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To: Anatol Belski <ab@php.net>, Joe Watkins <pthreads@pthreads.org>
CC: Tom Worster <fsb@thefsb.org>, internals <internals@lists.php.net>, "Levi
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Thread-Topic: Request to withdraw RFC's for nullable types for only return
 values
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Date: Thu, 28 Apr 2016 16:28:03 +0000
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Subject: Re: Request to withdraw RFC's for nullable types for only return
 values
From: dmitry@zend.com (Dmitry Stogov)

Hi,

The BC break in PHP-7.0 was introduced by commit ee9a78a033696ff9546fb1dbfe=
cd28f20477b511=20

Author: Joe Watkins <krakjoe@php.net>
Date:   Mon Mar 28 11:54:25 2016 +0100

Late, there were few more commits that changed and moved the problematic co=
de.

Anatol, I think we should revert this before 7.0.6 release.

Thanks. Dmitry.

________________________________________
From: morrison.levi@gmail.com <morrison.levi@gmail.com> on behalf of Levi M=
orrison <levim@php.net>
Sent: Thursday, April 28, 2016 18:40
To: internals
Cc: Dmitry Stogov; Tom Worster
Subject: Request to withdraw RFC's for nullable types for only return value=
s

I have discovered through a [bug report][1] a case where having
explicitly nullable parameters would be of value.

<?php

interface Foo {
    public function bar(array $baz =3D null);
}

class Hello implements Foo {
    public function bar(array $baz =3D array())  {}
}

?>

You can theoretically change the default value in a sub-type, but in
this case moving away from the default value of null breaks because
the subtype no longer permits null. It is important to realize that we
previously *allowed* this behavior since PHP 5.1 but was fixed in
7.0.6.

If instead we had nullable types separately from default values of
null this could change to:

<?php

class Hello implements Foo {
    public function bar(array | null $baz =3D [])  {}
}

?>

(or a short-form `?array $baz =3D []` if short-form passes)

This preserves the ability to be null but changes the default value.
Of course, there may be other code changes necessary to future-proof
their code but there current code would now work without having to
rewrite any method bodies (just signatures).

In light of this I kindly request that RFCs that add nullable types
for only return values be withdrawn. So that [Union Types][2] and
[Nullable Types][3] can go forward unhindered.


  [1]: https://bugs.php.net/bug.php?id=3D72119
  [2]: https://wiki.php.net/rfc/union_types
  [2]: https://wiki.php.net/rfc/nullable_types