Missing autocompletion for instances of Selectable

Compiler version

3.1.1

Minimized code

class Structural(map: Map[String, Any]) extends Selectable:
  def selectDynamic(name: String) = map(name)

type Person = Structural { val: name; val age: Int }

val p = new Structural(Map("name" -> "jacob", "age" -> 5)).asInstanceOf[Person]

p.name //I should see name + age in autocomplete

Output

There is no autocomplete for name or age.

Expectation

It would be great if there were autocomplete for name and age 😄

Notes

I’ve copied this issue from a metals issue after being informed that it may make more sense here (https://github.com/scalameta/metals-feature-requests/issues/238).

My hopes are that autocomplete for Selectable types can help provide a suitable replacement for annotation macros. I’m imagining a Macro that would generate a refined Selectable type. This Selectable instance would be a bag of autocompleteable methods based upon the structure of the given case class. Generating Lenses, for instance, could look like this:

case class Person(name: String, age: Int)

object Person {
  val lenses = Lenses.gen[Person]
}

Person.lenses.name // For this to be tenable, this would need to autocomplete with the type Lens[Person, String] 

[odersky]

OK, I note that there are important use cases. Thanks for pointing them out!

[jdegoes]

As a user, I would hope and expect that auto-complete is supported for all static types, including structural types, and I can think of many applications for this: for example, adding typing information to Spark workflows via metaprogramming (which can easily be done, but will be of limited use without auto-complete).

Separately, I do believe that export should work uniformly across nominal and structural types. One of the most tangible and practical perks of working with Scala 3 is the enhanced uniformity it brings to the language, and it would be a shame (in my view) to pass up the opportunity to make export work uniformly.