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Date: Thu, 14 Jun 2018 10:35:49 +0200
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To: Sara Golemon <pollita@php.net>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Strict switch statements
From: nikita.ppv@gmail.com (Nikita Popov)

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On Thu, Jun 14, 2018 at 6:53 AM, Sara Golemon <pollita@php.net> wrote:

> Just for casual discussion at this point:
> https://github.com/php/php-src/pull/3297
>
> switch ($a) {
>   case FOO:
>       // Works exactly as current behavior.
>       break;
>   case == FOO:
>      // Nearly identical, though not using the ZEND_CASE optimization.
>      // Can probably make this equivalent to `case FOO`, but it felt
> like an interesting direction.
>      break;
>   case === FOO:
>      // Only triggers if `$a === FOO`, no type juggling
>      break;
> }
>
> Love it? Hate it? See obvious flaws?  The implementation is just a
> rushed proof of concept, not something I've labored over, it may well
> have bugs.  Certainly wouldn't target anything earlier than 7.4, if at
> all.
>

I like the general idea here (switch with strict type comparison), but not
super fond of the particular syntax and implementation.

I think if people want to use strict matching, they'll quite likely want to
have it on all cases. Something like "strict switch ($expr) {}" or "switch
strict ($expr) {}" or "switch (strict $expr) {}" or "switch ($expr) strict
{}" or "switch ($expr) { strict; }" or whatever would be preferable in that
case.

Additionally, switch has the issue of fall-through behavior, which is
somewhat unexpected and error prone to many people. It might make sense to
introduce an entirely new "match" statement that conforms a bit more with
how switch-like strictures are implemented nowadays. That is, something like

match ($expr) {
    "foo" => {...},
    "bar" | "baz" => {...},
}

or similar. This might need some more design work to ensure forward
compatibility with potential future algebraic datatypes etc.

Nikita

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