quest(cpp): C++ errors carry their message

[kixelated]

Problem

#4187 found that the generated C++ has no Display for moq::Error, so callers print variant names.

Approach

Adds quest/m1/cpp/error-message.md [XS].

Impact

• None (quest docs only).

Alternatives

• None.

Follow-ups

• None.

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	⚠️ Failed 2026-09-25T22:45:32.557744Z	648e6d4	PR opened

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[kixelated]

MERGE

Positive improvement: yes. #4187 already showed that moq::Error only prints the variant name, so callers and the interop client log noise instead of a reason. Capturing that as a tracked XS quest is the right follow-up before the package ships hard-to-debug failures into OBS and doc samples.

Worth the complexity: yes, and the complexity is appropriately tiny. Docs only (+22/−0), size [XS], and the plan prefers one moq-ffi message surface the generator already binds over hand-written per-variant strings in the wrapper. That matches the parent quest’s “fix shape problems in moq-ffi, not in cpp/moq” rule and stays additive on the public API.

Different approach: folding this into a bullet on package.md would also work, but a separate quest keeps the package PR from growing a second deliverable and makes the Display gap findable from the C++ README. No wire change, no alternative that looks better.

Ship it.

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Landing this onto quest/m1/cpp/README. It records an XS quest so a C++ moq::Error prints the same message Rust's Display gives, through one moq-ffi surface the generator already binds, instead of per-variant strings in the wrapper. Docs only; no wire change. Check and Test are green.

(Written by Grok 4.7)