Support "in" operation on objects that have been weakly updated

Description

let b = __abstract("boolean", "NativeEnvironment.someBooleanProperty");
let ob1 = {  };
let ob2 = {  };
let ob3 = b ? ob1 : ob2;
ob3.bar = 777;
console.log("bar" in ob1);

Contributor guide

Tech stack

javascript

Domain

backend

Issue type

feature

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.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

mostly clear

Prerequisites

understanding of abstract interpretationfamiliarity with prepack's object model

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

30

Research direction

The issue requires adding support for the 'in' operator on weakly updated objects in Prepack's abstract interpreter. Look at how other operators like property access or deletion are handled in the abstract semantics, likely in files like `src/abstract operations.js` or similar. Investigate the handling of `WeakMap` or weak updates. The 'in' operator should check abstract property existence. Review existing tests for abstract object operations.