CLJS-3461: don't hard-code destructuring to PAM

- use empty map literal instead, use the constructor for createAsIfByAssoc
- perf is not critical for `:lite-mode` opt for simplicity for now
- add REPL aliases to deps.edn to make it easier to play around :lite-mode

Author: swannodette

deps.edn

@@ -9,7 +9,11 @@
   org.clojure/tools.reader {:mvn/version "1.3.6"}
   org.clojure/test.check {:mvn/version "1.1.1"}}
  :aliases
- {:cli.test.run          {:extra-paths ["src/test/cljs_cli"]
+ {:cljs-repl             {:extra-paths ["src/test/cljs"]
+                          :main-opts ["-m" "cljs.main" "-re" "node" "-d" ".cljs_repl" "-r"]}
+  :cljs-lite-repl        {:extra-paths ["src/test/cljs"]
+                          :main-opts ["-m" "cljs.main" "-co" "{:lite-mode true}" "-re" "node" "-d" ".cljs_lite_repl" "-r"]}
+  :cli.test.run          {:extra-paths ["src/test/cljs_cli"]
                           :main-opts ["-i" "src/test/cljs_cli/cljs_cli/test_runner.clj"
                                       "-e" "(cljs-cli.test-runner/-main)"]}
   :compiler.test         {:extra-paths ["src/test/cljs" "src/test/cljs_build" "src/test/cljs_cp"

src/main/cljs/cljs/core.cljs

@@ -4129,10 +4129,10 @@ reduces them without incurring seq initialization"
 (defn --destructure-map [gmap]
   (if (implements? ISeq gmap)
     (if (next gmap)
-      (.createAsIfByAssoc PersistentArrayMap (to-array gmap))
+      (.createAsIfByAssoc (. {} -constructor) (to-array gmap))
       (if (seq gmap)
         (first gmap)
-        (.-EMPTY PersistentArrayMap)))
+        {}))
     gmap))
 
 (defn vary-meta
@@ -7126,7 +7126,7 @@ reduces them without incurring seq initialization"
   (fn [init]
     ;; check trailing element
     (let [len           (alength init)
-          has-trailing? (== 1 (bit-and len  1))]
+          has-trailing? (== 1 (bit-and len 1))]
       (if-not (or has-trailing? (pam-dupes? init))
         (PersistentArrayMap. nil (/ len 2) init nil)
         (.createAsIfByAssocComplexPath PersistentArrayMap init has-trailing?)))))
@@ -9040,8 +9040,8 @@ reduces them without incurring seq initialization"
   https://clojure.org/reference/special_forms#keyword-arguments"
   [s]
   (if (next s)
-    (.createAsIfByAssoc PersistentArrayMap (to-array s))
-    (if (seq s) (first s) (.-EMPTY PersistentArrayMap))))
+    (.createAsIfByAssoc (. {} -constructor) (to-array s))
+    (if (seq s) (first s) {})))
 
 (defn sorted-map
   "keyval => key val
@@ -12731,6 +12731,21 @@ reduces them without incurring seq initialization"
           (recur (nnext kvs)))
         (.fromObject ObjMap ks obj)))))
 
+(set! (.-createAsIfByAssoc ObjMap)
+  (fn [init]
+    ;; check trailing element
+    (let [len           (alength init)
+          has-trailing? (== 1 (bit-and len 1))
+          init          (if has-trailing?
+                          (pam-grow-seed-array init
+                            (into {} (aget init (dec len))))
+                          init)
+          len           (alength init)]
+      (loop [i 0 ret {}]
+        (if (< i len)
+          (recur (+ i 2) (assoc ret (aget init i) (aget init (inc i))))
+          ret)))))
+
 (defn- scan-array-equiv [incr k array]
   (let [len (alength array)]
     (loop [i 0]