dart2js: incomplete test for Iterable<int>

[rakudrama]

This program does not throw a TypeError when compiled with --strong:

foo(Iterable<int> a) {
  print(a);
}

main() {
  dynamic f = foo;
  f(<String>['hi']);
}

The generated code calls listSuperNativeTypeCheck:

    function(a) {
      H.printString(H.S(H.listSuperNativeTypeCheck(a, "$isIterable")));
    },

It is probably best to simply always avoid listSuperNativeTypeCheck, since it can't handle type arguments, and contains two getInterceptor calls. The logic for picking the 'optimized' xxxTypeCheck is based on the Dart 1 libraries many years ago.

[rakudrama]

Fixing this is blocked on #32829.
If we fix the 'is Iterator' test, then the sync* Iterables will fail.

[sigmundch]

@rakudrama I wonder if we can close this now (is bcc5e6e the entire fix, or is there more to follow up here?)