在使用 spec2 进行实验时，我发现以下行为像是一个错误。
(s/def ::s1 (s/schema {:a string?}))
=> :dev.fp.livingdocs.specs/s1
(s/def ::s2 (s/schema {:b string?}))
=> :dev.fp.livingdocs.specs/s2
(s/def ::s3 (s/schema {:c string?}))
=> :dev.fp.livingdocs.specs/s3
;; The following is unexpected (neseted unions)
(s/def ::u (s/union ::s1 (s/union ::s2 ::s3)))
Execution error (IllegalArgumentException) at clojure.alpha.spec.protocols/eval1665$fn$G (protocols.clj:20).
No implementation of method: :keyspecs* of protocol: #'clojure.alpha.spec.protocols/Schema found for class: clojure.lang.PersistentList
(s/def ::u (s/union (s/union ::s1 ::s2) ::s3))
Execution error (IllegalArgumentException) at clojure.alpha.spec.protocols/eval1665$fn$G (protocols.clj:20).
No implementation of method: :keyspecs* of protocol: #'clojure.alpha.spec.protocols/Schema found for class: clojure.lang.PersistentList
;; if I try to pull out the nested union into a separate keyword, it starts working
(s/def ::u' (s/union ::s1 ::s2))
=> :dev.fp.livingdocs.specs/u'
(s/def ::u (s/union ::u' ::s3))
=> :dev.fp.livingdocs.specs/u
(s/explain (s/select ::u [:a :c]) {:a "bdfd"})
{:a "bdfd"} - failed: (fn [m] (contains? m :c))
;; but also this
(s/form ::ld/typed)
=>
(clojure.alpha.spec/schema
[{:name clojure.core/string?, :type clojure.core/string?}])
(s/form ::ldd/editable)
=>
(clojure.alpha.spec/schema
[{:optional clojure.core/boolean?,
:maxLength clojure.core/integer?,
:plainText clojure.core/boolean?,
:excluexcludeFromTextCount clojure.core/boolean?}])
(s/def ::service
(s/or :single (s/select (s/union ::ld/typed ::ldd/editable) [:type :name :optional])
:multiple (s/select (s/union :ld/typed ::ldd/editable) [:type :name :maxLength])))
Execution error (IllegalArgumentException) at clojure.alpha.spec.protocols/eval1665$fn$G (protocols.clj:20).
No implementation of method: :keyspecs* of protocol: #'clojure.alpha.spec.protocols/Schema found for class: clojure.lang.PersistentList
在这两种情况下，s/union都出现在传给 spec 宏的形式中的嵌套位置。
