Rollup merge of #59056 - scottmcm:even-fewer-lifetimes, r=sfackler

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.

11 files changed, 38 insertions, 38 deletions

diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index 8a599c11b20..f2111f2d9e0 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -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
 {
@@ -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
 {
@@ -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
 {
@@ -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
 {
diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 2858308e8f8..3eb289501cb 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -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
@@ -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
@@ -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))
     }
 }
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 139680e526f..ad3f45bfada 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -690,8 +690,8 @@ impl<'a> From<Cow<'a, CStr>> for CString {
 }
 
 #[stable(feature = "box_from_c_str", since = "1.17.0")]
-impl<'a> From<&'a CStr> for Box<CStr> {
-    fn from(s: &'a CStr) -> Box<CStr> {
+impl From<&CStr> for Box<CStr> {
+    fn from(s: &CStr) -> Box<CStr> {
         let boxed: Box<[u8]> = Box::from(s.to_bytes_with_nul());
         unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
     }
@@ -767,7 +767,7 @@ impl From<CString> for Arc<CStr> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a CStr> for Arc<CStr> {
+impl From<&CStr> for Arc<CStr> {
     #[inline]
     fn from(s: &CStr) -> Arc<CStr> {
         let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
@@ -789,7 +789,7 @@ impl From<CString> for Rc<CStr> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a CStr> for Rc<CStr> {
+impl From<&CStr> for Rc<CStr> {
     #[inline]
     fn from(s: &CStr) -> Rc<CStr> {
         let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
@@ -1268,8 +1268,8 @@ impl ToOwned for CStr {
 }
 
 #[stable(feature = "cstring_asref", since = "1.7.0")]
-impl<'a> From<&'a CStr> for CString {
-    fn from(s: &'a CStr) -> CString {
+impl From<&CStr> for CString {
+    fn from(s: &CStr) -> CString {
         s.to_owned()
     }
 }
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index f68eaeb9c7e..3a0590021c9 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -357,8 +357,8 @@ impl From<String> for OsString {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for OsString {
-    fn from(s: &'a T) -> OsString {
+impl<T: ?Sized + AsRef<OsStr>> From<&T> for OsString {
+    fn from(s: &T) -> OsString {
         s.as_ref().to_os_string()
     }
 }
@@ -421,8 +421,8 @@ impl PartialEq<OsString> for str {
 }
 
 #[stable(feature = "os_str_str_ref_eq", since = "1.29.0")]
-impl<'a> PartialEq<&'a str> for OsString {
-    fn eq(&self, other: &&'a str) -> bool {
+impl PartialEq<&str> for OsString {
+    fn eq(&self, other: &&str) -> bool {
         **self == **other
     }
 }
@@ -656,8 +656,8 @@ impl OsStr {
 }
 
 #[stable(feature = "box_from_os_str", since = "1.17.0")]
-impl<'a> From<&'a OsStr> for Box<OsStr> {
-    fn from(s: &'a OsStr) -> Box<OsStr> {
+impl From<&OsStr> for Box<OsStr> {
+    fn from(s: &OsStr) -> Box<OsStr> {
         let rw = Box::into_raw(s.inner.into_box()) as *mut OsStr;
         unsafe { Box::from_raw(rw) }
     }
@@ -707,7 +707,7 @@ impl From<OsString> for Arc<OsStr> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a OsStr> for Arc<OsStr> {
+impl From<&OsStr> for Arc<OsStr> {
     #[inline]
     fn from(s: &OsStr) -> Arc<OsStr> {
         let arc = s.inner.into_arc();
@@ -729,7 +729,7 @@ impl From<OsString> for Rc<OsStr> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a OsStr> for Rc<OsStr> {
+impl From<&OsStr> for Rc<OsStr> {
     #[inline]
     fn from(s: &OsStr) -> Rc<OsStr> {
         let rc = s.inner.into_rc();
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 858a5778b81..ea3fcd8ce28 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1456,8 +1456,8 @@ impl PathBuf {
 }
 
