This type should be able to replace Separated (with a bit of effort).
The hope is that this type is a better representation for table-like
syntax with optional trailing delimiter that will let me remove_map
elements without too much difficulty. This is necessary for desugaring
table constructors.
I noticed that programs like '{} would parse correctly while '{ } would
expect an inner element. This was because the leading space was actually
part of the element parser, which is a violation of the (as of yet
unspoken) rule that parsers should not parse surrounding whitespace.
Because whitespace whas treated differently from everywhere else and
because this implementation was wrong, I decided to reimplement it,
abstracting the concept of things separated by other things with
optional trailing things. I did this in such a way that surrounding
whitespace is not touched.
The structure mostly follows the ast structure, with some slight
changes. Each parser submodule documents which ast submodule it
corresponds to.
This parser is not yet complete, and I have yet to go through its
modules one-by-one to fix and complete them.
