Trait nom::lib::std::convert::From

pub trait From<T> {
#[lang = "from"]    pub fn from(T) -> Self;
}

Used to do value-to-value conversions while consuming the input value. It is the reciprocal of Into.

One should always prefer implementing From over Into because implementing From automatically provides one with an implementation of Into thanks to the blanket implementation in the standard library.

Only implement Into when targeting a version prior to Rust 1.41 and converting to a type outside the current crate. From was not able to do these types of conversions in earlier versions because of Rust’s orphaning rules. See Into for more details.

Prefer using Into over using From when specifying trait bounds on a generic function. This way, types that directly implement Into can be used as arguments as well.

The From is also very useful when performing error handling. When constructing a function that is capable of failing, the return type will generally be of the form Result<T, E>. The From trait simplifies error handling by allowing a function to return a single error type that encapsulate multiple error types. See the “Examples” section and the book for more details.

Note: This trait must not fail. If the conversion can fail, use TryFrom.

Generic Implementations

• From<T> for U implies Into<U> for T
• From is reflexive, which means that From<T> for T is implemented

Examples

String implements From<&str>:

An explicit conversion from a &str to a String is done as follows:

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

assert_eq!(string, other_string);

While performing error handling it is often useful to implement From for your own error type. By converting underlying error types to our own custom error type that encapsulates the underlying error type, we can return a single error type without losing information on the underlying cause. The ‘?’ operator automatically converts the underlying error type to our custom error type by calling Into<CliError>::into which is automatically provided when implementing From. The compiler then infers which implementation of Into should be used.

use std::fs;
use std::io;
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 contents = fs::read_to_string(&file_name)?;
    let num: i32 = contents.trim().parse()?;
    Ok(num)
}

Required methods

#[lang = "from"]pub fn from(T) -> Self

Performs the conversion.

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Implementations on Foreign Types

impl<'_> From<&'_ CStr> for Arc<CStr>

pub fn from(s: &CStr) -> Arc<CStr>

impl From<u128> for Ipv6Addr

pub fn from(ip: u128) -> Ipv6Addr

Convert a host byte order u128 into an Ipv6Addr.

Examples

use std::net::Ipv6Addr;

let addr = Ipv6Addr::from(0x102030405060708090A0B0C0D0E0F00D_u128);
assert_eq!(
    Ipv6Addr::new(
        0x1020, 0x3040, 0x5060, 0x7080,
        0x90A0, 0xB0C0, 0xD0E0, 0xF00D,
    ),
    addr);

impl From<ErrorKind> for Error

Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.

pub fn from(kind: ErrorKind) -> Error

Converts an ErrorKind into an Error.

This conversion allocates a new error with a simple representation of error kind.

Examples

use std::io::{Error, ErrorKind};

let not_found = ErrorKind::NotFound;
let error = Error::from(not_found);
assert_eq!("entity not found", format!("{}", error));

impl From<Ipv6Addr> for IpAddr

pub fn from(ipv6: Ipv6Addr) -> IpAddr

Copies this address to a new IpAddr::V6.

Examples

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

let addr = Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff);

assert_eq!(
    IpAddr::V6(addr),
    IpAddr::from(addr)
);

impl From<Ipv6Addr> for u128

pub fn from(ip: Ipv6Addr) -> u128

Convert an Ipv6Addr into a host byte order u128.

Examples

use std::net::Ipv6Addr;

let addr = Ipv6Addr::new(
    0x1020, 0x3040, 0x5060, 0x7080,
    0x90A0, 0xB0C0, 0xD0E0, 0xF00D,
);
assert_eq!(0x102030405060708090A0B0C0D0E0F00D_u128, u128::from(addr));

impl From<[u16; 8]> for IpAddr

pub fn from(segments: [u16; 8]) -> IpAddr

Creates 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
);

impl From<String> for OsString

pub fn from(s: String) -> OsString

Converts a String into a OsString.

This conversion does not allocate or copy memory.

impl From<OsString> for Rc<OsStr>

pub fn from(s: OsString) -> Rc<OsStr>

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

impl From<CString> for Arc<CStr>

pub fn from(s: CString) -> Arc<CStr>

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

impl From<Box<OsStr, Global>> for OsString

pub fn from(boxed: Box<OsStr, Global>) -> OsString

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

impl From<SocketAddrV6> for SocketAddr

pub fn from(sock6: SocketAddrV6) -> SocketAddr

Converts a SocketAddrV6 into a SocketAddr::V6.

impl<T> From<SendError<T>> for TrySendError<T>

pub fn from(err: SendError<T>) -> TrySendError<T>

Converts a SendError<T> into a TrySendError<T>.

This conversion always returns a TrySendError::Disconnected containing the data in the SendError<T>.

No data is allocated on the heap.

impl From<PathBuf> for Rc<Path>

pub fn from(s: PathBuf) -> Rc<Path>

Converts a PathBuf into an Rc by moving the PathBuf data into a new Rc buffer.

impl From<Ipv4Addr> for IpAddr

pub fn from(ipv4: Ipv4Addr) -> IpAddr

Copies this address to a new IpAddr::V4.

Examples

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

let addr = Ipv4Addr::new(127, 0, 0, 1);

assert_eq!(
    IpAddr::V4(addr),
    IpAddr::from(addr)
)

impl<'a> From<Cow<'a, CStr>> for CString

pub fn from(s: Cow<'a, CStr>) -> CString

impl<T> From<PoisonError<T>> for TryLockError<T>

pub fn from(err: PoisonError<T>) -> TryLockError<T>

impl<'_> From<&'_ CStr> for CString

pub fn from(s: &CStr) -> CString

impl From<Box<CStr, Global>> for CString

pub fn from(s: Box<CStr, Global>) -> CString

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

impl From<[u8; 4]> for IpAddr

pub fn from(octets: [u8; 4]) -> IpAddr

Creates 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);

impl<T> From<T> for SyncOnceCell<T>

pub fn from(value: T) -> SyncOnceCell<T>

impl From<NulError> for Error

pub fn from(NulError) -> Error

Converts a NulError into a io::Error.

impl<'_> From<&'_ OsStr> for Rc<OsStr>

pub fn from(s: &OsStr) -> Rc<OsStr>

impl From<PathBuf> for Arc<Path>

pub fn from(s: PathBuf) -> Arc<Path>

Converts a PathBuf into an Arc by moving the PathBuf data into a new Arc buffer.

impl<'_> From<&'_ Path> for Rc<Path>

pub fn from(s: &Path) -> Rc<Path>

Converts a Path into an Rc by copying the Path data into a new Rc buffer.

