wp-includes/SimplePie/src/Misc.php:1819$mimestringstring public static function parse_mime(string $mime) { if (($pos = strpos($mime, ';')) === false) { return trim($mime); } return trim(substr($mime, 0, $pos)); }2 changes between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
$mime retyped from untyped to string.verified against sourcenone to string.verified against sourcesrc/wp-includes/SimplePie/src/Misc.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.