'static str) -> Self::Failure; /// This is called before trying to match next MatcherLoc on the current token. fn before_match_loc(&mut self, _parser: &TtParser, _matcher: &'matcher MatcherLoc) {} /// This is called after an arm has been parsed, either successfully or unsuccessfully. When /// this is called, `before_match_loc` was called at least once (with a `MatcherLoc::Eof`). fn after_arm(&mut self, _in_body: bool, _result: &NamedParseResult) {} /// For tracing. fn description() -> &'static str; fn recovery() -> Recovery { Recovery::Forbidden } } /// A noop tracker that is used in the hot path of the expansion, has zero overhead thanks to /// monomorphization. pub(super) struct NoopTracker; impl<'matcher> Tracker<'matcher> for NoopTracker { type Failure = (); fn build_failure(_tok: Token, _position: u32, _msg: &'static str) -> Self::Failure {} fn description() -> &'static str { "none" } } /// Expands the rules based macro defined by `rules` for a given input `arg`. #[instrument(skip(cx, transparency, arg, rules))] fn expand_macro<'cx>( cx: &'cx mut ExtCtxt<'_>, sp: Span, def_span: Span, node_id: NodeId, name: Ident, transparency: Transparency, arg: TokenStream, rules: &[MacroRule], ) -> Box { let psess = &cx.sess.psess; if cx.trace_macros() { let msg = format!("expanding `{}! {{ {} }}`", name, pprust::tts_to_string(&arg)); trace_macros_note(&mut cx.expansions, sp, msg); } // Track nothing for the best performance. let try_success_result = try_match_macro(psess, name, &arg, rules, &mut NoopTracker); match try_success_result { Ok((rule_index, rule, named_matches)) => { let MacroRule::Func { rhs, .. } = rule else { panic!("try_match_macro returned non-func rule"); }; let mbe::TokenTree::Delimited(rhs_span, _, rhs) = rhs else { cx.dcx().span_bug(sp, "malformed macro rhs"); }; let arm_span = rhs_span.entire(); // rhs has holes ( `$id` and `$(...)` that need filled) let id = cx.current_expansion.id; let tts = match transcribe(psess, &named_matches, rhs, *rhs_span, transparency, id) { Ok(tts) => tts, Err(err) => { let guar = err.emit(); return DummyResult::any(arm_span, guar); } }; if cx.trace_macros() { let msg = format!("to `{}`", pprust::tts_to_string(&tts)); trace_macros_note(&mut cx.expansions, sp, msg); } let is_local = is_defined_in_current_crate(node_id); if is_local { cx.resolver.record_macro_rule_usage(node_id, rule_index); } // Let the context choose how to interpret the result. Weird, but useful for X-macros. Box::new(ParserAnyMacro::from_tts(cx, tts, sp, arm_span, is_local, name)) } Err(CanRetry::No(guar)) => { debug!("Will not retry matching as an error was emitted already"); DummyResult::any(sp, guar) } Err(CanRetry::Yes) => { // Retry and emit a better error. let (span, guar) = failed_to_match_macro( cx.psess(), sp, def_span, name, FailedMacro::Func, &arg, rules, ); cx.macro_error_and_trace_macros_diag(); DummyResult::any(span, guar) } } } /// Expands the rules based macro defined by `rules` for a given attribute `args` and `body`. #[instrument(skip(cx, transparency, args, body, rules))] fn expand_macro_attr( cx: &mut ExtCtxt<'_>, sp: Span, def_span: Span, node_id: NodeId, name: Ident, transparency: Transparency, args: TokenStream, body: TokenStream, rules: &[MacroRule], ) -> Result { let psess = &cx.sess.psess; // 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(&args), pprust::tts_to_string(&body), ); trace_macros_note(&mut cx.expansions, sp, msg); } // Track nothing for the best performance. match try_match_macro_attr(psess, name, &args, &body, rules, &mut NoopTracker) { Ok((i, rule, named_matches)) => { let MacroRule::Attr { rhs, .. } = rule else { panic!