Nullability is weird

The current nullability annotations are weird and make use of the library clunky.

Exhibit a:

Validator.Check()
  .That(someValue).IsNotNull()!.IsNotEmpty()
  .ElseThrow();

Exhibit b:

Validator.Check()
  .That(someValue)!.IsNotEmpty().When(someValue != null)
  .ElseThrow();

I'd prefer not having to resort to the ! operator.