Add implementations of last in terms of next_back on a bunch of DoubleEndedIterators.

r?Manishearth

5 files changed, 24 insertions, 0 deletions

diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index 01b301cb43d..6cb160067f7 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -740,6 +740,10 @@ impl Iterator for Args {
         self.inner.next().map(|s| s.into_string().unwrap())
     }
     fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+    #[inline]
+    fn last(mut self) -> Option<String> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "env", since = "1.0.0")]
@@ -775,6 +779,8 @@ impl Iterator for ArgsOs {
     type Item = OsString;
     fn next(&mut self) -> Option<OsString> { self.inner.next() }
     fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+    #[inline]
+    fn last(mut self) -> Option<OsString> { self.next_back() }
 }
 
 #[stable(feature = "env", since = "1.0.0")]
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 1bbda9b5bcb..79ba37b2eb5 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -886,6 +886,11 @@ impl<'a> Iterator for Iter<'a> {
     fn next(&mut self) -> Option<&'a OsStr> {
         self.inner.next().map(Component::as_os_str)
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a OsStr> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -949,6 +954,11 @@ impl<'a> Iterator for Components<'a> {
         }
         None
     }
+
+    #[inline]
+    fn last(mut self) -> Option<Self::Item> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/libstd/sys/unix/args.rs b/src/libstd/sys/unix/args.rs
index 18de1096df2..f0594bb21bd 100644
--- a/src/libstd/sys/unix/args.rs
+++ b/src/libstd/sys/unix/args.rs
@@ -35,6 +35,8 @@ impl Iterator for Args {
     type Item = OsString;
     fn next(&mut self) -> Option<OsString> { self.iter.next() }
     fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
+    #[inline]
+    fn last(mut self) -> Option<OsString> { self.next_back() }
 }
 
 impl ExactSizeIterator for Args {
diff --git a/src/libstd/sys/wasm/args.rs b/src/libstd/sys/wasm/args.rs
index b3c77b86995..6766099c1ec 100644
--- a/src/libstd/sys/wasm/args.rs
+++ b/src/libstd/sys/wasm/args.rs
@@ -37,6 +37,10 @@ impl Iterator for Args {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[inline]
+    fn last(mut self) -> Option<OsString> {
+        self.next_back()
+    }
 }
 
 impl ExactSizeIterator for Args {
diff --git a/src/libstd/sys/windows/args.rs b/src/libstd/sys/windows/args.rs
index b04bb484eed..744d7ec59d3 100644
--- a/src/libstd/sys/windows/args.rs
+++ b/src/libstd/sys/windows/args.rs
@@ -181,6 +181,8 @@ impl Iterator for Args {
     type Item = OsString;
     fn next(&mut self) -> Option<OsString> { self.parsed_args_list.next() }
     fn size_hint(&self) -> (usize, Option<usize>) { self.parsed_args_list.size_hint() }
+    #[inline]
+    fn last(mut self) -> Option<OsString> { self.next_back() }
 }
 
 impl DoubleEndedIterator for Args {