[speed_spread]

As long as the compiled code is just as efficient as it would be had it been built-in to the language, I don't see the issue? Bitfield ops are very low-level constructs that are only useful in very specific project types. Their portable usage can be tricky, it's not something a majority of coders should reach for.

That's the luxury of a standard build system: essential but rarely used features can be left out of the core language / lib because adding them back in is just a crate import away.