Bug report

Using phpstan version 1.9.4, setting rememberPossiblyImpureFunctionValues to false incorrectly fails on use of nonexistent classes guarded by class_exists.

Code snippet that reproduces the problem

test-class_exists.php

<?php
if (!class_exists('nonexistentclass')) throw new \Exception('nonexistentclass');
$x = new \nonexistentclass();

phpstan.neon

parameters:
  phpVersion: 80024
  level: 5
  paths: [ . ]
  rememberPossiblyImpureFunctionValues: false

(I could not reproduce the issue on phpstan.org/try because this does not allow to specify the config parameters)

Expected output

phpstan should not report any errors, as it does with rememberPossiblyImpureFunctionValues: true. Instead it reports Instantiated class nonexistentclass not found.