Trait Niche 

pub trait Niche: Sized {
    type Output;

    // Required methods
    fn none() -> Self::Output;
    fn is_none(value: &Self::Output) -> bool;
    fn into_some(value: Self) -> Self::Output;
    fn from_some(value: Self::Output) -> Self;
}

A type should implement Niche if its memory representation has any bit patterns that do not represent valid values. If so, one of those can be used to represent the None case of an option.

Required Associated Types

type Output

The type that is used to store values of Self inside of a ControlledOption. This might be Self itself, if your niche is a valid instance of the type, but which violates some runtime constraint. But if you cannot easily create your niche as an instance of Self, you can use some other type, you can use some other type instead.

A word of caution: is it this Output type that is stored inside of a ControlledOption. If you want ControlledOption<Self> to have the same memory layout as Self (so that you can use #[repr(transparent)], for instance), then you must ensure that Self and Output have the same layout, as determined by std::alloc::Layout::new, and that every valid bit pattern for Self is be a valid bit pattern for Output that returns true for is_some.

Required Methods

fn none() -> Self::Output

Returns the niche value for this type that should be used to represent None for a ControlledOption.

fn is_none(value: &Self::Output) -> bool

Returns whether value is the niche value for this type.

fn into_some(value: Self) -> Self::Output

Transforms a non-niche value of this type into its Output type. When Output is Self, this will be the identity function.

fn from_some(value: Self::Output) -> Self

Transforms a non-niche value of this type from its Output type. When Output is Self, this will be the identity function.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Niche for NonZeroI8

type Output = i8

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroI16

type Output = i16

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroI32

type Output = i32

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroI64

type Output = i64

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroIsize

type Output = isize

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroU8

type Output = u8

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroU16

type Output = u16

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroU32

type Output = u32

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroU64

type Output = u64

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl Niche for NonZeroUsize

type Output = usize

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl<'a, T> Niche for &'a T

type Output = *const T

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

impl<'a, T> Niche for &'a mut T

type Output = *mut T

fn none() -> Self::Output

fn is_none(value: &Self::Output) -> bool

fn into_some(value: Self) -> Self::Output

fn from_some(value: Self::Output) -> Self

Implementors