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Delete the evaluation context's dead completion channel - #2895

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drop-dead-completion-channel
Aug 2, 2026
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Delete the evaluation context's dead completion channel#2895
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drop-dead-completion-channel

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@lahma lahma commented Aug 2, 2026

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Summary

Removes EvaluationContext.Completion, which could only ever hold Normal, and its dead consumers.

Details

The single assignment to EvaluationContext.Completion anywhere in the repository is Completion = CompletionType.Normal inside PrepareFor. So IsAbrupt() always returned false and its consumers were unreachable, not merely untaken.

It has been dead since the day it was written

Abrupt expression completions have travelled by JavaScriptException or through the deferred Engine._error slot ever since. No behaviour was lost then and none is restored here.

What goes

The field, IsAbrupt(), and fourteen consumers across class declarations, destructuring, assignment and object expressions.

In JintForInForOfStatement the reach is larger than the call sites suggest: the status local was fed only from this channel, so its guard block — three new Completion(status, …) returns and two iteratorRecord.Close(status) calls — went with it.

Why bother

Two reasons beyond tidiness.

JintVariableDeclaration's tight-loop ExecuteDiscarded documents its own correctness as resting on this field never being abrupt. A dead field whose deadness is load-bearing for a fast path is a trap for whoever next decides to "fix" it by writing to it.

And PrepareFor now collapses to a single store. It runs on every non-block statement and, via JintExpression.Evaluate, on every expression node in the program. context.IsAbrupt() was also a field load and compare on the simple-assignment path, which every x = y travels.

Linked issue

None on file — found while auditing EvaluationContext.

Test plan

  • Ran dotnet test --configuration Release locally (all projects, net10.0 + net472)
  • Ran Jint.Tests.Test262 — 99,738 passed, 0 failed, identical to the parent commit
  • Perf numbers pending — this touches PrepareFor and the assignment path, so a SunSpider + Dromaeo table is owed before merge

No new tests: this is dead-code removal, and the existing suite is what proves the branches were unreachable.

Breaking change?

No. EvaluationContext is internal.

Base automatically changed from jump-label-on-completion to main August 2, 2026 14:25
@lahma @claude
Delete the evaluation context's dead completion channel
03cabf4 
`EvaluationContext.Completion` could only ever hold `Normal`. The single
assignment to it anywhere in the repository is `Completion = CompletionType.Normal`
inside `PrepareFor`, so `IsAbrupt()` always returned false and its consumers were
unreachable rather than merely untaken.

It has been dead since the day it was written. #1291 (2022-09-10) moved the
abrupt-completion check off `ExpressionResult` onto the context; #1292, the next
day, deleted `ExpressionResult` and with it the only code that ever wrote a
non-Normal value. Abrupt expression completions have travelled by
`JavaScriptException` or through the deferred `Engine._error` slot ever since, so
no behaviour was lost and none is restored here.

Removed: the field, `IsAbrupt()`, and fourteen consumers across class
declarations, destructuring, assignment and object expressions. In
`JintForInForOfStatement` the reach is larger than the call sites suggest: the
`status` local was fed only from this channel, so its guard block — three
`new Completion(status, …)` returns and two `iteratorRecord.Close(status)` calls —
went too.

Two reasons to do this rather than leave it:

`JintVariableDeclaration`'s tight-loop `ExecuteDiscarded` documents its own
correctness as resting on the field never being abrupt. A dead field whose
deadness is load-bearing for a fast path is a trap for whoever next decides to
"fix" it by writing to it.

And `PrepareFor` now collapses to a single store. It runs on every non-block
statement and, via `JintExpression.Evaluate`, on every expression node in the
program; `context.IsAbrupt()` was also a field load and compare on the
simple-assignment path, which `x = y` travels.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
@lahma
lahma force-pushed the drop-dead-completion-channel branch from cecd422 to 03cabf4 Compare August 2, 2026 14:25
@lahma
lahma merged commit 4952e9c into main Aug 2, 2026
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@lahma
lahma deleted the drop-dead-completion-channel branch August 2, 2026 15:15
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legrab added a commit to legrab/pocok that referenced this pull request Aug 18, 2026
@legrab
Bump Jint from 4.15.3 to 4.16.0 (#56)
ef20afa 
Updated [Jint](https://github.com/sebastienros/jint) from 4.15.3 to
4.16.0.

<details>
<summary>Release notes</summary>

_Sourced from [Jint's
releases](https://github.com/sebastienros/jint/releases)._

## 4.16.0

Jint 4.16.0 is a **correctness- and reliability-focused release**:
alongside asynchronous module loading, proper tail calls and four new
iterator built-ins, a pre-tag review swept the whole engine and fixed
what it found — including long-standing defects that predate this cycle.
**No option defaults changed.** Behaviour changes to note up front:
`JSON.stringify` and other machine-readable output now format
invariantly under every host culture — under Swedish or Finnish locales
on .NET 8+ it used to emit a Unicode minus sign no JSON parser accepts;
`JSON.parse` now rejects trailing commas as the grammar requires; bare
identifiers at global scope resolve through the global's prototype chain
per spec; `IModuleLoader.Resolve` is consulted once per (referrer,
specifier) pair, so a loader using it as a per-import access-control
checkpoint should move the check to `LoadModule`; and an inconsistent
sort comparator now finishes with an implementation-defined order on
every target framework instead of hanging (net462/netstandard) or
throwing a CLR exception at script (net8+).

