Unbound template type is not narrowed correctly

[mvorisek]

repro: https://psalm.dev/r/db8a695a2d and https://psalm.dev/r/ed1b1e4cfb

I expect no Psalm issue reported.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/db8a695a2d

<?php

class BigIntType
{
    /**
     * @template T
     * @param T $value
     * @return (T is null ? null : int|string)
     */
    public function convertToPHPValue(mixed $value): int|string|null
    {
        if ($value === null || is_int($value)) {
            return $value;
        }

        assert(is_string($value));

        // remove decimals
        $dotPos = strpos($value, '.');
        if ($dotPos !== false) {
            $value = substr($value, 0, $dotPos);
        }

        return $value;
    }
}

Psalm output (using commit 16b24bd):

ERROR: NoValue - 21:29 - All possible types for this argument were invalidated - This may be dead code

[mvorisek]

Does anyone has an idea what is going on and how to fix it?