[phobos] The @property experiment

[Jonathan M Davis]

> Le 2011-04-08 à 19:34, Jonathan M Davis a écrit :
> > On 2011-04-08 15:54, Michel Fortin wrote:
> >> You can't overload properties and non-properties today; changing whether
> >> @property is enforced or not doesn't affect that. Fixing this problem is
> >> entirely orthogonal. Whether it can be fixed is unclear however
> >> considering that a property can return a delegate or another callable
> >> type which would make things ambiguous.
> > 
> > The problem is that isFile, isDir, etc. are currently marked as
> > @property, because they should be properties when they take a string,
> > but because you can't overload property functions with non-property
> > functions, the uint versions are also marked with @property. As long as
> > @property isn't enforced, you can continue calling the uint versions as
> > normal functions, but once it's enforced, they become completely
> > uncallable, because UFCS would be required to call them. So, either the
> > compiler needs to be fixed so that the uint versions don't have to be
> > property functions for the string versions to be property functions, or
> > some or all of those functions in std.file need to be changed. I would
> > much prefer that the compiler be changed, but regardless of which
> > solution we should go with, a change _must_ be made before @property is
> > enforced.
> 
> Well, it's not much of a problem as long as enforcing property is optional
> (via a compiler switch) and not the default. But I agree with you; I think
> I misunderstood what you meant in your previous message and I agree that
> there is a problem.
> 
> It's the problem that was discussed at length on the forum a little while
> ago and I'm not sure there was a clear solution. The problem being that
> UFCS (for arrays) and @property don't mix well.
> 
> 	bool isDir(string str) @property;
> 
> 	isDir = "hello";
> 	"hello".isDir;
> 
> Here, the property can be a setter and a getter at the same time! I did not
> try to solve that issue. The changes I made doesn't disallow the above. So
> that's the first problem. The second one is that you want to overload it
> with this:
> 
> 	bool isDir(int attr);
> 
> 	isDir(9);
> 
> Now we're in a real syntactic mess.

I don't see why that's a syntactic mess. In the one case, it takes a string 
and is a property function. In the other, it takes an int and is not a 
property function. The property function is called as a property and the non-
property function is called as a normal function. It seems to me that it 
should work just fine and that UFCS has nothing to do with it. UFCS definitely 
enters in if they're both property functions, since then you'd have to do 
9.isDir (which is hideous IMHO), but arrays work just fine with member 
function call syntax (or whatever it's called for just arrays) and properties. 
I see no ambiguity here at all.

- Jonathan M Davis