nextjs - 💡(How to fix) Fix Turbopack: panic on `**` (exponentiation) operator in node_modules when `compiler.styledComponents` is enabled [1 participants]

Link to the code that reproduces this issue

https://github.com/mhdsdt/turbopack-bigint-exponentiation-repro

To Reproduce

1. Clone the reproduction: git clone https://github.com/mhdsdt/turbopack-bigint-exponentiation-repro
2. npm install
3. npm run dev (runs next dev --turbopack)
4. Open http://localhost:3000 — the page returns a 500 error

The reproduction requires three conditions to trigger:

1. compiler: { styledComponents: true } in next.config.ts
2. styled-components installed as a dependency
3. Any code in node_modules that uses the ** (exponentiation) operator — in this case, [email protected] uses 10n ** 18n

Switching to webpack (next dev without --turbopack) works fine.

Current vs. Expected behavior

Current: Turbopack panics with a Rust todo!() and returns a 500 error:

thread 'tokio-runtime-worker' panicked at
  swc_ecma_compat_es2015/src/generator.rs:507:21:
  not yet implemented: right-associative binary expression

The full debug trace:

failed to analyze ecmascript module
  '[project]/node_modules/permissionless/_esm/actions/pimlico/estimateErc20PaymasterCost.js [client] (ecmascript)'

Caused by:
- not yet implemented: right-associative binary expression

Debug info:
- Execution of <ModuleAssetContext as AssetContext>::process_resolve_result failed
- Execution of *EcmascriptExports::split_locals_and_reexports failed
- Execution of analyze_ecmascript_module failed
- Execution of <EcmascriptModuleAsset as EcmascriptParsable>::failsafe_parse failed
- Execution of parse failed
- not yet implemented: right-associative binary expression

Expected: The page should compile and render successfully. The ** operator is standard ES2016 JavaScript and has been supported in all modern browsers since 2016. The SWC generator transform should handle it rather than panicking.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.3.0
  Available memory (MB): 24576
  Available CPU cores: 10
Binaries:
  Node: 20.20.0
  npm: 10.8.2
  Yarn: 1.22.22
  pnpm: 10.24.0
Relevant Packages:
  next: 16.1.6
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected?

Turbopack, SWC

Which stage(s) are affected?

next dev (local), next build (local)

Additional context

Root cause: The ** operator is the only right-associative binary operator in JavaScript. In SWC's ES2015 generator transform (swc_ecma_compat_es2015/src/generator.rs), all binary expressions are handled via visit_left_associative_bin_expr(), but ** is explicitly marked as todo!("right-associative binary expression") at line 507. When Turbopack's module analysis triggers this code path (via the styledComponents compiler option), it panics.

Confirmed on canary: Tested on [email protected] — the bug still exists (the todo!() is at the same location in swc_ecma_compat_es2015-42.0.0).

Real-world impact: This blocks Turbopack adoption for any project using styled-components alongside Web3/crypto libraries. Affected packages include:

• permissionless (uses 10n ** 18n)
• @noble/curves (uses _2n ** BigInt(254) extensively — foundational crypto library)
• @walletconnect/utils (bundles noble-curves code)

Related:

• SWC source: swc_ecma_compat_es2015/src/generator.rs:507 — the todo!() that panics
• pimlicolabs/permissionless.js#499 — same error reported on the library repo (wrong place; the bug is in SWC/Turbopack)