trying to follow: http://ddili.org/ders/d.en/class.html
//--- OSX 10.9 DMD 2.065 module test; class Foo { int num; this(int num) { this.num = num; } Foo dup() const { return new Foo(this.num); } immutable(Foo) idup() const { return new immutable(Foo)(this.num); } } void main() { auto foo = new Foo(1); auto mfoo = foo.dup(); auto ifoo = foo.idup(); } * test.d(15): Error: mutable method test.Foo.this is not callable using a immutable object * test.d(15): Error: no constructor for Foo * Failed: ["dmd", "-v", "-o-", "test.d", "-I."] //--- What am i missing?