LibJS+LibWeb: Remove NonnullGCPtr<T>::operator=(GCPtr<T>) footgun

GCPtr can be null so it's not safe to assign it to a NonnullGCPtr unless
you know it to be non-null.

This exposed a number of wrong uses in LibWeb which had to be fixed as
part of this change.

Userland/Libraries/LibJS/Heap/GCPtr.h

@@ -49,13 +49,6 @@ public:
     {
     }
 
-    NonnullGCPtr& operator=(GCPtr<T> const& other)
-    {
-        m_ptr = const_cast<T*>(other.ptr());
-        VERIFY(m_ptr);
-        return *this;
-    }
-
     NonnullGCPtr& operator=(T const& other)
     {
         m_ptr = &const_cast<T&>(other);

Userland/Libraries/LibWeb/DOM/EventDispatcher.cpp

@@ -285,7 +285,7 @@ bool EventDispatcher::dispatch(JS::NonnullGCPtr<EventTarget> target, Event& even
             }
             // 8. Otherwise, set target to parent and then:
             else {
-                target = parent;
+                target = *parent;
 
                 // 1. If isActivationEvent is true, activationTarget is null, and target has activation behavior, then set activationTarget to target.
                 if (is_activation_event && !activation_target && target->activation_behavior)

Userland/Libraries/LibWeb/DOM/NodeIterator.cpp

@@ -84,7 +84,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> NodeIterator::traverse(Direction directio
                 auto* next_node = m_traversal_pointer->node->next_in_pre_order(m_root.ptr());
                 if (!next_node)
                     return nullptr;
-                m_traversal_pointer->node = next_node;
+                m_traversal_pointer->node = *next_node;
             } else {
                 // If beforeNode is true, then set it to false.
                 m_traversal_pointer->is_before_node = false;
@@ -99,7 +99,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> NodeIterator::traverse(Direction directio
                 auto* previous_node = m_traversal_pointer->node->previous_in_pre_order();
                 if (!previous_node)
                     return nullptr;
-                m_traversal_pointer->node = previous_node;
+                m_traversal_pointer->node = *previous_node;
             } else {
                 // If beforeNode is false, then set it to true.
                 m_traversal_pointer->is_before_node = true;
@@ -194,7 +194,7 @@ void NodeIterator::run_pre_removing_steps_with_node_pointer(Node& to_be_removed_
             while (node && node->is_descendant_of(to_be_removed_node))
                 node = node->next_in_pre_order(root());
             if (node)
-                pointer.node = node;
+                pointer.node = *node;
             return;
         }
         if (auto* node = to_be_removed_node.previous_in_pre_order()) {
@@ -218,7 +218,7 @@ void NodeIterator::run_pre_removing_steps_with_node_pointer(Node& to_be_removed_
                 node = node->previous_in_pre_order();
         }
         if (node)
-            pointer.node = node;
+            pointer.node = *node;
         return;
     }
     auto* node = to_be_removed_node.next_in_pre_order(root());
@@ -227,7 +227,7 @@ void NodeIterator::run_pre_removing_steps_with_node_pointer(Node& to_be_removed_
             node = node->previous_in_pre_order();
     }
     if (node)
-        pointer.node = node;
+        pointer.node = *node;
 }
 
 // https://dom.spec.whatwg.org/#nodeiterator-pre-removing-steps

Userland/Libraries/LibWeb/DOM/Range.cpp

@@ -116,7 +116,7 @@ RelativeBoundaryPointPosition position_of_boundary_point_relative_to_other_bound
         while (!node_a.is_parent_of(child)) {
             auto* parent = child->parent();
             VERIFY(parent);
-            child = parent;
+            child = *parent;
         }
 
         // 3. If child’s index is less than offsetA, then return after.
@@ -147,12 +147,12 @@ WebIDL::ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartO
 
