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Make IntoPyObject for Bound & Borrowed more generic #5831

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Merged
davidhewitt merged 1 commit into from
Feb 18, 2026
+22 −12
Merged

Make IntoPyObject for Bound & Borrowed more generic #5831

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1 change: 1 addition & 0 deletions newsfragments/5831.added.md
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Original file line number Diff line number Diff line change
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Add `Borrowed::as_unbound`
1 change: 1 addition & 0 deletions newsfragments/5831.changed.md
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Make `IntoPyObject` for `Bound` & `Borrowed` more generic
24 changes: 12 additions & 12 deletions src/conversion.rs
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Expand Up @@ -127,55 +127,55 @@ pub(crate) mod private {
}
}

impl<'py, T: PyTypeCheck> IntoPyObject<'py> for Bound<'py, T> {
impl<'py, T: PyTypeCheck> IntoPyObject<'py> for Bound<'_, T> {
type Target = T;
type Output = Bound<'py, Self::Target>;
type Error = Infallible;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;

fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self)
fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self.unbind().into_bound(py))
}
}

impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &'a Bound<'py, T> {
impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &'a Bound<'_, T> {
type Target = T;
type Output = Borrowed<'a, 'py, Self::Target>;
type Error = Infallible;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;

fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self.as_borrowed())
fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self.as_unbound().bind_borrowed(py))
}
}

impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for Borrowed<'a, 'py, T> {
impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for Borrowed<'a, '_, T> {
type Target = T;
type Output = Borrowed<'a, 'py, Self::Target>;
type Error = Infallible;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;

fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self)
fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self.as_unbound().bind_borrowed(py))
}
}

impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &Borrowed<'a, 'py, T> {
impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &Borrowed<'a, '_, T> {
type Target = T;
type Output = Borrowed<'a, 'py, Self::Target>;
type Error = Infallible;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;

fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(*self)
fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
Ok(self.as_unbound().bind_borrowed(py))
}
}

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8 changes: 8 additions & 0 deletions src/instance.rs
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Expand Up @@ -1075,6 +1075,14 @@ impl<'a, 'py, T> Borrowed<'a, 'py, T> {
pub unsafe fn cast_unchecked<U>(self) -> Borrowed<'a, 'py, U> {
Borrowed(self.0, PhantomData, self.2)
}

/// Removes the connection for this `Borrowed<T>` from the [`Python<'py>`] token,
/// allowing it to cross thread boundaries, without transferring ownership.
#[inline]
pub fn as_unbound(&self) -> &'a Py<T> {
// Safety: NonNull<ffi::PyObject> is layout-compatible with Py<T>
unsafe { NonNull::from(&self.0).cast().as_ref() }
}
Comment on lines +1082 to +1085
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@Icxolu Icxolu Feb 18, 2026

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I think this might be unsound. I think the &Py can only live as long as the reference to the Borrowed (&self) and not for 'a, as the pointer we get from self is only valid until the borrow ends at the end of the scope.

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@davidhewitt davidhewitt Feb 18, 2026

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You're absolutely right, thanks for catching this and sorry I missed it review!

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@Icxolu Icxolu Feb 18, 2026

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Glad I could catch it. Opened #5832 to revert this for now.

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@bschoenmaeckers bschoenmaeckers Feb 18, 2026 •
edited
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Sorry for my mistake, I will take a closer look tomorrow so I understand the relationship between these lifetimes better.

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@davidhewitt davidhewitt Feb 19, 2026

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No worries, I made a similar form of exactly this mistake many times when we were trying to implement the Bound API originally!

}

impl<'a, T: PyClass> Borrowed<'a, '_, T> {
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