Issue 27358. Reset AnalysisContext 'sourceFactory' and 'typeSystem' on analysis options change.

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/dart/ast/ast.dart';
@@ skipping 311 matching lines @@
     this._options.enableInitializingFormalAccess =
         options.enableInitializingFormalAccess;
     this._options.enableSuperMixins = options.enableSuperMixins;
     this._options.enableTiming = options.enableTiming;
     this._options.hint = options.hint;
     this._options.incremental = options.incremental;
     this._options.incrementalApi = options.incrementalApi;
     this._options.incrementalValidation = options.incrementalValidation;
     this._options.lint = options.lint;
     this._options.preserveComments = options.preserveComments;
+    if (this._options.strongMode != options.strongMode) {
+      _typeSystem = null;
+    }
     this._options.strongMode = options.strongMode;
     this._options.trackCacheDependencies = options.trackCacheDependencies;
     this._options.finerGrainedInvalidation = options.finerGrainedInvalidation;
     if (options is AnalysisOptionsImpl) {
       this._options.strongModeHints = options.strongModeHints;
       this._options.implicitCasts = options.implicitCasts;
       this._options.nonnullableTypes = options.nonnullableTypes;
       this._options.implicitDynamic = options.implicitDynamic;
     }
     if (needsRecompute) {
@@ skipping 1883 matching lines @@
     }
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new ArgumentError(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }