CLJS-3085: Types are inferred for dynamic vars

Infers dynamic vars as 'any, unless def has a type hint

Author: roman01la

src/main/clojure/cljs/analyzer.cljc

@@ -1879,9 +1879,11 @@
                         (disallowing-ns*
                           (analyze (assoc env :context :expr) (:init args) sym))))
           fn-var? (and (some? init-expr) (= (:op init-expr) :fn))
-          tag (if fn-var?
-                (or (:ret-tag init-expr) tag (:inferred-ret-tag init-expr))
-                (or tag (:tag init-expr)))
+          tag (cond
+                fn-var? (or (:ret-tag init-expr) tag (:inferred-ret-tag init-expr))
+                tag tag
+                dynamic ANY_SYM
+                :else (:tag init-expr))
           export-as (when-let [export-val (-> sym meta :export)]
                       (if (= true export-val) var-name export-val))
           doc (or (:doc args) (-> sym meta :doc))]

src/test/cljs/cljs/binding_test.cljs

@@ -35,3 +35,22 @@
   (is (= 2 (with-redefs [a 10
                          b (inc a)]
              b))))
+
+(def ^:dynamic *foo* false)
+(def ^:dynamic ^boolean *foo-tagged* false)
+
+(defn bar [] (if *foo* 1 2))
+(defn bar-tagged [] (if *foo-tagged* 1 2))
+
+(deftest test-tag-inference
+  (is (= 2 (bar)))
+  (binding [*foo* "abc"]
+    (is (= 1 (bar))))
+  (binding [*foo* ""]
+    (is (= 1 (bar))))
+
+  (is (= 2 (bar-tagged)))
+  (binding [*foo-tagged* "abc"]
+    (is (= 1 (bar-tagged))))
+  (binding [*foo-tagged* ""]
+    (is (= 2 (bar-tagged)))))