An i16 that is known not to equal zero.

This enables some memory layout optimization. For example, Option<NonZeroI16> is the same size as i16:

assert_eq!(size_of::<Option<core::num::NonZeroI16>>(), size_of::<i16>());

Layout

NonZeroI16 is guaranteed to have the same layout and bit validity as i16 with the exception that 0 is not a valid instance. Option<NonZeroI16> is guaranteed to be compatible with i16, including in FFI.

Thanks to the null pointer optimization, NonZeroI16 and Option<NonZeroI16> are guaranteed to have the same size and alignment:

use std::num::NonZeroI16;

assert_eq!(size_of::<NonZeroI16>(), size_of::<Option<NonZeroI16>>());
assert_eq!(align_of::<NonZeroI16>(), align_of::<Option<NonZeroI16>>());

Compile-time creation

Since both [Option::unwrap()] and [Option::expect()] are const, it is possible to define a new NonZeroI16 at compile time via:

use std::num::NonZeroI16;

const TEN: NonZeroI16 = NonZeroI16::new(10).expect("ten is non-zero");