microsoft / microsoft/TypeScript
Give `{}` some other type than `{}` so it doesn't cause subtype reduction problems with primitives
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Description
TypeScript Version: 3.9.0-beta
Search Terms:
Array
Code
let a = [{a:1},1,2,3] // OK, Expected (number | { a: number; })[]
let b = [{},1,2,3] // Error, Expected: `({}|1)[]` Actual: `{}[]`
Playground Link:
Related Issues:
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 TypeScript 3.9.0-beta Playground link and reproduce the two array-literal examples. Investigate how the type checker infers {} alongside primitive elements; done means the second example preserves the expected union type instead of reducing to {}[].
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