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Rollup merge of rust-lang#59056 - scottmcm:even-fewer-lifetimes, r=sf…
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…ackler

Use lifetime contravariance to elide more lifetimes in core+alloc+std

Sample:
```diff
-    impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> {
+    impl<A: ?Sized, B: ?Sized> PartialEq<&mut B> for &mut A where A: PartialEq<B> {
         #[inline]
-        fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
+        fn eq(&self, other: &&mut B) -> bool { PartialEq::eq(*self, *other) }
         #[inline]
-        fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
+        fn ne(&self, other: &&mut B) -> bool { PartialEq::ne(*self, *other) }
     }
```

[I didn't know this worked](https://internals.rust-lang.org/t/why-can-you-use-different-unconstrained-lifetimes-to-implement-traits/9544/2?u=scottmcm) until recently, but since defining methods contravariantly in their lifetimes this way has worked back to Rust 1.0, we might as well take advantage of combining it with IHLE.
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Centril authored Mar 10, 2019
2 parents 56aeb70 + df4ea90 commit 6a94f44
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Showing 19 changed files with 93 additions and 93 deletions.
8 changes: 4 additions & 4 deletions src/liballoc/boxed.rs
Original file line number Diff line number Diff line change
Expand Up @@ -489,7 +489,7 @@ impl<T: ?Sized> From<Box<T>> for Pin<Box<T>> {
}

#[stable(feature = "box_from_slice", since = "1.17.0")]
impl<'a, T: Copy> From<&'a [T]> for Box<[T]> {
impl<T: Copy> From<&[T]> for Box<[T]> {
/// Converts a `&[T]` into a `Box<[T]>`
///
/// This conversion allocates on the heap
Expand All @@ -503,15 +503,15 @@ impl<'a, T: Copy> From<&'a [T]> for Box<[T]> {
///
/// println!("{:?}", boxed_slice);
/// ```
fn from(slice: &'a [T]) -> Box<[T]> {
fn from(slice: &[T]) -> Box<[T]> {
let mut boxed = unsafe { RawVec::with_capacity(slice.len()).into_box() };
boxed.copy_from_slice(slice);
boxed
}
}

#[stable(feature = "box_from_slice", since = "1.17.0")]
impl<'a> From<&'a str> for Box<str> {
impl From<&str> for Box<str> {
/// Converts a `&str` into a `Box<str>`
///
/// This conversion allocates on the heap
Expand All @@ -523,7 +523,7 @@ impl<'a> From<&'a str> for Box<str> {
/// println!("{}", boxed);
/// ```
#[inline]
fn from(s: &'a str) -> Box<str> {
fn from(s: &str) -> Box<str> {
unsafe { from_boxed_utf8_unchecked(Box::from(s.as_bytes())) }
}
}
Expand Down
4 changes: 2 additions & 2 deletions src/liballoc/rc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1145,15 +1145,15 @@ impl<T> From<T> for Rc<T> {
}

#[stable(feature = "shared_from_slice", since = "1.21.0")]
impl<'a, T: Clone> From<&'a [T]> for Rc<[T]> {
impl<T: Clone> From<&[T]> for Rc<[T]> {
#[inline]
fn from(v: &[T]) -> Rc<[T]> {
<Self as RcFromSlice<T>>::from_slice(v)
}
}

#[stable(feature = "shared_from_slice", since = "1.21.0")]
impl<'a> From<&'a str> for Rc<str> {
impl From<&str> for Rc<str> {
#[inline]
fn from(v: &str) -> Rc<str> {
let rc = Rc::<[u8]>::from(v.as_bytes());
Expand Down
4 changes: 2 additions & 2 deletions src/liballoc/string.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2172,9 +2172,9 @@ impl AsRef<[u8]> for String {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> From<&'a str> for String {
impl From<&str> for String {
#[inline]
fn from(s: &'a str) -> String {
fn from(s: &str) -> String {
s.to_owned()
}
}
Expand Down
16 changes: 8 additions & 8 deletions src/liballoc/vec.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2182,25 +2182,25 @@ impl<T> AsMut<[T]> for Vec<T> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
impl<T: Clone> From<&[T]> for Vec<T> {
#[cfg(not(test))]
fn from(s: &'a [T]) -> Vec<T> {
fn from(s: &[T]) -> Vec<T> {
s.to_vec()
}
#[cfg(test)]
fn from(s: &'a [T]) -> Vec<T> {
fn from(s: &[T]) -> Vec<T> {
crate::slice::to_vec(s)
}
}

