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=MYewdgzgLgBAhjAvDA5AIxQWAFA4CYCmwANnAE4EzEGwAeAXDAN7yPRkCWYA5gDQxo2UTjxgBfGAB8YYAK7FiOHLQD8AOgQBCZHIUwVMWgG04AXRiMUAMxAgsubAVoAHEGVgsxQA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Y6RAM0WlqYSNkAC1pkA9gEMkyMswDm6KL2jjokcGAC%2BILUA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

const a = 'b';

declare let x: { a: string, b: string } | null

x?.a != null ? x[a] : 'foo'

ESLint Config

module.exports = {
  parser: "@typescript-eslint/parser",
  rules: {
    "@typescript-eslint/prefer-nullish-coalescing": ["error"],
  },
};

tsconfig

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

Expected Result

x?.a != null ? x[a] : 'foo' should not report

Actual Result

x?.a != null ? x[a] : 'foo' reports

Additional Info

Raised in #10733 (comment)

Root cause: the rule doesn't handle well computed members.

A fix is ready in the perimeter of #10861: f69b588

✅ PR branch playground

Cc @kirkwaiblinger