Typer deviation for (Function[0]) _

```
object O3 {
  def foo: Function0[Object] = {
    def bar = O3
    bar _
  }
  foo
}
```

```
$ scalac O3.scala
$ dotc O3.scala
O3.scala:4: error: type mismatch:
 found   : O3
 required: () => Object
    bar _
    ^
one error found
```