impl From<OsString> for PathBuf

pub fn from(s: OsString) -> PathBuf

Converts an OsString into a PathBuf

This conversion does not allocate or copy memory.

impl From<PathBuf> for OsString

pub fn from(path_buf: PathBuf) -> OsString

Converts a PathBuf into an OsString

This conversion does not allocate or copy memory.

impl<'a> From<Cow<'a, Path>> for PathBuf

pub fn from(p: Cow<'a, Path>) -> PathBuf

impl From<[u8; 16]> for IpAddr

pub fn from(octets: [u8; 16]) -> IpAddr

Creates 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
);

impl<'_> From<&'_ Path> for Arc<Path>

pub fn from(s: &Path) -> Arc<Path>

Converts a Path into an Arc by copying the Path data into a new Arc buffer.

impl<T> From<T> for RwLock<T>

pub fn from(t: T) -> RwLock<T>

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

impl<'a> From<Cow<'a, OsStr>> for OsString

pub fn from(s: Cow<'a, OsStr>) -> OsString

impl From<String> for PathBuf

pub fn from(s: String) -> PathBuf

Converts a String into a PathBuf

This conversion does not allocate or copy memory.

impl From<RecvError> for TryRecvError

pub fn from(err: RecvError) -> TryRecvError

Converts a RecvError into a TryRecvError.

This conversion always returns TryRecvError::Disconnected.

No data is allocated on the heap.

impl<'_, T> From<&'_ T> for PathBuf where
    T: AsRef<OsStr> + ?Sized, 

pub fn from(s: &T) -> PathBuf

impl<'_> From<&'_ CStr> for Rc<CStr>

pub fn from(s: &CStr) -> Rc<CStr>

impl<'_> From<&'_ OsStr> for Arc<OsStr>

pub fn from(s: &OsStr) -> Arc<OsStr>

impl From<u32> for Ipv4Addr

pub fn from(ip: u32) -> Ipv4Addr

Converts a host byte order u32 into an Ipv4Addr.

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::from(0xcafebabe);
assert_eq!(Ipv4Addr::new(0xca, 0xfe, 0xba, 0xbe), addr);

impl From<Vec<NonZeroU8, Global>> for CString

pub fn from(v: Vec<NonZeroU8, Global>) -> CString

Converts a Vec<NonZeroU8> into a CString without copying nor checking for inner null bytes.

impl<W> From<IntoInnerError<W>> for Error

pub fn from(iie: IntoInnerError<W>) -> Error

impl<T> From<T> for Mutex<T>

pub fn from(t: T) -> Mutex<T>

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

impl From<RecvError> for RecvTimeoutError

pub fn from(err: RecvError) -> RecvTimeoutError

Converts a RecvError into a RecvTimeoutError.

This conversion always returns RecvTimeoutError::Disconnected.

No data is allocated on the heap.

impl From<SocketAddrV4> for SocketAddr

pub fn from(sock4: SocketAddrV4) -> SocketAddr

Converts a SocketAddrV4 into a SocketAddr::V4.

impl From<File> for Stdio

pub fn from(file: File) -> Stdio

Converts a File into a Stdio

Examples

File will be converted to Stdio using Stdio::from under the hood.

use std::fs::File;
use std::process::Command;

// With the `foo.txt` file containing `Hello, world!"
let file = File::open("foo.txt").unwrap();

let reverse = Command::new("rev")
    .stdin(file)  // Implicit File conversion into a Stdio
    .output()
    .expect("failed reverse command");

assert_eq!(reverse.stdout, b"!dlrow ,olleH");

impl From<Box<Path, Global>> for PathBuf

pub fn from(boxed: Box<Path, Global>) -> PathBuf

Converts a Box<Path> into a PathBuf

This conversion does not allocate or copy memory.

impl<I> From<(I, u16)> for SocketAddr where
    I: Into<IpAddr>, 

pub fn from(pieces: (I, u16)) -> SocketAddr

Converts a tuple struct (Into<IpAddr>, u16) into a SocketAddr.

This conversion creates a SocketAddr::V4 for a IpAddr::V4 and creates a SocketAddr::V6 for a IpAddr::V6.

u16 is treated as port of the newly created SocketAddr.

impl<'_, T> From<&'_ T> for OsString where
    T: AsRef<OsStr> + ?Sized, 

pub fn from(s: &T) -> OsString

impl From<CString> for Rc<CStr>

pub fn from(s: CString) -> Rc<CStr>

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

impl From<OsString> for Arc<OsStr>

pub fn from(s: OsString) -> Arc<OsStr>

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

impl From<[u8; 4]> for Ipv4Addr

pub fn from(octets: [u8; 4]) -> Ipv4Addr

Creates an Ipv4Addr from a four element byte array.

Examples

use std::net::Ipv4Addr;

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

impl From<ChildStdin> for Stdio

pub fn from(child: ChildStdin) -> Stdio

Converts a ChildStdin into a Stdio

Examples

ChildStdin will be converted to Stdio using Stdio::from under the hood.

use std::process::{Command, Stdio};

let reverse = Command::new("rev")
    .stdin(Stdio::piped())
    .spawn()
    .expect("failed reverse command");

let _echo = Command::new("echo")
    .arg("Hello, world!")
    .stdout(reverse.stdin.unwrap()) // Converted into a Stdio here
    .output()
    .expect("failed echo command");

// "!dlrow ,olleH" echoed to console

impl From<ChildStderr> for Stdio

pub fn from(child: ChildStderr) -> Stdio

Converts a ChildStderr into a Stdio

Examples

use std::process::{Command, Stdio};

let reverse = Command::new("rev")
    .arg("non_existing_file.txt")
    .stderr(Stdio::piped())
    .spawn()
    .expect("failed reverse command");

let cat = Command::new("cat")
    .arg("-")
    .stdin(reverse.stderr.unwrap()) // Converted into a Stdio here
    .output()
    .expect("failed echo command");

assert_eq!(
    String::from_utf8_lossy(&cat.stdout),
    "rev: cannot open non_existing_file.txt: No such file or directory\n"
);

impl From<[u8; 16]> for Ipv6Addr

pub fn from(octets: [u8; 16]) -> Ipv6Addr

Creates an Ipv6Addr from a sixteen element byte array.

Examples

use std::net::Ipv6Addr;

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

impl From<[u16; 8]> for Ipv6Addr

pub fn from(segments: [u16; 8]) -> Ipv6Addr

Creates an Ipv6Addr from an eight element 16-bit array.

