addListener method
Implementation
void addListener(Type t, NopListener listener) {
t = getAlias(t);
assert(!_pointers.containsKey(t), t);
_pointers[t] = listener;
}
void addListener(Type t, NopListener listener) {
t = getAlias(t);
assert(!_pointers.containsKey(t), t);
_pointers[t] = listener;
}