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=4.9.3&showAST=es&fileType=.tsx&code=HYQwtgpgzgDiDGEAEBBJBvAUEpEAeMA9gE4AuuwArmEgEIbY5IDCANIzgCLs4C%2Bm-TABMI8ADYhiyeIWBRyIAFyoAdLUyYoAdwCWpeAAskAChABKBjnggoyFGpXNlWJkgBGUkAGtG-XkA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6ZAd0vzIAt6AHrwCGsZPkoA3RExTJafRGQDW6KImjQA9tEjgwAXxAGgA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

namespace A {
  export enum B {
    C,
    D,
  }
}

declare const a: A.B

switch (a) {
  case A.B.C: {
    break
  }
}

ESLint Config

{
  "rules": {
    "@typescript-eslint/switch-exhaustiveness-check": "error"
  }
}

tsconfig

No response

Expected Result

switch (a) {
  case A.B.C: {
    break
  }
  case A.B.D: { throw new Error('Not implemented yet: A.B.D case') }
}

Actual Result

switch (a) {
  case A.B.C: {
    break
  }
  case B.D: { throw new Error('Not implemented yet: B.D case') }
}

Additional Info

In the actual codebase, the enum is namespaced under an ESM import *, rather than a TypeScript namespace. However, I think both cases should be fixed by any potential PR that fixes this