Don't print parens around list comprehensions

diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs
index 11b4df3..44d9b43 100644 (file)
--- a/compiler/hsSyn/HsExpr.lhs
+++ b/compiler/hsSyn/HsExpr.lhs
@@ -483,17 +483,19 @@ pprParendExpr expr
        -- I think that is usually (always?) right
     in
     case unLoc expr of
-      HsLit l          -> pp_as_was
-      HsOverLit l      -> pp_as_was
-      HsVar _          -> pp_as_was
-      HsIPVar _                -> pp_as_was
-      ExplicitList _ _  -> pp_as_was
-      ExplicitPArr _ _  -> pp_as_was
-      ExplicitTuple _ _        -> pp_as_was
-      HsPar _          -> pp_as_was
-      HsBracket _      -> pp_as_was
-      HsBracketOut _ []        -> pp_as_was
-      _                        -> parens pp_as_was
+      HsLit l             -> pp_as_was
+      HsOverLit l         -> pp_as_was
+      HsVar _             -> pp_as_was
+      HsIPVar _                   -> pp_as_was
+      ExplicitList _ _     -> pp_as_was
+      ExplicitPArr _ _     -> pp_as_was
+      ExplicitTuple _ _           -> pp_as_was
+      HsPar _             -> pp_as_was
+      HsBracket _         -> pp_as_was
+      HsBracketOut _ []           -> pp_as_was
+      HsDo sc _ _ _
+       | isListCompExpr sc -> pp_as_was
+      _                           -> parens pp_as_was
 
 isAtomicHsExpr :: HsExpr id -> Bool    -- A single token
 isAtomicHsExpr (HsVar {})     = True
@@ -936,7 +938,12 @@ data HsStmtContext id
 isDoExpr :: HsStmtContext id -> Bool
 isDoExpr DoExpr      = True
 isDoExpr (MDoExpr _) = True
-isDoExpr other       = False
+isDoExpr _           = False
+
+isListCompExpr :: HsStmtContext id -> Bool
+isListCompExpr ListComp = True
+isListCompExpr PArrComp = True
+isListCompExpr _        = False
 \end{code}
 
 \begin{code}