Auto merge of rust-lang#106228 - matthiaskrgr:rollup-jsznhww, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#104402 (Move `ReentrantMutex` to `std::sync`)
 - rust-lang#104493 (available_parallelism: Gracefully handle zero value cfs_period_us)
 - rust-lang#105359 (Make sentinel value configurable in `library/std/src/sys_common/thread_local_key.rs`)
 - rust-lang#105497 (Clarify `catch_unwind` docs about panic hooks)
 - rust-lang#105570 (Properly calculate best failure in macro matching)
 - rust-lang#105702 (Format only modified files)
 - rust-lang#105998 (adjust message on non-unwinding panic)
 - rust-lang#106161 (Iterator::find: link to Iterator::position in docs for discoverability)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

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<BestFailure>,
     root_span: Span,
     result: Option<Box<dyn MacResult + 'cx>>,
 }
 
+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();

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -310,7 +310,8 @@ pub(crate) enum ParseResult<T> {
     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<NamedParseResult> {
         // 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",
                     );
                 }

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);

compiler/rustc_parse/src/parser/mod.rs

@@ -1499,6 +1499,10 @@ 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(

library/core/src/iter/traits/iterator.rs

@@ -2654,7 +2654,10 @@ pub trait Iterator {
     /// argument is a double reference. You can see this effect in the
     /// examples below, with `&&x`.
     ///
+    /// If you need the index of the element, see [`position()`].
+    ///
     /// [`Some(element)`]: Some
+    /// [`position()`]: Iterator::position
     ///
     /// # Examples
     ///

library/std/src/io/stdio.rs

@@ -10,9 +10,8 @@ use crate::fmt;
 use crate::fs::File;
 use crate::io::{self, BufReader, IoSlice, IoSliceMut, LineWriter, Lines};
 use crate::sync::atomic::{AtomicBool, Ordering};
-use crate::sync::{Arc, Mutex, MutexGuard, OnceLock};
+use crate::sync::{Arc, Mutex, MutexGuard, OnceLock, ReentrantMutex, ReentrantMutexGuard};
 use crate::sys::stdio;
-use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 
 type LocalStream = Arc<Mutex<Vec<u8>>>;
 

library/std/src/panic.rs

@@ -114,6 +114,9 @@ where
 /// aborting the process as well. This function *only* catches unwinding panics,
 /// not those that abort the process.
 ///
+/// Note that if a custom panic hook has been set, it will be invoked before
+/// the panic is caught, before unwinding.
+///
 /// Also note that unwinding into Rust code with a foreign exception (e.g.
 /// an exception thrown from C++ code) is undefined behavior.
 ///

library/std/src/panicking.rs

@@ -699,7 +699,11 @@ fn rust_panic_with_hook(
         // have limited options. Currently our preference is to
         // just abort. In the future we may consider resuming
         // unwinding or otherwise exiting the thread cleanly.
-        rtprintpanic!("thread panicked while panicking. aborting.\n");
+        if !can_unwind {
+            rtprintpanic!("thread caused non-unwinding panic. aborting.\n");
+        } else {
+            rtprintpanic!("thread panicked while panicking. aborting.\n");
+        }
         crate::sys::abort_internal();
     }
 

library/std/src/sync/mod.rs

@@ -177,6 +177,8 @@ pub use self::lazy_lock::LazyLock;
 #[unstable(feature = "once_cell", issue = "74465")]
 pub use self::once_lock::OnceLock;
 
+pub(crate) use self::remutex::{ReentrantMutex, ReentrantMutexGuard};
+
 pub mod mpsc;
 
 mod barrier;
@@ -187,4 +189,5 @@ mod mutex;
 mod once;
 mod once_lock;
 mod poison;
+mod remutex;
 mod rwlock;