Ah, but most of the complexity in that line is an artifact of how Haddock (egregiously badly) generates documentation. The line in the source code is inst

Ah, but most of the complexity in that line is an artifact of how Haddock (egregiously badly) generates documentation. The line in the source code is instance (Patchy p, ApplyState p ~ Tree) => Patchy (PatchInfoAnd rt p) I don't personally like typeclassitis, but this is actually easy to interpret: "If 'p' is a patch-like thing, and its ApplyState is a Tree, then 'PatchInfoAnd rt p' is a patch-like thing"