Cabal allows defining modules multiple times

[nh2]

You can write

exposed-modules:
   Mymodule
   Mymodule
   Mymodule

and cabal build not complain. It will pass it to GHC's command line, which will also not complain, until finally:

    module `mypackage-0.1.0.0:Mymodule' is defined in multiple files: src/Mymodule.hs
                                                                      src/Mymodule.hs
                                                                      src/Mymodule.hs

Cabal should complain in the first place - it doesn't make sense to list a module more than once.

[nh2]

Grr, wrong project page ... sorry for that!