("try_macro_match_attr returned non-attr rule"); }; let mbe::TokenTree::Delimited(rhs_span, _, rhs) = rhs else { cx.dcx().span_bug(sp, "malformed macro rhs"); }; let id = cx.current_expansion.id; let tts = transcribe(psess, &named_matches, rhs, *rhs_span, transparency, id) .map_err(|e| e.emit())?; if cx.trace_macros() { let msg = format!("to `{}`", pprust::tts_to_string(&tts)); trace_macros_note(&mut cx.expansions, sp, msg); } if is_local { cx.resolver.record_macro_rule_usage(node_id, i); } Ok(tts) } Err(CanRetry::No(guar)) => Err(guar), Err(CanRetry::Yes) => { // Retry and emit a better error. let (_, guar) = failed_to_match_macro( cx.psess(), sp, def_span, name, FailedMacro::Attr(&args), &body, rules, ); cx.trace_macros_diag(); Err(guar) } } } pub(super) enum CanRetry { Yes, /// We are not allowed to retry macro expansion as a fatal error has been emitted already. No(ErrorGuaranteed), } /// Try expanding the macro. Returns the index of the successful arm and its named_matches if it was successful, /// and nothing if it failed. On failure, it's the callers job to use `track` accordingly to record all errors /// correctly. #[instrument(level = "debug", skip(psess, arg, rules, track), fields(tracking = %T::description()))] pub(super) fn try_match_macro<'matcher, T: Tracker<'matcher>>( psess: &ParseSess, name: Ident, arg: &TokenStream, rules: &'matcher [MacroRule], track: &mut T, ) -> Result<(usize, &'matcher MacroRule, NamedMatches), CanRetry> { // 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(psess, arg.clone(), T::recovery()); // Try each arm's matchers. let mut tt_parser = TtParser::new(name); for (i, rule) in rules.iter().enumerate() { let MacroRule::Func { lhs, .. } = rule else { continue }; let _tracing_span = trace_span!("Matching arm", %i); // 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 *psess.gated_spans.spans.borrow_mut()); let result = tt_parser.parse_tt(&mut Cow::Borrowed(&parser), lhs, track); track.after_arm(true, &result); match result { Success(named_matches) => { debug!("Parsed arm successfully"); // The matcher was `Success(..)`ful. // Merge the gated spans from parsing the matcher with the preexisting ones. psess.gated_spans.merge(gated_spans_snapshot); return Ok((i, rule, named_matches)); } Failure(_) => { trace!("Failed to match arm, trying the next one"); // Try the next arm. } Error(_, _) => { debug!("Fatal error occurred during matching"); // We haven't emitted an error yet, so we can retry. return Err(CanRetry::Yes); } ErrorReported(guarantee) => { debug!("Fatal error occurred and was reported during matching"); // An error has been reported already, we cannot retry as that would cause duplicate errors. return Err(CanRetry::No(guarantee)); } } // The matcher was not `Success(..)`ful. // Restore to the state before snapshotting and maybe try again. mem::swap(&mut gated_spans_snapshot, &mut psess.gated_spans.spans.borrow_mut()); } Err(CanRetry::Yes) } /// Try expanding the macro attribute. Returns the index of the successful arm and its /// named_matches if it was successful, and nothing if it failed. On failure, it's the caller's job /// to use `track` accordingly to record all errors correctly. #[instrument(level = "debug", skip(psess, attr_args, attr_body, rules, track), fields(tracking = %T::description()))] pub(super) fn try_match_macro_attr<'matcher, T: Tracker<'matcher>>( psess: &ParseSess, name: Ident, attr_args: &TokenStream, attr_body: &TokenStream, rules: &'matcher [MacroRule], track: &mut T, ) -> Result<(usize, &'matcher MacroRule, NamedMatches), CanRetry> { // This uses the same strategy as `try_match_macro` let args_parser = parser_from_cx(psess, attr_args.clone(), T::recovery()); let body_parser = parser_from_cx(psess, attr_body.clone(), T::recovery()); let mut tt_parser = TtParser::new(name); for (i, rule) in rules.iter().enumerate() { let MacroRule::Attr { args, body, .. } = rule else { continue }; let mut gated_spans_snapshot = mem::take(&mut *psess.gated_spans.spans.borrow_mut()); let result = tt_parser.parse_tt(&mut Cow::Borrowed(&args_parser), args, track); track.after_arm(false, &result); let mut named_matches = match result { Success(named_matches) => named_matches, Failure(_) => { mem::swap(&mut gated_spans_snapshot, &mut psess.gated_spans.spans.borrow_mut()); continue; } Error(_, _) => return Err(CanRetry::Yes), ErrorReported(guar) => return Err(CanRetry::No(guar)), }; let result = tt_parser.parse_tt(&mut Cow::Borrowed(&body_parser), body, track); track.after_arm(true, &result); match result { Success(body_named_matches) => { psess.gated_spans.merge(gated_spans_snapshot); #[allow(rustc::potential_query_instability)] named_matches.extend(body_named_matches); return Ok((i, rule, named_matches)); } Failure(_) => { mem::swap(&mut gated_spans_snapshot, &mut psess.gated_spans.spans.borrow_mut()) } Error(_, _) => return Err(CanRetry::Yes), ErrorReported(guar) => return Err(CanRetry::No(guar)), } } Err(CanRetry::Yes) } /// Try expanding the macro derive. Returns the index of the successful arm and its /// named_matches if it was successful, and nothing if it failed. On failure, it's the caller's job /// to use `track` accordingly to record all errors correctly. #[instrument(level = "debug", skip(psess, body, rules, track), fields(tracking = %T::description()))] pub(super) fn try_match_macro_derive<'matcher, T: Tracker<'matcher>>( psess: &ParseSess, name: Ident, body: &TokenStream, rules: &'matcher [MacroRule], track: &mut T, ) -> Result<(usize, &'matcher MacroRule, NamedMatches), CanRetry> { // This uses the same strategy as `try_match_macro` let body_parser = parser_from_cx(psess, body.clone(), T::recovery()); let mut tt_parser = TtParser::new(name); for (i, rule) in rules.iter().enumerate() { let MacroRule::Derive { body, .. } = rule else { continue }; let mut gated_spans_snapshot = mem::take(&mut *psess.gated_spans.spans.borrow_mut()); let result = tt_parser.parse_tt(&mut Cow::Borrowed(&body_parser), body, track); track.after_arm(true, &result); match result { Success(named_matches) => { psess.gated_spans.merge(gated_spans_snapshot); return Ok((i, rule, named_matches)); } Failure(_) => { mem::swap(&mut gated_spans_snapshot, &mut psess.gated_spans.spans.borrow_mut()) } Error(_, _) => return Err(CanRetry::Yes), ErrorReported(guar) => return Err(CanRetry::No(guar)), } } Err(CanRetry::Yes) } /// Converts a macro item into a syntax extension. pub fn compile_declarative_macro( sess: &Session, features: &Features, macro_def: &ast::MacroDef, ident: Ident, attrs: &[hir::Attribute], span: Span, node_id: NodeId, edition: Edition, ) -> (SyntaxExtension, usize) { let mk_syn_ext = |kind| { let is_local = is_defined_in_current_crate(node_id); SyntaxExtension::new(sess, kind, span, Vec::new(), edition, ident.name, attrs, is_local) }; let dummy_syn_ext = |guar| (mk_syn_ext(SyntaxExtensionKind::Bang(Arc::new(DummyBang(guar)))), 0); let macro_rules = macro_def.macro_rules; let exp_sep = if macro_rules { exp!(Semi) } else { exp!