`augmented()` can't occur in an initializer list of an augmenting constructor declaration, right?

[eernstg]

Surely it would violate some invariants that we can otherwise rely on if augmented() is allowed to be executed in the initializer list of a non-redirecting, or in the redirection of a redirecting generative constructor. (In short: general code gets to see an object which is not initialized.)

However, I can't find an explicit indication in the feature specification that there must be such an error. Here is an example. Currently (ac9b6d1672255d2233ed612eb9c94921dca3cd3a), the analyzer does not report any errors.

class A {
  dynamic x;
  A() {
    print('Running introductory!');
  }
  augment A(): x = augmented();
}

class B {
  B(Object? o);
  B.named(): this(42);
  augment B.named(): this(augmented());
}

I think we must specify a compile-time error for both of these situations, because the initializer list / redirection does not have access to this, but the body of an augmented generative constructor can access this.

Of course, we could also allow both of them, and consider augmented to be a regular identifier in both situations, potentially resolving to a static, top-level, or imported declaration. We'd then have an error if augmented() in that context resolves to an instance member of the enclosing class/enum/extension-type, because the initializer list / redirection does not have access to this.

@dart-lang/language-team, WDYT?