Why this code can't take advantage from CTFE?

[Andrea Fontana via Digitalmars-d-learn]

On Wednesday, 3 February 2016 at 17:49:39 UTC, Marc Schütz wrote:
> On Wednesday, 3 February 2016 at 16:07:59 UTC, Messenger wrote:
>> What is a good way to try to force it? Using enum? Then 
>> optionally copying the value once to avoid the "manifest 
>> constant" copy/paste behaviour, where applicable?
>
> template forceCTFE(alias expr) {
>     alias forceCTFE = expr;
> }
>
> auto value = forceCTFE!(some_expression());

Interesting :)
Thank you!