Adding parens into generically generated codewip/T3384

And some other bits

3 files changed, 14 insertions, 5 deletions

diff --git a/compiler/hsSyn/HsDecls.hs b/compiler/hsSyn/HsDecls.hs
index 840106c47c..252d6c2b62 100644
--- a/compiler/hsSyn/HsDecls.hs
+++ b/compiler/hsSyn/HsDecls.hs
@@ -1068,7 +1068,14 @@ instance (OutputableBndrId name) => Outputable (HsDerivingClause name) where
                         , deriv_clause_tys      = L _ dct })
     = hsep [ text "deriving"
            , ppDerivStrategy dcs
-           , parens (interpp'SP dct) ]
+           , pp_dct dct ]
+      where
+        -- This complexity is to distinguish between
+        --    deriving Show
+        --    deriving (Show)
+        pp_dct [a@(HsIB _ (L _ HsAppsTy{}))] = parens (ppr a)
+        pp_dct [a] = ppr a
+        pp_dct _   = parens (interpp'SP dct)
 
 data NewOrData
   = NewType                     -- ^ @newtype Blah ...@
diff --git a/compiler/hsSyn/HsPat.hs b/compiler/hsSyn/HsPat.hs
index ec5578f36d..0042f51d44 100644
--- a/compiler/hsSyn/HsPat.hs
+++ b/compiler/hsSyn/HsPat.hs
@@ -670,9 +670,9 @@ hsPatNeedsParens (LitPat {})         = False
 hsPatNeedsParens (NPat {})           = False
 
 conPatNeedsParens :: HsConDetails a b -> Bool
-conPatNeedsParens (PrefixCon args) = not (null args)
-conPatNeedsParens (InfixCon {})    = True
-conPatNeedsParens (RecCon {})      = True
+conPatNeedsParens (PrefixCon {}) = False
+conPatNeedsParens (InfixCon {})  = True
+conPatNeedsParens (RecCon {})    = False
 
 {-
 % Collect all EvVars from all constructor patterns
diff --git a/compiler/hsSyn/HsUtils.hs b/compiler/hsSyn/HsUtils.hs
index de7736004d..8f52ea0c15 100644
--- a/compiler/hsSyn/HsUtils.hs
+++ b/compiler/hsSyn/HsUtils.hs
@@ -49,7 +49,7 @@ module HsUtils(
   -- Patterns
   mkNPat, mkNPlusKPat, nlVarPat, nlLitPat, nlConVarPat, nlConVarPatName, nlConPat,
   nlConPatName, nlInfixConPat, nlNullaryConPat, nlWildConPat, nlWildPat,
-  nlWildPatName, nlWildPatId, nlTuplePat, mkParPat,
+  nlWildPatName, nlWildPatId, nlTuplePat, mkParPat, nlParPat,
   mkBigLHsVarTup, mkBigLHsTup, mkBigLHsVarPatTup, mkBigLHsPatTup,
 
   -- Types
@@ -206,6 +206,8 @@ mkParPat :: LPat name -> LPat name
 mkParPat lp@(L loc p) | hsPatNeedsParens p = L loc (ParPat lp)
                       | otherwise          = lp
 
+nlParPat :: LPat name -> LPat name
+nlParPat p = noLoc (ParPat p)
 
 -------------------------------
 -- These are the bits of syntax that contain rebindable names