(Comma) }; let body = macro_def.body.tokens.clone(); let mut p = Parser::new(&sess.psess, body, rustc_parse::MACRO_ARGUMENTS); // Don't abort iteration early, so that multiple errors can be reported. We only abort early on // parse failures we can't recover from. let mut guar = None; let mut check_emission = |ret: Result<(), ErrorGuaranteed>| guar = guar.or(ret.err()); let mut kinds = MacroKinds::empty(); let mut rules = Vec::new(); while p.token != token::Eof { let (args, is_derive) = if p.eat_keyword_noexpect(sym::attr) { kinds |= MacroKinds::ATTR; if !features.macro_attr() { feature_err(sess, sym::macro_attr, span, "`macro_rules!` attributes are unstable") .emit(); } if let Some(guar) = check_no_eof(sess, &p, "expected macro attr args") { return dummy_syn_ext(guar); } let args = p.parse_token_tree(); check_args_parens(sess, sym::attr, &args); let args = parse_one_tt(args, RulePart::Pattern, sess, node_id, features, edition); check_emission(check_lhs(sess, node_id, &args)); if let Some(guar) = check_no_eof(sess, &p, "expected macro attr body") { return dummy_syn_ext(guar); } (Some(args), false) } else if p.eat_keyword_noexpect(sym::derive) { kinds |= MacroKinds::DERIVE; let derive_keyword_span = p.prev_token.span; if !features.macro_derive() { feature_err(sess, sym::macro_derive, span, "`macro_rules!` derives are unstable") .emit(); } if let Some(guar) = check_no_eof(sess, &p, "expected `()` after `derive`") { return dummy_syn_ext(guar); } let args = p.parse_token_tree(); check_args_parens(sess, sym::derive, &args); let args_empty_result = check_args_empty(sess, &args); let args_not_empty = args_empty_result.is_err(); check_emission(args_empty_result); if let Some(guar) = check_no_eof(sess, &p, "expected macro derive body") { return dummy_syn_ext(guar); } // If the user has `=>` right after the `()`, they might have forgotten the empty // parentheses. if p.token == token::FatArrow { let mut err = sess .dcx() .struct_span_err(p.token.span, "expected macro derive body, got `=>`"); if args_not_empty { err.span_label(derive_keyword_span, "need `()` after this `derive`"); } return dummy_syn_ext(err.emit()); } (None, true) } else { kinds |= MacroKinds::BANG; (None, false) }; let lhs_tt = p.parse_token_tree(); let lhs_tt = parse_one_tt(lhs_tt, RulePart::Pattern, sess, node_id, features, edition); check_emission(check_lhs(sess, node_id, &lhs_tt)); if let Err(e) = p.expect(exp!(FatArrow)) { return dummy_syn_ext(e.emit()); } if let Some(guar) = check_no_eof(sess, &p, "expected right-hand side of macro rule") { return dummy_syn_ext(guar); } let rhs_tt = p.parse_token_tree(); let rhs_tt = parse_one_tt(rhs_tt, RulePart::Body, sess, node_id, features, edition); check_emission(check_rhs(sess, &rhs_tt)); check_emission(check_meta_variables(&sess.psess, node_id, args.as_ref(), &lhs_tt, &rhs_tt)); let lhs_span = lhs_tt.span(); // Convert the lhs into `MatcherLoc` form, which is better for doing the // actual matching. let lhs = if let mbe::TokenTree::Delimited(.., delimited) = lhs_tt { mbe::macro_parser::compute_locs(&delimited.tts) } else { return dummy_syn_ext(guar.unwrap()); }; if let Some(args) = args { let args_span = args.span(); let mbe::TokenTree::Delimited(.., delimited) = args else { return dummy_syn_ext(guar.unwrap()); }; let args = mbe::macro_parser::compute_locs(&delimited.tts); let body_span = lhs_span; rules.push(MacroRule::Attr { args, args_span, body: lhs, body_span, rhs: rhs_tt }); } else if is_derive { rules.push(MacroRule::Derive { body: lhs, body_span: lhs_span, rhs: rhs_tt }); } else { rules.push(MacroRule::Func { lhs, lhs_span, rhs: rhs_tt }); } if p.token == token::Eof { break; } if let Err(e) = p.expect(exp_sep) { return dummy_syn_ext(e.emit()); } } if rules.is_empty() { let guar = sess.dcx().span_err(span, "macros must contain at least one rule"); return dummy_syn_ext(guar); } assert!