Add visitor methods specific to ??= to SemanticSendVisitor.

tests/compiler/dart2js/semantic_visitor_test.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 dart2js.semantics_visitor_test;
 
 import 'dart:async';
 import 'dart:mirrors';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
@@ skipping 164 matching lines @@
       sb.writeln(codeByPrefix);
     }
     return sb.toString();
   }
 }
 
 const List<VisitKind> UNTESTABLE_KINDS = const <VisitKind>[
   // A final field shadowing a non-final field is currently not supported in
   // resolution.
   VisitKind.VISIT_SUPER_FIELD_FIELD_COMPOUND,
+  VisitKind.VISIT_SUPER_FIELD_FIELD_SET_IF_NULL,
   VisitKind.VISIT_SUPER_FIELD_FIELD_PREFIX,
   VisitKind.VISIT_SUPER_FIELD_FIELD_POSTFIX,
   // Combination of method and setter with the same name is currently not
   // supported by the element model.
   VisitKind.VISIT_STATIC_METHOD_SETTER_COMPOUND,
+  VisitKind.VISIT_STATIC_METHOD_SETTER_SET_IF_NULL,
   VisitKind.VISIT_STATIC_METHOD_SETTER_PREFIX,
   VisitKind.VISIT_STATIC_METHOD_SETTER_POSTFIX,
   VisitKind.VISIT_TOP_LEVEL_METHOD_SETTER_COMPOUND,
+  VisitKind.VISIT_TOP_LEVEL_METHOD_SETTER_SET_IF_NULL,
   VisitKind.VISIT_TOP_LEVEL_METHOD_SETTER_PREFIX,
   VisitKind.VISIT_TOP_LEVEL_METHOD_SETTER_POSTFIX,
   VisitKind.VISIT_SUPER_METHOD_SETTER_COMPOUND,
+  VisitKind.VISIT_SUPER_METHOD_SETTER_SET_IF_NULL,
   VisitKind.VISIT_SUPER_METHOD_SETTER_PREFIX,
   VisitKind.VISIT_SUPER_METHOD_SETTER_POSTFIX,
   // The only undefined unary, `+`, is currently handled and skipped in the
   // parser.
   VisitKind.ERROR_UNDEFINED_UNARY_EXPRESSION,
   // Constant expression are currently not computed during resolution.
   VisitKind.VISIT_CONSTANT_GET,
   VisitKind.VISIT_CONSTANT_INVOKE,
 ];
 
@@ skipping 158 matching lines @@
   internalError(Spannable spannable, String message) {
     throw new SpannableAssertionFailure(spannable, message);
   }
 }
 
 enum VisitKind {
   VISIT_PARAMETER_GET,
   VISIT_PARAMETER_SET,
   VISIT_PARAMETER_INVOKE,
   VISIT_PARAMETER_COMPOUND,
+  VISIT_PARAMETER_SET_IF_NULL,
   VISIT_PARAMETER_PREFIX,
   VISIT_PARAMETER_POSTFIX,
   VISIT_FINAL_PARAMETER_SET,
   VISIT_FINAL_PARAMETER_COMPOUND,
+  VISIT_FINAL_PARAMETER_SET_IF_NULL,
   VISIT_FINAL_PARAMETER_PREFIX,
   VISIT_FINAL_PARAMETER_POSTFIX,
 
   VISIT_LOCAL_VARIABLE_GET,
   VISIT_LOCAL_VARIABLE_SET,
   VISIT_LOCAL_VARIABLE_INVOKE,
   VISIT_LOCAL_VARIABLE_COMPOUND,
+  VISIT_LOCAL_VARIABLE_SET_IF_NULL,
   VISIT_LOCAL_VARIABLE_PREFIX,
   VISIT_LOCAL_VARIABLE_POSTFIX,
   VISIT_LOCAL_VARIABLE_DECL,
   VISIT_LOCAL_CONSTANT_DECL,
   VISIT_FINAL_LOCAL_VARIABLE_SET,
   VISIT_FINAL_LOCAL_VARIABLE_COMPOUND,
+  VISIT_FINAL_LOCAL_VARIABLE_SET_IF_NULL,
   VISIT_FINAL_LOCAL_VARIABLE_PREFIX,
   VISIT_FINAL_LOCAL_VARIABLE_POSTFIX,
 
