Do you want to request a feature or report a bug?

I want to request a feature

What is the current behavior?

Currently, when using toast.promise you can only set a toast's type as a string, eg.:

toast.promise( fetcher, {
   success: {
      render: ( { data } ) => "Post ${data.title} was successfully created!",
      type: "success"
   },
   error: {
      render: "Something went wrong!",
      type: "error"
   },
})

What is the expected behavior?

It would be nice if type accepted a function that receives the data (just like render), and determine the type based on that data. I'm asking because eg. when requesting data with GraphQL, the request may be successful (ie. the fetcher doesn't throw an error, so the error toast is not used), but the successful response may still contain errors, so I would basically turn the success toast into an error toast, something like this:

toast.promise( fetcher, {
   success: {
      render: ( { data: result } ) => {
         const { data, errors } = result
         return errors ? "Something went wrong" : "Post ${data.title} was successfully created!", 
      },
      type: ( { data: result } ) => {
         const { data, errors } = result
         return errors ? "error" : "success"
      },
   },
   error: {
      render: "Something went wrong!",
      type: "error"
   },
})

I am currently working around this by using a try/catch block and toast.update as explained in #726, but I like the toast.promise signature better :)