Cannot destructure properties of a resource obtained using the 'using' keyword

[electricmonk]

🔎 Search Terms

using destructure

🕗 Version & Regression Information

• I was unable to test this on prior versions because this is a new feature in 5.2

⏯ Playground Link

https://www.typescriptlang.org/play?#code/GYVwdgxgLglg9mABAcwKZQEqoM5xAJwlQAoBKRAbwChFbF90Clq7XFg44AuRAIgCMAhvl4AaGm1oBtAMoBPALb84AGwB0AExjYADnGyoAujzKIAvAD5KAX3GtrVB1RZ0Q2GGGT1zKdFlwERGQA3BK0EAi4KqhqKnDIxPhqHHCkoU7OYYhuHl4U7JyI1j5omDh4hCRpWRFgUTFxCSnV1kA

💻 Code

function getResource() {
 return {
 foo: "bar",
 [Symbol.dispose]: () => {},
 }
}

{
 using { foo } = getResource();
 console.log(foo);
}```


### 🙁 Actual behavior

> Error: 'using' declarations may not have binding patterns.(1492)


### 🙂 Expected behavior

Should be able to destructure a variable defined using the `using` keyword

### Additional information about the issue

_No response_

[MartinJohns]

This is working as intended. JavaScript does not support combining destructuring and using declarations. See This comment and the linked issues.

[electricmonk]

Fair enough.
It could be argued, though, that this is just another piece of sugar TSC can provide us with.
From the dev experience perspective, this behavior violate the principle of least surprise and I'm sure that many many developers will be surprised to learn about it.

[MartinJohns]

that this is just another piece of sugar TSC can provide us with.

It's not. That would require additional code to be emitted that goes beyond downleveling support for older runtimes. A clear no-go for TypeScript.

[guillaumebrunerie]

I guess one issue is that's it's unclear whether it's the result of getResource that should be disposed, or the foo variable. Technically, the statement only introduces a variable called foo, so it would make more sense to dispose foo, but it is not disposable.

[electricmonk]

To me it's very clear that the containing object is the disposable but maybe I'm in minority.

[typescript-bot]

This issue has been marked as "Working as Intended" and has seen no recent activity. It has been automatically closed for house-keeping purposes.