Document given CanEqual on companion objects

Compiler version

scala 3.0

Minimized example

import scala.language.strictEquality

case class Suit(value: String)

object Suit:
  given CanEqual[Suit, Suit] = CanEqual.derived

@main def main =
  println(Suit("X") == Suit("X"))

Output

true

Expectation

According to https://github.com/lampepfl/dotty/blob/a9a7e7042408dd0de6cebdddc5fc23a6e33d26be/docs/docs/reference/contextual/multiversal-equality.md#precise-rules-for-equality-checking objects can be compared using == under strictEquality if there is a given of type CanEqual[T, U].

In the example above it’s not clear (to me) and I can’t find documentation as to why the given CanEqual in the companion object is available in this case. AFAICT, it is in general not available as given at the main scope without an import.

Thank you

[som-snytt]

@amitport The amended doc is at https://dotty.epfl.ch/docs/reference/changed-features/implicit-resolution.html

The relevant section is Nr 3, which I had previously skipped because of tldr; The terminology is revised but the gist is similar.

There is a TODO on the page to refine it.

I agree that if I’ve read something in the reference docs, but I need to find it again because I haven’t had enough opportunity to use Scala 3, it can be hard to find what I need. Sometimes I grep the repo.

I don’t know how this topic is covered in introductory materials.

[amitport]

Thanks, I saw that one, but it’s not really “reader-friendly”, and missing some details.

Hopefully, at some point, scala3 language guides would contain all the language semantics without referring to scala2 language specification (the reference is also missing in this case) + migration guide.