auto merge of #7931 : blake2-ppc/rust/chain-mut-ref, r=pcwalton

First, clean up the uses of "None" and "Some" to always use consistent title case matching the variant names.

Add .chain_mut_ref() which is a missing method. A use case example for this method is extraction of an optional value from an Option\<Container\> value.

src/libstd/option.rs

@@ -118,13 +118,13 @@ pub fn mut_iter<'r>(&'r mut self) -> OptionMutIterator<'r, T> {
         }
     }
 
-    /// Returns true if the option equals `none`
+    /// Returns true if the option equals `None`
     #[inline]
     pub fn is_none(&self) -> bool {
         match *self { None => true, Some(_) => false }
     }
 
-    /// Returns true if the option contains some value
+    /// Returns true if the option contains a `Some` value
     #[inline]
     pub fn is_some(&self) -> bool { !self.is_none() }
 
@@ -158,6 +158,17 @@ pub fn chain_ref<'a, U>(&'a self, f: &fn(x: &'a T) -> Option<U>)
         }
     }
 
+    /// Update an optional value by optionally running its content by mut reference
+    /// through a function that returns an option.
+    #[inline]
+    pub fn chain_mut_ref<'a, U>(&'a mut self, f: &fn(x: &'a mut T) -> Option<U>)
+                                -> Option<U> {
+        match *self {
+            Some(ref mut x) => f(x),
+            None => None
+        }
+    }
+
     /// Filters an optional value using given function.
     #[inline(always)]
     pub fn filtered(self, f: &fn(t: &T) -> bool) -> Option<T> {
@@ -167,19 +178,19 @@ pub fn filtered(self, f: &fn(t: &T) -> bool) -> Option<T> {
         }
     }
 
-    /// Maps a `some` value from one type to another by reference
+    /// Maps a `Some` value from one type to another by reference
     #[inline]
     pub fn map<'a, U>(&'a self, f: &fn(&'a T) -> U) -> Option<U> {
         match *self { Some(ref x) => Some(f(x)), None => None }
     }
 
-    /// Maps a `some` value from one type to another by a mutable reference
+    /// Maps a `Some` value from one type to another by a mutable reference
     #[inline]
     pub fn map_mut<'a, U>(&'a mut self, f: &fn(&'a mut T) -> U) -> Option<U> {
         match *self { Some(ref mut x) => Some(f(x)), None => None }
     }
 
-    /// Maps a `some` value from one type to another by a mutable reference,
+    /// Maps a `Some` value from one type to another by a mutable reference,
     /// or returns a default value.
     #[inline]
     pub fn map_mut_default<'a, U>(&'a mut self, def: U, f: &fn(&'a mut T) -> U) -> U {
@@ -260,7 +271,7 @@ pub fn mutate_default(&mut self, def: T, f: &fn(T) -> T) {
     pub fn get_ref<'a>(&'a self) -> &'a T {
         match *self {
           Some(ref x) => x,
-          None => fail!("option::get_ref none")
+          None => fail!("option::get_ref None")
         }
     }
 
@@ -282,7 +293,7 @@ pub fn get_ref<'a>(&'a self) -> &'a T {
     pub fn get_mut_ref<'a>(&'a mut self) -> &'a mut T {
         match *self {
           Some(ref mut x) => x,
-          None => fail!("option::get_mut_ref none")
+          None => fail!("option::get_mut_ref None")
         }
     }
 
@@ -306,7 +317,7 @@ pub fn unwrap(self) -> T {
          */
         match self {
           Some(x) => x,
-          None => fail!("option::unwrap none")
+          None => fail!("option::unwrap None")
         }
     }
 
@@ -320,7 +331,7 @@ pub fn unwrap(self) -> T {
      */
     #[inline]
     pub fn take_unwrap(&mut self) -> T {
-        if self.is_none() { fail!("option::take_unwrap none") }
+        if self.is_none() { fail!("option::take_unwrap None") }
         self.take().unwrap()
     }
 
@@ -330,7 +341,7 @@ pub fn take_unwrap(&mut self) -> T {
      *
      * # Failure
      *
-     * Fails if the value equals `none`
+     * Fails if the value equals `None`
      */
     #[inline]
     pub fn expect(self, reason: &str) -> T {
@@ -358,7 +369,7 @@ pub fn expect(self, reason: &str) -> T {
     pub fn get(self) -> T {
         match self {
           Some(x) => return x,
-          None => fail!("option::get none")
+          None => fail!("option::get None")
         }
     }
 
@@ -368,7 +379,7 @@ pub fn get_or_default(self, def: T) -> T {
         match self { Some(x) => x, None => def }
     }
 
-    /// Applies a function zero or more times until the result is none.
+    /// Applies a function zero or more times until the result is None.
     #[inline]
     pub fn while_some(self, blk: &fn(v: T) -> Option<T>) {
         let mut opt = self;