Generics and named constructors

[vsmenon]

We appear to generate invalid code for named constructors with generic types:

class A<T> {
  A.named() {
    init();
  }

  init() {
    print('hello');
  }
}

main() {
  new A<int>.named();
}

results in this error when the named constructor is executed:
"Uncaught TypeError: this.init is not a function"

[vsmenon]

@jmesserly helped me track this down to precedence.

We're generating:

new A$(core.int).named();

We should be generating:

new (A$(core.int).named)();

[vsmenon]

This is somewhat related to / muddled by #162.
E.g., this surprisingly seems to work today:

  new core.Map$(core.String, core.String).from(oldmap);

but it is actually creating an empty Map via the default constructor and calling from as an instance method on it.

[jmesserly]

yeah, that's the same bug

[jmesserly]

https://codereview.chromium.org/1122283002/