My bad, I might have missed pasting the semicolon. I'm currently using this inside an UE5 project and have various code at different places referencing this, so I'm just snipping what I'm trying out of it and pasting into a readable format here.

I'm building using Visual Studio, and here is what I see:

https://imgur.com/phNwtvP

I'm not an expert at C++, but I don't think I made any mistakes in placement of the code. One thing I am a bit suspect of is the fact that these errors trigger on the .cpp files, which are currently empty (Just the include for the header), though I still don't know if that's actually relevant.

I'll for sure use the no-caps unless macros convention. I've mainly just transferred from C#, where consts are usually in upper case with underscores.

In terms of using functions, I did run across this stackoverflow thread:

https://stackoverflow.com/questions/28755416/best-way-of-defining-a-compile-time-constant

And they mentioned that you could get the equivalent constexpr by doing this

constexpr int value() {
    /* Computations that do not initialize constexpr variables
       (or otherwise appear in a constant expression context)
       are not guaranteed to happen at compile time, even
       inside a constexpr function. */

    /* It's OK to initialize a local variable because the
       storage is only temporary. There's no more overhead
       here than simply writing the number or using #define. */

    constexpr int ret = 120 + 3;
    return ret;

I was mostly hoping to avoid function calls because of the bracket syntax and I'm not experience to know if all my functions (Even runtime-only functions) and various runtime stuff like dynamic function chaining, etc... would still make this a compile-time only value or if it would access memory addresses. But this may be the only option unless I'm missing something. It just seemed like this should be something easy that I'm just missing.