:type-at and :all-types show types for non-expressions in deriving and instances

Summary

:all-types :type-at show types for X in data ... deriving (X) and instance X where .... They al

Steps to reproduce

Save this file:

module Ghost where

data X = A | B
    deriving (Show)

instance Eq X where
    A == A = True
    B == B = True
    _ == _ = False

And in GHCi:

ghci> :set +c
ghci> :l ghost.hs
[1 of 1] Compiling Ghost            ( ghost.hs, interpreted ) [flags changed]
Ok, one module loaded.
Collecting type info for 1 module(s) ... 
ghci> :all-types
ghost.hs:(4,15)-(4,19): GHC.Types.Int -> Ghost.X -> GHC.Show.ShowS
ghost.hs:(7,7)-(7,9): Ghost.X -> Ghost.X -> GHC.Types.Bool
ghost.hs:(4,15)-(4,19): GHC.Show.Show Ghost.X
ghost.hs:(4,15)-(4,19): ([Ghost.X] -> GHC.Show.ShowS) -> GHC.Show.Show Ghost.X
... (many more lines for the same range (4,15)-(4,19))
ghost.hs:(6,10)-(6,14): GHC.Classes.Eq Ghost.X
ghost.hs:(6,10)-(6,14): (Ghost.X -> Ghost.X -> GHC.Types.Bool) -> GHC.Classes.Eq Ghost.X
... (many more lines for the same range (6,10)-(6,14))
ghost.hs:(7,14)-(7,18): GHC.Types.Bool
ghost.hs:(8,14)-(8,18): GHC.Types.Bool
... (many other 'correct' types)

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

-- instance Eq X where
--          ^^^^
ghci> :type-at ghost.hs 6 10 6 14
 :: X -> X -> Bool

Expected behavior

Show in deriving (Show) and Eq X in instance Eq X where should not show up in :all-types and should not be accepted by :type-at.

Environment

• GHC version used: 8.6.4

Optional:

• Operating System: Linux
• System Architecture: x86-64