LibWeb: Add fast_is<T> helpers for Navigable & TraversableNavigable

Author: https://github.com/awesomekling
Commit: https://github.com/LadybirdBrowser/ladybird/commit/0e490e33522
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4395

Libraries/LibWeb/HTML/Navigable.cpp

@@ -99,11 +99,6 @@ Vector<GC::Root<Navigable>> Navigable::child_navigables() const
     return results;
 }
 
-bool Navigable::is_traversable() const
-{
-    return is<TraversableNavigable>(*this);
-}
-
 bool Navigable::is_ancestor_of(GC::Ref<Navigable> other) const
 {
     for (auto ancestor = other->parent(); ancestor; ancestor = ancestor->parent()) {

Libraries/LibWeb/HTML/Navigable.h

@@ -52,7 +52,7 @@ public:
 
     Vector<GC::Root<Navigable>> child_navigables() const;
 
-    bool is_traversable() const;
+    virtual bool is_traversable() const { return false; }
 
     String const& id() const { return m_id; }
     GC::Ptr<Navigable> parent() const { return m_parent; }
@@ -188,6 +188,9 @@ public:
 
     bool has_pending_navigations() const { return !m_pending_navigations.is_empty(); }
 
+    template<typename T>
+    bool fast_is() const = delete;
+
 protected:
     explicit Navigable(GC::Ref<Page>);
 

Libraries/LibWeb/HTML/TraversableNavigable.h

@@ -120,6 +120,8 @@ public:
 private:
     TraversableNavigable(GC::Ref<Page>);
 
+    virtual bool is_traversable() const override { return true; }
+
     virtual void visit_edges(Cell::Visitor&) override;
 
     // FIXME: Fix spec typo cancelation --> cancellation
@@ -175,4 +177,7 @@ struct BrowsingContextAndDocument {
 WebIDL::ExceptionOr<BrowsingContextAndDocument> create_a_new_top_level_browsing_context_and_document(GC::Ref<Page> page);
 void finalize_a_same_document_navigation(GC::Ref<TraversableNavigable> traversable, GC::Ref<Navigable> target_navigable, GC::Ref<SessionHistoryEntry> target_entry, GC::Ptr<SessionHistoryEntry> entry_to_replace, HistoryHandlingBehavior, UserNavigationInvolvement);
 
+template<>
+inline bool Navigable::fast_is<TraversableNavigable>() const { return is_traversable(); }
+
 }