cabal should detect case errors in build-depends:

(Imported from [Trac #834](http://hackage.haskell.org/trac/hackage/ticket/834), reported by cmh on 2011-04-22)

for example, with a foo.cabal file containing:

build depends: http >= 4000

Resolving dependencies...
cabal: cannot configure foo-0.0.1. It requires http >=4000
There is no available version of http that satisfies >=4000

The solution is of course to specify HTTP, but the user may be led to believe that there is a version problem, which is confusing.

Perhaps a message such as - "Did you mean package HTTP" - Would be appropriate.