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 havesearched for related issues and found none that matched my issue.
• I haveread the FAQ and my problem is not listed.

Playground Link

https://typescript-eslint.io/play/#ts=5.7.2&fileType=.ts&code=JYOwLgpgTgZghgYwgAgEIHsAeyDeAoZZANzgBsBXCALmQGcwpQBzAbjwF888ATCBUuFBQxyIBGGDoQyJhDAAxMqQBGiANYZMACgCUNTWx58BQ5Ain1kveOVJhN%2BrMgA%2ByUddARuh63Fv2nZ1dZBSVVBA0sXTYAehjCBMSAPyS8OOQABSEYaDdaZmQQW1JgWgALM3QyCFoEAvQAB2g4MHQoZAA6Lq5ff01kAH4rCBs7fpoQxVIVdU1otPiAOXRkaCg25CotIA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Y6RAM0WlqYSNkAC1pkA9gEMkyMswDm6KL2jjokcGAC%2BILUA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

interfaceBox{value:string;}declarefunctiongetFallbackBox():Box;declareconstdefaultBox:Box|undefined;defaultBox||getFallbackBox();//         ~~// Prefer using nullish coalescing operator ...defaultBox ?defaultBox :getFallbackBox();// No error :(

ESLint Config

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

tsconfig

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

Expected Result

Both the|| or and the?: ternary should report.

Actual Result

Only the|| or reports.

Additional Info

Ternary support was added in#4905, but seems limited to more strict cases of bothundefined andnull being checked?

Split out of#10218 (comment).

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