support bottom type as receiver

[ptarjan]

I had a tough time writing a test for this since I couldn't figure out how to return the bottom type from real code

[jeffrey-s-foster]

I'm not sure I understand this proposed change. Am I right that it makes any method call on %bot return %bot? What's the intuition behind that choice?

[ptarjan]

This was needed after #48 so that you can do foo.bar.baz. Because we typed those unknown functions as returning %bot we also made it infectious here. Should it be returning something else? If so we can use that here.

[jeffrey-s-foster]

Okay to drop this in favor of #53? I like #53 much better.

[ptarjan]

+1 agreed