[NUAAwqy]

Problem

trackReference walks a reference up while its parent is any member expression, without checking the
reference is the member's object, and then asks isAssignedMember. So for obj[rest] = 1 the computed
key rest is treated as if its own members were assigned. When rest is a <const> rest binding, valid
code fails to compile:

rest is a rest element, a copy rebuilt from the value it is destructured from whenever that changes,
so assigning its members would be lost.

The key is only read — nothing assigns rest. The same missing check also records a needless
addAssignedProperty de-optimization for ordinary keys (o[x] = 1, o[x]++, delete o[x]).

Fix

Stop the walk unless the reference is the member's object; a computed key is just a read. One line
(+ a two-line comment) in translator/util/references.ts. Node comparison is direct, per AGENTS.md.

Tests

New fixture rest-computed-member-key (html/dom/ssr/csr, generated snapshots) fails to compile before the
guard and passes after. Real member writes still error: --grep rest = 307 passing, including
error-assign-to-rest-element and error-assign-to-rest-element-member (rest.b = 5). Full
runtime-tags translator suite green, repo-wide oxlint/oxfmt clean, and build:sizes produces no
.sizes/.sizes.json delta (translator-only change, zero shipped runtime bytes).

Resolves the tracked agent-feedback item for this defect; the item file is deleted in this PR per
agent-feedback/README.md rule 8.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1d1606e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@marko/runtime-tags	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

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📒 Files selected for processing: 6

• .changeset/rest-computed-member-key.md
• agent-feedback/items/2026-10-21-stop-a-computed-key-from-counting-as-a-member-write.md
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• packages/runtime-tags/src/__tests__/fixtures/rest-computed-member-key/template.marko
• packages/runtime-tags/src/__tests__/fixtures/rest-computed-member-key/test.ts
• packages/runtime-tags/src/translator/util/references.ts

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• agent-feedback/items/2026-10-21-stop-a-computed-key-from-counting-as-a-member-write.md

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Walkthrough

trackReference now stops traversing a member expression when the reference is used as its key rather than its object. A new fixture renders values accessed with rest-binding keys and tests updates to those keys through a button click. The change also adds a patch changeset and removes the related bug-report document.

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to 1d160

Computed-key rest bindings can be used without being misclassified as assigned, and the fixture checks that their lookups update. No actionable merge risk remains; the change is ready for normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (3 skipped: 3 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main fix: computed member keys are treated as reads instead of member writes.
Description check		The description is directly related to the changes. It explains the defect, the fix, the regression fixture, validation results, and deletion of the tracked feedback item.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (3 skipped: 3 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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