It's easy to specify a compiler to use when building with dub (dub build --compiler=...) but is it possible for the creator of a dub package to specify a preferred priority order of available compilers? So, for example, if I specify a priority list of,

1. gdc >= 4.8
2. ldc >= 0.12.0
3. dmd >= 2.063

Then dub will first look to see if an appropriate GDC version is installed (and compile with it if it is); then LDC; and finally DMD if nothing else presents. This could be a way in which package creators can help to ensure builds of their software are adequate in terms of performance and available features. (I'm not sure if checking for compiler version is reliably possible but thought I'd throw it out there as a suggestion in case it is.)