MODULE TFwdSet;
// SET OF a type declared later in the same TYPE block (forward type
// reference): the span check is deferred until the block completes.
// Exit 42.
TYPE myset = SET OF colour;
     colour = (red, green, blue);
VAR s : myset; ExitCode : INTEGER;
BEGIN
  s := myset{red};
  IF (red IN s) AND NOT (green IN s) THEN ExitCode := 42 ELSE ExitCode := 1 END
END TFwdSet.