Fix negative literals in patterns (fixes #49)

src-literatetests/tests.blt

@@ -1017,6 +1017,15 @@ func = do
         | otherwise -> max (defLen - 0.05) (defLen * 0.95) -- TODO
   return True
 
+#test issue 49
+
+foo n = case n of
+  1  -> True
+  -1 -> False
+
+bar n = case n of
+  (-2, -2) -> (-2, -2)
+
 
 ###############################################################################
 ###############################################################################

src/Language/Haskell/Brittany/Internal/Layouters/Pattern.hs

@@ -131,8 +131,12 @@ layoutPat lpat@(L _ pat) = docWrapNode lpat $ case pat of
     wrapPatPrepend pat1 (docLit $ Text.pack "!")
   LazyPat pat1 -> do
     wrapPatPrepend pat1 (docLit $ Text.pack "~")
-  NPat llit@(L _ (OverLit olit _ _ _)) _ _ _ -> do
+  NPat llit@(L _ (OverLit olit _ _ _)) mNegative _ _ -> do
-    fmap Seq.singleton $ docWrapNode llit $ allocateNode $ overLitValBriDoc olit
+    litDoc <- docWrapNode llit $ allocateNode $ overLitValBriDoc olit
+    negDoc <- docLit $ Text.pack "-"
+    pure $ case mNegative of
+      Just{}  -> Seq.fromList [negDoc, litDoc]
+      Nothing -> Seq.singleton litDoc
 
 -- if MIN_VERSION_ghc(8,0,0)
 --   VarPat n -> return $ stringLayouter lpat $ lrdrNameToText n