[PHP-DEV] 5.4a2 trait attribute name conflict resolution

[Alex Howansky]

Hello folks,

I've just grabbed 5.4a2 to play with traits. I've found some behaviour 
which I'm not sure is a bug, an inconsistency, or a design decision.


Consider a trait and a class that implements it but also overrides both 
a trait method and a trait attribute:


trait foo
{
 public $zoo = 'foo::zoo';
 public function bar()
 {
 echo in foo::bar\n;
 }
}

class baz
{
 use foo;
 public $zoo = 'baz::zoo';
 public function bar()
 {
 echo in baz::bar\n;
 }
}

$obj = new baz();
$obj-bar();
echo $obj-zoo, \n;

We get:

in baz::bar
foo::zoo

It seems this is not correct and that it should be:

in baz::bar
baz::zoo

The traits RFC pretty clearly states that if a class method conflicts 
with a trait method then the trait method will be ignored, which is 
what's happening, but it says nothing about what happens to attributes 
in that same condition. Is this a bug?


Thanks,

--
Alex Howansky



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Re: [PHP-DEV] 5.4a2 trait attribute name conflict resolution

[Alex Howansky]

That makes sense if it would overwrite the methods as well, but
otherwise it seems like it provides inconsistent functionality.


Exactly. At the least, it's inconsistent. If it's a bug, then it seems 
the question becomes:


Is the bug this:

Properties defined in a trait should be overridden by same-named 
properties defined in a class that use the trait.


Or (as pointed out by Anthony) this:

You shouldn't be able to define properties in a trait.

--
Alex Howansky



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Re: [PHP-DEV] 5.4a2 trait attribute name conflict resolution

[Alex Howansky]

Just curious, if the trait property is set to private what happens?


Ooh, good question.

PHP Fatal error:  baz and foo define the same property ($zoo) in the 
composition of baz. However, the definition differs and is considered 
incompatible.


--
Alex Howansky



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Re: [PHP-DEV] 5.4a2 trait attribute name conflict resolution

[Alex Howansky]

 Best practice, always choose trait property names carefully/~unique
 so that you don't run into conflicts.

Sure, but in this case, I created the conflict intentionally because I 
*want* to override it, and I'm not allowed to like I am with methods. 
Don't you think that's inconsistent?


 The short answer is it's not a bug but maybe an implementation
 issue... should it be an E_WARNING instead of E_STRICT?

At least. Consider the situation where I'm using classes/traits from 
somebody else's library that I may not be intimately familiar with. I'll 
have to know what every one of their properties is named so I can plan 
my code accordingly -- else I'll silently start getting their values in 
what I think are my variables.


--
Alex Howansky



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