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Auto merge of #63233 - RalfJung:get_unchecked, r=Centril

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clarify that unchecked indexing is UB even if the reference is never used
This commit is contained in:
bors 2019-08-04 07:53:25 +00:00
commit 5170a3f45a
1 changed files with 16 additions and 4 deletions
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20
src/libcore/slice/mod.rs
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@ -292,10 +292,13 @@ impl<T> [T] {
/// Returns a reference to an element or subslice, without doing bounds
/// checking.
///
/// This is generally not recommended, use with caution! For a safe
/// alternative see [`get`].
/// This is generally not recommended, use with caution!
/// Calling this method with an out-of-bounds index is *[undefined behavior]*
/// even if the resulting reference is not used.
/// For a safe alternative see [`get`].
///
/// [`get`]: #method.get
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
///
/// # Examples
///
@ -317,10 +320,13 @@ impl<T> [T] {
/// Returns a mutable reference to an element or subslice, without doing
/// bounds checking.
///
/// This is generally not recommended, use with caution! For a safe
/// alternative see [`get_mut`].
/// This is generally not recommended, use with caution!
/// Calling this method with an out-of-bounds index is *[undefined behavior]*
/// even if the resulting reference is not used.
/// For a safe alternative see [`get_mut`].
///
/// [`get_mut`]: #method.get_mut
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
///
/// # Examples
///
@ -2629,11 +2635,17 @@ pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
/// Returns a shared reference to the output at this location, without
/// performing any bounds checking.
/// Calling this method with an out-of-bounds index is *[undefined behavior]*
/// even if the resulting reference is not used.
/// [undefined behavior]: ../../reference/behavior-considered-undefined.html
#[unstable(feature = "slice_index_methods", issue = "0")]
unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
/// Returns a mutable reference to the output at this location, without
/// performing any bounds checking.
/// Calling this method with an out-of-bounds index is *[undefined behavior]*
/// even if the resulting reference is not used.
/// [undefined behavior]: ../../reference/behavior-considered-undefined.html
#[unstable(feature = "slice_index_methods", issue = "0")]
unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;