(!kinds.is_empty()); let transparency = find_attr!(attrs, AttributeKind::MacroTransparency(x) => *x) .unwrap_or(Transparency::fallback(macro_rules)); if let Some(guar) = guar { // To avoid warning noise, only consider the rules of this // macro for the lint, if all rules are valid. return dummy_syn_ext(guar); } // Return the number of rules for unused rule linting, if this is a local macro. let nrules = if is_defined_in_current_crate(node_id) { rules.len() } else { 0 }; let exp = MacroRulesMacroExpander { name: ident, kinds, span, node_id, transparency, rules }; (mk_syn_ext(SyntaxExtensionKind::MacroRules(Arc::new(exp))), nrules) } fn check_no_eof(sess: &Session, p: &Parser<'_>, msg: &'static str) -> Option { if p.token == token::Eof { let err_sp = p.token.span.shrink_to_hi(); let guar = sess .dcx() .struct_span_err(err_sp, "macro definition ended unexpectedly") .with_span_label(err_sp, msg) .emit(); return Some(guar); } None } fn check_args_parens(sess: &Session, rule_kw: Symbol, args: &tokenstream::TokenTree) { // This does not handle the non-delimited case; that gets handled separately by `check_lhs`. if let tokenstream::TokenTree::Delimited(dspan, _, delim, _) = args && *delim != Delimiter::Parenthesis { sess.dcx().emit_err(errors::MacroArgsBadDelim { span: dspan.entire(), sugg: errors::MacroArgsBadDelimSugg { open: dspan.open, close: dspan.close }, rule_kw, }); } } fn check_args_empty(sess: &Session, args: &tokenstream::TokenTree) -> Result<(), ErrorGuaranteed> { match args { tokenstream::TokenTree::Delimited(.., delimited) if delimited.is_empty() => Ok(()), _ => { let msg = "`derive` rules do not accept arguments; `derive` must be followed by `()`"; Err(sess.dcx().span_err(args.span(), msg)) } } } fn check_lhs(sess: &Session, node_id: NodeId, lhs: &mbe::TokenTree) -> Result<(), ErrorGuaranteed> { let e1 = check_lhs_nt_follows(sess, node_id, lhs); let e2 = check_lhs_no_empty_seq(sess, slice::from_ref(lhs)); e1.and(e2) } fn check_lhs_nt_follows( sess: &Session, node_id: NodeId, lhs: &mbe::TokenTree, ) -> Result<(), ErrorGuaranteed> { // 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, node_id, &delimited.tts) } else { let msg = "invalid macro matcher; matchers must be contained in balanced delimiters"; Err(sess.dcx().span_err(lhs.span(), msg)) } } fn is_empty_token_tree(sess: &Session, seq: &mbe::SequenceRepetition) -> bool { if seq.separator.is_some() { false } else { let mut is_empty = true; let mut iter = seq.tts.iter().peekable(); while let Some(tt) = iter.next() { match tt { mbe::TokenTree::MetaVarDecl { kind: NonterminalKind::Vis, .. } => {} mbe::TokenTree::Token(t @ Token { kind: DocComment(..), .. }) => { let mut now = t; while let Some(&mbe::TokenTree::Token( next @ Token { kind: DocComment(..), .. }, )) = iter.peek() { now = next; iter.next(); } let span = t.span.to(now.span); sess.dcx().span_note(span, "doc comments are ignored in matcher position"); } mbe::TokenTree::Sequence(_, sub_seq) if (sub_seq.kleene.op == mbe::KleeneOp::ZeroOrMore || sub_seq.kleene.op == mbe::KleeneOp::ZeroOrOne) => {} _ => is_empty = false, } } is_empty } } /// Checks if a `vis` nonterminal fragment is unnecessarily wrapped in an optional repetition. /// /// When a `vis` fragment (which can already be empty) is wrapped in `$(...)?