add blanket IntoPyObject implementation for &&T (#4680)

src/conversion.rs

@@ -333,6 +333,20 @@ impl<'a, 'py, T> IntoPyObject<'py> for &'a Py<T> {
     }
 }
 
+impl<'a, 'py, T> IntoPyObject<'py> for &&'a T
+where
+    &'a T: IntoPyObject<'py>,
+{
+    type Target = <&'a T as IntoPyObject<'py>>::Target;
+    type Output = <&'a T as IntoPyObject<'py>>::Output;
+    type Error = <&'a T as IntoPyObject<'py>>::Error;
+
+    #[inline]
+    fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
+        (*self).into_pyobject(py)
+    }
+}
+
 /// Extract a type from a Python object.
 ///
 ///

src/tests/hygiene/misc.rs

@@ -71,7 +71,7 @@ struct IntoPyObject2<'a> {
 #[pyo3(crate = "crate")]
 struct IntoPyObject3<'py>(i32, crate::Bound<'py, crate::PyAny>); // tuple case
 
-#[derive(crate::IntoPyObject)]
+#[derive(crate::IntoPyObject, crate::IntoPyObjectRef)]
 #[pyo3(crate = "crate")]
 struct IntoPyObject4<'a, 'py> {
     callable: &'a crate::Bound<'py, crate::PyAny>, // struct case

tests/ui/invalid_property_args.stderr

@@ -55,14 +55,14 @@ error[E0277]: `PhantomData<i32>` cannot be converted to a Python object
    = help: the trait `IntoPyObject<'_>` is not implemented for `PhantomData<i32>`, which is required by `for<'py> PhantomData<i32>: PyO3GetField<'py>`
    = note: implement `IntoPyObject` for `&PhantomData<i32>` or `IntoPyObject + Clone` for `PhantomData<i32>` to define the conversion
    = help: the following other types implement trait `IntoPyObject<'py>`:
+             &&'a T
              &&OsStr
              &&Path
              &&str
              &'a (T0, T1)
              &'a (T0, T1, T2)
              &'a (T0, T1, T2, T3)
              &'a (T0, T1, T2, T3, T4)
-             &'a (T0, T1, T2, T3, T4, T5)
            and $N others
    = note: required for `PhantomData<i32>` to implement `for<'py> PyO3GetField<'py>`
 note: required by a bound in `PyClassGetterGenerator::<ClassT, FieldT, Offset, false, false, false, false, false>::generate`

tests/ui/missing_intopy.stderr

@@ -8,14 +8,14 @@ error[E0277]: `Blah` cannot be converted to a Python object
   = note: if you do not wish to have a corresponding Python type, implement it manually
   = note: if you do not own `Blah` you can perform a manual conversion to one of the types in `pyo3::types::*`
   = help: the following other types implement trait `IntoPyObject<'py>`:
+            &&'a T
             &&OsStr
             &&Path
             &&str
             &'a (T0, T1)
             &'a (T0, T1, T2)
             &'a (T0, T1, T2, T3)
             &'a (T0, T1, T2, T3, T4)
-            &'a (T0, T1, T2, T3, T4, T5)
           and $N others
 note: required by a bound in `UnknownReturnType::<T>::wrap`
  --> src/impl_/wrap.rs