fix(net): keep track::Fetching unwind safe

[kixelated]

Problem

#4691 made track::Fetching hold a cached-hit group::Consumer. That consumer carries an Arc<dyn group::Expiry>, and the crate-private Expiry trait is not RefUnwindSafe, so Fetching lost UnwindSafe and RefUnwindSafe. cargo-semver-checks flags that as breaking, which is why release-plz #4596 bumps moq-net to 0.4.0 while its public dependents (moq-tokio, hang, ...) get patch bumps: downstream users would break on a patch update.

Approach

Add UnwindSafe + RefUnwindSafe supertraits to the crate-private group::Expiry (its one implementor, GroupExpiry, already satisfies them), matching the moq-audio Backend pattern. A unit test statically asserts Fetching and group::Consumer are unwind safe so this can't regress silently.

A backport to release follows so #4596 regenerates with a 0.3.x moq-net bump.

Impact

• track::Fetching regains UnwindSafe and RefUnwindSafe (as in moq-net 0.3.8).
• group::Consumer gains UnwindSafe and RefUnwindSafe (additive).
• No wire change.

Alternatives

• Wrap the held hit in AssertUnwindSafe inside Fetching: fixes only the symptom; group::Consumer stays !UnwindSafe for no real reason.
• Accept moq-net 0.4.0 on release: requires minor bumps on every public dependent.

Follow-ups

• moq-relay::drills relay_killed_mid_group_aborts_then_resumes::impaired flaked locally once with EADDRINUSE when restarting the relay on the same UDP port under parallel test load (passes in isolation). Unrelated to this change.

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between 1956381 and c5c7180.

📒 Files selected for processing (2)

• rs/moq-net/src/model/group.rs
• rs/moq-net/src/model/track.rs

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[kixelated]

Automated review by review (OpenAI)

Reviewed c5c7180. No actionable bugs found.

Direction: the private Expiry supertrait bounds in rs/moq-net/src/model/group.rs:1135 fix the trait-object boundary directly, letting the compiler enforce unwind safety instead of asserting it with AssertUnwindSafe. The compile-time assertions in rs/moq-net/src/model/track.rs:8087-8091 protect both public handle types. This is a small, justified compatibility fix with no runtime or wire changes.

Verification limits: static review of the patch and surrounding Consumer, Fetching, and GroupExpiry code only; I did not run Rust tests or cargo-semver-checks. The release-branch backport and regenerated #4596 version plan still need separate verification.

(Written by OpenAI)

[kixelated]

Merging: CI green, automated review found no issues. Fix is the supertrait bound on the private group::Expiry (chosen over AssertUnwindSafe on the held hit, which would leave group::Consumer needlessly !UnwindSafe). Backport to release is #4759, so release-plz #4596 can regenerate with a 0.3.x moq-net bump.

(Written by Claude Opus 5.5)