Experimental Lite Mode

deps.edn

@@ -19,6 +19,8 @@
                                       "-e" "(cljs.test-runner/-main)"]}
   :runtime.test.build    {:extra-paths ["src/test/cljs"]
                           :main-opts ["-m" "cljs.main" "-co" "resources/test.edn" "-c"]}
+  :lite.test.build       {:extra-paths ["src/test/cljs"]
+                          :main-opts ["-m" "cljs.main" "-co" "resources/lite_test.edn" "-c"]}
   :selfhost.test.build   {:extra-paths ["src/test/self"]
                           :main-opts ["-m" "cljs.main" "-co" "resources/self_host_test.edn" "-c"]}
   :selfparity.test.build {:extra-paths ["src/test/self"]

resources/lite_test.edn

@@ -0,0 +1,13 @@
+{:optimizations    :advanced
+ :main             lite-test-runner
+ :lite-mode        true
+ :output-to        "builds/out-lite/lite-test.js"
+ :output-dir       "builds/out-lite"
+ :output-wrapper   true
+ :verbose          true
+ :compiler-stats   true
+ :parallel-build   true
+ :closure-warnings {:non-standard-jsdoc :off :global-this :off}
+ :language-out     :es5
+ :pseudo-names     true
+ :pretty-print     true}

src/main/cljs/cljs/analyzer/passes/lite.cljc

@@ -0,0 +1,32 @@
+;; Copyright (c) Rich Hickey. All rights reserved.
+;; The use and distribution terms for this software are covered by the
+;; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+;; which can be found in the file epl-v10.html at the root of this distribution.
+;; By using this software in any fashion, you are agreeing to be bound by
+;; the terms of this license.
+;; You must not remove this notice, or any other, from this software.
+
+(ns cljs.analyzer.passes.lite
+  (:refer-clojure :exclude [var?]))
+
+(defn var? [ast]
+  (= :var (:op ast)))
+
+(def ctor->simple-ctor
+  '{cljs.core/vector cljs.core/simple-vector
+    cljs.core/vec    cljs.core/simple-vec})
+
+(defn update-var [{:keys [name] :as ast}]
+  (let [replacement (get ctor->simple-ctor name)]
+    (-> ast
+      (assoc :name replacement)
+      (assoc-in [:info :name] replacement))))
+
+(defn replace-var? [ast]
+  (and (var? ast)
+       (contains? ctor->simple-ctor (:name ast))))
+
+(defn use-lite-types
+  [env ast _]
+  (cond-> ast
+    (replace-var? ast) update-var))