unit r where
    signature H where
        data Foo = Foo
    -- NB: Foo here gets compiled into Foo{v} on the RHS, referring
    -- to the DataCon wrapper!
    -- (There should be a test for type class too)
    module M where
        import H
        d = Foo

unit h-impl where
    module A where
        data Foo = Foo
    module H(Foo(..)) where
        import A

unit s where
    dependency r[H=h-impl:H]