Examples

use std::net::Ipv6Addr;

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

impl From<Ipv4Addr> for u32

pub fn from(ip: Ipv4Addr) -> u32

Converts an Ipv4Addr into a host byte order u32.

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::new(0xca, 0xfe, 0xba, 0xbe);
assert_eq!(0xcafebabe, u32::from(addr));

impl From<ChildStdout> for Stdio

pub fn from(child: ChildStdout) -> Stdio

Converts a ChildStdout into a Stdio

Examples

ChildStdout will be converted to Stdio using Stdio::from under the hood.

use std::process::{Command, Stdio};

let hello = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::piped())
    .spawn()
    .expect("failed echo command");

let reverse = Command::new("rev")
    .stdin(hello.stdout.unwrap())  // Converted into a Stdio here
    .output()
    .expect("failed reverse command");

assert_eq!(reverse.stdout, b"!dlrow ,olleH\n");

impl From<Infallible> for TryFromSliceError

pub fn from(x: Infallible) -> TryFromSliceError

impl From<NonZeroU32> for u32

pub fn from(nonzero: NonZeroU32) -> u32

Converts a NonZeroU32 into an u32

impl<'_, T> From<&'_ mut T> for NonNull<T> where
    T: ?Sized, 

pub fn from(reference: &mut T) -> NonNull<T>

impl From<i16> for f64

Converts i16 to f64 losslessly.

pub fn from(small: i16) -> f64

impl From<i32> for AtomicI32

pub fn from(v: i32) -> AtomicI32

Converts an i32 into an AtomicI32.

impl From<bool> for i8

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);

pub fn from(small: bool) -> i8

impl From<NonZeroU32> for NonZeroU64

Converts NonZeroU32 to NonZeroU64 losslessly.

pub fn from(small: NonZeroU32) -> NonZeroU64

impl From<NonZeroU8> for NonZeroI128

Converts NonZeroU8 to NonZeroI128 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroI128

impl<T> From<Unique<T>> for NonNull<T> where
    T: ?Sized, 

pub fn from(unique: Unique<T>) -> NonNull<T>

impl From<i8> for AtomicI8

pub fn from(v: i8) -> AtomicI8

Converts an i8 into an AtomicI8.

impl From<NonZeroU16> for u16

pub fn from(nonzero: NonZeroU16) -> u16

Converts a NonZeroU16 into an u16

impl From<NonZeroU64> for NonZeroI128

Converts NonZeroU64 to NonZeroI128 losslessly.

pub fn from(small: NonZeroU64) -> NonZeroI128

impl From<f32> for f64

Converts f32 to f64 losslessly.

pub fn from(small: f32) -> f64

impl From<u16> for u64

Converts u16 to u64 losslessly.

pub fn from(small: u16) -> u64

impl From<NonZeroU128> for u128

pub fn from(nonzero: NonZeroU128) -> u128

Converts a NonZeroU128 into an u128

impl From<i32> for f64

Converts i32 to f64 losslessly.

pub fn from(small: i32) -> f64

impl From<u64> for i128

Converts u64 to i128 losslessly.

pub fn from(small: u64) -> i128

impl From<u8> for u16

Converts u8 to u16 losslessly.

pub fn from(small: u8) -> u16

impl From<u8> for AtomicU8

pub fn from(v: u8) -> AtomicU8

Converts an u8 into an AtomicU8.

impl From<u16> for u128

Converts u16 to u128 losslessly.

pub fn from(small: u16) -> u128

impl From<i8> for f64

Converts i8 to f64 losslessly.

pub fn from(small: i8) -> f64

impl From<NonZeroU8> for NonZeroUsize

Converts NonZeroU8 to NonZeroUsize losslessly.

pub fn from(small: NonZeroU8) -> NonZeroUsize

impl From<u8> for i64

Converts u8 to i64 losslessly.

pub fn from(small: u8) -> i64

impl<'_, T> From<&'_ T> for NonNull<T> where
    T: ?Sized, 

pub fn from(reference: &T) -> NonNull<T>

impl From<u32> for u128

Converts u32 to u128 losslessly.

pub fn from(small: u32) -> u128

impl From<bool> for u128

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);

pub fn from(small: bool) -> u128

impl From<u8> for i32

Converts u8 to i32 losslessly.

pub fn from(small: u8) -> i32

impl From<u64> for u128

Converts u64 to u128 losslessly.

pub fn from(small: u64) -> u128

impl From<i32> for i128

Converts i32 to i128 losslessly.

pub fn from(small: i32) -> i128

impl From<u32> for i128

Converts u32 to i128 losslessly.

pub fn from(small: u32) -> i128

impl From<bool> for u32

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);

pub fn from(small: bool) -> u32

impl From<bool> for u8

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);

pub fn from(small: bool) -> u8

impl From<i16> for i64

Converts i16 to i64 losslessly.

pub fn from(small: i16) -> i64

impl From<NonZeroU8> for NonZeroI32

Converts NonZeroU8 to NonZeroI32 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroI32

impl From<u16> for u32

Converts u16 to u32 losslessly.

pub fn from(small: u16) -> u32

impl From<NonZeroU8> for NonZeroU16

Converts NonZeroU8 to NonZeroU16 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroU16

impl From<bool> for i64

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);

pub fn from(small: bool) -> i64

impl<T> From<T> for UnsafeCell<T>

pub fn from(t: T) -> UnsafeCell<T>

impl<T> From<*mut T> for AtomicPtr<T>

pub fn from(p: *mut T) -> AtomicPtr<T>

impl From<i16> for i32

Converts i16 to i32 losslessly.

pub fn from(small: i16) -> i32

impl From<i32> for i64

Converts i32 to i64 losslessly.

pub fn from(small: i32) -> i64

impl From<u8> for u64

Converts u8 to u64 losslessly.

pub fn from(small: u8) -> u64

impl From<NonZeroI16> for NonZeroI128

Converts NonZeroI16 to NonZeroI128 losslessly.

pub fn from(small: NonZeroI16) -> NonZeroI128

impl From<NonZeroU8> for u8

pub fn from(nonzero: NonZeroU8) -> u8

Converts a NonZeroU8 into an u8

impl From<bool> for i128

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);

pub fn from(small: bool) -> i128

impl From<NonZeroU16> for NonZeroI32

Converts NonZeroU16 to NonZeroI32 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroI32

impl From<i64> for AtomicI64

pub fn from(v: i64) -> AtomicI64

Converts an i64 into an AtomicI64.

impl From<bool> for isize

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);

pub fn from(small: bool) -> isize

impl From<NonZeroI64> for i64

pub fn from(nonzero: NonZeroI64) -> i64

Converts a NonZeroI64 into an i64

impl From<NonZeroU8> for NonZeroU128

Converts NonZeroU8 to NonZeroU128 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroU128

impl From<char> for u64

pub fn from(c: char) -> u64

Converts a [char] into a [u64].

