Microsoft/TypeScript

JS | Optional chaining left hand assignment not detected as syntax error.

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#57,640 opened on Mar 4, 2024

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BugDomain: ParserHelp Wanted

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Description

Does this issue occur when all extensions are disabled?: Yes/No

  • VS Code Version: 1.86.2
  • OS Version: Windows 11

Steps to Reproduce:

  1. Add this code to a .js file:
let tree = {type: 'none'};
tree?.type = 'apple';
  1. This should be detected as a syntax error. Specifically "Uncaught SyntaxError: Invalid left-hand side in assignment". It is not.

Contributor guide

Research direction
Find the code in the TypeScript parser that checks for invalid left hand side in assignment expressions. Look at the AST node for optional chaining expressions and trace how they are validated during parsing. Use the test suite to add a test case for this scenario.
Tech stack
typescriptjavascript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65