- pruned_matches
- | null all_unifs = foldr insert_overlapping [] all_matches
- | otherwise = all_matches -- Non-empty unifs is always an error situation,
- -- so don't attempt to pune the matches
+ pruned_matches = foldr insert_overlapping [] all_matches
+ -- Even if the unifs is non-empty (an error situation)
+ -- we still prune the matches, so that the error message isn't
+ -- misleading (complaining of multiple matches when some should be
+ -- overlapped away)