I'm working on a project in the D language and I want to use a module from the standard library called std.sumtype. I'm on debian oldstable, and I've tried both GDC and LDC. DMD is unavailable, because I'm using a machine with an armhf architecture. Neither of these compilers can find std.sumtype, despite it being in the standard library. I also tried downloading 3 different versions of sumtype.d from the phobos repositories of all three D compilers. Each of these would not compile. How can I use this? Am I on the wrong version?