const(Object)ref is here!

[Steven Schveighoffer]

On Mon, 06 Dec 2010 15:01:25 -0500, Michel Fortin  
<michel.fortin at michelf.com> wrote:

> On 2010-12-06 14:46:51 -0500, spir <denis.spir at gmail.com> said:
>
>> On Mon, 6 Dec 2010 13:44:41 -0500
>> Michel Fortin <michel.fortin at michelf.com> wrote:
>>
>>> Since we're speaking of the optional use of 'ref', here's a little  
>>> quiz:
>>>  	alias Object A;
>>> 	alias Object ref B;
>>>  	A ref a;
>>> 	B ref b;
>>>  What happens here? Should there be an error somewhere? Where? Also,
>>> what happens if we apply different modifiers at different places?
>>  As I understand the (non-)semantics of 'ref', there should be no  
>> error. Thi
>> s code should considered by the compiler as equivalent to:
>> 	Object a;
>> 	Object b;
>
> And that's what my patch does. It only gets confusing when you add  
> modifiers:
>
> 	alias const(Object)ref A;
> 	alias const(Object ref) B;
> 	alias const(Object) C;
>
> 	A ref a;
> 	B ref b;
> 	C ref c;
>
> With my patch, variables 'a', 'b', and 'c' are all of the same type:  
> "const(Object)ref", the later 'ref' changing the constness of the  
> reference specified in the 'B' alias.
>
> Note that while this behaviour is allowed with an alias, it is *not*  
> allowed directly, so you can't write this for instance:
>
> 	const(Object ref) ref d;
>
> That's an error.

I don't know if that's good.  Redundancy is OK as long as it is  
consistent.  If Object ref is treated as Object everywhere it is used,  
that helps to be able to explain how it works.

Similarly Object ref ref should probably reduce to Object.

We really need to ensure that all types using this notation are reduced to  
their canonical types internally.  Otherwise, strange results would occur.

-Steve