Enum GcNode 

pub enum GcNode {
    ClosureFn(Weak<NativeFn>),
    EnvWrapper(Weak<Env>),
    EnvBindings(Weak<EnvBindings>),
    Thunk(Weak<Thunk>),
    Channel {
        weak: Weak<Channel>,
        id: ChannelId,
    },
    Promise {
        weak: Weak<AsyncPromise>,
        id: PromiseId,
    },
    MultiMethod(Weak<MultiMethod>),
    MutableArray(Weak<MutableArray>),
    MutableCell(Weak<MutableCell>),
}

A registered cycle-birth candidate. Registered once at creation by the (cold) constructors of the only objects that can be born into cycles; upvalue cells and interior Value nodes are discovered during trace (via GcEdge), never registered.

Variants

ClosureFn(Weak<NativeFn>)

A VM closure’s NativeFn wrapper (registered by make_closure).

EnvWrapper(Weak<Env>)

An env wrapper allocation, registered on first home-adoption. The wrapper (not just its bindings) is the candidate so a pass can reach the whole parent chain: a cycle that closes through an ANCESTOR env’s bindings (e.g. module code set!-ing a root binding to a closure homed in the module) is reachable from the home wrapper via parent edges even when no registered bindings map holds the closure.

EnvBindings(Weak<EnvBindings>)

An env’s bindings allocation (data-path registration; home adoption registers the wrapper above, which reaches the bindings anyway).

Thunk(Weak<Thunk>)

delay thunk (data-only cycles via forced).

Channel

Channel handle (data-only cycles via the runtime’s channel BUFFER, which lives in the ChannelRegistry, reached via the runtime interior hooks). The id is retained so a prune of a dead handle can also evict the registry record — the handle Weak alone cannot recover it once dead.

Fields

weak: Weak<Channel>

id: ChannelId

Promise

Promise handle (data-only cycles via the runtime’s SETTLED value, which lives in the PromiseRegistry, reached via the runtime interior hooks). The id is retained for the same dead-handle eviction reason.

Fields

weak: Weak<AsyncPromise>

id: PromiseId

MultiMethod(Weak<MultiMethod>)

Multimethod (data-only cycles via the method table).

MutableArray(Weak<MutableArray>)

Mutable array (data-only cycles via the element vector).

MutableCell(Weak<MutableCell>)

Mutable cell (data-only cycles via the value slot).