Examples

use std::mem;

let c = '👤';
let u = u64::from(c);
assert!(8 == mem::size_of_val(&u))

impl From<u16> for usize

Converts u16 to usize losslessly.

pub fn from(small: u16) -> usize

impl From<NonZeroI8> for i8

pub fn from(nonzero: NonZeroI8) -> i8

Converts a NonZeroI8 into an i8

impl From<u16> for AtomicU16

pub fn from(v: u16) -> AtomicU16

Converts an u16 into an AtomicU16.

impl From<u8> for i16

Converts u8 to i16 losslessly.

pub fn from(small: u8) -> i16

impl From<i8> for i32

Converts i8 to i32 losslessly.

pub fn from(small: i8) -> i32

impl From<usize> for AtomicUsize

pub fn from(v: usize) -> AtomicUsize

Converts an usize into an AtomicUsize.

impl From<NonZeroI16> for NonZeroI32

Converts NonZeroI16 to NonZeroI32 losslessly.

pub fn from(small: NonZeroI16) -> NonZeroI32

impl From<char> for u128

pub fn from(c: char) -> u128

Converts a [char] into a [u128].

Examples

use std::mem;

let c = '⚙';
let u = u128::from(c);
assert!(16 == mem::size_of_val(&u))

impl From<u32> for f64

Converts u32 to f64 losslessly.

pub fn from(small: u32) -> f64

impl From<NonZeroU64> for NonZeroU128

Converts NonZeroU64 to NonZeroU128 losslessly.

pub fn from(small: NonZeroU64) -> NonZeroU128

impl From<NonZeroI16> for i16

pub fn from(nonzero: NonZeroI16) -> i16

Converts a NonZeroI16 into an i16

impl From<u32> for i64

Converts u32 to i64 losslessly.

pub fn from(small: u32) -> i64

impl From<NonZeroU32> for NonZeroU128

Converts NonZeroU32 to NonZeroU128 losslessly.

pub fn from(small: NonZeroU32) -> NonZeroU128

impl From<NonZeroU16> for NonZeroU64

Converts NonZeroU16 to NonZeroU64 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroU64

impl From<NonZeroI16> for NonZeroIsize

Converts NonZeroI16 to NonZeroIsize losslessly.

pub fn from(small: NonZeroI16) -> NonZeroIsize

impl From<NonZeroU8> for NonZeroU64

Converts NonZeroU8 to NonZeroU64 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroU64

impl From<Infallible> for TryFromIntError

pub fn from(x: Infallible) -> TryFromIntError

impl From<char> for u32

pub fn from(c: char) -> u32

Converts a [char] into a [u32].

Examples

use std::mem;

let c = 'c';
let u = u32::from(c);
assert!(4 == mem::size_of_val(&u))

impl From<i8> for i16

Converts i8 to i16 losslessly.

pub fn from(small: i8) -> i16

impl From<i8> for isize

Converts i8 to isize losslessly.

pub fn from(small: i8) -> isize

impl From<i16> for i128

Converts i16 to i128 losslessly.

pub fn from(small: i16) -> i128

impl<T> From<T> for OnceCell<T>

pub fn from(value: T) -> OnceCell<T>

impl From<NonZeroUsize> for usize

pub fn from(nonzero: NonZeroUsize) -> usize

Converts a NonZeroUsize into an usize

impl From<u8> for i128

Converts u8 to i128 losslessly.

pub fn from(small: u8) -> i128

impl From<u16> for f32

Converts u16 to f32 losslessly.

pub fn from(small: u16) -> f32

impl<T> From<T> for Poll<T>

pub fn from(t: T) -> Poll<T>

Convert to a Ready variant.

Example

assert_eq!(Poll::from(true), Poll::Ready(true));

impl From<NonZeroI32> for i32

pub fn from(nonzero: NonZeroI32) -> i32

Converts a NonZeroI32 into an i32

impl From<bool> for usize

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);

pub fn from(small: bool) -> usize

impl From<u16> for f64

Converts u16 to f64 losslessly.

pub fn from(small: u16) -> f64

impl From<u32> for AtomicU32

pub fn from(v: u32) -> AtomicU32

Converts an u32 into an AtomicU32.

impl From<u8> for f32

Converts u8 to f32 losslessly.

pub fn from(small: u8) -> f32

impl From<i16> for isize

Converts i16 to isize losslessly.

pub fn from(small: i16) -> isize

impl From<u8> for usize

Converts u8 to usize losslessly.

pub fn from(small: u8) -> usize

impl From<NonZeroIsize> for isize

pub fn from(nonzero: NonZeroIsize) -> isize

Converts a NonZeroIsize into an isize

impl From<u16> for i64

Converts u16 to i64 losslessly.

pub fn from(small: u16) -> i64

impl From<NonZeroU64> for u64

pub fn from(nonzero: NonZeroU64) -> u64

Converts a NonZeroU64 into an u64

impl From<NonZeroU8> for NonZeroU32

Converts NonZeroU8 to NonZeroU32 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroU32

impl From<NonZeroI128> for i128

pub fn from(nonzero: NonZeroI128) -> i128

Converts a NonZeroI128 into an i128

impl From<NonZeroU16> for NonZeroI64

Converts NonZeroU16 to NonZeroI64 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroI64

impl From<u8> for f64

Converts u8 to f64 losslessly.

pub fn from(small: u8) -> f64

impl From<NonZeroU32> for NonZeroI128

Converts NonZeroU32 to NonZeroI128 losslessly.

pub fn from(small: NonZeroU32) -> NonZeroI128

impl From<u64> for AtomicU64

pub fn from(v: u64) -> AtomicU64

Converts an u64 into an AtomicU64.

impl From<NonZeroI8> for NonZeroIsize

Converts NonZeroI8 to NonZeroIsize losslessly.

pub fn from(small: NonZeroI8) -> NonZeroIsize

impl From<isize> for AtomicIsize

pub fn from(v: isize) -> AtomicIsize

Converts an isize into an AtomicIsize.

impl<T> From<T> for RefCell<T>

pub fn from(t: T) -> RefCell<T>

impl From<NonZeroI16> for NonZeroI64

Converts NonZeroI16 to NonZeroI64 losslessly.

pub fn from(small: NonZeroI16) -> NonZeroI64

impl From<bool> for i16

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);

pub fn from(small: bool) -> i16

impl From<u8> for char

Maps a byte in 0x00..=0xFF to a char whose code point has the same value, in U+0000..=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.

pub fn from(i: u8) -> char

Converts a u8 into a [char].

