Argument-less infix declarations printed without parentheses in -ddump-splices

Compile this:

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeOperators #-}
{-# OPTIONS_GHC -ddump-splices #-}
module Bug where

$([d| type (|||) = Either

      (&&&) :: Bool -> Bool -> Bool
      (&&&) = (&&)

      data (***)
    |])

And you'll get this:

$ /opt/ghc/8.4.3/bin/ghci Bug.hs
GHCi, version 8.4.3: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug              ( Bug.hs, interpreted )
Bug.hs:(6,3)-(12,6): Splicing declarations
    [d| (&&&_a1xt) :: Bool -> Bool -> Bool
        (&&&_a1xt) = (&&)
        
        type |||_a1xs = Either
        data ***_a1xr |]
  ======>
    type |||_a5bW = Either
    (&&&_a5bV) :: Bool -> Bool -> Bool
    (&&&_a5bV) = (&&)
    data ***_a5bX
Ok, one module loaded.

Notice the pretty-printed declarations of type |||_a5bW and data ***_a5bX, which are lacking some necessary parentheses.

Trac metadata

Trac field	Value
Version	8.4.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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