Disallow assigning null to non-nullable variables

pkg/analyzer/lib/src/task/dart.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.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 6251 matching lines @@
     RecordingErrorListener errorListener = new RecordingErrorListener();
     //
     // Prepare inputs.
     //
     TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
     CompilationUnit unit = getRequiredInput(UNIT_INPUT);
     AnalysisOptionsImpl options = context.analysisOptions;
     if (options.strongMode) {
       CodeChecker checker = new CodeChecker(
           typeProvider,
-          new StrongTypeSystemImpl(implicitCasts: options.implicitCasts),
+          new StrongTypeSystemImpl(
+              implicitCasts: options.implicitCasts,
+              nonnullableTypes: options.nonnullableTypes),
           errorListener,
           options);
       checker.visitCompilationUnit(unit);
     }
     //
     // Record outputs.
     //
     outputs[STRONG_MODE_ERRORS] = getUniqueErrors(errorListener.errors);
     outputs[CREATED_RESOLVED_UNIT] = true;
     outputs[RESOLVED_UNIT] = unit;
@@ skipping 293 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }