Bodil shares this seminal work with us, by walking through and implementing a type checker in JavaScript as described in the paper.
Cardelli's 1987 paper "Basic Polymorphic Type Checking" was, according to the author, the first attempt to explain the Hindley-Milner-Damas type system in a way that would be accessible to people who weren't either Hindley, Milner or Damas. It served as my first gentle introduction to the mysteries of type checking, back when I was obsessed with the conceit that the world needed another Lisp with a type system and I was going to have to build it (it would be called BODOL, because obviously).
It was my first significant journey into the mysteries of type checking, to a large extent because it delivers what it promises on the tin: it's an explanation of a method for type checking and inference with parametric polymorphism that's accessible to the average programmer, as opposed to the average logician, and so I'd like to share that journey by walking through and implementing the described type checker with you, but maybe in a language more accessible to modern programmers than the Modula-2 of Cardelli's implementation.
