weakref.WeakMethod equality behaves differently than weakref.ref (always False after garbage collection)

Bug report

Equality comparison of weakref.ref objects succeeds both before and after object deletion. Equality of two weakref.WeakMethod objects, however, is always false if the underlying object has been deleted:

>>> from weakref import WeakMethod, ref
>>> class T:
...   def x(self): ...
...
>>> t = T()
>>> r1 = ref(t)
>>> r2 = ref(t)
>>> m1 = WeakMethod(t.x)
>>> m2 = WeakMethod(t.x)
>>> r1 == r2
True
>>> m1 == m2
True
>>> del t
>>> r1 == r2
True
>>> m1 == m2
False

Is this a bug? or perhaps desirable behavior or a fundamental limitation of bound method weak references?

Your environment

• Python 3.11.0 | packaged by conda-forge | (main, Jan 15 2023, 05:44:48) [Clang 14.0.6 ] on darwin
• macos x86_64, v12.6.1 (21G217)

首先运行提供的 Python REPL 示例，并比较垃圾回收前后 weakref.ref 与 weakref.WeakMethod 的行为。然后检查 WeakMethod 和 ref 的实现，以及它们与相等性相关的测试（如果存在）。确认删除后的预期相等性语义，并在确认该行为是 bug 的情况下添加覆盖测试或进行针对性修复，即视为完成。