Enum TypeKind 

pub enum TypeKind {
    Scalar(ScalarKind),
    Str,
    String,
    Optional(Box<TypeRef>),
    Vec(Box<TypeRef>),
    Slice(Box<TypeRef>),
    Fallible {
        ok: Box<TypeRef>,
        err: Box<TypeRef>,
    },
    Named {
        id: TypeId,
        args: Vec<GenericArg>,
    },
    Array {
        elem: Box<TypeRef>,
        extent: Box<ArrayExtent>,
    },
    Ref {
        lifetime: Option<Lifetime>,
        mutable: bool,
        inner: Box<TypeRef>,
    },
    Boxed(Box<TypeRef>),
    Cow {
        lifetime: Lifetime,
        inner: Box<TypeRef>,
    },
    Uninit(Box<TypeRef>),
    Callback {
        args: Vec<TypeRef>,
    },
    Unit,
}

The accepted syntax of a TypeRef: the subset of syn::Type a #[prebindgen] crate may write, and nothing more.

One variant per accepted Rust form, not per destination concept. str and String are two forms and get two variants; Box<T> is a form of its own and does not disappear into T. Nothing here folds two spellings together, which is what makes TypeRef::spell recoverable from this — rebuilding the syntax from a kind is the round-trip that checks it.

Why it is only syntax

It was a destination-neutral classification once, and that leaked: &T earned a layer while Box<T> was declared transparent, on no principle either adapter shared, and Cbindgen went on picking its C type from the Rust spelling anyway. Deciding that &str and String are both “a string” is a destination decision, so it belongs to the destination — the model hands over what the source wrote and stays out of it.

Where two adapters want the same fold, it is a reading, not a variant: TypeRef::unwrapped peels Box/Cow for the consumers that want them gone, and the ones that must rebuild the Rust value ask TypeRef::erased_wrappers instead. One helper, visible at the call site, rather than a fold baked into every classification.

Variants

Scalar(ScalarKind)

A primitive with a fixed C/JVM counterpart — u8, bool, f64.

A closed set of bare idents, so recognising one is reading the syntax rather than interpreting it — and it keeps every adapter off a name table of its own.

Str

str — unsized, so it is only ever reached through a Ref or a wrapper.

String

String.

Optional(Box<TypeRef>)

Option<T>.

Vec(Box<TypeRef>)

Vec<T>.

Slice(Box<TypeRef>)

[T] — the unsized run, reached through a Ref or a wrapper. Not the same form as Vec, so not the same variant.

Fallible

Result<T, E>.

Fields

ok: Box<TypeRef>

err: Box<TypeRef>

Named

Any other named type: a #[prebindgen] struct or enum, or a foreign path.

id is the type’s identity — a name, not a syn::Path, so nothing downstream has to take a path apart to learn what a type is. args is the last segment’s generic arguments, in the order they were written and including lifetimes, because dropping either would make the spelling unrecoverable.

Fields

id: TypeId

args: Vec<GenericArg>

Array

[T; N] — a run of T whose length is known at compile time.

Fields

elem: Box<TypeRef>

extent: Box<ArrayExtent>

Boxed: an extent carries an Origin over the length expression, which makes it the size outlier among the kinds, and an array is the rare one. The same trade-off Unsupported::error makes.

Ref

A borrow — &T or &mut T, with the lifetime the source wrote.

An out-parameter is &mut over Uninit, which is what the source spells. What that means at a boundary — the caller supplies the slot, the callee fills it — is the adapter’s reading of the form, not a third value of a mode enum.

Fields

lifetime: Option<Lifetime>

mutable: bool

inner: Box<TypeRef>

Boxed(Box<TypeRef>)

Box<T>.

A form of its own. It was erased once, on the grounds that no destination language can tell Box<T> from T — true, and still the adapter’s call to make: TypeRef::unwrapped makes it, on demand.

Cow

Cow<'a, T>.

The lifetime is not optional: Cow has one in its own signature, so a Cow<T> is not Rust and no source crate can compile it. Lowering refuses the shape (WrongGenericArguments) rather than modelling an absence that would then have to be spelled back as something the source did not write.

Fields

lifetime: Lifetime

inner: Box<TypeRef>

Uninit(Box<TypeRef>)

MaybeUninit<T>.

Accepted only directly under a &mut — see UnsupportedTypeReason::OwnedUninit. It has a variant because the source writes it; that it is refused elsewhere is an acceptance rule, which is a separate question from how the form is represented.

Callback

impl Fn(A, B, …) + Send + Sync + 'static — the callback form.

Fields

args: Vec<TypeRef>

Unit

().

Trait Implementations

impl Clone for TypeKind

fn clone(&self) -> TypeKind

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TypeKind

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

Formats the value using the given formatter.