Unformated tree in error emitted when abstract member is not defined.

[nicolasstucki]

abstract class Foo {
  def f(i: Int): Unit
}
class Bar extends Foo {
  def f(i: String): Unit = ???
}

error: class Bar needs to be abstract, since def f: (i: Int)Unit is not defined 
(Note that TypeRef(TermRef(ThisType(TypeRef(NoPrefix,<root>)),scala),Int) does not match TypeRef(TermRef(ThisType(TypeRef(NoPrefix,scala)),Predef),String))
class Bar extends Foo {
      ^

Note that the types are printed as trees.