:set +c
:l T16575.hs
:all-types

-- data X = A | B
--     deriving (Show)
--               ^^^^
:type-at T16575.hs 4 15 4 19
-- wrongly outputs:
--  :: [X] -> ShowS

-- instance Eq X where
--          ^^^^
:type-at T16575.hs 6 10 6 14
-- wrongly outputs:
-- :: X -> X -> Bool

-- also note how :all-types is inconsistent with :type-at