Enum fallible_option::Fallible

pub enum Fallible<E> {
    Success,
    Fail(E),
}

Outcome of an operation that does not produce a value on success.

Variants

Success

No error was produced.

Fail(E)

An error was produced.

Implementations

impl<E> Fallible<E>

pub const fn as_deref(&self) -> Fallible<&<E as Deref>::Target>where
    E: Deref,

Converts from Fallible<E> (or &Fallible<E>) to Fallible<&E::Target>.

Leaves the original Fallible in-place, creating a new one with a reference to the original one, additionally coercing the contents via Deref.

let fail: Fallible<String> = Fail("something went wrong".to_owned());
assert_eq!(fail.as_deref(), Fail("something went wrong"))

pub const fn as_deref_mut(&mut self) -> Fallible<&mut <E as Deref>::Target>where
    E: DerefMut,

Converts from Fallible<E> (or &mut Fallible<E>) to Fallible<&mut E::Target>

Leaves the original Fallible in-place, creating a new one containing a mutable reference to the inner type’s Deref::Target type.

let mut fail = Fail("uh oh!".to_owned());

fail.as_deref_mut().map(|err| {
    err.make_ascii_uppercase();
    err
});

assert_eq!(fail, Fail("UH OH!".to_owned()));

pub const fn as_mut(&mut self) -> Fallible<&mut E>

Converts from &mut Fallible<E> to Fallible<&mut E>

let mut fail = Fail("uh oh!".to_owned());
match fail.as_mut() {
    Fail(err) => err.make_ascii_uppercase(),
    Success => {}
}

assert_eq!(fail, Fail("UH OH!".to_owned()))

pub const fn as_ref(&self) -> Fallible<&E>

Converts from &Fallible<E> to Fallible<&E>

let fail = Fail("uh oh!");
let err_length = fail.as_ref().map(|err| err.len());

assert_eq!(err_length, Fail(6));

pub const fn is_successful(&self) -> bool

Returns true if the value is a Success, otherwise false.

assert_eq!(Fail("some error").is_successful(), false);
assert_eq!(Success::<&str>.is_successful(), true)

pub const fn is_fail(&self) -> bool

Returns true if the value is a Fail, otherwise false.

assert_eq!(Fail("some error").is_fail(), true);
assert_eq!(Success::<&str>.is_fail(), false)

pub fn unwrap_fail(self) -> E

Unwrap the contained error or panics if no error has occurred.

let fail = Fail(70);
assert_eq!(fail.unwrap_fail(), 70);

let fail: Fallible<u32> = Success;
assert_eq!(fail.unwrap_fail(), 70);

pub const fn contains<U: PartialEq<E>>(&self, x: &U) -> bool

Returns true if the Fallible is a Fail value containing an error equivalent to f

let fail = Fail("hello".to_owned());
assert!(fail.contains(&"hello"))

pub const fn map<F, U>(self, op: F) -> Fallible<U>where
    F: FnOnce(E) -> U,

Maps an Fallible<E> to Fallible<U> by applying a function to the contained error.

let fail = Fail("hello");
let fail = fail.map(|err| format!("{err} world!"));

assert_eq!(fail, Fail("hello world!".to_owned()));

pub const fn result(self) -> Result<(), E>

Transforms the Fallible<E> into a Result<(), E>, where Fail(e) becomes Err(e) and Success becomes Ok(())

let fail = Fail("error").result();

assert_eq!(fail, Err("error"));

pub const fn err(&self) -> Option<&E>

Borrows the Fallible<E> as an Option<E>, yielding none if no error occurred.

let fail = Fail("error occurred");
let maybe_error = fail.err();

assert_eq!(maybe_error, Some(&"error occurred"));

pub const fn err_or<T>(self, value: T) -> Result<T, E>

Constructs a Result<T, E> from self.

let fail: Result<u32, &str> = Fail("some error").err_or(10);

assert_eq!(fail, Err("some error"));

Fail(e) becomes Err(e) and Success becomes Ok(value)

pub const fn take(&mut self) -> Option<E>

Replaces the contained error (if any) with None, and returns an Option<E> with the contained error, if the outcome was Fail.

