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Bug: [explicit-function-return-type] false negatives on inner function when using allowTypedFunctionExpressions option #8808

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@yeonjuan

Description

@yeonjuan

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=5.4.3&showAST=es&fileType=.tsx&code=GYVwdgxgLglg9mABMOcAUBKAXIgbnGAE0QG8AoRRCBAZykQCMBDAJ0QF5FMOA%2BLjXqUQB6YYgBycRAFEWLOCwA0yJgBsaAU0RgNAcyaxcGipUQsNUECyTUwNOKo0A6VXF1oA5CjgeMAbhMAXwDAsjJbOkZWDn5BbnY%2BEhExWXk2JhpEDQAPAAcNaA1CJxNzS2sqWgdnV3cvVF8QvyA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6RAD2MbMroDNYTMvkoB7JrWiJ8saJKKl0YANqRE0aGOiQANJnDYcAQ3jwxAdwAqJRABMAYkJHimAUS7TkyV6gz44REMIAF8AXUMQkBCgA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

function foo(): void {
  const bar = () => () => { // No Error, false negative
    return console.log('foo');
  };
}

const bar = () => () => { // Error as expected.
  return console.log('foo');
};

ESLint Config

module.exports = {
  parser: "@typescript-eslint/parser",
  rules: {
  "@typescript-eslint/explicit-function-return-type": ["error", {
      "allowTypedFunctionExpressions": true
    }]
  },
};

tsconfig

{
  "compilerOptions": {
    // ...
  }
}

Expected Result

Two errors (line 2, line 7)

Actual Result

One error (line 7)

Additional Info

If the allowTypedFunctionExpressions option is false, this bug does not occur. IMO, ancestorHasReturnType seems to be buggy when traversing ancestor nodes: when encountering a certain node type, it should return false without further traversal.

playground

function foo(): void {
  const bar = () => () => { // Error as expected
    return console.log('foo');
  };
}

const bar = () => () => { // Error as expected.
  return console.log('foo');
};

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