bjoernager/rust
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Apply requested API changes to cell_update

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Do the following:

* Switch to `impl FnOnce` rather than a generic `F`.
* Change `update` to return nothing.

This was discussed at a libs-api meeting [1].

Tracking issue: https://github.com/rust-lang/rust/issues/50186

[1]: https://github.com/rust-lang/rust/pull/134446#issuecomment-2770842949
This commit is contained in:
Trevor Gross 2025-04-02 18:15:50 +00:00
parent 4f0de4c81d
commit 072aa9e66f
2 changed files with 6 additions and 13 deletions
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15
library/core/src/cell.rs
View file

@ -544,7 +544,7 @@ impl<T: Copy> Cell<T> {
unsafe { *self.value.get() } unsafe { *self.value.get() }
} }
/// Updates the contained value using a function and returns the new value. /// Updates the contained value using a function.
/// ///
/// # Examples /// # Examples
/// ///
@ -554,21 +554,14 @@ impl<T: Copy> Cell<T> {
/// use std::cell::Cell; /// use std::cell::Cell;
/// ///
/// let c = Cell::new(5); /// let c = Cell::new(5);
/// let new = c.update(|x| x + 1); /// c.update(|x| x + 1);
///
/// assert_eq!(new, 6);
/// assert_eq!(c.get(), 6); /// assert_eq!(c.get(), 6);
/// ``` /// ```
#[inline] #[inline]
#[unstable(feature = "cell_update", issue = "50186")] #[unstable(feature = "cell_update", issue = "50186")]
pub fn update<F>(&self, f: F) -> T pub fn update(&self, f: impl FnOnce(T) -> T) {
where
F: FnOnce(T) -> T,
{
let old = self.get(); let old = self.get();
let new = f(old); self.set(f(old));
self.set(new);
new
} }
} }

4
library/coretests/tests/cell.rs
View file

@ -50,10 +50,10 @@ fn smoketest_cell() {
fn cell_update() { fn cell_update() {
let x = Cell::new(10); let x = Cell::new(10);
assert_eq!(x.update(|x| x + 5), 15); x.update(|x| x + 5);
assert_eq!(x.get(), 15); assert_eq!(x.get(), 15);
assert_eq!(x.update(|x| x / 3), 5); x.update(|x| x / 3);
assert_eq!(x.get(), 5); assert_eq!(x.get(), 5);
} }