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=4.7.2&sourceType=module&code=CYUwxgNghgTiAEYD2A7AzgF3gMyUgXPAN4CwAUPPFAPyGYwCWKA5uQL7nLpYBGs8AXhx4AdFCpp49JswA+AVxShsTEMHJA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0ipWkOTJE0fJQ5N0UOdA7RI4MAF8QOoA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3QAacDUjoAHgENmuAsXmoACpliIseAJ4AVPTuFhR6KQF8QloA

Repro Code

declare const foo: {
  a?: string
}
const bar = foo.a as string | undefined

ESLint Config

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

tsconfig

{
  "compilerOptions": {
    "strictNullChecks": true,
    "exactOptionalPropertyTypes": true
  }
}

Expected Result

no-unnecessary-type-assertion error

Actual Result

no error

Additional Info

even thought exactOptionalPropertyTypes changes the meaning of a?: string to be different to a?: string | undefined, that difference is not relevant when checking the type of foo.a, as it will be string | undefined in both cases

Versions