Struct swim_structure::item::Item

#[repr(C)]
pub struct Item<'a> { /* fields omitted */ }

Union of Field and Value representing a member of a Record.

Methods

impl<'a> Item<'a>

pub fn attr(key: Text<'a>, val: Value<'a>) -> Item<'a>

pub fn slot(key: Value<'a>, val: Value<'a>) -> Item<'a>

pub const fn from_u8(value: u8) -> Item<'a>

Constructs a new Item from a u8 value.

pub const fn from_i8(value: i8) -> Item<'a>

Constructs a new Item from an i8 value.

pub const fn from_u16(value: u16) -> Item<'a>

Constructs a new Item from a u16 value.

pub const fn from_i16(value: i16) -> Item<'a>

Constructs a new Item from an i16 value.

pub const fn from_u32(value: u32) -> Item<'a>

Constructs a new Item from a u32 value.

pub const fn from_i32(value: i32) -> Item<'a>

Constructs a new Item from an i32 value.

pub const fn from_u64(value: u64) -> Item<'a>

Constructs a new Item from a u64 value.

pub const fn from_i64(value: i64) -> Item<'a>

Constructs a new Item from an i64 value.

pub fn from_f16(value: f16) -> Item<'a>

Constructs a new Item from an f16 value.

pub fn from_f32(value: f32) -> Item<'a>

Constructs a new Item from an f32 value.

pub fn from_f64(value: f64) -> Item<'a>

Constructs a new Item from an f64 value.

pub const fn from_usize(value: usize) -> Item<'a>

Constructs a new Item from a usize value.

pub const fn from_isize(value: isize) -> Item<'a>

Constructs a new Item from an isize value.

pub const fn from_bool(value: bool) -> Item<'a>

Constructs a new Item from a bool value.

pub const fn extant() -> Item<'a>

Constructs a new extant Item.

pub const fn absent() -> Item<'a>

Constructs a new absent Item.

pub fn get_key(&self) -> &Option<Value<'a>>

Returns a reference to this Item's optional key.

pub fn get_key_mut(&mut self) -> &mut Option<Value<'a>>

Returns a mutable reference to this Item's optional key.

pub unsafe fn get_key_unchecked(&self) -> &Value<'a>

Returns a reference to this Item's key.

Safety

Does not verify that this Item's key is defined.

pub unsafe fn get_key_unchecked_mut(&mut self) -> &mut Value<'a>

Returns a mutable reference to this Item's key.

Safety

Does not verify that this Item's key is defined.

pub fn get_val(&self) -> &Value<'a>

Returns a reference to this Item's value.

pub fn get_val_mut(&mut self) -> &mut Value<'a>

Returns a mutable reference to this Item's value.

pub fn get_key_val(&self) -> (&Option<Value<'a>>, &Value<'a>)

Returns a pair of references to this Item's optional key and value.

pub fn get_key_val_mut(&mut self) -> (&mut Option<Value<'a>>, &mut Value<'a>)

Returns a pair of mutable references to this Item's optional key and value.

pub fn into_key(self) -> Option<Value<'a>>

Returns this Item's key, dropping its value.

pub fn into_val(self) -> Value<'a>

Returns this Item's value, dropping its optional key.

pub fn into_key_val(self) -> (Option<Value<'a>>, Value<'a>)

Returns this Item's optional key and value as a pair.

pub fn is_defined(&self) -> bool

Returns true if this Item is not Absent.

pub fn is_field(&self) -> bool

Returns true if this Item is a Field.

pub fn is_attr(&self) -> bool

Returns true if this Item is an Attr.

pub fn is_slot(&self) -> bool

Returns true if this Item is a Slot.

pub fn is_value(&self) -> bool

Returns true if this Item is a Value.

pub fn is_record(&self) -> bool

Returns true if this Item is a Record.

pub fn is_data(&self) -> bool

Returns true if this Item is Data.

pub fn is_text(&self) -> bool

Returns true if this Item is Text.

pub fn is_num(&self) -> bool

Returns true if this Item is a Num.

pub fn is_bool(&self) -> bool

Returns true if this Item is a Bool.

pub fn is_extant(&self) -> bool

Returns true if this Item is Extant.

pub fn is_absent(&self) -> bool

Returns true if this Item is Absent.

pub fn as_field(&self) -> &Field<'a>

Downcasts this Item reference to a Field reference.

