Change some toString occurrences on Name to mangledString

These were caught when turning the backend check on.

Author: odersky

compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala

@@ -220,7 +220,7 @@ class SymbolLoaders {
       if (!sourceModule.isCompleted)
         sourceModule.completer.complete(sourceModule)
 
-      val packageName = if (root.isEffectiveRoot) "" else root.fullName.toString
+      val packageName = if (root.isEffectiveRoot) "" else root.fullName.mangledString
 
       enterFlatClasses = Some { ctx =>
         enterFlatClasses = None

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -677,7 +677,7 @@ class ClassfileParser(
     for (entry <- innerClasses.values) {
       // create a new class member for immediate inner classes
       if (entry.outerName == currentClassName) {
-        val file = ctx.platform.classPath.findClassFile(entry.externalName.toString) getOrElse {
+        val file = ctx.platform.classPath.findClassFile(entry.externalName.mangledString) getOrElse {
           throw new AssertionError(entry.externalName)
         }
         enterClassAndModule(entry, file, entry.jflags)

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -63,7 +63,7 @@ class TreeChecker extends Phase with SymTransformer {
   val NoSuperClass = Trait | Package
 
   def testDuplicate(sym: Symbol, registry: mutable.Map[String, Symbol], typ: String)(implicit ctx: Context) = {
-    val name = sym.fullName.toString
+    val name = sym.fullName.mangledString
     if (this.flatClasses && registry.contains(name))
         printError(s"$typ defined twice $sym ${sym.id} ${registry(name).id}")
     registry(name) = sym