Checking if CTFE is used?

[Stefan Koch]

On Tuesday, 18 December 2018 at 12:21:44 UTC, berni wrote:
> Is there a way to check if a function is indeed executed at 
> compile time or not? (Other than going through the whole 
> executable binaries...)
>
> I tried
>
>> static this()
>> {
>>   if (__ctfe) pragma(msg,"works");
>>   // some other stuff
>> }
>
> but unfortunatley this "if" is also executed at compile time, 
> when I put it into a function that is only called at runtime. 
> When I try "static if" instead the compiler complains about 
> "__ctfe" being not known at compile time.

Why would you need to know?