Implement -Ydebug-pos

When set, prints full source positions, not just file + line.

Author: odersky

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -87,6 +87,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val YdebugFlags: Setting[Boolean] = BooleanSetting("-Ydebug-flags", "Print all flags of definitions")
   val YdebugMissingRefs: Setting[Boolean] = BooleanSetting("-Ydebug-missing-refs", "Print a stacktrace when a required symbol is missing")
   val YdebugNames: Setting[Boolean] = BooleanSetting("-Ydebug-names", "Show internal representation of names")
+  val YdebugPos: Setting[Boolean] = BooleanSetting("-Ydebug-pos", "Show full source positions including spans")
   val YtermConflict: Setting[String] = ChoiceSetting("-Yresolve-term-conflict", "strategy", "Resolve term conflicts", List("package", "object", "error"), "error")
   val Ylog: Setting[List[String]] = PhasesSetting("-Ylog", "Log operations during")
   val YemitTastyInClass: Setting[Boolean] = BooleanSetting("-Yemit-tasty-in-class", "Generate tasty in the .class file and add an empty *.hasTasty file.")

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

@@ -42,6 +42,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
 
   /** If true, tweak output so it is the same before and after pickling */
   protected def homogenizedView: Boolean = ctx.settings.YtestPickler.value
+  protected def debugPos: Boolean = ctx.settings.YdebugPos.value
 
   def homogenize(tp: Type): Type =
     if (homogenizedView)

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

@@ -604,7 +604,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     if (!suppressPositions) {
       if (printPos) {
         val posStr =
-          if (homogenizedView)
+          if (homogenizedView || debugPos)
             if (tree.isInstanceOf[MemberDef]) Str(s"${tree.source}${tree.span}")
             else Str(s"${tree.source}${tree.span.toSynthetic}")
           else