change 'this' pointer for structs to reference type

[bearophile]

Denis Koroskin:
> I would drop the 'in' keyword altogether (opIn_r is horrible, imo).
> I believe 'lookup' or 'find' methods are generally better.

Okay, thank you all the people in this thread (Jarrett Billingsley too) for helping me see things better. 
Dropping "in" for AAs? That's mad. Or making it return a boolean like in Python? but D isn't Python. I don't want Python here, I already have Python elsewhere.

Removing something from D2 because of SafeD? What?  I don't like to change D2 to suit SafeD (if safeD is wanted then you have to think of it as another language with few differences, like the semantics of "in" that returns a bool in safeD and returns a pointer in D2).

Now I think "in" is fine as it is. I like pointers to refer to structs. I like none of the proposed changes :-)

The point of having a system language is to have a language that allows me to be efficient, avoiding unnecessary AA lookups, and to use pointers without doing strange things, and especially to have ways to control memory exactly, so if I want a struct of 6 bytes I want it (D1 already doesn't work fully this way, because the allocator allocates at powers of two sizes and that's barely acceptable).
If you make D2 become something different from a system language some people will have to work hard to invent yet another language (D1? C2?) to replace it.
Pointers are dangerous, and I don't want to use them to use strings, arrays, etc etc. But I don't like the idea of having to cast a struct reference when I want to use them. Having control over how the memory is used and how pointers are manages is probably the only real advantage the D1 language has over Java (No, speed isn't an advantage, because you can see that in practice HotSpot produces code that is often faster than programs compiled with DMD for D1). So if you remove such things D2 becomes quite less useful.

Bye,
bearophile