Implement subtype for type variables.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // Copyright (c) 2012, 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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(Node node);
@@ skipping 2767 matching lines @@
       TypeVariableElement variableElement = typeVariable.element;
       if (typeNode.bound != null) {
         DartType boundType = typeResolver.resolveTypeAnnotation(
             typeNode.bound, scope, element, onFailure: warning);
         if (boundType != null && boundType.element == variableElement) {
           // TODO(johnniwinther): Check for more general cycles, like
           // [: <A extends B, B extends C, C extends B> :].
           warning(node, MessageKind.CYCLIC_TYPE_VARIABLE,
                   {'typeVariableName': variableElement.name});
         } else if (boundType != null) {
-          variableElement.bound = boundType;
+          variableElement.upperBound = boundType;
         } else {
           // TODO(johnniwinther): Should be an erroneous type.
-          variableElement.bound = compiler.objectClass.computeType(compiler);
+          variableElement.upperBound = compiler.objectClass.computeType(compiler);
         }
       } else {
-        variableElement.bound = compiler.objectClass.computeType(compiler);
+        variableElement.upperBound = compiler.objectClass.computeType(compiler);
       }
       nodeLink = nodeLink.tail;
       typeLink = typeLink.tail;
     }
     assert(typeLink.isEmpty);
   }
 }
 
 class TypedefResolverVisitor extends TypeDefinitionVisitor {
   TypedefElement get element => super.element;
@@ skipping 819 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }