regression in handling constant strings in unions #8568
Description
Bug report
reported by @schlndh in https://github.com/phpstan/phpstan-src/pull/1979/files#r1053594574
Code snippet that reproduces the problem
https://phpstan.org/r/33df1d6b-50e1-4aed-ac3b-bb5f1a8ac66b
Expected output
non-falsy-string