error method
Implementation
void error(OnState<TS> onState, ValueWidgetBuilder<Object> builder) {
_add(onState,
(c, stated, child) => builder(c, stated.extractError(), child));
}
void error(OnState<TS> onState, ValueWidgetBuilder<Object> builder) {
_add(onState,
(c, stated, child) => builder(c, stated.extractError(), child));
}