Examples

use std::mem;

let u = 32 as u8;
let c = char::from(u);
assert!(4 == mem::size_of_val(&c))

impl From<NonZeroI64> for NonZeroI128

Converts NonZeroI64 to NonZeroI128 losslessly.

pub fn from(small: NonZeroI64) -> NonZeroI128

impl From<u8> for u32

Converts u8 to u32 losslessly.

pub fn from(small: u8) -> u32

impl From<NonZeroU8> for NonZeroI16

Converts NonZeroU8 to NonZeroI16 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroI16

impl From<i8> for i128

Converts i8 to i128 losslessly.

pub fn from(small: i8) -> i128

impl From<i16> for f32

Converts i16 to f32 losslessly.

pub fn from(small: i16) -> f32

impl From<i8> for i64

Converts i8 to i64 losslessly.

pub fn from(small: i8) -> i64

impl From<u16> for i32

Converts u16 to i32 losslessly.

pub fn from(small: u16) -> i32

impl From<NonZeroI8> for NonZeroI128

Converts NonZeroI8 to NonZeroI128 losslessly.

pub fn from(small: NonZeroI8) -> NonZeroI128

impl From<NonZeroU16> for NonZeroUsize

Converts NonZeroU16 to NonZeroUsize losslessly.

pub fn from(small: NonZeroU16) -> NonZeroUsize

impl From<i64> for i128

Converts i64 to i128 losslessly.

pub fn from(small: i64) -> i128

impl From<NonZeroU32> for NonZeroI64

Converts NonZeroU32 to NonZeroI64 losslessly.

pub fn from(small: NonZeroU32) -> NonZeroI64

impl From<NonZeroI32> for NonZeroI64

Converts NonZeroI32 to NonZeroI64 losslessly.

pub fn from(small: NonZeroI32) -> NonZeroI64

impl From<u32> for u64

Converts u32 to u64 losslessly.

pub fn from(small: u32) -> u64

impl From<i8> for f32

Converts i8 to f32 losslessly.

pub fn from(small: i8) -> f32

impl From<NonZeroU8> for NonZeroI64

Converts NonZeroU8 to NonZeroI64 losslessly.

pub fn from(small: NonZeroU8) -> NonZeroI64

impl<T> From<T> for Cell<T>

pub fn from(t: T) -> Cell<T>

impl From<NonZeroU16> for NonZeroI128

Converts NonZeroU16 to NonZeroI128 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroI128

impl From<bool> for AtomicBool

pub fn from(b: bool) -> AtomicBool

Converts a bool into an AtomicBool.

Examples

use std::sync::atomic::AtomicBool;
let atomic_bool = AtomicBool::from(true);
assert_eq!(format!("{:?}", atomic_bool), "true")

impl From<NonZeroI32> for NonZeroI128

Converts NonZeroI32 to NonZeroI128 losslessly.

pub fn from(small: NonZeroI32) -> NonZeroI128

impl From<NonZeroI8> for NonZeroI32

Converts NonZeroI8 to NonZeroI32 losslessly.

pub fn from(small: NonZeroI8) -> NonZeroI32

impl From<u8> for isize

Converts u8 to isize losslessly.

pub fn from(small: u8) -> isize

impl From<NonZeroU8> for NonZeroIsize

Converts NonZeroU8 to NonZeroIsize losslessly.

pub fn from(small: NonZeroU8) -> NonZeroIsize

impl From<bool> for u64

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);

pub fn from(small: bool) -> u64

impl From<NonZeroI8> for NonZeroI64

Converts NonZeroI8 to NonZeroI64 losslessly.

pub fn from(small: NonZeroI8) -> NonZeroI64

impl From<NonZeroU16> for NonZeroU32

Converts NonZeroU16 to NonZeroU32 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroU32

impl From<bool> for i32

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);

pub fn from(small: bool) -> i32

impl From<bool> for u16

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);

pub fn from(small: bool) -> u16

impl From<NonZeroU16> for NonZeroU128

Converts NonZeroU16 to NonZeroU128 losslessly.

pub fn from(small: NonZeroU16) -> NonZeroU128

impl From<i16> for AtomicI16

pub fn from(v: i16) -> AtomicI16

Converts an i16 into an AtomicI16.

impl From<!> for TryFromIntError

pub fn from(never: !) -> TryFromIntError

impl From<u8> for u128

Converts u8 to u128 losslessly.

pub fn from(small: u8) -> u128

impl From<u16> for i128

Converts u16 to i128 losslessly.

pub fn from(small: u16) -> i128

impl From<NonZeroI8> for NonZeroI16

Converts NonZeroI8 to NonZeroI16 losslessly.

pub fn from(small: NonZeroI8) -> NonZeroI16

impl<W> From<Arc<W>> for RawWaker where
    W: 'static + Wake + Send + Sync, 

pub fn from(waker: Arc<W>) -> RawWaker

impl<T> From<T> for Rc<T>

pub fn from(t: T) -> Rc<T>

impl From<String> for Arc<str>

pub fn from(v: String) -> Arc<str>

Allocate a reference-counted str and copy v into it.

Example

let unique: String = "eggplant".to_owned();
let shared: Arc<str> = Arc::from(unique);
assert_eq!("eggplant", &shared[..]);

impl<'_> From<&'_ str> for Arc<str>

pub fn from(v: &str) -> Arc<str>

Allocate a reference-counted str and copy v into it.

Example

let shared: Arc<str> = Arc::from("eggplant");
assert_eq!("eggplant", &shared[..]);

impl<'_, T> From<&'_ [T]> for Arc<[T]> where
    T: Clone, 

pub fn from(v: &[T]) -> Arc<[T]>

Allocate a reference-counted slice and fill it by cloning v’s items.

Example

let original: &[i32] = &[1, 2, 3];
let shared: Arc<[i32]> = Arc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<T> From<Box<T, Global>> for Rc<T> where
    T: ?Sized, 

pub fn from(v: Box<T, Global>) -> Rc<T>

Move a boxed object to a new, reference counted, allocation.

