is_resource: adjust type specification for truthy context only

[janedbal]

Should fix phpstan/phpstan#9687

[thg2k]

I don't think you need a dedicated class for this, just replace the stub assertion with:

@phpstan-assert-if-true =resource $value

The (undocumented?) equal sign indicates that if false the opposite should not be asserted.

[janedbal]

Oh god, the whole psalm-originated @phpstan-assert-if-true is so un-intuitive!

Thank you!

[ondrejmirtes]

Since we're trying to fix "Call to function is_resource() with resource will always evaluate to true.", we need a test for ImpossibleCheckTypeFunctionCallRule. Thanks.

[ondrejmirtes]

Thank you!