add Py2Borrowed::to_owned

Author: davidhewitt

src/instance.rs

@@ -228,6 +228,17 @@ pub(crate) struct Py2Borrowed<'a, 'py, T>(
     Python<'py>,
 );
 
+impl<'py, T> Py2Borrowed<'_, 'py, T> {
+    /// Creates a new owned `Py2` from this borrowed reference by increasing the reference count.
+    pub(crate) fn to_owned(self) -> Py2<'py, T> {
+        unsafe { ffi::Py_INCREF(self.as_ptr()) };
+        Py2(
+            self.py(),
+            ManuallyDrop::new(unsafe { Py::from_non_null(self.0) }),
+        )
+    }
+}
+
 impl<'a, 'py> Py2Borrowed<'a, 'py, PyAny> {
     /// # Safety
     /// This is similar to `std::slice::from_raw_parts`, the lifetime `'a` is completely defined by

src/types/list.rs

@@ -4,6 +4,7 @@ use std::iter::FusedIterator;
 use crate::err::{self, PyResult};
 use crate::ffi::{self, Py_ssize_t};
 use crate::ffi_ptr_ext::FfiPtrExt;
+use crate::instance::Py2Borrowed;
 use crate::internal_tricks::get_ssize_index;
 use crate::types::{PySequence, PyTuple};
 use crate::{Py2, PyAny, PyObject, Python, ToPyObject};
@@ -391,7 +392,7 @@ impl<'py> PyListMethods<'py> for Py2<'py, PyList> {
             // PyList_GetItem return borrowed ptr; must make owned for safety (see #890).
             ffi::PyList_GetItem(self.as_ptr(), index as Py_ssize_t)
                 .assume_borrowed_or_err(self.py())
-                .map(|borrowed_any| borrowed_any.clone())
+                .map(Py2Borrowed::to_owned)
         }
     }