Dart2js does not accept "x = (){return 42;}()" in initializer list.

Example code:

class C {
&nbsp;final int x;
&nbsp;C() : x = (){ return 42; }();
}

main() {
&nbsp;&nbsp;print(new C().x);
}

This errs with the message:
initcall.dart:3:28: unexpected token '('
&nbsp;C() : x = (){ return 42; }();

The grammar allows the syntax.
