wp-includes/class-wp-error.php:91Retrieves the first error code available.
string|int public function get_error_code() { $codes = $this->get_error_codes(); if ( empty( $codes ) ) { return ''; } return $codes[0]; }Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-error.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.