Allow case-of Blockargument operand with par-spacing

data/15-regressions.blt

@@ -1108,3 +1108,8 @@ func = do
     some long function invocation (plus a paren + ed operator expression)
       `shouldReturn` all ((==) True)
       :: IO ()
+
+#test allow operator plus paragraph case-of BlockArgument
+func arg = abc ++ def ++ case arg of
+  False -> ghi
+  True  -> jkl

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/OpTree.hs

@@ -22,6 +22,7 @@ allowAsOpPar :: LHsExpr GhcPs -> Bool
 allowAsOpPar = \case
   L _ HsLam{}     -> True
   L _ HsLamCase{} -> True
+  L _ HsCase{}    -> True
   L _ HsDo{}      -> True
   _               -> False