CLJS-620: Warnings are generated when using a macro in argument position

If the analyzer is about to emit a "use of undeclared Var" warning,
first check to see if there is a macro present with the same name, and,
in that case, change the emitted diagnostic to instead display
a "can't take value of macro" warning.

Author: mfikes

src/main/clojure/cljs/analyzer.cljc

@@ -220,7 +220,10 @@
 
 (defmethod error-message :undeclared-var
   [warning-type info]
-  (str "Use of undeclared Var " (:prefix info) "/" (:suffix info)))
+  (str (if (:macro-present? info)
+         "Can't take value of macro "
+         "Use of undeclared Var ")
+    (:prefix info) "/" (:suffix info)))
 
 (defmethod error-message :undeclared-ns
   [warning-type {:keys [ns-sym js-provide] :as info}]
@@ -599,9 +602,14 @@
   [env prefix suffix]
   (contains? implicit-nses prefix))
 
+(declare get-expander)
+
 (defn confirm-var-exist-warning [env prefix suffix]
   (fn [env prefix suffix]
-    (warning :undeclared-var env {:prefix prefix :suffix suffix})))
+    (warning :undeclared-var env
+      {:prefix         prefix
+       :suffix         suffix
+       :macro-present? (not (nil? (get-expander (symbol (str prefix) (str suffix)) env)))})))
 
 (defn loaded-js-ns?
   "Check if a JavaScript namespace has been loaded. JavaScript vars are
@@ -663,8 +671,6 @@
              #?(:clj (nil? (util/ns->source ns-sym))))
     (warning :undeclared-ns env {:ns-sym ns-sym})))
 
-(declare get-expander)
-
 (defn core-name?
   "Is sym visible from core in the current compilation namespace?"
   #?(:cljs {:tag boolean})