Use gather all fields when setting up the return of an opaque method

This can be considered an input to the function under test, so therefore
we need to set it up in the same way.

Author: thk123

jbmc/src/java_bytecode/java_bytecode_language.cpp

@@ -1039,25 +1039,13 @@ bool java_bytecode_languaget::convert_single_method(
     return false;
   }
 
-  const auto type_adder =  [&needed_lazy_methods](const typet &type) {
-    const pointer_typet *return_type_pointer =
-      type_try_dynamic_cast<pointer_typet>(type);
-    if(return_type_pointer)
-    {
-      const symbol_typet *symbol_type =
-        type_try_dynamic_cast<symbol_typet>(return_type_pointer->subtype());
-      if(symbol_type)
-      {
-        needed_lazy_methods->add_needed_class(symbol_type->get_identifier());
-      }
-    }
-  };
-
-  // opaque method, but we should load the classes of the parameters and return??
-  const code_typet function_type =to_code_type(symbol.type);
-  type_adder(function_type.return_type());
-  for(const code_typet::parametert &parameter : function_type.parameters())
-    type_adder(parameter.type());
+  const code_typet function_type = to_code_type(symbol.type);
+  if(
+    const pointer_typet *pointer_return_type =
+      type_try_dynamic_cast<pointer_typet>(function_type.return_type()))
+  {
+    needed_lazy_methods->add_all_needed_classes(*pointer_return_type);
+  }
 
   return true;
 }