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add insert to Option #77392

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merged 7 commits into from
Oct 24, 2020
Merged

add insert to Option #77392

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9b90e17
add `insert` and `insert_with` to `Option`
Canop Oct 1, 2020
e8df2a4
remove `option.insert_with`
Canop Oct 1, 2020
60a96ca
more tests in option.insert, code cleaning in option
Canop Oct 1, 2020
cc8b77a
fix naming unconsistency between function doc and prototype
Canop Oct 3, 2020
3955779
Update library/core/src/option.rs
Canop Oct 23, 2020
415a8e5
Update library/core/src/option.rs
Canop Oct 23, 2020
216d0fe
add tracking issue number to option_insert feature gate
Canop Oct 23, 2020
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44 changes: 37 additions & 7 deletions library/core/src/option.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -562,6 +562,36 @@ impl<T> Option<T> {
}
}

/// Inserts `value` into the option then returns a mutable reference to it.
///
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/// If the option already contains a value, the old value is dropped.
///
/// # Example
///
/// ```
/// #![feature(option_insert)]
///
/// 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]
#[unstable(feature = "option_insert", reason = "newly added", issue = "78271")]
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
/////////////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -792,7 +822,7 @@ impl<T> Option<T> {
// Entry-like operations to insert if None and return a reference
/////////////////////////////////////////////////////////////////////////

/// Inserts `v` into the option if it is [`None`], then
/// Inserts `value` into the option if it is [`None`], then
/// returns a mutable reference to the contained value.
///
/// # Examples
Expand All @@ -811,12 +841,12 @@ impl<T> Option<T> {
/// ```
#[inline]
#[stable(feature = "option_entry", since = "1.20.0")]
pub fn get_or_insert(&mut self, v: T) -> &mut T {
self.get_or_insert_with(|| v)
pub fn get_or_insert(&mut self, value: T) -> &mut T {
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self.get_or_insert_with(|| value)
}

/// Inserts a value computed from `f` into the option if it is [`None`], then
/// returns a mutable reference to the contained value.
/// Inserts a value computed from `f` into the option if it is [`None`],
/// then returns a mutable reference to the contained value.
///
/// # Examples
///
Expand All @@ -839,8 +869,8 @@ impl<T> Option<T> {
*self = Some(f());
}

match *self {
Some(ref mut v) => v,
match self {
Some(v) => v,
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If we're changing this method anyway, might as well call insert:

match self {
    Some(v) => v,
    None => self.insert(f()),
}

(GitHub didn't let me add this as a change suggestion)

// SAFETY: a `None` variant for `self` would have been replaced by a `Some`
// variant in the code above.
None => unsafe { hint::unreachable_unchecked() },
Expand Down