   VISIT_LOCAL_FUNCTION_GET,
   VISIT_LOCAL_FUNCTION_INVOKE,
   VISIT_LOCAL_FUNCTION_INCOMPATIBLE_INVOKE,
   VISIT_LOCAL_FUNCTION_DECL,
   VISIT_CLOSURE_DECL,
   VISIT_LOCAL_FUNCTION_SET,
   VISIT_LOCAL_FUNCTION_COMPOUND,
+  VISIT_LOCAL_FUNCTION_SET_IF_NULL,
   VISIT_LOCAL_FUNCTION_PREFIX,
   VISIT_LOCAL_FUNCTION_POSTFIX,
 
   VISIT_STATIC_FIELD_GET,
   VISIT_STATIC_FIELD_SET,
   VISIT_STATIC_FIELD_INVOKE,
   VISIT_STATIC_FIELD_COMPOUND,
+  VISIT_STATIC_FIELD_SET_IF_NULL,
   VISIT_STATIC_FIELD_PREFIX,
   VISIT_STATIC_FIELD_POSTFIX,
   VISIT_STATIC_FIELD_DECL,
   VISIT_STATIC_CONSTANT_DECL,
 
   VISIT_STATIC_GETTER_GET,
   VISIT_STATIC_GETTER_SET,
   VISIT_STATIC_GETTER_INVOKE,
 
   VISIT_STATIC_SETTER_GET,
   VISIT_STATIC_SETTER_SET,
   VISIT_STATIC_SETTER_INVOKE,
 
   VISIT_STATIC_GETTER_SETTER_COMPOUND,
+  VISIT_STATIC_GETTER_SETTER_SET_IF_NULL,
   VISIT_STATIC_METHOD_SETTER_COMPOUND,
+  VISIT_STATIC_METHOD_SETTER_SET_IF_NULL,
   VISIT_STATIC_GETTER_SETTER_PREFIX,
   VISIT_STATIC_GETTER_SETTER_POSTFIX,
 
   VISIT_STATIC_GETTER_DECL,
   VISIT_STATIC_SETTER_DECL,
 
   VISIT_FINAL_STATIC_FIELD_SET,
   VISIT_STATIC_FINAL_FIELD_COMPOUND,
+  VISIT_STATIC_FINAL_FIELD_SET_IF_NULL,
   VISIT_STATIC_FINAL_FIELD_POSTFIX,
   VISIT_STATIC_FINAL_FIELD_PREFIX,
 
   VISIT_STATIC_FUNCTION_GET,
   VISIT_STATIC_FUNCTION_SET,
   VISIT_STATIC_FUNCTION_INVOKE,
   VISIT_STATIC_FUNCTION_INCOMPATIBLE_INVOKE,
   VISIT_STATIC_FUNCTION_DECL,
   VISIT_STATIC_METHOD_SETTER_PREFIX,
   VISIT_STATIC_METHOD_SETTER_POSTFIX,
 
   VISIT_UNRESOLVED_STATIC_GETTER_COMPOUND,
+  VISIT_UNRESOLVED_STATIC_GETTER_SET_IF_NULL,
   VISIT_UNRESOLVED_STATIC_SETTER_COMPOUND,
+  VISIT_UNRESOLVED_STATIC_SETTER_SET_IF_NULL,
   VISIT_STATIC_METHOD_COMPOUND,
+  VISIT_STATIC_METHOD_SET_IF_NULL,
   VISIT_UNRESOLVED_STATIC_GETTER_PREFIX,
   VISIT_UNRESOLVED_STATIC_SETTER_PREFIX,
   VISIT_STATIC_METHOD_PREFIX,
   VISIT_UNRESOLVED_STATIC_GETTER_POSTFIX,
   VISIT_UNRESOLVED_STATIC_SETTER_POSTFIX,
   VISIT_STATIC_METHOD_POSTFIX,
 
