What's the idiomatic way of using untyped collections/data structures in typed code?

[NoahStoryM]

Hi!

The data-lib library contains many mutable data structures, which necessitate distinguishing between read types and write types. While current Typed Racket doesn't provide a built-in way to define such types, we can achieve this through some clever techniques.

You can refer to how I defined typed-data-queue and typed-racket-mutable-treelist to implement a similar approach for typed-data-heap:

A new way to type mutable data structures with opposite variance in typed racket

Hi everyone, I have been experimenting with a way to define types with opposite variance in typed racket (see also Is it possible to make Mutable Types support subtype? · racket/typed-racket · Discussion #1129 · GitHub). The idea is to use a struct with two type arguments, one for the input type and one for the output type, and then use a Parameter type to constrain them. For example, here is how I defined a type for queue, a mutable data structure from data/queue: #lang typed/racket/base (re…