#[stable(feature = "vec_from_mut", since = "1.19.0")]
impl<'a, T: Clone> From<&'a mut [T]> for Vec<T> {
impl<T: Clone> From<&mut [T]> for Vec<T> {
#[cfg(not(test))]
fn from(s: &'a mut [T]) -> Vec<T> {
fn from(s: &mut [T]) -> Vec<T> {
s.to_vec()
}
#[cfg(test)]
fn from(s: &'a mut [T]) -> Vec<T> {
fn from(s: &mut [T]) -> Vec<T> {
crate::slice::to_vec(s)
}
}
Expand Down Expand Up @@ -2231,8 +2231,8 @@ impl<T> From<Vec<T>> for Box<[T]> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> From<&'a str> for Vec<u8> {
fn from(s: &'a str) -> Vec<u8> {
impl From<&str> for Vec<u8> {
fn from(s: &str) -> Vec<u8> {
From::from(s.as_bytes())
}
}
Expand Down
2 changes: 1 addition & 1 deletion src/libcore/array.rs
Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ macro_rules! array_impls {
}

#[stable(feature = "try_from", since = "1.34.0")]
impl<'a, T> TryFrom<&'a [T]> for [T; $N] where T: Copy {
impl<T> TryFrom<&[T]> for [T; $N] where T: Copy {
type Error = TryFromSliceError;

fn try_from(slice: &[T]) -> Result<[T; $N], TryFromSliceError> {
Expand Down
48 changes: 24 additions & 24 deletions src/libcore/cmp.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1004,26 +1004,26 @@ mod impls {
// & pointers

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a A where A: PartialEq<B> {
impl<A: ?Sized, B: ?Sized> PartialEq<&B> for &A where A: PartialEq<B> {
#[inline]
fn eq(&self, other: & &'b B) -> bool { PartialEq::eq(*self, *other) }
fn eq(&self, other: & &B) -> bool { PartialEq::eq(*self, *other) }
#[inline]
fn ne(&self, other: & &'b B) -> bool { PartialEq::ne(*self, *other) }
fn ne(&self, other: & &B) -> bool { PartialEq::ne(*self, *other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b B> for &'a A where A: PartialOrd<B> {
impl<A: ?Sized, B: ?Sized> PartialOrd<&B> for &A where A: PartialOrd<B> {
#[inline]
fn partial_cmp(&self, other: &&'b B) -> Option<Ordering> {
fn partial_cmp(&self, other: &&B) -> Option<Ordering> {
PartialOrd::partial_cmp(*self, *other)
}
#[inline]
fn lt(&self, other: & &'b B) -> bool { PartialOrd::lt(*self, *other) }
fn lt(&self, other: & &B) -> bool { PartialOrd::lt(*self, *other) }
#[inline]
fn le(&self, other: & &'b B) -> bool { PartialOrd::le(*self, *other) }
fn le(&self, other: & &B) -> bool { PartialOrd::le(*self, *other) }
#[inline]
fn ge(&self, other: & &'b B) -> bool { PartialOrd::ge(*self, *other) }
fn ge(&self, other: & &B) -> bool { PartialOrd::ge(*self, *other) }
#[inline]
fn gt(&self, other: & &'b B) -> bool { PartialOrd::gt(*self, *other) }
fn gt(&self, other: & &B) -> bool { PartialOrd::gt(*self, *other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: ?Sized> Ord for &A where A: Ord {
Expand All @@ -1036,26 +1036,26 @@ mod impls {
// &mut pointers

