3 Jul
2008
3 Jul
'08
4:14 p.m.
actually, GHC gives me "could not deduce Blah f a from Blah f1 a" first. It seems that desugaring type function notation into an additional constraint helps, so there's something odd going on:
Silly me, I didn't paste the whole type error. Yes, GHC gives both. I should add that I tested this under GHC 6.8.2. But this is known not to work with a (one/two months old) GHC head.
yes, I tested with 6.9.20080514. And just in case my phrasing was unclear: desugaring the type function application makes the error go away, so you have a workaround. It is just confusing that this example shows that the "desugaring" is not a desugaring, in the current implementation.. Claus