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-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs1420
1 files changed, 1420 insertions, 0 deletions
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 `<eof>`") {
+ if !e.span.is_dummy() {
+ // early end of macro arm (#52866)
+ e.replace_span_with(parser.sess.source_map().next_point(parser.token.span));
+ }
+ let msg = &e.message[0];
+ e.message[0] = (
+ rustc_errors::DiagnosticMessage::Str(format!(
+ "macro expansion ends with an incomplete expression: {}",
+ msg.0.expect_str().replace(", found `<eof>`", ""),
+ )),
+ msg.1,
+ );
+ }
+ if e.span.is_dummy() {
+ // Get around lack of span in error (#30128)
+ e.replace_span_with(site_span);
+ if !parser.sess.source_map().is_imported(arm_span) {
+ e.span_label(arm_span, "in this macro arm");
+ }
+ } else if parser.sess.source_map().is_imported(parser.token.span) {
+ e.span_label(site_span, "in this macro invocation");
+ }
+ match kind {
+ // Try a statement if an expression is wanted but failed and suggest adding `;` to call.
+ AstFragmentKind::Expr => match parse_ast_fragment(orig_parser, AstFragmentKind::Stmts) {
+ Err(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<ParserAnyMacro<'a>>, kind: AstFragmentKind) -> AstFragment {
+ let ParserAnyMacro {
+ site_span,
+ macro_ident,
+ ref mut parser,
+ lint_node_id,
+ arm_span,
+ is_trailing_mac,
+ is_local,
+ } = *self;
+ let snapshot = &mut parser.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<Vec<MatcherLoc>>,
+ rhses: Vec<mbe::TokenTree>,
+ valid: bool,
+}
+
+impl TTMacroExpander for MacroRulesMacroExpander {
+ fn expand<'cx>(
+ &self,
+ cx: &'cx mut ExtCtxt<'_>,
+ sp: Span,
+ input: TokenStream,
+ ) -> Box<dyn MacResult + 'cx> {
+ if !self.valid {
+ return DummyResult::any(sp);
+ }
+ 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<dyn MacResult + 'cx> {
+ DummyResult::any(span)
+}
+
+fn trace_macros_note(cx_expansions: &mut FxIndexMap<Span, Vec<String>>, sp: Span, message: String) {
+ let sp = sp.macro_backtrace().last().map_or(sp, |trace| trace.call_site);
+ cx_expansions.entry(sp).or_default().push(message);
+}
+
+/// 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<MatcherLoc>],
+ rhses: &[mbe::TokenTree],
+) -> Box<dyn MacResult + 'cx> {
+ 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::<Vec<_>>();
+ // 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::<Vec<mbe::TokenTree>>(),
+ _ => sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs"),
+ };
+
+ let rhses = match argument_map[&MacroRulesNormalizedIdent::new(rhs_nm)] {
+ MatchedSeq(ref s) => s
+ .iter()
+ .map(|m| {
+ if let 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::<Vec<mbe::TokenTree>>(),
+ _ => sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs"),
+ };
+
+ for rhs in &rhses {
+ valid &= check_rhs(&sess.parse_sess, rhs);
+ }
+
+ // don't abort iteration early, so that errors for multiple lhses can be reported
+ for lhs in &lhses {
+ valid &= check_lhs_no_empty_seq(&sess.parse_sess, slice::from_ref(lhs));
+ }
+
+ valid &= macro_check::check_meta_variables(&sess.parse_sess, def.id, def.span, &lhses, &rhses);
+
+ let (transparency, transparency_error) = attr::find_transparency(&def.attrs, macro_rules);
+ match transparency_error {
+ Some(TransparencyError::UnknownTransparency(value, span)) => {
+ diag.span_err(span, &format!("unknown macro transparency: `{}`", value));
+ }
+ Some(TransparencyError::MultipleTransparencyAttrs(old_span, new_span)) => {
+ diag.span_err(vec![old_span, new_span], "multiple macro transparency attributes");
+ }
+ None => {}
+ }
+
+ // 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::<Vec<_>>()
+ } 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<Span, Option<TokenSet<'tt>>>,
+}
+
+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<TtHandle<'tt>>,
+ 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::<Vec<_>>()
+ .join(", "),
+ ts[ts.len() - 1],
+ ));
+ }
+ }
+ err.emit();
+ }
+ }
+ }
+ }
+ }
+ }
+ last
+}
+
+fn token_can_be_followed_by_any(tok: &mbe::TokenTree) -> bool {
+ if let mbe::TokenTree::MetaVarDecl(_, _, Some(kind)) = *tok {
+ frag_can_be_followed_by_any(kind)
+ } else {
+ // (Non NT's can always be followed by anything in matchers.)
