Error: ThreadError(BadCall(TypeError { expected: "function", found: "nil" })

[zaoqi]

[zaoqi@zaoqi-pc lua]$ lua -i lang.lua 
Lua 5.3.5  Copyright (C) 1994-2018 Lua.org, PUC-Rio
> 
[zaoqi@zaoqi-pc lua]$ ............../luster/target/debug/luster -r lang.lua
Error: ThreadError(BadCall(TypeError { expected: "function", found: "nil" }))

https://gitlab.com/the-language/the-language/blob/d13341505075cb8cc4fa9b23212fd9c9932bc556/core/pure/lua/lang.lua