Am 16.03.2022 um 06:52 schrieb Juliette Reinders Folmer 
> I've just been looking in detail at the Partially Supported Callables 
> deprecation RFC: 
> The RFC explicitly excludes the `is_callable()` function and the `callable` 
> type from throwing deprecation notices.
>> The |is_callable()| function and |callable| type remain side-effect free and 
>> do not throw a deprecation warning. They will continue to accept these 
>> callables until support is removed entirely. 
> While I can fully support this for the `callable` type, I wonder if the 
> decision to not throw a deprecation on use in `is_callable()` is the right 
> one (though I understand the desire to keep it side-effect free).
> Consider these code samples:
>  function foo(callable $callback) {}
>  foo('static::method');
> This function call not throwing a deprecation is not problematic as in PHP 
> 9.0 the function will start throwing a TypeError.

My reaction to your last sentence is actually quite the opposite: This is a 
major problem because code which was "just working" directly goes to a 
TypeError without a migration phase warning about it. This is something I've 
repeatedly advocated against.

>  if (is_callable('static::method')) {
>      static::method();
>  }
> The second code sample, however, is problematic, as in PHP 9.0, the behaviour 
> of this code will be silently reversed for those callbacks which would 
> previously result in `is_callable()` returning true, which makes this a 
> potentially dangerous change without deprecation notice.

I agree with you here: Code which silently changes behavior is also a migration 

- Chris

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