alias this doesn't work for properties.

[John Colvin]

On Friday, 2 August 2013 at 01:55:35 UTC, JS wrote:
> On Friday, 2 August 2013 at 01:46:28 UTC, Jesse Phillips wrote:
>> I'm going to provide a reduced case for the issue you are 
>> having.
>>
>> struct Foo {
>>    double x;
>>    alias x this;
>> }
>>
>> void main() {
>>    Foo a;
>>    a = 8; // Alias this assignment
>>    assert(a.x == 8);
>>    fun(7); // What you want
>> }
>>
>> void fun(Foo a) {
>> }
>>
>> You're claiming that since Foo is requested to "be" a double 
>> calling fun(7) should just assign 7 to x.
>>
>> What you're missing is that it is Foo which behaves like 
>> double, however fun(7) there is no Foo involved, it doesn't 
>> exist. You're actually requesting that a Foo is created, then 
>> to have an assignment of 7 to x of the new temporary Foo.
>>
>> This is not a bug, it is by design. Alias this is sugar of 
>> type it is declared in not the type it is declared to.
>
>
> Um, but I'm not talking about a free function or member 
> function but a property... they are suppose to be special else 
> whats the point. They are suppose to wrap fields.
>
> Because of this "design" you speak of, I can't use a double 
> wrapped(essentially)  type because it is in an interface and I 
> can't use a field in the interface.
>
> What is the difference between
>
> class A
> {
>     int x;
> }
>
> class A
> {
>     private int _x;
>     @property int x() { }
>     @property int x(int v) { }
> }
>
> ? From the outside world there is suppose to be no difference.

In an ideal world, perhaps. There has been a huge amount of 
discussion about properties here before and no solution is 
perfect.