collections: Fix coding style and other review comments for Drain

Author: Ulrik Sverdrup

src/libcollections/range.rs

@@ -11,12 +11,7 @@
 //! Range syntax.
 
 use core::option::Option::{self, None, Some};
-use core::ops::{
-    RangeFull,
-    Range,
-    RangeTo,
-    RangeFrom
-};
+use core::ops::{RangeFull, Range, RangeTo, RangeFrom};
 
 #[unstable(feature = "collections", reason = "was just added")]
 /// **RangeArgument** is implemented by Rust's built-in range types, produced

src/libcollections/vec.rs

@@ -745,9 +745,7 @@ impl<T> Vec<T> {
     /// ```
     #[unstable(feature = "collections",
                reason = "recently added, matches RFC")]
-    pub fn drain<R>(&mut self, range: R) -> Drain<T> where
-        R: RangeArgument<usize>,
-    {
+    pub fn drain<R>(&mut self, range: R) -> Drain<T> where R: RangeArgument<usize> {
         // Memory safety
         //
         // When the Drain is first created, it shortens the length of
@@ -1828,8 +1826,7 @@ impl<T> Drop for IntoIter<T> {
 
 /// A draining iterator for `Vec<T>`.
 #[unstable(feature = "collections", reason = "recently added")]
-pub struct Drain<'a, T: 'a>
-{
+pub struct Drain<'a, T: 'a> {
     /// Index of tail to preserve
     tail_start: usize,
     /// Length of tail
@@ -1844,52 +1841,39 @@ unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> Iterator for Drain<'a, T>
-{
+impl<'a, T> Iterator for Drain<'a, T> {
     type Item = T;
 
     #[inline]
-    fn next(&mut self) -> Option<T>
-    {
-        match self.iter.next() {
-            None => None,
-            Some(elt) => {
-                unsafe {
-                    Some(ptr::read(elt as *const _))
-                }
+    fn next(&mut self) -> Option<T> {
+        self.iter.next().map(|elt|
+            unsafe {
+                ptr::read(elt as *const _)
             }
-        }
+        )
     }
 
-    fn size_hint(&self) -> (usize, Option<usize>)
-    {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> DoubleEndedIterator for Drain<'a, T>
-{
+impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
     #[inline]
-    fn next_back(&mut self) -> Option<T>
-    {
-        match self.iter.next_back() {
-            None => None,
-            Some(elt) => {
-                unsafe {
-                    Some(ptr::read(elt as *const _))
-                }
+    fn next_back(&mut self) -> Option<T> {
+        self.iter.next_back().map(|elt|
+            unsafe {
+                ptr::read(elt as *const _)
             }
-        }
+        )
     }
 }
 
 #[unsafe_destructor]
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> Drop for Drain<'a, T>
-{
-    fn drop(&mut self)
-    {
+impl<'a, T> Drop for Drain<'a, T> {
+    fn drop(&mut self) {
         // exhaust self first
         while let Some(_) = self.next() { }