Use null-aware operators to clean up the code

pkg/analyzer/lib/src/task/strong/info.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.
 
 /// Defines static information collected by the type checker and used later by
 /// emitters to generate code.
 // TODO(jmesserly): this was ported from package:dev_compiler, and needs to be
 // refactored to fit into analyzer.
 library analyzer.src.task.strong.info;
 
@@ skipping 194 matching lines @@
       : super(rules, expression);
   DartType get convertedType => DynamicTypeImpl.instance;
   String get message => '{0} requires dynamic invoke';
 
   @override
   String get name => 'STRONG_MODE_DYNAMIC_INVOKE';
 
   toErrorCode() => new HintCode(name, message);
 
   /// Whether this [node] is the target of a dynamic operation.
-  static bool get(AstNode node) {
-    var value = node.getProperty(_propertyName);
-    return value != null ? value : false;
-  }
+  static bool get(AstNode node) => node.getProperty(_propertyName) ?? false;
 
   /// Sets whether this node is the target of a dynamic operation.
   static bool set(AstNode node, bool value) {
     // Free the storage for things that aren't dynamic.
     if (value == false) value = null;
     node.setProperty(_propertyName, value);
     return value;
   }
 }
 
@@ skipping 312 matching lines @@
         super(expression);
 
   @override
   List<Object> get arguments => [node, baseType, expectedType];
   @override
   String get message => 'Type check failed: {0} ({1}) is not of type {2}';
 
   @override
   String get name => 'STRONG_MODE_STATIC_TYPE_ERROR';
 }