Newtype enum dereferences

[sanxiyn]

I noticed this while trying to remove codes related to newtype enums. Newtype enum syntax is gone, but rustc still relies on autodereference behavior.

Most notably, syntax::visit::vt<E> is an enum but codes access fields such as visit_expr. Since it is a newtype enum (one variant and one argument) it currently works, but I think the idea is to get rid of newtype enum dereferences?

My attempt to replace it with a newtype struct met ICEs and was unsuccessful.

[thestinger]

This is still an issue, but it's not clear if this is what we want to do. Tagging this as an RFC.

[brson]

Fixed.