Bug report

PHPStan 0.12.15 incorrectly recognizes is_numeric() with non-constant int|string as always-true expression.

Code snippet that reproduces the problem

https://phpstan.org/r/34aaa80e-0c2c-4773-a38d-b9bf6b219017

This seems to only be reported when strict rules are enabled, however it started happening after update from 0.12.14 to 0.12.15 with phpstan-strict-rules being unchanged (0.12.2) so I assume this is an issue in PHPStan core.

Expected output

No error reported.