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clarify that unchecked indexing is UB even if the reference is never used

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This commit is contained in:
Ralf Jung 2019-08-03 12:46:20 +02:00
parent d7270712cb
commit f44abba4ec
1 changed files with 12 additions and 4 deletions
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16
src/libcore/slice/mod.rs
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@ -292,8 +292,10 @@ 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 UB even if the resulting
/// reference is not used.
/// For a safe alternative see [`get`].
///
/// [`get`]: #method.get
///
@ -317,8 +319,10 @@ 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 UB even if the resulting
/// reference is not used.
/// For a safe alternative see [`get_mut`].
///
/// [`get_mut`]: #method.get_mut
///
@ -2629,11 +2633,15 @@ 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 UB even if the resulting
/// reference is not used.
#[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 UB even if the resulting
/// reference is not used.
#[unstable(feature = "slice_index_methods", issue = "0")]
unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;