However, the one part I am struggling with is implementing exporting of
pattern synonyms. The pipeline is pretty clear to get the pattern synonym
definitions to the ModGuts, but I get lost there. Since they are a
completely compile-time thing, there's nothing to put in the CgGuts (well,
I guess the wrapper (i.e. the patsyn-in-an-expression-context) should be
put there). However, when I look at existing stuff in ModIface/ModDetails,
I don't really see a pattern for storing actual definitions there.