$> cabal install --dry-run --jhc --verbose base
Reading available packages...
Resolving dependencies...
cabal: internal error: impossible
$> cabal install --dry-run --ghc --verbose base
Reading available packages...
Resolving dependencies...
cabal: Distribution/Client/Dependency/TopDown.hs:171:37-73:
Non-exhaustive patterns in lambda
base is supposed to be installable?! I always understood that error to mean "base has to be built with the compiler, cabal-install is incapable of doing this for you".