tcfail034.hs:17:
    Could not deduce `Integral a' from the context (Num a, Eq a)
    Probable fix:
	Add `Integral a' to the type signature for `test'
    arising from use of `mod' at tcfail034.hs:17
    In the first argument of `(==)', namely `(x `mod` 3)'
    In the right-hand side of an equation for `test': (x `mod` 3) == 0