dangerous_table_mutation.lua

local function dangerous_mutate_table(t, f)
  for i, v in ipairs(t) do t[i] = f(v, i) end
end

parent = {}
parent[1] = {}
dangerous_mutate_table(parent, function(v)
    v.prop = "asdf"
    -- oops, the programmer forgot to return anything here
end)

parent -- is now an empty table