Auto merge of #83308 - Dylan-DPC:rollup-p2j6sy8, r=Dylan-DPC

Rollup of 8 pull requests

Successful merges:

 - #79986 (Only build help popup when it's really needed)
 - #82570 (Add `as_str` method for split whitespace str iterators)
 - #83244 (Fix overflowing length in Vec<ZST> to VecDeque)
 - #83254 (Include output stream in `panic!()` documentation)
 - #83269 (Revert the second deprecation of collections::Bound)
 - #83277 (Mark early otherwise optimization unsound)
 - #83285 (Update LLVM to bring in SIMD updates for WebAssembly)
 - #83297 (Do not ICE on ty::Error as an error must already have been reported)

Failed merges:

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

5 files changed, 71 insertions, 9 deletions

diff --git a/library/core/src/iter/adapters/filter.rs b/library/core/src/iter/adapters/filter.rs
index f8d684fcdda..0337892b9e8 100644
--- a/library/core/src/iter/adapters/filter.rs
+++ b/library/core/src/iter/adapters/filter.rs
@@ -13,7 +13,8 @@ use crate::ops::Try;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Clone)]
 pub struct Filter<I, P> {
-    iter: I,
+    // Used for `SplitWhitespace` and `SplitAsciiWhitespace` `as_str` methods
+    pub(crate) iter: I,
     predicate: P,
 }
 impl<I, P> Filter<I, P> {
diff --git a/library/core/src/iter/adapters/map.rs b/library/core/src/iter/adapters/map.rs
index 2d997cfe509..2a4b7efd5e6 100644
--- a/library/core/src/iter/adapters/map.rs
+++ b/library/core/src/iter/adapters/map.rs
@@ -57,7 +57,8 @@ use crate::ops::Try;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Clone)]
 pub struct Map<I, F> {
-    iter: I,
+    // Used for `SplitWhitespace` and `SplitAsciiWhitespace` `as_str` methods
+    pub(crate) iter: I,
     f: F,
 }
 
diff --git a/library/core/src/macros/panic.md b/library/core/src/macros/panic.md
index 6e502426df9..5127a16bbfd 100644
--- a/library/core/src/macros/panic.md
+++ b/library/core/src/macros/panic.md
@@ -9,11 +9,15 @@ tests. `panic!` is closely tied with the `unwrap` method of both
 [`Option`][ounwrap] and [`Result`][runwrap] enums. Both implementations call
 `panic!` when they are set to [`None`] or [`Err`] variants.
 
-This macro is used to inject panic into a Rust thread, causing the thread to
-panic entirely. This macro panics with a string and uses the [`format!`] syntax
-for building the message.
-
-Each thread's panic can be reaped as the [`Box`]`<`[`Any`]`>` type,
+When using `panic!()` you can specify a string payload, that is built using
+the [`format!`] syntax. That payload is used when injecting the panic into
+the calling Rust thread, causing the thread to panic entirely.
+
+The behavior of the default `std` hook, i.e. the code that runs directly
+after the panic is invoked, is to print the message payload to
+`stderr` along with the file/line/column information of the `panic!()`
+call. You can override the panic hook using [`std::panic::set_hook()`].
+Inside the hook a panic can be accessed as a `&dyn Any + Send`,
 which contains either a `&str` or `String` for regular `panic!()` invocations.
 To panic with a value of another other type, [`panic_any`] can be used.
 
@@ -26,6 +30,7 @@ See also the macro [`compile_error!`], for raising errors during compilation.
 
 [ounwrap]: Option::unwrap
 [runwrap]: Result::unwrap
+[`std::panic::set_hook()`]: ../std/panic/fn.set_hook.html
 [`panic_any`]: ../std/panic/fn.panic_any.html
 [`Box`]: ../std/boxed/struct.Box.html
 [`Any`]: crate::any::Any
diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index 796301c76b6..c82b76df6ff 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -335,9 +335,11 @@ pub struct Split<'a, T: 'a, P>
 where
     P: FnMut(&T) -> bool,
 {
-    v: &'a [T],
+    // Used for `SplitWhitespace` and `SplitAsciiWhitespace` `as_str` methods
+    pub(crate) v: &'a [T],
     pred: P,
-    finished: bool,
+    // Used for `SplitAsciiWhitespace` `as_str` method
+    pub(crate) finished: bool,
 }
 
 impl<'a, T: 'a, P: FnMut(&T) -> bool> Split<'a, T, P> {
diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index 0c9307a6d2f..4eac017f915 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -1200,6 +1200,30 @@ impl<'a> DoubleEndedIterator for SplitWhitespace<'a> {
 #[stable(feature = "fused", since = "1.26.0")]
 impl FusedIterator for SplitWhitespace<'_> {}
 
+impl<'a> SplitWhitespace<'a> {
+    /// Returns remainder of the splitted string
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(str_split_whitespace_as_str)]
+    ///
+    /// let mut split = "Mary had a little lamb".split_whitespace();
+    /// assert_eq!(split.as_str(), "Mary had a little lamb");
+    ///
+    /// split.next();
+    /// assert_eq!(split.as_str(), "had a little lamb");
+    ///
+    /// split.by_ref().for_each(drop);
+    /// assert_eq!(split.as_str(), "");
+    /// ```
+    #[inline]
+    #[unstable(feature = "str_split_whitespace_as_str", issue = "77998")]
+    pub fn as_str(&self) -> &'a str {
+        self.inner.iter.as_str()
+    }
+}
+
 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
 impl<'a> Iterator for SplitAsciiWhitespace<'a> {
     type Item = &'a str;
@@ -1231,6 +1255,35 @@ impl<'a> DoubleEndedIterator for SplitAsciiWhitespace<'a> {
 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
 impl FusedIterator for SplitAsciiWhitespace<'_> {}
 
+impl<'a> SplitAsciiWhitespace<'a> {
+    /// Returns remainder of the splitted string
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(str_split_whitespace_as_str)]
+    ///
+    /// let mut split = "Mary had a little lamb".split_ascii_whitespace();
+    /// assert_eq!(split.as_str(), "Mary had a little lamb");
+    ///
+    /// split.next();
+    /// assert_eq!(split.as_str(), "had a little lamb");
+    ///
+    /// split.by_ref().for_each(drop);
+    /// assert_eq!(split.as_str(), "");
+    /// ```
+    #[inline]
+    #[unstable(feature = "str_split_whitespace_as_str", issue = "77998")]
+    pub fn as_str(&self) -> &'a str {
+        if self.inner.iter.iter.finished {
+            return "";
+        }
+
+        // SAFETY: Slice is created from str.
+        unsafe { crate::str::from_utf8_unchecked(&self.inner.iter.iter.v) }
+    }
+}
+
 #[stable(feature = "split_inclusive", since = "1.51.0")]
 impl<'a, P: Pattern<'a>> Iterator for SplitInclusive<'a, P> {
     type Item = &'a str;