lua - How to use __index as a function? -

i'm trying imitate:

b = {1,2,3} = setmetatable({1,nil,3},{__index = b}) print(a[2]) -- prints 2 

with that:

b = {1,2,3} = setmetatable({1,nil,3},{__index = function(t,k) rawget(b,k) end}) print(a[2]) -- nil 

what did wrong?

you need return value in metamethod:

return rawget(b,k)