foreign exports not taken into account when calculating -fwarn-unused-imports

[duncan]

Here we have a program that imports and uses liftM from Control.Monad, but only as a result of being used in the definition of a function that is foreign exported.

module Foo () where

import Control.Monad (liftM)

foo :: IO ()
foo = id `liftM` return ()

foreign export ccall "hs_foo"
  foo :: IO ()

GHC 6.6 and HEAD report:

foo.hs:3:0:
    Warning: Module `Control.Monad' is imported, but nothing from it is used,
               except perhaps instances visible in `Control.Monad'
             To suppress this warning, use: import Control.Monad()

So I suppose all that needs to happen is to add in foreign exports as roots when building the usage graph.

[simonpj]

Fixed thank you.

Simon