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?
std.sumtype is a pretty new package that was added in 2.097.0: https://dlang.org/changelog/2.097.0.html#std-sumtype so the debian oldstable packages probably don't have it yet as you would need at least:
If you want to use the latest compiler you could always download the latest LDC archive and extract it somewhere and run it from there or use the install.sh script from the download page for portable and multiple simultaneous installs.
std.sumtype is an adoption of the dub package sumtype so if you are using dub, you can depend on that as well and not need to get another compiler outside the package manager.