Type Alias FluentId

pub(crate) type FluentId = Cow<'static, str>;

Identifier for the Fluent message/attribute corresponding to a diagnostic message.

Aliased Type

enum FluentId {
    Borrowed(&'static str),
    Owned(String),
}

Variants

Borrowed(&'static str)

Borrowed data.

Owned(String)

Owned data.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 24 bytes

Size for each variant:

• Borrowed: 24 bytes
• Owned: 24 bytes

Implementations

impl<B> Cow<'_, B>

where B: ToOwned + ?Sized,

pub const fn is_borrowed(&self) -> bool

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

Returns true if the data is borrowed, i.e. if to_mut would require additional work.

Examples

#![feature(cow_is_borrowed)]
use std::borrow::Cow;

let cow = Cow::Borrowed("moo");
assert!(cow.is_borrowed());

let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
assert!(!bull.is_borrowed());

pub const fn is_owned(&self) -> bool

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

Returns true if the data is owned, i.e. if to_mut would be a no-op.

Examples

#![feature(cow_is_borrowed)]
use std::borrow::Cow;

let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
assert!(cow.is_owned());

let bull = Cow::Borrowed("...moo?");
assert!(!bull.is_owned());

pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned

Acquires a mutable reference to the owned form of the data.

Clones the data if it is not already owned.

Examples

use std::borrow::Cow;

let mut cow = Cow::Borrowed("foo");
cow.to_mut().make_ascii_uppercase();

assert_eq!(
  cow,
  Cow::Owned(String::from("FOO")) as Cow<'_, str>
);

pub fn into_owned(self) -> <B as ToOwned>::Owned

Extracts the owned data.

Clones the data if it is not already owned.

Examples

Calling into_owned on a Cow::Borrowed returns a clone of the borrowed data:

use std::borrow::Cow;

let s = "Hello world!";
let cow = Cow::Borrowed(s);

assert_eq!(
  cow.into_owned(),
  String::from(s)
);

Calling into_owned on a Cow::Owned returns the owned data. The data is moved out of the Cow without being cloned.

use std::borrow::Cow;

let s = "Hello world!";
let cow: Cow<'_, str> = Cow::Owned(String::from(s));

assert_eq!(
  cow.into_owned(),
  String::from(s)
);

Trait Implementations

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

type Output = Cow<'a, str>

The resulting type after applying the + operator.

fn add(self, rhs: &'a str) -> Cow<'a, str>

Performs the + operation.

impl<'a> Add for Cow<'a, str>

type Output = Cow<'a, str>

The resulting type after applying the + operator.

fn add(self, rhs: Cow<'a, str>) -> Cow<'a, str>

Performs the + operation.

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

fn add_assign(&mut self, rhs: &'a str)

Performs the += operation.

impl<'a> AddAssign for Cow<'a, str>

fn add_assign(&mut self, rhs: Cow<'a, str>)

Performs the += operation.

impl<'a> Arg for Cow<'a, str>

fn as_str(&self) -> Result<&str, Errno>

Returns a view of this string as a string slice.

fn to_string_lossy(&self) -> Cow<'_, str>

Returns a potentially-lossy rendering of this string as a Cow<'_, str>.

fn as_cow_c_str(&self) -> Result<Cow<'_, CStr>, Errno>

Returns a view of this string as a maybe-owned CStr.

fn into_c_str<'b>(self) -> Result<Cow<'b, CStr>, Errno>

where Cow<'a, str>: 'b,

Consumes self and returns a view of this string as a maybe-owned CStr.

fn into_with_c_str<T, F>(self, f: F) -> Result<T, Errno>

where Cow<'a, str>: Sized, F: FnOnce(&CStr) -> Result<T, Errno>,

Runs a closure with self passed in as a &CStr.

impl<T> AsRef<T> for Cow<'_, T>

where T: ToOwned + ?Sized,

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<'a, B> Borrow<B> for Cow<'a, B>

where B: ToOwned + ?Sized,

fn borrow(&self) -> &B

Immutably borrows from an owned value.

impl<B> Clone for Cow<'_, B>

where B: ToOwned + ?Sized,

fn clone(&self) -> Cow<'_, B>

Returns a copy of the value.

fn clone_from(&mut self, source: &Cow<'_, B>)

Performs copy-assignment from source.

impl<B> Debug for Cow<'_, B>

where B: Debug + ToOwned + ?Sized, <B as ToOwned>::Owned: Debug,

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

Formats the value using the given formatter.

impl<D> Decodable<D> for Cow<'_, str>

where D: Decoder,

fn decode(d: &mut D) -> Cow<'static, str>

impl<B> Default for Cow<'_, B>

where B: ToOwned + ?Sized, <B as ToOwned>::Owned: Default,

fn default() -> Cow<'_, B>

Creates an owned Cow<’a, B> with the default value for the contained owned value.

impl<B> Deref for Cow<'_, B>

where B: ToOwned + ?Sized, <B as ToOwned>::Owned: Borrow<B>,

type Target = B

The resulting type after dereferencing.

fn deref(&self) -> &B

Dereferences the value.

impl<B> Display for Cow<'_, B>

where B: Display + ToOwned + ?Sized, <B as ToOwned>::Owned: Display,

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

Formats the value using the given formatter.

impl<S> Encodable<S> for Cow<'_, str>

where S: Encoder,

fn encode(&self, s: &mut S)

impl<T> EncodeAsVarULE<T> for Cow<'_, T>

where T: VarULE + ToOwned + ?Sized,

fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R

Calls cb with a piecewise list of byte slices that when concatenated produce the memory pattern of the corresponding instance of T.

fn encode_var_ule_len(&self) -> usize

Return the length, in bytes, of the corresponding VarULE type

fn encode_var_ule_write(&self, dst: &mut [u8])

Write the corresponding VarULE type to the dst buffer. dst should be the size of Self::encode_var_ule_len()

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

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 str> for Cow<'a, str>

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<String> for Cow<'a, str>

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, 'b> FromIterator<&'b str> for Cow<'a, str>

fn from_iter<I>(it: I) -> Cow<'a, str>

where I: IntoIterator<Item = &'b str>,

Creates a value from an iterator.

