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

Rollup of 12 pull requests

Successful merges:

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

Failed merges:

r? @ghost

Author: bors

Cargo.lock

@@ -3483,6 +3483,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_interface",
+ "rustc_lint",
  "rustc_metadata",
  "rustc_mir",
  "rustc_plugin",

src/liballoc/borrow.rs

@@ -207,6 +207,47 @@ impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
 }
 
 impl<B: ?Sized + ToOwned> Cow<'_, B> {
+    /// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow = Cow::Borrowed("moo");
+    /// assert!(cow.is_borrowed());
+    ///
+    /// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
+    /// assert!(!bull.is_borrowed());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    pub fn is_borrowed(&self) -> bool {
+        match *self {
+            Borrowed(_) => true,
+            Owned(_) => false,
+        }
+    }
+
+    /// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
+    /// assert!(cow.is_owned());
+    ///
+    /// let bull = Cow::Borrowed("...moo?");
+    /// assert!(!bull.is_owned());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    pub fn is_owned(&self) -> bool {
+        !self.is_borrowed()
+    }
+
     /// Acquires a mutable reference to the owned form of the data.
     ///
     /// Clones the data if it is not already owned.

src/liballoc/collections/vec_deque.rs

@@ -1817,7 +1817,7 @@ impl<T> VecDeque<T> {
             }
         }
 
-        return elem;
+        elem
     }
 
     /// Splits the `VecDeque` into two at the given index.

src/liballoc/lib.rs

@@ -85,6 +85,7 @@
 #![feature(const_generic_impls_guard)]
 #![feature(const_generics)]
 #![feature(const_in_array_repeat_expressions)]
+#![feature(cow_is_borrowed)]
 #![feature(dispatch_from_dyn)]
 #![feature(core_intrinsics)]
 #![feature(container_error_extra)]

src/liballoc/str.rs

@@ -456,7 +456,7 @@ impl str {
                 }
             }
         }
-        return s;
+        s
     }
 
     /// Converts a [`Box<str>`] into a [`String`] without copying or allocating.

src/liballoc/sync.rs

@@ -1638,7 +1638,7 @@ impl<T: ?Sized> Clone for Weak<T> {
             }
         }
 
-        return Weak { ptr: self.ptr };
+        Weak { ptr: self.ptr }
     }
 }
 

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);
             }
         }

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.

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;

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 {