Bug 1685621b - Fix serialization of complex :not(). r=emilio, a=jcristau

Differential Revision: https://phabricator.services.mozilla.com/D101090

servo/components/selectors/parser.rs

@@ -1519,14 +1519,6 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
             AttributeOther(ref attr_selector) => attr_selector.to_css(dest),
 
             // Pseudo-classes
-            Negation(ref arg) => {
-                dest.write_str(":not(")?;
-                for component in arg.iter() {
-                    component.to_css(dest)?;
-                }
-                dest.write_str(")")
-            },
-
             FirstChild => dest.write_str(":first-child"),
             LastChild => dest.write_str(":last-child"),
             OnlyChild => dest.write_str(":only-child"),
@@ -1556,10 +1548,11 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
                 write_affine(dest, a, b)?;
                 dest.write_char(')')
             },
-            Is(ref list) | Where(ref list) => {
+            Is(ref list) | Where(ref list) | Negation(ref list) => {
                 match *self {
                     Where(..) => dest.write_str(":where(")?,
                     Is(..) => dest.write_str(":is(")?,
+                    Negation(..) => dest.write_str(":not(")?,
                     _ => unreachable!(),
                 }
                 serialize_selector_list(list.iter(), dest)?;

testing/web-platform/meta/css/selectors/parsing/parse-not.html.ini

-[parse-not.html]
-  [":not(span.a, div.b)" should be a valid selector]
-    expected: FAIL
-
-  [":not(.a .b ~ c, .d .e)" should be a valid selector]
-    expected: FAIL
-