Introduce Substitution class and Supertype class.

lib/binary/ast_from_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_from_binary;
 
 import '../ast.dart';
 import 'tag.dart';
 import 'loader.dart';
 import 'dart:convert';
 import 'package:kernel/transformations/flags.dart';
@@ skipping 311 matching lines @@
     int flags = readByte();
     node.isAbstract = flags & 0x1 != 0;
     node.level = _currentLibrary.isExternal
         ? (flags & 0x2 != 0) ? ClassLevel.Type : ClassLevel.Hierarchy
         : ClassLevel.Body;
     node.name = readStringOrNullIfEmpty();
     node.fileUri = readUriReference();
     node.annotations = readAnnotationList(node);
     debugPath.add(node.name ?? 'normal-class');
     readAndPushTypeParameterList(node.typeParameters, node);
-    node.supertype = readDartTypeOption();
-    _fillNonTreeNodeList(node.implementedTypes, readDartType);
+    node.supertype = readSupertypeOption();
+    _fillNonTreeNodeList(node.implementedTypes, readSupertype);
     _fillLazilyLoadedList(node.fields, (int tag, int index) {
       readField(loader.getClassMemberReference(node, tag, index), tag);
     });
     _fillLazilyLoadedList(node.constructors, (int tag, int index) {
       readConstructor(loader.getClassMemberReference(node, tag, index), tag);
     });
     _fillLazilyLoadedList(node.procedures, (int tag, int index) {
       readProcedure(loader.getClassMemberReference(node, tag, index), tag);
     });
     typeParameterStack.length = 0;
     debugPath.removeLast();
   }
 
   void readMixinClass(Class node) {
     int flags = readByte();
     node.isAbstract = flags & 0x1 != 0;
     node.level = _currentLibrary.isExternal
         ? (flags & 0x2 != 0) ? ClassLevel.Type : ClassLevel.Hierarchy
         : ClassLevel.Body;
     node.name = readStringOrNullIfEmpty();
     node.fileUri = readUriReference();
     node.annotations = readAnnotationList(node);
     debugPath.add(node.name ?? 'mixin-class');
     readAndPushTypeParameterList(node.typeParameters, node);
-    node.supertype = readDartType();
-    node.mixedInType = readDartType();
+    node.supertype = readSupertype();
+    node.mixedInType = readSupertype();
     _fillNonTreeNodeList(node.implementedTypes, readDartType);
     _fillLazilyLoadedList(node.constructors, (int tag, int index) {
       readConstructor(loader.getClassMemberReference(node, tag, index), tag);
     });
     typeParameterStack.length = 0;
     debugPath.removeLast();
   }
 
   int getAndResetTransformerFlags() {
     int flags = _transformerFlags;
@@ skipping 426 matching lines @@
     return new Catch(exception, body, guard: guard, stackTrace: stackTrace);
   }
 
   Block readBlock() {
     int stackHeight = variableStack.length;
     var body = readStatementList();
     variableStack.length = stackHeight;
     return new Block(body);
   }
 
+  Supertype readSupertype() {
+    InterfaceType type = readDartType();
+    return new Supertype(type.classNode, type.typeArguments);
+  }
+
+  Supertype readSupertypeOption() {
+    return readAndCheckOptionTag() ? readSupertype() : null;
+  }
+
+  List<Supertype> readSupertypeList() {
+    return new List<Supertype>.generate(readUInt(), (i) => readSupertype());
+  }
+
   List<DartType> readDartTypeList() {
     return new List<DartType>.generate(readUInt(), (i) => readDartType());
   }
 
   DartType readDartTypeOption() {
     return readAndCheckOptionTag() ? readDartType() : null;
   }
 
   DartType readDartType() {
     int tag = readByte();
@@ skipping 105 matching lines @@
         isFinal: flags & 0x1 != 0,
         isConst: flags & 0x2 != 0);
   }
 
   int readOffset() {
     // Offset is saved as unsigned,
     // but actually ranges from -1 and up (thus the -1)
     return readUInt() - 1;
   }
 }