use case: initialize struct with one field pointing to another

``` zig
const array_of_things = []Thing {
    foo(),
    foo(),
};

struct Thing {
    field1: &i32,
    field2: i32,
}

fn foo() -> Thing {
    Thing {
        field1: // somehow make this reference field2
        field2: 1234,
    }
}
```
