Partial kind signatures and synonyms
ghci> :kind (Maybe :: _) <interactive>:1:11: error: • Found type wildcard ‘_’ standing for ‘* -> *’ To use the inferred type, enable PartialTypeSignatures • In the kind ‘_’ In the type ‘(Maybe :: _)’
This doesn't work:
ghci> type T = (Maybe :: _) <interactive>:2:20: error: Wildcard ‘_’ not allowed in the declaration for type synonym ‘T’
Maybe there's a deeper reason why, but I naively expect the second command to show the partial kind signature.