microsoft / microsoft/TypeScript
Expected token errors should display all expected tokens, not just the first
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Description
🕗 Version & Regression Information
Pretty sure this has been the behaviour since the rewrite.
⏯ Playground Link
Playground link with relevant code
💻 Code
function a0([a, b, [[c]]]: [number, number, string[][]]) { }
a0([1, 2, [["world"]]);
🙁 Actual behavior
On the last ), "Expected ','."
🙂 Expected behavior
On the last ), "Expected ',' or ']'."
Right now the parser only shows the first error that starts at each location. This is an OK approach, especially when parsing has gone badly wrong, but often the parser will expect multiple tokens. The parser should report all the tokens in one error that were previously issued as multiple Expected_0 errors.
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 trace parser handling for Expected_0 diagnostics at the final closing parenthesis. The change is done when the same example reports the expected comma and closing bracket together rather than only the first token.
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