Deduction failure

[Dave Abrahams]

This program fails:

#include <boost/phoenix.hpp>
#include <boost/range/as_literal.hpp>

using namespace boost::phoenix::placeholders;
using namespace boost::phoenix;
    
int main()
{
    find(boost::as_literal("fox"), 'x')();                                           // works
    find(boost::as_literal("fox"), construct<char>(arg1))('x');        // works
    find(boost::as_literal("fox"), arg1)('x');                                    // compilation error
}

Took hours to work out what was going on. Nature of the beast, I suppose.