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=5.7.2&fileType=.ts&code=CYUwxgNghgTiAEYD2A7AzgF3gWygTwCMQBBGGALnkxgEsUBzAbQF14AfeAVxVADM6QwANwAoUJFgJk6LLApUMtBi1EiA9Gvi8oNCGkRIy4DBDwjeh%2BAAppmeDQwhs9lPDkBKeAG8AviPWaaAAWSJwQwFo6EAA0VFDYCADuDkHwAAYAKizs8ChhEGnmljaodg5OLjj4RKQwnr7%2BGvAADkiOKBg0UBCmVJz09CCYalCcGEj8AB7w4zNBCBY9SMkMAPxFMNa2WOXOE1WEJGTwq6vwLPV%2BQA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1oDMPpbmtAIbRoQwuiiJRfSODABfEAqA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

declareconstmaybeArr:string[]|undefined;declareconstarr:string[];// fails correctlyfor(constiteminarr){}// should fail, same with `T[] | null`for(constiteminmaybeArr){}// potentially suggest/autofix to the following?for(constitemofmaybeArr??[]){}

ESLint Config

module.exports={parser:"@typescript-eslint/parser",rules:{"@typescript-eslint/no-for-in-array":"error",},};

tsconfig

{"compilerOptions": {"strictNullChecks":true  }}

Expected Result

I expected the rule to report, as it doesn't make sense to iteratenull orundefined. A fixer would be nice (in general, not just for this special case) since most of the time, the intent is to usefor-of.

Actual Result

The rule fails to catch these cases.

Additional Info

Currently, the rule checks specifically for an array or union of arrays. I think this can be expanded to a union with an array and potentiallynull andundefined.