anchor.diff:        :visit-nodes    visitor/visit-list
         :traverse-nodes traverse/traverse-node
         :traverse-nodes traverse/traverse-list
  -      :symbol->var    (lambda (x) (.> x :var))
  +      :symbol->var    (lambda (x)
  +                        (with (var (.> x :var))
  +                          (if (string? var) (.> variables var) var)))
         :var->symbol    nodes/make-symbol
         :builtin?       nodes/builtin?
         :constant?      nodes/constant?
  
positive.code: 
  (defun create-plugin-state (compiler)
    (let* [(logger (.> compiler :log))
           (warnings (.> compiler :warnings))
           (optimise (.> compiler :optimise))
  
  
negative.code:          (emit       '())]
      (const-struct
        ;; backend.lisp
        :add-categoriser!    (lambda () (fail! "add-categoriser! is not yet implemented")) ;; TODO: Add add-categoriser!
        :categorise-node     categories/visit-node
        :categorise-nodes    categories/visit-nodes
        :cat                 categories/cat
  