Example

let original: Box<i32> = Box::new(1);
let shared: Rc<i32> = Rc::from(original);
assert_eq!(1, *shared);

impl<'_> From<&'_ str> for Rc<str>

pub fn from(v: &str) -> Rc<str>

Allocate a reference-counted string slice and copy v into it.

Example

let shared: Rc<str> = Rc::from("statue");
assert_eq!("statue", &shared[..]);

impl<T, A> From<Box<T, A>> for Pin<Box<T, A>> where
    T: ?Sized,
    A: Allocator + 'static, 

pub fn from(boxed: Box<T, A>) -> Pin<Box<T, A>>

Converts a Box<T> into a Pin<Box<T>>

This conversion does not allocate on the heap and happens in place.

impl<T> From<Box<T, Global>> for Arc<T> where
    T: ?Sized, 

pub fn from(v: Box<T, Global>) -> Arc<T>

Move a boxed object to a new, reference-counted allocation.

Example

let unique: Box<str> = Box::from("eggplant");
let shared: Arc<str> = Arc::from(unique);
assert_eq!("eggplant", &shared[..]);

impl<'_, T> From<&'_ [T]> for Rc<[T]> where
    T: Clone, 

pub fn from(v: &[T]) -> Rc<[T]>

Allocate a reference-counted slice and fill it by cloning v’s items.

Example

let original: &[i32] = &[1, 2, 3];
let shared: Rc<[i32]> = Rc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<'a, B> From<Cow<'a, B>> for Rc<B> where
    B: ToOwned + ?Sized,
    Rc<B>: From<&'a B>,
    Rc<B>: From<<B as ToOwned>::Owned>, 

pub fn from(cow: Cow<'a, B>) -> Rc<B>

impl<T> From<T> for Arc<T>

pub fn from(t: T) -> Arc<T>

impl<T> From<Vec<T, Global>> for Rc<[T]>

pub fn from(v: Vec<T, Global>) -> Rc<[T]>

Allocate a reference-counted slice and move v’s items into it.

Example

let original: Box<Vec<i32>> = Box::new(vec![1, 2, 3]);
let shared: Rc<Vec<i32>> = Rc::from(original);
assert_eq!(vec![1, 2, 3], *shared);

impl From<String> for Rc<str>

pub fn from(v: String) -> Rc<str>

Allocate a reference-counted string slice and copy v into it.

Example

let original: String = "statue".to_owned();
let shared: Rc<str> = Rc::from(original);
assert_eq!("statue", &shared[..]);

impl<T> From<Vec<T, Global>> for Arc<[T]>

pub fn from(v: Vec<T, Global>) -> Arc<[T]>

Allocate a reference-counted slice and move v’s items into it.

Example

let unique: Vec<i32> = vec![1, 2, 3];
let shared: Arc<[i32]> = Arc::from(unique);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<'a, B> From<Cow<'a, B>> for Arc<B> where
    B: ToOwned + ?Sized,
    Arc<B>: From<&'a B>,
    Arc<B>: From<<B as ToOwned>::Owned>, 

pub fn from(cow: Cow<'a, B>) -> Arc<B>

impl<W> From<Arc<W>> for Waker where
    W: 'static + Wake + Send + Sync, 

pub fn from(waker: Arc<W>) -> Waker

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Implementors

impl From<char> for String

pub fn from(c: char) -> String

impl From<!> for Infallible

pub fn from(x: !) -> Infallible

impl From<LayoutError> for TryReserveError

pub fn from(LayoutError) -> TryReserveError

impl From<Box<str, Global>> for String

pub fn from(s: Box<str, Global>) -> String

Converts the given boxed str slice to a String. It is notable that the str slice is owned.

Examples

Basic usage:

let s1: String = String::from("hello world");
let s2: Box<str> = s1.into_boxed_str();
let s3: String = String::from(s2);

assert_eq!("hello world", s3)

impl From<String> for Box<str, Global>

pub fn from(s: String) -> Box<str, Global>

Converts the given String to a boxed str slice that is owned.

Examples

Basic usage:

let s1: String = String::from("hello world");
let s2: Box<str> = Box::from(s1);
let s3: String = String::from(s2);

assert_eq!("hello world", s3)

impl From<String> for Box<dyn Error + 'static + Sync + Send, Global>

pub fn from(err: String) -> Box<dyn Error + 'static + Sync + Send, Global>

Converts a String into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;
use std::mem;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))

impl From<String> for Box<dyn Error + 'static, Global>

pub fn from(str_err: String) -> Box<dyn Error + 'static, Global>

Converts a String into a box of dyn Error.

Examples

use std::error::Error;
use std::mem;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error>::from(a_string_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))

impl From<String> for Vec<u8, Global>

pub fn from(string: String) -> Vec<u8, Global>

Converts the given String to a vector Vec that holds values of type u8.

Examples

Basic usage:

let s1 = String::from("hello world");
let v1 = Vec::from(s1);

for b in v1 {
    println!("{}", b);
}

impl From<CString> for Box<CStr, Global>

pub fn from(s: CString) -> Box<CStr, Global>

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

impl From<CString> for Vec<u8, Global>

pub fn from(s: CString) -> Vec<u8, Global>

Converts a CString into a Vec<u8>.

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

impl From<OsString> for Box<OsStr, Global>

pub fn from(s: OsString) -> Box<OsStr, Global>

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

impl From<PathBuf> for Box<Path, Global>

pub fn from(p: PathBuf) -> Box<Path, Global>

Converts a PathBuf into a Box<Path>

This conversion currently should not allocate memory, but this behavior is not guaranteed on all platforms or in all future versions.

impl From<StreamResult> for Result<MZStatus, MZError>

pub fn from(res: StreamResult) -> Result<MZStatus, MZError>

impl<'_> From<&'_ str> for Box<str, Global>

pub fn from(s: &str) -> Box<str, Global>

Converts a &str into a Box<str>

This conversion allocates on the heap and performs a copy of s.

Examples

let boxed: Box<str> = Box::from("hello");
println!("{}", boxed);

impl<'_> From<&'_ str> for Box<dyn Error + 'static, Global>

pub fn from(err: &str) -> Box<dyn Error + 'static, Global>

Converts a str into a box of dyn Error.

Examples

use std::error::Error;
use std::mem;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error>::from(a_str_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))

impl<'_> From<&'_ str> for String

pub fn from(s: &str) -> String

impl<'_> From<&'_ str> for Vec<u8, Global>

pub fn from(s: &str) -> Vec<u8, Global>

Allocate a Vec<u8> and fill it with a UTF-8 string.

