class ??? with Haddock

[Wolfgang Jeltsch]

Hello,

I have a datatype
    Relation element1 element2
which derives an Eq instance.  In the Haddock-generated documentation the 
instances section of Relation says
    (Ord element1, Ord element2, ??? element1 element2) => [...].
Why does Haddock generate this mysterious
    ??? element1 element2
context?

Wolfgang