# 1.0.0[−][src]Trait std::convert::AsRef

    pub trait AsRef<T> where
        T: ?Sized, {
        fn as_ref(&self) -> &T;
    }

A cheap reference-to-reference conversion. Used to convert a value to a reference value within generic code.

`AsRef` is very similar to, but serves a slightly different purpose than, `Borrow`.

`AsRef` is to be used when wishing to convert to a reference of another type. `Borrow` is more related to the notion of taking the reference. It is useful when wishing to abstract over the type of reference (`&T`, `&mut T`) or allow both the referenced and owned type to be treated in the same manner.

The key difference between the two traits is the intention:

- Use `AsRef` when the goal is to simply convert into a reference
- Use `Borrow` when the goal is related to writing code that is agnostic to the type of borrow and whether it is a reference or value

See the book for a more detailed comparison.

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

# Generic Implementations

- `AsRef` auto-dereferences if the inner type is a reference or a mutable reference (e.g.: `foo.as_ref()` will work the same if `foo` has type `&mut Foo` or `&&mut Foo`)

# Examples

Both `String` and `&str` implement `AsRef<str>`:

    fn is_hello<T: AsRef<str>>(s: T) {
       assert_eq!("hello", s.as_ref());
    }

    let s = "hello";
    is_hello(s);

    let s = "hello".to_string();
    is_hello(s);Run

## Required Methods

ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

### `fn as_ref(&self) -> &T`

Performs the conversion.

## Implementors

###

`impl AsRef<[u8]> for str`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[u8]`

[src]

###

`impl AsRef<[u8]> for String`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[u8]`

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`impl AsRef<str> for str`

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`fn as_ref(&self) -> &str`

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`impl AsRef<str> for String`

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`fn as_ref(&self) -> &str`

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`impl AsRef<CStr> for CStr`

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`fn as_ref(&self) -> &CStr`

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`impl AsRef<CStr> for CString`

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`fn as_ref(&self) -> &CStr`

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`impl AsRef<OsStr> for str`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<OsStr> for OsStr`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<OsStr> for OsString`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<OsStr> for Path`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<OsStr> for PathBuf`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<OsStr> for String`

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`fn as_ref(&self) -> &OsStr`

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`impl AsRef<Path> for str`

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`fn as_ref(&self) -> &Path`

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`impl AsRef<Path> for OsStr`

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`fn as_ref(&self) -> &Path`

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`impl AsRef<Path> for OsString`

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`fn as_ref(&self) -> &Path`

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`impl AsRef<Path> for Path`

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`fn as_ref(&self) -> &Path`

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`impl AsRef<Path> for PathBuf`

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`fn as_ref(&self) -> &Path`

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`impl AsRef<Path> for String`

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`fn as_ref(&self) -> &Path`

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`impl<'_, T> AsRef<[T]> for std::slice::Iter<'_, T>`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<'_, T, U> AsRef<U> for &'_ T where T: AsRef<U> + ?Sized, U: ?Sized,`

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####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &U`

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###

`impl<'_, T, U> AsRef<U> for &'_ mut T where T: AsRef<U> + ?Sized, U: ?Sized,`

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####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &U`

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###

`impl<'a> AsRef<OsStr> for Component<'a>`

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`fn as_ref(&self) -> &OsStr`

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`impl<'a> AsRef<OsStr> for Components<'a>`

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`fn as_ref(&self) -> &OsStr`

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###

`impl<'a> AsRef<OsStr> for std::path::Iter<'a>`

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####

`fn as_ref(&self) -> &OsStr`

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###

`impl<'a> AsRef<Path> for Cow<'a, OsStr>`

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####

`fn as_ref(&self) -> &Path`

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###

`impl<'a> AsRef<Path> for Component<'a>`

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####

`fn as_ref(&self) -> &Path`

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###

`impl<'a> AsRef<Path> for Components<'a>`

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`fn as_ref(&self) -> &Path`

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`impl<'a> AsRef<Path> for std::path::Iter<'a>`

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`fn as_ref(&self) -> &Path`

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###

`impl<'a, T> AsRef<T> for Cow<'a, T> where T: ToOwned + ?Sized,`

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####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &T`

[src]

###

`impl<T> AsRef<[T]> for [T; 0]`

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####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 1]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 2]`

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####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

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`impl<T> AsRef<[T]> for [T; 3]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 4]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

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`impl<T> AsRef<[T]> for [T; 5]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

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`impl<T> AsRef<[T]> for [T; 6]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 7]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

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`impl<T> AsRef<[T]> for [T; 8]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 9]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 10]`

[src]

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 11]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 12]`

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ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 13]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 14]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 15]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 16]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 17]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 18]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 19]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 20]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 21]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 22]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 23]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 24]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 25]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 26]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 27]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 28]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 29]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 30]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 31]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T; 32]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for [T]`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<[T]> for Vec<T>`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[T]`

[src]

###

`impl<T> AsRef<Vec<T>> for Vec<T>`

[src]

####
ⓘImportant traits for Vec<u8>

### Important traits for Vec<u8>

`impl Write for Vec<u8>`

`fn as_ref(&self) -> &Vec<T>`

[src]

###

`impl<T> AsRef<T> for Box<T> where T: ?Sized,`

[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &T`

[src]

###

`impl<T> AsRef<T> for Rc<T> where T: ?Sized,`

[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &T`

[src]

###

`impl<T> AsRef<T> for Arc<T> where T: ?Sized,`

[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn as_ref(&self) -> &T`

[src]

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