Initial support for the NNBD proposal

pkg/analyzer/lib/src/dart/ast/utilities.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.dart.ast.utilities;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 7185 matching lines @@
     return null;
   }
 
   @override
   Object visitFunctionTypedFormalParameter(FunctionTypedFormalParameter node) {
     _visitNodeListWithSeparatorAndSuffix(node.metadata, ' ', ' ');
     _visitNodeWithSuffix(node.returnType, " ");
     _visitNode(node.identifier);
     _visitNode(node.typeParameters);
     _visitNode(node.parameters);
+    if (node.question != null) {
+      _writer.print('?');
+    }
     return null;
   }
 
   @override
   Object visitHideCombinator(HideCombinator node) {
     _writer.print("hide ");
     _visitNodeListWithSeparator(node.hiddenNames, ", ");
     return null;
   }
 
@@ skipping 426 matching lines @@
     _writer.print('<');
     _visitNodeListWithSeparator(node.arguments, ", ");
     _writer.print('>');
     return null;
   }
 
   @override
   Object visitTypeName(TypeName node) {
     _visitNode(node.name);
     _visitNode(node.typeArguments);
+    if (node.question != null) {
+      _writer.print('?');
+    }
     return null;
   }
 
   @override
   Object visitTypeParameter(TypeParameter node) {
     _visitNodeListWithSeparatorAndSuffix(node.metadata, " ", " ");
     _visitNode(node.name);
     _visitNodeWithPrefix(" extends ", node.bound);
     return null;
   }
@@ skipping 166 matching lines @@
    * Safely visit the given [token], printing the [suffix] after the token if it
    * is non-`null`.
    */
   void _visitTokenWithSuffix(Token token, String suffix) {
     if (token != null) {
       _writer.print(token.lexeme);
       _writer.print(suffix);
     }
   }
 }