Ahn, Ki Yung wrote:
Another problem, which I haven't mentioned, I have when I tried to make additional type family instance declarations that latest (stable)
Typo: I mean type class instance declaration of course.
distributions of GHC 6.10.x does not let me declare instances of (Expandable (Tuple (Map ((,) t2) ys))). When you try declaring such an instance something like this:
instance Expandable (Tuple (Map ((,) t2) ys)) where ...
GHC will give me an error message that type synonyms are not allowed in instance declarations: kyagrd@kyavaio:~/tmp$ ghci -fglasgow-exts -XUndecidableInstances Review3.lhs GHCi, version 6.10.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( Review3.lhs, interpreted )
Review3.lhs:62:2: Illegal type synonym family application in instance: Tuple (Map ((,) t2) ys) In the instance declaration for `Expandable (Tuple (Map ((,) t2) ys))' Failed, modules loaded: none.
So, my impression is that there is little hope even I try fixing this by adding more instance declarations, even if this was an incomplete code because of space restrictions of the review. But I still wanted to double check and discuss this matter with mailing list readers since there were few reports (which we fail to reproduce) that this type checks in their installation of GHC.