Wrong linearization for super calls in case classes

[ddtthh]

Compiler version

3.2.2
3.3.0-RC3
Worked in 3.1.2

Minimized code

class Root {
  override def toString() = "Root"
}
trait A extends Root with B {  }
trait B {
   override def toString() = "B"
}
case class C() extends A {
  override def toString() = super.toString()
}

println(C())

Output

Root

Expectation

toString in trait B should be called and output should be B.
This works for normal classes, but the case class breaks that.

[szymon-rd]

Regression, behavior changed in 3.2.0-RC1

[szymon-rd]

Bisected to first bad commit 16b8e07f189610fd620c1ab9f93f9e78643b36ca - #15416
@anatoliykmetyuk

[odersky]

@szymon-rd Thanks for the bisect! That would have been much harder to diagnose otherwise.