Speaking speculatively, improving type inference is a great place for collaboration. Concretely, I've extended several minor ideas. Typed Clojure uses occurre

Speaking speculatively, improving type inference is a great place for collaboration. Concretely, I've extended several minor ideas. Typed Clojure uses occurrence typing in sequential forms, as well as conditionals: http://frenchy64.github.io/2013/09/08/simple-reasoning-assertions-core-typed.html http://frenchy64.github.io/2013/09/08/simple-reasoning-asser... We can type check (filter identity coll) a little more accurately (which is actually quite hard to do): https://github.com/clojure/core.typed/blob/master/src/main/clojure/clojure/core/typed/base_env.clj#L729 https://github.com/clojure/core.typed/blob/master/src/main/c... The type system's interaction with Java's type system is interesting, which is something I've fleshed out. I have heterogeneous maps as well as heterogeneous vectors, and support complex operations like merge. Unsure if relevant to Racket. There are lots of other ideas which I need to implement to type check Clojure, but aren't necessarily crucial to type checking Racket, but would be nice to have.