wp-includes/SimplePie/src/IRI.php:108Return the entire IRI when you try and read the object as a string
string public function __toString() { return (string) $this->get_iri(); }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/SimplePie/src/IRI.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.