In this case,
class TestOne<T> { // TestN.class
     Object mtest( TestOne<T> t){ return null; }

    public void test() {
        mtest( new TestOne<T>() { // TestN$1
                class InnerAnon<U> { // TestN$1$InnerAnon.class
                    @F String ia_m1(){ return null; };
                }
                InnerAnon<String> IA = new InnerAnon< String>();
           });
   }
}
@Retention(RUNTIME) @Target(TYPE_USE) @interface F { }

@F is written to class file as a regular annotation on ia_m1().