         // 1. If range’s root is not equal to node’s root, or if bp is after the range’s end, set range’s end to bp.
         if (&root() != &node.root() || position_of_boundary_point_relative_to_other_boundary_point(node, offset, m_end_container, m_end_offset) == RelativeBoundaryPointPosition::After) {
-            m_end_container = &node;
+            m_end_container = node;
             m_end_offset = offset;
         }
 
         // 2. Set range’s start to bp.
-        m_start_container = &node;
+        m_start_container = node;
         m_start_offset = offset;
     } else {
         // -> If these steps were invoked as "set the end"
@@ -160,12 +160,12 @@ WebIDL::ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartO
 
         // 1. If range’s root is not equal to node’s root, or if bp is before the range’s start, set range’s start to bp.
         if (&root() != &node.root() || position_of_boundary_point_relative_to_other_boundary_point(node, offset, m_start_container, m_start_offset) == RelativeBoundaryPointPosition::Before) {
-            m_start_container = &node;
+            m_start_container = node;
             m_start_offset = offset;
         }
 
         // 2. Set range’s end to bp.
-        m_end_container = &node;
+        m_end_container = node;
         m_end_offset = offset;
     }
 
@@ -342,11 +342,11 @@ WebIDL::ExceptionOr<void> Range::select(Node& node)
     auto index = node.index();
 
     // 4. Set range’s start to boundary point (parent, index).
-    m_start_container = parent;
+    m_start_container = *parent;
     m_start_offset = index;
 
     // 5. Set range’s end to boundary point (parent, index plus 1).
-    m_end_container = parent;
+    m_end_container = *parent;
     m_end_offset = index + 1;
 
     return {};
@@ -384,11 +384,11 @@ WebIDL::ExceptionOr<void> Range::select_node_contents(Node const& node)
     auto length = node.length();
 
     // 3. Set start to the boundary point (node, 0).
-    m_start_container = &node;
+    m_start_container = node;
     m_start_offset = 0;
 
     // 4. Set end to the boundary point (node, length).
-    m_end_container = &node;
+    m_end_container = node;
     m_end_offset = length;
 
     return {};
@@ -428,7 +428,7 @@ JS::NonnullGCPtr<Node> Range::common_ancestor_container() const
     // 2. While container is not an inclusive ancestor of end node, let container be container’s parent.
     while (!container->is_inclusive_ancestor_of(m_end_container)) {
         VERIFY(container->parent());
-        container = container->parent();
+        container = *container->parent();
     }
 
     // 3. Return container.
@@ -593,7 +593,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::extract()
 
     // 6. While common ancestor is not an inclusive ancestor of original end node, set common ancestor to its own parent.
     while (!common_ancestor->is_inclusive_ancestor_of(original_end_node))
-        common_ancestor = common_ancestor->parent_node();
+        common_ancestor = *common_ancestor->parent_node();
 
     // 7. Let first partially contained child be null.
     JS::GCPtr<Node> first_partially_contained_child;
@@ -919,7 +919,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_the_content
 
     // 6. While common ancestor is not an inclusive ancestor of original end node, set common ancestor to its own parent.
     while (!common_ancestor->is_inclusive_ancestor_of(original_end_node))
-        common_ancestor = common_ancestor->parent_node();
+        common_ancestor = *common_ancestor->parent_node();
 
     // 7. Let first partially contained child be null.
     JS::GCPtr<Node> first_partially_contained_child;
@@ -1078,7 +1078,7 @@ WebIDL::ExceptionOr<void> Range::delete_contents()
 
         // 2. While reference node’s parent is not null and is not an inclusive ancestor of original end node, set reference node to its parent.
         while (reference_node->parent_node() && !reference_node->parent_node()->is_inclusive_ancestor_of(original_end_node))
-            reference_node = reference_node->parent_node();
+            reference_node = *reference_node->parent_node();
 
         // 3. Set new node to the parent of reference node, and new offset to one plus the index of reference node.
         new_node = reference_node->parent_node();

Userland/Libraries/LibWeb/DOM/TreeWalker.cpp

@@ -57,7 +57,7 @@ JS::NonnullGCPtr<Node> TreeWalker::current_node() const
 // https://dom.spec.whatwg.org/#dom-treewalker-currentnode
 void TreeWalker::set_current_node(Node& node)
 {
-    m_current = &node;
+    m_current = node;
 }
 
