microsoft / microsoft/TypeScript
Parse error when using `in` nested in a `for` initializer
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Nobody has claimed this yet.
Bug
Domain: Parser
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Description
🔎 Search Terms
in for in init syntax error
🕗 Version & Regression Information
- This is the behavior in every version I tried
⏯ Playground Link
https://www.typescriptlang.org/play/?ts=5.5.3#code/GYewTgBAFAbghpOEC8EDaAjCBLAdhAYwF0BuEgShKA
💻 Code
for (var a = [b in c];;);
🙁 Actual behavior
It says "',' expected." at the in
🙂 Expected behavior
It should parse it properly
Additional information about the issue
No response
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 by reproducing the parsing error with the TypeScript Playground link and the provided for initializer snippet. Trace how the parser handles for initializers containing in, then add a regression test and verify that the snippet parses without the reported error.
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
- 45/100