Add a testcase for PatternSynonym decls (needs fixing)

src-literatetests/14-extensions.blt

@@ -126,6 +126,26 @@ pattern myLeftVariableName `MyInfixPatternMatcher` myRightVariableName <-
 pattern J :: a -> Maybe a
 pattern J x = Just x
 
+#test pattern synonym multiple cases
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ViewPatterns #-}
+pattern Signed x <- (asSigned -> x) where
+  Signed (Neg x) = -x
+  Signed Zero    = 0
+  Signed (Pos x) = x
+
+#test pattern synonym multiple cases with comments
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ViewPatterns #-}
+pattern Signed x <- (asSigned -> x) where
+  Signed (Neg x) = -x -- negative comment
+  Signed Zero    = 0  -- zero comment
+  Signed (Pos x) = x  -- positive comment
+
+#test Pattern synonym types multiple names
+{-# LANGUAGE PatternSynonyms #-}
+pattern J, K :: a -> Maybe a
+
 #test Pattern synonym type sig wrapped
 {-# LANGUAGE PatternSynonyms #-}
 pattern LongMatcher