Add a trait bound to From<Bound<'py, T>> for PyErr

src/coroutine.rs

@@ -78,7 +78,7 @@ impl Coroutine {
             (Some(exc), Some(cb)) => cb.throw(exc),
             (Some(exc), None) => {
                 self.close();
-                return Err(exc.into_bound(py).into());
+                return Err(PyErr::from_value_bound(exc.into_bound(py)));
             }
             (None, _) => {}
         }

src/err/mod.rs

@@ -982,7 +982,18 @@ impl PyErrArguments for PyDowncastErrorArguments {
     }
 }
 
-impl<'py, T> std::convert::From<Bound<'py, T>> for PyErr {
+/// Python exceptions that can be converted to [`PyErr`].
+///
+/// This is used to implement [`From<Bound<'_, T>> for PyErr`].
+///
+/// Users should not need to implement this trait directly. It is implemented automatically in the
+/// [`import_exception!`] and [`create_exception!`] macros.
+pub trait ToPyErr {}
+
+impl<'py, T> std::convert::From<Bound<'py, T>> for PyErr
+where
+    T: ToPyErr,
+{
     #[inline]
     fn from(err: Bound<'py, T>) -> PyErr {
         PyErr::from_value_bound(err.into_any())

src/exceptions.rs

@@ -52,6 +52,8 @@ macro_rules! impl_exception_boilerplate {
                 }
             }
         }
+
+        impl $crate::ToPyErr for $name {}
     };
 }
 

src/lib.rs

@@ -301,7 +301,7 @@ pub use crate::conversion::{AsPyPointer, FromPyObject, FromPyPointer, IntoPy, To
 #[allow(deprecated)]
 pub use crate::conversion::{PyTryFrom, PyTryInto};
 pub use crate::err::{
-    DowncastError, DowncastIntoError, PyDowncastError, PyErr, PyErrArguments, PyResult,
+    DowncastError, DowncastIntoError, PyDowncastError, PyErr, PyErrArguments, PyResult, ToPyErr,
 };
 pub use crate::gil::GILPool;
 #[cfg(not(PyPy))]

src/tests/common.rs

@@ -74,9 +74,9 @@ mod inner {
     #[pymethods(crate = "pyo3")]
     impl UnraisableCapture {
         pub fn hook(&mut self, unraisable: Bound<'_, PyAny>) {
-            let err = unraisable.getattr("exc_value").unwrap();
+            let err = PyErr::from_value_bound(unraisable.getattr("exc_value").unwrap());
             let instance = unraisable.getattr("object").unwrap();
-            self.capture = Some((err.into(), instance.into()));
+            self.capture = Some((err, instance.into()));
         }
     }
 

src/types/traceback.rs

@@ -147,7 +147,7 @@ except Exception as e:
                 Some(&locals),
             )
             .unwrap();
-            let err: PyErr = locals.get_item("err").unwrap().unwrap().into();
+            let err = PyErr::from_value_bound(locals.get_item("err").unwrap().unwrap());
             let traceback = err.value_bound(py).getattr("__traceback__").unwrap();
             assert!(err.traceback_bound(py).unwrap().is(&traceback));
         })