`, /// this suggests removing the redundant repetition syntax since it provides no additional benefit. fn check_redundant_vis_repetition( err: &mut Diag<'_>, sess: &Session, seq: &SequenceRepetition, span: &DelimSpan, ) { if seq.kleene.op == KleeneOp::ZeroOrOne && matches!( seq.tts.first(), Some(mbe::TokenTree::MetaVarDecl { kind: NonterminalKind::Vis, .. }) ) { err.note("a `vis` fragment can already be empty"); err.multipart_suggestion( "remove the `$(` and `)?`", vec![ ( sess.source_map().span_extend_to_prev_char_before(span.open, '$', true), "".to_string(), ), (span.close.with_hi(seq.kleene.span.hi()), "".to_string()), ], Applicability::MaybeIncorrect, ); } } /// 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: &Session, tts: &[mbe::TokenTree]) -> Result<(), ErrorGuaranteed> { use mbe::TokenTree; for tt in tts { match tt { TokenTree::Token(..) | TokenTree::MetaVar(..) | TokenTree::MetaVarDecl { .. } | TokenTree::MetaVarExpr(..) => (), TokenTree::Delimited(.., del) => check_lhs_no_empty_seq(sess, &del.tts)?, TokenTree::Sequence(span, seq) => { if is_empty_token_tree(sess, seq) { let sp = span.entire(); let mut err = sess.dcx().struct_span_err(sp, "repetition matches empty token tree"); check_redundant_vis_repetition(&mut err, sess, seq, span); return Err(err.emit()); } check_lhs_no_empty_seq(sess, &seq.tts)? } } } Ok(()) } fn check_rhs(sess: &Session, rhs: &mbe::TokenTree) -> Result<(), ErrorGuaranteed> { match *rhs { mbe::TokenTree::Delimited(..) => Ok(()), _ => Err(sess.dcx().span_err(rhs.span(), "macro rhs must be delimited")), } } fn check_matcher( sess: &Session, node_id: NodeId, matcher: &[mbe::TokenTree], ) -> Result<(), ErrorGuaranteed> { let first_sets = FirstSets::new(matcher); let empty_suffix = TokenSet::empty(); check_matcher_core(sess, node_id, &first_sets, matcher, &empty_suffix)?; Ok(()) } fn has_compile_error_macro(rhs: &mbe::TokenTree) -> bool { match rhs { mbe::TokenTree::Delimited(.., 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::Bang = bang.kind && let mbe::TokenTree::Delimited(.., del) = args && !del.delim.skip() { 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, _, delimited) => { build_recur(sets, &delimited.tts); first.replace_with(TtHandle::from_token_kind( delimited.delim.as_open_token_kind(), span.open, )); } TokenTree::Sequence(sp, 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)); } // 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, _, delimited) => { first.add_one(TtHandle::from_token_kind( delimited.delim.as_open_token_kind(), span.open, )); return first; } TokenTree::Sequence(sp, seq_rep) => { let subfirst_owned; let subfirst = match self.first.get(&sp.entire()) { Some(Some(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)); } 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 preexisting 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)) } _ => 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-empty. 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: &Session, node_id: NodeId, first_sets: &FirstSets<'tt>, matcher: &'tt [mbe::TokenTree], follow: &TokenSet<'tt>, ) -> Result, ErrorGuaranteed> { use mbe::TokenTree; let mut last = TokenSet::empty(); let mut errored = Ok(()); // 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, _, d) => { let my_suffix = TokenSet::singleton(TtHandle::from_token_kind( d.delim.as_close_token_kind(), span.close, )); check_matcher_core(sess, node_id, 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(_, 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)); &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, node_id, 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, 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.) if is_defined_in_current_crate(node_id) && matches!