Abstract over the type system.

pkg/analyzer/lib/src/context/context.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.src.context.context;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
@@ skipping 143 matching lines @@
    */
   HashMap<Source, ChangeNoticeImpl> _pendingNotices =
       new HashMap<Source, ChangeNoticeImpl>();
 
   /**
    * The [TypeProvider] for this context, `null` if not yet created.
    */
   TypeProvider _typeProvider;
 
   /**
+   * The [TypeSystem] for this context, `null` if not yet created.
+   */
+  TypeSystem _typeSystem;
+
+  /**
    * The controller for sending [SourcesChangedEvent]s.
    */
   StreamController<SourcesChangedEvent> _onSourcesChangedController;
 
   /**
    * A subscription for a stream of events indicating when files are (and are
    * not) being implicitly analyzed.
    */
   StreamController<ImplicitAnalysisEvent> _implicitAnalysisEventsController;
 
@@ skipping 298 matching lines @@
   }
 
   /**
    * Sets the [TypeProvider] for this context.
    */
   void set typeProvider(TypeProvider typeProvider) {
     _typeProvider = typeProvider;
   }
 
   @override
+  TypeSystem get typeSystem {
+    if (_typeSystem == null) {
+      _typeSystem = new TypeSystemImpl(typeProvider);
+    }
+    return _typeSystem;
+  }
+
+  @override
   void addListener(AnalysisListener listener) {
     if (!_listeners.contains(listener)) {
       _listeners.add(listener);
     }
   }
 
   @override
   void applyAnalysisDelta(AnalysisDelta delta) {
     ChangeSet changeSet = new ChangeSet();
     delta.analysisLevels.forEach((Source source, AnalysisLevel level) {
@@ skipping 1602 matching lines @@
         new PendingFuture<T>(_context, target, computeValue);
     if (!pendingFuture.evaluate(entry)) {
       _context._pendingFutureTargets
           .putIfAbsent(target, () => <PendingFuture>[])
           .add(pendingFuture);
       scheduleComputation();
     }
     return pendingFuture.future;
   }
 }