[clang-tools-extra] [clangd] fix extract-to-function for overloaded operators (PR #81640)

[Nathan Ridge via cfe-commits]

================
@@ -104,9 +104,12 @@ bool isRootStmt(const Node *N) {
   // Root statement cannot be partially selected.
   if (N->Selected == SelectionTree::Partial)
     return false;
-  // Only DeclStmt can be an unselected RootStmt since VarDecls claim the entire
-  // selection range in selectionTree.
-  if (N->Selected == SelectionTree::Unselected && !N->ASTNode.get<DeclStmt>())
+  // A DeclStmt can be an unselected RootStmt since VarDecls claim the entire
+  // selection range in selectionTree. Additionally, a CXXOperatorCallExpr of a
+  // binary operation can be unselected because it's children claim the entire
+  // selection range in the selection tree (e.g. <<).
+  if (N->Selected == SelectionTree::Unselected && !N->ASTNode.get<DeclStmt>() &&
----------------
HighCommander4 wrote:

I guess the difference is that a `DeclStmt` can have a **single** `VarDecl` child which could be completely selected, leaving the `DeclStmt` unselected. There is no analogous situation for a `CXXOperatorCallExpr` which has multiple children.

https://github.com/llvm/llvm-project/pull/81640