`in` operator inside for statement destructuring

[Kanguk Lee]

// input.js
for ( var { x = 0 in [ 0 ] } of [ 0 ] );
_____________________

Hello,

Executing the input.js using JSC throws SyntaxError, but it is expected to terminate normally.

Running the input.js with JSC gives

---
$ jsc input.js
Exception: SyntaxError: Unexpected keyword 'in'. Expected either a closing '}' or an ',' after a property destructuring pattern.
at input.js:1
---

while other engines behave like

---
# V8
$ node input.js
// no error

# GraalJS
$ js input.js
// no error
---


WebKit version: 615.1.10

[Radar WebKit Bug Importer]

<rdar://problem/102065296>

[Yijia Huang]

Pull request: https://github.com/WebKit/WebKit/pull/6305

[EWS]

Committed 256497@main (598cda65c4a2): <https://commits.webkit.org/256497@main>

Reviewed commits have been landed. Closing PR #6305 and removing active labels.