SPJ, quoting Marc:
> | Could somebody tell me how to disambiguate the following program
> |
> | > module Tmp( g ) where
> | > data A p q = A
> | > g :: (Num p,Ord q) => (A p q) -> Bool
> | > g A = g A
>
> I don't understand this. "g" always returns bottom.
If only! The above example looks pathological mainly because Marc was
in Mega-terse mode when producing a canonical example of this bug/feature,
I think; one could expand it back to a more meaningful program, with
the same disambiguation problem.
The trouble here is that compiling this, under 2.02, gives:
tmp.lhs:1: tmp.lhs:4: Ambiguous overloading:
at a use of an overloaded identifier: `g' PrelBase.Ord q{-av0-}
When checking signature(s) for: Tmp.g
2.01 (and earlier) thinks it's OK. I'm not sure which of these is
correct behaviour (or if some tweak in the standard means both are
(or were)).
Alex.
