# Union std::mem::ManuallyDrop 1.20.0 [−] [src]

    pub union ManuallyDrop<T> {
        // some fields omitted
    }

A wrapper to inhibit compiler from automatically calling `T`’s destructor.

This wrapper is 0-cost.

# Examples

This wrapper helps with explicitly documenting the drop order dependencies between fields of the type:

    use std::mem::ManuallyDrop;
    struct Peach;
    struct Banana;
    struct Melon;
    struct FruitBox {
        // Immediately clear there’s something non-trivial going on with these fields.
        peach: ManuallyDrop<Peach>,
        melon: Melon, // Field that’s independent of the other two.
        banana: ManuallyDrop<Banana>,
    }

    impl Drop for FruitBox {
        fn drop(&mut self) {
            unsafe {
                // Explicit ordering in which field destructors are run specified in the intuitive
                // location – the destructor of the structure containing the fields.
                // Moreover, one can now reorder fields within the struct however much they want.
                ManuallyDrop::drop(&mut self.peach);
                ManuallyDrop::drop(&mut self.banana);
            }
            // After destructor for `FruitBox` runs (this function), the destructor for Melon gets
            // invoked in the usual manner, as it is not wrapped in `ManuallyDrop`.
        }
    }Run

## Methods

### `impl<T> ManuallyDrop<T>`
[src]

#### `fn new(value: T) -> ManuallyDrop<T>`
[src]

Wrap a value to be manually dropped.

# Examples

    use std::mem::ManuallyDrop;
    ManuallyDrop::new(Box::new(()));Run

#### `fn into_inner(slot: ManuallyDrop<T>) -> T`
[src]

Extract the value from the ManuallyDrop container.

# Examples

    use std::mem::ManuallyDrop;
    let x = ManuallyDrop::new(Box::new(()));
    let _: Box<()> = ManuallyDrop::into_inner(x);Run

#### `unsafe fn drop(slot: &mut ManuallyDrop<T>)`
[src]

Manually drops the contained value.

# Safety

This function runs the destructor of the contained value and thus the wrapped value now represents uninitialized data. It is up to the user of this method to ensure the uninitialized data is not actually used.

## Trait Implementations

### `impl<T> Default for ManuallyDrop<T> where
T: Default,`
[src]

#### `fn default() -> ManuallyDrop<T>`
[src]

Returns the "default value" for a type. Read more

### `impl<T> Hash for ManuallyDrop<T> where
T: Hash,`
[src]

#### `fn hash<H>(&self, state: &mut H) where
H: Hasher,`
[src]

Feeds this value into the given [`Hasher`]. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,`
1.3.0
[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl<T> Clone for ManuallyDrop<T> where
T: Clone,`
[src]

#### `fn clone(&self) -> ManuallyDrop<T>`
[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &ManuallyDrop<T>)`
[src]

Performs copy-assignment from `source`. Read more

### `impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialEq<T>,`
[src]

#### `fn eq(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `fn ne(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests for `!=`.

### `impl<T> Ord for ManuallyDrop<T> where
T: Ord,`
[src]

#### `fn cmp(&self, other: &ManuallyDrop<T>) -> Ordering`
[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `fn max(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the minimum of two values. Read more

### `impl<T> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T> where
T: PartialOrd<T>,`
[src]

#### `fn partial_cmp(&self, other: &ManuallyDrop<T>) -> Option<Ordering>`
[src]

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

#### `fn lt(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

#### `fn le(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

#### `fn gt(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

#### `fn ge(&self, other: &ManuallyDrop<T>) -> bool`
[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

### `impl<T> Copy for ManuallyDrop<T> where
T: Copy,`
[src]

### `impl<T> Deref for ManuallyDrop<T>`
[src]

#### `type Target = T`

The resulting type after dereferencing.

#### `fn deref(&self) -> &<ManuallyDrop<T> as Deref>::Target`
[src]

Dereferences the value.

### `impl<T> DerefMut for ManuallyDrop<T>`
[src]

#### `fn deref_mut(&mut self) -> &mut <ManuallyDrop<T> as Deref>::Target`
[src]

Mutably dereferences the value.

### `impl<T> Debug for ManuallyDrop<T> where
T: Debug,`
[src]

#### `fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>`
[src]

Formats the value using the given formatter.

### `impl<T> Eq for ManuallyDrop<T> where
T: Eq,`
[src]

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