Using a @NonNull value where nullness checker expects @Nullable is sometimes an error

[AlexLloyd0]

I'm trying to pass a @NonNull value where the nullness checker expects @Nullable. This seems safe to me but I get an error.

commands: checker-framework-3.19.0/checker/bin/javac -processor nullness NullnessCheckerDemo.java

inputs:
NullnessCheckerDemo.java:

package com.google.nullnesscheckerdemo;

import java.util.Optional;

final class NullnessCheckerDemo {
  private static <T extends Object> Optional<T> demo(Optional<Container<T>> maybeContainer) {
    return Optional.<T>empty().or(() -> maybeContainer.map(container -> container.element));
  }

  class Container<T extends Object> {
    public final T element;

    Container(T element) {
      this.element = element;
    }
  }
}

Removing any one of the generic, the container or the Optional make the test pass.

outputs:

NullnessCheckerDemo.java:7: error: [return] incompatible types in return.
    return Optional.<T>empty().or(() -> maybeContainer.map(container -> container.element));
                                                                                 ^
  type of expression: T extends @Initialized @NonNull Object
  method return type: T extends @Initialized @Nullable Object
1 error

expectation:
no error

[smillst]

This was fixed with #979.