Fixing vim's handling of the enclosing-type cache

[ELLIOTTCABLE]

The usage of the enclosing_types cache in the Vim plugin is pretty bugged — fixes #732, #770.

This is my first PR, so I intentionally went a bit overboard with explanatory comments; I also tried to match the code-style while moving things around.

I won't be offended at all if you have any feedback on how you want this cleaned up — feel free to throw any requirements at me if you want this massaged! <3

[ELLIOTTCABLE]

Anything blocking this? (=

[trefis]

Anything blocking this?

Yes, the lack of people available for reviewing :p

So, I just had a look, and it took me a while to see what the actual change was, that's because the diff is bigger than it needs to: why did you inline the function instead of living in on its own?
If you hadn't, the change would have been more obvious.

Apart from that nitpick I think I understand and agree with your change.

If you can undo the inlining and squash all your commits then I'll happily merge this.

[ELLIOTTCABLE]

@trefis hah! turns out my Python was just shaky. I needed access to enclosing_types[0] for the fix; I assumed it was local, didn't notice it was global, saw it was only used in one place, and took the expedient action. ‘Outlined!’

Squashing, rebasing, and pushing now. <3

[trefis]

Thank you!