On Mon, Jan 30, 2006 at 05:21:50PM +0300, Bulat Ziganshin wrote:

the attached program compiles under GHC, but not with Hugs. as far as i see, Hugs don't use dependencies in class headers to figure out that there is only one "vMkIOError" that can be called in the last definition

The example (slightly simplified): class (Monad m) => Stream m h | h->m where vMkIOError :: h -> Int data BinHandle = forall h . Stream IO h => BinH h instance Stream IO BinHandle where vMkIOError (BinH h) = vMkIOError h OK, I think it's a bug (though the example is bizarre). Sadly Hugs's support for FDs is rough around the edges (and unlikely to improve soon).