It's neat, but if I understand it correctly, if you forget to write the "using" keyword the code will still work just fine but the dispose will never be called, resulting in a memory leak. I don't suppose there is a way to mark a function as being un-callable unless you do so with "using"?

Short answer: Yes, Disposable can leak if you forget "using" it. And it will leak if the Disposable is not guarded by advanced GC mechanisms like the FinalizationRegistry.

Unlike C# where it's relatively easier to utilize its GC to dispose undisposed resources [2], properly utilizing FinalizationRegistry to do the same thing in JavaScript is not that simple. In response to our conversation, Ron is proposing adding the use of FinalizationRegistry as a best practice note [3], but only for native handles. It's mainly meant for JS engine developers.

Most JS developers wrapping anything inside a Disposable would not go through the complexity of integrating with FinalizationRegistry, thus cannot gain the same level of memory-safety, and will leak if not "using" it.

IMO this design will cause a lot of problems, misuses and abuses. But making JS to look more like C# is on Microsoft's agenda so they are probably not going to change anything.

[1]: https://github.com/tc39/proposal-explicit-resource-managemen...

[2]: https://stackoverflow.com/a/538238/1481095

[3]: https://github.com/tc39/proposal-explicit-resource-managemen...