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 have searched for related issues and found none that matched my issue.
• I have read the FAQ and my problem is not listed.

Playground Link

https://typescript-eslint.io/play/#ts=5.5.2&fileType=.tsx&code=GYVwdgxgLglg9mABMOcA8AVAfACgPoBciGAlIgN4BQiiECAzlIgB5EaIC8iYIANrwEIA3NVoMmATzadufQSIC%2BlIA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0ipWsRFCAtonyJoqDJCXQO0SODABfELqA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

function foo<T>(_: T) {
  const x: T = null!;
  const y: T = null!;
}

ESLint Config

module.exports = {
  "rules": {
    "@typescript-eslint/no-unnecessary-type-parameters": "error"
  }
}

tsconfig

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

Expected Result

T should be marked as an unnecessary type parameter. It's only used once in the type signature.

Actual Result

No report.

Additional Info

Repro case courtesy of @That-Guy977's #9664 (comment), thanks!

💖