The following program crashes the runtime, even after 4979440 is fixed.

import java.lang.reflect.*;

class A<T> {
    class B<U> {}
}

class Main {
    public void f(A<String>.B<Integer> x) {
    }

    public static void main(String[] args) throws Exception {
        Method m = Main.class.getMethod("f", A.B.class);
        Type param = m.getGenericParameterTypes()[0];
        System.out.println(param.toString());
    }
}