Conventions

As far as possible, no mutual, always forward declare.
- Related: no declaring in one module and defining in another
Indent so that alpha conversion always works with a simple search and replace. In general this would mean starting a new line when starting a new level of indentation.
- Indent by a consistent amount (eg 4 spaces), rather than trying to line up with the previous line. This makes diffs smaller and makes it easier to type.
Use parameters blocks for avoiding boilerplate when passing state around. If this exposes any bugs with parameter blocks in Idris 2, we must fix the bug rather than working around it.

Some high level decisions

Module hierarchy:
- Idris.* and Compiler.* can import from any part of the hierarchy
- TTImp.* may not import Idris.* or Compiler.*
- Core.* may not import TTImp.*, Idris.* or Compiler.*
- In other words: Idris.* and Compiler.* are considered Idris front-end, TTImp is a library for elaborating TT with implicits, and Core is a library for the core type theory.
- Eventually, ttimp should be a package of its own consisting of the TTImp.* and Core.* parts of the hierarchy.
Let's not invent anything new unless we have absolutely no other option! It's more important to do what we already know as well as we possible can.
Other than changing pattern matching from a top level concept to a case block, we'll keep other features of the theory pretty much the same. In particular this means:
- RigCount is not yet first class, and we'll fix it at 0,1,unrestricted for now
- No OTT just yet!
Aim for incremental checking, rather than batch checking of files
- In practice, I think this is about calculating dependencies of definitions and shouldn't be too tricky, but important to remember it up front at least.