Resynthesize exports lazily.

pkg/analyzer/test/src/summary/resynthesize_test.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 test.src.serialization.elements_test;
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/constant/value.dart';
@@ skipping 92 matching lines @@
 
   void checkLibraryElements(
       LibraryElementImpl original, LibraryElementImpl resynthesized) {
     compareElements(resynthesized, original, '(library)');
     expect(resynthesized.displayName, original.displayName);
     expect(original.enclosingElement, isNull);
     expect(resynthesized.enclosingElement, isNull);
     expect(resynthesized.hasExtUri, original.hasExtUri);
     compareCompilationUnitElements(resynthesized.definingCompilationUnit,
         original.definingCompilationUnit);
-    expect(resynthesized.parts.length, original.parts.length);
+    expect(resynthesized.parts.length, original.parts.length, reason: 'parts');
     for (int i = 0; i < resynthesized.parts.length; i++) {
       compareCompilationUnitElements(resynthesized.parts[i], original.parts[i]);
     }
-    expect(resynthesized.imports.length, original.imports.length);
+    expect(resynthesized.imports.length, original.imports.length,
+        reason: 'imports');
     for (int i = 0; i < resynthesized.imports.length; i++) {
       compareImportElements(resynthesized.imports[i], original.imports[i],
           'import ${original.imports[i].uri}');
     }
-    expect(resynthesized.exports.length, original.exports.length);
+    expect(resynthesized.exports.length, original.exports.length,
+        reason: 'exports');
     for (int i = 0; i < resynthesized.exports.length; i++) {
       compareExportElements(resynthesized.exports[i], original.exports[i],
           'export ${original.exports[i].uri}');
     }
     expect(resynthesized.nameLength, original.nameLength);
     compareNamespaces(resynthesized.publicNamespace, original.publicNamespace,
         '(public namespace)');
     compareNamespaces(resynthesized.exportNamespace, original.exportNamespace,
         '(export namespace)');
     if (original.entryPoint == null) {
@@ skipping 4471 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }