Rationale for classes as reference types

[Steven Schveighoffer]

"Bill Baxter" wrote
> On Fri, Aug 8, 2008 at 1:10 AM, Steven Schveighoffer
> wrote:
>> "A Lahav" wrote
>>> Can anyone please explain the design rationale for classes being 
>>> reference
>>> types exclusively?
>>>
>>> I ask this because I really like my classes to be allocated on the stack
>>> or be value-type data members, the performance boost you get eliminiting
>>> all these unnecessary heap operations is entirely not neglible.
>>>
>>> Otherwise I'll have a real problem considering D for my own use...
>>
>> Because of many reasons Walter has described in the past.  The one that
>> sticks out to me is the chopping effect (don't know if this is the right
>> term).  Let's say a function returns a non-reference class instance, and
>> your function returns a derived instance.  The return value chops off the
>> derived stuff.
>
> It's called "slicing".
>
>> I like the way classes are always references.  But there is a way to 
>> ensure
>> a class gets allocated on the stack:
>>
>> scope c = new MyClass(...);
>>
>> This will allocate the class on the stack.  Be sure not to return a
>> reference to it later though!
>>
>> Another possibility is to use structs instead, which do not have
>> inheritance, and so will not cause the chopping effect.
>
> As has been mentioned in the past, it would definitely be nice if you
> could also make a "scope MyClass" as a member of another class or
> struct.

I also would like this request to be granted: 
http://d.puremagic.com/issues/show_bug.cgi?id=2070

-Steve