Bootstrap failure: wrong static initializer of inner class

[odersky]

If I compile everything in src/dotty and run the resulting program without arguments I get:

dotc
Exception in thread "main" java.lang.NoSuchMethodError: dotty.tools.dotc.ast.Trees$Instance$TreeMap$: method ()V not found
at dotty.tools.dotc.ast.Trees$Instance$TreeMap$.(Trees.scala)
at dotty.tools.dotc.ast.Trees$Instance.(Trees.scala:1087)
at dotty.tools.dotc.ast.untpd$.(untpd.scala:13)
at dotty.tools.dotc.ast.untpd$.(untpd.scala)
at dotty.tools.dotc.core.Contexts$InitialContext.(Contexts.scala:467)
at dotty.tools.dotc.core.Contexts$ContextBase.(Contexts.scala:493)

Investigation with javap shows that TreeMap has a static initializer which tries to create a TreeMap object with an empty constructor. But TreeMap is an inner class, so the constructor takes an outer pointer.

Compiled from "Trees.scala"
public final class dotty.tools.dotc.ast.Trees$Instance$TreeMap$ {
public static final dotty.tools.dotc.ast.Trees$Instance$TreeMap$ MODULE$;

public static {};
Code:
0: new #2 // class dotty/tools/dotc/ast/Trees$Instance$TreeMap$
3: invokespecial #23 // Method "":()V
6: return

public dotty.tools.dotc.ast.Trees$Instance$TreeMap$(dotty.tools.dotc.ast.Trees$Instance);
Code:

The whole static initializer seems to be a random artefact, since TreeMap does not have a companion object.

Edit: No, it does have a synthetic companion object (which contains default arguments). But since it's an inner class of the outer class Instance it should not have a static initializer that creates an instance, it seems to me.