anchor.diff:  }
   
   class FunctionExpr extends Expression {
  -  List<FnParam> params;
  -  List<Statement> statements;
  +  final List<FnParam> params;
  +  final List<Statement> statements;
   
     FunctionExpr(this.params, this.statements, [OutputType type = null])
         : super(type);
  
positive.code: }
  
  class NotExpr extends Expression {
    Expression condition;
    NotExpr(this.condition) : super(BOOL_TYPE);
  
    dynamic visitExpression(ExpressionVisitor visitor, dynamic context) {
  
negative.code: }
  
  class ExternalExpr extends Expression {
    final CompileIdentifierMetadata value;
    final List<OutputType> typeParams;
    ExternalExpr(this.value, [OutputType type, this.typeParams]) : super(type);
  
    dynamic visitExpression(ExpressionVisitor visitor, dynamic context) {
      return visitor.visitExternalExpr(this, context);
  