Regression in ist-dsi/scala-keystone-client

[WojciechMazur]

Regression found in Open CB for ist-dsi/scala-keystone-client - build logs

Compiler version

3.3.1-RC1-bin-20230204-a356581-NIGHTLY
3.3.1-RC4
Bisect points to 11854bb

If you're not sure what version you're using, run print scalaVersion from sbt
(if you're running scalac manually, use scalac -version instead).

Minimized code

abstract class Service[F[_]](val name: String)
abstract class CrudService[F[_]](name: String) extends Service[F](name)

trait Foo[F[_]] { self: CrudService[?] =>
  val x = self.name
}

Output

-- [E008] Not Found Error: /Users/wmazur/projects/dotty/bisect/main.scala:6:15 -
6 |  val x = self.name
  |          ^^^^^^^^^
  |value name is not a member of CrudService[?[_$2]] & Foo[F] - did you mean (Foo.this : CrudService[?[_$2]] & Foo[F]).name?

Expectation

I'm not sure if it's a fix of corner case or real regression, it's only present when using at least 1 wildcard type. When defining self: CrudService[F] => it fails with every stable Scala version

> scala-cli compile  --server=false bisect/main.scala -S 3.0 
-- [E008] Not Found Error: /Users/wmazur/projects/dotty/bisect/main.scala:6:15 -
6 |  val x = self.name
  |          ^^^^^^^^^
  |value name is not a member of CrudService[F] & Foo[F] - did you mean (Foo.this : CrudService[F] & Foo[F]).name?

[prolativ]

It looks like the type parameters were only hiding the original problem. The snippet below compiles in scala 2 but doesn't compile in any release of scala 3

class Service(val name: String)
class CrudService(name: String) extends Service(name)

trait Foo { self: CrudService =>
  val x = self.name
}

It seems like the problem is in the clash of names between the parameter name: String of the subclass CrudService and the parameter member val name: String of the superclass Service.
If we remove the clash, e.g.

class Service(val name: String)
class CrudService(name1: String) extends Service(name1)

trait Foo { self: CrudService =>
  val x = self.name
}

the code compiles successfully

[odersky]

@prolativ Great minimization! That helped me not going down some other rabbit holes.