Enum template with mixin, need 'this'

[Meta via Digitalmars-d-learn]

On Wednesday, 24 December 2014 at 17:41:09 UTC, ketmar via 
Digitalmars-d-learn wrote:
> On Wed, 24 Dec 2014 17:05:45 +0000
> Meta via Digitalmars-d-learn 
> <digitalmars-d-learn at puremagic.com> wrote:
>
>> So `if (isSet!bit1)` becomes `if (cast(bool)(embeddedTest.bits 
>> & bit1)`. That doesn't work, however. I get an error message 
>> saying "need 'this' for 'bits' of type 'int'". Is there a way 
>> to make this work, or am I stuck with the uglier mixin at the 
>> usage site?
>
> i don't think that you can cheat like this. ;-)
>
> templates aren't macros, and `mixin` inside the template works
> immediately. i.e. it's trying to *execute* the mixined code in
> compile time. so your template with `mixin` in it tries to check
> `embedded.bits` in *compile* time, and then complains about 
> missing
> 'this', as it should.
>
> i don't think that you can do c-like macros in D.

Hmm, I confused myself over when the expression is interpreted. I 
got it into my head that the template expansion would somehow 
delay interpretation of the expression so it could be picked up 
at runtime, but of course `enum` forces it to be CTFE'd.