Scala Trait linearization

gistfile1.txt

Welcome to Scala version 2.9.1.r0-b20120125223512 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_02).
Type in expressions to have them evaluated.
Type :help for more information.

scala> trait A
defined trait A

scala> trait C extends A
defined trait C

scala> trait B extends A
defined trait B

scala> trait D extends B
defined trait D

scala> trait E extends C
defined trait E

scala> class D extends A with D with E
<console>:12: error: class D inherits itself
       class D extends A with D with E
                              ^

scala> class F extends A with D with E
defined class F

scala> :power
** Power User mode enabled - BEEP BOOP SPIZ **
** :phase has been set to 'typer'.          **
** scala.tools.nsc._ has been imported      **
** global._ and definitions._ also imported **
** Try  :help,  vals.<tab>,  power.<tab>    **

scala> intp.types("F").tpe.baseTypeSeq.toList
res0: List[$r.intp.global.Type] = List(F, D, E, C, B, ScalaObject, A, java.lang.Object, Any)

Tada!

This works:

Welcome to Scala 2.12.4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_144).
Type in expressions for evaluation. Or try :help.

scala> :paste
// Entering paste mode (ctrl-D to finish)

trait A { def foo = "a" }
trait B extends A {  override def foo = "b" + super.foo }
trait D extends A {  override def foo = "d" + super.foo }
trait C extends B {  override def foo = "c" + super.foo }
class Qux extends A with C with B with D

// Exiting paste mode, now interpreting.

defined trait A
defined trait B
defined trait D
defined trait C
defined class Qux

scala> :power
Power mode enabled. :phase is at typer.
import scala.tools.nsc._, intp.global._, definitions._
Try :help or completions for vals._ and power._

scala> intp.exprTyper.typeOfTypeString("Qux").baseClasses
res0: List[$r.intp.exprTyper.repl.global.Symbol] = List(class Qux, trait D, trait C, trait B, trait A, class Object, class Any)

Documentation for the method is here: https://github.com/scala/scala/blob/v2.12.4/src/reflect/scala/reflect/internal/Types.scala#L909