Examples

assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']);

impl<'_> From<&'_ String> for String

pub fn from(s: &String) -> String

impl<'_> From<&'_ CStr> for Box<CStr, Global>

pub fn from(s: &CStr) -> Box<CStr, Global>

impl<'_> From<&'_ OsStr> for Box<OsStr, Global>

pub fn from(s: &OsStr) -> Box<OsStr, Global>

impl<'_> From<&'_ Path> for Box<Path, Global>

pub fn from(path: &Path) -> Box<Path, Global>

impl<'_> From<&'_ StreamResult> for Result<MZStatus, MZError>

pub fn from(res: &StreamResult) -> Result<MZStatus, MZError>

impl<'_> From<&'_ mut str> for String

pub fn from(s: &mut str) -> String

Converts a &mut str into a String.

The result is allocated on the heap.

impl<'_> From<Cow<'_, str>> for Box<str, Global>

pub fn from(cow: Cow<'_, str>) -> Box<str, Global>

impl<'_> From<Cow<'_, CStr>> for Box<CStr, Global>

pub fn from(cow: Cow<'_, CStr>) -> Box<CStr, Global>

impl<'_> From<Cow<'_, OsStr>> for Box<OsStr, Global>

pub fn from(cow: Cow<'_, OsStr>) -> Box<OsStr, Global>

impl<'_> From<Cow<'_, Path>> for Box<Path, Global>

pub fn from(cow: Cow<'_, Path>) -> Box<Path, Global>

impl<'_, T> From<Cow<'_, [T]>> for Box<[T], Global> where
    T: Copy, 

pub fn from(cow: Cow<'_, [T]>) -> Box<[T], Global>

impl<'_, T> From<&'_ [T]> for Box<[T], Global> where
    T: Copy, 

pub fn from(slice: &[T]) -> Box<[T], Global>

Converts a &[T] into a Box<[T]>

This conversion allocates on the heap and performs a copy of slice.

Examples

// create a &[u8] which will be used to create a Box<[u8]>
let slice: &[u8] = &[104, 101, 108, 108, 111];
let boxed_slice: Box<[u8]> = Box::from(slice);

println!("{:?}", boxed_slice);

impl<'_, T> From<&'_ [T]> for Vec<T, Global> where
    T: Clone, 

pub fn from(s: &[T]) -> Vec<T, Global>

Allocate a Vec<T> and fill it by cloning s’s items.

Examples

assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]);

impl<'_, T> From<&'_ mut [T]> for Vec<T, Global> where
    T: Clone, 

pub fn from(s: &mut [T]) -> Vec<T, Global>

Allocate a Vec<T> and fill it by cloning s’s items.

Examples

assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]);

impl<'a> From<&'a str> for Cow<'a, str>

pub fn from(s: &'a str) -> Cow<'a, str>

Converts a string slice into a Borrowed variant. No heap allocation is performed, and the string is not copied.

Example

assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));

impl<'a> From<&'a String> for Cow<'a, str>

pub fn from(s: &'a String) -> Cow<'a, str>

Converts a String reference into a Borrowed variant. No heap allocation is performed, and the string is not copied.

Example

let s = "eggplant".to_string();
assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant"));

impl<'a> From<&'a CStr> for Cow<'a, CStr>

pub fn from(s: &'a CStr) -> Cow<'a, CStr>

impl<'a> From<&'a CString> for Cow<'a, CStr>

pub fn from(s: &'a CString) -> Cow<'a, CStr>

impl<'a> From<&'a OsStr> for Cow<'a, OsStr>

pub fn from(s: &'a OsStr) -> Cow<'a, OsStr>

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

pub fn from(s: &'a OsString) -> Cow<'a, OsStr>

impl<'a> From<&'a Path> for Cow<'a, Path>

pub fn from(s: &'a Path) -> Cow<'a, Path>

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

pub fn from(p: &'a PathBuf) -> Cow<'a, Path>

impl<'a> From<Cow<'a, str>> for Box<dyn Error + 'static, Global>

pub fn from(err: Cow<'a, str>) -> Box<dyn Error + 'static, Global>

Converts a Cow into a box of dyn Error.

Examples

use std::error::Error;
use std::mem;
use std::borrow::Cow;

let a_cow_str_error = Cow::from("a str error");
let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))

impl<'a> From<Cow<'a, str>> for String

pub fn from(s: Cow<'a, str>) -> String

impl<'a> From<String> for Cow<'a, str>

pub fn from(s: String) -> Cow<'a, str>

Converts a String into an Owned variant. No heap allocation is performed, and the string is not copied.

Example

let s = "eggplant".to_string();
let s2 = "eggplant".to_string();
assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2));

impl<'a> From<CString> for Cow<'a, CStr>

pub fn from(s: CString) -> Cow<'a, CStr>

impl<'a> From<OsString> for Cow<'a, OsStr>

pub fn from(s: OsString) -> Cow<'a, OsStr>

impl<'a> From<PathBuf> for Cow<'a, Path>

pub fn from(s: PathBuf) -> Cow<'a, Path>

impl<'a, '_> From<&'_ str> for Box<dyn Error + 'a + Sync + Send, Global>

pub fn from(err: &str) -> Box<dyn Error + 'a + Sync + Send, Global>

Converts a str into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;
use std::mem;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a + Sync + Send, Global>

pub fn from(err: Cow<'b, str>) -> Box<dyn Error + 'a + Sync + Send, Global>

Converts a Cow into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;
use std::mem;
use std::borrow::Cow;

let a_cow_str_error = Cow::from("a str error");
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))

impl<'a, E> From<E> for Box<dyn Error + 'a + Sync + Send, Global> where
    E: 'a + Error + Send + Sync, 

pub fn from(err: E) -> Box<dyn Error + 'a + Sync + Send, Global>

Converts a type of Error + Send + Sync into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;
use std::fmt;
use std::mem;

#[derive(Debug)]
struct AnError;

impl fmt::Display for AnError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f , "An error")
    }
}

impl Error for AnError {}

unsafe impl Send for AnError {}

unsafe impl Sync for AnError {}

let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))

impl<'a, E> From<E> for Box<dyn Error + 'a, Global> where
    E: 'a + Error, 

pub fn from(err: E) -> Box<dyn Error + 'a, Global>

Converts a type of Error into a box of dyn Error.

