1.0.0[][src]Trait std::convert::From

pub trait From<T> {
    fn from(T) -> Self;
}

Simple and safe type conversions in to Self. It is the reciprocal of Into.

This trait is useful when performing error handling as described by the book and is closely related to the ? operator.

When constructing a function that is capable of failing the return type will generally be of the form Result<T, E>.

The From trait allows for simplification of error handling by providing a means of returning a single error type that encapsulates numerous possible erroneous situations.

This trait is not limited to error handling, rather the general case for this trait would be in any type conversions to have an explicit definition of how they are performed.

Note: this trait must not fail. If the conversion can fail, use TryFrom or a dedicated method which returns an Option<T> or a Result<T, E>.

Generic Implementations

Examples

String implements From<&str>:

let string = "hello".to_string();
let other_string = String::from("hello");

assert_eq!(string, other_string);Run

An example usage for error handling:

use std::io::{self, Read};
use std::num;

enum CliError {
    IoError(io::Error),
    ParseError(num::ParseIntError),
}

impl From<io::Error> for CliError {
    fn from(error: io::Error) -> Self {
        CliError::IoError(error)
    }
}

impl From<num::ParseIntError> for CliError {
    fn from(error: num::ParseIntError) -> Self {
        CliError::ParseError(error)
    }
}

fn open_and_parse_file(file_name: &str) -> Result<i32, CliError> {
    let mut file = std::fs::File::open("test")?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    let num: i32 = contents.trim().parse()?;
    Ok(num)
}Run

Required Methods

Performs the conversion.

Implementations on Foreign Types

impl<T> From for T
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Implementors

impl From<u16> for AtomicU16
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impl From<bool> for i8
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Converts a bool to a i8. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(i8::from(true), 1);
assert_eq!(i8::from(false), 0);Run

impl From<i8> for f64
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Converts i8 to f64 losslessly.

impl<T> From<Unique<T>> for NonNull<T> where
    T: ?Sized
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impl From<u8> for f64
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Converts u8 to f64 losslessly.

impl From<u8> for i128
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Converts u8 to i128 losslessly.

impl From<bool> for u64
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Converts a bool to a u64. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u64::from(true), 1);
assert_eq!(u64::from(false), 0);Run

impl From<u64> for i128
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Converts u64 to i128 losslessly.

impl<T> From<T> for Option<T>
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impl From<u8> for isize
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Converts u8 to isize losslessly.

impl From<i16> for f64
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Converts i16 to f64 losslessly.

impl From<i32> for f64
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Converts i32 to f64 losslessly.

impl From<u16> for u64
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Converts u16 to u64 losslessly.

impl From<bool> for i16
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Converts a bool to a i16. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(i16::from(true), 1);
assert_eq!(i16::from(false), 0);Run

impl From<i32> for i64
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Converts i32 to i64 losslessly.

impl<'a, T> From<&'a T> for NonNull<T> where
    T: ?Sized
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impl From<u8> for u32
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Converts u8 to u32 losslessly.

impl<T> From<T> for Cell<T>
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impl From<char> for u32
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impl From<LocalWaker> for Waker
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impl From<bool> for u128
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Converts a bool to a u128. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u128::from(true), 1);
assert_eq!(u128::from(false), 0);Run

impl From<i8> for i128
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Converts i8 to i128 losslessly.

impl From<i8> for AtomicI8
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impl From<f32> for f64
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Converts f32 to f64 losslessly.

impl From<u8> for i64
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Converts u8 to i64 losslessly.

impl From<i8> for isize
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Converts i8 to isize losslessly.

impl From<i64> for i128
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Converts i64 to i128 losslessly.

impl From<u16> for i64
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Converts u16 to i64 losslessly.

impl<T> From<T> for Poll<T>
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impl From<u8> for usize
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Converts u8 to usize losslessly.

impl From<bool> for i64
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Converts a bool to a i64. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(i64::from(true), 1);
assert_eq!(i64::from(false), 0);Run

impl From<bool> for AtomicBool
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impl From<u16> for f64
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Converts u16 to f64 losslessly.

