ghci shouldn't link entire package
In this thread: http://www.haskell.org/pipermail/glasgow-haskell-users/2007-January/011839.html Alistair Bayley requests that ghci only link against parts of a package that are actually needed (like ld does) as:
With Takusen, all modules, including the DBMS-specific modules, are compiled into a single library. At present we have 3 DBMS's: Sqlite, Oracle, and PostgreSQL. For example, suppose you had just the Oracle DBMS client libraries installed, and you write a program which only uses the Oracle modules from Takusen. When you link, the gnu ld program attempts to resolve the symbols in only the modules that you've used. You don't need to have PostgreSQL or Sqlite installed, and the linker ignores these modules from the package archive. This is quite nice, because we can distribute the entire library as a single package, and it will work even if the user does not have all of the DBMS client libraries installed. In contrast, when ghci (or runhaskell) attempts to link it tries to resolve all of the symbols in the PostgreSQL and Sqlite modules, and fails because you don't have them installed. The result is that a user of Takusen can't easily use the library with ghci/runhaskell "out of the box", unless they have the full set of DBMS client libraries installed. There are a couple of workarounds, but they're both a bit fiddly, so it'd be nicer (from my POV) if the ghci linker behaved like gnu ld.