Rollup merge of rust-lang#54687 - scottmcm:more-elision, r=dtolnay

Use impl_header_lifetime_elision in libcore

The feature is approved for stabilization, so let's use it to remove about 300 `'a`s.

Tracking issue for the feature: rust-lang#15872

src/libcore/borrow.rs

@@ -226,16 +226,16 @@ impl<T: ?Sized> BorrowMut<T> for T {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Borrow<T> for &'a T {
+impl<T: ?Sized> Borrow<T> for &T {
     fn borrow(&self) -> &T { &**self }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Borrow<T> for &'a mut T {
+impl<T: ?Sized> Borrow<T> for &mut T {
     fn borrow(&self) -> &T { &**self }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> BorrowMut<T> for &'a mut T {
+impl<T: ?Sized> BorrowMut<T> for &mut T {
     fn borrow_mut(&mut self) -> &mut T { &mut **self }
 }

src/libcore/cell.rs

@@ -1092,7 +1092,7 @@ impl<'b> BorrowRef<'b> {
     }
 }
 
-impl<'b> Drop for BorrowRef<'b> {
+impl Drop for BorrowRef<'_> {
     #[inline]
     fn drop(&mut self) {
         let borrow = self.borrow.get();
@@ -1101,9 +1101,9 @@ impl<'b> Drop for BorrowRef<'b> {
     }
 }
 
-impl<'b> Clone for BorrowRef<'b> {
+impl Clone for BorrowRef<'_> {
     #[inline]
-    fn clone(&self) -> BorrowRef<'b> {
+    fn clone(&self) -> Self {
         // Since this Ref exists, we know the borrow flag
         // is a reading borrow.
         let borrow = self.borrow.get();
@@ -1127,7 +1127,7 @@ pub struct Ref<'b, T: ?Sized + 'b> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, T: ?Sized> Deref for Ref<'b, T> {
+impl<T: ?Sized> Deref for Ref<'_, T> {
     type Target = T;
 
     #[inline]
@@ -1219,7 +1219,7 @@ impl<'b, T: ?Sized> Ref<'b, T> {
 impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Ref<'b, U>> for Ref<'b, T> {}
 
 #[stable(feature = "std_guard_impls", since = "1.20.0")]
-impl<'a, T: ?Sized + fmt::Display> fmt::Display for Ref<'a, T> {
+impl<T: ?Sized + fmt::Display> fmt::Display for Ref<'_, T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.value.fmt(f)
     }
@@ -1305,7 +1305,7 @@ struct BorrowRefMut<'b> {
     borrow: &'b Cell<BorrowFlag>,
 }
 
-impl<'b> Drop for BorrowRefMut<'b> {
+impl Drop for BorrowRefMut<'_> {
     #[inline]
     fn drop(&mut self) {
         let borrow = self.borrow.get();
@@ -1356,7 +1356,7 @@ pub struct RefMut<'b, T: ?Sized + 'b> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, T: ?Sized> Deref for RefMut<'b, T> {
+impl<T: ?Sized> Deref for RefMut<'_, T> {
     type Target = T;
 
     #[inline]
@@ -1366,7 +1366,7 @@ impl<'b, T: ?Sized> Deref for RefMut<'b, T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> {
+impl<T: ?Sized> DerefMut for RefMut<'_, T> {
     #[inline]
     fn deref_mut(&mut self) -> &mut T {
         self.value
@@ -1377,7 +1377,7 @@ impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> {
 impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<RefMut<'b, U>> for RefMut<'b, T> {}
 
