[NathanWalker]

Summary

Swift interop stack — review bottom-up; each PR shows only its own commits. Merge in order; after a squash merge, rebase the next branch onto main. Design discussion: RFC NativeScript/rfcs#57.

1. feat(metadata-generator): Swift symbol graphs to thunks and TypeScript declarations (Swift interop 1/7) #518 generator: symbol graphs → IR → thunks + .d.ts
2. feat(runtime): ns:swift calls Swift through generated thunks (Swift interop 2/7) #519 runtime: ns:swift core
3. feat(swift-interop): modules, generics, protocols, Observation and SwiftUI (3/7) #520 modules, generics, protocols, Observation, SwiftUI
4. feat(swift-interop): generate and link thunks in app builds (4/7) #521 app builds
5. feat(swift-interop): returning closures, generic functions, tuples, Result and C structs (5/7) #522 more values: returning closures, generic functions, tuples, Result, C structs
6. feat(swift-interop): adapter lifetime, cancellation, subscripts, Combine and operators (6/7) #523 adapter lifetime, cancellation, subscripts, Combine, operators ← this PR
7. feat(swift-interop): Any, UUID and Decimal, performance, and docs (Swift interop 7/7) #517 Any/UUID/Decimal, performance, docs

Lifetime and call-shape work.

SwiftDemo.introduce(delegate, "ada");            // one adapter per JS object; weak Swift delegates live as long as JS holds them
await SwiftDemo.waitForCancel(10, controller.signal); // AbortSignal rejects and cancels the Swift task
shelf.setSubscript("apples", 3); shelf.subscript("apples"); // subscripts
for await (const v of publisher.values) { break; } // AsyncSequence types, Combine publishers, early exit ends the stream
a.plus(b); versions.sort((x, y) => x.compare(y)); // operators as named methods, Equatable/Comparable
SwiftDemo.sumAll([1, 2, 3]);                     // some Sequence<Int>, C: Collection, any Sequence<E> take arrays

Protocol adapters follow NativeScript's lifetime rule for the JS side of Objective-C objects (ABI 14). Async calls take a trailing AbortSignal (ABI 15).

Evidence

• Before: each call made a new adapter, so Swift saw a new identity each time (removeAll { $0 === listener } never matched), and a weakly held adapter was freed as soon as the call returned. Async calls could not be cancelled.
  After: 134 ns:swift TestRunner specs (17 new), covering adapter identity, weak delegates across GC, cancellation, subscripts, Combine and collection protocols.

Merge Danger

Door: two-way

Blast Radius: ns:swift

Adapters hold JS objects strongly while Swift shares them and weakly otherwise, so leak or early-release bugs would show here first.

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