3 Could not deduce `Eq (Foo a b)' from the context (Ord a, Ord b)
5 Add `Eq (Foo a b)' to the instance declaration context
6 Or add an instance declaration for `Eq (Foo a b)'
7 arising from the instance declaration at drvfail004.hs:5
8 In the instance declaration for `Ord (Foo a b)'