anchor.diff:  
   (defun create-plugin-state (compiler)
     (let* [(logger (.> compiler :log))
  +         (variables (.> compiler :variables))
            (warnings (.> compiler :warnings))
            (optimise (.> compiler :optimise))
   
  
positive.code:       :visit-nodes    visitor/visit-list
        :traverse-nodes traverse/traverse-node
        :traverse-nodes traverse/traverse-list
        :symbol->var    (lambda (x) (.> x :var))
        :var->symbol    nodes/make-symbol
        :builtin?       nodes/builtin?
        :constant?      nodes/constant?
  
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
  