TypeAdapterRuntimeTypeWrapper prefers cyclic adapter for base type over reflective adapter for sub type

[Marcono1234]

The internal class TypeAdapterRuntimeTypeWrapper is supposed to prefer custom adapters for the compile type over the reflective adapter for the runtime type. However, when the compile type and the runtime type only have a reflective adapter, then it should prefer the runtime type adapter.

The problem is that this logic is not working for classes with cyclic dependencies which therefore have a Gson$FutureTypeAdapter wrapping a reflective adapter because the following line does not consider this:

gson/gson/src/main/java/com/google/gson/internal/bind/TypeAdapterRuntimeTypeWrapper.java

Line 60 in ceae88b

} else if (!(delegate instanceof ReflectiveTypeAdapterFactory.Adapter)) {

For example:

class Base {
  public Base f;
}

class Sub extends Base {
  public int i;

  public Sub(int i) {
    this.i = i;
  }
}

Base b = new Base();
b.f = new Sub(2);
String json = new Gson().toJson(b);
// Fails because reflective adapter for base class is used, therefore json is: {"f":{}}
assertEquals("{\"f\":{\"i\":2}}", json);

Note: This is similar to the problem #1787 tries to fix for TreeTypeAdapter.