There's a new and improved CTFE coming to D, with performance optimizations: "At 5 times the speed. While using 40% the memory."

https://forum.dlang.org/post/btozyjtvogxgfejiwunr@forum.dlang.org

Compile Time Function Evaluation. That's pretty meta. Does it compile the compile-time runtime, so that there is a compile-time compile-time? Can you run CTFE there? :-D

If you're less lazy than me, the answer is probably here:

https://tour.dlang.org/tour/en/gems/compile-time-function-evaluation-ctfe