let mut fail = Fail("something went wrong");

let err = fail.take();

assert_eq!(fail, Success);
assert_eq!(err, Some("something went wrong"));

impl<E> Fallible<&E>where
    E: Clone,

pub const fn cloned(self) -> Fallible<E>

Maps a Fallible<&E> to a Fallible<E> by cloning the contents of the error.

pub const fn copied(self) -> Fallible<E>where
    E: Copy,

Maps an Fallible<&E> to an Fallible<E> by copying the contents of the error.

impl<E> Fallible<&mut E>where
    E: Clone,

pub const fn cloned(self) -> Fallible<E>

Maps an Fallible<&E> to an Fallible<E> by cloning the contents of the error.

pub const fn copied(self) -> Fallible<E>where
    E: Copy,

Maps an Fallible<&E> to an Fallible<E> by copying the contents of the error.

impl<E> Fallible<E>where
    E: Debug,

The following functions are only available if the generic parameter E implements Debug

pub fn unwrap(self)

Returns a unit value if the Fallible is not Fail.

Panics

Panics if the value is a Fail, with a panic message including the content of the Fail.

let success: Fallible<()> = Success;
success.unwrap();

let fail = Fail("hello world");
fail.unwrap();

impl<E> Fallible<Fallible<E>>

pub const fn flatten(self) -> Fallible<E>

Flattens a Fallible<Fallible<E>> into a Fallible<E>

Trait Implementations

impl<E> Clone for Fallible<E>where
    E: Clone,

const fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<E: Debug> Debug for Fallible<E>

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

Formats the value using the given formatter.

impl<E> Default for Fallible<E>

const fn default() -> Self

Returns the “default value” for a type.

impl<'a, E> From<&'a Fallible<E>> for Fallible<&'a E>

const fn from(value: &'a Fallible<E>) -> Self

Converts to this type from the input type.

impl<'a, E> From<&'a mut Fallible<E>> for Fallible<&'a mut E>

const fn from(value: &'a mut Fallible<E>) -> Self

Converts to this type from the input type.

impl<E> From<E> for Fallible<E>

const fn from(value: E) -> Self

Converts to this type from the input type.

impl<T, E> From<Result<T, E>> for Fallible<E>

const fn from(value: Result<T, E>) -> Self

Converts to this type from the input type.

impl<E, U> FromResidual<Fallible<U>> for Fallible<E>where
    E: From<U>,

fn from_residual(residual: Fallible<U>) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<T, E, U> FromResidual<Fallible<U>> for Result<T, E>where
    E: From<U>,

fn from_residual(residual: Fallible<U>) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<E, U> FromResidual<Result<(), U>> for Fallible<E>where
    E: From<U>,

fn from_residual(residual: Result<(), U>) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<E, U> FromResidual<Result<Infallible, U>> for Fallible<E>where
    E: From<U>,

fn from_residual(residual: Result<Infallible, U>) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<E: Hash> Hash for Fallible<E>

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<E: Ord> Ord for Fallible<E>

fn cmp(&self, other: &Fallible<E>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl<E: PartialEq> PartialEq<Fallible<E>> for Fallible<E>

fn eq(&self, other: &Fallible<E>) -> bool

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

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<E: PartialOrd> PartialOrd<Fallible<E>> for Fallible<E>

fn partial_cmp(&self, other: &Fallible<E>) -> Option<Ordering>

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

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

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

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

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

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

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

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<E> Try for Fallible<E>

type Output = ()

🔬This is a nightly-only experimental API. (try_trait_v2)

The type of the value produced by ? when not short-circuiting.

type Residual = Fallible<E>

🔬This is a nightly-only experimental API. (try_trait_v2)

The type of the value passed to FromResidual::from_residual as part of ? when short-circuiting.

fn from_output(_: Self::Output) -> Self

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from its Output type.

fn branch(self) -> ControlFlow<Self::Residual, Self::Output>

🔬This is a nightly-only experimental API. (try_trait_v2)

Used in ? to decide whether the operator should produce a value (because this returned ControlFlow::Continue) or propagate a value back to the caller (because this returned ControlFlow::Break).

impl<E: Copy> Copy for Fallible<E>

impl<E: Eq> Eq for Fallible<E>

impl<E> StructuralEq for Fallible<E>

impl<E> StructuralPartialEq for Fallible<E>