refactor(effect): name the lift's rejection channel; fold boundary settlements without an unknown failure - #517
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… settlements without an unknown failure lift.ts: `LiftedRejection` names the identity lift's fail channel (the raw thrown/rejected value, narrowed by callers), and `liftPromise` hands the helper Effect's interruption AbortSignal per rc.112's tryPromise contract. reconciler.ts: `waitSettledBoundary` folds a boundary's settlement inside the promise instead of catching an `unknown` off the Effect channel; the rejection reason stays data for `renderErrorFrom` (React's digest-bearing objects), so it is deliberately not normalized through `toRuntimeError`.
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Summary
The two "small ones" from the Effect-conformance audit: the reconciler's momentary
unknownon the fail channel, and the dev seam's identity lift inferring bareunknownat every call site. Behavior-preserving: no runtime path changes; everyliftPromise/liftTrycall site (82) type-checks unchanged.What changed
packages/rsc-runtime/src/reconciler.ts:288–300(audit row:293–295,Effect.tryPromise({ catch: (error) => error })→unknownInEffectCatch). The audit suggestedcatch: toRuntimeError; that would be a behavior change: a boundary's rejection reason is data thatrenderErrorFrom(:130) reads — React rejects a boundary thenable with a{ message, digest }object, andtoRuntimeErrorwould turn a non-Errorobject intonew Error('[object Object]')and lose the digest-derivedcode. InsteadwaitSettledBoundaryfolds both settlements inside the promise (Effect.promise(() => thenable.then(ok, (error) => ({ boundary, error, ok: false })))), so the Effect can never fail and nothingunknownever sits on the error channel — the reason travels as a field ofSettledBoundary, as before. Return type narrows fromEffect<SettledBoundary, Error>toEffect<SettledBoundary>.packages/agent-bundle/src/effect/lift.ts(audit row:11–15). The audit proposed typingEasCodedError | DiagnosticError | unknown; that union collapses tounknownand any narrower union would be unsound — the lift is an identity by contract (typed dev errors and rawAbortSignal.reasonvalues must cross the boundary untouched). So:export type LiftedRejection = unknownnames the channel: hovers and signatures now readEffect<A, LiftedRejection>with the doc explaining it is the raw thrown/rejected value that callers narrow (instanceof,isErrno,Effect.mapErrorinto a typed dev error) rather than a shape to assume, and how the boundary maps whatever reaches it.liftPromise'sevaluateis now(signal: AbortSignal) => PromiseLike<A>— rc.112's ownEffect.tryPromisecontract (Effect.ts:969–973): the signal aborts when the fiber is interrupted, so a cancellable Promise API can take it directly. Zero-arg thunks are unchanged.Effect.tryPromise(fn)is not used (it wraps rejections inCause.UnknownError).Idioms and citations
repos/effect/LLMS.md/ repo sectionunknown/ globalErroron the fail channel; a value that is data stays in the success channelagent-patterns/effect-errors.md"What to avoid:unknownor globalErrorin the fail channel (unknownInEffectCatch)"Effect.promisefor a promise that cannot reject;tryPromise'stry(signal)for interruption-aware liftsEffect.promiserelease), rc.112Effect.promise/tryPromisesignaturesdocs/effect-conventions.mdStage 3 "Hurt": "BareEffect.tryPromise(fn)wraps rejections inCause.UnknownError; always route throughsrc/effect/lift.ts"Tests
packages/agent-bundle/tests/effect-boundary.test.ts(effect lifts): rejected typed errors and raw non-Errorreasons are identity-preserved on the fail channel (Exit+Cause.squash), thrown values likewise vialiftTry; the Promise edge rethrows typed errors as-is and wraps a non-Errorper the mapping table; the lifted helper receives anAbortSignalthat is not aborted while running and aborts when the host signal interrupts the fiber (AbortErrorat the edge).emits a represented boundary error and still completes siblings,emits a replace or error for every boundary that settled before resnapshot) cover the fold; all 55 dispatcher/boundary tests green.pnpm typecheck,pnpm lintgreen;pnpm test:unitgreen (3186 passed).Changeset
skip-changeset: type-level and internal-structure only; no Promise-side value, message, or export changes.Review status
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