Struct Partial

pub struct Partial<'s> { /* private fields */ }

A partially-initialized shape.

This type keeps track of the initialized state of every field and only allows getting out the concrete type or the boxed concrete type or moving out of this partial into a pointer if all the fields have been initialized.

Implementations

impl Partial<'_>

pub fn alloc(shape: ShapeDesc) -> Self

Allocates a partial on the heap for the given shape descriptor.

pub fn borrow<T: Shapely>(uninit: &mut MaybeUninit<T>) -> Self

Borrows a MaybeUninit<Self> and returns a Partial.

Before calling assume_init, make sure to call Partial.build_in_place().

pub fn array_slot(&mut self, size_hint: Option<usize>) -> Option<ArraySlot>

Returns a slot for treating this partial as an array (onto which you can push new items)

pub fn hashmap_slot(&mut self, size_hint: Option<usize>) -> Option<HashMapSlot>

Returns a slot for a HashMap field in the shape.

pub fn hashmap_iter(&self) -> Option<HashMapIter>

Returns an iterator over the key-value pairs in a HashMap

pub fn scalar_slot(&mut self) -> Option<Slot<'_>>

Returns a slot for assigning this whole shape as a scalar

pub fn slot_by_name<'s>( &'s mut self, name: &str, ) -> Result<Slot<'s>, FieldError>

Returns a slot for initializing a field in the shape.

pub fn slot_by_index(&mut self, index: usize) -> Result<Slot<'_>, FieldError>

Returns a slot for initializing a field in the shape by index.

pub fn build_in_place(self)

Asserts that every field has been initialized and forgets the Partial.

This method is only used when the origin is borrowed. If this method is not called, all fields will be freed when the Partial is dropped.

Panics

This function will panic if:

• The origin is not borrowed (i.e., it’s heap allocated).
• Any field is not initialized.

pub fn build<T: Shapely>(self) -> T

Builds a value of type T from the partial representation.

Panics

This function will panic if:

• Not all the fields have been initialized.
• The generic type parameter T does not match the shape that this partial is building.

pub fn build_boxed<T: Shapely>(self) -> Box<T>

Build that partial into a boxed completed shape.

Panics

This function will panic if:

• Not all the fields have been initialized.
• The generic type parameter T does not match the shape that this partial is building.

Safety

This function uses unsafe code to create a Box from a raw pointer. It’s safe because we’ve verified the initialization and shape matching, and we forget self to prevent double-freeing.

pub unsafe fn move_into(self, target: NonNull<u8>)

Moves the contents of this Partial into a target memory location.

This function is useful when you need to place the fully initialized value into a specific memory address, such as when working with FFI or custom allocators.

Safety

The target pointer must be valid and properly aligned, and must be large enough to hold the value. The caller is responsible for ensuring that the target memory is properly deallocated when it’s no longer needed.

pub fn shape(&self) -> ShapeDesc

Returns the shape we’re currently building.

pub fn addr(&self) -> NonNull<u8>

Returns the address of the value we’re building in memory.

pub fn set_variant_by_name( &mut self, variant_name: &str, ) -> Result<(), FieldError>

Sets the variant of an enum by name.

Errors

Returns an error if:

• The shape doesn’t represent an enum.
• No variant with the given name exists.

pub fn set_variant_by_index( &mut self, variant_index: usize, ) -> Result<(), FieldError>

Sets the variant of an enum by index.

Errors

Returns an error if:

• The shape doesn’t represent an enum.
• The index is out of bounds.

pub fn selected_variant_index(&self) -> Option<usize>

Returns the currently selected variant index, if any.

pub fn variant_field_by_name<'s>( &'s mut self, name: &str, ) -> Result<Slot<'s>, FieldError>

Get a slot for a field in the currently selected variant.

Errors

Returns an error if:

• The shape doesn’t represent an enum.
• No variant has been selected yet.
• The field name doesn’t exist in the selected variant.
• The selected variant is a unit variant (which has no fields).

Trait Implementations

impl Drop for Partial<'_>

fn drop(&mut self)

Executes the destructor for this type.