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Should we open a feature request at Haddock?

I think that would be a good idea. A cursory search suggests there's no feature request already

Done: https://github.com/haskell/haddock/issues/1625 I would also like to humbly suggest that the GHC devs consider my proof that pattern synonym completeness checks are decidable, thus improving the situation that caused this thread. I have a proof-of-concept implementation with a type signature like covers :: PatternMatch t => [Pattern t] -> Bool where  type Pattern t = t -> Bool  and PatternMatch is a type class much like Generic which derives instances for all Generic Rep types (except V1) plus function spaces and fixed points. What is left to do is to convert the GHC-internal pattern representation into (t -> Bool). Is that feasible? As I elaborated, that task ist quite mechanistic and could likely be done in Template Haskell. Olaf