Auto merge of #58578 - kennytm:rollup, r=kennytm

Rollup of 24 pull requests

Successful merges:

 - #56470 (Modify doctest's auto-`fn main()` to allow `Result`s)
 - #58044 (Make overflowing and wrapping negation const)
 - #58303 (Improve stability tags display)
 - #58336 (Fix search results interactions)
 - #58384 (Fix tables display)
 - #58392 (Use less explicit shifting in std::net::ip)
 - #58409 (rustdoc: respect alternate flag when formatting impl trait)
 - #58456 (Remove no longer accurate diagnostic code about NLL)
 - #58528 (Don't use an allocation for ItemId in StmtKind)
 - #58530 (Monomorphize less code in fs::{read|write})
 - #58534 (Mention capping forbid lints)
 - #58536 (Remove UB in pointer tests)
 - #58538 (Add missing fmt structs examples)
 - #58539 (Add alias methods to PathBuf for underlying OsString (#58234))
 - #58544 (Fix doc for rustc "-g" flag)
 - #58545 (Add regression test for a specialization-related ICE (#39448))
 - #58546 (librustc_codegen_llvm => 2018)
 - #58551 (Explain a panic in test case net::tcp::tests::double_bind)
 - #58553 (Use more impl header lifetime elision)
 - #58562 (Fix style nits)
 - #58565 (Fix typo in std::future::Future docs)
 - #58568 (Fix a transposition in driver.rs.)
 - #58569 (Reduce Some Code Repetitions like `(n << amt) >> amt`)
 - #58576 (Stabilize iter::successors and iter::from_fn)

11 files changed, 361 insertions, 62 deletions

diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index 2525b47f2bd..45994c2b4f0 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -71,8 +71,10 @@ impl fmt::Write for PadAdapter<'_> {
 ///     }
 /// }
 ///
-/// // prints "Foo { bar: 10, baz: "Hello World" }"
-/// println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });
+/// assert_eq!(
+///     format!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() }),
+///     "Foo { bar: 10, baz: \"Hello World\" }",
+/// );
 /// ```
 #[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
@@ -96,6 +98,33 @@ pub fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,
 
 impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
     /// Adds a new field to the generated struct output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Bar {
+    ///     bar: i32,
+    ///     another: String,
+    /// }
+    ///
+    /// impl fmt::Debug for Bar {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_struct("Bar")
+    ///            .field("bar", &self.bar) // We add `bar` field.
+    ///            .field("another", &self.another) // We add `another` field.
+    ///            // We even add a field which doesn't exist (because why not?).
+    ///            .field("not_existing_field", &1)
+    ///            .finish() // We're good to go!
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Bar { bar: 10, another: "Hello World".to_string() }),
+    ///     "Bar { bar: 10, another: \"Hello World\", not_existing_field: 1 }",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut DebugStruct<'a, 'b> {
         self.result = self.result.and_then(|_| {
@@ -124,6 +153,32 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
     }
 
     /// Finishes output and returns any error encountered.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Bar {
+    ///     bar: i32,
+    ///     baz: String,
+    /// }
+    ///
+    /// impl fmt::Debug for Bar {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_struct("Bar")
+    ///            .field("bar", &self.bar)
+    ///            .field("baz", &self.baz)
+    ///            .finish() // You need to call it to "finish" the
+    ///                      // struct formatting.
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Bar { bar: 10, baz: "Hello World".to_string() }),
+    ///     "Bar { bar: 10, baz: \"Hello World\" }",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
         if self.has_fields {
@@ -168,8 +223,10 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
 ///     }
 /// }
 ///
-/// // prints "Foo(10, "Hello World")"
-/// println!("{:?}", Foo(10, "Hello World".to_string()));
+/// assert_eq!(
+///     format!("{:?}", Foo(10, "Hello World".to_string())),
+///     "Foo(10, \"Hello World\")",
+/// );
 /// ```
 #[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
@@ -193,6 +250,28 @@ pub fn debug_tuple_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>, name: &str) -> D
 
 impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
     /// Adds a new field to the generated tuple struct output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(i32, String);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_tuple("Foo")
+    ///            .field(&self.0) // We add the first field.
+    ///            .field(&self.1) // We add the second field.
+    ///            .finish() // We're good to go!
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(10, "Hello World".to_string())),
+    ///     "Foo(10, \"Hello World\")",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut DebugTuple<'a, 'b> {
         self.result = self.result.and_then(|_| {
@@ -220,6 +299,29 @@ impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
     }
 
