style: Correct style sharing handling for any element that considered `:has()` in selector matching

For any element that anchors a `:has()` selector (i.e. Matches a selector that
contains a `:has()` on its rightmost side), we prevent style sharing altogether,
as evaluation of the `:has()` selector is required in the first place to
determine style sharing.

On the other hand, any element matching a rule containing `:has()` without
anchoring it can do style sharing for siblings, but not cousins.

Differential Revision: https://phabricator.services.mozilla.com/D176836

1 files changed, 3 insertions, 0 deletions

diff --git a/components/selectors/context.rs b/components/selectors/context.rs
index 8abfebbf78a..fc620baa08f 100644
--- a/components/selectors/context.rs
+++ b/components/selectors/context.rs
@@ -146,6 +146,7 @@ where
 
     /// The current element we're anchoring on for evaluating the relative selector.
     current_relative_selector_anchor: Option<OpaqueElement>,
+    pub considered_relative_selector: bool,
 
     quirks_mode: QuirksMode,
     needs_selector_flags: NeedsSelectorFlags,
@@ -199,6 +200,7 @@ where
             pseudo_element_matching_fn: None,
             extra_data: Default::default(),
             current_relative_selector_anchor: None,
+            considered_relative_selector: false,
             _impl: ::std::marker::PhantomData,
         }
     }
@@ -332,6 +334,7 @@ where
         self.current_relative_selector_anchor = Some(anchor);
         let result = self.nest(f);
         self.current_relative_selector_anchor = original_relative_selector_anchor;
+        self.considered_relative_selector = true;
         result
     }