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add slice::replace #76902

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add slice::replace #76902

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24 changes: 24 additions & 0 deletions library/core/src/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3059,6 +3059,30 @@ impl<T> [T] {

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}

/// Moves `value` into `self[index]`, returning the old value.
///
/// Neither value is dropped.
///
/// # Panics
///
/// Panics if `index` is out of bounds.
///
/// # Examples
///
/// ```
/// #![feature(slice_replace)]
///
/// let mut v = [1, 2, 3];
/// let r = v.replace(1, 20);
///
/// assert_eq!(v, [1, 20, 3]);
/// assert_eq!(r, 2);
/// ```
#[unstable(feature = "slice_replace", reason = "new API", issue = "none")]
pub fn replace(&mut self, index: usize, value: T) -> T {
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nit: don't bother making this change until we find out whether libs wants to move forward, but note that mem::replace is must_use, so this one probably should be too -- maybe something like

#[must_use = "if you don't need the old value, you can just assign the new value directly with `*slice[index] = value;`"]

mem::replace(&mut self[index], value)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
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