Introduce Substitution class and Supertype class.

lib/binary/ast_to_binary.dart

 // Copyright (c) 2016, 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 kernel.ast_to_binary;
 
 import '../ast.dart';
 import '../import_table.dart';
 import 'tag.dart';
 import 'dart:convert';
 import 'dart:typed_data';
@@ skipping 852 matching lines @@
     if (node.typeArguments.isEmpty) {
       writeByte(Tag.SimpleInterfaceType);
       writeClassReference(node.classNode);
     } else {
       writeByte(Tag.InterfaceType);
       writeClassReference(node.classNode);
       writeNodeList(node.typeArguments);
     }
   }
 
+  visitSupertype(Supertype node) {
+    if (node.typeArguments.isEmpty) {
+      writeByte(Tag.SimpleInterfaceType);
+      writeClassReference(node.classNode);
+    } else {
+      writeByte(Tag.InterfaceType);
+      writeClassReference(node.classNode);
+      writeNodeList(node.typeArguments);
+    }
+  }
+
   visitFunctionType(FunctionType node) {
     if (node.requiredParameterCount == node.positionalParameters.length &&
         node.typeParameters.isEmpty &&
         node.namedParameters.isEmpty) {
       writeByte(Tag.SimpleFunctionType);
       writeNodeList(node.positionalParameters);
       writeNode(node.returnType);
     } else {
       writeByte(Tag.FunctionType);
       _typeParameterIndexer.push(node.typeParameters);
@@ skipping 356 matching lines @@
   void flush() {
     _sink.add(_buffer.sublist(0, length));
     _buffer = new Uint8List(SIZE);
     length = 0;
   }
 
   void flushAndDestroy() {
     _sink.add(_buffer.sublist(0, length));
   }
 }