     /// Finishes output and returns any error encountered.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(i32, String);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_tuple("Foo")
+    ///            .field(&self.0)
+    ///            .field(&self.1)
+    ///            .finish() // You need to call it to "finish" the
+    ///                      // tuple formatting.
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(10, "Hello World".to_string())),
+    ///     "Foo(10, \"Hello World\")",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
         if self.fields > 0 {
@@ -306,8 +408,10 @@ impl<'a, 'b: 'a> DebugInner<'a, 'b> {
 ///     }
 /// }
 ///
-/// // prints "{10, 11}"
-/// println!("{:?}", Foo(vec![10, 11]));
+/// assert_eq!(
+///     format!("{:?}", Foo(vec![10, 11])),
+///     "{10, 11}",
+/// );
 /// ```
 #[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
@@ -329,6 +433,28 @@ pub fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b
 
 impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     /// Adds a new entry to the set output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>, Vec<u32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_set()
+    ///            .entry(&self.0) // Adds the first "entry".
+    ///            .entry(&self.1) // Adds the second "entry".
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+    ///     "{[10, 11], [12, 13]}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugSet<'a, 'b> {
         self.inner.entry(entry);
@@ -336,6 +462,28 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     }
 
     /// Adds the contents of an iterator of entries to the set output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>, Vec<u32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_set()
+    ///            .entries(self.0.iter()) // Adds the first "entry".
+    ///            .entries(self.1.iter()) // Adds the second "entry".
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+    ///     "{10, 11, 12, 13}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entries<D, I>(&mut self, entries: I) -> &mut DebugSet<'a, 'b>
         where D: fmt::Debug,
@@ -348,6 +496,27 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     }
 
     /// Finishes output and returns any error encountered.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_set()
+    ///            .entries(self.0.iter())
+    ///            .finish() // Ends the struct formatting.
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11])),
+    ///     "{10, 11}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
         self.inner.finish();
@@ -377,8 +546,10 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
 ///     }
 /// }
 ///
-/// // prints "[10, 11]"
-/// println!("{:?}", Foo(vec![10, 11]));
+/// assert_eq!(
+///     format!("{:?}", Foo(vec![10, 11])),
+///     "[10, 11]",
+/// );
 /// ```
 #[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
@@ -400,6 +571,28 @@ pub fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a,
 
 impl<'a, 'b: 'a> DebugList<'a, 'b> {
     /// Adds a new entry to the list output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>, Vec<u32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_list()
+    ///            .entry(&self.0) // We add the first "entry".
+    ///            .entry(&self.1) // We add the second "entry".
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+    ///     "[[10, 11], [12, 13]]",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut DebugList<'a, 'b> {
         self.inner.entry(entry);
@@ -407,6 +600,28 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
     }
 
     /// Adds the contents of an iterator of entries to the list output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>, Vec<u32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_list()
+    ///            .entries(self.0.iter())
+    ///            .entries(self.1.iter())
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+    ///     "[10, 11, 12, 13]",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entries<D, I>(&mut self, entries: I) -> &mut DebugList<'a, 'b>
         where D: fmt::Debug,
@@ -419,6 +634,27 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
     }
 
     /// Finishes output and returns any error encountered.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<i32>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_list()
+    ///            .entries(self.0.iter())
+    ///            .finish() // Ends the struct formatting.
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![10, 11])),
+    ///     "[10, 11]",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
         self.inner.finish();
@@ -448,8 +684,10 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
 ///     }
 /// }
 ///
-/// // prints "{"A": 10, "B": 11}"
-/// println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));
+/// assert_eq!(
+///     format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+///     "{\"A\": 10, \"B\": 11}",
+/// );
 /// ```
 #[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
@@ -471,6 +709,27 @@ pub fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b
 
 impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// Adds a new entry to the map output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<(String, i32)>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_map()
+    ///            .entry(&"whole", &self.0) // We add the "whole" entry.
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+    ///     "{\"whole\": [(\"A\", 10), (\"B\", 11)]}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {
         self.result = self.result.and_then(|_| {
@@ -500,6 +759,29 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     }
 
