Compiler: something up with promise catch

I confused myself over this today and it became a problem

I want to do this:

each($.data, get()
  .then(...)
  .catch(...)
)

Ie for each item, I call get(), and I do one thing if the request succeeds, and another thing if it fails.

But I think there's a problem on the catch, because it doesn't receive a state object. Or maybe it receives a wierd one? Or wait I think I'm catching an error on the .then() handler, not the get itself?

This also doesn't work:

each($.data, get()
  .catch(...)
  .then(...)
)

Because it'll catch the error and THEN trigger the .then(), which isn't what we want.

Something is up here, and the docs don't show an example of a .then() AND a .catch() on the same operation. Need to investigate, fix and clarify.

Also, while I'm here, need to ensure that catch receives the last-good-state (the state before the throw), and that whatever the catch returns is the next state going forward.

Start in the compiler's promise handling and reproduce the two each($.data, get()...) examples from the issue. Trace whether catch receives the last-good state and whether its return value becomes the next state, then document and verify the intended then()/catch() behavior with examples.