Introduce Substitution class and Supertype class.

lib/text/ast_to_text.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_text;
 
 import '../ast.dart';
 import '../import_table.dart';
 import '../type_propagation/type_propagation.dart';
 
 class Namer<T> {
@@ skipping 401 matching lines @@
       type.accept(this);
     }
   }
 
   void writeOptionalType(DartType type) {
     if (type != null) {
       type.accept(this);
     }
   }
 
+  visitSupertype(Supertype type) {
+    if (type == null) {
+      print('<No Supertype>');
+    } else {
+      writeClassReference(type.classNode);
+      if (type.typeArguments.isNotEmpty) {
+        writeSymbol('<');
+        writeList(type.typeArguments, writeType);
+        writeSymbol('>');
+      }
+    }
+  }
+
   void writeModifier(bool isThere, String name) {
     if (isThere) {
       writeWord(name);
     }
   }
 
   void writeName(Name name) {
     if (name?.name == '') {
       writeWord(emptyNameString);
     } else {
@@ skipping 270 matching lines @@
 
   visitClass(Class node) {
     writeAnnotationList(node.annotations);
     writeIndentation();
     writeModifier(node.isAbstract, 'abstract');
     writeWord('class');
     writeWord(getClassName(node));
     writeTypeParameterList(node.typeParameters);
     if (node.isMixinApplication) {
       writeSpaced('=');
-      writeType(node.supertype);
+      visitSupertype(node.supertype);
       writeSpaced('with');
-      writeType(node.mixedInType);
+      visitSupertype(node.mixedInType);
     } else if (node.supertype != null) {
       writeSpaced('extends');
-      writeType(node.supertype);
+      visitSupertype(node.supertype);
     }
     if (node.implementedTypes.isNotEmpty) {
       writeSpaced('implements');
-      writeList(node.implementedTypes, writeType);
+      writeList(node.implementedTypes, visitSupertype);
     }
     var endLineString = ' {';
     if (node.enclosingLibrary.fileUri != node.fileUri) {
       endLineString += ' // from ${node.fileUri}';
     }
     endLine(endLineString);
     ++indentation;
     node.fields.forEach(writeNode);
     node.constructors.forEach(writeNode);
     node.procedures.forEach(writeNode);
@@ skipping 804 matching lines @@
   }
   throw 'illegal ProcedureKind: $kind';
 }
 
 class ExpressionPrinter {
   final Printer writeer;
   final int minimumPrecedence;
 
   ExpressionPrinter(this.writeer, this.minimumPrecedence);
 }