Struct::to_string broken for enumeration fields

[VeaaC]

If you have a struct containing an enum, e.g.:

namespace ttf {
enum RestrictionType : u8 {
    DUMMY,
}
struct A {
    restriction_type : RestrictionType;
}
}

Then the generated A::to_string does not compile:

error: no match for ‘operator+’:
     "    restriction_type : " << +restriction_type << "," << std::endl