class Foo {
  __init__(arg) {
    print("Foo.__init__(" + arg + ")");
    this.field = "init";
  }
}

var foo = Foo("one"); # expect: Foo.__init__(one)
foo.field = "field";

var foo2 = foo.__init__("two"); # expect: Foo.__init__(two)
print(foo2); # expect: <Foo instance>

# Make sure __init__() doesn't create a fresh instance.
print(foo.field); # expect: init