Confusion/trying to understand CTFE keywords

[Gopan]

On Tuesday, 5 June 2018 at 22:08:32 UTC, Stefan Koch wrote:
> On Tuesday, 5 June 2018 at 18:00:05 UTC, Steven Schveighoffer 
> wrote:
>
>> No, it's definitely a bug. main is not being evaluated at 
>> compile time. The real result of this function should be a 
>> compile-time error -- __ctfe is a *runtime* value that is 
>> always defined based on whether you are __ctfe or not. 
>> Therefore, n must be a runtime value, and not usable as a 
>> static array dimension.
>>
>> If the posted code is valid, then this should be valid as well:
>>
>> static if(__ctfe)
>>    immutable n = 1;
>> else
>>    immutable n = 2;
>>
>> But it's not.
>>
>> -Steve
>
> I see what you mean.
> I fear fixing this bug will not be easy without breaking 
> arguably valid uses.

Will it be feasible something like

int n = CTFE(foo(3)); //dont limit CTFE to enum or immutable, 
etc.  You are calling explicitly.
int[n] arr;

So that, we can be explicit about when CTFE kicks in.  In that 
case, don't assign value to n at runtime as it has been 
initialized at compile time.  This way, we can get rid of the 
intermediate enums which are introduced just for the sake of 
inviting CTFE.  Also, this way, it will not silently break 
existing code; instead a compilation error must be thrown "value 
of n not known at compile time" for the below code.

immutable n = foo();
int[n] arr;

Unless called throgh CTFE(....), dont go for CTFE.

Will this work?

Just putting my thoughts... I am no expert.