auto foo()

{

    int high;

    auto window = S();

    window.map!(bs => bs.map!(bar => high));

}

​

struct S

{

    auto front()

    {

        return [3];

    }

}

​

template ElementType(R)

{

    static if (is(typeof(R.front.init) T))

        alias ElementType = T;

}

​

template map(alias fun)

{

    void map(Range)(Range)

    {

        alias RE = ElementType!Range;

        assert(!is(typeof(fun(RE.init))));

        MapResult!(fun, Range) x;

    }

}

​

int front(int[] a) { return 0; }

​

struct MapResult(alias fun, Range)

{

    Range _input;

​

    void front()

    {

        fun(_input.front);

    }

}

​

void main() { }