Slightly more robust.

code_obj.lua

@@ -355,7 +355,7 @@ do
           local _list_1 = self.bits
           for _index_0 = 1, #_list_1 do
             local bit = _list_1[_index_0]
-            if bit.__class == LuaCode then
+            if not (type(bit) == 'string') then
               gather_from(bit)
             end
           end

code_obj.moon

@@ -207,7 +207,7 @@ class LuaCode extends Code
                         seen[var] = true
                         to_declare[#to_declare+1] = var
                 for bit in *@bits
-                    if bit.__class == LuaCode
+                    unless type(bit) == 'string'
                         gather_from bit
             gather_from self
         if #to_declare > 0