Unexpected error

I'm trying to run some pretty basic code, and am getting an unexpected and confusing error. I'm hoping that more experienced eyes can tell me what's wrong. This is standard code that was previously published, which I have not modified in any way. I am running the latest version of Lua.

Here is the error:
C:\>lua listtest.lua
lua: listtest.lua:46: attempt to call method 'pushright' (a nil value)
stack traceback:
listtest.lua:46: in function 'test'
listtest.lua:72: in main chunk
[C]: ?

C:\>

Here is the code:

-- $Id: lists.lua,v 1.6 2001年01月13日 22:04:18 doug Exp $
-- http://www.bagley.org/~doug/shootout/ 
-- implemented by: Roberto Ierusalimschy
--------------------------------------------------------------
-- List module
-- defines a prototipe for lists
--------------------------------------------------------------
List = {first = 0, last = -1}
function List:new ()
 local n = {}
 for k,v in self do n[k] = v end
 return n
end
function List:length ()
 return self.last - self.first + 1
end
function List:pushleft (value)
 local first = self.first - 1
 self.first = first
 self[first] = value
end
function List:pushright (value)
 local last = self.last + 1
 self.last = last
 self[last] = value
end
function List:popleft ()
 local first = self.first
 if first > self.last then error"list is empty" end
 local value = self[first]
 self[first] = nil -- to allow collection
 self.first = first+1
 return value
end
function List:popright ()
 local last = self.last
 if self.first > last then error"list is empty" end
 local value = self[last]
 self[last] = nil -- to allow collection
 self.last = last-1
 return value
end
function List:reverse ()
 local i, j = self.first, self.last
 while i<j do
 self[i], self[j] = self[j], self[i]
 i = i+1
 j = j-1
 end
end
function List:equal (otherlist)
 if self:length() ~= otherlist:length() then return nil end
 local diff = otherlist.first - self.first
 for i1=self.first,self.last do
 if self[i1] ~= otherlist[i1+diff] then return nil end
 end
 return 1
end
-----------------------------------------------------------
-----------------------------------------------------------
-- Some tests
function test ()
 local SIZE = 10000
 -- create a list with elements 1..SIZE
 local l1 = List:new()
 for i=1,SIZE do
 l1:pushright(i)
 end
 -- creates a copy of l1
 local l2 = l1:new()
 -- remove each individual item from left side of l2 and
 -- append to right side of l3 (preserving order)
 local l3 = List:new()
 while l2:length() > 0 do
 l3:pushright(l2:popleft()) 
 end
 -- remove each individual item from right side of l3 and
 -- append to right side of l2 (reversing list)
 while l3:length() > 0 do
 l2:pushright(l3:popright())
 end
 -- reverse l1 in place
 l1:reverse()
 -- compare Li1 and Li2 for equality
 -- and return length of the list
 if not l1:equal(l2) then return nil
 else return l1:length()
 end
end
N = tonumber((arg and arg[1])) or 1
for i=1, N do
 result = test()
end
print(result)