Panics

Panics if this Item is not, in fact, a Field.

pub fn as_mut_field(&mut self) -> &mut Field<'a>

Downcasts this Item reference to a mutable Field reference.

Panics

Panics if this Item is not, in fact, a Field.

pub fn as_attr(&self) -> &Attr<'a>

Downcasts this Item reference to an Attr reference.

Panics

Panics if this Item is not, in fact, an Attr.

pub fn as_mut_attr(&mut self) -> &mut Attr<'a>

Downcasts this Item reference to a mutable Attr reference.

Panics

Panics if this Item is not, in fact, an Attr.

pub fn as_slot(&self) -> &Slot<'a>

Downcasts this Item reference to a Slot reference.

Panics

Panics if this Item is not, in fact, a Slot.

pub fn as_mut_slot(&mut self) -> &mut Slot<'a>

Downcasts this Item reference to a mutable Slot reference.

Panics

Panics if this Item is not, in fact, a Slot.

pub fn as_value(&self) -> &Value<'a>

Downcasts this Item reference to a Value reference.

Panics

Panics if this Item is not, in fact, a Value.

pub fn as_mut_value(&mut self) -> &mut Value<'a>

Downcasts this Item reference to a mutable Value reference.

Panics

Panics if this Item is not, in fact, a Value.

pub fn as_record(&self) -> &Record<'a>

Downcasts this Item reference to a Record reference.

Panics

Panics if this Item is not, in fact, a Record.

pub fn as_mut_record(&mut self) -> &mut Record<'a>

Downcasts this Item reference to a mutable Record reference.

Panics

Panics if this Item is not, in fact, a Record.

pub fn as_data(&self) -> &Data<'a>

Downcasts this Item reference to a Data reference.

Panics

Panics if this Item is not, in fact, Data.

pub fn as_mut_data(&mut self) -> &mut Data<'a>

Downcasts this Item reference to a mutable Data reference.

Panics

Panics if this Item is not, in fact, Data.

pub fn as_text(&self) -> &Text<'a>

Downcasts this Item reference to a Text reference.

Panics

Panics if this Item is not, in fact, Text.

pub fn as_mut_text(&mut self) -> &mut Text<'a>

Downcasts this Item reference to a mutable Text reference.

Panics

Panics if this Item is not, in fact, Text.

pub fn as_num(&self) -> &Num<'a>

Downcasts this Item reference to a Num reference.

Panics

Panics if this Item is not, in fact, a Num.

pub fn as_mut_num(&mut self) -> &mut Num<'a>

Downcasts this Item reference to a mutable Num reference.

Panics

Panics if this Item is not, in fact, a Num.

pub fn as_bool(&self) -> &Bool

Downcasts this Item reference to a Bool reference.

Panics

Panics if this Item is not, in fact, a Bool.

pub fn as_mut_bool(&mut self) -> &mut Bool

Downcasts this Item reference to a mutable Bool reference.

Panics

Panics if this Item is not, in fact, a Bool.

pub fn as_extant(&self) -> &Extant

Downcasts this Item reference to an Extant reference.

Panics

Panics if this Item is not, in fact, Extant.

pub fn as_absent(&self) -> &Absent

Downcasts this Item reference to an Absent reference.

Panics

Panics if this Item is not, in fact, Absent.

pub unsafe fn as_field_unchecked(&self) -> &Field<'a>

Reinterprets this Item reference as an Field reference.

Safety

Does not verify that this Item is, in fact, an Field.

pub unsafe fn as_mut_field_unchecked(&mut self) -> &mut Field<'a>

Reinterprets this Item reference as a mutable Field reference.

Safety

Does not verify that this Item is, in fact, an Field.

pub unsafe fn as_attr_unchecked(&self) -> &Attr<'a>

Reinterprets this Item reference as an Attr reference.

