Fix wrong variable name and API in README.invariant.md "Documenting impossible states" example

[ooloth]

What

• Corrects emojiMap.get(symbol) to emojiLabel[symbol] in the "Documenting impossible states" code block — the real code uses plain object bracket access on emojiLabel, not a Map API call on a nonexistent variable

Why

• A reader copying this snippet would get a reference error: emojiMap does not exist in the codebase and emojiLabel is a plain object, not a Map

How to validate

• Open utils/errors/README.invariant.md and find the "Documenting impossible states" block — expect const ariaLabel = emojiLabel[symbol] (plain object access, correct variable name)
• Open ui/elements/emoji.tsx line 30 — expect the same expression emojiLabel[symbol], confirming the example matches the real code

Closes #29

Related links

• Fix wrong variable name and API in README.invariant.md "Documenting impossible states" example #29
• https://claude.ai/code/session_01Ajyob6XtCXqtQ87VKqXQrL

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Generated by Claude Code

[claude]

Code Review

Overview

This is a single-line documentation fix in utils/errors/README.invariant.md. It corrects a code example that used a nonexistent variable (emojiMap) and the wrong API (.get() from Map) — replacing it with the actual expression from ui/elements/emoji.tsx (emojiLabel[symbol], plain object bracket access).

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Correctness ✅

Verified against ui/elements/emoji.tsx:

• Line 3: const emojiLabel = { ... } — plain object, not a Map
• Line 30: const ariaLabel = emojiLabel[symbol] — matches the fix exactly

The old example would throw ReferenceError: emojiMap is not defined if copied verbatim. The new example is accurate.

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Code Quality

• Minimal and focused — one line changed, no unrelated edits.
• No style issues — the surrounding markdown is untouched.
• The comment on the line below (// Documents that our emoji map should be complete) uses the word "map" loosely (meaning "lookup table"), which is slightly confusing given the bug just fixed, but it's pre-existing and not introduced by this PR. Worth a follow-up if it causes confusion.

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Suggestions

None required for this fix. One optional improvement to consider separately:

• The comment // Documents that our emoji map should be complete could be clarified to // Documents that emojiLabel should cover all EmojiSymbol values to avoid the ambiguity between "map" (the data structure) and "map" (the lookup table). That's out of scope here though.

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Verdict

LGTM. Simple, correct, well-scoped fix. Safe to merge.

[Copilot]

Pull request overview

Updates the invariant usage guidelines to ensure the “Documenting impossible states” example matches the real emoji implementation in the UI codebase, preventing copy/paste errors from the documentation.

Changes:

• Replaces the incorrect emojiMap.get(symbol) example with emojiLabel[symbol] to reflect the actual data structure and variable name used in ui/elements/emoji.tsx.

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