collection/lib/qq.dart - third_party/dart-pkg - Git at Google

 class C {
   var x;
   C() : x = null ?? <int, int>{} {}
 }

 main() {
   print(new C());
 }
	class C {
	var x;
	C() : x = null ?? <int, int>{} {}
	}

	main() {
	print(new C());
	}