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> {
impl<A: ?Sized, B: ?Sized> PartialEq<&mut B> for &mut A where A: PartialEq<B> {
#[inline]
fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
fn eq(&self, other: &&mut B) -> bool { PartialEq::eq(*self, *other) }
#[inline]
fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
fn ne(&self, other: &&mut B) -> bool { PartialEq::ne(*self, *other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b mut B> for &'a mut A where A: PartialOrd<B> {
impl<A: ?Sized, B: ?Sized> PartialOrd<&mut B> for &mut A where A: PartialOrd<B> {
#[inline]
fn partial_cmp(&self, other: &&'b mut B) -> Option<Ordering> {
fn partial_cmp(&self, other: &&mut B) -> Option<Ordering> {
PartialOrd::partial_cmp(*self, *other)
}
#[inline]
fn lt(&self, other: &&'b mut B) -> bool { PartialOrd::lt(*self, *other) }
fn lt(&self, other: &&mut B) -> bool { PartialOrd::lt(*self, *other) }
#[inline]
fn le(&self, other: &&'b mut B) -> bool { PartialOrd::le(*self, *other) }
fn le(&self, other: &&mut B) -> bool { PartialOrd::le(*self, *other) }
#[inline]
fn ge(&self, other: &&'b mut B) -> bool { PartialOrd::ge(*self, *other) }
fn ge(&self, other: &&mut B) -> bool { PartialOrd::ge(*self, *other) }
#[inline]
fn gt(&self, other: &&'b mut B) -> bool { PartialOrd::gt(*self, *other) }
fn gt(&self, other: &&mut B) -> bool { PartialOrd::gt(*self, *other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: ?Sized> Ord for &mut A where A: Ord {
Expand All @@ -1066,18 +1066,18 @@ mod impls {
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> {
impl<A: ?Sized, B: ?Sized> PartialEq<&mut B> for &A where A: PartialEq<B> {
#[inline]
fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
fn eq(&self, other: &&mut B) -> bool { PartialEq::eq(*self, *other) }
#[inline]
fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
fn ne(&self, other: &&mut B) -> bool { PartialEq::ne(*self, *other) }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a mut A where A: PartialEq<B> {
impl<A: ?Sized, B: ?Sized> PartialEq<&B> for &mut A where A: PartialEq<B> {
#[inline]
fn eq(&self, other: &&'b B) -> bool { PartialEq::eq(*self, *other) }
fn eq(&self, other: &&B) -> bool { PartialEq::eq(*self, *other) }
#[inline]
fn ne(&self, other: &&'b B) -> bool { PartialEq::ne(*self, *other) }
fn ne(&self, other: &&B) -> bool { PartialEq::ne(*self, *other) }
}
}
12 changes: 6 additions & 6 deletions src/libcore/internal_macros.rs
Original file line number Diff line number Diff line change
Expand Up @@ -37,21 +37,21 @@ macro_rules! forward_ref_binop {
}

#[$attr]
impl<'a> $imp<&'a $u> for $t {
impl $imp<&$u> for $t {
type Output = <$t as $imp<$u>>::Output;

#[inline]
fn $method(self, other: &'a $u) -> <$t as $imp<$u>>::Output {
fn $method(self, other: &$u) -> <$t as $imp<$u>>::Output {
$imp::$method(self, *other)
}
}

#[$attr]
impl<'a, 'b> $imp<&'a $u> for &'b $t {
impl $imp<&$u> for &$t {
type Output = <$t as $imp<$u>>::Output;

#[inline]
fn $method(self, other: &'a $u) -> <$t as $imp<$u>>::Output {
fn $method(self, other: &$u) -> <$t as $imp<$u>>::Output {
$imp::$method(*self, *other)
}
}
Expand All @@ -67,9 +67,9 @@ macro_rules! forward_ref_op_assign {
};
(impl $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
#[$attr]
impl<'a> $imp<&'a $u> for $t {
impl $imp<&$u> for $t {
#[inline]
fn $method(&mut self, other: &'a $u) {
fn $method(&mut self, other: &$u) {
$imp::$method(self, *other);
}
}
Expand Down
16 changes: 8 additions & 8 deletions src/libcore/ptr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2837,15 +2837,15 @@ impl<T: ?Sized> fmt::Pointer for Unique<T> {
}

#[unstable(feature = "ptr_internals", issue = "0")]
impl<'a, T: ?Sized> From<&'a mut T> for Unique<T> {
fn from(reference: &'a mut T) -> Self {
impl<T: ?Sized> From<&mut T> for Unique<T> {
fn from(reference: &mut T) -> Self {
unsafe { Unique { pointer: reference as *mut T, _marker: PhantomData } }
}
}

