Pretty printing of types with HsDocTy goes wrong

Pretty printing of type signatures containing HsDocTy goes wrong in HEAD. This manifests itself as serious bugs in both Haddock and Hoogle. Because the bug causes Haddock generated documentation to be wrong, I've marked the severity as major.

Take the following file:

{-# LANGUAGE FlexibleInstances #-}

import GHC
import SrcLoc
import Outputable

main = do
	putStrLn $ out $ HsFunTy fun fun
	putStrLn $ out $ HsFunTy (doc fun) fun

reL = L undefined
out x = showSDoc $ ppr x
fun = reL $ HsFunTy (reL $ HsTyVar "a") (reL $ HsTyVar "b") 
doc = reL . flip HsDocTy undefined

instance OutputableBndr [Char] where
	pprBndr _ x = text x

The output is:

C:\Neil>runghc "-package ghc" test2.hs
([a] -> [b]) -> [a] -> [b]
[a] -> [b] <document comment> -> [a] -> [b]

Note that the first line (correctly) brackets the type signature, but that the second (incorrectly) omits the brackets. I suggest a change to the pretty printer to ignore HsTyDoc when determining where to insert brackets - or even removing the pretty printing of HsTyDoc entirely.

-- Neil

Trac metadata

Trac field	Value
Version	6.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ganesh.sittampalam@credit-suisse.com, neil.mitchell.2@credit-suisse.com
Operating system	Unknown
Architecture	Unknown