rest arguments without type hint are not parsing

[nadako]

The following fails to parse with Unexpected )

function f(...rest) {}

[nadako]

I assume that we need some notion of monomorph at untyped ast level so we can generate haxe.Rest<?> as a type hint there? We could either introduce CTMono or hack it in with CTPath mono where mono is some global instance of type_path to be processed by the typer.