195556 2019-03-11 07:59:15 -0700 Unable to extend the DocumentFragment class 2020-04-17 14:45:14 -0700 1 1 1 Unclassified WebKit DOM Safari Technology Preview Mac macOS 10.14 RESOLVED CONFIGURATION CHANGED https://bugs.webkit.org/show_bug.cgi?id=174313 P2 Normal --- 1 andrea.giammarchi webkit-unassigned ashvayka oldest_to_newest 1514766 0 andrea.giammarchi 2019-03-11 07:59:15 -0700 The following code will fail the assertion that would, otherwise, pass in every other browser that implements classes. (function () {'use strict'; class WaitWhat extends DocumentFragment {} console.assert( (new WaitWhat) instanceof WaitWhat, `any instance of a DocumentFragment extend fails` ); }()); This is true even through Reflect.construct (function () {'use strict'; class WaitWhat extends DocumentFragment {} console.assert( Reflect.construct(DocumentFragment, [], WaitWhat) instanceof WaitWhat, `any instance of a DocumentFragment extend fails` ); }()); The expected behavior is that it is possible to extend the DocumentFragment as any other built-in class. 1642852 1 ashvayka 2020-04-17 14:45:14 -0700 As of r256716, extending DocumentFragment (as well as other DOM constructors) works as expected.