PEP 362 implementation issue: C callables

<div>
    <br><br>
    One wrinkle of PEP 362 in CPython is callables implemented directly
    in C.&nbsp; Right now there's no good way to generate such signatures
    automatically.&nbsp; That's why we kept __signature__ in the spec, to
    allow implementors to generate signatures by hand for these
    callables.<br><br>
    But the wrinkle gets wrinklier.&nbsp; The problem is, you often can't add
    arbitrary attributes to these objects:<br><blockquote>&gt;&gt;&gt; import os<br>
      &gt;&gt;&gt; os.stat.random_new_attribute = 3<br>
      Traceback (most recent call last):<br>
      &nbsp; File "&lt;stdin&gt;", line 1, in &lt;module&gt;<br>
      AttributeError: 'builtin_function_or_method' object has no
      attribute 'random_new_attribute'<br>
</blockquote>
    If users are to attach precomputed signatures to callables
    implemented in C, those callables may need to *already* have a
    __signature__ attribute.<br><br><br>
    I've already added __signature__ to PyCFunctionObject in the PEP 362
    patch.&nbsp; This takes care of the vast bulk of such callables.&nbsp; But
    there are a bunch of obscure callable objects in CPython, and I
    suspect some of them may need a __signature__ attribute.<br><br>
    Here's an almost- complete list, listed as their Python type:<br><blockquote>functools.KeyWrapper (result of functools.cmp_to_key)<br>
      weakref.weakref<br>
      method (bound method objects, aka "x = Class(); x.method")<br>
      instancemethod (is this still even used?&nbsp; it's never used in
      trunk)<br>
      operator.itemgetter<br>
      operator.attrgetter<br>
      operator.methodcaller<br>
      _json.Scanner (result of _json.make_scanner)<br>
      _json.Encoder (result of _json.make_encoder)<br>
      _ctypes.DictRemover (I'm not even sure how you can get your hands
      on one of these)<br>
      sqlite3.Connection<br>
</blockquote>
    I produced this by grepping for "/* tp_call */" and ignoring all of
    them that were set to "0", then creating one of those objects and
    trying (and failing) to set a __signature__ attribute.<br><br>
    There are four more candidates I found with the grep but couldn't
    figure out how to instantiate and test.&nbsp; They have to do with the
    descriptor protocol, aka properties, but the types aren't directly
    exposed by Python.&nbsp; They're all defined in Object/descrobject.c.&nbsp;
    The internal class names are:<br><blockquote>
      method_descriptor<br>
      classmethod_descriptor<br>
      wrapper_descriptor<br>
      method-wrapper (you get one of these out of a
      "wrapper_descriptor")<br>
</blockquote>
    <br>
    I'm happy to do the work, but I don't have a good sense of which
    callables need a __signature__ attribute.&nbsp; Can someone here tell me
    which ones might need a __signature__ attribute?<br><br><br>/arry<br>
</div>