Support new "using" keyword for disposable objects

[hazae41]

Rollup Version

3.28.1

Operating System (or Browser)

macOS

Node Version (if applicable)

20.3.1

Link To Reproduction

https://stackblitz.com/edit/rollup-repro-zruwr9?file=src%2Fmain.ts

Expected Behaviour

It should build successfully if using TypeScript 5.2 and latest tslib, @rollup/plugin-typescript

Actual Behaviour

Error on build: RollupError: Unexpected token (Note that you need plugins to import files that are not JavaScript)

[hazae41]

It also crashes on latest rollup@4.0.0-13

RollupError: Expected ';', '}' or <eof>

[TrickyPi]

For Rollup V3, we need to wait for acorn.js to support parsing using. But it's in stage 3 for JavaScript, I'm not sure the team of acorn.js will support it right away. If you are stuck with this issue, you can change the option compilerOptions.target in the tsconfig.json to ES2022 as a workaround. For Rollup V4, which is under development, SWC can parse it with the option jsc.parser.usingDecl, I'll take a look at this issue on Rollup V4.

[hazae41]

Thanks for the tip, ES2022 target works! But for people reading this, for some reason ESNext doesn't 🤨

[hazae41]

microsoft/TypeScript#55609

The issue seems to be related to either tslib or @rollup/plugin-typescript, since it works in tsc

[dnalborczyk]

Thanks for the tip, ES2022 target works! But for people reading this, for some reason ESNext doesn't 🤨

ESNext essentially only strips the types, so the runtime you are running the transpiled code in needs to support the using syntax. there is no runtime support as of today as far as I know.

[Hebilicious]

@TrickyPi I am not familiar at all with the rollup codebase, but do you have any idea on how we could have this supported in rollup 4 ? ie setting usingDecl to true in the internal rollup parser ?

[github-actions]

This issue has been resolved via #5444 as part of rollup@4.14.0. You can test it via npm install rollup.