#[unstable(feature = "ptr_internals", issue = "0")]
impl<'a, T: ?Sized> From<&'a T> for Unique<T> {
fn from(reference: &'a T) -> Self {
impl<T: ?Sized> From<&T> for Unique<T> {
fn from(reference: &T) -> Self {
unsafe { Unique { pointer: reference as *const T, _marker: PhantomData } }
}
}
Expand Down Expand Up @@ -3049,17 +3049,17 @@ impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<'a, T: ?Sized> From<&'a mut T> for NonNull<T> {
impl<T: ?Sized> From<&mut T> for NonNull<T> {
#[inline]
fn from(reference: &'a mut T) -> Self {
fn from(reference: &mut T) -> Self {
unsafe { NonNull { pointer: reference as *mut T } }
}
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<'a, T: ?Sized> From<&'a T> for NonNull<T> {
impl<T: ?Sized> From<&T> for NonNull<T> {
#[inline]
fn from(reference: &'a T) -> Self {
fn from(reference: &T) -> Self {
unsafe { NonNull { pointer: reference as *const T } }
}
}
8 changes: 4 additions & 4 deletions src/libstd/collections/hash/set.rs
Original file line number Diff line number Diff line change
Expand Up @@ -850,7 +850,7 @@ impl<T, S> Default for HashSet<T, S>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, T, S> BitOr<&'b HashSet<T, S>> for &'a HashSet<T, S>
impl<T, S> BitOr<&HashSet<T, S>> for &HashSet<T, S>
where T: Eq + Hash + Clone,
S: BuildHasher + Default
{
Expand Down Expand Up @@ -882,7 +882,7 @@ impl<'a, 'b, T, S> BitOr<&'b HashSet<T, S>> for &'a HashSet<T, S>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, T, S> BitAnd<&'b HashSet<T, S>> for &'a HashSet<T, S>
impl<T, S> BitAnd<&HashSet<T, S>> for &HashSet<T, S>
where T: Eq + Hash + Clone,
S: BuildHasher + Default
{
Expand Down Expand Up @@ -914,7 +914,7 @@ impl<'a, 'b, T, S> BitAnd<&'b HashSet<T, S>> for &'a HashSet<T, S>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, T, S> BitXor<&'b HashSet<T, S>> for &'a HashSet<T, S>
impl<T, S> BitXor<&HashSet<T, S>> for &HashSet<T, S>
where T: Eq + Hash + Clone,
S: BuildHasher + Default
{
Expand Down Expand Up @@ -946,7 +946,7 @@ impl<'a, 'b, T, S> BitXor<&'b HashSet<T, S>> for &'a HashSet<T, S>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, T, S> Sub<&'b HashSet<T, S>> for &'a HashSet<T, S>
impl<T, S> Sub<&HashSet<T, S>> for &HashSet<T, S>
where T: Eq + Hash + Clone,
S: BuildHasher + Default
{
Expand Down
8 changes: 4 additions & 4 deletions src/libstd/error.rs
Original file line number Diff line number Diff line change
Expand Up @@ -337,7 +337,7 @@ impl From<String> for Box<dyn Error> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b> From<&'b str> for Box<dyn Error + Send + Sync + 'a> {
impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> {
/// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
///
/// # Examples
Expand All @@ -351,13 +351,13 @@ impl<'a, 'b> From<&'b str> for Box<dyn Error + Send + Sync + 'a> {
/// assert!(
/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
/// ```
fn from(err: &'b str) -> Box<dyn Error + Send + Sync + 'a> {
fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> {
From::from(String::from(err))
}
}

#[stable(feature = "string_box_error", since = "1.6.0")]
impl<'a> From<&'a str> for Box<dyn Error> {
impl From<&str> for Box<dyn Error> {
/// Converts a [`str`] into a box of dyn [`Error`].
///
/// # Examples
Expand All @@ -370,7 +370,7 @@ impl<'a> From<&'a str> for Box<dyn Error> {
/// let a_boxed_error = Box::<Error>::from(a_str_error);
/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
/// ```
fn from(err: &'a str) -> Box<dyn Error> {
fn from(err: &str) -> Box<dyn Error> {
From::from(String::from(err))
}
}
Expand Down
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