Issue with lein 2.9.0

[djptek]

Got this error:

clojure.lang.Compiler$CompilerException: Syntax error macroexpanding clojure.core/fn at (clojure/core/unify.clj:83:18).
#:clojure.error{:phase :macro-syntax-check, :line 83, :column 18, :source "clojure/core/unify.clj", :symbol clojure.core/fn}

workaround (not really fix) was downgrade lein

lein upgrade 2.8.3

prompted by stackoverflow