Disassociate fn arity choice from order of defined arities inline wit…

…h clojure.

src/sci/impl/fns.cljc

@@ -222,12 +222,13 @@
       f)))
 
 (defn lookup-by-arity [arities arity]
-  (some (fn [f]
-          (let [{:sci.impl/keys [fixed-arity min-var-args-arity]} (meta f)]
-            (when (or (= arity fixed-arity )
-                      (and min-var-args-arity
-                           (>= arity min-var-args-arity)))
-              f))) arities))
+  (let [arities-with-variadic-last (sort-by (comp :sci.impl/min-var-args-arity meta) arities)]
+    (some (fn [f]
+            (let [{:sci.impl/keys [fixed-arity min-var-args-arity]} (meta f)]
+              (when (or (= arity fixed-arity)
+                        (and min-var-args-arity
+                             (>= arity min-var-args-arity)))
+                f))) arities-with-variadic-last)))
 
 (defn eval-fn [ctx interpret {:sci.impl/keys [fn-bodies fn-name
                                               var] :as f}]

test/sci/core_test.cljc

@@ -189,6 +189,8 @@
   (is (= 2 (eval* '((fn foo [x & [y]] y) 1 2 3))))
   (is (= 1 (eval* '((fn ([x] x) ([x y] y)) 1))))
   (is (= 2 (eval* '((fn ([x] x) ([x y] y)) 1 2))))
+  (is (= "otherwise" (eval* '((fn ([x & xs] "variadic") ([x] "otherwise")) 1))))
+  (is (= "otherwise" (eval* '((fn ([x] "otherwise") ([x & xs] "variadic")) 1))))
   (is (= '(2 3 4) (eval* '(apply (fn [x & xs] xs) 1 2 [3 4]))))
   (is (thrown-with-msg? #?(:clj Exception :cljs js/Error)
                         #"Can't have fixed arity function with more params than variadic function"