Fixed parse error with @unchecked

Dotty currently cannot parse @unchecked annotations in pattern types. That's why the previous commit failed. We need to come back to this and fix it. For the moment, to make on the current branch, the annotation is removed.

Author: odersky

src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -429,7 +429,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
 
     def search(from: Any): List[Tree] = ctx.debugTraceIndented(s"search(${show(from)})") {
       from match {
-        case tree: Tree @ unchecked =>
+        case tree: Tree => // Dotty problem: cannot write Tree @ unchecked, this currently gives a syntax error
           if (definedSym(tree) == sym) tree :: Nil
           else if (tree.envelope.contains(sym.pos)) {
             val p = search(tree.productIterator)