Fix for RestArguments derivation.
Fix for RestArguments derivation.

briantrice/slate-language,krfkeith/slate-language,krfkeith/slate-language,krfkeith/slate-language,briantrice/slate-language,briantrice/slate-language,krfkeith/slate-language,briantrice/slate-language,briantrice/slate-language,briantrice/slate-language,krfkeith/slate-language,krfkeith/slate-language