Report error if the same uri appears in multiple summaries.

pkg/analyzer_cli/lib/src/build_mode.dart

 // Copyright (c) 2015, 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.
 
 library analyzer_cli.src.build_mode;
 
 import 'dart:core';
 import 'dart:io' as io;
 
 import 'package:analyzer/dart/ast/ast.dart' show CompilationUnit;
@@ skipping 151 matching lines @@
     // BuildMode expects sourceFiles in the format "<uri>|<filepath>",
     // but the rest of the code base does not understand this format.
     // Rewrite sourceFiles, stripping the "<uri>|" prefix, so that it
     // does not cause problems with code that does not expect this format.
     options.rewriteSourceFiles(options.sourceFiles
         .map((String uriPipePath) =>
             uriPipePath.substring(uriPipePath.indexOf('|') + 1))
         .toList());
 
     // Prepare the analysis context.
-    _createContext();
+    try {
+      _createContext();
+    } on ConflictingSummaryException catch (e) {
+      errorSink.writeln('$e');
+      io.exitCode = ErrorSeverity.ERROR.ordinal;
+      return ErrorSeverity.ERROR;
+    }
 
     // Add sources.
     ChangeSet changeSet = new ChangeSet();
     for (Uri uri in uriToFileMap.keys) {
       File file = uriToFileMap[uri];
       if (!file.exists) {
         errorSink.writeln('File not found: ${file.path}');
         io.exitCode = ErrorSeverity.ERROR.ordinal;
         return ErrorSeverity.ERROR;
       }
@@ skipping 237 matching lines @@
    * Build the inverse mapping of [uriToSourceMap].
    */
   static Map<String, Uri> _computePathToUriMap(Map<Uri, File> uriToSourceMap) {
     Map<String, Uri> pathToUriMap = <String, Uri>{};
     uriToSourceMap.forEach((Uri uri, File file) {
       pathToUriMap[file.path] = uri;
     });
     return pathToUriMap;
   }
 }