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Date: Mon, 16 Jul 2018 11:09:52 -0500
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Subject: Re: [PHP-DEV] Non-nullable properties
From: larry@garfieldtech.com (Larry Garfield)

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On Monday, July 16, 2018 9:55:31 AM CDT Rowan Collins wrote:
> On 16 July 2018 at 14:28, Marco Pivetta <ocramius@gmail.com> wrote:
> > These don't really need explicit tests in most cases, but rather static
> > analysis (currently happening via docblocks). Static analysis tools like
> > vimeo/psalm already pick this up.
> 
> Then why do we need the type hints at all?
> 
> > I'd even be happy to get type hints that only have effect on
> > `ReflectionProperty#getType()` as a massive improvement over the current
> > situation we've monkey-patched us into, but the patch is indeed consistent
> > with PHP's current state.
> 
> I disagree that it's consistent. It introduces an entirely new kind of null
> reference ("declared but uninitialised"), which will require *more* careful
> checks than forcing the value to be initially null, and will undoubtedly
> further annoy those who already claim that isset() is broken (the RFC
> doesn't even mention it, but I presume uninitialised properties will return
> false from isset(), but throw an error from is_null()).
> 
> If all typed properties require a valid default value, the patch is
> simpler, errors are raised at a line where you can fix them, and the
> language remains consistent - if you're promised a Foo, you get a Foo, not
> a "whoops, why isn't there a Foo here?" error.
> 
> 
> Regards,


This is a possibly highly stupid idea, but I'll throw it out anyway so that it 
can at least be explicitly rejected in that case...

Since Swift was mentioned before as a good example, what about borrowing from 
Swift?  Viz:

class Foo {

  protected Bar $b;

  // This runs before __construct, is not inherited, and cannot 
  // ever be skipped.  If this method exits and any property is still
  // value-less, TypeError immediately.
  protected function __init() {
    $this->b = new Bar();
  }

  public function __construct() {
    Behaves as it always has.
  }
}

That's similar to the "initialize" flag inside the constructor, but splits it 
off to a separate method that is devoted to just that purpose; it therefore 
has no parameters, ever, and if you want to initialize an object property 
based on a constructor argument then you must either make it explicitly 
nullable or initialize it to a dummy value first.

Which... I realize may not work well for service dependencies as the 
dependency chain could get deep.  Of course, that use case is generally a 
protected property not publicly accessible, so making it nullable and trusting 
yourself to populate it in the constructor is likely "safe enough".

Thoughts?

--Larry Garfield
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