Remove BangPatterns if possible

See #4

2 files changed, 15 insertions, 4 deletions

diff --git a/src/StylishHaskell/Stylish/LanguagePragmas.hs b/src/StylishHaskell/Stylish/LanguagePragmas.hs
index 60e3187..017c64d 100644
--- a/src/StylishHaskell/Stylish/LanguagePragmas.hs
+++ b/src/StylishHaskell/Stylish/LanguagePragmas.hs
@@ -77,6 +77,7 @@ addLanguagePragma pragma modu
 -- but we do a best effort.
 isRedundant :: H.Module H.SrcSpanInfo -> String -> Bool
 isRedundant m "ViewPatterns" = isRedundantViewPatterns m
+isRedundant m "BangPatterns" = isRedundantBangPatterns m
 isRedundant _ _              = False
 
 
@@ -85,3 +86,10 @@ isRedundant _ _              = False
 isRedundantViewPatterns :: H.Module H.SrcSpanInfo -> Bool
 isRedundantViewPatterns m = null
     [() | H.PViewPat _ _ _ <- everything m :: [H.Pat H.SrcSpanInfo]]
+
+
+--------------------------------------------------------------------------------
+-- | Check if the BangPatterns language pragma is redundant.
+isRedundantBangPatterns :: H.Module H.SrcSpanInfo -> Bool
+isRedundantBangPatterns m = null
+    [() | H.PBangPat _ _ <- everything m :: [H.Pat H.SrcSpanInfo]]
diff --git a/tests/StylishHaskell/Stylish/LanguagePragmas/Tests.hs b/tests/StylishHaskell/Stylish/LanguagePragmas/Tests.hs
index c802f62..74181ee 100644
--- a/tests/StylishHaskell/Stylish/LanguagePragmas/Tests.hs
+++ b/tests/StylishHaskell/Stylish/LanguagePragmas/Tests.hs
@@ -48,7 +48,8 @@ case02 :: Test
 case02 = testCase "case 02" $ expected @=? testStylish (stylish True) input
   where
     input = unlines
-        [ "{-# LANGUAGE ViewPatterns #-}"
+        [ "{-# LANGUAGE BangPatterns #-}"
+        , "{-# LANGUAGE ViewPatterns #-}"
         , "increment ((+ 1) -> x) = x"
         ]
 
@@ -63,10 +64,12 @@ case03 :: Test
 case03 = testCase "case 03" $ expected @=? testStylish (stylish True) input
   where
     input = unlines
-        [ "{-# LANGUAGE ViewPatterns #-}"
-        , "increment x = x + 1"
+        [ "{-# LANGUAGE BangPatterns #-}"
+        , "{-# LANGUAGE ViewPatterns #-}"
+        , "increment x = case x of !_ -> x + 1"
         ]
 
     expected = unlines
-        [ "increment x = x + 1"
+        [ "{-# LANGUAGE BangPatterns #-}"
+        , "increment x = case x of !_ -> x + 1"
         ]