(kind, NonterminalKind::Pat(PatParam { inferred: true })) && matches!( next_token, TokenTree::Token(token) if *token == token::Or ) { // It is suggestion to use pat_param, for example: $x:pat -> $x:pat_param. let suggestion = quoted_tt_to_string(&TokenTree::MetaVarDecl { span, name, kind: NonterminalKind::Pat(PatParam { inferred: false }), }); sess.psess.buffer_lint( RUST_2021_INCOMPATIBLE_OR_PATTERNS, span, ast::CRATE_NODE_ID, errors::OrPatternsBackCompat { span, suggestion }, ); } match is_in_follow(next_token, kind) { IsInFollow::Yes => {} IsInFollow::No(possible) => { let may_be = if last.tokens.len() == 1 && suffix_first.tokens.len() == 1 { "is" } else { "may be" }; let sp = next_token.span(); let mut err = sess.dcx().struct_span_err( sp, format!( "`${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 `{kind}` fragments")); if kind == NonterminalKind::Pat(PatWithOr) && sess.psess.edition.at_least_rust_2021() && next_token.is_token(&token::Or) { let suggestion = quoted_tt_to_string(&TokenTree::MetaVarDecl { span, name, kind: NonterminalKind::Pat(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 {t} is allowed after `{kind}` fragments", )); } ts => { err.note(format!( "{}{} or {}", msg, ts[..ts.len() - 1].to_vec().join(", "), ts[ts.len() - 1], )); } } errored = Err(err.emit()); } } } } } } errored?; Ok(last) } fn token_can_be_followed_by_any(tok: &mbe::TokenTree) -> bool { if let mbe::TokenTree::MetaVarDecl { 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, .. }) = tok && kind.close_delim().is_some() { // 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::Pat(PatParam { .. }) => { const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`|`", "`if`", "`in`"]; match tok { TokenTree::Token(token) => match token.kind { FatArrow | Comma | Eq | Or => IsInFollow::Yes, Ident(name, IdentIsRaw::No) if name == kw::If || name == kw::In => { IsInFollow::Yes } _ => IsInFollow::No(TOKENS), }, _ => IsInFollow::No(TOKENS), } } NonterminalKind::Pat(PatWithOr) => { const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`if`", "`in`"]; match tok { TokenTree::Token(token) => match token.kind { FatArrow | Comma | Eq => IsInFollow::Yes, Ident(name, IdentIsRaw::No) 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 { OpenBrace | OpenBracket | Comma | FatArrow | Colon | Eq | Gt | Shr | Semi | Or => IsInFollow::Yes, Ident(name, IdentIsRaw::No) if name == kw::As || name == kw::Where => { IsInFollow::Yes } _ => IsInFollow::No(TOKENS), }, TokenTree::MetaVarDecl { kind: 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(_, IdentIsRaw::Yes) => IsInFollow::Yes, Ident(name, _) if name != kw::Priv => IsInFollow::Yes, _ => { if token.can_begin_type() { IsInFollow::Yes } else { IsInFollow::No(TOKENS) } } }, TokenTree::MetaVarDecl { kind: 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(token) => pprust::token_to_string(token).into(), 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" ), } } fn is_defined_in_current_crate(node_id: NodeId) -> bool { // Macros defined in the current crate have a real node id, // whereas macros from an external crate have a dummy id. node_id != DUMMY_NODE_ID } pub(super) fn parser_from_cx( psess: &ParseSess, mut tts: TokenStream, recovery: Recovery, ) -> Parser<'_> { tts.desugar_doc_comments(); Parser::new(psess, tts, rustc_parse::MACRO_ARGUMENTS).recovery(recovery) }