microsoft / microsoft/TypeScript
Omitting a property from tuple breaks destruction
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Nobody has claimed this yet.
Bug
Domain: Mapped Types
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Description
Bug Report
🔎 Search Terms
tuple omit property
Searched in Bing and Github issues but I found nothing
🕗 Version & Regression Information
- This is the behavior in every version I tried
⏯ Playground Link
💻 Code
const foo = [1, "2"] as const
const [a, b] = foo // everything works well, a is number and b is string
const bar = [1, "2"] as Omit<[number, string], "at">
const [c, d] = bar // Oops! c and d are string | number now
🙁 Actual behavior
↑
c and d are both string | number
🙂 Expected behavior
a and b should have correct type
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the linked TypeScript Playground reproduction and inspect how the tuple type produced by Omit<[number, string], "at"> is handled during array destructuring. The fix is complete when destructuring that value infers c as number and d as string, matching the expected behavior shown in the issue.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100