In AbstractText/eneyj, the type of the Z23 “nothing” object is Z23, i.e. itself. This causes issues in GraalEneyj, because an object isn’t allowed to be a “meta-object” (a type) and “null” at the same time. In the current GraalEneyj commit for meta-objects, I’ve resolved this by pretending the type of Z23 is Z4/type instead of Z23. WikiLambda doesn’t have a Z23 “nothing” object yet, but when it does, I suggest its type should not be Z23, to avoid that issue.
Description
Description
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| In Progress | DMartin-WMF | T285433 Replace Z23s with Z21s (instances of Z24) in Orchestrator and Validator | |||
| Resolved | DVrandecic | T276721 ZObject model: Don’t make Z23/nothing’s Z1K1/type itself |
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You are right, that's actually wrong - Z23 really should be a Z4. Z23 shouldn't have any instance, not even itself. I will keep it open until the nothing type is created.
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In Scala, there is a "Nothing" type that have no instances and a "Nil" type that have one instance. In some case we need to differ a bottom type and a actual null value (such as that in Java).