--
-- fascist.lua, like strict.lua but even more so.
-- checks uses of uninitialized global variables
-- All global variables must be not only declared but actually initialized
-- in a main chunk by e.g. `global{a=1,b=2} before being used anywhere
-- or assigned to inside a function.
--
-- Dirk Laurie, 2012
--

local getinfo, error, rawset, rawget = debug.getinfo, error, rawset, rawget

local mt = getmetatable(_G)
if mt == nil then
  mt = {}
  setmetatable(_G, mt)
end

mt.__declared = {}

local function what ()
  local d = getinfo(3, "S")
  return d and d.what or "C"
end

mt.__newindex = function (t, n, v)
  if not mt.__declared[n] and what() ~= "C" then
      error("assign to undeclared variable '"..n.."'", 2)
    end
  rawset(t, n, v)
end

mt.__index = function (t, n)
  if not mt.__declared[n] and what() ~= "C" then
    error("variable '"..n.."' is not declared", 2)
  end
  return rawget(t, n)
end

local function global(t)
   for k,v in pairs(t) do
      if mt.__declared[k] then error(
         "variable '"..n.."' is already declared", 2)
      end
      mt.__declared[k] = true; rawset(_G,k,v)
   end
end

local function liberate()
   mt.__index=nil; mt.__newindex=nil
end

rawset(_G,"global",global)
rawset(_G,"liberate",liberate)