New scoping rule for "repeat" and "continue" patch

[Rici Lake <lua@...>]

I was interested to see that 5.1alpha implements a new scoping rule for 
"repeat" statements; the expression in the "until" clause is now 
*inside* the scope of the "repeat" block.

Unfortunately, this is not compatible with the semantics of "continue". 
Consider:

repeat
  local l = io.read"*l" or "quit"
  if l:match"^#" then continue end
  local g, rest = l:match"(%S+)%s*(.*)"
  local done = handle[g](g, words(rest))
until done

If the "continue" statement is executed, the "until" clause will be 
evaluated but the local "done" is uninitialised. Obviously, this could 
be fixed by defining done before the continue statement, but Lua will 
not detect the error, which I think is a showstopper.

If you want to test the code, here's a minimal test environment. You'll 
notice that the loop is terminated by a comment (i.e. a line starting 
#)

local function words(l)
  local rv = {}
  for w in l:gmatch"%S+" do table.insert(rv, w) end
  return rv
end

local function defaultTable(def)
  return setmetatable({}, {__index = function() return def end})
end

local function err(cmd)
  print(("I don't understand what you mean by %q"):format(cmd))
end

local handle = defaultTable(err)
function handle.quit()
  return true
end
function handle.hello()
  print "Hello, yourself"
end