Type Alias NonZeroI32

pub type NonZeroI32 = NonZero<i32>;

An integer that is known not to equal zero.

This enables some memory layout optimization. For example, Option<NonZeroI32> is the same size as i32:

use std::mem::size_of;
assert_eq!(size_of::<Option<core::num::NonZeroI32>>(), size_of::<i32>());

Layout

NonZeroI32 is guaranteed to have the same layout and bit validity as i32 with the exception that 0 is not a valid instance. Option<NonZeroI32> is guaranteed to be compatible with i32, including in FFI.

Thanks to the null pointer optimization, NonZeroI32 and Option<NonZeroI32> are guaranteed to have the same size and alignment:

use std::num::NonZeroI32;

assert_eq!(size_of::<NonZeroI32>(), size_of::<Option<NonZeroI32>>());
assert_eq!(align_of::<NonZeroI32>(), align_of::<Option<NonZeroI32>>());

Aliased Type

struct NonZeroI32(/* private fields */);