From f8428cf8d8193c1a6268a046afea9bea85d4d9fe Mon Sep 17 00:00:00 2001 From: Trevor Spiteri Date: Thu, 9 Jan 2020 14:51:58 +0100 Subject: [PATCH] doc: add Null-unchecked version section to mut pointer as_mut method The as_ref method already has a Null-unchecked version section, its example is a modification of the example in the main as_ref section. Similarly the example in this commit is a modification of the example in main as_mut section. --- src/libcore/ptr/mut_ptr.rs | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/src/libcore/ptr/mut_ptr.rs b/src/libcore/ptr/mut_ptr.rs index b3bb2f179b1..4bc0a3e9faa 100644 --- a/src/libcore/ptr/mut_ptr.rs +++ b/src/libcore/ptr/mut_ptr.rs @@ -250,6 +250,20 @@ impl *mut T { /// *first_value = 4; /// println!("{:?}", s); // It'll print: "[4, 2, 3]". /// ``` + /// + /// # Null-unchecked version + /// + /// If you are sure the pointer can never be null and are looking for some kind of + /// `as_mut_unchecked` that returns the `&mut T` instead of `Option<&mut T>`, know that + /// you can dereference the pointer directly. + /// + /// ``` + /// let mut s = [1, 2, 3]; + /// let ptr: *mut u32 = s.as_mut_ptr(); + /// let first_value = unsafe { &mut *ptr }; + /// *first_value = 4; + /// println!("{:?}", s); // It'll print: "[4, 2, 3]". + /// ``` #[stable(feature = "ptr_as_ref", since = "1.9.0")] #[inline] pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {