[phobos] Time to get ready for the next release

[Jonathan M Davis]

> On Thu, 21 Apr 2011 17:17:33 -0400, Jonathan M Davis <jmdavisProg at gmx.com>
> 
> wrote:
> >> On Thu, 21 Apr 2011 16:14:22 -0400, Jonathan M Davis
> >> <jmdavisProg at gmx.com>
> >> 
> >> wrote:
> >> >> On Thu, 21 Apr 2011 15:57:57 -0400, Jonathan M Davis
> >> >> <jmdavisProg at gmx.com>
> >> >> 
> >> >> wrote:
> >> >> >> How about the amount of existing code it breaks? How about the
> >> 
> >> fact
> >> 
> >> >> >> that
> >> >> >> it breaks using the same function for both method chaining and
> >> 
> >> with
> >> 
> >> >> >> property syntax?
> >> >> > 
> >> >> > Something like
> >> >> > 
> >> >> > auto b = a.prop1.prop2.prop3;
> >> >> > 
> >> >> > should work. I doesn't at present, but it should. There's a bug
> >> 
> >> report
> >> 
> >> >> > on it.
> >> >> 
> >> >> What about auto b = a.prop1(5).prop2(6).prop3(7); ?
> >> > 
> >> > I'd consider that to be the same. It should work, but it doesn't.
> >> > There's a
> >> > bug report for it.
> >> 
> >> Ahem, so you'd consider auto b = a.prop1(7); valid code under strict
> >> property rules?
> > 
> > Oh wait. You're right. I didn't read that right. No, that wouldn't be
> > legal.
> > That would be both getting and setting. Why would you even try and do
> > that
> > with a property, let alone with several chained together?
> > 
> > - Jonathan M Davis
> 
> First, remember that basic assignments can be chained: x = y = 1; So a
> property should never return void, whether it's a setter or a getter
> logically.

Actually, setters _should_ return void. The chaining should be done by calling 
both the getter and setter functions. The other options is a property function 
which takes nothing but returns a ref. In either case, the chaining would 
work.

> Second, there are situations where you want to be able to support:
> 
> a.prop1 = 5;

Okay. So the setter property prop1 gets called and given a value of 5. That's 
perfectly normal.

> and
> 
> auto b = a.prop1(5).prop2(6);
> 
> or simply
> 
> a.prop1(5).prop2(6).prop3(7);

Those don't look like property calls at all unless prop1, prop2, and prop3 all 
return a value which is callable with a single integer. I don't see the 
problem. I don't see how this relates to

a.prop1 = 5;

If prop1 is setter property function, a.prop1 = 5; makes sense, but then it 
doesn't make sense to call it as a.prop1(5). That wouldn't be calling it as a 
property, and the setter shouldn't be returning anything.

Are you trying to set prop1 to 5, then set prop1's prop2 to 6, and then set 
prop2's prop3 to 7? As long as setters return void (which they're supposed to 
do), that doesn't make any sense at all. A property function is either a 
getter by taking nothing and returning a value, a setter by returning nothing 
and taking a value, or both by taking nothing and returning a ref. I don't see 
how you could have a getter which took a value or a setter which returned one.

@property T prop1(T val){...}

You couldn't call that as a getter, since something like

auto b = a.prop1;

wouldn't have a value to pass as the parameter. I suppose that

a.prop1 = 7;

would work with that definition for prop1, but you'd be throwing away the 
return value unless you did something like

auto b = a.prop1 = 7;

and then something like

auto c = a.prop1;

would be inconsistent with

auto b = a.prop1 = 7;

because in you're using the exact same syntax to mean two very different 
things: in one case a.prop1 is returning using the getter and in another, it's 
returning using the setter. Given the fact that assignment is done right to 
left, the compiler can probably figure out to use the setter's return value 
rather than calling the getter, but if it doesn't assume that, then it's 
ambiguous.

I definitely think that chained assignment should be done by calling the 
setter and then calling the getter, _not_ by using the return value of the 
setter. It was my understanding that a setter _couldn't_ return a value, and I 
think that it's just asking for trouble to allow it.

So, I don't think that the chaining that you're attempting to do makes any 
sense in the first place when using property functions, unless I've just 
totally misunderstood what you're doing.

> syntactically. There's also times/uses for functions to be chained
> together using property syntax i.e.
> 
> a.verb1.verb2.verb3.verb4;
> 
> instead of
> 
> a.verb1().verb2().verb3().verb4();

If they're properties, the first version is correct. If they're not 
properties, then the second version is correct. If the first version doesn't 
work, it's a bug. http://d.puremagic.com/issues/show_bug.cgi?id=2883 relates 
to this.

- Jonathan M Davis