[Yhc] Incomprehensible error messages

[David Fox]

On 6/4/07, Stefan O'Rear <stefanor at cox.net> wrote:
> On Mon, Jun 04, 2007 at 12:05:56PM -0700, David Fox wrote:
> > I created this file by simplifying an error I was getting from a
> > program that uses the Javascript types.  If you remove the type
> > signatures for f1 and f2 it compiles, but how do I fix the error I get
> > when I compile with the signatures?
> >
> > module Main where
> >
> > type CPS c a = (a -> c) -> c
> >
> > class CNode a
> > data TNode = TNode
> > instance CNode TNode
> >
> > m :: TNode -> TNode -> Bool
> > m a b = f1 b a $ \_ -> True
> >
> > f1 :: (CNode a, CNode b) => a -> b -> CPS c a
> > f1 a b f = f2 a b $ \_ -> f a
> >
> > f2 :: (CNode a, CNode b) => a -> b -> CPS c a
> > f2 a b f = f1 a b $ \_ -> f a
> >
> > This gives these messages:
> >
> > yhc -linkcore Browser3.hs
> > Compiling Main             ( Browser3.hs )
> > -- during after type inference/checking
> > Error: No default for  Main.CNode at 16:1-16:29.(Id 215,[(Id 200,Id 250)])
> > Error: No default for  Main.CNode at 16:1-16:29.(Id 214,[(Id 200,Id 251)])
> > Error: No default for  Main.CNode at 13:1-13:29.(Id 220,[(Id 200,Id 248)])
> > Error: No default for  Main.CNode at 13:1-13:29.(Id 219,[(Id 200,Id 249)])
> >
> > You can replace the CNode/TNode and CPS declarations with this:
> >
> > import DOM.Level1.Html
> > import DOM.Level1.Dom
> > import CPS
> >
> > same result.
>
> Works fine in both GHC and Hugs.  I don't think this bug will be fixed,
> because the current typechecker is already on the chopping block (see
> Matthieu's SoC project).  So just wait a few months, or help.
>
> Stefan

Where do I see Matthieu's SoC project?  I scanned the last six months
of the YHC mailing list, maybe I missed it.