Cyclic reference error involving CanBuildFrom in implicit objects

[pweisenburger]

The following code compiles on Scala but produces a cyclic reference involving trait CanBuildFrom compiler error on Dotty:

class Test[T](f: List[String] => T)

object o {
  implicit object a extends Test(_ map identity)
  implicit object b extends Test(_ map identity)
}

[allanrenucci]

Slightly minimised:

import scala.collection.generic.CanBuildFrom

class Test {
  implicitly[CanBuildFrom[List[_], Int, List[Int]]]

  class Foo[T](x: T)
  implicit object Bar extends Foo(
    implicitly[CanBuildFrom[List[_], Int, List[Int]]]
  )
}

> dotc tests/allan/Test.scala
-- [E045] Syntax Error: tests/allan/Test.scala:21:30 ---------------------------
21 |  implicit object Bar extends Foo(
   |                              ^
   |                           cyclic reference involving trait CanBuildFrom
22 |    implicitly[CanBuildFrom[List[_], Int, List[Int]]]