GHC 8.4.1 regression: rank-n types no longer parenthesized when pretty-printed
Take this file:
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -ddump-splices #-}
module Bug where
import Language.Haskell.TH
$([d| f :: (forall a. a) -> Int
f _ = undefined |])In GHC 8.2.2, -ddump-splices behaves as you'd expect:
$ /opt/ghc/8.2.2/bin/ghci Bug.hs
GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Bug.hs:(8,3)-(9,24): Splicing declarations
[d| f_a1zL :: (forall a_a1zM. a_a1zM) -> Int
f_a1zL _ = undefined |]
======>
f_a49Z :: (forall a_a4a0. a_a4a0) -> Int
f_a49Z _ = undefined
Ok, one module loaded.But in GHC 8.4.1-alpha (and HEAD), the GHC pretty-printer incorrectly leaves off the parentheses around the type (forall a. a):
$ /opt/ghc/8.4.1/bin/ghci Bug.hs
GHCi, version 8.4.0.20171222: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Bug.hs:(8,3)-(9,24): Splicing declarations
[d| f_a1EF :: (forall a_a1EG. a_a1EG) -> Int
f_a1EF _ = undefined |]
======>
f_a4ap :: forall a_a4aq. a_a4aq -> Int
f_a4ap _ = undefined
Ok, one module loaded.Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.4.1-alpha1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | high |
| Resolution | Unresolved |
| Component | GHC API |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | alanz |
| Operating system | |
| Architecture |