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Rollup merge of #84337 - matklad:insert_or_insert, r=jyn514

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Clarify the difference between insert and get_or_insert

Took me a while to realize that the two are actually different.
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Dylan DPC 2021-04-20 11:08:27 +02:00 committed by GitHub
commit 9f03385499
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1 changed files with 35 additions and 29 deletions
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64
library/core/src/option.rs
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@ -594,34 +594,6 @@ impl<T> Option<T> {
}
}
/// Inserts `value` into the option then returns a mutable reference to it.
///
/// If the option already contains a value, the old value is dropped.
///
/// # Example
///
/// ```
/// let mut opt = None;
/// let val = opt.insert(1);
/// assert_eq!(*val, 1);
/// assert_eq!(opt.unwrap(), 1);
/// let val = opt.insert(2);
/// assert_eq!(*val, 2);
/// *val = 3;
/// assert_eq!(opt.unwrap(), 3);
/// ```
#[inline]
#[stable(feature = "option_insert", since = "1.53.0")]
pub fn insert(&mut self, value: T) -> &mut T {
*self = Some(value);
match self {
Some(v) => v,
// SAFETY: the code above just filled the option
None => unsafe { hint::unreachable_unchecked() },
}
}
/////////////////////////////////////////////////////////////////////////
// Iterator constructors
/////////////////////////////////////////////////////////////////////////
@ -849,12 +821,46 @@ impl<T> Option<T> {
}
/////////////////////////////////////////////////////////////////////////
// Entry-like operations to insert if None and return a reference
// Entry-like operations to insert a value and return a reference
/////////////////////////////////////////////////////////////////////////
/// Inserts `value` into the option then returns a mutable reference to it.
///
/// If the option already contains a value, the old value is dropped.
///
/// See also [`Option::get_or_insert`], which doesn't update the value if
/// the option already contains [`Some`].
///
/// # Example
///
/// ```
/// let mut opt = None;
/// let val = opt.insert(1);
/// assert_eq!(*val, 1);
/// assert_eq!(opt.unwrap(), 1);
/// let val = opt.insert(2);
/// assert_eq!(*val, 2);
/// *val = 3;
/// assert_eq!(opt.unwrap(), 3);
/// ```
#[inline]
#[stable(feature = "option_insert", since = "1.53.0")]
pub fn insert(&mut self, value: T) -> &mut T {
*self = Some(value);
match self {
Some(v) => v,
// SAFETY: the code above just filled the option
None => unsafe { hint::unreachable_unchecked() },
}
}
/// Inserts `value` into the option if it is [`None`], then
/// returns a mutable reference to the contained value.
///
/// See also [`Option::insert`], which updates the value even if
/// the option already contains [`Some`].
///
/// # Examples
///
/// ```