crash on compilable code: type of ... is not assigned

[helloqirun]

The latest stable release of scalac (version 2.12) can compile, but dotc crashes.

$ cat abc.scala
package +
import tools.nsc._, reporters._, typechecker._
class CustomGlobal(currentSettings: Reporter) extends Global(currentSettings) {
  override lazy val analyzer = new { val global: this.type = this }
  with Analyzer {
    override def newTyper(context: Context) = new CustomTyper(context)
    class CustomTyper(context: Context) extends Typer(context) {
      override def typed(tree: Tree, pt: Type) = {
        if (tree.summaryString contains "Bippy") ()
        super.typed(tree, pt)
      }
    }
  }
}

$ dotc abc.scala
-- [E009] Syntax Error: abc.scala:5:2 ------------------------------------------
5 |  with Analyzer {
  |  ^^^^
  |  early definitions are not supported; use trait parameters instead

longer explanation available when compiling with `-explain`
-- [E006] Unbound Identifier Error: abc.scala:1:8 ------------------------------
1 |package +
  |        ^
  |        not found: +

longer explanation available when compiling with `-explain`

exception occurred while compiling abc.scala
Exception in thread "main" dotty.tools.dotc.ast.Trees$UnAssignedTypeException: type of TypeDef(CustomGlobal,Template(DefDef(<init>,List(),List(List(ValDef(currentSettings,Ident(Reporter),EmptyTree))),TypeTree,EmptyTree),List(Apply(Select(New(Ident(Global)),<init>),List(Ident(currentSettings)))),ValDef(_,EmptyTree,EmptyTree),List(ValDef(analyzer,TypeTree,New(Template(DefDef(<init>,List(),List(),TypeTree,EmptyTree),List(),ValDef(_,EmptyTree,EmptyTree),List(ValDef(global,SingletonTypeTree(This(Ident())),This(Ident()))))))))) is not assigned
	at dotty.tools.dotc.ast.Trees$Tree.tpe(Trees.scala:97)
	at dotty.tools.dotc.ast.Trees$DenotingTree.denot(Trees.scala:236)
	at dotty.tools.dotc.ast.Trees$Tree.symbol(Trees.scala:148)
	at dotty.tools.dotc.typer.FrontEnd.firstTopLevelDef(FrontEnd.scala:73)
	at dotty.tools.dotc.typer.FrontEnd.discardAfterTyper(FrontEnd.scala:78)
<...>

[odersky]

Should be tested again when symblic names are in.