Array.flatMap incorrectly narrows types.

[bweis]

🔎 Search Terms

• flatMap
• Array.flatMap

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about flatMap

⏯ Playground Link

https://www.typescriptlang.org/play/?target=6&ts=5.7.3#code/C4TwDgpgBAglC8UDeAoK6qkgLigIhjzQwDcBDAGwFcJcBnYAJwEsA7AcxQF8UUtoAQgmTF0-XHgFEMUctVpQGLDqKhs6zACYKAwgG0Aut178oO4ahlyauVlQC2AIwiNjvAMYB7VgyhlGjGQguDABQQA8cAA+UAIAfMJ6SOL4hAA0spQ2+ACMeFwZyeAKBHgZ1iUATPmFKZJlmfISeRnqWgpJFbgAzAXIXVAALFwGfUU4+FLlWVUNbdq4nTO4AKxjAwDsIyO8KAD0e2ZkdNA5uAAinhB0UKyewFAA7p6MANYoXj4PAGaensL+QIgAB03woZGAAFkyGAABSwioASgQCUsGGY3ygCJmwNM8HxqTwyLRMnQjAgwCojFYjRoqi4UAgFBOakx2PkuOKCAJ9WJqhk5Mp1NpEGB8wg9NUn18AH0qKxyWR3AALMiOCgKVgQEguYQVVSCqk0uUKiBK1XqiVcRG7A5HFmVXAAJQgAEcqMxyTcIAAPMAUZjuZgPbTfNjB5jeTD-Z5vD7eXyOfwAsIgsEQ6FgSJQGI6OLwpEokQyDFYiqcyDcxClPmkjCG4X6mQMpks0vsmgV6D46tSWt1qANmnl8WSmTSh4mxUqtUa2za3WIJv1ilGqBTs0zy3cG22w46Y7Qbq4ADyjCg9hhGWAyogNPTwGB8a+UCTAC8U0DgZe4R2IMj4FRVR23LPEeUIfs6yHEV6UZZloBAnEwN7IliwHaCRx8doxwwCd13lacLTnW4F3PJcZgNVdhQ3c1ZytRFQXBYBYURIA

💻 Code

// Your code here

🙁 Actual behavior

I replicated additional cases in the playground link. I would expect the type narrowing to work in case 1, as it does in case 2 and case 3.

🙂 Expected behavior

I replicated additional cases in the playground link. I would expect the type narrowing to work in case 1, as it does in case 2 and case 3.

Additional information about the issue

No response

[jcalz]

duplicate #31033

[typescript-bot]

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