Disallow assigning null to non-nullable variables

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 274 matching lines @@
         this._options.preserveComments != options.preserveComments ||
         this._options.strongMode != options.strongMode ||
         this._options.enableAssertMessage != options.enableAssertMessage ||
         ((options is AnalysisOptionsImpl)
             ? this._options.strongModeHints != options.strongModeHints
             : false) ||
         ((options is AnalysisOptionsImpl)
             ? this._options.implicitCasts != options.implicitCasts
             : false) ||
         ((options is AnalysisOptionsImpl)
+            ? this._options.nonnullableTypes != options.nonnullableTypes
+            : false) ||
+        ((options is AnalysisOptionsImpl)
             ? this._options.implicitDynamic != options.implicitDynamic
             : false) ||
         this._options.enableStrictCallChecks !=
             options.enableStrictCallChecks ||
         this._options.enableGenericMethods != options.enableGenericMethods ||
         this._options.enableAsync != options.enableAsync ||
         this._options.enableSuperMixins != options.enableSuperMixins;
     int cacheSize = options.cacheSize;
     if (this._options.cacheSize != cacheSize) {
       this._options.cacheSize = cacheSize;
@@ skipping 14 matching lines @@
     this._options.incrementalApi = options.incrementalApi;
     this._options.incrementalValidation = options.incrementalValidation;
     this._options.lint = options.lint;
     this._options.preserveComments = options.preserveComments;
     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) {
       for (WorkManager workManager in workManagers) {
         workManager.onAnalysisOptionsChanged();
       }
     }
   }
 
   @override
@@ skipping 1962 matching lines @@
     }
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new IllegalArgumentException(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }