wp-includes/rest-api.php:2330Validates a null value based on a schema.
$valuemixed$paramstringtrue|WP_Errorfunction rest_validate_null_value_from_schema( $value, $param ) { if ( null !== $value ) { return new WP_Error( 'rest_invalid_type', /* translators: 1: Parameter, 2: Type name. */ sprintf( __( '%1$s is not of type %2$s.' ), $param, 'null' ), array( 'param' => $param ) ); } return true;}Introduced in 5.7.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/rest-api.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.