unit p where
    signature H where
        x :: Bool
    module PP where
        y = False
    module P where
        import PP
        import H
        z :: Bool
        z = x || y

unit impls where
    module H where
        x = False
        -- y = True
    module H2 where
        x = True

unit main where
    dependency impls
    dependency p[H=impls:H] (P as P2, PP)
    module Main where
        import PP
        import qualified P2
        main = print P2.z