Use null-aware operators to clean up the code

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 798 matching lines @@
    * Return the logger that should receive information about errors within the
    * analysis engine.
    */
   Logger get logger => _logger;
 
   /**
    * Set the logger that should receive information about errors within the
    * analysis engine to the given [logger].
    */
   void set logger(Logger logger) {
-    this._logger = logger == null ? Logger.NULL : logger;
+    this._logger = logger ?? Logger.NULL;
   }
 
   /**
    * Return the list of plugins that clients are required to process, either by
    * creating an [ExtensionManager] or by using the method
    * [processRequiredPlugins].
    */
   List<Plugin> get requiredPlugins => <Plugin>[enginePlugin];
 
   /**
@@ skipping 363 matching lines @@
    * 37).
    */
   bool enableAssertMessage = false;
 
   /**
    * A flag indicating whether analysis is to enable async support.
    */
   bool enableAsync = true;
 
   /**
-   * A flag indicating whether interface libraries are to be supported (DEP 40).
-   */
-  bool get enableConditionalDirectives => true;
-
-  @deprecated
-  void set enableConditionalDirectives(_) {}
-
-  /**
    * A flag indicating whether generic methods are to be supported (DEP 22).
    */
   bool enableGenericMethods = false;
 
   /**
    * A flag indicating whether analysis is to strictly follow the specification
    * when generating warnings on "call" methods (fixes dartbug.com/21938).
    */
   bool enableStrictCallChecks = false;
 
@@ skipping 121 matching lines @@
   AnalyzeFunctionBodiesPredicate get analyzeFunctionBodiesPredicate =>
       _analyzeFunctionBodiesPredicate;
 
   set analyzeFunctionBodiesPredicate(AnalyzeFunctionBodiesPredicate value) {
     if (value == null) {
       throw new ArgumentError.notNull('analyzeFunctionBodiesPredicate');
     }
     _analyzeFunctionBodiesPredicate = value;
   }
 
+  /**
+   * A flag indicating whether interface libraries are to be supported (DEP 40).
+   */
+  bool get enableConditionalDirectives => true;
+
+  @deprecated
+  void set enableConditionalDirectives(_) {}
+
   @override
   int encodeCrossContextOptions() =>
       (enableAssertMessage ? ENABLE_ASSERT_FLAG : 0) |
       (enableAsync ? ENABLE_ASYNC_FLAG : 0) |
       (enableGenericMethods ? ENABLE_GENERIC_METHODS_FLAG : 0) |
       (enableStrictCallChecks ? ENABLE_STRICT_CALL_CHECKS_FLAG : 0) |
       (strongMode ? ENABLE_STRONG_MODE_FLAG : 0) |
       (strongModeHints ? ENABLE_STRONG_MODE_HINTS_FLAG : 0) |
       (enableSuperMixins ? ENABLE_SUPER_MIXINS_FLAG : 0);
 
@@ skipping 1189 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);
 }