275055 2024-06-03 06:54:42 -0700 [Regression] Spread of class should not inherit instanceof 2024-06-04 14:10:01 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P1 Major --- 1 max ysuzuki ahmad.saleem792 lloisrrois webkit-bug-importer ysuzuki yurys oldest_to_newest 2039419 0 max 2024-06-03 06:54:42 -0700 RANGE: https://github.com/WebKit/WebKit/compare/cd9be0fded51cea4c2c3a7c9a21d6b4d341df09d...91f787886ac542eb4148d991b629c028f389f0cf Potential commit which broke it: https://github.com/WebKit/WebKit/commit/804d44f89619bfae3e5e2e21a07669b1fb320d57 Repro: ```ts class Test {field1 = 'foo';} const t1 = { ...new Test() }; console.log(t1 instanceof Test); ``` Expected: false Actual: true V8/Spidermonkey return false. Downstream issue: https://github.com/microsoft/playwright/issues/31132 2039422 1 max 2024-06-03 07:01:08 -0700 Was able to reproduce it in Safari Technology Preview - t1 is a class instance while in V8/Spidermonkey its just an object. 2039450 2 webkit-bug-importer 2024-06-03 09:21:39 -0700 <rdar://problem/129168077> 2039714 3 ysuzuki 2024-06-04 13:07:42 -0700 Pull request: https://github.com/WebKit/WebKit/pull/29511 2039726 4 ews-feeder 2024-06-04 14:09:59 -0700 Committed 279713@main (2069a352b203): <https://commits.webkit.org/279713@main> Reviewed commits have been landed. Closing PR #29511 and removing active labels.