Struct PhantomCovariant

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

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

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.

Layout

For all T, the following are guaranteed:

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

Implementations

impl<T> PhantomCovariant<T>

where T: ?Sized,

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

impl<T> Clone for PhantomCovariant<T>

where T: ?Sized,

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T> Debug for PhantomCovariant<T>

where T: ?Sized,

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

Formats the value using the given formatter.

impl<T> Default for PhantomCovariant<T>

where T: ?Sized,

fn default() -> Self

Returns the “default value” for a type.

impl<T> Hash for PhantomCovariant<T>

where T: ?Sized,

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

Feeds this value into the given Hasher.

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

where Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> Ord for PhantomCovariant<T>

where T: ?Sized,

fn cmp(&self, _: &Self) -> 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<T> PartialEq for PhantomCovariant<T>

where T: ?Sized,

fn eq(&self, _: &Self) -> 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<T> PartialOrd for PhantomCovariant<T>

where T: ?Sized,

fn partial_cmp(&self, _: &Self) -> 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<T> Copy for PhantomCovariant<T>

where T: ?Sized,

impl<T> Eq for PhantomCovariant<T>

where T: ?Sized,

impl<T> Variance for PhantomCovariant<T>

where T: ?Sized,