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Introducing the core.typed REPL and integrated type checking

So far core.typed has offered offline checking. The check-ns function is exposed so programmers can type check namespaces when they like.

Using nREPL middleware and a little monkey-patching, we can integrate core.typed into the compilation pipeline. This way you can use typed namespaces as you would a normal namespace, except you automatically get type checking from core.typed.

Setup

We assume you are using leiningen.

• Step 1:

Depend on core.typed 0.3.0-x and Clojure 1.7.0-x.

  :dependencies [[org.clojure/clojure "1.7.0-RC1"]
                 [org.clojure/core.typed "0.3.0-alpha5"]])

• Step 2:

Add the following middleware to your project.clj, or equivalent middleware

  :repl-options {:nrepl-middleware [clojure.core.typed.repl/wrap-clj-repl]}

• Step 3:

Add ^:core.typed metadata to the ns form you want type checked.

Usage

Use your favourite Clojure editor/IDE and use the standard REPL and load features.