Allow recursive contract definitions

[gregwebs]

This is a very confusing error message. In this case:

MyC = ?({ myc: -> MyC })

The message should be: "recursive contract 'MyC'", please use Self

[disnet]

Wow, that is a terrible error message.

I wonder if instead of throwing an error we could just allow recursive definitions and add the self implicitly? You'd still need to explicitly use self sometimes for nested objects:

Obj = ?{ my_obj: Obj, inner: { inner_obj: Self}}
# or if we get fancy
Obj = ?{ my_obj: Obj, inner: { inner_obj: Obj.inner}}
# but even then we could never completely drop self
Fun = ?(Num, { my_obj: Self }) -> Any

Think it's worth allowing recursive definitions or just keep the single self way (with a better error message)?

[gregwebs]

I like the recursive definitions: that is what I tried first. Keeping Self is fine though.