Duplicate or overlapping instance declarations:
  tcfail073.hs:7: {Eq (a, b)}
  /home/simonmar/builds/i386-unknown-linux/ghc/compiler/../lib/std/PrelTup.hi:66: {Eq (a,
										       b)}

tcfail073.hs:8:
    Could not deduce `Eq a' from the context (Eq (a, b))
    Probable fix:
	Add `Eq a' to the instance declaration context
    arising from use of `==' at tcfail073.hs:8
    In the right-hand side of an equation for `==': m == o