Report errors and warnings for hiding elements, issue 572.

compiler/java/com/google/dart/compiler/resolver/Scope.java

Index: compiler/java/com/google/dart/compiler/resolver/Scope.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/Scope.java b/compiler/java/com/google/dart/compiler/resolver/Scope.java
index aa82908693889083d9ac596738eec8b26d84becf..7175766ef2ae035ccae399585b40a5647a12e0cb 100644
--- a/compiler/java/com/google/dart/compiler/resolver/Scope.java
+++ b/compiler/java/com/google/dart/compiler/resolver/Scope.java
@@ -51,7 +51,7 @@ public class Scope {
     // or we are ignoring libraries (i.e., fromLibrary == null).
     if (fromLibrary == null
         || !DartIdentifier.isPrivateName(name)
-        || library.equals(fromLibrary)) {
+        || fromLibrary.equals(library)) {
       element = findLocalElement(name);
     }
     if (element == null) {