On Friday, 8 December 2017 at 01:30:13 UTC, Manu wrote:

I tried this, and was surprised it didn't work:

int ctfeOnly(int x)
{
static assert(__ctfe);
return x + 1;
}

This would probably solve the problem in a satisfying way without an attribute?

I think that's because __ctfe, despite being magic, is actually a regular variable.

While this looks not too inelegant for a user perspective, I dont know how to handle this from a compiler perspective: filtering by attribute is as easy as "does this function have a UDA ctfeonly? If so, don't code generate it. Generating errors at codegen time is also trivial: when generating a call check to see if the callee is @ctfeonly, if it is give an error message

I don't know how to do that for a `static assert(__ctfe);`. That would require changes and semantic analysis in the front end which I am much less familiar with.