Big restriction: Dart's Stream does not support synchronous mode

When I tried to support getter property of another referenced entity, I came to recognize that it is NOT possible in current Dart.

This is ridiculous restriction.
And it was supported until M3 deprecated the previous synchronous Stream classes.
I think this is pretty much nutty stupid decision.
It must have been done by young limited experienced people who can believe such single bullet approach can solve every thing. Probably it may solve every thing they knew.
That is the problem of the lack of experience.

Whole Dart development somehow has resemblance to early stage of Java around 1995. Probably many of developer of Dart does not remember.

Java has been introduced as a language for Applet. And marketed as such, then it was mainly used for server side. The main reason for the adaption can be contributed several reasons. one aspect is it was free, and it provided a lot of library. Compared to C/C++, these are big difference. Also from language point of view, Java supported class, object oriented features and garbage collection.(and lack of pointer). So compared to C/C++, it was significantly high level language, it was good enough for the most of server side application.

(but it was really backward step compared to other advanced moduler languages, like Mesa/Cedar, Ada, Modula-2, etc. but they never became known to wider audiences, that may have helped Java to proliferated also..)

For Dart,  the current marketing Buz is for browser side language(to replace JavaScript (eventually..)), but as a language, it has also unique feature integrating object/functional idioms in a single language.
Although there are many of such languages(Like Scala), there are no other language which can support both browser and server side.

I think  these two aspects are quite important. Although current marketing focus is in browser side, like polymer, dart:io etc, but it will be used more on server side.
Since the combination of object/functional style is very powerful, once people realized how it is productive, they will never want to write huge amount of equivalent codes in Java. Also sharing the same class from both sides is big plus.

Bottom line is  Dart should target such server side development in much higher priority. Right now, many people seems not developing significant application, they will not complain, but eventually, more people start using Dart, this kind of biased API design will bring a lot of complaints.