     /// Adds the contents of an iterator of entries to the map output.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<(String, i32)>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_map()
+    ///            // We map our vec so each entries' first field will become
+    ///            // the "key".
+    ///            .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
+    ///            .finish()
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+    ///     "{\"A\": 10, \"B\": 11}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b>
         where K: fmt::Debug,
@@ -513,6 +795,27 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     }
 
     /// Finishes output and returns any error encountered.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Foo(Vec<(String, i32)>);
+    ///
+    /// impl fmt::Debug for Foo {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         fmt.debug_map()
+    ///            .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
+    ///            .finish() // Ends the struct formatting.
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(
+    ///     format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+    ///     "{\"A\": 10, \"B\": 11}",
+    /// );
+    /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
         let prefix = if self.is_pretty() && self.has_fields {
diff --git a/src/libcore/future/future.rs b/src/libcore/future/future.rs
index 02457e00054..84e7147153e 100644
--- a/src/libcore/future/future.rs
+++ b/src/libcore/future/future.rs
@@ -81,7 +81,7 @@ pub trait Future {
     ///
     /// Once a future has completed (returned `Ready` from `poll`),
     /// then any future calls to `poll` may panic, block forever, or otherwise
-    /// cause any kind of bad behavior expect causing memory unsafety.
+    /// cause any kind of bad behavior except causing memory unsafety.
     /// The `Future` trait itself provides no guarantees about the behavior
     /// of `poll` after a future has completed.
     ///
@@ -92,7 +92,7 @@ pub trait Future {
     fn poll(self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output>;
 }
 
-impl<'a, F: ?Sized + Future + Unpin> Future for &'a mut F {
+impl<F: ?Sized + Future + Unpin> Future for &mut F {
     type Output = F::Output;
 
     fn poll(mut self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output> {
diff --git a/src/libcore/internal_macros.rs b/src/libcore/internal_macros.rs
index 9f0f6fd49fb..faca785e488 100644
--- a/src/libcore/internal_macros.rs
+++ b/src/libcore/internal_macros.rs
@@ -7,7 +7,7 @@ macro_rules! forward_ref_unop {
     };
     (impl $imp:ident, $method:ident for $t:ty, #[$attr:meta]) => {
         #[$attr]
-        impl<'a> $imp for &'a $t {
+        impl $imp for &$t {
             type Output = <$t as $imp>::Output;
 
             #[inline]
diff --git a/src/libcore/iter/mod.rs b/src/libcore/iter/mod.rs
index 4e1dc108cc9..5dcca7ee0ca 100644
--- a/src/libcore/iter/mod.rs
+++ b/src/libcore/iter/mod.rs
@@ -326,8 +326,10 @@ pub use self::sources::{Empty, empty};
 pub use self::sources::{Once, once};
 #[unstable(feature = "iter_once_with", issue = "57581")]
 pub use self::sources::{OnceWith, once_with};
-#[unstable(feature = "iter_unfold", issue = "55977")]
-pub use self::sources::{FromFn, from_fn, Successors, successors};
+#[stable(feature = "iter_from_fn", since = "1.34.0")]
+pub use self::sources::{FromFn, from_fn};
+#[stable(feature = "iter_successors", since = "1.34.0")]
+pub use self::sources::{Successors, successors};
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::traits::{FromIterator, IntoIterator, DoubleEndedIterator, Extend};
diff --git a/src/libcore/iter/sources.rs b/src/libcore/iter/sources.rs
index 6f45f082d6a..74ff7f41d76 100644
--- a/src/libcore/iter/sources.rs
+++ b/src/libcore/iter/sources.rs
@@ -514,7 +514,6 @@ pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
 /// [module-level documentation]: index.html
 ///
 /// ```
-/// #![feature(iter_unfold)]
 /// let mut count = 0;
 /// let counter = std::iter::from_fn(move || {
 ///     // Increment our count. This is why we started at zero.
@@ -530,7 +529,7 @@ pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
 /// assert_eq!(counter.collect::<Vec<_>>(), &[1, 2, 3, 4, 5]);
 /// ```
 #[inline]
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_from_fn", since = "1.34.0")]
 pub fn from_fn<T, F>(f: F) -> FromFn<F>
     where F: FnMut() -> Option<T>
 {
@@ -544,10 +543,10 @@ pub fn from_fn<T, F>(f: F) -> FromFn<F>
 ///
 /// [`iter::from_fn`]: fn.from_fn.html
 #[derive(Clone)]
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_from_fn", since = "1.34.0")]
 pub struct FromFn<F>(F);
 
