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Load the following code into GHCi using 8.8 or later:

{-# LANGUAGE GADTs #-}
module Bug where

data T where
  MkT :: (Int -> Int) -> T

And then try :info T:

λ> :info T
data T where
  MkT :: Int -> Int -> T
        -- Defined at Bug.hs:4:1

Eek! Those parentheses around Int -> Int are required, but aren't showing up here.

This is my fault, as I accidentally introduced this regression in commit 9d9e3557. When pretty-printing fields in a GADT type signature, I should have been using funPrec, not topPrec, since the fields are interspersed with arrows. Unfortunately, no regression tests existed to catch my mistake.

Patch incoming.