CLJS-3134: Thread predicate-induced inference through and

Author: mfikes

src/main/clojure/cljs/analyzer.cljc

@@ -3483,13 +3483,23 @@
             (contains? t 'js)
             (some array-types t))))))
 
+(defn- analyze-js-star-args [js-op env args]
+  (first (reduce
+           (fn [[argexprs env] arg]
+             [(conj argexprs (analyze env arg))
+              (if (= js-op 'cljs.core/and)
+                (set-test-induced-tags env arg)
+                env)])
+           [[] env]
+           args)))
+
 (defn analyze-js-star* [env jsform args form]
   (let [enve      (assoc env :context :expr)
-        argexprs  (vec (map #(analyze enve %) args))
         form-meta (meta form)
         segs      (js-star-seg jsform)
         tag       (get-js-tag form)
         js-op     (:js-op form-meta)
+        argexprs  (analyze-js-star-args js-op enve args)
         numeric   (:numeric form-meta)
         validate  (fn [warning-type valid-types?]
                     (let [types (map #(infer-tag env %) argexprs)]

src/main/clojure/cljs/core.cljc

@@ -874,13 +874,19 @@
   ([x] x)
   ([x & next]
    (core/let [forms (concat [x] next)]
-     (if (every? #(simple-test-expr? &env %)
-           (map #(cljs.analyzer/no-warn (cljs.analyzer/analyze &env %)) forms))
+     (core/cond
+       (every? #(simple-test-expr? &env %)
+         (map #(cljs.analyzer/no-warn (cljs.analyzer/analyze &env %)) forms))
        (core/let [and-str (core/->> (repeat (count forms) "(~{})")
                             (interpose " && ")
                             (#(concat ["("] % [")"]))
                             (apply core/str))]
          (bool-expr `(~'js* ~and-str ~@forms)))
+
+       (typed-expr? &env x '#{boolean})
+       `(if ~x (and ~@next) false)
+
+       :else
        `(let [and# ~x]
           (if and# (and ~@next) and#))))))