Fix the @var type hint for various NodeList<Node> usages.

[zimzat]

• Remove = [] from a couple of usages, as this is now considered invalid typing.
• Adjust a few boolean checks to explicitly check for === null now
  • (the default when not set during manual construction prior to typed properties).

Discussion:

With regard to = [] and/or |null/ = null, what approach would you want the library to take?

If you want the library to start using public NodeList $interfaces, after PHP 7.4 becomes the minimum version, then attempting to access it directly would cause uninitialized errors unless it's public ?NodeList $interfaces = null. Ensuring it's always initialized with the expected value would allow for fluid object access. At initial glance I don't see anywhere things are explicitly set to null (though I could be very wrong) so maintaining nullability doesn't seem necessary?

Direction:

• Find a way to ensure they're always initialized as NodeList during construction?
  • Extending the __construct() method to do something like $this->interfaces = $this->interfaces ?? new NodeList([]) is one possibility.
• Mark all of them as |null and default to = null?
• Other?

I'd lean toward ensuring they're initialized as NodeList, but could see going some other way depending on where you see the architecture going.

Thanks!

[coveralls]

Coverage decreased (-0.02%) to 86.288% when pulling 7fecf69 on zimzat:update-type-var-declarations into 4f34309 on webonyx:master.

[simPod]

About the initialization, here's some context #675

[spawnia]

Remove = [] from a couple of usages, as this is now considered invalid typing.

Nicely done!

With regard to = [] and/or |null/ = null, what approach would you want the library to take?

Some properties can legimately not exist in some nodes, in which case defaulting initialization to null seems fine to me.

For properties that must not be null but may not always be initialized after construction, we should avoid typing them as nullable. We can use isset() to safely check if it is initialized (or null):

class Foo {
    var $bar;
}

$foo = new Foo();
var_dump(isset($foo->bar));
// bool(false)

$foo->bar = null;
var_dump(isset($foo->bar));
// bool(false)

This plays nicely with PHP 7.4 typed properties, which I would like to use at some point - probably far into the future.

I'd lean toward ensuring they're initialized as NodeList

That comes with a performance cost, as object construction is not free.