add types for built-in singletons

newsfragments/3408.added.md

@@ -0,0 +1 @@
+Add types for `None`, `Ellipsis`, and `NotImplemented`

src/conversion.rs

@@ -263,19 +263,6 @@ where
     }
 }
 
-/// `()` is converted to Python `None`.
-impl ToPyObject for () {
-    fn to_object(&self, py: Python<'_>) -> PyObject {
-        py.None()
-    }
-}
-
-impl IntoPy<PyObject> for () {
-    fn into_py(self, py: Python<'_>) -> PyObject {
-        py.None()
-    }
-}
-
 impl IntoPy<PyObject> for &'_ PyAny {
     #[inline]
     fn into_py(self, py: Python<'_>) -> PyObject {

src/marker.rs

@@ -118,7 +118,9 @@
 use crate::err::{self, PyDowncastError, PyErr, PyResult};
 use crate::gil::{GILGuard, GILPool, SuspendGIL};
 use crate::impl_::not_send::NotSend;
-use crate::types::{PyAny, PyDict, PyModule, PyString, PyType};
+use crate::types::{
+    PyAny, PyDict, PyEllipsis, PyModule, PyNone, PyNotImplemented, PyString, PyType,
+};
 use crate::version::PythonVersionInfo;
 use crate::{ffi, FromPyPointer, IntoPy, Py, PyNativeType, PyObject, PyTryFrom, PyTypeInfo};
 use std::ffi::{CStr, CString};
@@ -690,21 +692,21 @@ impl<'py> Python<'py> {
     #[allow(non_snake_case)] // the Python keyword starts with uppercase
     #[inline]
     pub fn None(self) -> PyObject {
-        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_None()) }
+        PyNone::get(self).into()
     }
 
     /// Gets the Python builtin value `Ellipsis`, or `...`.
     #[allow(non_snake_case)] // the Python keyword starts with uppercase
     #[inline]
     pub fn Ellipsis(self) -> PyObject {
-        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_Ellipsis()) }
+        PyEllipsis::get(self).into()
     }
 
     /// Gets the Python builtin value `NotImplemented`.
     #[allow(non_snake_case)] // the Python keyword starts with uppercase
     #[inline]
     pub fn NotImplemented(self) -> PyObject {
-        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_NotImplemented()) }
+        PyNotImplemented::get(self).into()
     }
 
     /// Gets the running Python interpreter version as a string.

src/types/ellipsis.rs

@@ -0,0 +1,60 @@
+use crate::{ffi, PyAny, PyDowncastError, PyTryFrom, Python};
+
+/// Represents the Python `Ellipsis` object.
+#[repr(transparent)]
+pub struct PyEllipsis(PyAny);
+
+pyobject_native_type_named!(PyEllipsis);
+pyobject_native_type_extract!(PyEllipsis);
+
+impl PyEllipsis {
+    /// Returns the `Ellipsis` object.
+    #[inline]
+    pub fn get(py: Python<'_>) -> &PyEllipsis {
+        unsafe { py.from_borrowed_ptr(ffi::Py_Ellipsis()) }
+    }
+}
+
+impl<'v> PyTryFrom<'v> for PyEllipsis {
+    fn try_from<V: Into<&'v PyAny>>(value: V) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        let value: &PyAny = value.into();
+        if unsafe { ffi::Py_Ellipsis() == value.as_ptr() } {
+            return unsafe { Ok(value.downcast_unchecked()) };
+        }
+        Err(PyDowncastError::new(value, "ellipsis"))
+    }
+
+    fn try_from_exact<V: Into<&'v PyAny>>(
+        value: V,
+    ) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        value.into().downcast()
+    }
+
+    unsafe fn try_from_unchecked<V: Into<&'v PyAny>>(value: V) -> &'v Self {
+        let ptr = value.into() as *const _ as *const PyEllipsis;
+        &*ptr
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::types::{PyDict, PyEllipsis};
+    use crate::Python;
+
+    #[test]
+    fn test_ellipsis_is_itself() {
+        Python::with_gil(|py| {
+            assert!(PyEllipsis::get(py)
+                .downcast::<PyEllipsis>()
+                .unwrap()
+                .is_ellipsis());
+        })
+    }
+
+    #[test]
+    fn test_dict_is_not_ellipsis() {
+        Python::with_gil(|py| {
+            assert!(PyDict::new(py).downcast::<PyEllipsis>().is_err());
+        })
+    }
+}

src/types/mod.rs

@@ -16,6 +16,7 @@ pub use self::datetime::{
 pub use self::dict::{IntoPyDict, PyDict};
 #[cfg(not(PyPy))]
 pub use self::dict::{PyDictItems, PyDictKeys, PyDictValues};
+pub use self::ellipsis::PyEllipsis;
 pub use self::floatob::PyFloat;
 #[cfg(all(not(Py_LIMITED_API), not(PyPy)))]
 pub use self::frame::PyFrame;
@@ -27,6 +28,8 @@ pub use self::iterator::PyIterator;
 pub use self::list::PyList;
 pub use self::mapping::PyMapping;
 pub use self::module::PyModule;
+pub use self::none::PyNone;
+pub use self::notimplemented::PyNotImplemented;
 pub use self::num::PyLong;
 pub use self::num::PyLong as PyInt;
 #[cfg(not(PyPy))]
@@ -278,6 +281,7 @@ mod complex;
 #[cfg(not(Py_LIMITED_API))]
 mod datetime;
 mod dict;
+mod ellipsis;
 mod floatob;
 #[cfg(all(not(Py_LIMITED_API), not(PyPy)))]
 mod frame;
@@ -287,6 +291,8 @@ mod iterator;
 pub(crate) mod list;
 mod mapping;
 mod module;
+mod none;
+mod notimplemented;
 mod num;
 #[cfg(not(PyPy))]
 mod pysuper;

