Why this code can't take advantage from CTFE?

[Timon Gehr via Digitalmars-d-learn]

On 02/03/2016 11:39 PM, Andrea Fontana wrote:
> 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!

I would use enum forceCTFE(alias expr)=expr; though. With alias it won't 
force compile-time evaluation of expressions that can be interpreted as 
symbols.