So far the @NotNull annotation can be applied to pretty much any element. And it is an inspection error to assign an element of type @Nullable (or maybe unknown type, see http://www.jetbrains.net/jira/browse/IDEA-2087 ). But what about the situation where we assign a value to a variable where the assignment doesn't come from a method return value, a field or a local variable? void doTest() { // We have flagged the collection, but not its contents @NotNull Collection<String> c = new ArrayList<String> (); c.add ("Test"); c.add (null); // Oops // How can we be sure that all the elements of c are not null? for (@NotNull String s : c) { // Not flagged doTest2 (s); } } void doTest2 (@NotNull String s) { // Not flagged, and I don't test for null if (s.equals ("Test")) { // ... } } Do we maybe need a subsidiary annotation, something like @IteratorNeverReturnsNullInAnyCaseWhatsoever (or maybe something a bit shorter ? OK, this isn't really a bug, but I was just playing around and I thought I would submit this case for consideration.