   VISIT_TOP_LEVEL_FIELD_GET,
   VISIT_TOP_LEVEL_FIELD_SET,
   VISIT_TOP_LEVEL_FIELD_INVOKE,
   VISIT_FINAL_TOP_LEVEL_FIELD_SET,
   VISIT_TOP_LEVEL_FIELD_COMPOUND,
+  VISIT_TOP_LEVEL_FIELD_SET_IF_NULL,
   VISIT_TOP_LEVEL_FIELD_PREFIX,
   VISIT_TOP_LEVEL_FIELD_POSTFIX,
   VISIT_TOP_LEVEL_FIELD_DECL,
   VISIT_TOP_LEVEL_CONSTANT_DECL,
   VISIT_TOP_LEVEL_FINAL_FIELD_COMPOUND,
+  VISIT_TOP_LEVEL_FINAL_FIELD_SET_IF_NULL,
   VISIT_TOP_LEVEL_FINAL_FIELD_POSTFIX,
   VISIT_TOP_LEVEL_FINAL_FIELD_PREFIX,
 
   VISIT_TOP_LEVEL_GETTER_GET,
   VISIT_TOP_LEVEL_GETTER_SET,
   VISIT_TOP_LEVEL_GETTER_INVOKE,
   VISIT_TOP_LEVEL_SETTER_GET,
   VISIT_TOP_LEVEL_SETTER_SET,
   VISIT_TOP_LEVEL_SETTER_INVOKE,
   VISIT_TOP_LEVEL_GETTER_SETTER_COMPOUND,
+  VISIT_TOP_LEVEL_GETTER_SETTER_SET_IF_NULL,
   VISIT_TOP_LEVEL_GETTER_SETTER_PREFIX,
   VISIT_TOP_LEVEL_GETTER_SETTER_POSTFIX,
   VISIT_TOP_LEVEL_GETTER_DECL,
   VISIT_TOP_LEVEL_SETTER_DECL,
 
   VISIT_TOP_LEVEL_FUNCTION_GET,
   VISIT_TOP_LEVEL_FUNCTION_SET,
   VISIT_TOP_LEVEL_FUNCTION_INVOKE,
   VISIT_TOP_LEVEL_FUNCTION_INCOMPATIBLE_INVOKE,
   VISIT_TOP_LEVEL_FUNCTION_DECL,
   VISIT_TOP_LEVEL_METHOD_SETTER_COMPOUND,
+  VISIT_TOP_LEVEL_METHOD_SETTER_SET_IF_NULL,
   VISIT_TOP_LEVEL_METHOD_SETTER_PREFIX,
   VISIT_TOP_LEVEL_METHOD_SETTER_POSTFIX,
 
   VISIT_UNRESOLVED_TOP_LEVEL_GETTER_COMPOUND,
+  VISIT_UNRESOLVED_TOP_LEVEL_GETTER_SET_IF_NULL,
   VISIT_UNRESOLVED_TOP_LEVEL_SETTER_COMPOUND,
+  VISIT_UNRESOLVED_TOP_LEVEL_SETTER_SET_IF_NULL,
   VISIT_TOP_LEVEL_METHOD_COMPOUND,
+  VISIT_TOP_LEVEL_METHOD_SET_IF_NULL,
   VISIT_UNRESOLVED_TOP_LEVEL_GETTER_PREFIX,
   VISIT_UNRESOLVED_TOP_LEVEL_SETTER_PREFIX,
   VISIT_TOP_LEVEL_METHOD_PREFIX,
   VISIT_UNRESOLVED_TOP_LEVEL_GETTER_POSTFIX,
   VISIT_UNRESOLVED_TOP_LEVEL_SETTER_POSTFIX,
   VISIT_TOP_LEVEL_METHOD_POSTFIX,
 
