> A method that returns Optional<T> may return null.

projects that do this drive me bananas

If I had the emotional energy, I'd open a JEP for a new @java.lang.NonNullReference and any type annotated with it would be a compiler error to assign null to it

  public interface Alpha {}
  @java.lang.NonNullReference
  public interface Beta {}

  Alpha a = null; // ok
  Beta b = null; // compiler error

javac will tolerate this

  Beta b;
  if (Random.randBoolean()) {
    b = getBeta();
  } else {
    b = newBeta();
  }

but I would need to squint at the language specification to see if dead code elimination is a nicety or a formality

  Beta b;
  if (true) {
    b = getBeta();
  } else {
    b = null; // I believe this will be elided and thus technically legal
  }