import std.stdio;

import std.typecons;

​

class A {

    Nullable!string _str;

    Nullable!string str() { return this._str; }

    Nullable!string str(T)(T setter) { 

        return this._str = setter; 

    }

}

​

void main() {

    auto a = new A();

    a.str = "abc";

    writeln(a.str());

}

​