Perfect forwarding in D?

Question

tl;dr: How do you do perfect forwarding in D?

---

The link has a great explanation, but for example, let's say I have this method:

void foo(T)(in int a, out int b, ref int c, scope int delegate(ref const(T)) d)
    const nothrow
{
}

How do I create another method, bar(), which can be called in lieu of foo(), which subsequently calls foo() "perfectly" (i.e. without introducing compilation/scope/etc. problems at the calling site)?

The naive approach

auto bar(T...)(T args)
{
    writeln("foo() intercepted!");
    return foo(args);
}

of course doesn't work because it doesn't handle the ref, in, out, inout, the const-ness of the method, pure-ity, nothrow, etc... and it also limits how the values can be used with r-values.

And I don't know how to handle those possible cases... any ideas?

Answer 1

Your naive approach can be improved upon, though it's still not perfect:

auto ref bar(T...)(auto ref T args)
{
    writeln("foo() intercepted!");
    return foo(args);
}

Now the only problem is scope arguments.