anchor.diff:    ((%block-ast :initarg :block-ast :reader block-ast)
      (%form-ast :initarg :form-ast :reader form-ast)))
   
  -(defun make-return-from-ast (block-ast form-ast)
  +(defun make-return-from-ast (block-ast form-ast &key origin)
     (make-instance 'return-from-ast
  +    :origin origin
       :block-ast block-ast
       :form-ast form-ast))
     
  
positive.code: (defclass top-level-function-ast (function-ast)
    ((%forms :initarg :forms :reader forms)))
  
  (defun make-top-level-function-ast (body-ast lambda-list forms)
    (make-instance 'top-level-function-ast
      :body-ast body-ast
      :lambda-list lambda-list
      :forms forms))
  
negative.code: (defclass tag-ast (ast)
    ((%name :initarg :name :reader name)))
  
  (defun make-tag-ast (name &key origin)
    (make-instance 'tag-ast
      :origin origin
      :name name))
  
  (cleavir-io:define-save-info tag-ast
  