Show LazyRefs nicely

Previously, this fell back to toString

Author: odersky

src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -170,6 +170,8 @@ class PlainPrinter(_ctx: Context) extends Printer {
             else TypeBounds.empty
           "(" ~ toText(tp.origin) ~ "?" ~ toText(bounds) ~ ")"
         }
+      case tp: LazyRef =>
+        "LazyRef(" ~ toTextGlobal(tp.ref) ~ ")"
       case _ =>
         tp.fallbackToText(this)
     }