Null-value constraints in Java code, plugin

Hi, I've been working on a way to use non-null types in Java 5.0 using annotations.
This is being implemented partly as an IDEA plugin. I thought some of you
might be interested in its development and I recently gave a presentation
to my college's research group, so I'll post the slides that I made for that
presentation: http://kano.net/in/NullnessPresentationApril6.pdf

An example of code using this functionality is:

String maybeNull() { return null; }

void x() {
@NonNull String s = maybeNull(); // error
String p = "";
@NonNull String r = p; // safe
}

@NonNull String notNullBad() {
return maybeNull(); // error
}

@NonNull String notNull() {
return ""; // safe
}

void noNullParams(@NonNull String s) { }

void y() {
@NonNull String s = notNull(); // safe
noNullParams(null); // error
noNullParams(notNull()); // safe
noNullParams(""); // safe
}

Everywhere marked with "// error" produces a red underline in the editor,
and will produce errors at compile time.

I don't have a usable version of the plugin to release yet (currently it
has some huge memory leak that prevents use for more than a few minutes),
but I'll be releasing something soon.