generated at
Cofree
from Freeモナド
Cofree
https://pursuit.purescript.org/packages/purescript-free/4.0.0/docs/Control.Comonad.Cofree
https://www.youtube.com/watch?v=klpKIs84_bU
http://comonad.com/reader/2008/the-cofree-comonad-and-the-expression-problem/
https://stackoverflow.com/questions/38816993/what-are-some-motivating-examples-for-cofree-comonad-in-haskell
https://iokasimov.github.io/posts/2018/05/cofree-will-tear-us-apart
https://www.reddit.com/r/haskell/comments/4x22f9/labelling_ast_nodes_with_locations/d6ce74g/
Fix型と関連があるらしい ref

Cofree型