https://issues.dlang.org/show_bug.cgi?id=21178

          Issue ID: 21178
           Summary: It is not explained what is "unknown"
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: minor
          Priority: P1
         Component: dlang.org
          Assignee: nobody@puremagic.com
          Reporter: porton@narod.ru

https://dlang.org/spec/enum.html

"An empty enum body (For example enum E;) signifies an opaque enum - the enum
members are unknown."

The specification is very unclear here:

What this "unknown" does mean? How does "unknown" differ from "none" in this context?

The specification does not define the meaning of unknown. Formal specifications should not use a word with no clear meaning.

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