+ true
+ }
+}
+
+/// Returns `true` if a fragment of type `frag` can be followed by any sort of
+/// token. We use this (among other things) as a useful approximation
+/// for when `frag` can be followed by a repetition like `$(...)*` or
+/// `$(...)+`. In general, these can be a bit tricky to reason about,
+/// so we adopt a conservative position that says that any fragment
+/// specifier which consumes at most one token tree can be followed by
+/// a fragment specifier (indeed, these fragments can be followed by
+/// ANYTHING without fear of future compatibility hazards).
+fn frag_can_be_followed_by_any(kind: NonterminalKind) -> bool {
+ matches!(
+ kind,
+ NonterminalKind::Item // always terminated by `}` or `;`
+ | NonterminalKind::Block // exactly one token tree
+ | NonterminalKind::Ident // exactly one token tree
+ | NonterminalKind::Literal // exactly one token tree
+ | NonterminalKind::Meta // exactly one token tree
+ | NonterminalKind::Lifetime // exactly one token tree
+ | NonterminalKind::TT // exactly one token tree
+ )
+}
+
+enum IsInFollow {
+ Yes,
+ No(&'static [&'static str]),
+}
+
+/// Returns `true` if `frag` can legally be followed by the token `tok`. For
+/// fragments that can consume an unbounded number of tokens, `tok`
+/// must be within a well-defined follow set. This is intended to
+/// guarantee future compatibility: for example, without this rule, if
+/// we expanded `expr` to include a new binary operator, we might
+/// break macros that were relying on that binary operator as a
+/// separator.
+// when changing this do not forget to update doc/book/macros.md!
+fn is_in_follow(tok: &mbe::TokenTree, kind: NonterminalKind) -> IsInFollow {
+ use mbe::TokenTree;
+
+ if let TokenTree::Token(Token { kind: token::CloseDelim(_), .. }) = *tok {
+ // closing a token tree can never be matched by any fragment;
+ // iow, we always require that `(` and `)` match, etc.
+ IsInFollow::Yes
+ } else {
+ match kind {
+ NonterminalKind::Item => {
+ // since items *must* be followed by either a `;` or a `}`, we can
+ // accept anything after them
+ IsInFollow::Yes
+ }
+ NonterminalKind::Block => {
+ // anything can follow block, the braces provide an easy boundary to
+ // maintain
+ IsInFollow::Yes
+ }
+ NonterminalKind::Stmt | NonterminalKind::Expr => {
+ const TOKENS: &[&str] = &["`=>`", "`,`", "`;`"];
+ match tok {
+ TokenTree::Token(token) => match token.kind {
+ FatArrow | Comma | Semi => IsInFollow::Yes,
+ _ => IsInFollow::No(TOKENS),
+ },
+ _ => IsInFollow::No(TOKENS),
+ }
+ }
+ NonterminalKind::PatParam { .. } => {
+ const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`|`", "`if`", "`in`"];
+ match tok {
+ TokenTree::Token(token) => match token.kind {
+ FatArrow | Comma | Eq | BinOp(token::Or) => IsInFollow::Yes,
+ Ident(name, false) if name == kw::If || name == kw::In => IsInFollow::Yes,
+ _ => IsInFollow::No(TOKENS),
+ },
+ _ => IsInFollow::No(TOKENS),
+ }
+ }
+ NonterminalKind::PatWithOr { .. } => {
+ const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`if`", "`in`"];
+ match tok {
+ TokenTree::Token(token) => match token.kind {
+ FatArrow | Comma | Eq => IsInFollow::Yes,
+ Ident(name, false) if name == kw::If || name == kw::In => IsInFollow::Yes,
+ _ => IsInFollow::No(TOKENS),
+ },
+ _ => IsInFollow::No(TOKENS),
+ }
+ }
+ NonterminalKind::Path | NonterminalKind::Ty => {
+ const TOKENS: &[&str] = &[
+ "`{`", "`[`", "`=>`", "`,`", "`>`", "`=`", "`:`", "`;`", "`|`", "`as`",
+ "`where`",
+ ];
+ match tok {
+ TokenTree::Token(token) => match token.kind {
+ OpenDelim(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),),
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-12 07:26:34 +0000