Fix tests

Author: odersky

compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala

@@ -112,7 +112,7 @@ class CommentPicklingTest {
       val trees = files.flatMap { f =>
         val unpickler = new DottyUnpickler(f.bytes().toArray)
         unpickler.enter(roots = Set.empty)
-        unpickler.trees(ctx)
+        unpickler.rootTrees(ctx)
       }
       fn(trees, ctx)
     }

language-server/src/dotty/tools/languageserver/DottyLanguageServer.scala

@@ -262,7 +262,7 @@ class DottyLanguageServer extends LanguageServer
             && funSym.owner.is(CaseClass)) {
             funSym.owner.info.member(name).symbol
           } else {
-            val classTree = funSym.topLevelClass.asClass.tree
+            val classTree = funSym.topLevelClass.asClass.rootTree
             tpd.defPath(funSym, classTree).lastOption.flatMap {
               case DefDef(_, _, paramss, _, _) =>
                 paramss.flatten.find(_.name == name).map(_.symbol)