### Highlights

**Proper tail calls (#​2975).** Strict-mode calls in tail position reuse
their frame, so `"use strict"` tail recursion runs in constant stack —
the first ES2015 PTC implementation among the .NET engines.

**Asynchronous module loading (#​2872).** `IAsyncModuleLoader` and the
`AsyncModuleLoader` template let a host fetch module source over I/O
without blocking a thread; `Engine.Modules.StartImport` returns an
operation a game loop drives via `ProcessTasks()`, and `ImportAsync`
awaits without holding a thread. The spec's load phase now exists as
written, a warm-cache async loader keeps the blocking `Import` fully
synchronous, and the blocking drain wakes on a work-arrived signal
instead of polling. A module served over a transport keeps its whole url
as `Module.Location` so its own relative imports resolve, a deferred
namespace evaluates its module instead of exposing uninitialized
bindings, and an import abandoned by a global snapshot restore reports
itself faulted instead of polling forever.

**The process no longer dies for recoverable reasons.**
`Options.LimitRecursion` used to kill the host process for most useful
limits — the constraint fired, and the unwind itself overflowed the
stack; exception filters now let it unwind ~7× deeper. The new opt-in
`Options.Constraints.StackOverflowGuard` converts unbounded recursion —
reachable through eighteen distinct routes, `new`, accessors, coercions
and Proxy traps included — from a process kill into a catchable
`RangeError`, exempting strict tail calls, which grow no stack. And a
family of CLR exceptions that escaped `engine.Evaluate` past every
script `catch` are now proper JavaScript errors or correct results:
sorting with an inconsistent comparator, destructuring with a
function-valued default (`const { onChange = () => {} } = opts`),
`toLocaleString` outside `DateTime`'s range, typed-array
`defineProperty` without a value, `DataView` reads at 2³¹,
`String.replace` `$'` with a lying exec, and the first instant of year
10000.

**New built-ins.** `Iterator.prototype.join`, `chunks`, `windows` and
`includes`; `take`/`drop` now throw `RangeError` for a finite limit
above 2^53−1 per the updated proposals.
`Intl.Locale.prototype.getCollations` reports CLDR-cited collation data
that `Intl.Collator` accepts in full, a malformed `collation` option is
a `RangeError`, and `Intl.supportedValuesOf("collation")` derives from
the same lists so the three can never drift.

**Conformance, from a review that ran what the suite does not.** Two of
the fixed defects had test262 coverage only under the never-generated
`staging/` directory, and several had none at all: `parseInt` strips the
sign before testing for a hex prefix, so `parseInt("-0x10")` is −16; a
suspended `finally` no longer swallows a pending `break`/`continue`; a
Proxy (or exotic host object) as the global's prototype answers bare
identifiers through its `get` trap; `Date.prototype.toISOString` emits
the spec's six-digit expanded year and round-trips through `Date.parse`
in every spelling including year 0; iterator helpers close their
receiver exactly once and only when the spec says so, and carry their
own `@@​toStringTag`; `Map`/`Set` `size` is the prototype accessor the
spec defines rather than a phantom own property; a Proxy's
`defineProperty` trap receives the partial descriptor the caller wrote;
a string's `@@​iterator` is read once, with the primitive as receiver;
`Array.prototype.join` re-asks the array when a side effect fills a hole
mid-join; a direct eval reaches the enclosing function's `arguments` in
both modes; and `Temporal.Now` drops the methods the proposal removed.

**Embedder surface.** `OperationDeadlineConstraint` bounds a whole
multi-entry host operation; `ScriptPreparationOptions.StaticAnalysis`
trades prepare-time analysis for per-engine materialization on shared
graphs; `ModuleFactory.LocationOf` exposes the module-naming rule a host
must match; `Engine.Advanced.HostDefined` carries per-request state on a
pooled engine; the CLR exception behind an interop error is reachable
through `JintException.TryGetClrException` with opt-in
`ChainClrExceptions()`, and a host method's own `TargetException` is no
longer mistaken for a receiver mismatch; and a recursion-limit failure
propagates out of a module load instead of becoming a catchable
rejection.