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

fn from_iter<I>(it: I) -> Cow<'a, str>

where I: IntoIterator<Item = String>,

Creates a value from an iterator.

impl<'a> FromIterator<char> for Cow<'a, str>

fn from_iter<I>(it: I) -> Cow<'a, str>

where I: IntoIterator<Item = char>,

Creates a value from an iterator.

impl<'a, C, T> FromParallelIterator<T> for Cow<'a, C>

where C: ToOwned + ?Sized, <C as ToOwned>::Owned: FromParallelIterator<T>, T: Send,

Collects an arbitrary Cow collection.

Note, the standard library only has FromIterator for Cow<'a, str> and Cow<'a, [T]>, because no one thought to add a blanket implementation before it was stabilized.

fn from_par_iter<I>(par_iter: I) -> Cow<'a, C>

where I: IntoParallelIterator<Item = T>,

Creates an instance of the collection from the parallel iterator par_iter.

impl<B> Hash for Cow<'_, B>

where B: Hash + ToOwned + ?Sized,

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

where H: Hasher,

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<B> Ord for Cow<'_, B>

where B: Ord + ToOwned + ?Sized,

fn cmp(&self, other: &Cow<'_, B>) -> Ordering

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

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

where Self: Sized,

Restrict a value to a certain interval.

impl<'a, 'b> PartialEq<&'b str> for Cow<'a, str>

fn eq(&self, other: &&'b str) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&'b str) -> bool

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

impl<'a, 'b, B, C> PartialEq<Cow<'b, C>> for Cow<'a, B>

where B: PartialEq<C> + ToOwned + ?Sized, C: ToOwned + ?Sized,

fn eq(&self, other: &Cow<'b, C>) -> bool

Tests for self and other values to be equal, and is used by ==.

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

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

impl<'a, 'b> PartialEq<String> for Cow<'a, str>

fn eq(&self, other: &String) -> bool

Tests for self and other values to be equal, and is used by ==.

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

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

impl<'a, 'b> PartialEq<str> for Cow<'a, str>

fn eq(&self, other: &str) -> bool

Tests for self and other values to be equal, and is used by ==.

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

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

impl<'a, B> PartialOrd for Cow<'a, B>

where B: PartialOrd + ToOwned + ?Sized,

fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering>

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

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl<'a, T> Writeable for Cow<'a, T>

where T: Writeable + ToOwned + ?Sized,

fn write_to<W>(&self, sink: &mut W) -> Result<(), Error>

where W: Write + ?Sized,

Writes a string to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to_parts, and discards any Part annotations.

fn write_to_parts<W>(&self, sink: &mut W) -> Result<(), Error>

where W: PartsWrite + ?Sized,

Write bytes and Part annotations to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to, and doesn’t produce any Part annotations.

fn writeable_length_hint(&self) -> LengthHint

Returns a hint for the number of UTF-8 bytes that will be written to the sink.

fn write_to_string(&self) -> Cow<'_, str>

Creates a new String with the data from this Writeable. Like ToString, but smaller and faster.

fn writeable_cmp_bytes(&self, other: &[u8]) -> Ordering

Compares the contents of this Writeable to the given bytes without allocating a String to hold the Writeable contents.

impl<'a, T> Yokeable<'a> for Cow<'static, T>

where T: 'static + ToOwned + ?Sized, <T as ToOwned>::Owned: Sized,

type Output = Cow<'a, T>

This type MUST be Self with the 'static replaced with 'a, i.e. Self<'a>

fn transform(&'a self) -> &'a Cow<'a, T>

This method must cast self between &'a Self<'static> and &'a Self<'a>.

fn transform_owned(self) -> Cow<'a, T>

This method must cast self between Self<'static> and Self<'a>.

unsafe fn make(from: Cow<'a, T>) -> Cow<'static, T>

This method can be used to cast away Self<'a>’s lifetime.

fn transform_mut<F>(&'a mut self, f: F)

where F: 'static + for<'b> FnOnce(&'b mut Cow<'a, T>),

This method must cast self between &'a mut Self<'static> and &'a mut Self<'a>, and pass it to f.

impl<'zf, B> ZeroFrom<'zf, Cow<'_, B>> for Cow<'zf, B>

where B: ToOwned + ?Sized,

fn zero_from(other: &'zf Cow<'_, B>) -> Cow<'zf, B>

Clone the other C into a struct that may retain references into C.

impl<'zf> ZeroFrom<'zf, String> for Cow<'zf, str>

fn zero_from(other: &'zf String) -> Cow<'zf, str>

Clone the other C into a struct that may retain references into C.

impl<'zf> ZeroFrom<'zf, str> for Cow<'zf, str>

fn zero_from(other: &'zf str) -> Cow<'zf, str>

Clone the other C into a struct that may retain references into C.

impl<B> DerefPure for Cow<'_, B>

where B: ToOwned + ?Sized, <B as ToOwned>::Owned: Borrow<B>,

impl<B> Eq for Cow<'_, B>

where B: Eq + ToOwned + ?Sized,