missing collection protocol method for simple-map-entry

- add ILookup
- add IFind
- add lite-collection-test for these cases
- NOTE: it wasn't clear until we we got to testing that we would need
  all this stuff. Perhaps we just want to use MapEntry, this does
  create a dependence on Vector, but I think simple-map-entry was
  created to avoid the connection to PV before I had done all work to emit
  the simple vector type under :lite-mode

Author: swannodette

src/main/cljs/cljs/core.cljs

@@ -10412,7 +10412,16 @@ reduces them without incurring seq initialization"
     (-nth [_ i]
       (case i, 0 k, 1 v, (throw (js/Error. "Index out of bounds"))))
     (-nth [_ i not-found]
-      (case i, 0 k, 1 v, not-found))))
+      (case i, 0 k, 1 v, not-found))
+    ILookup
+    (-lookup [coll k] (-nth coll k nil))
+    (-lookup [coll k not-found] (-nth coll k not-found))
+    IFind
+    (-find [node x]
+      (case x
+        0 (simple-map-entry 0 k)
+        1 (simple-map-entry 1 v)
+        nil))))
 
 (defn- pr-writer-impl
   [obj writer opts]

src/test/cljs/cljs/lite_collections_test.cljs

@@ -39,9 +39,19 @@
   (let [a (simple-set [(simple-map-entry 1 2)])]
     (is (contains? a (simple-map-entry 1 2)))))
 
+(deftest test-simple-map-entry-lookups
+  (let [me (simple-map-entry :foo "bar")]
+    (is (= :foo (get me 0)))
+    (is (= "bar" (get me 1)))
+    (is (= [0 :foo]
+          (vec (find (simple-map-entry :foo "bar") 0))))
+    (is (= [:foo "b"]
+          (vec (update (simple-map-entry :foo "bar") 1 first))
+          (vec (update-in (simple-map-entry :foo "bar") [1] first))))))
+
 (comment
 
-  (require '[cljs.lite-collections-test])
+  (require '[cljs.lite-collections-test] :reload)
   (cljs.test/run-tests)
 
   )