ffi: remove PyArena on 3.10 and up

CHANGELOG.md

@@ -37,6 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix case where `ValueError` without message could be raised by the `#[derive(FromPyObject)]` generated implementation for a tuple struct. [#2414](https://github.com/PyO3/pyo3/pull/2414)
 - Fix compile failure when using `#[pyo3(from_py_with = "pouf")]` in on a field in a `#[derive(FromPyObject)]` struct. [#2414](https://github.com/PyO3/pyo3/pull/2414)
 - Fix FFI definitions `_PyDateTime_BaseTime` lacking leading underscores in their names. [#2421](https://github.com/PyO3/pyo3/pull/2421)
+- Remove FFI definition `PyArena` on Python 3.10 and up. [#2421](https://github.com/PyO3/pyo3/pull/2421)
 
 ## [0.16.5] - 2022-05-15
 

pyo3-ffi/src/lib.rs

@@ -316,7 +316,7 @@ pub use self::moduleobject::*;
 pub use self::object::*;
 pub use self::objimpl::*;
 pub use self::osmodule::*;
-#[cfg(not(Py_LIMITED_API))]
+#[cfg(not(any(Py_LIMITED_API, Py_3_10)))]
 pub use self::pyarena::*;
 pub use self::pycapsule::*;
 pub use self::pyerrors::*;
@@ -399,7 +399,7 @@ mod osmodule;
 // skipped picklebufobject.h
 // skipped pyctype.h
 // skipped py_curses.h
-#[cfg(not(Py_LIMITED_API))]
+#[cfg(not(any(Py_LIMITED_API, Py_3_10)))]
 mod pyarena;
 mod pycapsule;
 // skipped pydecimal.h

src/marker.rs

@@ -184,7 +184,7 @@ mod negative_impls {
     impl !Ungil for crate::ffi::PyCodeObject {}
     #[cfg(not(Py_LIMITED_API))]
     impl !Ungil for crate::ffi::PyDictKeysObject {}
-    #[cfg(not(Py_LIMITED_API))]
+    #[cfg(not(any(Py_LIMITED_API, Py_3_10)))]
     impl !Ungil for crate::ffi::PyArena {}
 }