impl From<bool> for i32
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Converts a bool to a i32. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(i32::from(true), 1);
assert_eq!(i32::from(false), 0);Run

impl From<u32> for u64
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Converts u32 to u64 losslessly.

impl From<i8> for i64
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Converts i8 to i64 losslessly.

impl From<u8> for i32
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Converts u8 to i32 losslessly.

impl From<i16> for i64
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Converts i16 to i64 losslessly.

impl From<usize> for AtomicUsize
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impl From<u64> for u128
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Converts u64 to u128 losslessly.

impl From<bool> for u16
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Converts a bool to a u16. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u16::from(true), 1);
assert_eq!(u16::from(false), 0);Run

impl From<u8> for i16
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Converts u8 to i16 losslessly.

impl From<u8> for AtomicU8
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impl From<u8> for f32
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Converts u8 to f32 losslessly.

impl From<u16> for u128
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Converts u16 to u128 losslessly.

impl From<bool> for u32
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Converts a bool to a u32. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u32::from(true), 1);
assert_eq!(u32::from(false), 0);Run

impl From<u8> for u16
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Converts u8 to u16 losslessly.

impl From<!> for TryFromIntError
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impl From<u8> for char
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Maps a byte in 0x00...0xFF to a char whose code point has the same value, in U+0000 to U+00FF.

Unicode is designed such that this effectively decodes bytes with the character encoding that IANA calls ISO-8859-1. This encoding is compatible with ASCII.

Note that this is different from ISO/IEC 8859-1 a.k.a. ISO 8859-1 (with one less hyphen), which leaves some "blanks", byte values that are not assigned to any character. ISO-8859-1 (the IANA one) assigns them to the C0 and C1 control codes.

Note that this is also different from Windows-1252 a.k.a. code page 1252, which is a superset ISO/IEC 8859-1 that assigns some (not all!) blanks to punctuation and various Latin characters.

To confuse things further, on the Web ascii, iso-8859-1, and windows-1252 are all aliases for a superset of Windows-1252 that fills the remaining blanks with corresponding C0 and C1 control codes.

impl From<i8> for i32
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Converts i8 to i32 losslessly.

impl From<u32> for i64
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Converts u32 to i64 losslessly.

impl From<u16> for u32
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Converts u16 to u32 losslessly.

impl From<i8> for f32
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Converts i8 to f32 losslessly.

impl From<bool> for usize
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Converts a bool to a usize. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(usize::from(true), 1);
assert_eq!(usize::from(false), 0);Run

impl<T> From<T> for RefCell<T>
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impl From<i16> for i128
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Converts i16 to i128 losslessly.

impl<'a, T> From<FutureObj<'a, T>> for LocalFutureObj<'a, T>
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impl From<bool> for u8
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Converts a bool to a u8. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u8::from(true), 1);
assert_eq!(u8::from(false), 0);Run

impl From<i16> for isize
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Converts i16 to isize losslessly.

impl From<u16> for i32
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Converts u16 to i32 losslessly.

impl From<u16> for usize
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Converts u16 to usize losslessly.

impl From<i16> for f32
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Converts i16 to f32 losslessly.

impl From<u16> for i128
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Converts u16 to i128 losslessly.

impl<T> From<T> for T
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impl From<i8> for i16
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Converts i8 to i16 losslessly.

impl From<u8> for u64
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Converts u8 to u64 losslessly.

impl From<bool> for isize
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Converts a bool to a isize. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(isize::from(true), 1);
assert_eq!(isize::from(false), 0);Run

impl From<i16> for i32
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Converts i16 to i32 losslessly.

impl From<isize> for AtomicIsize
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impl<'a, T> From<&'a mut T> for NonNull<T> where
    T: ?Sized
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impl From<i32> for i128
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Converts i32 to i128 losslessly.

impl From<bool> for i128
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Converts a bool to a i128. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(i128::from(true), 1);
assert_eq!(i128::from(false), 0);Run

impl From<i64> for AtomicI64
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impl From<u32> for AtomicU32
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impl From<i32> for AtomicI32
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impl From<u8> for u128
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Converts u8 to u128 losslessly.

