Unary Operators Compilation Failure

[Suudy]

I'm getting a compilation error when using a unary operator. Here's some sample code that exhibits the problem.

This is on Lubuntu 15.04 with gcc 4.9.2. Also on Kubuntu 14.04 with gcc 4.8.4.

#include <pybind11/pybind11.h>
#include <pybind11/operators.h>

namespace py = pybind11;

class foo
{
  public:
    foo(int f_) : m_f(f_)
    {
    }

    foo operator~() const
    {
      return foo(~m_f);
    }

  private:
    int m_f;
};

PYBIND11_PLUGIN(foo)
{
  py::module m("foom", "foom example");

  py::class_<foo>(m, "foo")
    .def(py::init<int>())

    .def(~py::self);

  return m.ptr();
}

I get the following errors:

In file included from test.cpp:2:0:
./pybind11/operators.h: In instantiation of ‘struct pybind11::detail::op_impl<(pybind11::detail::op_id)15, (pybind11::detail::op_type)2, foo, foo, pybind11::detail::undefined_t>’:
./pybind11/operators.h:52:29: required from ‘void pybind11::detail::op_<id, ot, L, R>::execute(pybind11::class_<Base, Holder>&, Extra&& ...) const [with Base = foo; Holder = std::unique_ptr<foo, std::default_delete >; Extra = {}; pybind11::detail::op_id id = (pybind11::detail::op_id)15; pybind11::detail::op_type ot = (pybind11::detail::op_type)2; L = pybind11::detail::self_t; R = pybind11::detail::undefined_t]’
./pybind11/pybind11.h:703:9: required from ‘pybind11::class_<type, holder_type>& pybind11::class_<type, holder_type>::def(const pybind11::detail::op_<id, ot, L, R>&, Extra&& ...) [with pybind11::detail::op_id id = (pybind11::detail::op_id)15; pybind11::detail::op_type ot = (pybind11::detail::op_type)2; L = pybind11::detail::self_t; R = pybind11::detail::undefined_t; Extra = {}; type = foo; holder_type = std::unique_ptr<foo, std::default_delete >]’
test.cpp:29:19: required from here
./pybind11/operators.h:96:17: error: ‘l’ was not declared in this scope
static auto execute(const L &l) -> decltype(expr) { return expr; }
^
./pybind11/operators.h:137:1: note: in expansion of macro ‘PYBIND11_UNARY_OPERATOR’
PYBIND11_UNARY_OPERATOR(invert, operator~, ~l)
^
./pybind11/operators.h: In instantiation of ‘void pybind11::detail::op_<id, ot, L, R>::execute(pybind11::class_<Base, Holder>&, Extra&& ...) const [with Base = foo; Holder = std::unique_ptr<foo, std::default_delete >; Extra = {}; pybind11::detail::op_id id = (pybind11::detail::op_id)15; pybind11::detail::op_type ot = (pybind11::detail::op_type)2; L = pybind11::detail::self_t; R = pybind11::detail::undefined_t]’:
./pybind11/pybind11.h:703:9: required from ‘pybind11::class_<type, holder_type>& pybind11::class_<type, holder_type>::def(const pybind11::detail::op_<id, ot, L, R>&, Extra&& ...) [with pybind11::detail::op_id id = (pybind11::detail::op_id)15; pybind11::detail::op_type ot = (pybind11::detail::op_type)2; L = pybind11::detail::self_t; R = pybind11::detail::undefined_t; Extra = {}; type = foo; holder_type = std::unique_ptr<foo, std::default_delete >]’
test.cpp:29:19: required from here
./pybind11/operators.h:52:32: error: ‘execute’ is not a member of ‘op {aka pybind11::detail::op_impl<(pybind11::detail::op_id)15, (pybind11::detail::op_type)2, foo, foo, pybind11::detail::undefined_t>}’
class_.def(op::name(), &op::execute, std::forward(extra)...);
^

[Suudy]

I also tested it on Lubuntu 15.10 with gcc 5.2.1. Same error message.

[wjakob]

I pushed a fix -- can you please verify that it works now?

[Suudy]

That did fix it. Strange though. Looking at the preprocessed output before and after, they are essentially the same. I'm not sure if it is complaining about the decltype(~l) or the 'return ~l;'. It seems to me to be unambiguous in either case.

[Suudy]

And I just tested the build with Visual Studio 2015 and it does compile cleanly there (with the fa1bfb2 commit).

[wjakob]

Ok, good. I'm closing the ticket.