Add a parameter to return continuations

sdk/lib/_internal/compiler/implementation/cps_ir/cps_ir_nodes.dart

 // Copyright (c) 2013, 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.
 
 // IrNodes are kept in a separate library to have precise control over their
 // dependencies on other parts of the system.
 library dart2js.ir_nodes;
 
 import '../dart2jslib.dart' as dart2js show Constant, ConstructedConstant,
   StringConstant, ListConstant, MapConstant;
@@ skipping 475 matching lines @@
 }
 
 class Parameter extends Primitive {
   Parameter(Element element) {
     super.hint = element;
   }
 
   accept(Visitor visitor) => visitor.visitParameter(this);
 }
 
-/// Continuations are normally bound by 'let cont'.  A continuation with no
-/// parameter (or body) is used to represent a function's return continuation.
+/// Continuations are normally bound by 'let cont'.  A continuation with one
+/// parameter and no body is used to represent a function's return continuation.
 /// The return continuation is bound by the Function, not by 'let cont'.
 class Continuation extends Definition implements InteriorNode {
   final List<Parameter> parameters;
   Expression body = null;
 
   // A continuation is recursive if it has any recursive invocations.
   bool isRecursive = false;
 
   Continuation(this.parameters);
 
-  Continuation.retrn() : parameters = null;
+  Continuation.retrn() : parameters = <Parameter>[new Parameter(null)];
 
   accept(Visitor visitor) => visitor.visitContinuation(this);
 }
 
 /// A function definition, consisting of parameters and a body.  The parameters
 /// include a distinguished continuation parameter.
 class FunctionDefinition extends Node implements InteriorNode {
   final FunctionElement element;
   final Continuation returnContinuation;
   final List<Parameter> parameters;
@@ skipping 282 matching lines @@
       release(node.parameters[i]);
     }
   }
 
   void visitIsTrue(IsTrue node) {
     visitReference(node.value);
   }
 
 }