Incorrect parsing of binary operator chain, when metatables are involved

[toxamin]

Currently, it is assumed that the following operators may be chained while omitting parentheses: ["..", "and", "or", "+", "*", "&", "|"].
However, this becomes an issue when a metatable that has special operator functions is operated on. For example, consider this piece of code:
local ret = 4 + (setmetatable({}, { __add = function(_, val) return val * 2; end }) + 64) return ret

Here, the metatable will be operated on with the + operator and the number 64 FIRST, and then 4 will be added to the result, however these semantics are thrown out after parsing the script, leaving us with this result:
local ret = 4 + setmetatable({}, {__add=function(_, val) return val * 2; end}) + 64; return ret;
Now, because the parentheses were omitted, the behavior has changed, and no longer will the metatable function be called with 64 first.

Proposed solution: Consider adding a check to make sure that each member of the binary operator chain is a number, before assuming parentheses are safe to remove.