Bug 241847

Created attachment 460411 [details] Reproduction Example The `@supports selector ()` fails for shadow DOM pseudo element tests. An example for supported shadow DOM pseudo element styling is `input::placeholder { color: orchid }`. Therefore the expected behaviour would be that `@supports selector(input::placeholder) {` matches. Furthermore the expected behaviour would also be that `@supports not selector(input::placeholder) {` does NOT match. Instead the current behaviour is that `@supports selector(input::placeholder) {` does NOT match. In addition the current behaviour is also that `@supports not selector(input::placeholder) {` does match. This behaviour can be reproduced on different Safari versions: - iOS 15.5 Safari - MacOS Safari Version 15.5 (17613.2.7.1.8) - MacOS Safari Technology Preview Release 146 (Safari 15.4, WebKit 17614.1.14.10.6) Current Firefox and Chrome versions behave correctly. Please see the attached reproduction example.