Array.prototype.find does not narrow return type

[EvgenyMuryshkin]

🔎 Search Terms

Array.prototype.find

Something similar might be here
#19456

🕗 Version & Regression Information

Currently migrating codebase strictNullChecks on 5.7.3. Potentially an old issue.

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/GYVwdgxgLglg9mABBOBDANgUwM4UwCgDpiYpMBbbALkX2ygCcYwBzRAH0TBHXQ8XAATTMGaZBASgDaAXQk16TVvyEixgxAG8AUIj2IGmKCAZJSFbIVFhB+GIgC8APkT2AhA4dcefAGS-XRA8vVWtxRH9Aj0QAIhiJAG5tAF8gA

💻 Code

function coalesce(...items: (string | null | undefined)[]): string | undefined {
    return items.find(i => i !== null && i !== undefined && i != "");
}

🙁 Actual behavior

Type 'string | null | undefined' is not assignable to type 'string | undefined'.
  Type 'null' is not assignable to type 'string | undefined'.(2322)

🙂 Expected behavior

null values are filtered out, so return type should exclude null

Additional information about the issue

No response

[MartinJohns]

https://github.com/Microsoft/typescript/issues?q=is%3Aissue%20state%3Aclosed%20array%20find%20in%3Atitle

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.