Nobuyoshi Nakada wrote:
> * how to represent default arguments. They can be arbitrary
>   expressions not only simple literals, for instance,
>   preceeding parameters can be there, and any (parenthesized)
>   statements e.g. if, case, while, class, and etc.

For the JRuby args support (and I believe the ParseTree support) we 
agreed only the simplest literal types would be supported, which 
includes Fixnum, Symbol, and String in JRuby. This isn't intended to be 
a complete parameter-list specification as much as informational, and 
arbitrary defaults would fall outside the domain of informational.

- Charlie