Comptime also means that when endianness matches, using these functions is a no-op. I expect you know this, but those new to the language may not: the endianness check in the implementation happens when compiling, not when decoding structs.

It's instructive how different in feel this solution is to the traditional #ifdefs which the Fine Article dislikes enough to write an entire (IMHO very confused and opaque) broadside against. The preprocessor is a second language superimposed over the first, which is friction, and the author would rather trust the compiler (despite explicitly noting that MSVC cannot be so trusted!) to optimize out a non-obvious solution using shifts, rather than risk the bugs which come with preprocessor-driven conditional compilation.

By contrast, if you don't know Zig, it's not all that obvious that the little-to-little case is a no-op on little-endian systems. If you do know Zig it is obvious, and it's also boring, in a good way: idiomatic Zig code does a lot of small things at compile time, using, for the most part, the same language as runtime code.