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_from_fn", since = "1.34.0")]
 impl<T, F> Iterator for FromFn<F>
     where F: FnMut() -> Option<T>
 {
@@ -559,7 +558,7 @@ impl<T, F> Iterator for FromFn<F>
     }
 }
 
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_from_fn", since = "1.34.0")]
 impl<F> fmt::Debug for FromFn<F> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("FromFn").finish()
@@ -572,13 +571,12 @@ impl<F> fmt::Debug for FromFn<F> {
 /// and calls the given `FnMut(&T) -> Option<T>` closure to compute each item’s successor.
 ///
 /// ```
-/// #![feature(iter_unfold)]
 /// use std::iter::successors;
 ///
 /// let powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
 /// assert_eq!(powers_of_10.collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
 /// ```
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_successors", since = "1.34.0")]
 pub fn successors<T, F>(first: Option<T>, succ: F) -> Successors<T, F>
     where F: FnMut(&T) -> Option<T>
 {
@@ -598,13 +596,13 @@ pub fn successors<T, F>(first: Option<T>, succ: F) -> Successors<T, F>
 ///
 /// [`successors`]: fn.successors.html
 #[derive(Clone)]
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_successors", since = "1.34.0")]
 pub struct Successors<T, F> {
     next: Option<T>,
     succ: F,
 }
 
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_successors", since = "1.34.0")]
 impl<T, F> Iterator for Successors<T, F>
     where F: FnMut(&T) -> Option<T>
 {
@@ -628,12 +626,12 @@ impl<T, F> Iterator for Successors<T, F>
     }
 }
 
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_successors", since = "1.34.0")]
 impl<T, F> FusedIterator for Successors<T, F>
     where F: FnMut(&T) -> Option<T>
 {}
 
-#[unstable(feature = "iter_unfold", issue = "55977")]
+#[stable(feature = "iter_successors", since = "1.34.0")]
 impl<T: fmt::Debug, F> fmt::Debug for Successors<T, F> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("Successors")
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 6fb67ea9c9a..5b7d5f45d92 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1215,7 +1215,7 @@ $EndFeature, "
 ```"),
             #[stable(feature = "num_wrapping", since = "1.2.0")]
             #[inline]
-            pub fn wrapping_neg(self) -> Self {
+            pub const fn wrapping_neg(self) -> Self {
                 self.overflowing_neg().0
             }
         }
@@ -1569,12 +1569,8 @@ assert_eq!(", stringify!($SelfT), "::MIN.overflowing_neg(), (", stringify!($Self
 ```"),
             #[inline]
             #[stable(feature = "wrapping", since = "1.7.0")]
-            pub fn overflowing_neg(self) -> (Self, bool) {
-                if self == Self::min_value() {
-                    (Self::min_value(), true)
-                } else {
-                    (-self, false)
-                }
+            pub const fn overflowing_neg(self) -> (Self, bool) {
+                ((!self).wrapping_add(1), self == Self::min_value())
             }
         }
 
@@ -3092,7 +3088,7 @@ assert_eq!(100", stringify!($SelfT), ".wrapping_rem_euclid(10), 0);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
         #[inline]
-        pub fn wrapping_neg(self) -> Self {
+        pub const fn wrapping_neg(self) -> Self {
             self.overflowing_neg().0
         }
 
