code: List<Type> sigToTypes(char terminator) {
          List<Type> head = List.of(null);
          List<Type> tail = head;
          while (signature[sigp] != terminator)
              tail = tail.setTail(List.of(sigToType()));
          sigp++;
          return head.tail;
      }
docs: Convert (implicit) signature to list of types
  until `terminator' is encountered.