Add analysis option that will be used to fix #26583

pkg/analyzer/lib/src/generated/engine.dart

 // Copyright (c) 2014, 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.generated.engine;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 1277 matching lines @@
    * used.  This flag is not exposed in the interface, and should be
    * replaced by something more general.
    */
   // TODO(leafp): replace this with something more general
   bool strongModeHints = false;
 
   @override
   bool trackCacheDependencies = true;
 
   /**
+   * A flag indicating whether implicit casts are allowed in [strongMode]
+   * (they are always allowed in Dart 1.0 mode).
+   *
+   * This option is experimental and subject to change.
+   */
+  bool implicitCasts = true;
+
+  /**
    * Initialize a newly created set of analysis options to have their default
    * values.
    */
   AnalysisOptionsImpl();
 
   /**
    * Initialize a newly created set of analysis options to have the same values
    * as those in the given set of analysis [options].
    */
   AnalysisOptionsImpl.from(AnalysisOptions options) {
@@ skipping 10 matching lines @@
     generateSdkErrors = options.generateSdkErrors;
     hint = options.hint;
     incremental = options.incremental;
     incrementalApi = options.incrementalApi;
     incrementalValidation = options.incrementalValidation;
     lint = options.lint;
     preserveComments = options.preserveComments;
     strongMode = options.strongMode;
     if (options is AnalysisOptionsImpl) {
       strongModeHints = options.strongModeHints;
+      implicitCasts = options.implicitCasts;
     }
     trackCacheDependencies = options.trackCacheDependencies;
   }
 
   bool get analyzeFunctionBodies {
     if (identical(analyzeFunctionBodiesPredicate, _analyzeAllFunctionBodies)) {
       return true;
     } else if (identical(
         analyzeFunctionBodiesPredicate, _analyzeNoFunctionBodies)) {
       return false;
@@ skipping 1237 matching lines @@
    * The data that was created from the source.
    */
   final E data;
 
   /**
    * Initialize a newly created holder to associate the given [data] with the
    * given [modificationTime].
    */
   TimestampedData(this.modificationTime, this.data);
 }