Cannot assign to generic fields with toIndex function

[peq]

    @Test
    public void genericToIndexBug2() {
        testAssertOkLines(true,
                "package test",
                "native testSuccess()",
                "class C<T>",
                "    T x",
                "function stringToIndex(string s) returns int",
                "    return 42",
                "function stringFromIndex(int i) returns string",
                "    return \"42\"",
                "init",
                "    C<string> c = new C<string>",
                "    c.x = \"42\"",                           // translation fails here
                "    if c.x == \"42\"",
                "        testSuccess()");

    }