Promise API conundrum

gistfile1.js

// my thing
Thing = {
  
  addPromise: function(fn){
    Promise.resolve(fn.call(this, 'input'))
      .then(function(val){
         //do wahtever
      })
  },
  
  addNode: function(fn){
    fn.call(this, 'input', done)
    
    function done(val){
      //do wahtever
    }
  }
}

// consumer provides a fn to my Thing

Thing.addNode(function(input, done){
  doAsyncWork(input, function(err,val){
    done(err, val)
  })
})

Thing.addPromise(function(input){
  return doAsyncWork(input)
})

Thing.addPromise(function(input){
  return input + "sync value"
})