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Date: Sat, 7 Nov 2020 17:37:49 +0200
Message-ID: <CAM0Ccxg4RVRsaw4-EBtRXki0dqnfu7ZGKvEx3StgTcOsV-CX_w@mail.gmail.com>
To: =?UTF-8?Q?Olle_H=C3=A4rstedt?= <olleharstedt@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Union `&` operator
From: zsidelnik@gmail.com (Eugene Sidelnyk)

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Yes.
And I think it will be good if enforced by language.

On Sat, Nov 7, 2020, 5:33 PM Olle H=C3=A4rstedt <olleharstedt@gmail.com> wr=
ote:

> 2020-11-07 15:12 GMT, Eugene Sidelnyk <zsidelnik@gmail.com>:
> > When you follow ISP, you probably would have a lot of interfaces.
> > Thus, client code may require an object to implement a bunch of
> interfaces
> > depending on functionality needed.
> >
> > Consider class `Bar`:
> >
> > ```php
> >
> > interface A {}
> >
> > interface B {}
> >
> > interface C {}
> >
> > interface D {}
> >
> > interface E {}
> >
> > class Bar implements A, B, C, D, E {
> >     //
> > }
> > ```
> >
> >
> > And some code, which uses `Bar`, but depends rather on interfaces, whic=
h
> > functionality is actually needed:
> >
> > ```php
> > function foo(A & B & E $object) {
> >   // some work
> >
> >   var_dump($object);
> > }
> > ```
> >
> > It is currently feasable like this (ugly):
> >
> > ```php
> > function foo(A $object) {
> >   (function(B $object) {
> >
> >     (function(E $object) {
> >
> >         // some work
> >
> >         var_dump($object);
> >
> >     })($object);
> >
> >   })($object);
> > }
> > ```
> >
> > Or like this (more readable, but still):
> >
> > ```php
> > function foo(A | B | E $object) {
> >
> >   if (!$object instanceof A) {
> >     throw new \RuntimeException();
> >   }
> >
> >   if (!$object instanceof B) {
> >     throw new \RuntimeException();
> >   }
> >
> >   if (!$object instanceof E) {
> >     throw new \RuntimeException();
> >   }
> >
> >   // some work
> >
> >   var_dump($object);
> > }
> > ```
> >
> > Another possible option is to create interface, which combines `A`, `B`=
,
> > `E`, but in some cases it would lead us to interfaces explosion.
> >
> > This idea proposes to eliminate `instanceof` checks by introducing `&`
> > union operator.
> >
>
> You mean intersections? Psalm supports this notation.
>

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