diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs index 197f056917f..40aa64d9d40 100644 --- a/compiler/rustc_expand/src/mbe/diagnostics.rs +++ b/compiler/rustc_expand/src/mbe/diagnostics.rs @@ -43,7 +43,7 @@ pub(super) fn failed_to_match_macro<'cx>( return result; } - let Some((token, label, remaining_matcher)) = tracker.best_failure else { + let Some(BestFailure { token, msg: label, remaining_matcher, .. }) = tracker.best_failure else { return DummyResult::any(sp); }; @@ -95,11 +95,24 @@ struct CollectTrackerAndEmitter<'a, 'cx, 'matcher> { cx: &'a mut ExtCtxt<'cx>, remaining_matcher: Option<&'matcher MatcherLoc>, /// Which arm's failure should we report? (the one furthest along) - best_failure: Option<(Token, &'static str, MatcherLoc)>, + best_failure: Option, root_span: Span, result: Option>, } +struct BestFailure { + token: Token, + position_in_tokenstream: usize, + msg: &'static str, + remaining_matcher: MatcherLoc, +} + +impl BestFailure { + fn is_better_position(&self, position: usize) -> bool { + position > self.position_in_tokenstream + } +} + impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx, 'matcher> { fn before_match_loc(&mut self, parser: &TtParser, matcher: &'matcher MatcherLoc) { if self.remaining_matcher.is_none() @@ -119,18 +132,25 @@ impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx, "should not collect detailed info for successful macro match", ); } - Failure(token, msg) => match self.best_failure { - Some((ref best_token, _, _)) if best_token.span.lo() >= token.span.lo() => {} - _ => { - self.best_failure = Some(( - token.clone(), + Failure(token, approx_position, msg) => { + debug!(?token, ?msg, "a new failure of an arm"); + + if self + .best_failure + .as_ref() + .map_or(true, |failure| failure.is_better_position(*approx_position)) + { + self.best_failure = Some(BestFailure { + token: token.clone(), + position_in_tokenstream: *approx_position, msg, - self.remaining_matcher + remaining_matcher: self + .remaining_matcher .expect("must have collected matcher already") .clone(), - )) + }) } - }, + } Error(err_sp, msg) => { let span = err_sp.substitute_dummy(self.root_span); self.cx.struct_span_err(span, msg).emit(); diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs index d161868edce..df1c1834c1d 100644 --- a/compiler/rustc_expand/src/mbe/macro_parser.rs +++ b/compiler/rustc_expand/src/mbe/macro_parser.rs @@ -310,7 +310,8 @@ pub(crate) enum ParseResult { Success(T), /// Arm failed to match. If the second parameter is `token::Eof`, it indicates an unexpected /// end of macro invocation. Otherwise, it indicates that no rules expected the given token. - Failure(Token, &'static str), + /// The usize is the approximate position of the token in the input token stream. + Failure(Token, usize, &'static str), /// Fatal error (malformed macro?). Abort compilation. Error(rustc_span::Span, String), ErrorReported(ErrorGuaranteed), @@ -455,6 +456,7 @@ impl TtParser { &mut self, matcher: &'matcher [MatcherLoc], token: &Token, + approx_position: usize, track: &mut T, ) -> Option { // Matcher positions that would be valid if the macro invocation was over now. Only @@ -598,6 +600,7 @@ impl TtParser { token::Eof, if token.span.is_dummy() { token.span } else { token.span.shrink_to_hi() }, ), + approx_position, "missing tokens in macro arguments", ), }) @@ -627,7 +630,12 @@ impl TtParser { // Process `cur_mps` until either we have finished the input or we need to get some // parsing from the black-box parser done. - let res = self.parse_tt_inner(matcher, &parser.token, track); + let res = self.parse_tt_inner( + matcher, + &parser.token, + parser.approx_token_stream_pos(), + track, + ); if let Some(res) = res { return res; } @@ -642,6 +650,7 @@ impl TtParser { // parser: syntax error. return Failure( parser.token.clone(), + parser.approx_token_stream_pos(), "no rules expected this token in macro call", ); } diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs index 2dbb90e2190..b4001a497af 100644 --- a/compiler/rustc_expand/src/mbe/macro_rules.rs +++ b/compiler/rustc_expand/src/mbe/macro_rules.rs @@ -326,8 +326,8 @@ pub(super) fn try_match_macro<'matcher, T: Tracker<'matcher>>( return Ok((i, named_matches)); } - Failure(_, _) => { - trace!("Failed to match arm, trying the next one"); + Failure(_, reached_position, _) => { + trace!(%reached_position, "Failed to match arm, trying the next one"); // Try the next arm. } Error(_, _) => { @@ -432,7 +432,7 @@ pub fn compile_declarative_macro( let argument_map = match tt_parser.parse_tt(&mut Cow::Owned(parser), &argument_gram, &mut NoopTracker) { Success(m) => m, - Failure(token, msg) => { + 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); diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index bebb012660a..008388e3da3 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -1503,6 +1503,10 @@ impl<'a> Parser<'a> { pub fn clear_expected_tokens(&mut self) { self.expected_tokens.clear(); } + + pub fn approx_token_stream_pos(&self) -> usize { + self.token_cursor.num_next_calls + } } pub(crate) fn make_unclosed_delims_error( diff --git a/src/test/ui/macros/best-failure.rs b/src/test/ui/macros/best-failure.rs new file mode 100644 index 00000000000..bbdd465d5ec --- /dev/null +++ b/src/test/ui/macros/best-failure.rs @@ -0,0 +1,11 @@ +macro_rules! number { + (neg false, $self:ident) => { $self }; + ($signed:tt => $ty:ty;) => { + number!(neg $signed, $self); + //~^ ERROR no rules expected the token `$` + }; +} + +number! { false => u8; } + +fn main() {} diff --git a/src/test/ui/macros/best-failure.stderr b/src/test/ui/macros/best-failure.stderr new file mode 100644 index 00000000000..a52fc5e3da6 --- /dev/null +++ b/src/test/ui/macros/best-failure.stderr @@ -0,0 +1,21 @@ +error: no rules expected the token `$` + --> $DIR/best-failure.rs:4:30 + | +LL | macro_rules! number { + | ------------------- when calling this macro +... +LL | number!(neg $signed, $self); + | ^^^^^ no rules expected this token in macro call +... +LL | number! { false => u8; } + | ------------------------ in this macro invocation + | +note: while trying to match meta-variable `$self:ident` + --> $DIR/best-failure.rs:2:17 + | +LL | (neg false, $self:ident) => { $self }; + | ^^^^^^^^^^^ + = note: this error originates in the macro `number` (in Nightly builds, run with -Z macro-backtrace for more info) + +error: aborting due to previous error +