Some progress towards maintaining position on annotations.

There's still something missing, which might have to be for later.
See comment in RefinedPrinter.scala.

Author: odersky

src/dotty/tools/dotc/core/tasty/PositionPickler.scala

@@ -66,7 +66,11 @@ class PositionPickler(pickler: TastyPickler, addrsInfo: AddrsInfo) {
           val posType = positionedOfIterator.next(x)
           //println(s"pickle type pos $posType")
           posType.foreachPart {
-            case t @ AnnotatedType(_, PosAnnot(pos)) => picklePos(t, pos.toSynthetic)
+            case t @ AnnotatedType(_, annot) =>
+              annot match {
+                case PosAnnot(pos) => picklePos(t, pos.toSynthetic)
+                case _ => traverse(annot.tree)
+              }
             case _ =>
           }          
         }

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

@@ -446,7 +446,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
     case _ => String.valueOf(const.value)
   }
 
-  def toText(annot: Annotation): Text = s"@${annot.symbol.name}" // for now
+  def toText(annot: Annotation): Text = s"@${annot.symbol.name}" // should be overridden in RefinedPrinter
 
   protected def escapedString(str: String): String = str flatMap escapedChar
 

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

@@ -42,6 +42,8 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     case _ => false
   }
 
+  private var printPos = ctx.settings.Yprintpos.value
+
   override protected def recursionLimitExceeded() = {}
 
   protected val PrintableFlags = (SourceModifierFlags | Label | Module | Local).toCommonFlags
@@ -156,6 +158,18 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   def blockText[T >: Untyped](trees: List[Tree[T]]): Text =
     ("{" ~ toText(trees, "\n") ~ "}").close
 
+  def constrText(tree: untpd.Tree): Text = toTextLocal(tree).stripPrefix("new ") // DD
+    
+  // Would like to override this: 
+  // But this leads to tasty position tests failing because we read some
+  // annotations wihtout positions (curiously, only annootated types in patterns
+  // seem to be a problem). A failing test is:
+  //
+  //    test/new/annot.scala
+  //
+  // override def toText(annot: Annotation): Text = 
+  //   if (annot.tree.isEmpty) annot.toString else constrText(annot.tree)
+
   override def toText[T >: Untyped](tree: Tree[T]): Text = controlled {
 
     import untpd.{modsDeco => _, _}
@@ -206,8 +220,6 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case untpd.Function(_, tpt) => " <% " ~ toText(tpt)
     }
 
-    def constrText(tree: untpd.Tree): Text = toTextLocal(tree).stripPrefix("new ") // DD
-
     def annotText(tree: untpd.Tree): Text = "@" ~ constrText(tree) // DD
 
     def useSymbol =
@@ -524,11 +536,20 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         case tp => tp
       }
       if (tree.isType) txt = toText(tp)
-      else if (!tree.isDef) txt = ("<" ~ txt ~ ":" ~ toText(tp) ~ ">").close
+      else if (!tree.isDef) {
+        val saved = printPos
+        printPos = false // disable printPos for types that are not explicitly written
+        try txt = ("<" ~ txt ~ ":" ~ toText(tp) ~ ">").close
+        finally printPos = saved
+      }
     }
-    else if (homogenizedView && tree.isType) 
+    else if (homogenizedView && tree.isType) {
       txt = toText(tree.typeOpt)
-    if (ctx.settings.Yprintpos.value && !tree.isInstanceOf[WithoutTypeOrPos[_]]) {
+      if (printPos && false)
+        txt = txt ~ "@@" ~ 
+          Text(TypePositions.refPositions(tree.asInstanceOf[tpd.Tree]).map(x => Str(x.toString)))
+    }
+    if (printPos && !tree.isInstanceOf[WithoutTypeOrPos[_]]) {
       val pos = 
         if (homogenizedView) 
           tree match {
@@ -537,7 +558,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
             case _ => tree.pos.toSynthetic // deserialized position is synthetic
           }
         else tree.pos
-      val clsStr = "" // DEBUG: if (tree.isType) tree.getClass.toString else ""
+      val clsStr = ""//#" + tree.uniqueId // DEBUG: if (tree.isType) tree.getClass.toString else ""
       txt = (txt ~ "@" ~ pos.toString ~ clsStr).close
     }
     tree match {

tests/new/annot.scala

@@ -0,0 +1,10 @@
+import annotation.unchecked.uncheckedVariance
+import annotation.unchecked.uncheckedVariance
+
+class Test[T] {
+  val x: T @uncheckedVariance = ???
+
+  def f(x: Any) = (??? : T @unchecked) match {
+    case x: T @ unchecked => ???
+  }
+}