strict.lua

--
-- strict.lua
-- checks uses of undeclared global variables
-- All global variables must be 'declared' through a regular assignment
-- (even assigning nil will do) in a main chunk before being used
-- anywhere or assigned to inside a function.
--

local mt = getmetatable(_G)

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

__STRICT = true
mt.__declared = {}

mt.__newindex = function(t, n, v)
	if (__STRICT and not mt.__declared[n]) then
		local w = debug.getinfo(2, "S").what
		
		if (w ~= "main" and w ~= "C") then
			error("assign to undeclared variable '" .. n .. "'", 2)
		end
		
		mt.__declared[n] = true
	end
	
	rawset(t, n, v)
end

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

function global(...)
	for _, v in ipairs {...} do
		mt.__declared[v] = true
	end
end