stop printing if the enum is empty

Author: WANGJIEKE

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -396,6 +396,11 @@ class DeclAndTypePrinter::Implementation
       auto elementTagMapping =
           owningPrinter.interopContext.getIrABIDetails().getEnumTagMapping(ED);
 
+      if (elementTagMapping.empty()) {
+        os << "\n";
+        return;
+      }
+
       os << "  enum class cases {\n";
       for (const auto &pair : elementTagMapping) {
         os << "    ";
@@ -404,11 +409,6 @@ class DeclAndTypePrinter::Implementation
       }
       os << "  };\n"; // enum class cases' closing bracket
 
-      if (elementTagMapping.empty()) {
-        os << "\n";
-        return;
-      }
-
       // Printing operator cases()
       os << "  inline operator cases() const {\n";
       os << "    switch (_getEnumTag()) {\n";