Auto merge of #28629 - arielb1:supertrait-self, r=eddyb

[rust.git] / src / libcore / mem.rs

diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 86b331d220a3b30e0b55ab2d6a672e2271145a14..193b8d6d620de46dcd17c85e5bc0d80e81fb5acf 100644 (file)
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -247,7 +247,7 @@ pub unsafe fn zeroed<T>() -> T {
 /// This function is expected to be deprecated with the transition
 /// to non-zeroing drop.
 #[inline]
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 pub unsafe fn dropped<T>() -> T {
     #[inline(always)]
     unsafe fn dropped_impl<T>() -> T { intrinsics::init_dropped() }
@@ -434,6 +434,11 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
 /// While this does call the argument's implementation of `Drop`, it will not
 /// release any borrows, as borrows are based on lexical scope.
 ///
+/// This effectively does nothing for
+/// [types which implement `Copy`](../../book/ownership.html#copy-types),
+/// e.g. integers. Such values are copied and _then_ moved into the function,
+/// so the value persists after this function call.
+///
 /// # Examples
 ///
 /// Basic usage:
@@ -486,6 +491,21 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
 /// let borrow = x.borrow();
 /// println!("{}", *borrow);
 /// ```
+///
+/// Integers and other types implementing `Copy` are unaffected by `drop()`
+///
+/// ```
+/// #[derive(Copy, Clone)]
+/// struct Foo(u8);
+///
+/// let x = 1;
+/// let y = Foo(2);
+/// drop(x); // a copy of `x` is moved and dropped
+/// drop(y); // a copy of `y` is moved and dropped
+///
+/// println!("x: {}, y: {}", x, y.0); // still available
+/// ```
+///
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn drop<T>(_x: T) { }
@@ -510,22 +530,22 @@ macro_rules! repeat_u8_as_u64 {
 // But having the sign bit set is a pain, so 0x1d is probably better.
 //
 // And of course, 0x00 brings back the old world of zero'ing on drop.
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 #[allow(missing_docs)]
 pub const POST_DROP_U8: u8 = 0x1d;
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 #[allow(missing_docs)]
 pub const POST_DROP_U32: u32 = repeat_u8_as_u32!(POST_DROP_U8);
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 #[allow(missing_docs)]
 pub const POST_DROP_U64: u64 = repeat_u8_as_u64!(POST_DROP_U8);
 
 #[cfg(target_pointer_width = "32")]
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 #[allow(missing_docs)]
 pub const POST_DROP_USIZE: usize = POST_DROP_U32 as usize;
 #[cfg(target_pointer_width = "64")]
-#[unstable(feature = "filling_drop")]
+#[unstable(feature = "filling_drop", issue = "5016")]
 #[allow(missing_docs)]
 pub const POST_DROP_USIZE: usize = POST_DROP_U64 as usize;
 
@@ -558,33 +578,3 @@ pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
     #![allow(trivial_casts)]
     ptr::read(src as *const T as *const U)
 }
-
-/// Transforms lifetime of the second pointer to match the first.
-#[inline]
-#[unstable(feature = "copy_lifetime",
-           reason = "this function may be removed in the future due to its \
-                     questionable utility")]
-#[deprecated(since = "1.2.0",
-             reason = "unclear that this function buys more safety and \
-                       lifetimes are generally not handled as such in unsafe \
-                       code today")]
-pub unsafe fn copy_lifetime<'a, S: ?Sized, T: ?Sized + 'a>(_ptr: &'a S,
-                                                        ptr: &T) -> &'a T {
-    transmute(ptr)
-}
-
-/// Transforms lifetime of the second mutable pointer to match the first.
-#[inline]
-#[unstable(feature = "copy_lifetime",
-           reason = "this function may be removed in the future due to its \
-                     questionable utility")]
-#[deprecated(since = "1.2.0",
-             reason = "unclear that this function buys more safety and \
-                       lifetimes are generally not handled as such in unsafe \
-                       code today")]
-pub unsafe fn copy_mut_lifetime<'a, S: ?Sized, T: ?Sized + 'a>(_ptr: &'a S,
-                                                               ptr: &mut T)
-                                                              -> &'a mut T
-{
-    transmute(ptr)
-}