Bug report

After updates to version 2.1.15 from 2.1.14, phpstan started to report errors on the previously correct code.

Example code:

class SomeClass{    use MyTrait;}
class SomeClass2{    use MyTrait;}

trait MyTrait
{
    public function getRandom(): int
    {
        $value = random_int(1, 100);
        if (is_a($this, SomeClass::class)) { // Here we have an "error"
            return $value * $value;
        }
        return $value;
    }
}

Errors are:

 Call to function is_a() with $this(SomeClass2) and 'SomeClass' will always evaluate to false.  
         🪪 function.impossibleType     
Call to function is_a() with $this(SomeClass) and 'SomeClass' will always evaluate to true.
         Error Identifier: function.alreadyNarrowedType

Previously there was no errors and code runs without an issues.

Code snippet that reproduces the problem

https://phpstan.org/r/1638d012-268e-49ba-afeb-2924a69571c3

Expected output

no errors

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