State more clearly the restriction on multi-level optionals

[claymcleod]

The spec says

It is impossible to have a multi-level optional type, e.g., Int??. The outputs of a conditional are only ever single-level optionals, even when there are nested conditionals.

This should be pointed out more clearly in the optional types section.

[patmagee]

Is a non primitive construct considered multi-level? While you cannot have Int?? (Which I agree is silly), you can have Array[Array[String?]?]?

[claymcleod]

No, this would not be considered a multi-level optional because each ? applies to a different structural level of the type. The restriction on Int?? prevents multiple levels of optionality on the same value, not nested optionals within composite types.