typedef A[T] = (var T^ m);

var (bool x) b;

() f[T](A[T]^ a, A[T]^ b) {
    var A[(bool b)] nonpriv;

    /* ERRORS */
    a^.m^ = a^.m^;
    nonpriv.m^ = a^.m^;
    a^.m^ = nonpriv.m^;

}