Fix issue 19424

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java
index d92d959c693c12d0ba83b05303dcee5caaf8d893..236afd9d5a85df1900472e686bd3688f79daae90 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/scope/LibraryImportScope.java
@@ -14,6 +14,7 @@
 package com.google.dart.engine.internal.scope;
 
 import com.google.dart.engine.AnalysisEngine;
+import com.google.dart.engine.ast.AstNode;
 import com.google.dart.engine.ast.Identifier;
 import com.google.dart.engine.element.Element;
 import com.google.dart.engine.element.ImportElement;
@@ -22,6 +23,7 @@ import com.google.dart.engine.error.AnalysisError;
 import com.google.dart.engine.error.AnalysisErrorListener;
 import com.google.dart.engine.error.StaticWarningCode;
 import com.google.dart.engine.internal.element.MultiplyDefinedElementImpl;
+import com.google.dart.engine.source.Source;
 import com.google.dart.engine.utilities.general.StringUtilities;
 
 import java.util.ArrayList;
@@ -76,6 +78,15 @@ public class LibraryImportScope extends Scope {
   }
 
   @Override
+  protected Source getSource(AstNode node) {
+    Source source = super.getSource(node);
+    if (source == null) {
+      source = definingLibrary.getDefiningCompilationUnit().getSource();
+    }
+    return source;
+  }
+
+  @Override
   protected Element internalLookup(Identifier identifier, String name,
       LibraryElement referencingLibrary) {
     Element foundElement = localLookup(name, referencingLibrary);