Weird template error

[Nick Sabalausky]

"Jarrett Billingsley" <jarrett.billingsley at gmail.com> wrote in message 
news:mailman.19.1227139335.22690.digitalmars-d at puremagic.com...
> On Wed, Nov 19, 2008 at 4:59 PM, Brian <digitalmars at brianguertin.com> 
> wrote:
>> I don't understand why we wouldn't want properties either.  Another issue
>> I've had a couple times, although there might be a good reason for this
>> I'm not aware of:
>>
>> class Foo {
>>        int x;
>> }
>>
>> void set(inout int x) {
>>        x = 10;
>> }
>>
>> void main() {
>>        auto foo = new Foo();
>>        set(foo.x); // This works fine
>> }
>>
>> But then if you need to make x a property:
>>
>> class Foo {
>>        int _x;
>>
>>        int x() { return _x; }
>>        int x(int val) { return _x = val; }
>> }
>>
>> You get "Error: foo.x() is not an lvalue"
>
> That one's trickier, even if you did have properties.  Even "true"
> properties would still boil down to a function call.  Set expects a
> reference to an integer.  How do you convert getter/setter functions
> into an integer?
>

class Foo
{
    // This syntax is a modified version of C#'s properties
    int x
    {
       get { return x.rawValue; };
       set { x.rawValue = newValue; }
    }
}

void makeTen(inout int x)
{ x = 10; }

void main()
{
       int i;
       auto foo = new Foo();

       makeTen(i);  // Ok

       // compiler knows that foo.x is an int property
       // and turns this:
       makeTen(foo.x);

       // into this:
       auto _foo_x = foo.x;
       makeTen(_foo_x);
       foo.x = _foo_x;

       // and finally this:
       auto _foo_x = foo.x.get();
       makeTen(_foo_x);
       foo.x.set(_foo_x);
}

> It doesn't work now because foo.x is a function, not an int.
>
> Also, I wonder if ref returns could help here..