xor method
Returns a Some if either, but not both, of this
and other
is a Some, or None
otherwise.
Examples
// prints "None"
print(const Some(2).xor(const Some(3)));
// prints "Some(2)";
print(const Some(2).xor(const None()));
Implementation
@override
@useResult
Option<T> xor(Option<T> other) => other is None ? this : None<T>();