alias restriction??!

[Carl Sturtivant]

On Sunday, 19 July 2020 at 12:08:07 UTC, Paul Backus wrote:
> On Saturday, 18 July 2020 at 18:46:16 UTC, Carl Sturtivant 
> wrote:
>> Here's a toy version of a problem in the wild.
>>
>> struct S {
>>     long first;
>>     union T {
>>         long one;
>>         double two;
>>     }
>>     T second;
>>     alias First = first;
>>     alias Second = second.one;
>> }
>>
>> void main() {
>>     S x;
>>     x.First = 4;
>>     x.Second = 5; // compilation error: "Error: need this for 
>> one of type long"
>> }
>
> Easiest workaround:
>
> ref inout(long) Second() inout { return second.one; }

Was trying to avoid this for performance reasons. In fact what 
are the performance implications of this sort of thing with 
current implementations? --- relative to using a simple offset.