# Error in rand - Rust
Error type of random number generators
Keywords: rust, rustlang, rust-lang, Error

# Struct rand::Error

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    pub struct Error { /* private fields */ }

Expand description

Error type of random number generators

In order to be compatible with `std` and `no_std`, this type has two possible implementations: with `std` a boxed `Error` trait object is stored, while with `no_std` we merely store an error code.

## Implementations

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### impl Error

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#### pub const CUSTOM_START: u32 = 3_221_225_472u32

Codes at or above this point can be used by users to define their own custom errors.

This has a fixed value of `(1 << 31) + (1 << 30) = 0xC000_0000`, therefore the number of values available for custom codes is `1 << 30`.

This is identical to `getrandom::Error::CUSTOM_START`.

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#### pub const INTERNAL_START: u32 = 2_147_483_648u32

Codes below this point represent OS Errors (i.e. positive i32 values). Codes at or above this point, but below `Error::CUSTOM_START` are reserved for use by the `rand` and `getrandom` crates.

This is identical to `getrandom::Error::INTERNAL_START`.

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#### pub fn new<E>(err: E) -> Error where
E: Into<Box<dyn Error + Sync + Send + 'static, Global>>,

Construct from any type supporting `std::error::Error`

Available only when configured with `std`.

See also `From<NonZeroU32>`, which is available with and without `std`.

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#### pub fn inner(&self) -> &(dyn Error + Sync + Send + 'static)

Reference the inner error (`std` only)

When configured with `std`, this is a trivial operation and never panics. Without `std`, this method is simply unavailable.

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#### pub fn take_inner(self) -> Box<dyn Error + Sync + Send + 'static, Global>

Unwrap the inner error (`std` only)

When configured with `std`, this is a trivial operation and never panics. Without `std`, this method is simply unavailable.

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#### pub fn raw_os_error(&self) -> Option<i32>

Extract the raw OS error code (if this error came from the OS)

This method is identical to `std::io::Error::raw_os_error()`, except that it works in `no_std` contexts. If this method returns `None`, the error value can still be formatted via the `Diplay` implementation.

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#### pub fn code(&self) -> Option<NonZeroU32>

Retrieve the error code, if any.

If this `Error` was constructed via `From<NonZeroU32>`, then this method will return this `NonZeroU32` code (for `no_std` this is always the case). Otherwise, this method will return `None`.

## Trait Implementations

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### impl Debug for Error

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

Formats the value using the given formatter. Read more

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### impl Display for Error

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

Formats the value using the given formatter. Read more

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### impl Error for Error

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#### fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any. Read more

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#### fn backtrace(&self) -> Option<&Backtrace>

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

Returns a stack backtrace, if available, of where this error occurred. Read more

1.0.0 · source

#### fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

Read more
1.0.0 · source

#### fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

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### impl From<Error> for Error

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#### fn from(error: Error) -> Error

Converts to this type from the input type.

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### impl From<NonZeroU32> for Error

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#### fn from(code: NonZeroU32) -> Error

Converts to this type from the input type.

## Auto Trait Implementations

### impl !RefUnwindSafe for Error

### impl Send for Error

### impl Sync for Error

### impl Unpin for Error

### impl !UnwindSafe for Error

## Blanket Implementations

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToString for T where
T: Display + ?Sized,

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#### default fn to_string(&self) -> String

Converts the given value to a `String`. Read more

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

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### impl<V, T> VZip<V> for T where
V: MultiLane<T>,

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#### fn vzip(self) -> V