Add Borrowed::as_unbound

Author: bschoenmaeckers

src/conversion.rs

@@ -15,7 +15,6 @@ use crate::{
 };
 use std::convert::Infallible;
 use std::marker::PhantomData;
-use std::mem::transmute;
 
 /// Defines a conversion from a Rust type to a Python object, which may fail.
 ///
@@ -150,7 +149,7 @@ impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &'a Bound<'_, T> {
     const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;
 
     fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
-         Ok(self.as_unbound().bind_borrowed(py))
+        Ok(self.as_unbound().bind_borrowed(py))
     }
 }
 
@@ -162,8 +161,8 @@ impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for Borrowed<'a, '_, T> {
     #[cfg(feature = "experimental-inspect")]
     const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;
 
-    fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
-        unsafe { Ok(transmute(self)) }
+    fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
+        Ok(self.as_unbound().bind_borrowed(py))
     }
 }
 
@@ -175,8 +174,8 @@ impl<'a, 'py, T: PyTypeCheck> IntoPyObject<'py> for &Borrowed<'a, '_, T> {
     #[cfg(feature = "experimental-inspect")]
     const OUTPUT_TYPE: PyStaticExpr = T::TYPE_HINT;
 
-    fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
-        unsafe { Ok(transmute(*self)) }
+    fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
+        Ok(self.as_unbound().bind_borrowed(py))
     }
 }
 

src/instance.rs

@@ -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() }
+    }
 }
 
 impl<'a, T: PyClass> Borrowed<'a, '_, T> {