Java does; List<String> is not a subtype of List<Object>. This greatly confuses many programmers, since String[] is a subtype of Object[] (they made this mistak

Java does; List<String> is not a subtype of List<Object>. This greatly confuses many programmers, since String[] is a subtype of Object[] (they made this mistake before Guy Steele got involved). Naturally, SML does as well. SML also has immutable lists, which are covariant.