D inout article

local_ref.d

struct LocalRef(T)
{
    private T* _ref;
    this(ref T t) { _ref = &t; }
    ref T get() pure { return *_ref; }
}

void main()
{
    int x;
    auto y = LocalRef!int(x);
    y.get = 5;
    assert(x == 5); // y is a reference of x
}

local_ref_update1.d

struct LocalRef(T)
{
    ...
    ref T get() pure const { return *_ref; }
}

local_ref_update2.d

struct LocalRef(T)
{
    ...
    ref T get() pure const { return *cast(T *)_ref; }
}

local_ref_update3.d

struct LocalRef(T)
{
    ...
    ref T            get() pure           { return *_ref; }
    ref const(T)     get() pure const     { return *_ref; }
    ref immutable(T) get() pure immutable { return *_ref; }
}