 #[stable(feature = "box_from_path", since = "1.17.0")]
-impl<'a> From<&'a Path> for Box<Path> {
-    fn from(path: &'a Path) -> Box<Path> {
+impl From<&Path> for Box<Path> {
+    fn from(path: &Path) -> Box<Path> {
         let boxed: Box<OsStr> = path.inner.into();
         let rw = Box::into_raw(boxed) as *mut Path;
         unsafe { Box::from_raw(rw) }
@@ -1494,8 +1494,8 @@ impl Clone for Box<Path> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for PathBuf {
-    fn from(s: &'a T) -> PathBuf {
+impl<T: ?Sized + AsRef<OsStr>> From<&T> for PathBuf {
+    fn from(s: &T) -> PathBuf {
         PathBuf::from(s.as_ref().to_os_string())
     }
 }
@@ -1630,7 +1630,7 @@ impl From<PathBuf> for Arc<Path> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a Path> for Arc<Path> {
+impl From<&Path> for Arc<Path> {
     /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: &Path) -> Arc<Path> {
@@ -1650,7 +1650,7 @@ impl From<PathBuf> for Rc<Path> {
 }
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
-impl<'a> From<&'a Path> for Rc<Path> {
+impl From<&Path> for Rc<Path> {
     /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: &Path) -> Rc<Path> {
diff --git a/src/libstd/sys/cloudabi/shims/net.rs b/src/libstd/sys/cloudabi/shims/net.rs
index 50d72dc7b24..6d2a4962ab4 100644
--- a/src/libstd/sys/cloudabi/shims/net.rs
+++ b/src/libstd/sys/cloudabi/shims/net.rs
@@ -297,10 +297,10 @@ impl Iterator for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
+impl TryFrom<&str> for LookupHost {
     type Error = io::Error;
 
-    fn try_from(_v: &'a str) -> io::Result<LookupHost> {
+    fn try_from(_v: &str) -> io::Result<LookupHost> {
         unsupported()
     }
 }
diff --git a/src/libstd/sys/redox/net/mod.rs b/src/libstd/sys/redox/net/mod.rs
index a172763f613..dbaa140ed8a 100644
--- a/src/libstd/sys/redox/net/mod.rs
+++ b/src/libstd/sys/redox/net/mod.rs
@@ -35,7 +35,7 @@ impl Iterator for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
+impl TryFrom<&str> for LookupHost {
     type Error = io::Error;
 
     fn try_from(s: &str) -> io::Result<LookupHost> {
diff --git a/src/libstd/sys/sgx/net.rs b/src/libstd/sys/sgx/net.rs
index ab8b2681393..e5e42e3d0b0 100644
--- a/src/libstd/sys/sgx/net.rs
+++ b/src/libstd/sys/sgx/net.rs
@@ -420,10 +420,10 @@ impl Iterator for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
+impl TryFrom<&str> for LookupHost {
     type Error = io::Error;
 
-    fn try_from(v: &'a str) -> io::Result<LookupHost> {
+    fn try_from(v: &str) -> io::Result<LookupHost> {
         LookupHost::new(v.to_owned())
     }
 }
diff --git a/src/libstd/sys/unix/l4re.rs b/src/libstd/sys/unix/l4re.rs
index b6e8cc73894..b9e725371a3 100644
--- a/src/libstd/sys/unix/l4re.rs
+++ b/src/libstd/sys/unix/l4re.rs
@@ -447,10 +447,10 @@ pub mod net {
     unsafe impl Send for LookupHost {}
 
 
-    impl<'a> TryFrom<&'a str> for LookupHost {
+    impl TryFrom<&str> for LookupHost {
         type Error = io::Error;
 
-        fn try_from(_v: &'a str) -> io::Result<LookupHost> {
+        fn try_from(_v: &str) -> io::Result<LookupHost> {
             unimpl!();
         }
     }
diff --git a/src/libstd/sys/wasm/net.rs b/src/libstd/sys/wasm/net.rs
index 1249832fb09..a2ea2dfbbc0 100644
--- a/src/libstd/sys/wasm/net.rs
+++ b/src/libstd/sys/wasm/net.rs
@@ -298,10 +298,10 @@ impl Iterator for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
+impl TryFrom<&str> for LookupHost {
     type Error = io::Error;
 
-    fn try_from(_v: &'a str) -> io::Result<LookupHost> {
+    fn try_from(_v: &str) -> io::Result<LookupHost> {
         unsupported()
     }
 }
diff --git a/src/libstd/sys_common/net.rs b/src/libstd/sys_common/net.rs
index 36721171b17..b9505aaa69b 100644
--- a/src/libstd/sys_common/net.rs
+++ b/src/libstd/sys_common/net.rs
@@ -157,7 +157,7 @@ impl Drop for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
+impl TryFrom<&str> for LookupHost {
     type Error = io::Error;
 
     fn try_from(s: &str) -> io::Result<LookupHost> {