Auto merge of #121790 - jhpratt:rollup-yocg203, r=jhpratt

Rollup of 10 pull requests

Successful merges:

 - #119748 (Increase visibility of `join_path` and `split_paths`)
 - #120291 (Have `String` use `SliceIndex` impls from `str`)
 - #121723 (Two diagnostic things)
 - #121740 (Changing some attributes to only_local.)
 - #121745 (Deeply normalize obligations in `refining_impl_trait`)
 - #121748 (Restore the standard library review rotation to its former glory)
 - #121768 (Implement unwind safety for Condvar on all platforms )
 - #121777 (Fix typo in `rustc_passes/messages.ftl`)
 - #121778 (Document potential memory leak in unbounded channel)
 - #121779 (Remove unused diagnostic struct)

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

3 files changed, 25 insertions, 2 deletions

diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 5bd20ebe208..1f2b8d3007d 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -258,6 +258,9 @@ fn _var(key: &OsStr) -> Result<String, VarError> {
 ///     None => println!("{key} is not defined in the environment.")
 /// }
 /// ```
+///
+/// If expecting a delimited variable (such as `PATH`), [`split_paths`]
+/// can be used to separate items.
 #[must_use]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn var_os<K: AsRef<OsStr>>(key: K) -> Option<OsString> {
@@ -441,6 +444,16 @@ pub struct SplitPaths<'a> {
 /// Returns an iterator over the paths contained in `unparsed`. The iterator
 /// element type is [`PathBuf`].
 ///
+/// On most Unix platforms, the separator is `:` and on Windows it is `;`. This
+/// also performs unquoting on Windows.
+///
+/// [`join_paths`] can be used to recombine elements.
+///
+/// # Panics
+///
+/// This will panic on systems where there is no delimited `PATH` variable,
+/// such as UEFI.
+///
 /// # Examples
 ///
 /// ```
@@ -456,6 +469,7 @@ pub struct SplitPaths<'a> {
 ///     None => println!("{key} is not defined in the environment.")
 /// }
 /// ```
+#[doc(alias = "PATH")]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn split_paths<T: AsRef<OsStr> + ?Sized>(unparsed: &T) -> SplitPaths<'_> {
     SplitPaths { inner: os_imp::split_paths(unparsed.as_ref()) }
@@ -496,7 +510,8 @@ pub struct JoinPathsError {
 ///
 /// Returns an [`Err`] (containing an error message) if one of the input
 /// [`Path`]s contains an invalid character for constructing the `PATH`
-/// variable (a double quote on Windows or a colon on Unix).
+/// variable (a double quote on Windows or a colon on Unix), or if the system
+/// does not have a `PATH`-like variable (e.g. UEFI or WASI).
 ///
 /// # Examples
 ///
@@ -550,6 +565,7 @@ pub struct JoinPathsError {
 /// ```
 ///
 /// [`env::split_paths()`]: split_paths
+#[doc(alias = "PATH")]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn join_paths<I, T>(paths: I) -> Result<OsString, JoinPathsError>
 where
diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index 3728d5b64b8..3d576af681e 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -6,7 +6,7 @@ use crate::any::Any;
 use crate::collections;
 use crate::panicking;
 use crate::sync::atomic::{AtomicU8, Ordering};
-use crate::sync::{Mutex, RwLock};
+use crate::sync::{Condvar, Mutex, RwLock};
 use crate::thread::Result;
 
 #[doc(hidden)]
@@ -67,11 +67,15 @@ pub fn panic_any<M: 'static + Any + Send>(msg: M) -> ! {
 impl<T: ?Sized> UnwindSafe for Mutex<T> {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: ?Sized> UnwindSafe for RwLock<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl UnwindSafe for Condvar {}
 
 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
 impl<T: ?Sized> RefUnwindSafe for Mutex<T> {}
 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
 impl<T: ?Sized> RefUnwindSafe for RwLock<T> {}
+#[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
+impl RefUnwindSafe for Condvar {}
 
 // https://github.com/rust-lang/rust/issues/62301
 #[stable(feature = "hashbrown", since = "1.36.0")]
diff --git a/library/std/src/sync/mpmc/list.rs b/library/std/src/sync/mpmc/list.rs
index a1b275112a1..9e7148c716c 100644
--- a/library/std/src/sync/mpmc/list.rs
+++ b/library/std/src/sync/mpmc/list.rs
@@ -547,6 +547,9 @@ impl<T> Channel<T> {
         }
 
         let mut head = self.head.index.load(Ordering::Acquire);
+        // The channel may be uninitialized, so we have to swap to avoid overwriting any sender's attempts
+        // to initalize the first block before noticing that the receivers disconnected. Late allocations
+        // will be deallocated by the sender in Drop.
         let mut block = self.head.block.swap(ptr::null_mut(), Ordering::AcqRel);
 
         // If we're going to be dropping messages we need to synchronize with initialization