Auto merge of #65733 - Centril:rollup-0zth66f, r=Centril

Rollup of 12 pull requests

Successful merges:

 - #64178 (More Clippy fixes for alloc, core and std)
 - #65144 (Add Cow::is_borrowed and Cow::is_owned)
 - #65193 (Lockless LintStore)
 - #65479 (Add the `matches!( $expr, $pat ) -> bool` macro)
 - #65518 (Avoid ICE when checking `Destination` of `break` inside a closure)
 - #65583 (rustc_metadata: use a table for super_predicates, fn_sig, impl_trait_ref.)
 - #65641 (Derive `Rustc{En,De}codable` for `TokenStream`.)
 - #65648 (Eliminate `intersect_opt`.)
 - #65657 (Remove `InternedString`)
 - #65691 (Update E0659 error code long explanation to 2018 edition)
 - #65696 (Fix an issue with const inference variables sticking around under Chalk + NLL)
 - #65704 (relax ExactSizeIterator bound on write_bytes)

Failed merges:

r? @ghost

4 files changed, 34 insertions, 9 deletions

diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index 8413b2e0ac4..0e83a282b18 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -2025,7 +2025,7 @@ impl<T: ?Sized> Pointer for *const T {
         if f.alternate() {
             f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
 
-            if let None = f.width {
+            if f.width.is_none() {
                 f.width = Some(((mem::size_of::<usize>() * 8) / 4) + 2);
             }
         }
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 1320e63df06..35558e3abcd 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -238,6 +238,33 @@ macro_rules! debug_assert_ne {
     ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_ne!($($arg)*); })
 }
 
+/// Returns whether the given expression matches any of the given patterns.
+///
+/// Like in a `match` expression, the pattern can be optionally followed by `if`
+/// and a guard expression that has access to names bound by the pattern.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(matches_macro)]
+///
+/// let foo = 'f';
+/// assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
+///
+/// let bar = Some(4);
+/// assert!(matches!(bar, Some(x) if x > 2));
+/// ```
+#[macro_export]
+#[unstable(feature = "matches_macro", issue = "65721")]
+macro_rules! matches {
+    ($expression:expr, $( $pattern:pat )|+ $( if $guard: expr )?) => {
+        match $expression {
+            $( $pattern )|+ $( if $guard )? => true,
+            _ => false
+        }
+    }
+}
+
 /// Unwraps a result or propagates its error.
 ///
 /// The `?` operator was added to replace `try!` and should be used instead.
diff --git a/src/libcore/num/dec2flt/algorithm.rs b/src/libcore/num/dec2flt/algorithm.rs
index fa3c8075378..ed89852dc48 100644
--- a/src/libcore/num/dec2flt/algorithm.rs
+++ b/src/libcore/num/dec2flt/algorithm.rs
@@ -143,13 +143,12 @@ pub fn fast_path<T: RawFloat>(integral: &[u8], fractional: &[u8], e: i64) -> Opt
 /// > not a bound for the true error, but bounds the difference between the approximation z and
 /// > the best possible approximation that uses p bits of significand.)
 pub fn bellerophon<T: RawFloat>(f: &Big, e: i16) -> T {
-    let slop;
-    if f <= &Big::from_u64(T::MAX_SIG) {
+    let slop = if f <= &Big::from_u64(T::MAX_SIG) {
         // The cases abs(e) < log5(2^N) are in fast_path()
-        slop = if e >= 0 { 0 } else { 3 };
+        if e >= 0 { 0 } else { 3 }
     } else {
-        slop = if e >= 0 { 1 } else { 4 };
-    }
+        if e >= 0 { 1 } else { 4 }
+    };
     let z = rawfp::big_to_fp(f).mul(&power_of_ten(e)).normalize();
     let exp_p_n = 1 << (P - T::SIG_BITS as u32);
     let lowbits: i64 = (z.f % exp_p_n) as i64;
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 9eb29eae7f7..89f2d7ab29c 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -837,9 +837,8 @@ impl<T> Option<T> {
     #[inline]
     #[stable(feature = "option_entry", since = "1.20.0")]
     pub fn get_or_insert_with<F: FnOnce() -> T>(&mut self, f: F) -> &mut T {
-        match *self {
-            None => *self = Some(f()),
-            _ => (),
+        if let None = *self {
+            *self = Some(f());
         }
 
         match *self {