Mega-PR: transpiler optimisations, expanded Vim bindings

[mrkgnao]

This includes

• rudimentary dead-code elimination for top-level functions which are not called at all
• tail-call elimination for simple (i.e. not mutually) recursive functions
• a sketch of a renamer, which only annotates function names with their arities for now (IRTS.Simplified generates multiple functions with the same name due to partial application, which complicates DCE and inlining since one fails to have a bijection between function names and functions)
• a simple inliner that inlines all Vim primitives (this may have to be restricted -- what about huge lists? -- and will definitely have to be expanded -- otherwise we don't get TCO for mutually recursive functions!)

The code is badly formatted and needs a lot of uniplate/Control.Lens.Plated love.

[mrkgnao]

Let's start merging this, @owickstrom. The only real outstanding issue is https://github.com/owickstrom/idris-vimscript/issues/6, which I can fix while you're reviewing this PR.

[owickstrom]

@mrkgnao Absolutely!

[owickstrom]

I think the lack of uniplate tricks is fine for now, I'd rather not make the PR any larger. I do have a bunch of pedantic things that would be nice to fix:

• Language extensions on separate lines
• No redundant imports
• No Debug.Trace on master 😃
• Fix all GHC and hlint warnings (unused bindings, shadowing, etc). I'm keen on having a CI build fail on such warnings later, but that is further up the line.
• Run through stylish-haskell, and preferably hindent

Do these things make sense to you?

[mrkgnao]

Do these things make sense to you?

Yes, of course. I'll make sure that this passes the, er, idris-vimscript style guide before it gets merged. :P

Do you have any other code changes to request before I do?

[owickstrom]

Great job, @mrkgnao! 👍 💯

[mrkgnao]

Woohoo!