Cannot patch __call__ on an object with vectorcall defined

It appears that when the type of an object has JAX_TPFLAGS_HAVE_VECTORCALL set on tp_flags, then overrides to call from within python are ignored.

• PyObject_Call checks if vectorcall is available (which is only a property of the type), and if so, then does the vectorcall: https://github.com/python/cpython/blob/3.11/Objects/call.c#L328
• The implementation of vectorcall does not check for tp_call (is this where call ends up?) https://github.com/python/cpython/blob/3.11/Include/internal/pycore_call.h#L39

I encountered this bug when using the latest version of JAX, which introduced vectorcalls in https://github.com/tensorflow/tensorflow/commit/bf3eb110f49fe9628a31d8e2052951cd6d0082f0 :

import jax
g = jax.jit(lambda x: x + 1)
print(type(g))
# > <class 'google3.third_party.tensorflow.compiler.xla.python.xla_extension.CompiledFunction'>
print(g(5))
# > 6
type(g).__call__ = lambda *args: 0
print(g(5))
# > 6

まず JAX の例を再現し、次に Objects/call.c の PyObject_Call における vectorcall チェック周辺と、Include/internal/pycore_call.h の vectorcall ディスパッチ周辺を読みます。Python レベルの call オーバーライドとの想定される相互作用を確認し、意図した動作を示すリグレッションカバレッジを追加します。