   VISIT_DYNAMIC_PROPERTY_GET,
   VISIT_DYNAMIC_PROPERTY_SET,
   VISIT_DYNAMIC_PROPERTY_INVOKE,
   VISIT_DYNAMIC_PROPERTY_COMPOUND,
+  VISIT_DYNAMIC_PROPERTY_SET_IF_NULL,
   VISIT_DYNAMIC_PROPERTY_PREFIX,
   VISIT_DYNAMIC_PROPERTY_POSTFIX,
 
   VISIT_THIS_GET,
   VISIT_THIS_INVOKE,
 
   VISIT_THIS_PROPERTY_GET,
   VISIT_THIS_PROPERTY_SET,
   VISIT_THIS_PROPERTY_INVOKE,
   VISIT_THIS_PROPERTY_COMPOUND,
+  VISIT_THIS_PROPERTY_SET_IF_NULL,
   VISIT_THIS_PROPERTY_PREFIX,
   VISIT_THIS_PROPERTY_POSTFIX,
 
   VISIT_SUPER_FIELD_GET,
   VISIT_SUPER_FIELD_SET,
   VISIT_FINAL_SUPER_FIELD_SET,
   VISIT_SUPER_FIELD_INVOKE,
   VISIT_SUPER_FIELD_COMPOUND,
+  VISIT_SUPER_FIELD_SET_IF_NULL,
   VISIT_SUPER_FIELD_PREFIX,
   VISIT_SUPER_FIELD_POSTFIX,
   VISIT_SUPER_FINAL_FIELD_COMPOUND,
+  VISIT_SUPER_FINAL_FIELD_SET_IF_NULL,
   VISIT_SUPER_FINAL_FIELD_PREFIX,
   VISIT_SUPER_FINAL_FIELD_POSTFIX,
   VISIT_SUPER_FIELD_FIELD_COMPOUND,
+  VISIT_SUPER_FIELD_FIELD_SET_IF_NULL,
   VISIT_SUPER_FIELD_FIELD_PREFIX,
   VISIT_SUPER_FIELD_FIELD_POSTFIX,
 
   VISIT_SUPER_GETTER_GET,
   VISIT_SUPER_GETTER_SET,
   VISIT_SUPER_GETTER_INVOKE,
   VISIT_SUPER_SETTER_GET,
   VISIT_SUPER_SETTER_SET,
   VISIT_SUPER_SETTER_INVOKE,
   VISIT_SUPER_GETTER_SETTER_COMPOUND,
+  VISIT_SUPER_GETTER_SETTER_SET_IF_NULL,
   VISIT_SUPER_GETTER_FIELD_COMPOUND,
+  VISIT_SUPER_GETTER_FIELD_SET_IF_NULL,
   VISIT_SUPER_FIELD_SETTER_COMPOUND,
+  VISIT_SUPER_FIELD_SETTER_SET_IF_NULL,
   VISIT_SUPER_GETTER_SETTER_PREFIX,
   VISIT_SUPER_GETTER_FIELD_PREFIX,
   VISIT_SUPER_FIELD_SETTER_PREFIX,
   VISIT_SUPER_GETTER_SETTER_POSTFIX,
   VISIT_SUPER_GETTER_FIELD_POSTFIX,
   VISIT_SUPER_FIELD_SETTER_POSTFIX,
 
