CLJS-496: better implementation of char

Stop relying on `goog/isNumber?`, implement `number?` as an inlining
macro in core.clj, use it in core.cljs. Change `char` implementation
so that it uses `String.fromCharCode` if given a number. It simply
returns strings of length 1. On any other type of input it throws an
exception.

src/clj/cljs/core.clj

@@ -15,7 +15,7 @@
                             memfn ns or proxy proxy-super pvalues refer-clojure reify sync time
                             when when-first when-let when-not while with-bindings with-in-str
                             with-loading-context with-local-vars with-open with-out-str with-precision with-redefs
-                            satisfies? identical? true? false? nil? str get
+                            satisfies? identical? true? false? number? nil? str get
 
                             aget aset
                             + - * / < <= > >= == zero? pos? neg? inc dec max min mod
@@ -222,6 +222,9 @@
 (defmacro identical? [a b]
   (bool-expr (list 'js* "(~{} === ~{})" a b)))
 
+(defmacro number? [x]
+  (bool-expr (list 'js* "typeof ~{} === 'number'" x)))
+
 (defmacro aget
   ([a i]
      (list 'js* "(~{}[~{}])" a i))
@@ -239,7 +242,6 @@
   ([x y & more] `(+ (+ ~x ~y) ~@more)))
 
 (defmacro byte [x] x)
-(defmacro char [x] x)
 (defmacro short [x] x)
 (defmacro float [x] x)
 (defmacro double [x] x)

src/cljs/cljs/core.cljs

@@ -1105,7 +1105,7 @@ reduces them without incurring seq initialization"
   (instance? Symbol x))
 
 (defn ^boolean number? [n]
-  (goog/isNumber n))
+  (cljs.core/number? n))
 
 (defn ^boolean fn? [f]
   (or ^boolean (goog/isFunction f) (satisfies? Fn f)))
@@ -1379,7 +1379,15 @@ reduces them without incurring seq initialization"
    (reduce min (cljs.core/min x y) more)))
 
 (defn byte [x] x)
-(defn char [x] x)
+
+(defn char
+  "Coerce to char"
+  [x]
+  (cond
+    (number? x) (.fromCharCode js/String x)
+    (and (string? x) (== (.-length x) 1)) x
+    :else (throw (js/Error. "Argument to char must be a character or number"))))
+
 (defn short [x] x)
 (defn float [x] x)
 (defn double [x] x)

test/cljs/cljs/core_test.cljs

@@ -1857,5 +1857,9 @@
   (def exists?-test-val 'foo)
   (assert (exists? exists?-test-val))
 
+  ;; CLJS-496
+  (assert (= (char 65) \A))
+  (assert (= (char \A) \A))
+
   :ok
   )