Overlapping instances

[Sean Seefried]

Why is it that this source file
-- begin code --
class Numeric a 
    where describe :: a -> String

instance Integral a => Numeric a 
    where describe n = "Integral"

instance Floating a => Numeric a 
    where describe n = "Floating"
-- end code --

produces  the error message

-- begin code --
*** This instance   : Numeric a
*** Overlaps with   : Numeric a
*** Common instance : Numeric a
-- end code --

even though I have overlapping instances turned on.  The "+o" option.
------------------------------------------------
Sean Seefried
School of ITEE
The University of Queensland
Ph: 3365 8301
Mob: 0416 338 636