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Comment by lelf | Hacker News Reader

Well, there is no such simple interoperability with java from haskell, that's for sure. But otherwise…

  user> (:key nil)
  nil

Mmmm, I'm not certain I particularly want this

  user> (nil :key)
  CompilerException java.lang.IllegalArgumentException: Can't call nil

RUN!

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As many are saying it's a pragmatic choice. And it allows you to do stuff like this:

  (:foo (:bar {}))

Without throwing a NPE. Which is what I want 99.9% of the time. As someone who codes in Clojure close to 10 hours a day, I rarely see a problem like you describe.

If you use clojure.typed, I think the second example would give you a compile-time type error.

While true, the second example already gives you a compile-time error in normal Clojure (note the CompilerException). It never compiled and was never evaluated. This on the other hand compiles and is likely what the OP wanted to show:

  user> (let [e nil] (e :key))

  NullPointerException

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