impl<T> From<T> for UnsafeCell<T>
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impl<T> From<*mut T> for AtomicPtr<T>
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impl From<u32> for i128
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Converts u32 to i128 losslessly.

impl From<u16> for f32
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Converts u16 to f32 losslessly.

impl From<u32> for u128
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Converts u32 to u128 losslessly.

impl From<u32> for f64
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Converts u32 to f64 losslessly.

impl From<i16> for AtomicI16
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impl From<u64> for AtomicU64
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impl<T> From<Vec<T>> for Rc<[T]>
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impl<T> From<T> for Arc<T>
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impl<T> From<Box<T>> for Rc<T> where
    T: ?Sized
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impl<'a, T> From<Vec<T>> for Cow<'a, [T]> where
    T: Clone
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impl From<String> for Rc<str>
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impl From<String> for Box<str>
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Important traits for Box<I>

impl<T> From<Box<[T]>> for Vec<T>
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Important traits for Vec<u8>

impl<T> From<Box<T>> for PinBox<T> where
    T: ?Sized
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impl<T> From<Box<T>> for Arc<T> where
    T: ?Sized
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impl<'a> From<&'a str> for Cow<'a, str>
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impl<'a> From<Cow<'a, str>> for String
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impl<'a, T> From<&'a Vec<T>> for Cow<'a, [T]> where
    T: Clone
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impl<'a, F> From<Box<F>> for FutureObj<'a, ()> where
    F: 'a + Send + Future<Output = ()>, 
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impl<'a, T> From<&'a mut [T]> for Vec<T> where
    T: Clone
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Important traits for Vec<u8>

impl<'a> From<&'a str> for String
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impl<T> From<Arc<T>> for Waker where
    T: Wake + 'static, 
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impl<'a> From<&'a String> for Cow<'a, str>
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impl<'a, T> From<&'a [T]> for Cow<'a, [T]> where
    T: Clone
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impl<'a, T> From<&'a [T]> for Box<[T]> where
    T: Copy
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Important traits for Box<I>

impl<'a> From<String> for Cow<'a, str>
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impl<'a, T> From<&'a [T]> for Rc<[T]> where
    T: Clone
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impl From<AllocErr> for CollectionAllocErr
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impl<T> From<BinaryHeap<T>> for Vec<T>
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Important traits for Vec<u8>

impl<'a> From<&'a str> for Box<str>
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Important traits for Box<I>

impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where
    [T]: ToOwned,
    <[T] as ToOwned>::Owned == Vec<T>, 
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Important traits for Vec<u8>

impl<'a, F> From<PinBox<F>> for LocalFutureObj<'a, ()> where
    F: 'a + Future<Output = ()>, 
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impl<'a, T> From<&'a [T]> for Vec<T> where
    T: Clone
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Important traits for Vec<u8>

impl<T> From<Vec<T>> for Box<[T]>
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Important traits for Box<I>

impl From<Box<str>> for String
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impl From<Box<str>> for Box<[u8]>
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Important traits for Box<I>

impl<T> From<Vec<T>> for VecDeque<T>
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impl<'a, T> From<&'a [T]> for Arc<[T]> where
    T: Clone
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impl<T> From<PinBox<T>> for Box<T> where
    T: Unpin + ?Sized
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Important traits for Box<I>

impl From<String> for Arc<str>
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impl From<LayoutErr> for CollectionAllocErr
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impl<T> From<Vec<T>> for BinaryHeap<T> where
    T: Ord
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impl<T> From<T> for Box<T>
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Important traits for Box<I>

impl From<String> for Vec<u8>
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Important traits for Vec<u8>

impl<'a> From<&'a str> for Rc<str>
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impl<T> From<T> for Rc<T>
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impl<T> From<VecDeque<T>> for Vec<T>
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Important traits for Vec<u8>

