type argument inference from method argument in named arg list

[gavinking]

The following example from the tour does not pass the typechecker:

shared interface Observable {
    shared void addObserver<Event>(void on(Event event)) { }
}

class UpdateEvent() {}

void add() {
    object observable satisfies Observable {}
    observable.addObserver((UpdateEvent e)
            print("Update:" + e.string));
    observable.addObserver {
        void on(UpdateEvent e) {
            print("Update:" + e.string);
        }
    };
}

[gavinking]

I'm rather happy to have snuck this improvement into M3 :-)