 #[stable(feature = "std_guard_impls", since = "1.20.0")]
-impl<'a, T: ?Sized + fmt::Display> fmt::Display for RefMut<'a, T> {
+impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.value.fmt(f)
     }

src/libcore/clone.rs

@@ -204,7 +204,7 @@ mod impls {
 
     // Shared references can be cloned, but mutable references *cannot*!
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, T: ?Sized> Clone for &'a T {
+    impl<T: ?Sized> Clone for &T {
         #[inline]
         fn clone(&self) -> Self {
             *self

src/libcore/cmp.rs

@@ -1033,12 +1033,12 @@ mod impls {
         fn gt(&self, other: & &'b B) -> bool { PartialOrd::gt(*self, *other) }
     }
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, A: ?Sized> Ord for &'a A where A: Ord {
+    impl<A: ?Sized> Ord for &A where A: Ord {
         #[inline]
-        fn cmp(&self, other: & &'a A) -> Ordering { Ord::cmp(*self, *other) }
+        fn cmp(&self, other: &Self) -> Ordering { Ord::cmp(*self, *other) }
     }
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, A: ?Sized> Eq for &'a A where A: Eq {}
+    impl<A: ?Sized> Eq for &A where A: Eq {}
 
     // &mut pointers
 
@@ -1065,12 +1065,12 @@ mod impls {
         fn gt(&self, other: &&'b mut B) -> bool { PartialOrd::gt(*self, *other) }
     }
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, A: ?Sized> Ord for &'a mut A where A: Ord {
+    impl<A: ?Sized> Ord for &mut A where A: Ord {
         #[inline]
-        fn cmp(&self, other: &&'a mut A) -> Ordering { Ord::cmp(*self, *other) }
+        fn cmp(&self, other: &Self) -> Ordering { Ord::cmp(*self, *other) }
     }
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, A: ?Sized> Eq for &'a mut A where A: Eq {}
+    impl<A: ?Sized> Eq for &mut A where A: Eq {}
 
     #[stable(feature = "rust1", since = "1.0.0")]
     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a A where A: PartialEq<B> {

src/libcore/convert.rs

@@ -407,7 +407,7 @@ pub trait TryFrom<T>: Sized {
 
 // As lifts over &
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a T where T: AsRef<U>
+impl<T: ?Sized, U: ?Sized> AsRef<U> for &T where T: AsRef<U>
 {
     fn as_ref(&self) -> &U {
         <T as AsRef<U>>::as_ref(*self)
@@ -416,7 +416,7 @@ impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a T where T: AsRef<U>
 
 // As lifts over &mut
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a mut T where T: AsRef<U>
+impl<T: ?Sized, U: ?Sized> AsRef<U> for &mut T where T: AsRef<U>
 {
     fn as_ref(&self) -> &U {
         <T as AsRef<U>>::as_ref(*self)
@@ -433,7 +433,7 @@ impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a mut T where T: AsRef<U>
 
 // AsMut lifts over &mut
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized, U: ?Sized> AsMut<U> for &'a mut T where T: AsMut<U>
+impl<T: ?Sized, U: ?Sized> AsMut<U> for &mut T where T: AsMut<U>
 {
     fn as_mut(&mut self) -> &mut U {
         (*self).as_mut()

src/libcore/fmt/builders.rs

@@ -28,7 +28,7 @@ impl<'a> PadAdapter<'a> {
     }
 }
 
-impl<'a> fmt::Write for PadAdapter<'a> {
+impl fmt::Write for PadAdapter<'_> {
     fn write_str(&mut self, mut s: &str) -> fmt::Result {
         while !s.is_empty() {
             if self.on_newline {

src/libcore/fmt/mod.rs

@@ -208,7 +208,7 @@ pub trait Write {
         // requiring a `Sized` bound.
         struct Adapter<'a,T: ?Sized +'a>(&'a mut T);
 
-        impl<'a, T: ?Sized> Write for Adapter<'a, T>
+        impl<T: ?Sized> Write for Adapter<'_, T>
             where T: Write
         {
             fn write_str(&mut self, s: &str) -> Result {
@@ -229,7 +229,7 @@ pub trait Write {
 }
 
 #[stable(feature = "fmt_write_blanket_impl", since = "1.4.0")]
-impl<'a, W: Write + ?Sized> Write for &'a mut W {
+impl<W: Write + ?Sized> Write for &mut W {
     fn write_str(&mut self, s: &str) -> Result {
         (**self).write_str(s)
     }
@@ -291,8 +291,8 @@ pub struct ArgumentV1<'a> {
 
