const TreeScope* TreeScope::commonAncestorTreeScope(const TreeScope& other) const
{
WillBeHeapVector<RawPtrWillBeMember<const TreeScope>, 16> thisChain;
for (const TreeScope* tree = this; tree; tree = tree->parentTreeScope())
thisChain.append(tree);
WillBeHeapVector<RawPtrWillBeMember<const TreeScope>, 16> otherChain;
for (const TreeScope* tree = &other; tree; tree = tree->parentTreeScope())
otherChain.append(tree);
// Keep popping out the last elements of these chains until a mismatched pair is found. If |this| and |other|
// belong to different documents, null will be returned.
const TreeScope* lastAncestor = nullptr;
while (!thisChain.isEmpty() && !otherChain.isEmpty() && thisChain.last() == otherChain.last()) {
lastAncestor = thisChain.last();
thisChain.removeLast();
otherChain.removeLast();
}
return lastAncestor;
}
