Continuation can resume more than once

Rule ID: concurrency.double-continuation-resume@1.0.0. Availability below refers to source-scan at product 524fa07e.

V-ASYNC-07 — Continuation can resume more than once#

Continuation can resume more than once. It examines task ordering, suspension, cancellation, progress, and async obligations.

Availability#

Not available in source-scan. There is no source-scan flag to activate this condition.

A separate experimental source preview recognizes a limited local pattern for this condition:

"$ANALYZER" experimental-scan <path> --rule async.continuation-double-resume --format json

Use the terminal from Installation, with ANALYZER set, and replace <path> with a Swift file or directory. This preview is not compiler-backed source-scan coverage.

Example and action#

Illustrative design scenario, not a runnable Swift example or a reproduced analyzer result. The stated availability and evidence boundaries still apply.

Before: A success callback and a timeout both retain the same continuation and can each resume it.

Review the following change against the contract and build variants described above.

After: Give completion a single synchronized owner that atomically chooses the winning outcome. Resume once outside the protected state transition and release the losing callbacks; include cancellation in the same protocol.

Intended analysis#

Intended reasoning: Follow the relevant state, task or synchronization events across control-flow and suspension boundaries. The intended decision needs the complete event ordering and the operation contract; opaque events can leave the result unknown. Required evidence: task, suspension, cancellation, ordering, and progress facts

Assumptions and unknown#

The relevant facts must be admitted for the selected immutable build world. Unknown aliases, external effects, unsupported source forms or incomplete consumers can prevent a conclusion. Availability in this workflow is stated above; the illustration does not expand that availability.

Evidence and interpretation#

The target catalog describes the intended condition. It is not evidence of an active source-scan diagnostic.

Historical evidence at 4558458d: recovery-required (historical qualification is incomplete and needs further evidence). That evidence has not been requalified for this product revision.

How we validate checks explains the evidence boundary. Foundations separates method assumptions from implementation claims.