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21d3294c 1--
2-- strict.lua
3-- checks uses of undeclared global variables
4-- All global variables must be 'declared' through a regular assignment
5-- (even assigning nil will do) in a main chunk before being used
6-- anywhere or assigned to inside a function.
7--
8
9local getinfo, error, rawset, rawget = debug.getinfo, error, rawset, rawget
10
11local mt = getmetatable(_G)
12if mt == nil then
13 mt = {}
14 setmetatable(_G, mt)
15end
16
17mt.__declared = {}
18
19local function what ()
20 local d = getinfo(3, "S")
21 return d and d.what or "C"
22end
23
24mt.__newindex = function (t, n, v)
25 if not mt.__declared[n] then
26 local w = what()
27 if w ~= "main" and w ~= "C" then
28 error("assign to undeclared variable '"..n.."'", 2)
29 end
30 mt.__declared[n] = true
31 end
32 rawset(t, n, v)
33end
34
35mt.__index = function (t, n)
36 if not mt.__declared[n] and what() ~= "C" then
37 error("variable '"..n.."' is not declared", 2)
38 end
39 return rawget(t, n)
40end
41