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Bug: [prefer-nullish-coalescing] has various bugs around multi-part nullishness checks #10733

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@kirkwaiblinger

Description

@kirkwaiblinger

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=5.7.2&fileType=.tsx&code=CYUwxgNghgTiAEYD2A7AzgF3igrhCA8jAQEYBW4GAXNnhPAD7wDe8UNmMAligObwBfANwAoEcnRYMITAEZ4AXlr4ipCmCwBCBUpwpQAMx4hg8AGRnl9bUtz4R8eAH4rq8pQfwaAFgBMo8VRMeGlMX0VXYncNeBt4AyQkc0s7ax0rTxdUt3UMTx9-IA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUFvcgAQBcBPABxQGNoBLEggWhXioDsCB6E6RAM0WjuYImyABZ1yAewCGSZORYBzdFADuU6M0jgwAXxA6gA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

declare const nullOrObject: null | { a: string };

const test1 = nullOrObject !== undefined && null !== null
  ? nullOrObject
  : 42;

const test2 = nullOrObject !== foo && null !== null
  ? nullOrObject
  : 42;

ESLint Config

module.exports = {
  "rules": {
        "@typescript-eslint/prefer-nullish-coalescing": "warn"
  }
}

tsconfig

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

Expected Result

I expect neither test should report

Actual Result

both do

Additional Info

Relates to #10724, but this is an existing bug, not a regression from recent work

cc @OlivierZal if you're interested

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