False kind inference error, with confusing error message

[scabug]

Below is the output of the REPL when pasting the content of the attached file. First of all, I wouldn't expect any error. Second, this error message is confusing:

    class Option has one type parameter, but type F has one

---

$ ./scala-2.12.0-RC1/bin/scala
Welcome to Scala 2.12.0-RC1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_102).
Type in expressions for evaluation. Or try :help.

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

import scala.language.higherKinds

trait Foo[A] {
  type F[_]
}

object Foo {
  // two identical auxiliary type aliases
  type Aux1[A, F0[_]] = Foo[A] { type F[X] = F0[X] }
  type Aux2[A, F0[_]] = Foo[A] { type F[X] = F0[X] }

  def bar[A, F[_]](a: A)(implicit ev: Foo.Aux1[A, F]): Foo.Aux1[A, F] = ev

  implicit def ev: Foo.Aux1[String, Option] = new Foo[String] { type F[X] = Option[X] }

  val fooStringOption: Foo.Aux2[String, Option] = bar("hi")
}

// Exiting paste mode, now interpreting.

<console>:26: error: inferred kinds of the type arguments (String,Option[X]) do not conform to the expected kinds of the type parameters (type A,type F).
Option[X]'s type parameters do not match type F's expected parameters:
class Option has one type parameter, but type F has one
         val fooStringOption: Foo.Aux2[String, Option] = bar("hi")
                                                         ^
<console>:26: error: type mismatch;
 found   : String("hi")
 required: A
         val fooStringOption: Foo.Aux2[String, Option] = bar("hi")
                                                             ^

scala> 

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9950?orig=1
Reporter: Tomas Mikula (tomas.mikula-at-gmail.com)
Affected Versions: 2.12.0-RC1
Attachments:

• inferred-kinds.scala (created on Oct 5, 2016 11:59:58 PM UTC, 454 bytes)

[som-snytt]

compiles in 2.13 but not 2.12.20