Ok... fixed.  I just submitted a change which has it generate this:

```
        public bool TestPrimitiveInOut(ref int i)
        {
            int _i = i; // FIX!
            var arg0 = &_i;
            var __ret = Internal.TestPrimitiveInOut_0(__Instance, arg0);
            i = _i;
            return __ret;
        }
```