Issue 5292. Unreferenced imported identifiers should not be an error

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

Index: compiler/java/com/google/dart/compiler/resolver/DuplicateElementImplementation.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/DuplicateElementImplementation.java b/compiler/java/com/google/dart/compiler/resolver/DuplicateElementImplementation.java
new file mode 100644
index 0000000000000000000000000000000000000000..3faaff36b5b3b84ede277fd7d3140fc04ef85b5e
--- /dev/null
+++ b/compiler/java/com/google/dart/compiler/resolver/DuplicateElementImplementation.java
@@ -0,0 +1,88 @@
+// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.google.dart.compiler.resolver;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+import com.google.dart.compiler.ast.DartObsoleteMetadata;
+import com.google.dart.compiler.ast.Modifiers;
+import com.google.dart.compiler.common.SourceInfo;
+import com.google.dart.compiler.type.Type;
+
+import java.util.List;
+
+class DuplicateElementImplementation implements DuplicateElement {
+  private final String name;
+  private final List<String> locations = Lists.newArrayList();
+
+  public DuplicateElementImplementation(Element oldElement, Element newElement) {
+    name = oldElement.getName();
+    locations.addAll(getLocations(oldElement));
+    locations.addAll(getLocations(newElement));
+  }
+
+  @Override
+  public String getOriginalName() {
+    return name;
+  }
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public ElementKind getKind() {
+    return ElementKind.DUPLICATE;
+  }
+
+  @Override
+  public Type getType() {
+    return null;
+  }
+
+  @Override
+  public boolean isDynamic() {
+    return false;
+  }
+
+  @Override
+  public Modifiers getModifiers() {
+    return Modifiers.NONE;
+  }
+
+  @Override
+  public DartObsoleteMetadata getMetadata() {
+    return null;
+  }
+
+  @Override
+  public EnclosingElement getEnclosingElement() {
+    return null;
+  }
+
+  @Override
+  public SourceInfo getNameLocation() {
+    return null;
+  }
+
+  @Override
+  public SourceInfo getSourceInfo() {
+    return null;
+  }
+
+  @Override
+  public List<String> getLocations() {
+    return locations;
+  }
+
+  private static List<String> getLocations(Element element) {
+    if (element instanceof DuplicateElement) {
+      return ((DuplicateElement) element).getLocations();
+    } else {
+      return ImmutableList.of(Elements.getLibraryUnitLocation(element));
+    }
+  }
+}