microsoft / microsoft/TypeScript
Allow type aliases to reference themselves in type argument positions
Nobody has claimed this yet.
- Dominant language
- Go
- Stars
- 111k
- Forks
- 14.3k
- Avg merge
- 2d 4h
- Merged PRs (30d)
- 132
Description
TypeScript Version: 3.8.0-dev.20191105
Search Terms:
circular
Code
type A<T> = { x: T }
type R = A<R> // FAIL
type B = { x: B } // OK
Expected behavior:
Both cases throw no error.
Actual behavior:
Type R is rejected due to a circular reference.
Playground Link:
Link
Related Issues:
https://github.com/microsoft/TypeScript/pull/33050
Regression: https://github.com/microsoft/TypeScript/pull/33050#issuecomment-526637037
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
Reproduce the behavior in the linked TypeScript Playground using the A, R, and B aliases, then compare the reported circular-reference diagnostics with the expected behavior. Done means the type alias R is accepted in the same way as the directly recursive type B, without introducing errors for the existing cases.
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
- Clearly specified
- Newbie friendliness
- 28/100