Bug 1864647 - Don't crash when finding nested relative selectors. r=d…

…shin

For now, do the same as pseudo-elements, which is effectively to keep
them in the replaced selector but don't match them. Avoid crashing in
this case.

I filed w3c/csswg-drafts#9600 since this issue
isn't specific about :has(), and depending on the result of that
discussion, the "proper" solution might be different.

Differential Revision: https://phabricator.services.mozilla.com/D193663

UltraBlame original commit: 69bede2c30ec37c0a9b3b44879e28a5dd1c0b1c5

servo/components/selectors/matching.rs

@@ -3465,6 +3465,170 @@ false
 }
 None
 }
+fn
+match_relative_selectors
+<
+E
+:
+Element
+>
+(
+selectors
+:
+&
+[
+RelativeSelector
+<
+E
+:
+:
+Impl
+>
+]
+element
+:
+&
+E
+context
+:
+&
+mut
+MatchingContext
+<
+E
+:
+:
+Impl
+>
+rightmost
+:
+Rightmost
+)
+-
+>
+bool
+{
+if
+context
+.
+relative_selector_anchor
+(
+)
+.
+is_some
+(
+)
+{
+/
+/
+FIXME
+(
+emilio
+)
+:
+This
+currently
+can
+happen
+with
+nesting
+and
+it
+'
+s
+not
+fully
+/
+/
+correct
+arguably
+.
+But
+the
+ideal
+solution
+isn
+'
+t
+super
+-
+clear
+either
+.
+For
+now
+/
+/
+cope
+with
+it
+and
+explicitly
+reject
+it
+at
+match
+time
+.
+See
+[
+1
+]
+for
+discussion
+.
+/
+/
+/
+/
+[
+1
+]
+:
+https
+:
+/
+/
+github
+.
+com
+/
+w3c
+/
+csswg
+-
+drafts
+/
+issues
+/
+9600
+return
+false
+;
+}
+context
+.
+nest_for_relative_selector
+(
+element
+.
+opaque
+(
+)
+|
+context
+|
+{
+do_match_relative_selectors
+(
+selectors
+element
+context
+rightmost
+)
+}
+)
+}
 /
 /
 /
@@ -3480,7 +3644,7 @@ relative
 selectors
 .
 fn
-matches_relative_selectors
+do_match_relative_selectors
 <
 E
 :
@@ -6806,30 +6970,17 @@ relative_selectors
 )
 =
 >
-context
-.
-shared
-.
-nest_for_relative_selector
-(
-element
-.
-opaque
-(
-)
-|
-context
-|
 {
-matches_relative_selectors
+match_relative_selectors
 (
 relative_selectors
 element
 context
+.
+shared
 rightmost
 )
 }
-)
 Component
 :
 :

servo/components/style/invalidation/element/invalidation_map.rs

@@ -7363,17 +7363,23 @@ Impl
 >
 bool
 {
-unreachable
-!
-(
-"
-Nested
+/
+/
+Ignore
+nested
 relative
-selector
-?
-"
-)
-;
+selectors
+.
+These
+can
+happen
+as
+a
+result
+of
+nesting
+.
+true
 }
 fn
 visit_simple_selector
@@ -8712,17 +8718,23 @@ Impl
 >
 bool
 {
-unreachable
-!
-(
-"
-Nested
+/
+/
+Ignore
+nested
 relative
-selector
-?
-"
-)
-;
+selectors
+.
+These
+can
+happen
+as
+a
+result
+of
+nesting
+.
+true
 }
 fn
 visit_simple_selector

testing/web-platform/tests/css/css-nesting/has-nesting-ref.html

@@ -0,0 +1,46 @@
+<
+!
+doctype
+html
+>
+<
+title
+>
+Nested
+has
+shouldn
+'
+t
+match
+<
+/
+title
+>
+<
+style
+>
+ul
+{
+background
+:
+green
+}
+<
+/
+style
+>
+<
+ul
+>
+<
+li
+>
+Bar
+<
+/
+li
+>
+<
+/
+ul
+>