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[TS] Support field assignments that change the runtime value sort

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評估

難度
4/5
預估耗時
3-5 天
新手友好度
48/100
Issue 類型
功能
描述清晰度
基本清楚
活躍度
活躍
技術堆疊
kotlin, typescript
領域
compilers, testing

研究方向

Start with the unsupported path reported by PR #466 and the related context in issue #465, using the minimal TypeScript example as the reproducer. Add the focused symbolic tests described in the acceptance criteria, including the alias case, and replay generated concrete cases in Node.js; done means both branches have no unsupported paths and existing typed field operations remain correct.

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描述

Current state (2026-10-14)

Audited against usvm main at 19866c959d.

Structural symbolic object fields can change runtime kind after #458. For concretely allocated declared class fields, WriteField still rejects incompatible value sorts; the method-reference audit also reproduced this boundary.

Remaining acceptance boundary

Represent the current allocated-field value independently of its declared sort and preserve replacement/alias reads. Re-run both Numeric/Text constructor branches with no unsupported path and native replay; preserve the existing explicit boundary until implemented.

Original report and acceptance context, retained for traceability

Problem

TypeScript permits assigning a value whose JavaScript type differs from a field's declared type when the receiver has a union type. The symbolic executor stores fields in separate regions by value sort. After selecting a concrete runtime class, a write of another sort cannot be represented by that class's declared field region. USVM #465 / PR #466 now reports that path as unsupported; it still needs a sound model.

Minimal TypeScript example

class Numeric {
  value: number = 1;
  numericOnly: boolean = true;
}

class Text {
  value: string = "initial";
  textOnly: boolean = true;
}

export function check(useNumeric: boolean): boolean {
  const object = new (useNumeric ? Numeric : Text)();
  object.value = "changed";
  return object.value === "changed";
}

TypeScript accepts this code, and Node.js returns true for both check(true) and check(false). With PR #466, the Text branch is modeled and the Numeric branch is explicitly reported in unsupportedPaths because assigning a string changes the field's runtime value sort.

Expected support

Model the current value of an object field independently of its declared TypeScript type. A write that changes the JavaScript value type must replace the previous value; subsequent reads, including through aliases, must observe the new type and value. Branches that cannot yet be modeled should remain explicitly unsupported rather than produce a stale field value.

Acceptance criteria

  • A focused symbolic test covers both branches with no unsupported paths and checks that both return true.
  • The generated concrete cases replay in Node.js.
  • A second test reads the changed field through an alias and confirms that the original field value is no longer visible.
  • Existing typed numeric, Boolean, reference, and any field operations remain correct.

Related: #465 and PR #466. This task concerns value type changes after assignment, not constructor selection.

主要語言
Kotlin
星號
33
分支
27
平均合併
4 天 1 小時
30 天內合併 PR
84

環境準備

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從這裡開始

  1. 先讀完整個 Issue，再讀專案的貢獻指南。
  2. 在 Issue 下留言說明你要接手 —— 這能避免兩個人做同樣的事。
  3. Fork 儲存庫，在一個分支上完成修改。
  4. 送出 Pull Request，並在描述裡引用這個 Issue 編號。

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