Link to the code that reproduces this issue

https://github.com/SiroSuzume/next-build-bug-example

To Reproduce

1. Clone the repository above
2. Install dependencies with pnpm install (or npm install)
3. Run the production build with pnpm build
4. Observe the build fails with "ReferenceError: range is not defined" during prerendering

Current vs. Expected behavior

Current behavior: Following the reproduction steps, the build fails with:

Error occurred prerendering page "/". 
ReferenceError: range is not defined
    at <unknown> (.next/server/app/page.js)

The SWC minifier incorrectly transforms closures when they're called 3 or more times. The parameter range is renamed in the function signature but NOT in the closure body, causing the reference error.

Expected behavior: The build should complete successfully. The minifier should properly rename all references to the range parameter throughout the closure, regardless of how many times the closure is called.

Key finding:

• With 2 closure calls: Build succeeds ✅
• With 3+ closure calls: Build fails with ReferenceError ❌

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.3.0: Thu Jan  2 20:24:06 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T8103
  Available memory (MB): 16384
  Available CPU cores: 8
Binaries:
  Node: 20.19.4
  npm: 10.8.2
  Yarn: 1.22.17
  pnpm: 10.13.1
Relevant Packages:
  next: 15.6.0-canary.12 // Latest available version is detected (15.6.0-canary.12).
  eslint-config-next: N/A
  react: 19.1.1
  react-dom: 19.1.1
  typescript: 5.9.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

SWC

Which stage(s) are affected? (Select all that apply)

next build (local), Vercel (Deployed)

Additional context

Pinpointed version where bug was introduced:

• Last working version: Next.js 15.4.0 ✅
• First broken version: Next.js 15.4.1 ❌ (when SWC was updated to v1.11.24)
• Still broken in: 15.4.3, 15.5.3, 15.6.0-canary.12

The specific code pattern that triggers the bug:

const decideZoomByAccuracy = (range: number): number => {
  const isUnder = (accuracy: number): boolean => {
    return range <= accuracy;  // 'range' is not renamed in minified output
  };
  
  if (isUnder(0)) return 15;
  if (isUnder(50)) return 15;
  if (isUnder(100)) return 15;  // 3rd call triggers the bug!
  return 11;
};

Repository structure:

• app/page.tsx - Reproduces the bug (3 closure calls → fails)
• app/working-example.tsx - Demonstrates it works with 2 calls

Important findings:

1. Setting serverMinification: false does NOT fix the issue
2. The bug only occurs when the closure is called 3 or more times
3. With exactly 2 calls, the build succeeds
4. The issue affects both local builds and Vercel deployments

Current workarounds:

1. Refactor to avoid closures referencing parent parameters
2. Limit closure calls to 2 or fewer
3. Use Next.js 15.4.0 or earlier