Wildcards aren't captured for inner classes that use type parameters from the outer class

[cushon]

abstract class CaptureOuter<T> {
  abstract T get();

  abstract class Inner {
    abstract T get();
  }
}

class Client {
  Object getFrom(CaptureOuter<?> o) {
    return o.get();
  }

  Object getFrom(CaptureOuter<?>.Inner o) {
    return o.get();
  }
}

$ $HOME/checker-framework-3.21.0/checker/bin/javac -processor nullness CaptureOuter.java
CaptureOuter.java:11: error: [return] incompatible types in return.
    return o.get();
                ^
  type of expression: capture#84 extends @Initialized @Nullable Object
  method return type: @Initialized @NonNull Object
CaptureOuter.java:15: error: [return] incompatible types in return.
    return o.get();
                ^
  type of expression: @Initialized ? extends @Initialized @Nullable Object
  method return type: @Initialized @NonNull Object
2 errors

The call to CaptureOuter.get() has a type of capture#84 extends @Initialized @Nullable Object, as expected.

But the call to CaptureOuter.Inner.get() has a type of @Initialized ? extends @Initialized @Nullable Object.

Contrast this to what javac does if the return types of the getFrom methods is changed to String: In both cases, it identifies the call as having a type of CAP#1.