checks for copy ctor using __parameters

hasNonTrivialCopyConstructor.d

template hasNonTrivialCopyConstructor(T) {
    bool isCopyConstructorFor(alias ctor, T)() {
        // Specialized function that checks specifically for "ref" in a string
        bool containsRef(string str) {
            foreach (i, c; str) {
                if (c == 'r') {
                    if (i + 2 < str.length) {
                        return str[i + 1] == 'e' && str[i + 2] == 'f';
                    }
                }
            }
            return false;
        }
        static if (is(typeof(ctor) Params == __parameters) && Params.length >= 1) {
            // Check that Params 0 is correct type for a copy constructro
            enum isCorrectType = is(Params[0] == T);

            // If more than one parameter, check that they are all defaulted
            static if (Params.length >= 1) {
                bool hasCorrectDefaults() {
                    bool result = true;
                    static foreach (I; 1 .. Params.length) {{
                        auto getDefault(Params[I..I+1] args) { return args[0]; }
                        result &= is(typeof(getDefault()));
                    }}
                    return result;
                } 
            } else {
                enum hasCorrectDefaults = true;
            }

            return isCorrectType
                && containsRef(Params[0..1].stringof)
                && hasCorrectDefaults;
        } else {
            return false;
        }
    }

    bool impl() {
        static if (__traits(hasMember, T, "__ctor")) {
            foreach (f; __traits(getOverloads, T, "__ctor")) {
                auto yes = isCopyConstructorFor!(f, T);
                if (yes) {
                    return yes;
                }
            }
        }
        return false;
    }

    enum hasNonTrivialCopyConstructor = impl;
}