Build new IR for functions returning a constant

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 441 matching lines @@
               element.targetConstructor);
         }
         return new TreeElementMapping(element);
       }
       if (element.isPatched) {
         checkMatchingPatchSignatures(element, element.patch);
         element = element.patch;
       }
       return compiler.withCurrentElement(element, () {
         FunctionExpression tree = element.parseNode(compiler);
+        if (!tree.hasBody()) element.setAbstract();
         if (tree.modifiers.isExternal()) {
           error(tree, MessageKind.PATCH_EXTERNAL_WITHOUT_IMPLEMENTATION);
           return null;
         }
         if (isConstructor || element.isFactoryConstructor()) {
           if (tree.returnType != null) {
             error(tree, MessageKind.CONSTRUCTOR_WITH_RETURN_TYPE);
           }
           if (element.modifiers.isConst() &&
               tree.hasBody() &&
@@ skipping 4256 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);
 }