using in a for... of loop fails to call Symbol.dispose method (+ same problem for async versions)

[lionel-rowe]

Version: Deno 1.46.3

I initially thought this was a bug with TS, but compiling TS via the playground and running it in Chrome works correctly, as does running it in Bun.

Using using within a for... of loop fails to call the Symbol.dispose method. The same problem occurs when using awaiting using using await using using Symbol.asyncDispose:

class Disposable {
    disposed = false;

    [Symbol.dispose]() {
        this.disposed = true
    }
}

const disposables = [new Disposable()]

for (using _ of disposables) {/* ... */}

if (disposables[0]!.disposed) {
    console.log("✅ dispose ok")
} else {
    console.error("💥 failed to dispose")
}

class AsyncDisposable {
    disposed = false;

    [Symbol.asyncDispose]() {
        this.disposed = true
    }
}

const asyncDisposables = [new AsyncDisposable()]

for (await using _ of asyncDisposables) {/* ... */}

if (asyncDisposables[0]!.disposed) {
    console.log("✅ async dispose ok")
} else {
    console.error("💥 failed to async dispose")
}

Keywords: using, using using, using await using, awaiting using await using

[marvinhagemeister]

Seems like an SWC transpilation issue. I've put the reproduction code into their playground and the transpiled output matches exactly what we run in Deno. Running the transpiled output on its own inhibits the described error and the dispose hooks aren't called.

Filed an upstream issue here swc-project/swc#9576