[simias]

In my experience most of the time I had to use unsafe was to bind unsafe interface (think something like making raw OpenGL bindings for instance, you'll have unsafe code all over the place and you'll have write your own safe wrappers around it). Performance-wise I very rarely find myself having to compromise, although there are times where I have to write "smarter", more complicated code to get good performance without unsafe.

I just looked at the code of a pretty heavily optimized program I've been working on for a few months, I have exactly one instance of unsafe in the code:

   pub const GPIO_ID: StreamId = StreamId(unsafe { NonZeroU16::new_unchecked(0xf610) });

I need the unsafe because at the moment the language is not smart enough to understand that 0xf610 is obviously non-zero and that I can build a NonZeroU16 from it without fail (at least I don't know how to express this in static expression at the moment). This has no performance implications whatsoever.