+-- SrcLoc is an instance of Ord so that we can sort error messages easily
+instance Eq SrcLoc where
+ loc1 == loc2 = case loc1 `cmpSrcLoc` loc2 of
+ EQ -> True
+ other -> False
+
+instance Ord SrcLoc where
+ compare = cmpSrcLoc
+
+cmpSrcLoc NoSrcLoc NoSrcLoc = EQ
+cmpSrcLoc NoSrcLoc other = LT
+
+cmpSrcLoc (UnhelpfulSrcLoc s1) (UnhelpfulSrcLoc s2) = s1 `compare` s2
+cmpSrcLoc (UnhelpfulSrcLoc s1) other = GT
+
+cmpSrcLoc (SrcLoc s1 l1) NoSrcLoc = GT
+cmpSrcLoc (SrcLoc s1 l1) (UnhelpfulSrcLoc _) = LT
+cmpSrcLoc (SrcLoc s1 l1) (SrcLoc s2 l2) = (s1 `compare` s2) `thenCmp` (l1 `cmpline` l2)
+ where
+ l1 `cmpline` l2 | l1 <# l2 = LT
+ | l1 ==# l2 = EQ
+ | otherwise = GT
+