typeerror if scanning List encounters a non-list. Note that memberchk/2 does not perform a full list typecheck. For example,
memberchk(a, [a|b])succeeds without error. If List is cyclic and Elem is not a member of List, memberchk/2 eventually raises a
typeerror.121Eventually here means it will scan as many elements as the longest list that may exist given the current stack usage before raising the exception.