crash with compilable code: "java.lang.UnsupportedOperationException: multi-denotation with alternatives"

[helloqirun]

(The trunk version of) scalac can compile but dotc crashes. scalac-2.9 emits an error.
Moreover, if I "beautify" the code a bit, dotc does not crash.

$ cat good.scala

 import  java . io ._
 import  collection ._
 object  Test { def  check ( obj : AnyRef ){
 val  bos = new  ByteArrayOutputStream ()
 val  out = new  ObjectOutputStream ( println )
 val  arr = bos  toByteArray ()
 val  in =(())
 val  deser =()
 val  lhs = mutable  LinkedHashSet ()
 check ( lhs )}}

$ dotc good.scala

-- [E040] Syntax Error: good.scala ---------------------------------------------
4 | object  Test { def  check ( obj : AnyRef ){
  |                                           ^
  |                                          '=' expected, but `AnyRef` found

longer explanation available when compiling with `-explain`
-- [E040] Syntax Error: good.scala ---------------------------------------------
11 | check ( lhs )}}
   |               ^
   |               eof expected, but `lhs` found
13 |

longer explanation available when compiling with `-explain`

exception occurred while typechecking good.scala

exception occurred while compiling good.scala
Exception in thread "main" java.lang.UnsupportedOperationException: multi-denotation with alternatives List(method println, method println) does not implement operation info
	at dotty.tools.dotc.core.Denotations$MultiDenotation.multiHasNot(Denotations.scala:595)
	at dotty.tools.dotc.core.Denotations$MultiDenotation.infoOrCompleter(Denotations.scala:558)
	at dotty.tools.dotc.core.Denotations$MultiDenotation.info(Denotations.scala:559)
	at dotty.tools.dotc.core.Denotations$MultiDenotation.info(Denotations.scala:557)
	at dotty.tools.dotc.core.Types$NamedType.info(Types.scala:1618)
	at dotty.tools.dotc.core.TypeComparer.compareNamed$1(TypeComparer.scala:164)
	at dotty.tools.dotc.core.TypeComparer.dotty$tools$dotc$core$TypeComparer$$firstTry(TypeComparer.scala:205)
	at dotty.tools.dotc.core.TypeComparer$$anonfun$isSubType$1.apply$mcZ$sp(TypeComparer.scala:112)
	at dotty.tools.dotc.core.TypeComparer$$anonfun$isSubType$1.apply(TypeComparer.scala:104)
	at dotty.tools.dotc.core.TypeComparer$$anonfun$isSubType$1.apply(TypeComparer.scala:104)
<snipped>

[helloqirun]

The "beautified" code:

$ cat abc.scala

import java.io._
import collection._
object Test {
  def check(obj: AnyRef) {
    val bos = new ByteArrayOutputStream()
    val out = new ObjectOutputStream(println)
    val arr = bos toByteArray ()
    val in = (())
    val deser = ()
    val lhs = mutable LinkedHashSet ()
    check(lhs)
  }
}