OptionalargsCall: arguments in order.
The expression starts at the component context: save(), this.save(),
svc.save() where svc is a component member, flag = $event.
call for a method call, write for an assignment.
OptionalmemberCall: method name.
0-based offset in the template text.
OptionalreceiverCall: object the method is called on (svc, a.b); '' for a direct component method.
OptionaltargetWrite: assigned target (hasError, state.error).
Source text of the call or assignment.
OptionalvalueWrite: assigned value.
OptionalvalueWrite: the value reads $event.
A call or assignment inside an event handler expression.