Safety

Does not verify that this Item is, in fact, an Attr.

pub unsafe fn as_mut_attr_unchecked(&mut self) -> &mut Attr<'a>

Reinterprets this Item reference as a mutable Attr reference.

Safety

Does not verify that this Item is, in fact, an Attr.

pub unsafe fn as_slot_unchecked(&self) -> &Slot<'a>

Reinterprets this Item reference as a Slot reference.

Safety

Does not verify that this Item is, in fact, a Slot.

pub unsafe fn as_mut_slot_unchecked(&mut self) -> &mut Slot<'a>

Reinterprets this Item reference as a mutable Slot reference.

Safety

Does not verify that this Item is, in fact, a Slot.

pub unsafe fn as_record_unchecked(&self) -> &Record<'a>

Reinterprets this Item reference as a Record reference.

Safety

Does not verify that this Item is, in fact, a Record.

pub unsafe fn as_mut_record_unchecked(&mut self) -> &mut Record<'a>

Reinterprets this Item reference as a mutable Record reference.

Safety

Does not verify that this Item is, in fact, a Record.

pub unsafe fn as_data_unchecked(&self) -> &Data<'a>

Reinterprets this Item reference as a Data reference.

Safety

Does not verify that this Item is, in fact, Data.

pub unsafe fn as_mut_data_unchecked(&mut self) -> &mut Data<'a>

Reinterprets this Item reference as a mutable Data reference.

Safety

Does not verify that this Item is, in fact, Data.

pub unsafe fn as_text_unchecked(&self) -> &Text<'a>

Reinterprets this Item reference as a Text reference.

Safety

Does not verify that this Item is, in fact, Text.

pub unsafe fn as_mut_text_unchecked(&mut self) -> &mut Text<'a>

Reinterprets this Item reference as a Text reference.

Safety

Does not verify that this Item is, in fact, Text.

pub unsafe fn as_num_unchecked(&self) -> &Num<'a>

Reinterprets this Item reference as a Num reference.

Safety

Does not verify that this Item is, in fact, a Num.

pub unsafe fn as_mut_num_unchecked(&mut self) -> &mut Num<'a>

Reinterprets this Item reference as a Num reference.

Safety

Does not verify that this Item is, in fact, a Num.

pub unsafe fn as_bool_unchecked(&self) -> &Bool

Reinterprets this Item reference as a Bool reference.

Safety

Does not verify that this Item is, in fact, a Bool.

pub unsafe fn as_mut_bool_unchecked(&mut self) -> &mut Bool

Reinterprets this Item reference as a Bool reference.

Safety

Does not verify that this Item is, in fact, a Bool.

pub unsafe fn as_extant_unchecked(&self) -> &Extant

Reinterprets this Item reference as an Extant reference.

Safety

Does not verify that this Item is, in fact, Extant.

pub unsafe fn as_absent_unchecked(&self) -> &Absent

Reinterprets this Item reference as an Absent reference.

Safety

Does not verify that this Item is, in fact, Absent.

pub fn into_field(self) -> Field<'a>

Downcasts this Item to a Field.

Panics

Panics if this Item is not, in fact, a Field.

pub fn into_attr(self) -> Attr<'a>

Downcasts this Item to an Attr.

Panics

Panics if this Item is not, in fact, an Attr.

pub fn into_slot(self) -> Slot<'a>

Downcasts this Item to a Slot.

Panics

Panics if this Item is not, in fact, a Slot.

pub fn into_value(self) -> Value<'a>

Downcasts this Item to a Value.

Panics

Panics if this Item is not, in fact, a Value.

pub fn into_record(self) -> Record<'a>

Downcasts this Item to a Record.

Panics

Panics if this Item is not, in fact, a Record.

pub fn into_data(self) -> Data<'a>

Downcasts this Item to Data.

Panics

Panics if this Item is not, in fact, Data.

pub fn into_text(self) -> Text<'a>

Downcasts this Item to Text.

