Fix scope chaining

[dfellis]

This is blocking #747 (and probably other things) because I cannot call function arguments as the scope chain is unexpectedly empty, excepting the root scope.

All because of the s.clone() in this line

But fixing that breaks so much other code, so I need to rework a significant chunk of scope logic to resolve this, potentially rewriting much of it.

[dfellis]

I forgot to close this last night. It was fixed by #816