Fix bug with st/select-spec and s/or

Closes metosin#264

test/cljc/spec_tools/core_test.cljc

@@ -928,3 +928,18 @@
              {:epoch "Epoch converted"
               :nano 20
               :time-basis :UTC})))))
+
+(s/def ::str-264 string?)
+(s/def ::kw-264 keyword?)
+(s/def ::map-264 (s/or :str-map (s/keys :req [::str-264])
+                       :kw-map (s/keys :req [::kw-264])))
+
+(deftest issue-264
+  (doseq [check [{::kw-264 :foo}
+                 {::str-264 "bar"}]]
+
+    (testing "specs are valid before calling st/select-spec"
+      (is (s/valid? ::map-264 check)))
+
+    (testing "specs stay valid after calling st/select-spec"
+      (is (s/valid? ::map-264 (st/select-spec ::map-264 check))))))