microsoft / microsoft/TypeScript
"Infer types from usage" not consider js object initializer
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Experience Enhancement
Suggestion
- Dominant language
- Go
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- Merged PRs (30d)
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Description
TypeScript Version: Nightly
Search Terms: infer types from usage
Code
function foo(/*infer parameters from usage 'here'*/x) {
let obj1: { a: string } = { a: '' }
obj1.a = x;
let obj2: { a: boolean } = { a: true };
obj2.a = x;
bar({ a: x });
}
function bar(obj: { a: object }) {
}
Expected behavior:
foo become to foo(x: string|boolean|object)
Actual behavior:
foo become to foo(x: string|boolean)
Playground Link: Playground
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 compare the inferred type of foo with the expected signature. Trace how usage inference handles obj1.a = x, obj2.a = x, and bar({ a: x }); the fix is complete when the object-literal usage contributes object to the inferred union.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100