RFC: Anonymous Class Lexical Scope

[krakjoe]

RFC

[nikic]

What happens with use($a, $a) and similar?

[krakjoe]

Solved for use($a, $a), but properties are a bit difficult to detect duplicates of, I think ...

[Majkl578]

💯 This is definitely one of the main reasons why writing anonymous classes is irritating now.
What would be really cool is to specify passed variables, rename them and possibly also specify visibility.
For example this:

new class use ($foo->bar as private $bar)

would create private property `$bar.

This would be also reusable for passing $this:

new class use ($this as private $outsideScope)

[jesseschalken]

Very cool! I don't know where to comment on the RFC so I'll comment here.

If this is the syntax for variable capture in anonymous functions:

function () use ($glow) {
    print $glow;
}

I would naively expect this to be the syntax for variable capture in anonymous classes:

new class () use ($glow) {
    public function printGlow() {
        print $glow;
    }
}

But the correct code is actually:

new class () use ($glow) {
    public function printGlow() {
        print $this->glow;
    }
}

This seems jarring to me. $this->glow looks like a reference to a property that isn't defined, and use ($glow) looks like a variable being captured that isn't used.

Might I suggest actually requiring the public/protected/private keyword in the use clause for an anonymous class. This makes it obvious that you're declaring a property and not a variable, and keeps the door open for adding direct variable capture (not via a property) as a feature later.

new class () use (private $glow) {
    public function printGlow() {
        print $this->glow;
    }
}

This also has a handy correspondence with the property+constructor initialization shorthand in Hack and TypeScript:

class Foo {
    public function __construct(private $glow) {
    }
}

[nikic]

For use(&$foo->bar) shouldn't this compile BP_VAR_W?

[jesseschalken]

Another possible alternative:

function foo($glow) {
    new class () {
        private $glow = $glow;
        public function printGlow() {
            print $this->glow;
        }
    }
}

This makes it obvious how to use a different name, and possibly permits an arbitrary expression rather than just $var and $this->var.

[krakjoe]

This patch is actually completely wrong, it's so obvious this morning ...

The syntax can be changed after the fact, there is a problem with the implementation that must be fixed first.