Panics

Panics if this Item is not, in fact, Text.

pub fn into_num(self) -> Num<'a>

Downcasts this Item to a Num.

Panics

Panics if this Item is not, in fact, a Num.

pub fn into_bool(self) -> Bool

Downcasts this Item to a Bool.

Panics

Panics if this Item is not, in fact, a Bool.

pub fn into_extant(self) -> Extant

Downcasts this Item to Extant.

Panics

Panics if this Item is not, in fact, Extant.

pub fn into_absent(self) -> Absent

Downcasts this Item to Absent.

Panics

Panics if this Item is not, in fact, Absent.

pub unsafe fn into_field_unchecked(self) -> Field<'a>

Reinterprets this Item as a Field.

Safety

Does not verify that this Item is, in fact, a Field.

pub unsafe fn into_attr_unchecked(self) -> Attr<'a>

Reinterprets this Item as an Attr.

Safety

Does not verify that this Item is, in fact, an Attr.

pub unsafe fn into_slot_unchecked(self) -> Slot<'a>

Reinterprets this Item as a Slot.

Safety

Does not verify that this Item is, in fact, a Slot.

pub unsafe fn into_record_unchecked(self) -> Record<'a>

Reinterprets this Value as a Record.

Safety

Does not verify that this Value is, in fact, a Record.

pub unsafe fn into_data_unchecked(self) -> Data<'a>

Reinterprets this Value as Data.

Safety

Does not verify that this Value is, in fact, Data.

pub unsafe fn into_text_unchecked(self) -> Text<'a>

Reinterprets this Value as Text.

Safety

Does not verify that this Value is, in fact, Text.

pub unsafe fn into_num_unchecked(self) -> Num<'a>

Reinterprets this Value as a Num.

Safety

Does not verify that this Value is, in fact, a Num.

pub unsafe fn into_bool_unchecked(self) -> Bool

Reinterprets this Value as a Bool.

Safety

Does not verify that this Value is, in fact, a Bool.

pub unsafe fn into_extant_unchecked(self) -> Extant

Reinterprets this Value as Extant.

Safety

Does not verify that this Value is, in fact, Extant.

pub unsafe fn into_absent_unchecked(self) -> Absent

Reinterprets this Value as Absent.

Safety

Does not verify that this Value is, in fact, Absent.

pub fn cast_as_field(&self) -> Option<&Field<'a>>

Downcasts this Item reference to a typechecked Field reference.

pub fn cast_as_mut_field(&mut self) -> Option<&mut Field<'a>>

Downcasts this Item reference to a typechecked, mutable Field reference.

pub fn cast_as_attr(&self) -> Option<&Attr<'a>>

Downcasts this Item reference to a typechecked Attr reference.

pub fn cast_as_mut_attr(&mut self) -> Option<&mut Attr<'a>>

Downcasts this Item reference to a typechecked, mutable Attr reference.

pub fn cast_as_slot(&self) -> Option<&Slot<'a>>

Downcasts this Item reference to a typechecked Slot reference.

pub fn cast_as_mut_slot(&mut self) -> Option<&mut Slot<'a>>

Downcasts this Item reference to a typechecked, mutable Slot reference.

pub fn cast_as_value(&self) -> Option<&Value<'a>>

Downcasts this Item reference to a typechecked Value reference.

pub fn cast_as_mut_value(&mut self) -> Option<&mut Value<'a>>

Downcasts this Item reference to a typechecked, mutable Value reference.

pub fn cast_as_record(&self) -> Option<&Record<'a>>

Downcasts this Item reference to a typechecked Record reference.

pub fn cast_as_mut_record(&mut self) -> Option<&mut Record<'a>>

Downcasts this Item reference to a typechecked, mutable Record reference.

pub fn cast_as_data(&self) -> Option<&Data<'a>>

Downcasts this Item reference to a typechecked Data reference.

pub fn cast_as_mut_data(&mut self) -> Option<&mut Data<'a>>

Downcasts this Item reference to a typechecked, mutable Data reference.

pub fn cast_as_text(&self) -> Option<&Text<'a>>

Downcasts this Item reference to a typechecked Text reference.