@@ -3397,7 +3393,7 @@ assert_eq!(2", stringify!($SelfT), ".overflowing_neg(), (-2i32 as ", stringify!(
 ```"),
             #[inline]
             #[stable(feature = "wrapping", since = "1.7.0")]
-            pub fn overflowing_neg(self) -> (Self, bool) {
+            pub const fn overflowing_neg(self) -> (Self, bool) {
                 ((!self).wrapping_add(1), self != 0)
             }
         }
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 76ef36ac309..60aed7ce09d 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -874,7 +874,7 @@ impl<T> Option<T> {
     }
 }
 
-impl<'a, T: Copy> Option<&'a T> {
+impl<T: Copy> Option<&T> {
     /// Maps an `Option<&T>` to an `Option<T>` by copying the contents of the
     /// option.
     ///
@@ -895,7 +895,7 @@ impl<'a, T: Copy> Option<&'a T> {
     }
 }
 
-impl<'a, T: Copy> Option<&'a mut T> {
+impl<T: Copy> Option<&mut T> {
     /// Maps an `Option<&mut T>` to an `Option<T>` by copying the contents of the
     /// option.
     ///
@@ -916,7 +916,7 @@ impl<'a, T: Copy> Option<&'a mut T> {
     }
 }
 
-impl<'a, T: Clone> Option<&'a T> {
+impl<T: Clone> Option<&T> {
     /// Maps an `Option<&T>` to an `Option<T>` by cloning the contents of the
     /// option.
     ///
@@ -935,7 +935,7 @@ impl<'a, T: Clone> Option<&'a T> {
     }
 }
 
-impl<'a, T: Clone> Option<&'a mut T> {
+impl<T: Clone> Option<&mut T> {
     /// Maps an `Option<&mut T>` to an `Option<T>` by cloning the contents of the
     /// option.
     ///
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index a628fd0cfa4..d89443662df 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -2903,7 +2903,7 @@ macro_rules! iterator {
         }
 
         #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, T> ExactSizeIterator for $name<'a, T> {
+        impl<T> ExactSizeIterator for $name<'_, T> {
             #[inline(always)]
             fn len(&self) -> usize {
                 len!(self)
@@ -3098,10 +3098,10 @@ macro_rules! iterator {
         }
 
         #[stable(feature = "fused", since = "1.26.0")]
-        impl<'a, T> FusedIterator for $name<'a, T> {}
+        impl<T> FusedIterator for $name<'_, T> {}
 
         #[unstable(feature = "trusted_len", issue = "37572")]
-        unsafe impl<'a, T> TrustedLen for $name<'a, T> {}
+        unsafe impl<T> TrustedLen for $name<'_, T> {}
     }
 }
 
@@ -4365,8 +4365,8 @@ pub struct RChunks<'a, T:'a> {
 
 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> Clone for RChunks<'a, T> {
-    fn clone(&self) -> RChunks<'a, T> {
+impl<T> Clone for RChunks<'_, T> {
+    fn clone(&self) -> Self {
         RChunks {
             v: self.v,
             chunk_size: self.chunk_size,
@@ -4455,13 +4455,13 @@ impl<'a, T> DoubleEndedIterator for RChunks<'a, T> {
 }
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> ExactSizeIterator for RChunks<'a, T> {}
+impl<T> ExactSizeIterator for RChunks<'_, T> {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for RChunks<'a, T> {}
+unsafe impl<T> TrustedLen for RChunks<'_, T> {}
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> FusedIterator for RChunks<'a, T> {}
+impl<T> FusedIterator for RChunks<'_, T> {}
 
 #[doc(hidden)]
 #[stable(feature = "rchunks", since = "1.31.0")]
@@ -4580,13 +4580,13 @@ impl<'a, T> DoubleEndedIterator for RChunksMut<'a, T> {
 }
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> ExactSizeIterator for RChunksMut<'a, T> {}
