Overlapping, undecidable, incoherent -- or worse?

[MR K P SCHUPKE]

that is not the case with "-fallow-undecidable-instances" ... as far as
I understand it , ghc never considers the dependancies when selecting an
instance. If you don't think so you will need to show me an example where
it clearly does... as I haven't seen one yet (but just because I haven't
seen it doesn't mean its not possible),,,

IMHO, things should either stay as they are (only instance heads supported)
or it should switch to full Prolog style backtracking.

Given who 
I mean, given two instances like:

	instance a b c
	instance d e f

there is no way to tell between them... if you said choose a in preferenc
'a' would be chosen all the time. 

	Keean.