Struct RegionTree 

pub struct RegionTree { /* private fields */ }

Tree of regions enforcing structured concurrency (§4.11).

Every task/actor must be region-owned. The tree enforces INV-REGION-QUIESCENCE: no region closes until all children complete, all finalizers run, and all obligations resolve.

Implementations

impl RegionTree

pub fn new() -> Self

Create an empty region tree.

pub fn create_root( &mut self, kind: RegionKind, cx: Cx<FullCaps>, ) -> Result<Region>

Create the root region.

Only one root region may exist. Returns an error if a root already exists.

pub fn create_child( &mut self, parent: Region, kind: RegionKind, cx: Cx<FullCaps>, ) -> Result<Region>

Create a child region under the given parent.

pub fn root(&self) -> Option<Region>

Root region, if created.

pub fn kind(&self, id: Region) -> Option<RegionKind>

Query the kind of a region.

pub fn state(&self, id: Region) -> Option<RegionState>

Query the state of a region.

pub fn parent(&self, id: Region) -> Option<Option<Region>>

Query the parent of a region.

pub fn children(&self, id: Region) -> Option<&[Region]>

List children of a region.

pub fn cx(&self, id: Region) -> Option<Cx<FullCaps>>

Get a clone of the region’s Cx for cancellation inspection.

pub fn active_tasks(&self, id: Region) -> usize

Active task count for a region.

pub fn active_obligations(&self, id: Region) -> usize

Active obligation count for a region.

pub fn register_task(&self, id: Region) -> Result<TaskHandle>

Register a task in a region, returning an RAII handle.

The task count is incremented; when the handle is dropped, it decrements. Returns Err(Busy) if the region is not RegionState::Open.

pub fn register_obligation(&self, id: Region) -> Result<ObligationHandle>

Register an obligation in a region, returning an RAII handle.

Obligations can be registered while the region is Open or Closing (to allow in-flight work to create follow-up obligations during drain). Returns Err(Busy) if the region is RegionState::Closed.

pub fn register_finalizer( &mut self, id: Region, finalizer: impl FnOnce() + Send + 'static, ) -> Result<()>

Register a finalizer callback to run during region close.

pub fn begin_close(&mut self, id: Region) -> Result<()>

Begin closing a region: cancel its Cx and set state to Closing.

Recursively begins close on all descendant regions (parent-first cancellation propagation per INV-CANCEL-PROPAGATES).

Does NOT wait for quiescence. Use is_quiescent to poll, then complete_close to finalize.

pub fn is_quiescent(&self, id: Region) -> bool

Check whether a region has reached quiescence.

A region is quiescent when:

• all child regions are RegionState::Closed,
• active task count is zero,
• active obligation count is zero.

pub fn complete_close(&mut self, id: Region) -> Result<()>

Complete region close: run finalizers and mark as RegionState::Closed.

Returns an error if the region is not quiescent.

pub fn close_and_drain(&mut self, id: Region) -> Result<()>

Close a region and spin-wait until quiescent, then finalize.

This is the full close protocol: cancel → drain → finalize. Blocks the caller until INV-REGION-QUIESCENCE is satisfied. Children are drained bottom-up before the parent.

Trait Implementations

impl Default for RegionTree

fn default() -> Self

Returns the “default value” for a type.