"MemoryLifecycleGuard: Tasks That Never Cancel, Delegates That Never Die"

Retain cycles, un-cancelled tasks, and unbounded streams — the memory bugs that don’t crash, they just leak.

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Memory bugs in Swift rarely announce themselves. A stored Task that’s never cancelled keeps running after its owner is gone. A strong delegate quietly forms a retain cycle. An AsyncStream with no back-pressure grows without bound. The app doesn’t crash — it just gets slower, warmer, and stranger over hours.

What it catches

// ❌ lifecycle-task-no-cancel — a stored Task with no cancellation
final class Loader {
    private var task: Task
            
              ? func start() { task = Task { await load() } } // never cancelled } // ❌ lifecycle-strong-delegate — a strong delegate reference (retain cycle) var delegate: MyDelegate? // should be `weak var` // ❌ lifecycle-unbounded-stream — an AsyncStream with no termination path // ❌ lifecycle-task-no-deinit — a Task-owning type with no deinit to cancel it 
            

Representative rule IDs: lifecycle-task-no-cancel, lifecycle-task-no-deinit, lifecycle-strong-delegate, lifecycle-unbounded-stream, lifecycle-stream-terminated-elsewhere, lifecycle-delegate-retained-elsewhere.

Cross-file lifecycle analysis

The interesting part is what makes it precise. A Task stored in one file might legitimately be cancelled in another; a delegate declared strong here might be retained safely there. So the guard does cross-file analysis — the -elsewhere rules exist specifically to suppress a finding when the cancellation or the ownership actually lives in a different file. That’s the difference between a checker that nags and one you can leave on: it looks at the whole picture before it fires. Stale exemptions (lifecycle-stale-exemption) get flagged too, so suppressions don’t rot.

Try it

quality-gate --check memory-lifecycle

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Source: github.com/jpurnell/quality-gate-swift