How do I check if a function got CTFE?

[Adam D. Ruppe via Digitalmars-d-learn]

On Thursday, 2 October 2014 at 17:56:29 UTC, AsmMan wrote:
> I'd like to check if a function got CTFE, ie, the compiler was 
> able to replace my foo(s); by the computed value at 
> compile-time.

You have to explicitly force ctfe with context, it is never done 
automatically, and if it fails, the build will fail and you get a 
compile time error.

So if you write

enum f = foo();

or

static f = foo();

or similar initializations and the build succeeds, you know it 
got ctfe'd. Otherwise, it wasn't.