“using” fails to compile because your app is parsing a JavaScript feature that the current toolchain does not fully support yet.

If you reproduce this in a Next.js or React app and add the using keyword, the build typically breaks before runtime. The reason is not your syntax alone: this feature depends on the Explicit Resource Management proposal, and your framework compiler, parser, transpiler, or minifier may not yet understand it end to end.

Understanding the Root Cause

The using keyword is part of the JavaScript proposal for deterministic cleanup of resources. It allows objects implementing Symbol.dispose or Symbol.asyncDispose to be cleaned up automatically when execution leaves scope.

That sounds straightforward, but modern web apps are compiled through multiple layers:

• TypeScript parses the source
• SWC or Babel transforms it
• Next.js bundles and optimizes it
• Terser or another minifier may parse it again

If even one step in that pipeline does not support using declarations, compilation fails. In practice, this issue often appears in frameworks that rely on SWC, because support for new ECMAScript proposals can lag behind TypeScript parser support.

In other words, the bug is usually caused by a toolchain compatibility gap, not by an invalid application pattern.

Step-by-Step Solution

The safest fix today is to avoid the using keyword in a Next.js app unless your exact framework version, compiler, and runtime all support it.

1. Confirm the feature is what breaks compilation

A minimal failing example usually looks like this:

class Resource implements Disposable {
  [Symbol.dispose]() {
    console.log('disposed');
  }
}

export default function Page() {
  using resource = new Resource();
  return <div>Hello</div>;
}

If removing the using line makes the app compile again, you have confirmed the parser or transformer is the problem.

2. Replace using with try/finally

This is the most reliable workaround and is functionally close to what the proposal provides.

class Resource {
  dispose() {
    console.log('disposed');
  }
}

export default function Page() {
  const resource = new Resource();

  try {
    return <div>Hello</div>;
  } finally {
    resource.dispose();
  }
}

For asynchronous cleanup:

class Resource {
  async dispose() {
    console.log('disposed');
  }
}

export default async function Page() {
  const resource = new Resource();

  try {
    return <div>Hello</div>;
  } finally {
    await resource.dispose();
  }
}

This approach avoids unsupported syntax while preserving explicit cleanup logic.

3. Check your TypeScript version

If you are experimenting with this feature, make sure your project is on a TypeScript version that can at least parse the syntax. For example:

{
  "devDependencies": {
    "typescript": "^5.2.0"
  }
}

Then verify your compiler options:

{
  "compilerOptions": {
    "target": "ES2022",
    "lib": ["DOM", "ES2022"]
  }
}

Important: even if TypeScript accepts the syntax, your app can still fail later in the Next.js build pipeline.

4. Upgrade framework dependencies if support has landed

If you want native support, update the packages most likely involved in parsing and transforming code:

npm install next@latest react@latest react-dom@latest typescript@latest

Then test again. If the failure persists, the relevant compiler stage still does not support using.

5. Track upstream support instead of forcing the syntax

When the issue is framework-level, the real fix must land upstream. Review release notes for:

• Next.js
• SWC
• TypeScript
• Your deployment runtime

If needed, keep a fallback implementation with try/finally until official support is stable.

6. Use a safe abstraction for cleanup

If you want cleaner code without depending on proposal syntax, wrap disposal behavior in a helper:

async function withResource(createResource, run) {
  const resource = await createResource();

  try {
    return await run(resource);
  } finally {
    if (resource?.dispose) {
      await resource.dispose();
    }
  }
}

export default async function Page() {
  return withResource(
    async () => ({
      async dispose() {
        console.log('disposed');
      }
    }),
    async () => <div>Hello</div>
  );
}

This keeps resource cleanup explicit and framework-compatible.

Common Edge Cases

• TypeScript parses it, but Next.js still fails: this usually means SWC or a later bundling step does not support the syntax.
• Development works, production build fails: your dev server and production optimizer may use different code paths or stricter parsing.
• Disposable types are missing: if you use Disposable, Symbol.dispose, or related APIs, your environment may lack the required typings or runtime support.
• Async cleanup confusion: await using and Symbol.asyncDispose need separate support from basic using.
• Third-party transpiler conflicts: custom Babel plugins, monorepo build tools, or older package transforms can reintroduce parse failures.
• Server versus client component issues: even if syntax support arrives, resource management semantics may differ between server-side execution and client bundles.

FAQ

Can I use the using keyword in Next.js today?

Only if your exact Next.js, compiler, and runtime versions support the full syntax pipeline. In many current setups, the answer is effectively no, so try/finally is the safest solution.

Why does TypeScript accept the code but the app still does not compile?

Because parsing in the editor or TypeScript compiler is only one step. Your framework still needs to transform, bundle, and sometimes minify that syntax. A later tool in the chain may reject it.

Is there a polyfill for using?

Not in the usual sense. Since using is syntax, support requires parser and transform support. You can polyfill some disposal behavior, but not reliably add unsupported syntax to a compiler that cannot parse it.

If you need a production-ready fix for this issue right now, replace using declarations with explicit cleanup using try/finally, upgrade the toolchain where possible, and monitor upstream compiler support before switching back.

For related framework updates, check the relevant project release notes and issue trackers through the official Next.js documentation and the TypeScript documentation.