Fails to cast to a generic type and use generic types with v1

[poirierlouis]

I'm having an issue when using generics with the latest preview of redscript v1.

private abstract class State {}
private class WindowState extends State {}
private class TextState extends State {}

// Issue
public func Request<T extends State>(id: Uint64) -> ref<T> {
  let state: ref<T>;
  let type = NameOf<T>();

  switch type {
    case NameOf<WindowState>():
      let window = this.FindState<WindowState>() as WindowState;
      if !IsDefined(window) {
        window = WindowState.Create(id);
      }
      state = window; // type mismatch: found `WindowState` when expected `T`
      break;
  }

  return state;
}

// Workaround
public func Request<T extends State>(id: Uint64) -> ref<T> {
  let state: Variant;
  let type = NameOf<T>();

  switch type {
    case NameOf<WindowState>():
      let window = this.FindState<WindowState>() as WindowState;
      if !IsDefined(window) {
        window = WindowState.Create(id);
      }
      state = window;
      break;
  }

  return FromVariant(state);
}

Additionally, switch-case could be avoided/simplified, though it also requires ToVariant/FromVariant tricks.

If I do:

  // ...
  let state = this.FindState<T>(id); // type mismatch: found `T` when expected `State`
  // ...
}

public func FindState<T extends State>(id: Uint64) -> ref<T> {
  if this.m_flatTree.KeyExist(id) {
    let state: ref<State> = this.m_flatTree.Get(id) as State; // from wref<IScriptable> to wref<State> to ref<State>
    // ...
    return state; // type mismatch: found `State` when expected `T`
  }

  return null;
}

If I try directly with:

    //private let m_flatTree: ref<inkHashMap>;

    let state: ref<T> = this.m_flatTree.Get(id) as T; // this type cannot be usedd with the `as` operator, the target type must be a class

Some of the issues before seems legit, but imo this last line should be working in order to be useful for methods above. Is this diagnosis error expected?