• Adds destructuring assignment (x, y) <- (a = 1, b = 2). I hope to expand this in the future for arbitrarily nested built-in data type matching, but for now it only works with named and unnamed symbols.

Minor changes

• Updated pairs syntax (used for vectors and lists) to disallow more than one trailing comma
• Disallow .s in symbols! After many years of R this still feels weird and is used for both names and meaningful S3 method notation.
• Trying to index into a list with a name it does not contain no longer erroneously returns the first element.