Compiler: better support for promise chains

Did we miss a trick with promise chains? Should we be able to support an operation inside a .then callback?

We can currently do this:

each(
  $.items,
  post(`patient/${$.data.id}`, $.data).then(state => {
    state.completed.push(state.data);
    return state;
  })
);

But surely it would be cool to support this?

each(
  $.items,
 get(`patient/${$.data.id}`)
   .then(post(`patient/${$.data.id}`, $.data))
   .then((state => {
    console.log('done!')
    return state
  })
)

What I'm saying is that inside then() we should be able to write an operation, without a ()(state) wrapper.

Either compiler code, or some magic in promises (perhaps even a custom promise library), would have to "unwrap" the operation.

Something like this maybe?

each(
  $.items,
 get(`patient/${$.data.id}`)
   .then((state) => post(`patient/state{state.data.id}`, state.data)(state))
   .then((state => {
    console.log('done!')
    return state
  })
)

But my feeling is:

• .then() is called with state
• .then(get()) will pass a function into .then(), which will be lazily executed
• Can we extend .then() to recognise that an Operation has been passed in, and handle it appropriately? I should have all the information it needs.

Start by tracing how the compiler and promise handling represent operations passed to .then(), using the examples in the issue as the behavioral reference. Determine whether direct operations can be recognized and lazily executed without the current ()(state) wrapper; done means promise chains support this form while preserving ordinary callback behavior.