When APIs are generified using concrete instantiations of generic types, but
clients continue to use (now redundenat) casts in their code, javac elides
both the automatically-generated cast and the redudnant one, resulting in
unverifiable code.

here is a simplified test case:

import java.util.*;

class Z2 {
    protected Vector<String> v = null;

    public void f() {
        ((String) (v.elementAt(0))).charAt(0);
    }

    public static void main(String[] args) {}
}