# Struct PhantomCovariant

Source

    pub struct PhantomCovariant<T>(/* private fields */)
    where
        T: ?Sized;

🔬This is a nightly-only experimental API. (`phantom_variance_markers` #135806)
Expand description

Zero-sized type used to mark a type parameter as covariant.

Types used as part of the return value from a function are covariant. If the type is also passed as a parameter then it is invariant. See the reference for more information.

Note: If `T` is otherwise contravariant or invariant, the resulting type is invariant.

### §Layout

For all `T`, the following are guaranteed:

- `size_of::<PhantomCovariant<T>>() == 0`
- `align_of::<PhantomCovariant<T>>() == 1`

## Implementations§

Source§

### impl<T> PhantomCovariant<T>
where T: ?Sized,

Source

#### pub const fn new() -> Self

🔬This is a nightly-only experimental API. (`phantom_variance_markers` #135806)

Constructs a new instance of the variance marker.

## Trait Implementations§

Source§

### impl<T> Clone for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn clone(&self) -> Self

Returns a duplicate of the value. Read more
1.0.0 · Source§

#### fn clone_from(&mut self, source: &Self)
where Self:,

Performs copy-assignment from `source`. Read more
Source§

### impl<T> Debug for PhantomCovariant<T>
where T: ?Sized,

Source§

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

Formats the value using the given formatter. Read more
Source§

### impl<T> Default for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn default() -> Self

Returns the “default value” for a type. Read more
Source§

### impl<T> Hash for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn hash<H: Hasher>(&self, _: &mut H)

Feeds this value into the given `Hasher`. Read more
1.3.0 · Source§

#### fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)
where Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
Source§

### impl<T> Ord for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn cmp(&self, _: &Self) -> Ordering

This method returns an `Ordering` between `self` and `other`. Read more
1.21.0 · Source§

#### fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 · Source§

#### fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 · Source§

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

Restrict a value to a certain interval. Read more
Source§

### impl<T> PartialEq for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn eq(&self, _: &Self) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
1.0.0 · Source§

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

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

### impl<T> PartialOrd for PhantomCovariant<T>
where T: ?Sized,

Source§

#### fn partial_cmp(&self, _: &Self) -> Option<Ordering>

This method returns an ordering between `self` and `other` values if one exists. Read more
1.0.0 · Source§

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

Tests less than (for `self` and `other`) and is used by the `<` operator. Read more
1.0.0 · Source§

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

Tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more
1.0.0 · Source§

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

Tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
1.0.0 · Source§

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

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

### impl<T> Copy for PhantomCovariant<T>
where T: ?Sized,

Source§

### impl<T> Eq for PhantomCovariant<T>
where T: ?Sized,

Source§

### impl<T> Variance for PhantomCovariant<T>
where T: ?Sized,

## Auto Trait Implementations§

§

### impl<T> Freeze for PhantomCovariant<T>
where T: ?Sized,

§

### impl<T> RefUnwindSafe for PhantomCovariant<T>
where T: ?Sized,

§

### impl<T> Send for PhantomCovariant<T>
where T: ?Sized,

§

### impl<T> Sync for PhantomCovariant<T>
where T: ?Sized,

§

### impl<T> Unpin for PhantomCovariant<T>
where T: ?Sized,

§

### impl<T> UnwindSafe for PhantomCovariant<T>
where T: ?Sized,

## Blanket Implementations§

Source§

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

Source§

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

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

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

Source§

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

Immutably borrows from an owned value. Read more
Source§

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

Source§

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

Mutably borrows from an owned value. Read more
Source§

### impl<T> CloneToUninit for T
where T: Clone,

Source§

#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
Source§

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

Source§

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

Returns the argument unchanged.

Source§

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

Source§

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

Calls `U::from(self)`.

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

Source§

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

Source§

#### type Error = Infallible

The type returned in the event of a conversion error.
Source§

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

Performs the conversion.
Source§

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

Source§

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

The type returned in the event of a conversion error.
Source§

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

Performs the conversion.