[Haskell-cafe] type variable question

[Simon Peyton-Jones]

| The commented out signature is the signature that GHC infers for the
| function. When I uncomment that signature, it will no longer type
| check. Why does this happen? Even with the forall and the explicit
| signatures in the where clause, it chokes.

This very question is one that came up only yesterday
        http://hackage.haskell.org/trac/ghc/ticket/1050

Could you boil out a small example?  A good way to shrink code is to replace a function that is not playing a significant role with an error call: replace
        f :: <type>
        f = <big rhs>
with
        f :: <type>
        f = error "urk"

Usually that lets you get a small example.  But if you can't, just send the whole thing

Simon