Interesting error using clj-kondo v2019.05.06-alpha: /Users/marc/dev/circleci/circle/src/circle/web/http/routes/outer.clj:0:0: error: can't parse /Users/marc/dev/circleci/circle/src/circle/web/http/routes/outer.clj, No implementation of method: :sexpr of protocol: #'rewrite-clj.node.protocols/Node found for class: nil

These files have clojure dating from 2012-11-07 😄

Found it:

$ echo '(fn)' | clj-kondo --lint -
<stdin>:0:0: error: can't parse <stdin>, No implementation of method: :sexpr of protocol: #'rewrite-clj.node.protocols/Node found for class: nil
linting took 3ms, errors: 1, warnings: 0

And here is a similar one:

$ echo '(doseq [send [inc]] (send 1))' | clj-kondo --lint -
<stdin>:1:21: error: wrong number of args (1) passed to clojure.core/send