microsoft / microsoft/TypeScript

Error when spreading a union of tuples in a call

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#42,508 6 comments 0 reactions 1 assignee View on GitHub

@sandersn is already working on this.

Since Apr 27, 2021.

Bug Domain: check: Type Inference Rescheduled
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Description

Bug Report

🔎 Search Terms

destructure array typescript union

🕗 Version & Regression Information

I used the playground to test different versions and it looks like this has always occured.

  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about "Type Systems behavior", "Type Guards", "Functions".
⏯ Playground Link

Playground link with relevant code

💻 Code
const t = [4,20] as const
const t2 = [4, 20, 30] as const
const t3 = [10, 10] as [number, number] | [number, number, number]

// Works
new Date().setHours(...t)
new Date().setHours(...t2)

// Error: Expected 1-4 arguments, but got 0 or more.
new Date().setHours(...t3)
🙁 Actual behavior

Error: Expected 1-4 arguments, but got 0 or more.

The array type passed as a length of 2 or 3 so the message "got 0 arguments" is wrong.

🙂 Expected behavior

I expect the compiler should be able to recognize that the array type can only have length 2 or 3 and would not throw an error.

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