CLJS-2977: Spec instrumentation regression with varargs / :static-fns type hints we no longer need

advanced safe variadic invoke for the instrument fn wrapper did not
call conform before invoking the original variadic case. Add tests.

Author: swannodette

src/main/cljs/cljs/spec/test/alpha.cljs

@@ -128,7 +128,12 @@
       (when-some [variadic (.-cljs$core$IFn$_invoke$arity$variadic f)]
         (set! (.-cljs$core$IFn$_invoke$arity$variadic ret)
           (fn [& args]
-            (apply variadic args)))))
+            (if *instrument-enabled*
+              (with-instrument-disabled
+                (conform!* args)
+                (binding [*instrument-enabled* true]
+                  (apply' variadic args)))
+              (apply' variadic args))))))
     ret))
 
 (defn- no-fspec

src/test/cljs/cljs/spec_test.cljs

@@ -441,6 +441,20 @@
   (is (= (s/describe #(odd? %)) ::s/unknown))
   (is (= (s/form #(odd? %)) ::s/unknown)))
 
+(defn defk [key & [doc]]
+  key)
+
+(s/fdef defk
+  :args (s/cat :key keyword?
+               :doc (s/? string?)))
+
+(st/instrument `defk)
+
+(deftest cljs-2977-variadic-fn
+  (is (thrown? js/Error (defk 1 1)))
+  (is (thrown? js/Error (defk :foo 1)))
+  (is (= :foo (defk :foo "bar"))))
+
 (comment
 
   (run-tests)