Parsing list of variants with boost spirit X3 - c++

Question

I try to parse a simple list of float or int into a vector of variant. I'm using boost 1.64 on Windows (mingw 64bit).
Here is a minimal example:
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/adapted/struct.hpp>
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <vector>
namespace x3 = boost::spirit::x3;
struct var : x3::variant<int, float> {
using base_type::base_type;
using base_type::operator=;
};
struct block {
bool dummy; // needed to make newer boost version compile
std::vector<var> vars;
};
BOOST_FUSION_ADAPT_STRUCT(block,
(bool, dummy),
(std::vector<var>, vars)
);
x3::rule<class var, var> const r_var = "var";
x3::rule<class block, block> const r_block = "block";
auto const r_var_def = x3::float_ | x3::int_;
auto const r_block_def = x3::attr(true) >> *x3::lit(";") >> *(r_var >> -x3::lit(","));
BOOST_SPIRIT_DEFINE(r_var, r_block);
bool parse(std::string const &txt, block &ast)
{
using boost::spirit::x3::phrase_parse;
using boost::spirit::x3::space;
auto iter = txt.begin();
auto end = txt.end();
const bool parsed = phrase_parse(iter, end, r_block, space, ast);
return parsed && iter == end;
}
int main() {
std::vector<std::string> list = {
"1, 3, 5.5",
";1.0, 2.0, 3.0, 4.0"
};
for (const auto&i : list) {
block ast;
if (parse(i, ast)) {
std::cout << "OK: " << i << std::endl;
} else {
std::cout << "FAIL: " << i << std::endl;
}
}
}
GCC 7.1 gives the following error:
..\parser\parser.cpp:41:68: required from here
..\..\win64\include/boost/spirit/home/x3/nonterminal/detai/rule.hpp:313:24: error: use of deleted function 'var::var(const var&)'
value_type made_attr = make_attribute::call(attr);
^~~~~~~~~
Any ideas, why GCC doesn't compile it? It works with Clang though.
Live on Coliru (switch to clang++ to see it work).

Answer 1

It seems that there is a problem using the inherited special members. Two workarounds:
using var = x3::variant<int, float>;
Alternatively:
struct var : x3::variant<int, float> {
var ( ) = default;
var (var const&) = default;
var& operator= (var const&) = default;
using base_type::base_type;
using base_type::operator=;
};