[Haskell-cafe] GHC shows wrong line number in error?

[Niklas Hambüchen]

Hello,

I have some code like this (the contents don't really matter):

42  data TestChain next = ChainEntry (forall b . TestG b) next
43                      | ChainDescribe String (Free TestChain...
44                      deriving (Functor)
45
46  -- deriving instance Show a => Show (TestChain a)
47
48  it :: (SomeT typ, Partition t typ) => String -> t -> ...
49  it desc test = liftF (ChainEntry (mkTestG test) ())

And get the error:

Clean.hs:49:43:
    Could not deduce (t ~ b)
    from the context (SomeT typ, Partition t typ)
      bound by the type signature for
                 it :: (SomeT typ, Partition t typ) =>
                       String -> t -> Free TestChain ()
      at Clean.hs:49:1-51
      `t' is a rigid type variable bound by
          the type signature for
            it :: (SomeT typ, Partition t typ) =>
                  String -> t -> Free TestChain ()
          at Clean.hs:49:1
      `b' is a rigid type variable bound by
          a type expected by the context: TestG b at Clean.hs:49:23
[...]

In that last error line, should that not be "Clean.hs:42:..." (as it
references the 'b', which I only really have there), or is that
intended, and if yes, why?

I'm using GHC 7.4.2.

Thanks
Niklas