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Avoid unnecessary synchronization in {force,deref}_mut #231

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merged 4 commits into from
May 29, 2023
Merged

Avoid unnecessary synchronization in {force,deref}_mut #231

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8f2d2f5
Avoid unnecessary synchronization in `{force,deref}_mut`
danielhenrymantilla May 28, 2023
b5db23c
v1.17.2
danielhenrymantilla May 28, 2023
53ac97e
Make CI ensure the `Cargo.lock.msrv` file is up to date
danielhenrymantilla May 28, 2023
060943b
Update `.lock` file
danielhenrymantilla May 28, 2023
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26 changes: 18 additions & 8 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -796,8 +796,14 @@ pub mod unsync {
/// assert_eq!(*lazy, 92);
/// ```
pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
Self::force(this);
Self::get_mut(this).unwrap_or_else(|| unreachable!())
if this.cell.get_mut().is_none() {
let value = match this.init.get_mut().take() {
Some(f) => f(),
None => panic!("Lazy instance has previously been poisoned"),
};
this.cell = OnceCell::with_value(value);
}
this.cell.get_mut().unwrap_or_else(|| unreachable!())
}

/// Gets the reference to the result of this lazy value if
Expand Down Expand Up @@ -844,8 +850,7 @@ pub mod unsync {

impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F> {
fn deref_mut(&mut self) -> &mut T {
Lazy::force(self);
self.cell.get_mut().unwrap_or_else(|| unreachable!())
Lazy::force_mut(self)
}
}

Expand Down Expand Up @@ -1324,8 +1329,14 @@ pub mod sync {
/// assert_eq!(Lazy::force_mut(&mut lazy), &mut 92);
/// ```
pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
Self::force(this);
Self::get_mut(this).unwrap_or_else(|| unreachable!())
if this.cell.get_mut().is_none() {
let value = match this.init.get_mut().take() {
Some(f) => f(),
None => panic!("Lazy instance has previously been poisoned"),
};
this.cell = OnceCell::with_value(value);
}
this.cell.get_mut().unwrap_or_else(|| unreachable!())
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(Trying to rewrite this so as to avoiding the double-get_mut() on the happy path runs into polonius)

}

/// Gets the reference to the result of this lazy value if
Expand Down Expand Up @@ -1372,8 +1383,7 @@ pub mod sync {

impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F> {
fn deref_mut(&mut self) -> &mut T {
Lazy::force(self);
self.cell.get_mut().unwrap_or_else(|| unreachable!())
Lazy::force_mut(self)
}
}

Expand Down