<h3>Getting the address of a field... when the field might be a property function</h3>

<div class="language-d"><verbatim>
struct S {
    private int n;
    ref int prop() return { return n; }
}

auto ref eval(T)(auto ref T t) { return t; }

How do we get a pointer to n?
unittest {
    auto s = S(13);
    auto p1 = &s.prop;              wrong
    auto p2 = &(s.prop);            wrong
    auto p3 = &(x => x)(s.prop); error
    int* p4 = &eval(s.prop);        eval helper

    assert(typeof(p1).stringof == "int delegate() ref return");
    assert(typeof(p2).stringof == "int delegate() ref return");
    assert(p2() == 13);

    (*p4)++;
    p4[0]++;

    assert(p1() == 15);

    technically works, but requires this code to be in the same module as
    S's definition, and requires us to know the name of the real variable.
    what if S is a user-provided type?
    int* p5 = &s.n;

    eval works for fields as well
    int* p6 = &eval(s.n);
}