pub fn cast_as_mut_text(&mut self) -> Option<&mut Text<'a>>

Downcasts this Item reference to a typechecked, mutable Text reference.

pub fn cast_as_num(&self) -> Option<&Num<'a>>

Downcasts this Item reference to a typechecked Num reference.

pub fn cast_as_mut_num(&mut self) -> Option<&mut Num<'a>>

Downcasts this Item reference to a typechecked, mutable Num reference.

pub fn cast_as_bool(&self) -> Option<&Bool>

Downcasts this Item reference to a typechecked Bool reference.

pub fn cast_as_mut_bool(&mut self) -> Option<&mut Bool>

Downcasts this Item reference to a typechecked, mutable Bool reference.

pub fn cast_as_extant(&self) -> Option<&Extant>

Downcasts this Item reference to a typechecked Extant reference.

pub fn cast_as_absent(&self) -> Option<&Absent>

Downcasts this Item reference to a typechecked Absent reference.

pub fn cast_into_field(self) -> Option<Field<'a>>

Downcasts this Item to a typechecked Field.

pub fn cast_into_attr(self) -> Option<Attr<'a>>

Downcasts this Item to a typechecked Attr.

pub fn cast_into_slot(self) -> Option<Slot<'a>>

Downcasts this Item to a typechecked Slot.

pub fn cast_into_value(self) -> Option<Value<'a>>

Downcasts this Item to a typechecked Value.

pub fn cast_into_record(self) -> Option<Record<'a>>

Downcasts this Item to a typechecked Record.

pub fn cast_into_data(self) -> Option<Data<'a>>

Downcasts this Item to typechecked Data.

pub fn cast_into_text(self) -> Option<Text<'a>>

Downcasts this Item to typechecked Text.

pub fn cast_into_num(self) -> Option<Num<'a>>

Downcasts this Item to a typechecked Num.

pub fn cast_into_bool(self) -> Option<Bool>

Downcasts this Item to a typechecked Bool.

pub fn cast_into_extant(self) -> Option<Extant>

Downcasts this Item to typechecked Extant.

pub fn cast_into_absent(self) -> Option<Absent>

Downcasts this Item to typechecked Absent.

Trait Implementations

impl<'a> PartialEq<Item<'a>> for Item<'a>

fn eq(&self, that: &Item<'a>) -> bool

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

fn ne(&self, that: &Item<'a>) -> bool

This method tests for !=.

impl<'a> Eq for Item<'a>

impl<'a> Ord for Item<'a>

fn cmp(&self, other: &Item<'a>) -> Ordering

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

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

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

Restrict a value to a certain interval.

impl<'a> PartialOrd<Item<'a>> for Item<'a>

fn partial_cmp(&self, _that: &Item<'a>) -> Option<Ordering>

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

fn lt(&self, _that: &Item<'a>) -> bool

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

fn le(&self, _that: &Item<'a>) -> bool

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

fn ge(&self, _that: &Item<'a>) -> bool

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

fn gt(&self, _that: &Item<'a>) -> bool

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

impl<'a> From<Field<'a>> for Item<'a>

fn from(field: Field<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Attr<'a>> for Item<'a>

fn from(attr: Attr<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Slot<'a>> for Item<'a>

fn from(slot: Slot<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Value<'a>> for Item<'a>

fn from(value: Value<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Record<'a>> for Item<'a>

fn from(record: Record<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Data<'a>> for Item<'a>

fn from(data: Data<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Text<'a>> for Item<'a>

fn from(text: Text<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Num<'a>> for Item<'a>

fn from(num: Num<'a>) -> Item<'a>

Performs the conversion.

impl<'a> From<Bool> for Item<'a>

fn from(bool: Bool) -> Item<'a>

Performs the conversion.

impl<'a> From<Extant> for Item<'a>

fn from(extant: Extant) -> Item<'a>

Performs the conversion.

impl<'a> From<Absent> for Item<'a>

fn from(absent: Absent) -> Item<'a>

Performs the conversion.

