See the Air docblock for more information. I'm introducing new tokens for
the template system, which uses the terms "free" and "closed". I prefer
open/close for delimiters, as I've expressed elsewhere, but unfortunately it
conflicts too much (and too confusingly) with other standard terminology as
we get more into the formal side of the language.
DEV-13708
This removes special cases, but it does complicate the parent `AirAggregate`
parser. A pattern of delegation is forming, though abstracting it may be an
interesting challenge, given Rust's limitation on macro invocations as match
arms. But, I think I can manage by generating the entire match using a
macro with a match-compatible syntax, augmenting where
needed...maybe. This'll be messy.
...but if I can write the nightmare that is `ele_parse!`, I'm sure I can
manage this. I just prefer to avoid complex macros unless I really need
them.
DEV-13708
And finally we have tokens aggregated onto the ASG in the context of a
template. I expected to arrive here much more quickly, but there was a lot
of necessary refactoring. There's a lot more that could be done, but I need
to continue; I had wanted this done a week ago.
It is worth noting, though, that this finally achieves something I had been
wondering about since the inception of this project---how I'd represent
templates on the graph. I think this worked out rather nicely. It wasn't
even until a few months ago that I decided to use AIR instead of NIR for
that purpose (NIR wouldn't have worked).
And note how I didn't have to touch the program derivation at all---the
system test just works with the AIR change, because of the consistent
construction of the graph. Beautiful.
DEV-13708
This sets us up to be able to determine how `Dangling` expressions will be
rooted into templates.
This new strategy isn't yet handling `Dangling`; I wanted to get this
committed first so that the `Dangling` refactoring is more clear.
DEV-13708
Expressions were previously tied to packages. This prepares for using a
`Tpl` as a container for expressions.
This does not yet handle the situation of auto-rooting dangling expressions
within the container.
DEV-13708
Mike Gerwitz