I'd like to point out some puzzling behaviors in Traits as they exist in the
production releases of PHP 5.4.
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1. Name collisions between a trait method and a class method using the trait go
unreported, the class silently shadowing the trait method:
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trait T {
function foo() { $this->bar; }
function bar() { echo 'trait'; }
}
class C {
use T;
function bar() { echo 'class'; }
}
$c = new C;
$c->foo(); // "class"
Proposed behavior: Fatal error on collision, unless the method is imported with
a unique name using the { ... as ... } syntax.
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2. Using "as" syntax when importing a trait does NOT rename a method, but
creates an alias CLONE, the original method still callable.
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trait T {
function bar() { echo 'trait'; }
}
class C {
use T { bar as foo; }
}
$c = new C;
$c->bar(); // "trait"
Proposed behavior: the original name should be only accessible within the trait
and its methods, not from the class methods or by calling the class instance's
methods from outside.
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3. Properties silently collide in traits and classes.
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trait T1 {
private $foo;
trait T2 {
private $foo;
}
class C { use T1, T2; } // No error.
Proposed behavior: An error is produced only when the properties differ in
visibility or a default value, which is clearly insufficient to determine
they're used for the same purpose, and hold the same data. Instead they should
use the same logic as method conflicts: fatal error on name collision.
Alternatively, each trait property whould be accessible within the trait that
defines it, not from other traits used in the same class, or the class itself.
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4. The documentation says static propeties can't be defined by traits. Yet they
can.
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I don't know what's the bug here: a doc bug, or a code bug. For consistency,
static properties should work, if instance properties work. Nothing is gained
supporting it half-way.
Not many use 5.4 yet, so the sooner all this is clarified, the better, before
it becomes completely unfixable due to BC. Feedback?
Stan
