Before You File a Bug Report Please Confirm You Have Done The Following...

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I havesearched for related issues and found none that matched my issue.
• I haveread the FAQ and my problem is not listed.

Playground Link

https://typescript-eslint.io/play/#ts=5.6.3&fileType=.tsx&code=GYVwdgxgLglg9mABMAFAQwPwC5EG9EBGOAzlAE4xgDmiAPomCADZOIC%2BAlDgG5wwAmeAFCJEMYInSIAhAF5ZicPwCmwSssEAyTYjQA6AjPkNmTDsNGiICYnCbK9TOFXQGOI9kLZCgA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Y6RAM0WloHsalfkwCG8WmQAWo5uii9o-aJHBgAviHVA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eFYDAruuGAL4g9A&tokens=false

Repro Code

functionf(a?:{b:string|null}):void{if(a!==undefined&&a.b!==null){console.log(a.b)}}

ESLint Config

module.exports={"rules":{"@typescript-eslint/prefer-optional-chain":"error"}}

tsconfig

{"compilerOptions": {"strict":true  }}

Expected Result

No fix.

Actual Result

prefer-optional-chain produces this fix:

 function f(a?: { b: string | null }): void {-  if (a !== undefined && a.b !== null) {+  if (a?.b !== null) {     console.log(a.b)   } }

This is unsound because ifa isundefined, thena?.b isundefined, notnull.

Additional Info

No response