Type checks such as is_string() and is_array() make taint detection fail

[TysonAndre]

E.g. https://psalm.dev/r/6a3bc2a667

Expected: TaintedInput should be emitted whether or not there is an is_string() condition. Other conditions such as is_numeric() may be allowed to remove taintedness?
Observed: When if (is_string($var)) is added, psalm fails to infer the variable is tainted.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/6a3bc2a667

<?php // --taint-analysis

$input = $_GET['input'];
// Adding the is_string() or is_array() or condition makes taint detection fail.
if (is_string($input)) {
    echo "$input";
}

Psalm output (using commit 9837a60):

No issues!