Pretty much what the title says. I tried installing bc and it downloaded ghc, among other things. I was curious how this came to be, so I ran
guix graph --type=derivation bc | grep -- '-ghc'
(the dash being there to exclude accidental matches of "ghc" showing up in hashes). My understanding is that --type=derivation is the most exhaustive version, yet I didn't see any matches.
ghc-related derivations are listed among the ones to be built, but according to guix graph bc shouldn't be depending on those derivations.
bcinstalloutput