GHC HEAD regression: -ddump-splices incorrectly parenthesizes HsKindSig applications
When you compile this file with GHC 8.6.3 and HEAD:
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -ddump-splices #-}
module Bug where
import Data.Kind
type F = $([t| (Maybe :: Type -> Type) Int |])You get two different results:
$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
Bug.hs:8:12-45: Splicing type
[t| (Maybe :: Type -> Type) Int |]
======>
(Maybe :: Type -> Type) Int
$ ~/Software/ghc4/inplace/bin/ghc-stage2 -fforce-recomp Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
Bug.hs:8:12-45: Splicing type
[t| (Maybe :: Type -> Type) Int |]
======>
Maybe :: Type -> Type IntNotice how in the GHC HEAD output, GHC forgets to put parentheses around Maybe :: Type -> Type, leading to the utterly nonsensical type Maybe :: Type -> Type Int.
The commit that introduced this regression is bace26aadaafa4064e78f9ed088c1e2217221acc.
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