Remove get_refcnt from public api

This is an attempt to fix PyO3#3357.
The function is used relatively frequently in tests,
so have left it with #[cfg(test)] and pub(crate).
This avoids coating the tests with `unsafe`,
and something that doesn't indicate intent as well.

TODO:
[ ] Fix docs that refer to `get_refcnt` as an example -
    is there another function I can use instead?

src/gil.rs

@@ -521,7 +521,6 @@ mod tests {
     #[allow(deprecated)]
     use super::GILPool;
     use super::{gil_is_acquired, GIL_COUNT, OWNED_OBJECTS, POOL};
-    use crate::types::any::PyAnyMethods;
     use crate::{ffi, gil, PyObject, Python};
     #[cfg(not(target_arch = "wasm32"))]
     use parking_lot::{const_mutex, Condvar, Mutex};

src/instance.rs

@@ -202,6 +202,14 @@ impl<'py> Bound<'py, PyAny> {
     ) -> &'a Option<Self> {
         &*(ptr as *const *mut ffi::PyObject).cast::<Option<Bound<'py, PyAny>>>()
     }
+
+    /// Returns the reference count for the Python object.
+    ///
+    /// Only used to validate behaviour in tests.
+    #[cfg(test)]
+    pub(crate) fn get_refcnt(&self) -> isize {
+        unsafe { ffi::Py_REFCNT(self.as_ptr()) }
+    }
 }
 
 impl<'py, T> Bound<'py, T>
@@ -1288,8 +1296,7 @@ impl<T> Py<T> {
     }
 
     /// Gets the reference count of the `ffi::PyObject` pointer.
-    #[inline]
-    pub fn get_refcnt(&self, _py: Python<'_>) -> isize {
+    pub(crate) fn get_refcnt(&self, _py: Python<'_>) -> isize {
         unsafe { ffi::Py_REFCNT(self.0.as_ptr()) }
     }
 

src/types/any.rs

@@ -810,7 +810,10 @@ impl PyAny {
     }
 
     /// Returns the reference count for the Python object.
-    pub fn get_refcnt(&self) -> isize {
+    ///
+    /// Only used to validate behaviour in tests.
+    #[cfg(test)]
+    pub(crate) fn get_refcnt(&self) -> isize {
         self.as_borrowed().get_refcnt()
     }
 
@@ -1648,9 +1651,6 @@ pub trait PyAnyMethods<'py>: crate::sealed::Sealed {
     where
         T: FromPyObjectBound<'a, 'py>;
 
-    /// Returns the reference count for the Python object.
-    fn get_refcnt(&self) -> isize;
-
     /// Computes the "repr" representation of self.
     ///
     /// This is equivalent to the Python expression `repr(self)`.
@@ -2188,10 +2188,6 @@ impl<'py> PyAnyMethods<'py> for Bound<'py, PyAny> {
         FromPyObjectBound::from_py_object_bound(self.as_borrowed())
     }
 
-    fn get_refcnt(&self) -> isize {
-        unsafe { ffi::Py_REFCNT(self.as_ptr()) }
-    }
-
     fn repr(&self) -> PyResult<Bound<'py, PyString>> {
         unsafe {
             ffi::PyObject_Repr(self.as_ptr())

tests/test_inheritance.rs

@@ -242,16 +242,16 @@ mod inheriting_native_type {
     fn inherit_dict_drop() {
         Python::with_gil(|py| {
             let dict_sub = pyo3::Py::new(py, DictWithName::new()).unwrap();
-            assert_eq!(dict_sub.get_refcnt(py), 1);
+            assert_eq!(unsafe { pyo3::ffi::Py_REFCNT(dict_sub.as_ptr()) }, 1);
 
             let item = &py.eval_bound("object()", None, None).unwrap();
-            assert_eq!(item.get_refcnt(), 1);
+            assert_eq!(unsafe { pyo3::ffi::Py_REFCNT(item.as_ptr()) }, 1);
 
             dict_sub.bind(py).set_item("foo", item).unwrap();
-            assert_eq!(item.get_refcnt(), 2);
+            assert_eq!(unsafe { pyo3::ffi::Py_REFCNT(item.as_ptr()) }, 2);
 
             drop(dict_sub);
-            assert_eq!(item.get_refcnt(), 1);
+            assert_eq!(unsafe { pyo3::ffi::Py_REFCNT(item.as_ptr()) }, 1);
         })
     }