Introduce constraints of deferred constants.

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 get currentElement;
   Setlet<Node> get superUses;
 
@@ skipping 4623 matching lines @@
     } else {
       internalError(node.receiver, 'unexpected element $element');
     }
     return element;
   }
 
   Element visitIdentifier(Identifier node) {
     String name = node.source;
     Element element = resolver.reportLookupErrorIfAny(
         lookupInScope(compiler, node, resolver.scope, name), node, name);
+    resolver.useElement(node, element);
     // TODO(johnniwinther): Change errors to warnings, cf. 11.11.1.
     if (element == null) {
       return failOrReturnErroneousElement(resolver.enclosingElement, node, name,
                                           MessageKind.CANNOT_RESOLVE,
                                           {'name': name});
     } else if (element.isErroneous()) {
       return element;
     } else if (element.isTypedef()) {
       error(node, MessageKind.CANNOT_INSTANTIATE_TYPEDEF,
             {'typedefName': name});
@@ skipping 12 matching lines @@
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }
 
 /// Looks up [name] in [scope] and unwraps the result.
 Element lookupInScope(Compiler compiler, Node node,
                       Scope scope, String name) {
   return Elements.unwrap(scope.lookup(name), compiler, node);
 }