Cycle reference to union types generate dynamic types

[spideythewebhead]

Example

@Union()
class MyUnion {
  const factory MyUnion.a({
    required A a,
  }) = A;
}

Generates

class A extends MyUnion {
  ...
  final dynamic a; // should be => final A a;
}

This happens because class A doesn't exist before code generation, so the analyzer marks this as a dynamic instance.

Possible solution: Traverse the Node AST and extract the name of the type.

Needs investigation.