bitwise complement missing after enum rewrite?

[loriab]

Issue description

Once upon a time, adding py::arithmetic() to an enum class defined the bitwise complement operator (aka ~, aka __invert__). It looks like that went away in #1511. Was this intentional or a regression? If the former, please just close. I included a code snippet that reactivates the operator downstream, in case others run across the problem.

Reproducible example code

If one adds an invert line (~m.Flags.Write) to the test_enum.py test case (to an enum with arithmetic enabled, it throws an error

========================================================= FAILURES ==========================================================
___________________________________________________ test_binary_operators ___________________________________________________

    def test_binary_operators():
        assert int(m.Flags.Read) == 4
        assert int(m.Flags.Write) == 2
        assert int(m.Flags.Execute) == 1
        assert int(m.Flags.Read | m.Flags.Write | m.Flags.Execute) == 7
        assert int(m.Flags.Read | m.Flags.Write) == 6
        assert int(m.Flags.Read | m.Flags.Execute) == 5
        assert int(m.Flags.Write | m.Flags.Execute) == 3
        assert int(m.Flags.Write | 1) == 3
>       ~m.Flags.Write
E       TypeError: bad operand type for unary ~: 'pybind11_tests.enums.Flags'

test_enum.py:143: TypeError

User code solution

In case anyone needs this capability, this is a fix for your own code. (The def must be after the export_values.)

    py::enum_<efp_term>(m, "efp_term", py::arithmetic(), "Flags to specify EFP energy terms")
        .value("EFP_TERM_ELEC", EFP_TERM_ELEC, "EFP/EFP electrostatics.")
        .value("EFP_TERM_POL", EFP_TERM_POL, "EFP/EFP polarization.")
     ...
        .export_values()
        .def("__invert__", [](efp_term& value) { return ~value; });

[wjakob]

Hi @loriab,

this is a regression. Would you be willing to create PR that adds the __invert__ operator to the enum_base class.

Best,
Wenzel