The return value from an extension function may now be an implementation of
representing a sequence. The members of the
List must all implement
An argument to an extension function may now be the class
a subclass. If the supplied value is a sequence, the first node in the sequence is passed to the function;
it is an error if there is no node in the supplied sequence, or if the node is of the wrong type.
The rules for calling extension functions with a sequence-valued argument have been clarified, and
some new options are permitted, e.g. declaring the argument as
java.util.List. The possibilities
have not been extensively tested.