define open abstract class <diagnostic> (<condition>)
  constant class slot class-code :: <string>,
    required-init-keyword: class-code:;

  constant each-subclass slot subclass-code :: <string> = "000",
    init-keyword: subclass-code:;

  constant slot condition-number :: <integer> = 1,
    init-keyword: condition-number:;

  constant slot possible-explanation :: <deque> = make(<deque>);
end class;

...

define open class <ambiguous-cursor-name> (<diagnostic>)
  keyword class-code: = "3C";
end class;

-----------------------------------------

In Define Class <ambiguous-cursor-name>:
unknown source locationError: The type in the initialization argument specification for keyword class-code: in class <ambiguous-cursor-name> must be a subtype of the corresponding type specification in class <diagnostic>