boost::qvm not usable in boost::spirit::x3

[octopus-prime]

If you try to parse
boost::qvm::vec<float, 3>
you fail with compiler errors:

error: conversion from 'boost::qvm::vec<float, 3>' to 'boost::spirit::x3::unused_type' is ambiguous

reason:

/usr/include/boost/qvm/vec.hpp:25:13: note: candidate function [with R = boost::spirit::x3::unused_type]

            operator R() const

            ^

/usr/include/boost/spirit/home/x3/support/unused.hpp:21:9: note: candidate constructor [with T = boost::qvm::vec<float, 3>]

        unused_type(T const&)

        ^

[zajo]

Can I get a complete short program that demonstrates the problem?

[octopus-prime]

#include <boost/qvm/vec.hpp>
#include <boost/spirit/home/x3.hpp>

namespace qvm = boost::qvm;
namespace x3 = boost::spirit::x3;

using scalar_t = float;

auto const scalar = x3::rule<struct scalar_, scalar_t>{"scalar"} =
x3::float_;

using vector_t = qvm::vec<scalar_t, 3>;

template <size_t N>
struct foo {
	template <typename C>
	void operator()(C const& ctx) const {
		x3::_val(ctx).a[N] = x3::_attr(ctx);
	}
};

auto const vector = x3::rule<struct vector_, vector_t>{"vector"} =
x3::lit('<') > scalar [foo<0>()] > x3::lit(',') > scalar [foo<1>()] > x3::lit(',') > scalar [foo<2>()] > x3::lit('>');

int main() {
    std::string input = "center = <0,0,0>";
    vector_t result;
    x3::phrase_parse(input.begin(), input.end(), x3::lit("center") > x3::lit('=') > vector > x3::eoi, x3::space, result);
    return 0;
}

Tip: use clang++ because of g++ 'internal compiler error'

[zajo]

Thanks. Please confirm that this fixes it: https://github.com/boostorg/qvm/tree/feature/issue_39.

[octopus-prime]

Works like a charm 👍