Hugs and GHC seem to disagree on this one:
ERROR “./DeBruijn.lhs”:111 – Cannot justify constraints in explicitly typed binding
*** Expression : (\)
*** Type : (Named a, Bind b) => Bwd a -> b -> b
*** Given context : (Named a, Bind b)
*** Constraints : Named a
Peter directed me towards:
http://www.mail-archive.com/haskell@haskell.org/msg15390.html
So presumably some more type annotations are required. Can’t work out what though…