clojureclojure-protocol

Does the Clojure compiler check if records and types implement protocols?

Is the Clojure compiler meant to check if a record or type that says it instantiates a protocol actually implements the methods listed in it?

I'm trying this out now and so far, it doesn't seem to.

Solution

  • A record can implement a protocol without implementing any of its methods: 

    (defprotocol Structure
  (weight [this])
  (balanced? [this]))

(defrecord Mobile []
  Structure
  )

    ... is accepted.

    If you try to use a non-existent method:

    (balanced? (Mobile.))

;java.lang.AbstractMethodError: user.Mobile.balanced_QMARK_()Ljava/lang/Object;

    As usual, type errors are found at run time.