impl<'a, F> From<Box<F>> for LocalFutureObj<'a, ()> where
    F: 'a + Future<Output = ()>, 
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impl<'a> From<&'a str> for Arc<str>
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impl<T> From<Vec<T>> for Arc<[T]>
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impl<'a, F> From<PinBox<F>> for FutureObj<'a, ()> where
    F: 'a + Send + Future<Output = ()>, 
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impl<'a> From<&'a str> for Vec<u8>
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Important traits for Vec<u8>

impl<'a, E: Error + 'a> From<E> for Box<Error + 'a>
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Important traits for Box<I>

impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<Error + Send + Sync + 'a>
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Important traits for Box<I>

impl From<String> for Box<Error + Send + Sync>
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Important traits for Box<I>

impl From<String> for Box<Error>
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Important traits for Box<I>

impl<'a, 'b> From<&'b str> for Box<Error + Send + Sync + 'a>
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Important traits for Box<I>

impl<'a> From<&'a str> for Box<Error>
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Important traits for Box<I>

impl<'a, 'b> From<Cow<'b, str>> for Box<Error + Send + Sync + 'a>
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Important traits for Box<I>

impl<'a> From<Cow<'a, str>> for Box<Error>
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Important traits for Box<I>

impl From<CString> for Vec<u8>
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Important traits for Vec<u8>

Converts a CString into a Vec<u8>.

The conversion consumes the CString, and removes the terminating NUL byte.

impl<'a> From<Cow<'a, CStr>> for CString
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impl<'a> From<&'a CStr> for Box<CStr>
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Important traits for Box<I>

impl From<Box<CStr>> for CString
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Converts a Box<CStr> into a CString without copying or allocating.

impl From<CString> for Box<CStr>
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Important traits for Box<I>

Converts a CString into a Box<CStr> without copying or allocating.

impl<'a> From<CString> for Cow<'a, CStr>
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impl<'a> From<&'a CStr> for Cow<'a, CStr>
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impl<'a> From<&'a CString> for Cow<'a, CStr>
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impl From<CString> for Arc<CStr>
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Converts a CString into a Arc<CStr> without copying or allocating.

impl<'a> From<&'a CStr> for Arc<CStr>
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impl From<CString> for Rc<CStr>
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Converts a CString into a Rc<CStr> without copying or allocating.

impl<'a> From<&'a CStr> for Rc<CStr>
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impl From<NulError> for std::io::Error
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Converts a NulError into a io::Error.

impl<'a> From<&'a CStr> for CString
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impl From<String> for OsString
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Converts a String into a OsString.

The conversion copies the data, and includes an allocation on the heap.

impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for OsString
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impl<'a> From<&'a OsStr> for Box<OsStr>
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Important traits for Box<I>

impl From<Box<OsStr>> for OsString
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Converts a Box<OsStr> into a OsString without copying or allocating.

impl From<OsString> for Box<OsStr>
[src]

Important traits for Box<I>

Converts a OsString into a Box<OsStr> without copying or allocating.

impl From<OsString> for Arc<OsStr>
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Converts a OsString into a Arc<OsStr> without copying or allocating.

impl<'a> From<&'a OsStr> for Arc<OsStr>
[src]

impl From<OsString> for Rc<OsStr>
[src]

Converts a OsString into a Rc<OsStr> without copying or allocating.

impl<'a> From<&'a OsStr> for Rc<OsStr>
[src]

impl<'a> From<OsString> for Cow<'a, OsStr>
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impl<'a> From<&'a OsStr> for Cow<'a, OsStr>
[src]

impl<'a> From<&'a OsString> for Cow<'a, OsStr>
[src]

impl<'a> From<Cow<'a, OsStr>> for OsString
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impl<W> From<IntoInnerError<W>> for std::io::Error
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impl From<ErrorKind> for std::io::Error
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Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.

impl From<Ipv4Addr> for IpAddr
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impl From<Ipv6Addr> for IpAddr
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impl From<Ipv4Addr> for u32
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Convert an Ipv4Addr into a host byte order u32.

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::new(13, 12, 11, 10);
assert_eq!(0x0d0c0b0au32, u32::from(addr));Run

impl From<u32> for Ipv4Addr
[src]

Convert a host byte order u32 into an Ipv4Addr.

