Struct Stop 

pub struct Stop(/* private fields */);

Whether the caller still wants the reply.

docs/80 §80.12 named the gap this closes: cancellation rides the evaluator’s step counter, so a parallel: child blocked inside an outbound call was stopped only when the call came back — a scope whose first child failed still waited out a sibling’s ten-second timeout. §80.12 also says where the fix belongs: “a deadline on the net seam rather than a change to the scope”, because the scope is already right about when to stop a child and the thing it cannot reach is a socket.

A predicate rather than a token or a channel, for the reason the rest of this seam is what it is: the caller already knows the answer — beck-eval has the chain of enclosing scopes and their first-failed indices — and anything richer would be a second copy of that state, kept in step by hand.

Implementations

impl Stop

pub fn never() -> Stop

Nobody is going to stop this call, so an implementation need not watch for it.

Stop::watched is false for this one, which is what lets a client take the path with no timer in it — the ordinary case, since only a child of a parallel: can be cancelled.

pub fn when(f: impl Fn() -> bool + Send + Sync + 'static) -> Stop

pub fn asked(&self) -> bool

Whether the caller has stopped wanting the reply. Called repeatedly, so it is cheap.

pub fn watched(&self) -> bool

Whether anybody could ever ask.

Trait Implementations

impl Clone for Stop

fn clone(&self) -> Stop

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Stop

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

Formats the value using the given formatter.

impl Default for Stop

fn default() -> Stop

Returns the “default value” for a type.