 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
            issue = "0")]
-impl<'a> Clone for ArgumentV1<'a> {
-    fn clone(&self) -> ArgumentV1<'a> {
+impl Clone for ArgumentV1<'_> {
+    fn clone(&self) -> Self {
         *self
     }
 }
@@ -436,14 +436,14 @@ pub struct Arguments<'a> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> Debug for Arguments<'a> {
+impl Debug for Arguments<'_> {
     fn fmt(&self, fmt: &mut Formatter) -> Result {
         Display::fmt(self, fmt)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> Display for Arguments<'a> {
+impl Display for Arguments<'_> {
     fn fmt(&self, fmt: &mut Formatter) -> Result {
         write(fmt.buf, *self)
     }
@@ -1884,7 +1884,7 @@ impl<'a> Formatter<'a> {
 }
 
 #[stable(since = "1.2.0", feature = "formatter_write")]
-impl<'a> Write for Formatter<'a> {
+impl Write for Formatter<'_> {
     fn write_str(&mut self, s: &str) -> Result {
         self.buf.write_str(s)
     }
@@ -1911,11 +1911,11 @@ macro_rules! fmt_refs {
     ($($tr:ident),*) => {
         $(
         #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, T: ?Sized + $tr> $tr for &'a T {
+        impl<T: ?Sized + $tr> $tr for &T {
             fn fmt(&self, f: &mut Formatter) -> Result { $tr::fmt(&**self, f) }
         }
         #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, T: ?Sized + $tr> $tr for &'a mut T {
+        impl<T: ?Sized + $tr> $tr for &mut T {
             fn fmt(&self, f: &mut Formatter) -> Result { $tr::fmt(&**self, f) }
         }
         )*
@@ -2039,14 +2039,14 @@ impl<T: ?Sized> Pointer for *mut T {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Pointer for &'a T {
+impl<T: ?Sized> Pointer for &T {
     fn fmt(&self, f: &mut Formatter) -> Result {
         Pointer::fmt(&(*self as *const T), f)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Pointer for &'a mut T {
+impl<T: ?Sized> Pointer for &mut T {
     fn fmt(&self, f: &mut Formatter) -> Result {
         Pointer::fmt(&(&**self as *const T), f)
     }
@@ -2153,14 +2153,14 @@ impl<T: ?Sized + Debug> Debug for RefCell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, T: ?Sized + Debug> Debug for Ref<'b, T> {
+impl<T: ?Sized + Debug> Debug for Ref<'_, T> {
     fn fmt(&self, f: &mut Formatter) -> Result {
         Debug::fmt(&**self, f)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, T: ?Sized + Debug> Debug for RefMut<'b, T> {
+impl<T: ?Sized + Debug> Debug for RefMut<'_, T> {
     fn fmt(&self, f: &mut Formatter) -> Result {
         Debug::fmt(&*(self.deref()), f)
     }

src/libcore/hash/mod.rs

@@ -361,7 +361,7 @@ pub trait Hasher {
 }
 
 #[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
-impl<'a, H: Hasher + ?Sized> Hasher for &'a mut H {
+impl<H: Hasher + ?Sized> Hasher for &mut H {
     fn finish(&self) -> u64 {
         (**self).finish()
     }
@@ -669,14 +669,14 @@ mod impls {
 
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, T: ?Sized + Hash> Hash for &'a T {
+    impl<T: ?Sized + Hash> Hash for &T {
         fn hash<H: Hasher>(&self, state: &mut H) {
             (**self).hash(state);
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, T: ?Sized + Hash> Hash for &'a mut T {
+    impl<T: ?Sized + Hash> Hash for &mut T {
         fn hash<H: Hasher>(&self, state: &mut H) {
             (**self).hash(state);
         }

