Using output-range overloads of SysTime.toISO{Ext}String with formatting code

[Mitacha]

On Monday, 8 July 2019 at 12:53:18 UTC, Digital Mars wrote:
> 08.07.2019 13:38, Joseph Rushton Wakeling пишет:
>> [...]
> Sorry that my answer wasn't thoughtful.
>
> I guess that there is no way to have `writeln` automatically 
> use the output range overload instead of allocating one. You 
> need somehow to provide the output range to `toISOExtString` 
> explicitly because `writeln` outputs the return of 
> `toISOExtString` and have no ability to use specific overload. 
> That is compiler calls `toISOExtString` and then passes its 
> return to `writeln`. Probably library solution isn't possible 
> in this case. Workaround is using own wrapper to provide output 
> range to `toISOExtString`.

I've managed to make it work using 'alias this' and wrapper 
struct.
https://run.dlang.io/is/3SMEFZ
It's not an elegant solution, there could be a better way to do 
this.