Issue 3532. Report error if one unit included twice

compiler/javatests/com/google/dart/compiler/end2end/inc/IncrementalCompilation2Test.java

 // 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.end2end.inc;
 
 import static com.google.dart.compiler.DartCompiler.EXTENSION_DEPS;
 import static com.google.dart.compiler.DartCompiler.EXTENSION_TIMESTAMP;
 import static com.google.dart.compiler.common.ErrorExpectation.assertErrors;
 import static com.google.dart.compiler.common.ErrorExpectation.errEx;
 
@@ skipping 653 matching lines @@
     URI uri = new URI("dart:noSuchSource");
     Source source = new UrlSource(uri, new SystemLibraryManager()) {
       @Override
       public String getName() {
         return null;
       }
     };
     // should not cause exception
     assertFalse(source.exists());
   }
+  /**
+   * <p>
+   * http://code.google.com/p/dart/issues/detail?id=3532
+   */
+  public void test_includeSameUnitTwice() throws Exception {
+    appSource.setContent(
+        "A.dart",
+        makeCode(
+            "// filler filler filler filler filler filler filler filler filler filler filler",
+            ""));
+    appSource.setContent(
+        APP,
+        makeCode(
+            "// filler filler filler filler filler filler filler filler filler filler filler",
+            "#library('application');",
+            "#source('A.dart');",
+            "#source('A.dart');",
+            ""));
+    // do compile, no errors expected
+    compile();
+    assertErrors(errors, errEx(DartCompilerErrorCode.UNIT_WAS_ALREADY_INCLUDED, 4, 1, 18));
+  }
 
   /**
    * There was bug that we added <code>null</code> into {@link LibraryUnit#getImports()}. Here trick
    * is that we reference "existing" {@link Source}, which can not be read.
    * <p>
    * http://code.google.com/p/dart/issues/detail?id=2693
    */
   public void test_ignoreNullLibrary() throws Exception {
     appSource.setContent("canNotRead.dart", MemoryLibrarySource.IO_EXCEPTION_CONTENT);
     appSource.setContent(
@@ skipping 119 matching lines @@
   private void didWrite(String sourceName, String extension) {
     String spec = sourceName + "/" + extension;
     assertTrue("Expected write: " + spec, provider.writes.contains(spec));
   }
 
   private void didNotWrite(String sourceName, String extension) {
     String spec = sourceName + "/" + extension;
     assertFalse("Didn't expect write: " + spec, provider.writes.contains(spec));
   }
 }