[msoloviev]

This looks like a more mature/different approach to the same thing I tried to do in a side project a while ago (https://github.com/blackhole89/macros), down to similar aesthetic choices. However, I pitch my project as a macro system rather than compile-time execution.

While here the metalanguage is itself a C++-lookalike, in my project I wound up with something that is perhaps better described as a weird TeX (which seems to be what happens naturally when your machine model is based on binding and substitution).

On one hand, C++ is surely more powerful/expressive and there is elegance to having the language and metalanguage use the same idiom. On the other, I feel like this might actually making Circle a bit more confusing to use at times, as it becomes less clear exactly when what parts of the code are executed, and you could even imagine a typo accidentally lifting a part of the code from runtime to compile time, resulting in mystifying bugs. (I am myself puzzled by the "serialize structs generically" example: does it imply that the template is specialised before the @meta for is executed?)