fix(eslint-plugin): [no-misused-promises] expand union type to retrieve target property

[ntdiary]

PR Checklist

• Addresses an existing open issue: fixes Bug: [no-misused-promises] Specific function declaration syntax circumvents the rule with TypeScript strict enabled #11699
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

For union type, getPropertyOfType(type, name) can’t get property that exist only in one constituent. We need to manually expand the union and check each constituent, and unionConstituents helper is a good choice for this and also works with non-union type.

💖

[typescript-eslint]

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[nx-cloud]

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☁️ Nx Cloud last updated this comment at 2025-10-18 12:56:25 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.67%. Comparing base (3f5fbf6) to head (5f74775).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11706   +/-   ##
=======================================
  Coverage   90.67%   90.67%           
=======================================
  Files         518      518           
  Lines       52466    52466           
  Branches     8694     8696    +2     
=======================================
  Hits        47571    47571           
  Misses       4881     4881           
  Partials       14       14           

Flag	Coverage Δ
unittest	90.67% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ges/eslint-plugin/src/rules/no-misused-promises.ts	99.12% <100.00%> (ø)

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[JoshuaKGoldberg]

Thanks! Nice and clean, this is a good change. 🧼