anchor.diff:            (setf end-found t)
             (return))))
       (if end-found
  -        (completion-suggestions-for-tokens tokens cursor-point)
  +        (completion-suggestions-for-tokens tokens (vector-pop tokens) cursor-point)
           (completion-suggestions-for-start-of-new-token tokens))))
  
positive.code: (defvar *empty-iterator*
    (make-iterator ()
      (stop)))
  
  (defun completion-suggestions-for-tokens (tokens cursor-point)
    (declare (ignore tokens cursor-point))
    *empty-iterator*)
  
  (defun iterator-without-duplicates (iter)
    (let ((seen-values (fset:empty-set)))
  
negative.code:       (vector-push-extend error all-errors))
      (setf error (make-instance 'shcl/core/parser:choice :errors all-errors))
      (iterator-without-duplicates
       (expected-types-for-parse-error error sigil-token))))
  
  (defun completion-suggestions-for-start-of-new-token-with-valid-token-types (valid-token-types)
    (iterator-without-duplicates
     (concatenate-iterators
      (map-iterator valid-token-types 'simple-expansions-for-type))))
  
  (defun completion-suggestions-for-start-of-new-token (leading-tokens)
    (completion-suggestions-for-start-of-new-token-with-valid-token-types
     (valid-types-for-next-token leading-tokens)))
  
  (defun completion-suggestions-for-tokens (leading-tokens token-to-complete cursor-point)
    (declare (ignore cursor-point))
    (let* ((token-to-complete-value (shcl/core/lexer:token-value token-to-complete))
           (valid-next-token-types (valid-types-for-next-token leading-tokens))
           (new-token-suggestions
            (completion-suggestions-for-start-of-new-token-with-valid-token-types
             valid-next-token-types))
           (applicable-new-token-suggestions
            (filter-iterator
             new-token-suggestions
             (lambda (suggestion)
               (and
                (<= (length token-to-complete-value) (length suggestion))
                (string= suggestion token-to-complete-value
                         :end1 (min (length suggestion)
                                    (length token-to-complete-value))))))))
      applicable-new-token-suggestions))
  
  (defun completion-suggestions-for-input (input-text cursor-point readtable)
    "Compute possible completions.
  