anchor.diff:  
   /// A function definition, consisting of parameters and a body.  The parameters
   /// include a distinguished continuation parameter.
  -class FunctionDefinition extends Node {
  +class FunctionDefinition extends Node implements InteriorNode {
     final FunctionElement element;
     final Continuation returnContinuation;
     final List<Parameter> parameters;
  -  final Expression body;
  +  Expression body;
     final List<ConstDeclaration> localConstants;
   
     /// Values for optional parameters.
  
positive.code: /// value is in scope in the body.
  /// During one-pass construction a LetVal with an empty body is used to
  /// represent one-level context 'let val x = V in []'.
  class LetPrim extends Expression {
    final Primitive primitive;
    Expression body = null;
  
  
negative.code: ///
  ///   let rec [variable] = [definition] in [body]
  ///
  class DeclareFunction extends Expression implements InteriorNode {
    final Local variable;
    final FunctionDefinition definition;
    Expression body;
  