Use untpd.TreeTraverser in namedTrees

Avoids repeated crashes when hitting a tree that exists
only in untyped form.

Author: odersky

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

@@ -167,5 +167,6 @@ object Config {
    */
   final val PendingFindMemberLimit = LogPendingFindMemberThreshold * 4
 
+  /** When in IDE, turn StaleSymbol errors into warnings instead of crashing */
   final val ignoreStaleInIDE = true
 }

compiler/src/dotty/tools/dotc/interactive/Interactive.scala

@@ -131,19 +131,20 @@ object Interactive {
     val buf = new mutable.ListBuffer[SourceTree]
 
     trees foreach { case SourceTree(topTree, source) =>
-      (new TreeTraverser {
-        override def traverse(tree: Tree)(implicit ctx: Context) = {
+      (new untpd.TreeTraverser {
+        override def traverse(tree: untpd.Tree)(implicit ctx: Context) = {
           tree match {
-            case _: Inlined =>
+            case _: untpd.Inlined =>
               // Skip inlined trees
-            case tree: NameTree
-                if tree.symbol.exists
-                && !tree.symbol.is(Synthetic)
-                && tree.pos.exists
-                && !tree.pos.isZeroExtent
-                && (includeReferences || isDefinition(tree))
-                && treePredicate(tree) =>
-              buf += SourceTree(tree, source)
+            case utree: untpd.NameTree if tree.hasType =>
+              val tree = utree.asInstanceOf[tpd.NameTree]
+              if (tree.symbol.exists
+                   && !tree.symbol.is(Synthetic)
+                   && tree.pos.exists
+                   && !tree.pos.isZeroExtent
+                   && (includeReferences || isDefinition(tree))
+                   && treePredicate(tree))
+                buf += SourceTree(tree, source)
             case _ =>
           }
           traverseChildren(tree)