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Bug: [no-unused-vars] doesn't report unused variables in module and ambient module declarations in definition files #10713

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@ronami

Description

@ronami

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=5.7.3&fileType=.d.ts&code=KYDwDg9gTgLgBAOwIYFtgGcxIMbDgMQgjgG8AoOOAeirimElmABM5tp7sYAbATwH4KcGLzB4AQkihwAvHACMAbiGhG8EnAC%2ByzWTLNg2blLwoIzAK7c8AcgBGUm6SE046ABYQrrO3npqWQUoRMThJaTklFXBodS0dPVcPL24fPwZYwLIQiSlZBWVVWNJ4siA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tidmUQAmtAG4BDaKgyRE0aB2iRwYAL4hlQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

export namespace Foo {
  // reported correctly?
  type Bar = 1;
  export { };
}

declare module 'bar' {
  // should be reported?
  type Bar = 1;
  export { };
}

// should be reported?
type Bar = 1;
export { };

ESLint Config

module.exports = {
  parser: "@typescript-eslint/parser",
  rules: {
    "@typescript-eslint/no-unused-vars": "error",
  },
};

tsconfig

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

Expected Result

I expected the rule to report on the Bar type as unused, similar to TypeScript's report.

Actual Result

The type Bar isn't marked as unused, though to my understanding it should be.

Additional Info

It seems the issue remains the same if the export {} is replaced with export default ..., or export * from '...'.

I think this is similar to #2867, and I've wrote some of my thoughts about it in #10714.

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