202485 2019-10-02 11:17:40 -0700 typeof (function that masquerades as undefined) is "function", should be "undefined" 2020-12-03 09:46:19 -0800 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED DUPLICATE 215572 P2 Normal --- 1 ggaren webkit-unassigned adf ap ashvayka fpizlo saam ysuzuki oldest_to_newest 1576070 0 ggaren 2019-10-02 11:17:40 -0700 See https://bugs.webkit.org/show_bug.cgi?id=198805. The openDatabase function is allocated by calling JSFunction::createFunctionThatMasqueradesAsUndefined. 1576071 1 380040 ggaren 2019-10-02 11:19:35 -0700 Created attachment 380040 test case 1577081 2 ap 2019-10-04 17:07:39 -0700 The test case produces PASS for me in Safari 13.0.1. PASS: typeof window.openDatabase is undefined 1579031 3 adf 2019-10-11 01:47:31 -0700 I believe the issue is that (were these both tests) PASS: typeof window.openDatabase is undefined PASS: typeof window.openDatabase is function Both can't be true. Specifically window.openDatabase == "function" is true window.openDatabase == "undefined" is also true http://locutus.sorcerer.co.uk/demo/safari-openDatabase.html 1711701 4 ashvayka 2020-12-03 09:46:19 -0800 (In reply to Oz from comment #3) > PASS: typeof window.openDatabase is undefined > PASS: typeof window.openDatabase is function > > Both can't be true. Nicely noted, thank you. That discrepancy was made possible due to peephole optimization in BytecodeGenerator::emitEqualityOpImpl(), which detects patterns like `typeof X === "Y"` and emits different bytecodes depending on Y. r265907 fixed the `typeof X === "function"` bytecode op to return `false` for masquerader (aka [[IsHTMLDDA]]) objects. test262 coverage was added in https://github.com/tc39/test262/pull/2706. *** This bug has been marked as a duplicate of bug 215572 *** 380040 2019-10-02 11:19:35 -0700 2019-10-02 11:19:35 -0700 test case scratch.html text/html 313 ggaren PHByZSBpZD0iY29uc29sZSI+PC9wcmU+Cgo8c2NyaXB0PgpsZXQgbG9nID0gZnVuY3Rpb24ocykK ewoJZG9jdW1lbnQuZ2V0RWxlbWVudEJ5SWQoImNvbnNvbGUiKS5hcHBlbmRDaGlsZChkb2N1bWVu dC5jcmVhdGVUZXh0Tm9kZShzICsgIlxuIikpOwp9OwoKbGV0IHJlc3VsdCA9IHR5cGVvZiB3aW5k b3cub3BlbkRhdGFiYXNlOwpsZXQgcHJlZml4ID0gcmVzdWx0ID09ICJ1bmRlZmluZWQiID8gIlBB U1M6ICIgOiAiRkFJTDogIgoKbG9nKHByZWZpeCArICJ0eXBlb2Ygd2luZG93Lm9wZW5EYXRhYmFz ZSBpcyAiICsgcmVzdWx0KTsKPC9zY3JpcHQ+Cg==