+impl<T> ExactSizeIterator for RChunksMut<'_, T> {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for RChunksMut<'a, T> {}
+unsafe impl<T> TrustedLen for RChunksMut<'_, T> {}
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> FusedIterator for RChunksMut<'a, T> {}
+impl<T> FusedIterator for RChunksMut<'_, T> {}
 
 #[doc(hidden)]
 #[stable(feature = "rchunks", since = "1.31.0")]
@@ -4711,10 +4711,10 @@ impl<'a, T> ExactSizeIterator for RChunksExact<'a, T> {
 }
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for RChunksExact<'a, T> {}
+unsafe impl<T> TrustedLen for RChunksExact<'_, T> {}
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> FusedIterator for RChunksExact<'a, T> {}
+impl<T> FusedIterator for RChunksExact<'_, T> {}
 
 #[doc(hidden)]
 #[stable(feature = "rchunks", since = "1.31.0")]
@@ -4822,17 +4822,17 @@ impl<'a, T> DoubleEndedIterator for RChunksExactMut<'a, T> {
 }
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> ExactSizeIterator for RChunksExactMut<'a, T> {
+impl<T> ExactSizeIterator for RChunksExactMut<'_, T> {
     fn is_empty(&self) -> bool {
         self.v.is_empty()
     }
 }
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for RChunksExactMut<'a, T> {}
+unsafe impl<T> TrustedLen for RChunksExactMut<'_, T> {}
 
 #[stable(feature = "rchunks", since = "1.31.0")]
-impl<'a, T> FusedIterator for RChunksExactMut<'a, T> {}
+impl<T> FusedIterator for RChunksExactMut<'_, T> {}
 
 #[doc(hidden)]
 #[stable(feature = "rchunks", since = "1.31.0")]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 76a45e53684..8b51d846514 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -823,7 +823,7 @@ impl FusedIterator for Bytes<'_> {}
 unsafe impl TrustedLen for Bytes<'_> {}
 
 #[doc(hidden)]
-unsafe impl<'a> TrustedRandomAccess for Bytes<'a> {
+unsafe impl TrustedRandomAccess for Bytes<'_> {
     unsafe fn get_unchecked(&mut self, i: usize) -> u8 {
         self.0.get_unchecked(i)
     }
diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index 3e8549f8ae3..4cd734bad90 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -14,7 +14,6 @@
 #![feature(iter_copied)]
 #![feature(iter_nth_back)]
 #![feature(iter_once_with)]
-#![feature(iter_unfold)]
 #![feature(pattern)]
 #![feature(range_is_empty)]
 #![feature(raw)]
diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs
index 2c53e4832a8..03fe1fe5a7c 100644
--- a/src/libcore/tests/ptr.rs
+++ b/src/libcore/tests/ptr.rs
@@ -40,18 +40,17 @@ fn test() {
 }
 
 #[test]
-#[cfg(not(miri))] // This test performs invalid OOB pointer arithmetic
 fn test_is_null() {
     let p: *const isize = null();
     assert!(p.is_null());
 
-    let q = unsafe { p.offset(1) };
+    let q = p.wrapping_offset(1);
     assert!(!q.is_null());
 
     let mp: *mut isize = null_mut();
     assert!(mp.is_null());
 
-    let mq = unsafe { mp.offset(1) };
+    let mq = mp.wrapping_offset(1);
     assert!(!mq.is_null());
 
     // Pointers to unsized types -- slices
@@ -208,7 +207,6 @@ fn test_ptr_addition() {
 }
 
 #[test]
-#[cfg(not(miri))] // This test performs invalid OOB pointer arithmetic
 fn test_ptr_subtraction() {
     unsafe {
         let xs = vec![0,1,2,3,4,5,6,7,8,9];
@@ -224,8 +222,11 @@ fn test_ptr_subtraction() {
         let m_start = xs_mut.as_mut_ptr();
         let mut m_ptr = m_start.offset(9);
 
-        while m_ptr >= m_start {
+        loop {
             *m_ptr += *m_ptr;
+            if m_ptr == m_start {
+                break;
+            }
             m_ptr = m_ptr.offset(-1);
         }