sclass MatchableRecords<A extends IFieldsToList> {
  new L<A> records;
  
  *() {}
  *(A... records) { addAll(this.records, records); }
  
  O fulfillVariable(IF1<Var, A> makeRecord) {
    new Var var;
    O result = null;
    A record = makeRecord.get(var);
    O[] a = record._fieldsToList();
    bigLoop: for (A r : records) {
      if (r.getClass() != record.getClass()) continue;
      O[] b = r._fieldsToList();
      if (b.length != a.length) fail("Bad argument length: " + record);
      for i over a:
        if (a[i] == var) {
          if (result != null && !eq(result, b[i]))
            continue bigLoop;
          result = b[i];
        } else
          if (!eq(a[i], b[i]))
            continue bigLoop;
            
      ret result;
    }
    null;
  }
}