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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 opened this issue Jan 26, 2025 · 0 comments · Fixed by #10714
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accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin

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@ronami
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ronami commented Jan 26, 2025

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.

@ronami ronami added bug Something isn't working package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin triage Waiting for team members to take a look labels Jan 26, 2025
@JoshuaKGoldberg JoshuaKGoldberg added accepting prs Go ahead, send a pull request that resolves this issue and removed triage Waiting for team members to take a look labels Feb 24, 2025
@github-actions github-actions bot added the locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. label Mar 11, 2025
@github-actions github-actions bot locked as resolved and limited conversation to collaborators Mar 11, 2025
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Labels
accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin
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