Rollup merge of #51730 - MajorBreakfast:pin-get-mut-unchecked, r=withoutboats

New safe associated functions for PinMut

- Add safe `get_mut` and `map`
- Rename unsafe equivalents to `get_mut_unchecked` and `map_unchecked`

The discussion about this starts [in this comment](https://github.com/rust-lang/rust/issues/49150#issuecomment-399604573) on the tracking issue.

2 files changed, 11 insertions, 5 deletions

diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 31635ffa53c..08bd9289ab4 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -1119,6 +1119,12 @@ impl<'a, T: ?Sized + Unpin> PinMut<'a, T> {
     pub fn new(reference: &'a mut T) -> PinMut<'a, T> {
         PinMut { inner: reference }
     }
+
+    /// Get a mutable reference to the data inside of this `PinMut`.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub fn get_mut(this: PinMut<'a, T>) -> &'a mut T {
+        this.inner
+    }
 }
 
 
@@ -1150,21 +1156,21 @@ impl<'a, T: ?Sized> PinMut<'a, T> {
     /// the data out of the mutable reference you receive when you call this
     /// function.
     #[unstable(feature = "pin", issue = "49150")]
-    pub unsafe fn get_mut(this: PinMut<'a, T>) -> &'a mut T {
+    pub unsafe fn get_mut_unchecked(this: PinMut<'a, T>) -> &'a mut T {
         this.inner
     }
 
     /// Construct a new pin by mapping the interior value.
     ///
-    /// For example, if you  wanted to get a `PinMut` of a field of something, you
-    /// could use this to get access to that field in one line of code.
+    /// For example, if you  wanted to get a `PinMut` of a field of something,
+    /// you could use this to get access to that field in one line of code.
     ///
     /// This function is unsafe. You must guarantee that the data you return
     /// will not move so long as the argument value does not move (for example,
     /// because it is one of the fields of that value), and also that you do
     /// not move out of the argument you receive to the interior function.
     #[unstable(feature = "pin", issue = "49150")]
-    pub unsafe fn map<U, F>(this: PinMut<'a, T>, f: F) -> PinMut<'a, U> where
+    pub unsafe fn map_unchecked<U, F>(this: PinMut<'a, T>, f: F) -> PinMut<'a, U> where
         F: FnOnce(&mut T) -> &mut U
     {
         PinMut { inner: f(this.inner) }
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index e633d80a63c..20bc173f7e1 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -275,7 +275,7 @@ impl<T> Option<T> {
     #[unstable(feature = "pin", issue = "49150")]
     pub fn as_pin_mut<'a>(self: PinMut<'a, Self>) -> Option<PinMut<'a, T>> {
         unsafe {
-            PinMut::get_mut(self).as_mut().map(|x| PinMut::new_unchecked(x))
+            PinMut::get_mut_unchecked(self).as_mut().map(|x| PinMut::new_unchecked(x))
         }
     }