src/types/none.rs

@@ -0,0 +1,86 @@
+use crate::{ffi, IntoPy, PyAny, PyDowncastError, PyObject, PyTryFrom, Python, ToPyObject};
+
+/// Represents the Python `None` object.
+#[repr(transparent)]
+pub struct PyNone(PyAny);
+
+pyobject_native_type_named!(PyNone);
+pyobject_native_type_extract!(PyNone);
+
+impl PyNone {
+    /// Returns the `None` object.
+    #[inline]
+    pub fn get(py: Python<'_>) -> &PyNone {
+        unsafe { py.from_borrowed_ptr(ffi::Py_None()) }
+    }
+}
+
+impl<'v> PyTryFrom<'v> for PyNone {
+    fn try_from<V: Into<&'v PyAny>>(value: V) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        let value: &PyAny = value.into();
+        if value.is_none() {
+            return unsafe { Ok(value.downcast_unchecked()) };
+        }
+        Err(PyDowncastError::new(value, "NoneType"))
+    }
+
+    fn try_from_exact<V: Into<&'v PyAny>>(
+        value: V,
+    ) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        value.into().downcast()
+    }
+
+    unsafe fn try_from_unchecked<V: Into<&'v PyAny>>(value: V) -> &'v Self {
+        let ptr = value.into() as *const _ as *const PyNone;
+        &*ptr
+    }
+}
+
+/// `()` is converted to Python `None`.
+impl ToPyObject for () {
+    fn to_object(&self, py: Python<'_>) -> PyObject {
+        PyNone::get(py).into()
+    }
+}
+
+impl IntoPy<PyObject> for () {
+    #[inline]
+    fn into_py(self, py: Python<'_>) -> PyObject {
+        PyNone::get(py).into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::types::{PyDict, PyNone};
+    use crate::{IntoPy, PyObject, Python, ToPyObject};
+
+    #[test]
+    fn test_none_is_none() {
+        Python::with_gil(|py| {
+            assert!(PyNone::get(py).downcast::<PyNone>().unwrap().is_none());
+        })
+    }
+
+    #[test]
+    fn test_unit_to_object_is_none() {
+        Python::with_gil(|py| {
+            assert!(().to_object(py).downcast::<PyNone>(py).is_ok());
+        })
+    }
+
+    #[test]
+    fn test_unit_into_py_is_none() {
+        Python::with_gil(|py| {
+            let obj: PyObject = ().into_py(py);
+            assert!(obj.downcast::<PyNone>(py).is_ok());
+        })
+    }
+
+    #[test]
+    fn test_dict_is_not_none() {
+        Python::with_gil(|py| {
+            assert!(PyDict::new(py).downcast::<PyNone>().is_err());
+        })
+    }
+}

src/types/notimplemented.rs

@@ -0,0 +1,60 @@
+use crate::{ffi, PyAny, PyDowncastError, PyTryFrom, Python};
+
+/// Represents the Python `NotImplemented` object.
+#[repr(transparent)]
+pub struct PyNotImplemented(PyAny);
+
+pyobject_native_type_named!(PyNotImplemented);
+pyobject_native_type_extract!(PyNotImplemented);
+
+impl PyNotImplemented {
+    /// Returns the `NotImplemented` object.
+    #[inline]
+    pub fn get(py: Python<'_>) -> &PyNotImplemented {
+        unsafe { py.from_borrowed_ptr(ffi::Py_NotImplemented()) }
+    }
+}
+
+impl<'v> PyTryFrom<'v> for PyNotImplemented {
+    fn try_from<V: Into<&'v PyAny>>(value: V) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        let value: &PyAny = value.into();
+        if unsafe { ffi::Py_NotImplemented() == value.as_ptr() } {
+            return unsafe { Ok(value.downcast_unchecked()) };
+        }
+        Err(PyDowncastError::new(value, "NotImplementedType"))
+    }
+
+    fn try_from_exact<V: Into<&'v PyAny>>(
+        value: V,
+    ) -> Result<&'v Self, crate::PyDowncastError<'v>> {
+        value.into().downcast()
+    }
+
+    unsafe fn try_from_unchecked<V: Into<&'v PyAny>>(value: V) -> &'v Self {
+        let ptr = value.into() as *const _ as *const PyNotImplemented;
+        &*ptr
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::types::{PyDict, PyNotImplemented};
+    use crate::Python;
+
+    #[test]
+    fn test_notimplemented_is_itself() {
+        Python::with_gil(|py| {
+            assert!(PyNotImplemented::get(py)
+                .downcast::<PyNotImplemented>()
+                .unwrap()
+                .is(&py.NotImplemented()));
+        })
+    }
+
+    #[test]
+    fn test_dict_is_not_notimplemented() {
+        Python::with_gil(|py| {
+            assert!(PyDict::new(py).downcast::<PyNotImplemented>().is_err());
+        })
+    }
+}