I'm not necessarily suggesting this should do anything useful, just that it shouldn't crash.
scala> class A { var i = 0 ; trait A1 extends A { i += 1 } }
defined class A
scala> new A with A#A1
Exception in thread "main" java.lang.AssertionError: assertion failed: $$iw.$$iw.A
at scala.Predef$$.assert(Predef.scala:97)
at scala.tools.nsc.ast.TreeGen.mkAttributedQualifier(TreeGen.scala:75)
at scala.tools.nsc.ast.TreeGen.mkAttributedQualifier(TreeGen.scala:41)
at scala.tools.nsc.transform.ExplicitOuter$$ExplicitOuterTransformer.mixinOuterAccessorDef(ExplicitOuter.scala:323)
I'm not necessarily suggesting this should do anything useful, just that it shouldn't crash.