Struct ArrayExtent 

pub struct ArrayExtent {
    pub value: usize,
    pub source: ExtentSource,
    pub origin: Origin<Expr>,
}

A fixed-size array’s extent: the number, the const identity when the source named one, and the spelling it was written with.

Three facts, three consumers — and no ==

The three answer different questions, and deliberately no equality is provided, because there is no single one that could be right. A consumer projects the fact it actually needs:

Question	Projection
is this the same type / the same converter?	Self::value
how does a C declaration spell it?	Self::origin.syntax, per occurrence
which consts must reach the header as a #define?	Self::const_id

A blanket == mixes them and is wrong under either reading: comparing source makes [u8; A] differ from [u8; 4] when A == 4 — one Rust type reported as two — while ignoring the spelling makes [u8; 4] equal [u8; 0x04], whose retained syntax differs. Neither is type identity and neither is spelling identity, so the choice belongs to whoever is asking.

Note for a converter table

value being the type identity means several occurrences share one converter, and their spellings differ. A shared converter therefore needs a canonical Rust spelling chosen on purpose — the evaluated literal is the obvious one — rather than whichever occurrence happened to populate a deduplicated entry.

This lives on the use site — a field’s or parameter’s type — and never on anything keyed by type, for the same reason: two occurrences of one type may name the length differently, so a type-keyed table could only report whichever was stored last.

Fields

value: usize

The evaluated length. The type identity: [u8; A] and [u8; 4] are one Rust type when A == 4, and a destination language with no way to name a Rust const needs the number.

source: ExtentSource

How the length was addressed, so a C header can re-state uint8_t tag[TAG_LEN] and know TAG_LEN must reach it.

origin: Origin<Expr>

The length expression as written — 4, 0x04, TAG_LEN — and where it came from. The spelling of this occurrence, which is what a declaration re-emits; two occurrences of one type may differ here.

Implementations

impl ArrayExtent

pub fn const_id(&self) -> Option<&ConstId>

The const this extent named, if it named one.

Trait Implementations

impl Clone for ArrayExtent

fn clone(&self) -> ArrayExtent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ArrayExtent

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

Formats the value using the given formatter.