how to use ghci-debugger with packages

[Frederik Eaton]

Hello,

I have a program which uses some code in a package, and I would like
to be able to find out the source of an error which is occuring inside
that package. Can I use the ghci-debugger to do this? If I try to set
a breakpoint inside the package, it says:

"cannot set breakpoint on Vector.Sparse.Wrappers.vmergeOp: module
Vector.Sparse.Wrappers is not interpreted"

But this page:

http://www.haskell.org/ghc/dist/current/docs/users_guide/ghci-debugger.html

has no use of the word "package", so I assume that reading that (long)
document won't ansnwer my question...

Thank you,

Frederik

-- 
http://ofb.net/~frederik/