 // https://dom.spec.whatwg.org/#dom-treewalker-parentnode
@@ -76,7 +76,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::parent_node()
         if (node) {
             auto result = TRY(filter(*node));
             if (result == NodeFilter::FILTER_ACCEPT) {
-                m_current = node;
+                m_current = *node;
                 return node;
             }
         }
@@ -113,7 +113,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::next_sibling()
 JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::previous_node()
 {
     // 1. Let node be this’s current.
-    JS::GCPtr<Node> node = m_current;
+    JS::NonnullGCPtr<Node> node = m_current;
 
     // 2. While node is not this’s root:
     while (node != m_root) {
@@ -123,7 +123,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::previous_node()
         // 2. While sibling is non-null:
         while (sibling) {
             // 1. Set node to sibling.
-            node = sibling;
+            node = *sibling;
 
             // 2. Let result be the result of filtering node within this.
             auto result = TRY(filter(*node));
@@ -131,7 +131,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::previous_node()
             // 3. While result is not FILTER_REJECT and node has a child:
             while (result != NodeFilter::FILTER_REJECT && node->has_children()) {
                 // 1. Set node to node’s last child.
-                node = node->last_child();
+                node = *node->last_child();
 
                 // 2. Set result to the result of filtering node within this.
                 result = TRY(filter(*node));
@@ -152,7 +152,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::previous_node()
             return nullptr;
 
         // 4. Set node to node’s parent.
-        node = node->parent();
+        node = *node->parent();
 
         // 5. If the return value of filtering node within this is FILTER_ACCEPT, then set this’s current to node and return node.
         if (TRY(filter(*node)) == NodeFilter::FILTER_ACCEPT) {
@@ -168,7 +168,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::previous_node()
 JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::next_node()
 {
     // 1. Let node be this’s current.
-    JS::GCPtr<Node> node = m_current;
+    JS::NonnullGCPtr<Node> node = m_current;
 
     // 2. Let result be FILTER_ACCEPT.
     auto result = NodeFilter::FILTER_ACCEPT;
@@ -178,14 +178,14 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::next_node()
         // 1. While result is not FILTER_REJECT and node has a child:
         while (result != NodeFilter::FILTER_REJECT && node->has_children()) {
             // 1. Set node to its first child.
-            node = node->first_child();
+            node = *node->first_child();
 
             // 2. Set result to the result of filtering node within this.
             auto result = TRY(filter(*node));
 
             // 3. If result is FILTER_ACCEPT, then set this’s current to node and return node.
             if (result == NodeFilter::FILTER_ACCEPT) {
-                m_current = node;
+                m_current = *node;
                 return node;
             }
         }
@@ -207,7 +207,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::next_node()
 
             // 3. If sibling is non-null, then set node to sibling and break.
             if (sibling) {
-                node = sibling;
+                node = *sibling;
                 break;
             }
 
@@ -220,7 +220,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::next_node()
 
         // 6. If result is FILTER_ACCEPT, then set this’s current to node and return node.
         if (result == NodeFilter::FILTER_ACCEPT) {
-            m_current = node;
+            m_current = *node;
             return node;
         }
     }
@@ -279,7 +279,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::traverse_children(ChildTraver
 
         // 2. If result is FILTER_ACCEPT, then set walker’s current to node and return node.
         if (result == NodeFilter::FILTER_ACCEPT) {
-            m_current = node;
+            m_current = *node;
             return node;
         }
 
@@ -347,7 +347,7 @@ JS::ThrowCompletionOr<JS::GCPtr<Node>> TreeWalker::traverse_siblings(SiblingTrav
 
             // 3. If result is FILTER_ACCEPT, then set walker’s current to node and return node.
             if (result == NodeFilter::FILTER_ACCEPT) {
-                m_current = node;
+                m_current = *node;
                 return node;
             }