重载基础工具

function overloaded()
    local fns = {}
    local mt = {}
    
    local function oerror()
        return error("Invalid argument types to overloaded function")
    end
    
    function mt:__call(...)
        local argv = {...}
        local default = self.default
        
        local signature = {}
        for i,arg in ipairs {...} do
            signature[i] = type(arg)
        end
        
        signature = table.concat(signature, ",")
        
        return (fns[signature] or self.default)(...)
    end
    
    function mt:__index(key)
        local signature = {}
        local function __newindex(self, key, value)
            print(key, type(key), value, type(value))
            signature[#signature+1] = key
            fns[table.concat(signature, ",")] = value
            print("bind", table.concat(signature, ", "))
        end
        local function __index(self, key)
            print("I", key, type(key))
            signature[#signature+1] = key
            return setmetatable({}, { __index = __index, __newindex = __newindex })
        end
        return __index(self, key)
    end
    
    function mt:__newindex(key, value)
        fns[key] = value
    end
    
    return setmetatable({ default = oerror }, mt)
end