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::from(0x0d0c0b0au32);
assert_eq!(Ipv4Addr::new(13, 12, 11, 10), addr);Run

impl From<[u8; 4]> for Ipv4Addr
[src]

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::from([13u8, 12u8, 11u8, 10u8]);
assert_eq!(Ipv4Addr::new(13, 12, 11, 10), addr);Run

impl From<[u8; 4]> for IpAddr
[src]

Create an IpAddr::V4 from a four element byte array.

Examples

use std::net::{IpAddr, Ipv4Addr};

let addr = IpAddr::from([13u8, 12u8, 11u8, 10u8]);
assert_eq!(IpAddr::V4(Ipv4Addr::new(13, 12, 11, 10)), addr);Run

impl From<Ipv6Addr> for u128
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impl From<u128> for Ipv6Addr
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impl From<[u8; 16]> for Ipv6Addr
[src]

impl From<[u16; 8]> for Ipv6Addr
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impl From<[u8; 16]> for IpAddr
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Create an IpAddr::V6 from a sixteen element byte array.

Examples

use std::net::{IpAddr, Ipv6Addr};

let addr = IpAddr::from([
    25u8, 24u8, 23u8, 22u8, 21u8, 20u8, 19u8, 18u8,
    17u8, 16u8, 15u8, 14u8, 13u8, 12u8, 11u8, 10u8,
]);
assert_eq!(
    IpAddr::V6(Ipv6Addr::new(
        0x1918, 0x1716,
        0x1514, 0x1312,
        0x1110, 0x0f0e,
        0x0d0c, 0x0b0a
    )),
    addr
);Run

impl From<[u16; 8]> for IpAddr
[src]

Create an IpAddr::V6 from an eight element 16-bit array.

Examples

use std::net::{IpAddr, Ipv6Addr};

let addr = IpAddr::from([
    525u16, 524u16, 523u16, 522u16,
    521u16, 520u16, 519u16, 518u16,
]);
assert_eq!(
    IpAddr::V6(Ipv6Addr::new(
        0x20d, 0x20c,
        0x20b, 0x20a,
        0x209, 0x208,
        0x207, 0x206
    )),
    addr
);Run

impl From<SocketAddrV4> for std::net::SocketAddr
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impl From<SocketAddrV6> for std::net::SocketAddr
[src]

impl<I: Into<IpAddr>> From<(I, u16)> for std::net::SocketAddr
[src]

impl<'a> From<&'a Path> for Box<Path>
[src]

Important traits for Box<I>

impl From<Box<Path>> for PathBuf
[src]

impl From<PathBuf> for Box<Path>
[src]

Important traits for Box<I>

impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for PathBuf
[src]

impl From<OsString> for PathBuf
[src]

impl From<PathBuf> for OsString
[src]

impl From<String> for PathBuf
[src]

impl<'a> From<&'a Path> for Cow<'a, Path>
[src]

impl<'a> From<PathBuf> for Cow<'a, Path>
[src]

impl<'a> From<&'a PathBuf> for Cow<'a, Path>
[src]

impl<'a> From<Cow<'a, Path>> for PathBuf
[src]

impl From<PathBuf> for Arc<Path>
[src]

impl<'a> From<&'a Path> for Arc<Path>
[src]

impl From<PathBuf> for Rc<Path>
[src]

impl<'a> From<&'a Path> for Rc<Path>
[src]

impl From<ChildStdin> for Stdio
[src]

impl From<ChildStdout> for Stdio
[src]

impl From<ChildStderr> for Stdio
[src]

impl From<File> for Stdio
[src]

impl<T> From<SendError<T>> for TrySendError<T>
[src]

impl From<RecvError> for TryRecvError
[src]

impl From<RecvError> for RecvTimeoutError
[src]

impl<T> From<T> for Mutex<T>
[src]

Creates a new mutex in an unlocked state ready for use. This is equivalent to Mutex::new.

impl<T> From<T> for RwLock<T>
[src]

Creates a new instance of an RwLock<T> which is unlocked. This is equivalent to RwLock::new.

impl<T> From<PoisonError<T>> for TryLockError<T>
[src]