**Performance, gated.** Against v4.15.3 on idle hardware, medians of
three paired runs: `controlflow-recursive` **−15.6% time and −40.4%
allocation** (proper tail calls), `bitops-3bit-bits-in-byte` −8.9%,
`math-spectral-norm` −7.3%, `crypto-sha1` −6.9%, `3d-raytrace` −5.9%,
`math-cordic` −5.8%, with a broad −1–4% tail across the call- and
string-heavy rows; no row moved outside its own measured cross-run
envelope in the other direction, and allocation is flat within ±0.2%
suite-wide. Warmed `parseInt` call sites take the frameless fast-call
lane (−13% on the parse loop), joined by the `Number` predicates,
`String.prototype.indexOf`/`startsWith`/`endsWith`/`includes`/`at`/`substr`,
global `isNaN`/`isFinite` and `Array.isArray` (−3% to −19%) and the
`Map`/`Set` method family (`map.get` hit loop −13%); existence questions
on a wrapped dictionary answer from `ContainsKey`, taking `in` −33% with
−98% allocation and `Object.keys` −37%; resolving an inherited global no
longer allocates per miss (−99.99% on the read loop) and a global
created through an inherited write keeps the in-place store; JSON
replacer/reviver eligibility is decided once per document, built-in
callback dispatch once per loop, a call site's arguments reach an
interpreted callee in registers, and function-local `let`/`const` live
in fixed slots.

**Breaking changes.**
`Int32Extensions`/`Int64Extensions`/`DoubleExtensions` — polyfill hosts
that leaked into the public API — are now internal; on
net462/netstandard2.0, code with `using Jint;` may have bound span
`Parse`/`TryParse` members through them. `JsonParser` rejects trailing
commas. `Number.parseInt.length`/`Number.parseFloat.length` report their
spec values. Post-construction mutation of an `Options` instance no
longer reaches an already-built engine, and `Options.Configure`
callbacks work again. `UnwrapIfPromise` reports a cancelled engine as
`ExecutionCanceledException` instead of a timeout. Time-zone matching is
ASCII-case-insensitive per ECMA-402.

On the [engine comparison
benchmarks](https://github.com/sebastienros/jint/blob/main/Jint.Benchmark/README.md),
Jint 4.16.0 is the fastest engine outright on 5 of 12 scripts — leading
`dromaeo-object-regexp-modern` over native V8 by 1.25× — in a
statistical tie for first on `interop-collection-traversal`, the fastest
managed engine on 10 of 12, the fastest interpreter on all 12, and
8.6×–11.2× ahead of ClearScript (native V8) on every interop row while
allocating 3.9×–12.4× less than the nearest managed competitor.

## What's Changed
* Run the repository's own host tests under Release-mode contract
verification by @​lahma in
sebastienros/jint#2866
* Update test262 suite and implement Iterator.prototype.join by @​lahma
in sebastienros/jint#2867
* Stop a closing iterator from swallowing the error that closed it by
@​lahma in sebastienros/jint#2868
* Give every benchmark row its own engine by @​lahma in
sebastienros/jint#2873
* Hand a call site's arguments to an interpreted callee in registers by
@​lahma in sebastienros/jint#2874
* Ask once per loop, not once per element, how to call a built-in's
callback by @​lahma in sebastienros/jint#2876
* Say which spec document to read for a feature by @​lahma in
sebastienros/jint#2882
* Run PR CI on every pull request, not only those targeting main by
@​lahma in sebastienros/jint#2883
* Update test262 suite and adopt the new take/drop RangeError by @​lahma
in sebastienros/jint#2877
* Implement Iterator Chunking by @​lahma in
sebastienros/jint#2878
* Say to write against the modern BCL and polyfill downwards by @​lahma
in sebastienros/jint#2884
* Implement Iterator Includes by @​lahma in
sebastienros/jint#2879
* Ask once per document, not once per key, how to call a JSON replacer
or reviver by @​lahma in sebastienros/jint#2885
* Use double.IsFinite instead of hand-rolled NaN and infinity pairs by
@​lahma in sebastienros/jint#2880
* Bump the testing group with 1 update by @​dependabot[bot] in
sebastienros/jint#2889
* Stop charging closures for per-engine lazy globals by @​lahma in
sebastienros/jint#2890
* Bump the analyzers group with 1 update by @​dependabot[bot] in
sebastienros/jint#2888
* Make the lazy-global re-arm on restore a contract instead of an
accident by @​lahma in sebastienros/jint#2892
* Let the amortized constraint cadence span top-level entries into the
engine by @​lahma in sebastienros/jint#2886
* Let a function's own let/const live in its fixed slots by @​lahma in
sebastienros/jint#2887
* Keep a host function in the engine's own realm after a second realm
exists by @​lahma in sebastienros/jint#2893
* Make an engine's principal realm [[HostDefined]] reachable by @​lahma
in sebastienros/jint#2891
* Carry a labelled break/continue target on the completion record by
@​lahma in sebastienros/jint#2894
* Make Array.prototype.sort stable on every target framework by @​lahma
in sebastienros/jint#2898
* Stop toSorted and %TypedArray%.sort hanging on an inconsistent
comparator by @​lahma in sebastienros/jint#2899
* Delete the evaluation context's dead completion channel by @​lahma in
sebastienros/jint#2895
* Stop shipping the numeric polyfill hosts as public API by @​lahma in
sebastienros/jint#2901
 ... (truncated)

Commits viewable in [compare
view](sebastienros/jint@v4.15.3...v4.16.0).
</details>

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</details>
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