Examples

use std::error::Error;
use std::fmt;
use std::mem;

#[derive(Debug)]
struct AnError;

impl fmt::Display for AnError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f , "An error")
    }
}

impl Error for AnError {}

let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error>::from(an_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))

impl<'a, T> From<&'a Option<T>> for Option<&'a T>

pub fn from(o: &'a Option<T>) -> Option<&'a T>

Converts from &Option<T> to Option<&T>.

Examples

Converts an Option<String> into an Option<usize>, preserving the original. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let s: Option<String> = Some(String::from("Hello, Rustaceans!"));
let o: Option<usize> = Option::from(&s).map(|ss: &String| ss.len());

println!("Can still print s: {:?}", s);

assert_eq!(o, Some(18));

impl<'a, T> From<&'a Vec<T, Global>> for Cow<'a, [T]> where
    T: Clone, 

pub fn from(v: &'a Vec<T, Global>) -> Cow<'a, [T]>

impl<'a, T> From<&'a mut Option<T>> for Option<&'a mut T>

pub fn from(o: &'a mut Option<T>) -> Option<&'a mut T>

Converts from &mut Option<T> to Option<&mut T>

Examples

let mut s = Some(String::from("Hello"));
let o: Option<&mut String> = Option::from(&mut s);

match o {
    Some(t) => *t = String::from("Hello, Rustaceans!"),
    None => (),
}

assert_eq!(s, Some(String::from("Hello, Rustaceans!")));

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

pub fn from(s: Cow<'a, [T]>) -> Vec<T, Global>

Convert a clone-on-write slice into a vector.

If s already owns a Vec<T>, it will be returned directly. If s is borrowing a slice, a new Vec<T> will be allocated and filled by cloning s’s items into it.

Examples

let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
assert_eq!(Vec::from(o), Vec::from(b));

impl<'a, T> From<&'a [T]> for Cow<'a, [T]> where
    T: Clone, 

pub fn from(s: &'a [T]) -> Cow<'a, [T]>

impl<'a, T> From<Vec<T, Global>> for Cow<'a, [T]> where
    T: Clone, 

pub fn from(v: Vec<T, Global>) -> Cow<'a, [T]>

impl<A> From<Box<str, A>> for Box<[u8], A> where
    A: Allocator, 

pub fn from(s: Box<str, A>) -> Box<[u8], A>

Converts a Box<str> into a Box<[u8]>

This conversion does not allocate on the heap and happens in place.

Examples

// create a Box<str> which will be used to create a Box<[u8]>
let boxed: Box<str> = Box::from("hello");
let boxed_str: Box<[u8]> = Box::from(boxed);

// create a &[u8] which will be used to create a Box<[u8]>
let slice: &[u8] = &[104, 101, 108, 108, 111];
let boxed_slice = Box::from(slice);

assert_eq!(boxed_slice, boxed_str);

impl<T> From<!> for T

Stability note: This impl does not yet exist, but we are “reserving space” to add it in the future. See rust-lang/rust#64715 for details.

pub fn from(t: !) -> T

impl<T> From<BinaryHeap<T>> for Vec<T, Global>

pub fn from(heap: BinaryHeap<T>) -> Vec<T, Global>

Converts a BinaryHeap<T> into a Vec<T>.

This conversion requires no data movement or allocation, and has constant time complexity.

impl<T> From<VecDeque<T>> for Vec<T, Global>

pub fn from(other: VecDeque<T>) -> Vec<T, Global>

Turn a VecDeque<T> into a Vec<T>.

This never needs to re-allocate, but does need to do O(n) data movement if the circular buffer doesn’t happen to be at the beginning of the allocation.

Examples

use std::collections::VecDeque;

// This one is *O*(1).
let deque: VecDeque<_> = (1..5).collect();
let ptr = deque.as_slices().0.as_ptr();
let vec = Vec::from(deque);
assert_eq!(vec, [1, 2, 3, 4]);
assert_eq!(vec.as_ptr(), ptr);

// This one needs data rearranging.
let mut deque: VecDeque<_> = (1..5).collect();
deque.push_front(9);
deque.push_front(8);
let ptr = deque.as_slices().1.as_ptr();
let vec = Vec::from(deque);
assert_eq!(vec, [8, 9, 1, 2, 3, 4]);
assert_eq!(vec.as_ptr(), ptr);

impl<T> From<Vec<T, Global>> for BinaryHeap<T> where
    T: Ord, 

pub fn from(vec: Vec<T, Global>) -> BinaryHeap<T>

Converts a Vec<T> into a BinaryHeap<T>.

This conversion happens in-place, and has O(n) time complexity.

impl<T> From<Vec<T, Global>> for VecDeque<T>

pub fn from(other: Vec<T, Global>) -> VecDeque<T>

Turn a Vec<T> into a VecDeque<T>.

This avoids reallocating where possible, but the conditions for that are strict, and subject to change, and so shouldn’t be relied upon unless the Vec<T> came from From<VecDeque<T>> and hasn’t been reallocated.

impl<T> From<T> for Option<T>

pub fn from(val: T) -> Option<T>

Copies val into a new Some.

Examples

let o: Option<u8> = Option::from(67);

assert_eq!(Some(67), o);

impl<T> From<T> for Box<T, Global>

pub fn from(t: T) -> Box<T, Global>

Converts a generic type T into a Box<T>

The conversion allocates on the heap and moves t from the stack into it.

Examples

let x = 5;
let boxed = Box::new(5);

assert_eq!(Box::from(x), boxed);

impl<T> From<T> for T

pub fn from(t: T) -> T

impl<T, A> From<Box<[T], A>> for Vec<T, A> where
    A: Allocator, 

pub fn from(s: Box<[T], A>) -> Vec<T, A>

Convert a boxed slice into a vector by transferring ownership of the existing heap allocation.

Examples

let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice();
assert_eq!(Vec::from(b), vec![1, 2, 3]);

impl<T, A> From<Vec<T, A>> for Box<[T], A> where
    A: Allocator, 

pub fn from(v: Vec<T, A>) -> Box<[T], A>

Convert a vector into a boxed slice.

If v has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity.

Examples

assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());

impl<T, const N: usize> From<[T; N]> for Box<[T], Global>

pub fn from(array: [T; N]) -> Box<[T], Global>

Converts a [T; N] into a Box<[T]>

This conversion moves the array to newly heap-allocated memory.

Examples

let boxed: Box<[u8]> = Box::from([4, 2]);
println!("{:?}", boxed);

impl<T, const N: usize> From<[T; N]> for Vec<T, Global>

pub fn from(s: [T; N]) -> Vec<T, Global>

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