Change a test for UnboxedSums

The test is from mihaimaruseac#564.

TESTS.md

@@ -1643,7 +1643,7 @@ foo = undefined
 ```haskell
 {-# LANGUAGE UnboxedSums #-}
 
-f :: (# Int | Bool | String #)
+f :: (# (# Int, String #) | String #) -> (# Int | String #)
 ```
 
 #### Promoted types

src/HIndent/Pretty.hs

@@ -1019,8 +1019,11 @@ prettyHsType (HsAppTy _ l r) = spaced $ fmap pretty [l, r]
 prettyHsType (HsAppKindTy _ l r) = pretty l >> string " @" >> pretty r
 prettyHsType (HsFunTy _ _ a b) = (pretty a >> string " -> ") |=> pretty b
 prettyHsType (HsListTy _ xs) = brackets $ pretty xs
-prettyHsType (HsTupleTy _ _ []) = string "()"
-prettyHsType (HsTupleTy _ _ xs) = hvTuple' $ fmap pretty xs
+prettyHsType (HsTupleTy _ HsUnboxedTuple []) = string "(# #)"
+prettyHsType (HsTupleTy _ HsBoxedOrConstraintTuple []) = string "()"
+prettyHsType (HsTupleTy _ HsUnboxedTuple xs) = hUnboxedTuple $ fmap pretty xs
+prettyHsType (HsTupleTy _ HsBoxedOrConstraintTuple xs) =
+  hvTuple' $ fmap pretty xs
 prettyHsType (HsSumTy _ xs) = unboxedSums $ hBarSep $ fmap pretty xs
   -- For `HsOpTy`, we do not need a single quote for the infix operator. An
   -- explicit promotion is necessary if there is a data constructor and

src/HIndent/Pretty/Combinators/Lineup.hs

@@ -7,6 +7,7 @@ module HIndent.Pretty.Combinators.Lineup
   , vTuple
   , vTuple'
   , hPromotedTuple
+  , hUnboxedTuple
   , -- * Records
     hvFields
   , hFields
@@ -69,6 +70,10 @@ vTuple' = vLineup' ("(", ")")
 hPromotedTuple :: [Printer ()] -> Printer ()
 hPromotedTuple = promotedTupleParens . hCommaSep
 
+-- | RUns printers to construct an unboxed tuple in a line.
+hUnboxedTuple :: [Printer ()] -> Printer ()
+hUnboxedTuple = unboxedSums . hCommaSep
+
 -- | Applies 'hFields' if the result fits in a line or 'vFields' otherwise.
 hvFields :: [Printer ()] -> Printer ()
 hvFields = (<-|>) <$> hFields <*> vFields