Incorrect pretty-printing for warning categories
@barci2 helpfully pointed out some errors in the pretty-printing of warning categories that I introduced in !9684 (closed). For example, given this module:
module M {-# WARNING in "x-a" "b" #-} where
{-# WARNING in "x-c" e "d" #-}
e = e
the result of -ddump-parsed
is:
module M
{-# WARNING "b" #-}
where
{-# WARNING [x-c] e "d" #-}
e = e
whereas it should be:
module M
{-# WARNING in "x-a" "b" #-}
where
{-# WARNING in "x-c" e "d" #-}
e = e