   VISIT_SUPER_METHOD_GET,
   VISIT_SUPER_METHOD_SET,
   VISIT_SUPER_METHOD_INVOKE,
   VISIT_SUPER_METHOD_INCOMPATIBLE_INVOKE,
   VISIT_SUPER_METHOD_SETTER_COMPOUND,
+  VISIT_SUPER_METHOD_SETTER_SET_IF_NULL,
   VISIT_SUPER_METHOD_SETTER_PREFIX,
   VISIT_SUPER_METHOD_SETTER_POSTFIX,
   VISIT_SUPER_METHOD_COMPOUND,
+  VISIT_SUPER_METHOD_SET_IF_NULL,
   VISIT_SUPER_METHOD_PREFIX,
   VISIT_SUPER_METHOD_POSTFIX,
 
   VISIT_UNRESOLVED_GET,
   VISIT_UNRESOLVED_SET,
   VISIT_UNRESOLVED_INVOKE,
   VISIT_UNRESOLVED_SUPER_GET,
   VISIT_UNRESOLVED_SUPER_INVOKE,
 
   VISIT_BINARY,
   VISIT_INDEX,
   VISIT_EQUALS,
   VISIT_NOT_EQUALS,
   VISIT_INDEX_PREFIX,
   VISIT_INDEX_POSTFIX,
 
   VISIT_SUPER_BINARY,
   VISIT_UNRESOLVED_SUPER_BINARY,
   VISIT_SUPER_INDEX,
   VISIT_UNRESOLVED_SUPER_INDEX,
   VISIT_SUPER_EQUALS,
   VISIT_SUPER_NOT_EQUALS,
   VISIT_SUPER_INDEX_PREFIX,
   VISIT_UNRESOLVED_SUPER_GETTER_COMPOUND,
+  VISIT_UNRESOLVED_SUPER_GETTER_SET_IF_NULL,
   VISIT_UNRESOLVED_SUPER_SETTER_COMPOUND,
+  VISIT_UNRESOLVED_SUPER_SETTER_SET_IF_NULL,
   VISIT_UNRESOLVED_SUPER_GETTER_PREFIX,
   VISIT_UNRESOLVED_SUPER_SETTER_PREFIX,
   VISIT_UNRESOLVED_SUPER_INDEX_PREFIX,
   VISIT_UNRESOLVED_SUPER_GETTER_INDEX_PREFIX,
   VISIT_UNRESOLVED_SUPER_SETTER_INDEX_PREFIX,
   VISIT_SUPER_INDEX_POSTFIX,
   VISIT_UNRESOLVED_SUPER_GETTER_POSTFIX,
   VISIT_UNRESOLVED_SUPER_SETTER_POSTFIX,
   VISIT_UNRESOLVED_SUPER_INDEX_POSTFIX,
   VISIT_UNRESOLVED_SUPER_GETTER_INDEX_POSTFIX,
   VISIT_UNRESOLVED_SUPER_SETTER_INDEX_POSTFIX,
 
   VISIT_UNRESOLVED_SUPER_COMPOUND,
+  VISIT_UNRESOLVED_SUPER_SET_IF_NULL,
   VISIT_UNRESOLVED_SUPER_PREFIX,
   VISIT_UNRESOLVED_SUPER_POSTFIX,
 
   VISIT_UNARY,
   VISIT_SUPER_UNARY,
   VISIT_UNRESOLVED_SUPER_UNARY,
   VISIT_NOT,
 
   VISIT_EXPRESSION_INVOKE,
 
   VISIT_CLASS_TYPE_LITERAL_GET,
   VISIT_CLASS_TYPE_LITERAL_SET,
   VISIT_CLASS_TYPE_LITERAL_INVOKE,
   VISIT_CLASS_TYPE_LITERAL_COMPOUND,
+  VISIT_CLASS_TYPE_LITERAL_SET_IF_NULL,
   VISIT_CLASS_TYPE_LITERAL_PREFIX,
   VISIT_CLASS_TYPE_LITERAL_POSTFIX,
 
