Named arguments' behavior is not same to Scala 2

[floating-cat]

The following code fails in scala 2.12.2:

scala> def printName(first: String, last: String): Unit = {
     |   println(first + " " + last)
     | }
printName: (first: String, last: String)Unit

scala> printName("John", first = "Smith")
<console>:13: error: parameter 'first' is already specified at parameter position 1
       printName("John", first = "Smith")
                               ^

But compiles in dotty (Scastie link):

object Main {
  def printName(first: String, last: String): Unit = {
    println(first + " " + last)
  }

  def main(args: Array[String]): Unit = {
    printName("John", first = "Smith")
  }
}

scastie: Connecting.
scastie: Connected.
sbt: [info] Compiling 1 Scala source to /tmp/scastie5500368941075143733/target/scala-0.1/classes...
sbt: [info] Running Main
Smith John

If the new behavior is intentional, the similar code (I use last: String* instead of last: String) fails in dotty (Scastie link):

object Main {
  def printName(first: String, last: String*): Unit = {
    println(first + " " + last)
  }

  def main(args: Array[String]): Unit = {
    printName("John", first = "Smith")
  }
}

scastie: Connecting.
scastie: Connected.
sbt: [info] Compiling 1 Scala source to /tmp/scastie5500368941075143733/target/scala-0.1/classes...
sbt: [info] Running Main
sbt: [error] (run-main-10b) java.lang.NoClassDefFoundError: scala/$repeated$
sbt: java.lang.NoClassDefFoundError: scala/$repeated$
	at Main$.main(main.scala:7)
	at Main.main(main.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
Caused by: java.lang.ClassNotFoundException: scala.$repeated$
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at Main$.main(main.scala:7)
	at Main.main(main.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
[trace] Stack trace suppressed: run 'last compile:run' for the full output.
sbt: java.lang.RuntimeException: Nonzero exit code: 1
	at scala.sys.package$.error(package.scala:27)
[trace] Stack trace suppressed: run 'last compile:run' for the full output.
sbt: [error] (compile:run) Nonzero exit code: 1