Add DateTimeModifyReturnTypeExtension

[VincentLanglet]

Closes phpstan/phpstan#4927

I think it also closes phpstan/phpstan#1934. There is a lot more method listed:

• diff
• format
• getOffset
• getTimezone
• setTime

But I never succeed to get false with those method, except when I passed a parameter with a wrong type.

$dateTime->diff('foo') // false in php 7.4, exception in 8.0

This is reported by phpstan as an error, so I don't think a returnType extension might be needed to say it's return false in php 7.4.

[ondrejmirtes]

This code can cause PHPStan to report warnings: https://3v4l.org/9eHGQ The @ operator should be used

[VincentLanglet]

Done

[ondrejmirtes]

This will crash if someone calls ->modify() without args.

[VincentLanglet]

Done

[ondrejmirtes]

I don't like the usage of inheritance here. Instead, the class name should be asked for in the constructor and the class should be registered two times with different arguments.

[VincentLanglet]

Done

[ondrejmirtes]

What's the scenario for this if? I'd rather have you to check count($constantStrings) === 0 first and return $defaultReturnType then.

[VincentLanglet]

It's similar too DateTimeConstructorThrowTypeExtension.

I would say it's to handle a phpdoc like 'foo'|'bar'|somethingElseWhichIsNotAConstantString or a situation

if ($foo) {
     $arg = 'foo';
} else {
    $arg = ... ;
}
$dt->modify($arg);

[VincentLanglet]

I don't think the failure are related to my PR @ondrejmirtes

[ondrejmirtes]

Coding standard failed, otherwise it looks good to merge.

[ondrejmirtes]

Also please note I changed the configuration: c2e3f22 (no backslash needed)

[VincentLanglet]

Coding standard failed, otherwise it looks good to merge.

Fixed.

Also, should it target the 1.7.x branch or 1.6.x one ?

[ondrejmirtes]

1.6.x would be better, thanks.

[VincentLanglet]

1.6.x would be better, thanks.

Done :)

[ondrejmirtes]

Thank you!