Bug Report

Rector 2.0.7
PHPStan - PHP Static Analysis Tool 2.1.2

I have this basic example that represents my issue:
https://getrector.com/demo/9b6e60af-2af0-4ccb-b525-38e1fd2edf50

the line $var .= 'test'; forces the signature of $var to string and this gets it missaligned with the trait and phpstan isn't happy about it

https://phpstan.org/r/4c634fd4-544a-4cb5-a8a8-a9c8046a5259

Expected Behaviour

i think that rector tries to guess and add the type is fine, but it should not break the signature from the trait.