clojure -Srepro -Sdeps '{:deps {issue {:git/url "https://gist.github.com/darwin/e7748419304915f75633666b906f23f8" :sha "af929e906525703509a4f86ba371d74f8338dc71"}}}' -m main

deps.edn

{:paths ["."]
 :deps  {metosin/spec-tools     {:mvn/version "0.7.2"}
         org.clojure/test.check {:mvn/version "0.9.0"}
         org.clojure/clojure    {:mvn/version "1.9.0"}}}

main.clj

(ns main
  (:require [spec-tools.core :as st]
            [clojure.spec.alpha :as s]
            [clojure.spec.gen.alpha :as gen]))

(def raw-spec (s/+ (s/tuple #{:a :b :c} integer?)))

(def metosin-spec
  (st/spec {:spec raw-spec}))

(def worked-around-metosin-spec
  (st/spec {:spec raw-spec
            :gen  #(s/gen raw-spec)}))

(defn -main [& args]
  (println "1." (gen/generate (s/gen raw-spec)))
  (try
    (println "2." (gen/generate (s/gen metosin-spec)))
    (catch Exception e
      (println e)))
  (println "3." (gen/generate (s/gen worked-around-metosin-spec))))

output.txt

1. ([:b 109632] [:a 3436022] [:c 19434] [:a -1401] [:c -100] [:a 1978152] [:c 21879] [:a 52823884] [:c 10055] [:a -1271189] [:a 6379119])
#error {
 :cause No implementation of method: :gen* of protocol: #'clojure.spec.alpha/Spec found for class: clojure.lang.PersistentArrayMap
 :via
 [{:type java.lang.IllegalArgumentException
   :message No implementation of method: :gen* of protocol: #'clojure.spec.alpha/Spec found for class: clojure.lang.PersistentArrayMap
   :at [clojure.core$_cache_protocol_fn invokeStatic core_deftype.clj 583]}]
 :trace
 [[clojure.core$_cache_protocol_fn invokeStatic core_deftype.clj 583]
  [clojure.core$_cache_protocol_fn invoke core_deftype.clj 575]
  [clojure.spec.alpha$fn__1715$G__1663__1726 invoke alpha.clj 37]
  [spec_tools.core.Spec gen_STAR_ core.cljc 265]
  [clojure.spec.alpha$gensub invokeStatic alpha.clj 279]
  [clojure.spec.alpha$gensub invoke alpha.clj 272]
  [clojure.spec.alpha$gen invokeStatic alpha.clj 296]
  [clojure.spec.alpha$gen invoke alpha.clj 285]
  [clojure.spec.alpha$gen invokeStatic alpha.clj 295]
  [clojure.spec.alpha$gen invoke alpha.clj 285]
  [main$_main$fn__920 invoke main.clj 18]
  [main$_main invokeStatic main.clj 17]
  [main$_main doInvoke main.clj 15]
  [clojure.lang.RestFn invoke RestFn.java 397]
  [clojure.lang.AFn applyToHelper AFn.java 152]
  [clojure.lang.RestFn applyTo RestFn.java 132]
  [clojure.lang.Var applyTo Var.java 702]
  [clojure.core$apply invokeStatic core.clj 657]
  [clojure.main$main_opt invokeStatic main.clj 317]
  [clojure.main$main_opt invoke main.clj 313]
  [clojure.main$main invokeStatic main.clj 424]
  [clojure.main$main doInvoke main.clj 387]
  [clojure.lang.RestFn applyTo RestFn.java 137]
  [clojure.lang.Var applyTo Var.java 702]
  [clojure.main main main.java 37]]}
3. ([:a 27631896] [:b -1] [:a -16745599] [:a -1] [:a 68070] [:a 0] [:a 230523] [:b -1] [:a 390] [:b 213302589] [:c -3309] [:a -27] [:a -159041781] [:c 829904] [:b -1507] [:b 21] [:b 12063284] [:c -2813] [:a 712393] [:a 87379] [:b -47827052])