impl<'a> From<u8> for Item<'a>

fn from(value: u8) -> Item<'a>

Performs the conversion.

impl<'a> From<i8> for Item<'a>

fn from(value: i8) -> Item<'a>

Performs the conversion.

impl<'a> From<u16> for Item<'a>

fn from(value: u16) -> Item<'a>

Performs the conversion.

impl<'a> From<i16> for Item<'a>

fn from(value: i16) -> Item<'a>

Performs the conversion.

impl<'a> From<u32> for Item<'a>

fn from(value: u32) -> Item<'a>

Performs the conversion.

impl<'a> From<i32> for Item<'a>

fn from(value: i32) -> Item<'a>

Performs the conversion.

impl<'a> From<u64> for Item<'a>

fn from(value: u64) -> Item<'a>

Performs the conversion.

impl<'a> From<i64> for Item<'a>

fn from(value: i64) -> Item<'a>

Performs the conversion.

impl<'a> From<f16> for Item<'a>

fn from(value: f16) -> Item<'a>

Performs the conversion.

impl<'a> From<f32> for Item<'a>

fn from(value: f32) -> Item<'a>

Performs the conversion.

impl<'a> From<f64> for Item<'a>

fn from(value: f64) -> Item<'a>

Performs the conversion.

impl<'a> From<usize> for Item<'a>

fn from(value: usize) -> Item<'a>

Performs the conversion.

impl<'a> From<isize> for Item<'a>

fn from(value: isize) -> Item<'a>

Performs the conversion.

impl<'a> From<bool> for Item<'a>

fn from(value: bool) -> Item<'a>

Performs the conversion.

impl<'a> Debug for Item<'a>

fn fmt(&self, _f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<'a> Hash for Item<'a>

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

Feeds this value into the given [Hasher].

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

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

impl<'a> Clone for Item<'a>

fn clone(&self) -> Item<'a>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'a> AsMut<Item<'a>> for Field<'a>

fn as_mut(&mut self) -> &mut Item<'a>

Performs the conversion.

impl<'a> AsMut<Item<'a>> for Attr<'a>

fn as_mut(&mut self) -> &mut Item<'a>

Performs the conversion.

impl<'a> AsMut<Item<'a>> for Slot<'a>

fn as_mut(&mut self) -> &mut Item<'a>

Performs the conversion.

impl<'a> AsRef<Item<'a>> for Field<'a>

fn as_ref(&self) -> &Item<'a>

Performs the conversion.

impl<'a> AsRef<Item<'a>> for Attr<'a>

fn as_ref(&self) -> &Item<'a>

Performs the conversion.

impl<'a> AsRef<Item<'a>> for Slot<'a>

fn as_ref(&self) -> &Item<'a>

Performs the conversion.

impl<'a> Default for Item<'a>

fn default() -> Item<'a>

Returns the "default value" for a type.

impl<'a, 'b> Stow<'b, Item<'b>> for Item<'a>

unsafe fn stow(
    src: *mut Item<'a>,
    dst: *mut Item<'b>,
    hold: &dyn Hold<'b>
) -> Result<(), HoldError>

Moves the value at the src pointer to the dst pointer, recursively moving all child values into the hold. If a child stow operation fails, then any already completed child stow operations get reverted by calling unstow on the child.

unsafe fn unstow(src: *mut Item<'a>, dst: *mut Item<'b>)

Reverts the most recent stow operation by moving the value at the dst pointer back to the src pointer from whence it came. The memory at the src address will be in the same state the stow operation left it in.

impl<'a> TryClone for Item<'a>

fn try_clone(&self) -> Result<Item<'a>, HoldError>

Returns a clone of self; returns an error if the clone fails.

impl<'a, 'b> CloneIntoHold<'a, Item<'a>> for Item<'b>

fn try_clone_into_hold(
    &self,
    hold: &dyn Hold<'a>
) -> Result<Item<'a>, HoldError>

Returns a clone of self allocated in hold; returns an error if the clone fails.

default fn clone_into_hold(&self, hold: &dyn Hold<'a>) -> T

Returns a clone of self allocated in hold.