Struct Origin 

pub struct Origin<S> {
    pub location: Rc<SourceLocation>,
    /* private fields */
}

The syntax a node was built from, plus where that syntax came from.

Why the two travel together

syn tokens normally carry spans, so in principle the syntax alone could answer “where was this written”. Not here: the proc-macro serializes each marked item as a string into JSONL, and build.rs re-parses it, so every span in spell() points into an anonymous buffer. [SourceLocation::from_span] captures file, line and column at macro-expansion time — while real rustc spans still exist — precisely because they cannot survive that trip.

Why the location is shared

One captured record is one item, so there is exactly one location per item and none of its own for any component. An item and everything inside it — parameters, fields, variants, types, extents — therefore point at the same [SourceLocation], which is both the honest answer and the cheap one: a struct with twenty fields keeps one location, not twenty copies of a path.

Rc rather than Arc: this holds syn values, which are !Send, so the model can never cross a thread boundary and an atomic refcount would only cost. TypeKey made the same call for the same reason.

The rule about origins

A reference carries a name; the declaration carries the origin.

location.crate_name here is the crate whose source this node was written in — the use site. It is never part of a referenced item’s identity: TypeId is a name alone, because #[prebindgen] names live in one flat namespace. ConstId is not an exception — the crate it records is the const’s declaring crate, obtained by lookup, and that is exactly what lets an array extent refuse a const from another source.

The syntax is sealed

You may output the source. You may not read it.

spell hands out tokens and nothing else, which is all generated Rust ever needed. The node is reachable only through one crate-internal accessor, and the field itself is pub(super) — so the model still reads it freely, while everything outside is limited to the spelling.

It was a public field returning a syn node to anyone who asked. Outside this crate, captured syntax is reachable only through Emit, and the compiler enforces it.

Fields

location: Rc<SourceLocation>

The captured item this node belongs to, shared with every sibling.

Implementations

impl<S> Origin<S>

pub fn new(syntax: S, location: Rc<SourceLocation>) -> Self

pub fn crate_name(&self) -> Option<&str>

The crate this node’s source was written in.

The use site, not the declaring crate of anything it names.

pub fn with<T>(&self, syntax: T) -> Origin<T>

The same location over different syntax — for building a component’s origin from the item’s.

impl Origin<Type>

pub fn key(&self) -> TypeKey

This type’s identity as a table key — the same answer TypeRef::key gives for a reading.

Here because a declaration is an Origin<syn::Type>: the type a build script wrote, carried with a placeless location. Asking it for its identity is not reaching for the node, and it should not have to be spelled as one — every TypeKey::from_type(decl.as_syn()) was a keying operation wearing an escape’s clothes.

impl<S: ToTokens> Origin<S>

pub fn spell(&self) -> TokenStream

The node’s tokens, for generated Rust to spell.

The only output route, and deliberately not ToTokens. Implementing that trait would make quote!(#node) work — and hand every consumer to_token_stream().to_string() with it, which is a classifier’s input in a spelling’s clothing. A TokenStream interpolates just as well one let earlier, and the string, if a site really wants one, is now a two-call pattern that says so.

It does not make a token string impossible — spell().to_string() reaches one, and the ledger still lists that as open. What it makes is visible: .to_token_stream().to_string() was indistinguishable from the same call on a type an adapter built itself.

pub, not pub(crate): the registry pipeline’s own tests (now in the separate prebindgen-registry crate) call this on a captured element’s origin — see TypeRef’s doc for why this seal is now a convention rather than a compiler check.

impl Origin<Type>

pub fn declared_spelling(&self) -> TokenStream

A declared type’s tokens.

Public where Origin::spell is sealed, and the difference is what S is. An Origin<syn::ItemFn>’s tokens re-parse to the captured item, so handing them out is the item door under another name — that one is Emit’s to open. An Origin<syn::Type> in an adapter’s declaration holds a type the build script wrote, which was never captured syntax and which #280 leaves the model no way to have a reading for.

Still a token route, and still one C3 has to account for when TypeRef::spell moves onto Emit: a declaration is an identity (key()), and the two sites that spell one do it to splice #target into generated Rust.

Trait Implementations

impl<S: Clone> Clone for Origin<S>

fn clone(&self) -> Origin<S>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<S: Debug> Debug for Origin<S>

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

Formats the value using the given formatter.