   VISIT_TYPEDEF_TYPE_LITERAL_GET,
   VISIT_TYPEDEF_TYPE_LITERAL_SET,
   VISIT_TYPEDEF_TYPE_LITERAL_INVOKE,
   VISIT_TYPEDEF_TYPE_LITERAL_COMPOUND,
+  VISIT_TYPEDEF_TYPE_LITERAL_SET_IF_NULL,
   VISIT_TYPEDEF_TYPE_LITERAL_PREFIX,
   VISIT_TYPEDEF_TYPE_LITERAL_POSTFIX,
 
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_GET,
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_SET,
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_INVOKE,
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_COMPOUND,
+  VISIT_TYPE_VARIABLE_TYPE_LITERAL_SET_IF_NULL,
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_PREFIX,
   VISIT_TYPE_VARIABLE_TYPE_LITERAL_POSTFIX,
 
   VISIT_DYNAMIC_TYPE_LITERAL_GET,
   VISIT_DYNAMIC_TYPE_LITERAL_SET,
   VISIT_DYNAMIC_TYPE_LITERAL_INVOKE,
   VISIT_DYNAMIC_TYPE_LITERAL_COMPOUND,
+  VISIT_DYNAMIC_TYPE_LITERAL_SET_IF_NULL,
   VISIT_DYNAMIC_TYPE_LITERAL_PREFIX,
   VISIT_DYNAMIC_TYPE_LITERAL_POSTFIX,
 
   VISIT_INDEX_SET,
   VISIT_COMPOUND_INDEX_SET,
   VISIT_SUPER_INDEX_SET,
   VISIT_UNRESOLVED_SUPER_INDEX_SET,
   VISIT_SUPER_COMPOUND_INDEX_SET,
   VISIT_UNRESOLVED_SUPER_COMPOUND_INDEX_SET,
   VISIT_UNRESOLVED_SUPER_GETTER_COMPOUND_INDEX_SET,
@@ skipping 41 matching lines @@
   VISIT_REDIRECTING_FACTORY_CONSTRUCTOR_DECL,
 
   VISIT_REQUIRED_PARAMETER_DECL,
   VISIT_OPTIONAL_PARAMETER_DECL,
   VISIT_NAMED_PARAMETER_DECL,
   VISIT_REQUIRED_INITIALIZING_FORMAL_DECL,
   VISIT_OPTIONAL_INITIALIZING_FORMAL_DECL,
   VISIT_NAMED_INITIALIZING_FORMAL_DECL,
 
   VISIT_UNRESOLVED_COMPOUND,
+  VISIT_UNRESOLVED_SET_IF_NULL,
   VISIT_UNRESOLVED_PREFIX,
   VISIT_UNRESOLVED_POSTFIX,
 
   VISIT_IF_NULL,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_GET,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_SET,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_INVOKE,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_COMPOUND,
+  VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_SET_IF_NULL,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_PREFIX,
   VISIT_IF_NOT_NULL_DYNAMIC_PROPERTY_POSTFIX,
 
   ERROR_INVALID_ASSERT,
   ERROR_UNDEFINED_UNARY_EXPRESSION,
   ERROR_UNDEFINED_BINARY_EXPRESSION,
   ERROR_INVALID_GET,
   ERROR_INVALID_INVOKE,
   ERROR_INVALID_SET,
   ERROR_INVALID_PREFIX,
   ERROR_INVALID_POSTFIX,
   ERROR_INVALID_COMPOUND,
+  ERROR_INVALID_SET_IF_NULL,
   ERROR_INVALID_UNARY,
   ERROR_INVALID_EQUALS,
   ERROR_INVALID_NOT_EQUALS,
   ERROR_INVALID_BINARY,
   ERROR_INVALID_INDEX,
   ERROR_INVALID_INDEX_SET,
   ERROR_INVALID_COMPOUND_INDEX_SET,
   ERROR_INVALID_INDEX_PREFIX,
   ERROR_INVALID_INDEX_POSTFIX,
 
   VISIT_CONSTANT_GET,
   VISIT_CONSTANT_INVOKE,
 
   PREVISIT_DEFERRED_ACCESS,
 }