Use more impl header lifetime elision

There are two big categories of changes in here

- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop` & `Debug`)
- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)

I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations where the flipped one cannot elide the lifetime.

2 files changed, 4 insertions, 4 deletions

diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 765452e0288..7e82f33ad8a 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -659,8 +659,8 @@ impl fmt::Debug for CStr {
 }
 
 #[stable(feature = "cstr_default", since = "1.10.0")]
-impl<'a> Default for &'a CStr {
-    fn default() -> &'a CStr {
+impl Default for &CStr {
+    fn default() -> Self {
         const SLICE: &[c_char] = &[0];
         unsafe { CStr::from_ptr(SLICE.as_ptr()) }
     }
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index f8176892513..5429079f5b8 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -778,10 +778,10 @@ impl Default for Box<OsStr> {
 }
 
 #[stable(feature = "osstring_default", since = "1.9.0")]
-impl<'a> Default for &'a OsStr {
+impl Default for &OsStr {
     /// Creates an empty `OsStr`.
     #[inline]
-    fn default() -> &'a OsStr {
+    fn default() -> Self {
         OsStr::new("")
     }
 }