[Issue 19871] Copy constructor rejects valid code if default construction is disabled

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19871

--- Comment #4 from Atila Neves <atila.neves at gmail.com> ---
I disagree wholeheartedly that it should be the correct behaviour. I'm pasting
the same comment again here so it doesn't get lost.

I missed this discussion originally. The reason one one wants to have:

```d
struct Foo {
    this(ref Foo);
    this(Foo);
}
```

is simple: C++ interop. I made it so that the dpp translations actually enabled
D code to call a C++ move constructor by overloading on this.

More importantly, D should be able to do what C++ does without needing rvalue
references. So the equivalent of this should be possible:


-----------------------
struct Foo {
    Foo(const Foo& foo); // copy ctor
    Foo(Foo&& foo); // move ctor
};
-----------------------

As you can imagine, any and all types that have been updated post C++11 that
had copy constructors now have move constructors. Which I'd declare in D how,
exactly?

--