Hi all,

While there is a way to expand type synonyms in type errors (-fprint-expanded-synonyms), as far as I know, the same doesn't exist for type families. For example, the following

type family Foo a where Foo Int = String
type family Bar a :: Maybe (Foo Int) where Bar a = '()

results in the error


I'd be interested in trying my hand at implementing a way to see this, either by adding it to -fprint-expanded-synonyms, or as a new flag.

Three questions:
 - Is there already a way to do this that I'm missing?
 - Are there reasons for why this would be a bad idea?
 - Would a proposal be necessary for this?

Thanks,
Jakob