Add *IndexSetIfNull methods to SemanticSendVisitor.

pkg/compiler/lib/src/resolution/semantic_visitor.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;
 
 import '../common.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
 import '../tree/tree.dart';
@@ skipping 3163 matching lines @@
   ///     m(rhs) => dynamic += rhs;
   ///
   R visitDynamicTypeLiteralCompound(
       Send node,
       ConstantExpression constant,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
   /// Compound index assignment of [rhs] with [operator] to [index] on the
-  /// index operators of [receiver] whose getter and setter are defined by
-  /// [getterSelector] and [setterSelector], respectively.
+  /// index operators of [receiver].
   ///
   /// For instance:
   ///
   ///     m(receiver, index, rhs) => receiver[index] += rhs;
   ///
   R visitCompoundIndexSet(
       SendSet node,
       Node receiver,
       Node index,
       AssignmentOperator operator,
@@ skipping 16 matching lines @@
   R visitSuperCompoundIndexSet(
       SendSet node,
       MethodElement getter,
       MethodElement setter,
       Node index,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
   /// Compound index assignment of [rhs] with [operator] to [index] on a super
-  /// super class where the index getter is undefined and the index setter is
-  /// defined by [setter].
+  /// class where the index getter is undefined and the index setter is defined
+  /// by [setter].
   ///
   /// For instance:
   ///
   ///     class B {
   ///     }
   ///     class C extends B {
   ///       m() => super[1] += 42;
   ///     }
   ///
   R visitUnresolvedSuperGetterCompoundIndexSet(
       Send node,
       Element element,
       MethodElement setter,
       Node index,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
   /// Compound index assignment of [rhs] with [operator] to [index] on a super
-  /// super class where the index getter is defined by [getter] but the index
-  /// setter is undefined.
+  /// class where the index getter is defined by [getter] but the index setter
+  /// is undefined.
   ///
   /// For instance:
   ///
   ///     class B {
   ///       operator [](index) => 42;
   ///     }
   ///     class C extends B {
   ///       m() => super[1] += 42;
   ///     }
   ///
   R visitUnresolvedSuperSetterCompoundIndexSet(
       Send node,
       MethodElement getter,
       Element element,
       Node index,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
   /// Compound index assignment of [rhs] with [operator] to [index] on a super
-  /// super class where the index getter and setter are undefined.
+  /// class where the index getter and setter are undefined.
   ///
   /// For instance:
   ///
   ///     class B {
   ///     }
   ///     class C extends B {
   ///       m() => super[1] += 42;
   ///     }
   ///
   R visitUnresolvedSuperCompoundIndexSet(
       Send node,
       Element element,
       Node index,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
+  /// If-null assignment expression of [rhs] to [index] on the index operators
+  /// of [receiver].
+  ///
+  /// For instance:
+  ///
+  ///     m(receiver, index, rhs) => receiver[index] ??= rhs;
+  ///
+  R visitIndexSetIfNull(
+      SendSet node,
+      Node receiver,
+      Node index,
+      Node rhs,
+      A arg);
+
+  /// If-null assignment expression of [rhs] to [index] on the index operators
+  /// of a super class defined by [getter] and [setter].
+  ///
+  /// For instance:
+  ///
+  ///     class B {
+  ///       operator [](index) {}
+  ///       operator [](index, value) {}
+  ///     }
+  ///     class C extends B {
+  ///       m(index, rhs) => super[index] ??= rhs;
+  ///     }
+  ///
+  R visitSuperIndexSetIfNull(
+      SendSet node,
+      MethodElement getter,
+      MethodElement setter,
+      Node index,
+      Node rhs,
+      A arg);
+
+  /// If-null assignment expression of [rhs] to [index] on a super class where
+  /// the index getter is undefined and the index setter is defined by [setter].
+  ///
+  /// For instance:
+  ///
+  ///     class B {
+  ///       operator [](index, value) {}
+  ///     }
+  ///     class C extends B {
+  ///       m() => super[1] ??= 42;
+  ///     }
+  ///
+  R visitUnresolvedSuperGetterIndexSetIfNull(
+      Send node,
+      Element element,
+      MethodElement setter,
+      Node index,
+      Node rhs,
+      A arg);
+
+  /// If-null assignment expression of [rhs] to [index] on a super class where
+  /// the index getter is defined by [getter] but the index setter is undefined.
+  ///
+  /// For instance:
+  ///
+  ///     class B {
+  ///       operator [](index) => 42;
+  ///     }
+  ///     class C extends B {
+  ///       m() => super[1] ??= 42;
+  ///     }
+  ///
+  R visitUnresolvedSuperSetterIndexSetIfNull(
+      Send node,
+      MethodElement getter,
+      Element element,
+      Node index,
+      Node rhs,
+      A arg);
+
+  /// If-null assignment expression of [rhs] to [index] on a super class where
+  /// the index getter and setter are undefined.
+  ///
+  /// For instance:
+  ///
+  ///     class B {
+  ///     }
+  ///     class C extends B {
+  ///       m() => super[1] ??= 42;
+  ///     }
+  ///
+  R visitUnresolvedSuperIndexSetIfNull(
+      Send node,
+      Element element,
+      Node index,
+      Node rhs,
+      A arg);
+
   /// Prefix expression with [operator] of the property on [receiver] whose
   /// getter and setter are defined by [getterSelector] and [setterSelector],
   /// respectively.
   ///
   /// For instance:
   ///
   ///     m(receiver) => ++receiver.foo;
   ///
   R visitDynamicPropertyPrefix(
       Send node,
@@ skipping 1787 matching lines @@
   ///
   ///     m() => p += 42;
   ///
   R errorInvalidCompound(
       Send node,
       ErroneousElement error,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
+  /// If-null assignment expression of [rhs] to [index] on the index operators
+  /// of an invalid expression.
+  ///
+  /// For instance:
+  ///
+  ///     import 'foo.dart' as p;
+  ///
+  ///     m(index, rhs) => p[index] ??= rhs;
+  ///
+  R errorInvalidIndexSetIfNull(
+      SendSet node,
+      ErroneousElement error,
+      Node index,
+      Node rhs,
+      A arg);
+
   /// Unary operation with [operator] on an invalid expression.
   ///
   /// For instance:
   ///
   ///     class C {
   ///       static m() => ~super;
   ///     }
   ///
   R errorInvalidUnary(
       Send node,
@@ skipping 736 matching lines @@
   ///       C() : this._(42);
   ///     }
   ///
   R errorUnresolvedThisConstructorInvoke(
       Send node,
       Element element,
       NodeList arguments,
       Selector selector,
       A arg);
 }