Pattern/binding/parameter issues

[dhess]

We have a bunch of issues all somewhat related:

• How should we render patterns/bindings? https://github.com/hackworthltd/vonnegut/issues/290
• Better rendering of case expresisons https://github.com/hackworthltd/vonnegut/issues/271
• How could we render multiple equations with pattern matching? https://github.com/hackworthltd/vonnegut/issues/272
• Non-selectable nodes (e.g., case branch labels) should be indicated somehow https://github.com/hackworthltd/vonnegut/issues/263
• We currently can't rename variables bound in case branches https://github.com/hackworthltd/vonnegut/issues/233

Also, these or related issues have recently come up in PRs https://github.com/hackworthltd/vonnegut/pull/303 and https://github.com/hackworthltd/vonnegut/pull/285

What these issues have in common is that we don't handle patterns/bindings/parameters very well. I, for one, am having trouble keeping track of all these different discussions, searching the tracker for related issues, and determining what are the root causes or missing functionalities.

Let's use this issue to come up with some prioritized, actionable changes that will result in patterns/bindings/parameters being first class citizens of our programs.

[hmac]

I've written a proposal to address these issues here.