Enum RegisterError 

pub enum RegisterError {
    UnknownDep(NodeId),
    OperatorWithoutDeps,
    InitialOnlyForStateNodes,
    TerminalDep(NodeId),
    OperatorSeedSentinel,
}

Errors returnable by Core::register and its sugar wrappers (Core::register_state, Core::register_producer, Core::register_derived, Core::register_dynamic, Core::register_operator).

Slice H (2026-05-07) promoted these from assert!/panic! to typed errors so that callers can recover from contract violations without process abort. Every variant corresponds to a construction-time invariant that the caller is responsible for upholding; the dispatcher rejects the registration before any reactive state is created (so there is no Message::Error channel through which to surface the failure — these are imperative-layer errors, not reactive ones).

All variants are zero-side-effect: when Core::register returns Err, no node has been added to the graph and any handle retains taken on the way in (e.g. operator scratch seed retains via BindingBoundary::retain_handle) have been released.

Variants

UnknownDep(NodeId)

One of the supplied dep ids is not a registered node.

OperatorWithoutDeps

op was supplied (operator node) but deps was empty. Operator nodes need at least one dep — for subscription-managed combinators with no declared deps, use Core::register_producer instead.

InitialOnlyForStateNodes

NodeOpts::initial was set to a real handle but the registration shape is not a state node (state nodes are deps.is_empty() && fn_id.is_none() && op.is_none()). Initial cache only makes sense for state nodes.

TerminalDep(NodeId)

A supplied dep is terminal (COMPLETE / ERROR) AND not resubscribable. Adding it would create a permanent wedge — the dep will never re-emit, so the registered node would be stuck. Mirrors SetDepsError::TerminalDep at registration time.

OperatorSeedSentinel

A stateful operator (OperatorOp::Scan / OperatorOp::Reduce) was registered with seed = NO_HANDLE. R2.5.3 first-run gate requires the seed to be a real handle so that the operator can emit on its first fire.

Trait Implementations

impl Clone for RegisterError

fn clone(&self) -> RegisterError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RegisterError

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

Formats the value using the given formatter.

impl Display for RegisterError

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

Formats the value using the given formatter.

impl Error for RegisterError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for RegisterError

fn eq(&self, other: &RegisterError) -> 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 Eq for RegisterError

impl StructuralPartialEq for RegisterError