src/libcore/iter/iterator.rs

@@ -2557,7 +2557,7 @@ fn select_fold1<I, B, FProj, FCmp>(mut it: I,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, I: Iterator + ?Sized> Iterator for &'a mut I {
+impl<I: Iterator + ?Sized> Iterator for &mut I {
     type Item = I::Item;
     fn next(&mut self) -> Option<I::Item> { (**self).next() }
     fn size_hint(&self) -> (usize, Option<usize>) { (**self).size_hint() }

src/libcore/iter/traits.rs

@@ -724,7 +724,7 @@ pub trait ExactSizeIterator: Iterator {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, I: ExactSizeIterator + ?Sized> ExactSizeIterator for &'a mut I {
+impl<I: ExactSizeIterator + ?Sized> ExactSizeIterator for &mut I {
     fn len(&self) -> usize {
         (**self).len()
     }
@@ -974,7 +974,7 @@ impl<T, U, E> Product<Result<U, E>> for Result<T, E>
 pub trait FusedIterator: Iterator {}
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<'a, I: FusedIterator + ?Sized> FusedIterator for &'a mut I {}
+impl<I: FusedIterator + ?Sized> FusedIterator for &mut I {}
 
 /// An iterator that reports an accurate length using size_hint.
 ///
@@ -999,4 +999,4 @@ impl<'a, I: FusedIterator + ?Sized> FusedIterator for &'a mut I {}
 pub unsafe trait TrustedLen : Iterator {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, I: TrustedLen + ?Sized> TrustedLen for &'a mut I {}
+unsafe impl<I: TrustedLen + ?Sized> TrustedLen for &mut I {}

src/libcore/lib.rs

@@ -87,6 +87,7 @@
 #![feature(doc_spotlight)]
 #![feature(extern_types)]
 #![feature(fundamental)]
+#![feature(impl_header_lifetime_elision)]
 #![feature(intrinsics)]
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]

src/libcore/marker.rs

@@ -584,9 +584,9 @@ impls! { PhantomData }
 
 mod impls {
     #[stable(feature = "rust1", since = "1.0.0")]
-    unsafe impl<'a, T: Sync + ?Sized> Send for &'a T {}
+    unsafe impl<T: Sync + ?Sized> Send for &T {}
     #[stable(feature = "rust1", since = "1.0.0")]
-    unsafe impl<'a, T: Send + ?Sized> Send for &'a mut T {}
+    unsafe impl<T: Send + ?Sized> Send for &mut T {}
 }
 
 /// Compiler-internal trait used to determine whether a type contains
@@ -600,8 +600,8 @@ impl<T: ?Sized> !Freeze for UnsafeCell<T> {}
 unsafe impl<T: ?Sized> Freeze for PhantomData<T> {}
 unsafe impl<T: ?Sized> Freeze for *const T {}
 unsafe impl<T: ?Sized> Freeze for *mut T {}
-unsafe impl<'a, T: ?Sized> Freeze for &'a T {}
-unsafe impl<'a, T: ?Sized> Freeze for &'a mut T {}
+unsafe impl<T: ?Sized> Freeze for &T {}
+unsafe impl<T: ?Sized> Freeze for &mut T {}
 
 /// Types which can be safely moved after being pinned.
 ///
@@ -689,6 +689,6 @@ mod copy_impls {
 
     // Shared references can be copied, but mutable references *cannot*!
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<'a, T: ?Sized> Copy for &'a T {}
+    impl<T: ?Sized> Copy for &T {}
 
 }

src/libcore/ops/deref.rs

@@ -83,14 +83,14 @@ pub trait Deref {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Deref for &'a T {
+impl<T: ?Sized> Deref for &T {
     type Target = T;
 
     fn deref(&self) -> &T { *self }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> Deref for &'a mut T {
+impl<T: ?Sized> Deref for &mut T {
     type Target = T;
 
     fn deref(&self) -> &T { *self }
@@ -174,6 +174,6 @@ pub trait DerefMut: Deref {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized> DerefMut for &'a mut T {
+impl<T: ?Sized> DerefMut for &mut T {
     fn deref_mut(&mut self) -> &mut T { *self }
 }