anchor.diff:  
              ;;compile-result
              :varjo-compile-result
  +           :compiled-function-result
              :glsl-code
              :stage-type
              :out-vars
  
positive.code:            :find-mutual-cast-type
             :v-special-functionp
             :v-errorp
  
             ;;type accessors
             :core-typep
  
negative.code:            :id=
             :id~=
             :flow-ids
             :flow-id-scope
  
             ;;environment
             :get-symbol-binding
             :get-base-env
             :get-primitive-type-from-context
             :argument-type
             :argument-uniform-name
             :variable-in-scope-p
             :variable-type
             :variable-uniform-name
             :variables-in-scope
             :metadata-for-argument
             :metadata-for-variable
  
             ;; ast
             :ast-node
  