T = require 'tcomb-promise'

User = T.struct
  name: T.String
  email: T.String
, 'User'

fetchUser = T.func T.String, T.promise(User)
.of (id) ->
  fetch "https://example.com/users/#{id}"
  .then ({data}) -> data

fetchUser('someId').then (u) ->
  # result is automatically hydrated
  User.is(u) == true