Fix docstrings of enum methods

[YannickJadoul]

#1511 broke the docstrings of the __repr__, __add__, etc. methods of enum_ types. E.g., the docstring of a __repr__ now looks like this:

>>> example.AnEnum.__repr__.__doc__
'(self: handle) -> str\n'

This PR fixes that by passing the name to the cpp_function constructors, in the same was as class_::def would do:

>>> example.AnEnum.__repr__.__doc__
'__repr__(self: handle) -> str\n'

I also converted __setstate__ and __getstate__ to pickle, to get rid of the warnings about old- vs. new-style constructors.

[wjakob]

All the changes look good for me, except the changes regarding hash and getstate. I remember at the time intentionally getting rid of pickle() to avoid unneeded code, which you now added back. Can we stick with how it was previously?

[YannickJadoul]

The reason I did this is that by adding the name to the original __setstate__, it would start complaining about "using an old-style placement-new 'setstate' which has been deprecated", and I thought the one function wouldn't matter and even avoid a second call from C++ -> Python -> C++ by calling __int__ is called in __getstate__.

But this latest commit should fix it.

One minor concern is that the docstrings still show int_ instead of int, but if I can easily fix that, I'll open a new PR.

[wjakob]

LGTM, thanks!

[wjakob]

FYI: I removed the use of std::move in __setstate__, that seemed a bit overkill for an enum.

[YannickJadoul]

FYI: I removed the use of std::move in __setstate__, that seemed a bit overkill for an enum.

Oh right, it's just a primitive underlying type, anyway. That was just a remainder of copy-pasting the __setstate__ implemenation, I suppose.