| ⇢ | A | CallableHiddenValidator added | |
| ⇢ | A | ValidationResult added |
| ⇢ | A | ValidationResult::merge() added | |
| ⇢ | A | Hidden::validate() added | |
| ⇢ | A | CallableHiddenValidator::__construct() added | |
| ⇢ | A | CallableHiddenValidator::validate() added | |
| ⇢ | A | ValidationResult::addError() added | |
| ⇢ | A | ValidationResult::getErrors() added | |
| ⇢ | A | ValidationResult::isValid() added | |
| ⇢ | A | Hidden::addValidator() added | |
| C | ↘ | D | Form::isValid() got worse |