Add simplified toString on Positions which matches pickled data

Author: OlivierBlanvillain

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

@@ -531,7 +531,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       else if (!tree.isDef) txt = ("<" ~ txt ~ ":" ~ toText(tp) ~ ">").close
     }
     if (ctx.settings.Yprintpos.value && !tree.isInstanceOf[WithoutTypeOrPos[_]])
-      txt = txt ~ "@" ~ tree.pos.toString
+      txt = txt ~ "@" ~ tree.pos.toString(simplified = true)
     tree match {
       case Block(_, _) | Template(_, _, _, _) => txt
       case _ => txt.close

src/dotty/tools/dotc/util/Positions.scala

@@ -108,10 +108,12 @@ object Positions {
     /** A synthetic copy of this position */
     def toSynthetic = if (isSynthetic) this else Position(start, end)
 
-    override def toString = {
-      val (left, right) = if (isSynthetic) ("<", ">") else ("[", "]")
+    override def toString: String = toString(simplified = false)
+
+    def toString(simplified: Boolean): String = {
+      val (left, right) = if (simplified || isSynthetic) ("<", ">") else ("[", "]")
       if (exists)
-        s"$left$start..${if (point == start) "" else s"$point.."}$end$right"
+        s"$left$start..${if (simplified || point == start) "" else s"$point.."}$end$right"
       else
         s"${left}no position${right}"
     }