[Webkit-unassigned] [Bug 247493] New: Order between initializing x and this.x in strict mode

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=247493

            Bug ID: 247493
           Summary: Order between initializing x and this.x in strict mode
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Mac (Apple Silicon)
                OS: macOS 12
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: p51lee at kaist.ac.kr

Created attachment 463411

  --> https://bugs.webkit.org/attachment.cgi?id=463411&action=review

I captured ECMAScript 2022 section 13.15.2.

// input.js
"use strict";
x = this.x = 0;
________________________________

Hello,

Executing the input.js using JSC terminates normally, but it is expected to throw ReferenceError.

According to ECMAScript 2022 section 13.15.2: Evaluation of `*AssignmentExpression* : *LeftHandSideExpression* = *AssignmentExpression*`,

(link: https://tc39.es/ecma262/2022/multipage/ecmascript-language-expressions.html#sec-assignment-operators-runtime-semantics-evaluation)

in line 1-a, *LeftHandSideExpression*, i.e. `x` should be evaluated first and the evaluation result is an unresolvable reference.

Therefore PutValue() in line 1-e throws ReferenceError because strict mode is turned on.


WebKit version: 615.1.10

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