Workaround for AOT protocol bug with getStackTrace

When creating an uberjar, the code gets AOT compiled. When type
hinting the .getStackTrace call, it returns an array. That array
caused us to hit https://dev.clojure.org/jira/browse/CLJ-1790. This
commit works around that until we upgrade to Clojure 1.9.

src/metabase/util.clj

@@ -575,16 +575,26 @@
   (filtered-stacktrace [this]
     "Get the stack trace associated with E and return it as a vector with non-metabase frames filtered out."))
 
+;; These next two functions are a workaround for this bug https://dev.clojure.org/jira/browse/CLJ-1790
+;; When Throwable/Thread are type-hinted, they return an array of type StackTraceElement, this causes
+;; a VerifyError. Adding a layer of indirection here avoids the problem. Once we upgrade to Clojure 1.9
+;; we should be able to remove this code.
+(defn- throwable-get-stack-trace [^Throwable t]
+  (.getStackTrace t))
+
+(defn- thread-get-stack-trace [^Thread t]
+  (.getStackTrace t))
+
 (extend nil
   IFilteredStacktrace {:filtered-stacktrace (constantly nil)})
 
 (extend Throwable
-  IFilteredStacktrace {:filtered-stacktrace (fn [^Throwable this]
-                                              (filtered-stacktrace (.getStackTrace this)))})
+  IFilteredStacktrace {:filtered-stacktrace (fn [this]
+                                             (filtered-stacktrace (throwable-get-stack-trace this)))})
 
 (extend Thread
-  IFilteredStacktrace {:filtered-stacktrace (fn [^Thread this]
-                                              (filtered-stacktrace (.getStackTrace this)))})
+  IFilteredStacktrace {:filtered-stacktrace (fn [this]
+                                              (filtered-stacktrace (thread-get-stack-trace this)))})
 
 ;; StackTraceElement[] is what the `.getStackTrace` method for Thread and Throwable returns
 (extend (Class/forName "[Ljava.lang.StackTraceElement;")