Generate UnsupportedItem for function templates

PiperOrigin-RevId: 424329140
diff --git a/rs_bindings_from_cc/ast_visitor.cc b/rs_bindings_from_cc/ast_visitor.cc
index 86261fd..1f38d1e 100644
--- a/rs_bindings_from_cc/ast_visitor.cc
+++ b/rs_bindings_from_cc/ast_visitor.cc
@@ -197,6 +197,11 @@
 bool AstVisitor::VisitFunctionDecl(clang::FunctionDecl* function_decl) {
   if (!IsFromCurrentTarget(function_decl)) return true;
   if (function_decl->isDeleted()) return true;
+  if (function_decl->isTemplated()) {
+    PushUnsupportedItem(function_decl,
+                        "Function templates are not supported yet",
+                        function_decl->getBeginLoc());
+  }
 
   devtools_rust::LifetimeSymbolTable lifetime_symbol_table;
   llvm::Expected<devtools_rust::FunctionLifetimes> lifetimes =