This might seem like a silly question, but what's the reasoning behind the following behaviour?
% ghc-pkg list dataenc
/usr/lib/ghc-6.8.2/package.conf:
% ghc --make -hide-package dataenc -isrc UT.hs
ghc-6.8.2
: unknown package: dataenc
Hiding an uninstalled package doesn't seem to warrant failing compilation!
/M