This is about a paper published in 1991: Functional programming with bananas, lenses, envelopes and barbed wire by Erik Meijer, Maarten Fokkinga & Ross Paterson. Other references to articles and papers by Milewski , Wadler and Gibbons at 32:48 . I also came across this paper by Wadler: The Girard-Reynolds Isomorphism . I wish I had known about this, it would have saved me several years of work! Mike Gordon presumably didn't know about it either: see Emily Riehl and Terrence Tau on The Future of Mathematics . Subscribe to Lambda World . And I just found this 2016 ICFP talk by Dan Licata on Functional programming and Homotopy Type Theory. At 45:54 there is an example of taking this idea of higher inductive types to verify interpreters. Subscribe to ICFP . This was given in 2019. See Cubical Agda: A Dependently Typed Programming Language with Univalence and Higher Inductive Types : The principle of univalence is the major new addition in Homotopy...