Error about constructor calls in loops/labels, but there are no loops and labels?

[DarkHole]

On Thursday, 17 May 2018 at 20:02:19 UTC, Steven Schveighoffer 
wrote:
> On 5/17/18 3:55 PM, DarkHole wrote:
>> This strange code - https://run.dlang.io/is/BKgv49 - fails 
>> with error "Error: constructor calls not allowed in loops or 
>> after labels", but there is no loops or labels.
>
> Switch cases are labels.
>
> -Steve

But why?