static function duplicateInputFieldMessage($fieldName) { return "There can be only one input field named \"{$fieldName}\"."; }
private function duplicateField($name, $l1, $c1, $l2, $c2) { return FormattedError::create(UniqueInputFieldNames::duplicateInputFieldMessage($name), [new SourceLocation($l1, $c1), new SourceLocation($l2, $c2)]); }