Struct OptionalLayout 

pub struct OptionalLayout {
    pub size: u32,
    pub align: u32,
    pub tag_offset: u32,
    pub payload_offset: u32,
    pub payload_size: u32,
    pub payload_align: u32,
}

Layout decisions for an Optional<T> value.

Optional is laid out as a uniform { tag: i32, payload: T } pair in linear memory. Tag values are OPTIONAL_TAG_NIL (no payload) and OPTIONAL_TAG_SOME (payload present); the same byte range is reserved either way so callers don’t need to know the discriminant to compute the allocation size. Optional<Never> is the type of nil itself — it has no payload, so payload_size == 0 and the total value is just the 4-byte tag.

Fields

size: u32

Total bytes one optional value occupies, including tag, post-tag alignment padding, payload, and trailing alignment padding.

align: u32

Optional alignment — the maximum of OPTIONAL_TAG_ALIGN and the payload’s alignment (or just the tag alignment for Optional<Never>).

tag_offset: u32

Offset of the discriminant tag (always 0).

payload_offset: u32

Offset where the payload starts. tag_offset + OPTIONAL_TAG_SIZE rounded up to the payload’s alignment.

payload_size: u32

Payload size in bytes. Aggregate inner types collapse to a 4-byte pointer; Optional<Never> has size 0.

payload_align: u32

Payload alignment in bytes. 1 when there is no payload (Optional<Never>).

Trait Implementations

impl Clone for OptionalLayout

fn clone(&self) -> OptionalLayout

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for OptionalLayout

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

Formats the value using the given formatter.

impl PartialEq for OptionalLayout

fn eq(&self, other: &OptionalLayout) -> 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 Copy for OptionalLayout

impl Eq for OptionalLayout

impl StructuralPartialEq for OptionalLayout