move arg_types to TokenIter

lips/Collector.lua

@@ -11,14 +11,6 @@ function Collector:init(options)
     self.options = options or {}
 end
 
-Collector.arg_types = { -- for instructions
-    NUM = true,
-    REG = true,
-    VARSYM = true,
-    LABELSYM = true,
-    RELLABELSYM = true,
-}
-
 function Collector:statement(...)
     local I = self.iter
     local s = Statement(I.fn, I.line, ...)
@@ -186,7 +178,7 @@ function Collector:instruction(name)
             I:next()
         elseif I.tt == 'SEP' then
             I:error('extraneous comma')
-        elseif not self.arg_types[I.tt] then
+        elseif not I.arg_types[I.tt] then
             I:error('unexpected argument type in instruction', I.tt)
         else
             insert(s, t)

lips/TokenIter.lua

@@ -16,6 +16,14 @@ function TokenIter:init(tokens)
     self:reset()
 end
 
+TokenIter.arg_types = {
+    NUM = true,
+    REG = true,
+    VARSYM = true,
+    LABELSYM = true,
+    RELLABELSYM = true,
+}
+
 function TokenIter:error(msg, got)
     if got ~= nil then
         msg = msg..', got '..tostring(got)
@@ -176,7 +184,7 @@ function TokenIter:special()
     local args = {}
     while true do
         local arg = self:advance()
-        if not arg_types[arg.tt] then
+        if not self.arg_types[arg.tt] then
             self:error('invalid argument type', arg.tt)
         else
             self:advance()