🔎 Search Terms

TS2488

🕗 Version & Regression Information

• This changed between versions 3.8.3 and 3.9.7 (tested with the playground)
• I was unable to test this with every-ts because this issue seems to affect only the editor, not tsc

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=3.9.7#code/CYUwxgNghgTiAEA3W8AeAueA7ArgWwCMQYBtAXXgB94BveAF0wHIon4BfeAMloeYLbsAUBBD14JEKLwUAvGiA

💻 Code

declare var x: number[] | { t: 'a' } & { t: 'b' }
let [elem] = x

🙁 Actual behavior

The array destructure fails with this error:

Type 'number[]' must have a '[Symbol.iterator]()' method that returns an iterator.(2488)

🙂 Expected behavior

No error should be present.

Since an object cannot have a field t that holds both 'a' and 'b', { t: 'a' } & { t: 'b' } reduces to never. And number[] | never decays to number[], which is iterable by definition.

Additional information about the issue

No response