Enum core_extensions::void::Void

pub enum Void {}

Type for impossible situations.

Use this as a type parameter to enums to make the variants that use it unconstructible.

This type is used in ResultLike to unwrap values that can only be either the ok or error variants of the type.

Interaction with unsafe code

It is only valid to convert to Void from other Void-like types, it is undefined behavior to convert from any constructible type,even if zero-sized.

Example,infallible FromStr implementation.

use std::str::FromStr;
use core_extensions::{SelfOps,ResultLike,Void};

#[derive(Debug,PartialEq)]
pub struct Double(pub String);
impl FromStr for Double{
    type Err=Void;
    fn from_str(s:&str)->Result<Self,Void>{
        s.repeat(2)
            .piped(Double)
            .piped(Ok)
    }
}

assert_eq!(
    "12345".parse::<Double>().unwrap_safe(),
    Double("12345".repeat(2))
);

Example,infinite loop which only returns on error.

use core_extensions::{ResultLike,Void};

#[derive(Debug,PartialEq)]
enum Error<T>{
    InvalidItem(T),
    IteratorWasntInfinite,
}
fn reading_numbers<I>(i:I)->Result<Void,Error<usize>>
where I:IntoIterator<Item=usize>
{
    for elem in i{
        if elem==0 { return Err(Error::InvalidItem(elem)) }
        println!("{}",elem);
    }
    Err(Error::IteratorWasntInfinite)
}

assert_eq!(reading_numbers(1..100).unwrap_err_safe() , Error::IteratorWasntInfinite);
assert_eq!(reading_numbers(0..).unwrap_err_safe() , Error::InvalidItem(0));

Methods

impl Void

pub fn to<T>(self) -> T

Converts a Void to any type.

Note that because Void is impossible to construct, this method is unreachable.

Trait Implementations

impl Copy for Void

impl<T: ?Sized> PartialOrd<T> for Void

fn partial_cmp(&self, _: &T) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]

default fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]

default fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]

default fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]

default fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: ?Sized> PartialEq<T> for Void

fn eq(&self, _: &T) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]

default fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl Eq for Void

impl Ord for Void

fn cmp(&self, _: &Self) -> Ordering

This method returns an Ordering between self and other.

default fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

default fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

default fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl Clone for Void

fn clone(&self) -> Void

Returns a copy of the value.

default fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Hash for Void

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given [Hasher].

default fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Display for Void

fn fmt(&self, _: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Debug for Void

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Serialize for Void

This impl is only enabled if the "serde_" feature is enabled.

fn serialize<S>(&self, _: S) -> Result<S::Ok, S::Error> where
    S: Serializer, 

Serialize this value into the given Serde serializer.

impl<'de> Deserialize<'de> for Void

This impl is only enabled if the "serde_" feature is enabled.

This always Returns an Err(D::Error::custom(DeserializeVoidError)).

fn deserialize<D>(_: D) -> Result<Self, D::Error> where
    D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.